1
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Ying M, Wang K, Yan W, Pu M, Lin L. Stable Axially Chiral Cyclohexylidenes from Catalytic Asymmetric Knoevenagel Condensation. Chemistry 2024; 30:e202401243. [PMID: 38711202 DOI: 10.1002/chem.202401243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/03/2024] [Accepted: 05/06/2024] [Indexed: 05/08/2024]
Abstract
Axially chiral cycloalkylidenes are interesting but less developed axially chiral molecules. Here, a bispidine-based chiral amine catalytic system was developed to promote efficiently the asymmetric Knoevenagel condensation of N-protected oxindoles and benzofuranones with 4-substituted cyclohexanones. A variety of alkylidenecycloalkanes with stable axial chirality were obtained in good yields and fairly good er (enantiomeric ratio). Based on the absolute configuration determination of product and DFT calculations, a possible mechanism of stereoselective induction was proposed.
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Affiliation(s)
- Meijia Ying
- Key Laboratory of Green Chemistry & Technology Ministry of Education, College of Chemistry, Sichuan University, P. R. China
| | - Kaixuan Wang
- Key Laboratory of Green Chemistry & Technology Ministry of Education, College of Chemistry, Sichuan University, P. R. China
| | - Wenjun Yan
- Key Laboratory of Green Chemistry & Technology Ministry of Education, College of Chemistry, Sichuan University, P. R. China
| | - Maoping Pu
- Key Laboratory of Green Chemistry & Technology Ministry of Education, College of Chemistry, Sichuan University, P. R. China
| | - Lili Lin
- Key Laboratory of Green Chemistry & Technology Ministry of Education, College of Chemistry, Sichuan University, P. R. China
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2
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Viesser RV, Donald CP, May JA, Wu JI. Can Twisted Double Bonds Facilitate Stepwise [2 + 2] Cycloadditions? Org Lett 2024; 26:3778-3783. [PMID: 38684005 DOI: 10.1021/acs.orglett.4c00879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Computational studies for a series of low to high strain anti-Bredt alkenes suggest that those with highly twisted bridgehead double bonds and a small singlet-triplet energy gap may undergo facile stepwise [2 + 2] cycloadditions to furnish four membered rings. A selection of reaction substrates, including ethylene, acetylene, perfluoroethylene, and cyclooctyne are considered.
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Affiliation(s)
- Renan V Viesser
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Clayton P Donald
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Jeremy A May
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Judy I Wu
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
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3
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Guo W, Hori M, Ogura Y, Nishimura K, Oki K, Ikai T, Yashima E, Ishihara K. Tandem Isomerization/α,β-Site-Selective and Enantioselective Addition Reactions of N-(3-Butynoyl)-3,5-dimethylpyrazole Induced by Chiral π-Cu(II) Catalysts. J Am Chem Soc 2023; 145:27080-27088. [PMID: 38032102 PMCID: PMC10722507 DOI: 10.1021/jacs.3c10820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 11/07/2023] [Accepted: 11/08/2023] [Indexed: 12/01/2023]
Abstract
Allenes are important building blocks, and derivatization of products via cycloadditions of allenes could become a powerful strategy for constructing carbocyclic and heterocyclic rings. However, the development of catalytic site-selective and enantioselective cycloaddition reactions of allenes still presents significant challenges. Here, we report chiral π-Cu(II)-complex-catalyzed isomerization of N-(3-butynoyl)-3,5-dimethyl-1H-pyrazole to generate N-allenoylpyrazole in situ and subsequent α,β-site-selective and enantioselective [3 + 2], [4 + 2], or [2 + 2] cycloaddition or conjugate addition reactions. The asymmetric environment created by the intramolecular π-Cu(II) interactions provides the corresponding adducts in moderate to high yield with excellent enantioselectivity. To the best of our knowledge, this is the first successful method for chiral-Lewis-acid-catalyzed tandem isomerization/α,β-site-selective and enantioselective cycloaddition or conjugate addition reactions of latent non-γ-substituted allenoyl derivative.
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Affiliation(s)
- Weiwei Guo
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Masahiro Hori
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Yoshihiro Ogura
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Kazuki Nishimura
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Kosuke Oki
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Tomoyuki Ikai
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Eiji Yashima
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Kazuaki Ishihara
- Graduate
School of Engineering, Nagoya University, B2-3(611) Furo-cho, Chikusa, Nagoya 464-8603, Japan
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4
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Tang L, Huang QN, Wu F, Xiao Y, Zhou JL, Xu TT, Wu WB, Qu S, Feng JJ. C(sp 2)-H cyclobutylation of hydroxyarenes enabled by silver-π-acid catalysis: diastereocontrolled synthesis of 1,3-difunctionalized cyclobutanes. Chem Sci 2023; 14:9696-9703. [PMID: 37736637 PMCID: PMC10510764 DOI: 10.1039/d3sc03258b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/22/2023] [Indexed: 09/23/2023] Open
Abstract
Ring-opening of bicyclo[1.1.0]butanes (BCBs) is emerging as a powerful strategy for 1,3-difunctionalized cyclobutane synthesis. However, reported radical strain-release reactions are typically plagued with diastereoselectivity issues. Herein, an atom-economic protocol for the highly chemo- and diastereoselective polar strain-release ring-opening of BCBs with hydroxyarenes catalyzed by a π-acid catalyst AgBF4 has been developed. The use of readily available starting materials, low catalyst loading, high selectivity (up to >98 : 2 d.r.), a broad substrate scope, ease of scale-up, and versatile functionalizations of the cyclobutane products make this approach very attractive for the synthesis of 1,1,3-trisubstituted cyclobutanes. Moreover, control experiments and theoretical calculations were performed to illustrate the reaction mechanism and selectivity.
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Affiliation(s)
- Lei Tang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Qi-Nan Huang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Feng Wu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Yuanjiu Xiao
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Jin-Lan Zhou
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Tong-Tong Xu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Wen-Biao Wu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Shuanglin Qu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
| | - Jian-Jun Feng
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Advanced Catalytic Engineering Research Center of the Ministry of Education, College of Chemistry and Chemical Engineering, Hunan University Changsha Hunan 410082 P. R. China
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5
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Guo R, Brown MK. Lewis Acid-Promoted [2 + 2] Cycloadditions of Allenes and Ketenes: Versatile Methods for Natural Product Synthesis. Acc Chem Res 2023; 56:2253-2264. [PMID: 37540783 PMCID: PMC11041672 DOI: 10.1021/acs.accounts.3c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
ConspectusCycloaddition reactions are an effective method to quickly build molecular complexity. As predicted by the Woodward-Hoffmann rules, concerted cycloadditions with alkenes allow for the constructions of all possible stereoisomers of product by use of either the Z or E geometry. While this feature of cycloadditions is widely used in, for example, [4 + 2] cycloadditions, translation to [2 + 2] cycloadditions is challenging because of the often stepwise and therefore stereoconvergent nature of these processes. Over the past decade, our lab has explored Lewis acid-promoted [2 + 2] cycloadditions of electron-deficient allenes or ketenes with alkenes. The concerted, asynchronous cycloadditions allow for the synthesis of various cyclobutanes with control of stereochemistry.Our lab developed the first examples of Lewis acid-promoted ketene-alkene [2 + 2] cycloadditions. Compared with traditional thermal conditions, Lewis acid-promoted conditions have several advantages, such as increased reactivity, increased yield, improved diastereoselectivity, and, for certain cases, inverse diastereoselectivity. Detailed mechanistic studies revealed that the diastereoselectivity was controlled by the size of the substituent and the barrier of a deconjugation event. However, these reactions required the use of stoichiometric amounts of EtAlCl2 because of the product inhibition, which led us to investigate catalytic enantioselective [2 + 2] cycloadditions of allenoates with alkenes. Through the use of chiral oxazaborolidines, a broad range of cyclobutanes can be prepared with the control of enantioselectivity. Mechanistic experiments, including 2D-labled alkenes and Hammett analysis, illuminate likely transition state models for the cycloadditions. Additional studies led to the development of Lewis acid-catalyzed intramolecular stereoselective [2 + 2] cycloadditions of chiral allenic ketones/esters with alkenes.The methods we developed have been instrumental in the synthesis of several families of natural products. Specifically, one key lactone motif in (±)-gracilioether F was constructed by a ketene-alkene [2 + 2] cycloaddition and subsequent regioselective Baeyer-Villiger oxidation sequence. Enantioselective allenoate-alkene [2 + 2] cycloadditions allowed for the synthesis of (-)-hebelophyllene E. Another attempt of applying this method in the synthesis of (+)-[5]-ladderanoic acid failed to deliver the desired cyclobutane because of an unexpected rearrangement. The key cyclobutane was later assembled by a stepwise carboboration/Zweifel olefination process. Finally, the stereoselective [2 + 2] cycloadditions of allenic ketones and alkenes was applied in the syntheses of (-)-[3]-ladderanol, (+)-hippolide J, and (-)-cajanusine.
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Affiliation(s)
- Renyu Guo
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave, Bloomington, Indiana 47405, United States
| | - M Kevin Brown
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave, Bloomington, Indiana 47405, United States
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6
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Fan Z, Strassfeld DA, Park HS, Wu K, Yu JQ. Formal γ-C-H Functionalization of Cyclobutyl Ketones: Synthesis of cis-1,3-Difunctionalized Cyclobutanes. Angew Chem Int Ed Engl 2023; 62:e202303948. [PMID: 37051944 PMCID: PMC10330309 DOI: 10.1002/anie.202303948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/10/2023] [Accepted: 04/11/2023] [Indexed: 04/14/2023]
Abstract
1,3-Difunctionalized cyclobutanes are an emerging scaffold in medicinal chemistry that can confer beneficial pharmacological properties to small-molecule drug candidates. However, the diastereocontrolled synthesis of these compounds typically requires complicated synthetic routes, indicating a need for novel methods. Here, we report a sequential C-H/C-C functionalization strategy for the stereospecific synthesis of cis-γ-functionalized cyclobutyl ketones from readily available cyclobutyl aryl ketones. Specifically, a bicyclo[1.1.1]pentan-2-ol intermediate is generated from the parent cyclobutyl ketone via an optimized Norrish-Yang procedure. This intermediate then undergoes a ligand-enabled, palladium-catalyzed C-C cleavage/functionalization to produce valuable cis-γ-(hetero)arylated, alkenylated, and alkynylated cyclobutyl aryl ketones, the benzoyl moiety of which can subsequently be converted to a wide range of functional groups including amides and esters.
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Affiliation(s)
- Zhoulong Fan
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Daniel A Strassfeld
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Han Seul Park
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Kevin Wu
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jin-Quan Yu
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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7
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Liang Z, Wang L, Wang Y, Wang L, Chong Q, Meng F. Cobalt-Catalyzed Diastereo- and Enantioselective Carbon-Carbon Bond Forming Reactions of Cyclobutenes. J Am Chem Soc 2023; 145:3588-3598. [PMID: 36734874 DOI: 10.1021/jacs.2c12475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Catalytic enantioselective functionalization of cyclobutenes constitutes a general and modular strategy for construction of enantioenriched complex cyclobutanes bearing multiple stereogenic centers, as chiral four-membered rings are common motifs in biologically active molecules and versatile intermediates in organic synthesis. However, enantioselective synthesis of cyclobutanes through such a strategy remained significantly limited. Herein, we report a series of unprecedented cobalt-catalyzed carbon-carbon bond forming reactions of cyclobutenes that are initiated through enantioselective carbometalation. The protocols feature diastereo- and enantioselective introduction of allyl, alkynyl, and functionalized alkyl groups. Mechanistic studies indicated an unusual 1,3-cobalt migration and subsequent β-carbon elimination cascade process occurred in the allyl addition. These new discoveries established a new elementary process for cobalt catalysis and an extension of diversity of nucleophiles for enantioselective transformations of cyclobutenes.
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Affiliation(s)
- Zhikun Liang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032
| | - Lei Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032
| | - Yu Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032
| | - Lifan Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032
| | - Qinglei Chong
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032
| | - Fanke Meng
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, China, 200032.,School of Chemistry and Material Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China, 310024
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8
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Wang L, Gao F, Zhang X, Peng T, Xu Y, Wang R, Yang D. Concerted Enantioselective [2+2] Cycloaddition Reaction of Imines Mediated by a Magnesium Catalyst. J Am Chem Soc 2023; 145:610-625. [PMID: 36538490 DOI: 10.1021/jacs.2c11284] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Enantioselective [2 + 2] cyclization between an imine and a carbon-carbon double bond is a versatile strategy to build chiral azetidines. However, α-branched allenoates have never been successfully applied in [2 + 2] cyclization reactions with imines, as they always undergo Kwon's [4 + 2] annulation in previous catalytic methods. Herein, a simple in situ generated magnesium catalyst was employed to successfully achieve the enantioselective [2 + 2] cyclization reaction of DPP-imines and α-branched allenoates for the first time. Insightful experiments including KIE experiments, controlled experiments, Hammett plot analysis, and 31P NMR studies of initial intermediates indicate that the current [2 + 2] cyclization of imine most likely involves an asynchronous concerted transition state. Further mechanistic investigations by combining kinetic studies, ESI experiments, 31P NMR studies of coordination complexes, and controlled experiments on reaction rates under different catalyst loading amounts provided the coordination details for this [2 + 2] cyclization reaction between DPP-imines and α-branched allenoates. This new approach was applied to the synthesis of various chiral aza-heterocycles, including the enantioselective synthesis of the key intermediate of a lipid-lowering agent Ezetimibe.
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Affiliation(s)
- Linqing Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
| | - Feiyun Gao
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
| | - Xiaoyong Zhang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518055, P. R. China
| | - Tianyu Peng
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
| | - Yingfan Xu
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
| | - Rui Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
| | - Dongxu Yang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, P. R. China.,Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou 730000, P. R. China
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9
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Zhou M, Mathew S, de Bruin B. Thermal and (Thermo-Reversible) Photochemical Cycloisomerization of 1 H-2-Benzo[ c]oxocins: From Synthetic Applications to the Development of a New T-Type Molecular Photoswitch. J Am Chem Soc 2022; 145:645-657. [PMID: 36548378 PMCID: PMC9837851 DOI: 10.1021/jacs.2c11310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A novel T-type molecular photoswitch based on the reversible cyclization of 1H-2-benzo[c]oxocins to dihydro-4H-cyclobuta[c]isochromenes has been developed. The switching mechanism involves a light-triggered ring-contraction of 8-membered 1H-2-benzo[c]oxocins to 4,6-fused O-heterocyclic dihydro-4H-cyclobuta[c]isochromene ring systems, with reversion back to the 1H-2-benzo[c]oxocin state accessible through heating. Both processes are unidirectional and proceed with good efficiency, with switching properties─including reversibility and half-life time─easily adjusted via structural functionalization. Our new molecular-switching platform exhibits independence from solvent polarity, originating from its neutral-charge switching mechanism, a property highly sought-after for biological applications. The photoinduced ring-contraction involves a [2+2] conjugated-diene cyclization that obeys the Woodward-Hoffmann rules. In contrast, the reverse process initiates via a thermal ring-opening (T > 60 °C) to produce the original 8-membered 1H-2-benzo[c]oxocins, which is thermally forbidden according to the Woodward-Hoffmann rules. The thermal ring-opening is likely to proceed via an ortho-quinodimethane (o-QDM) intermediate, and the corresponding switching mechanisms are supported by experimental observations and density functional theory calculations. Other transformations of 1H-2-benzo[c]oxocins were found upon altering reaction conditions: prolonged heating of the 1H-2-benzo[c]oxocins at a significantly elevated temperature (72 h at 120 °C), with the resulting dihydronaphthalenes formed via the o-QDM intermediate. These reactions also proceed with good chemoselectivities, providing new synthetic protocols for motifs found in several bioactive molecules, but are otherwise difficult to access.
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10
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Shankar M, Kalyani A, Anitha M, Siva Reddy A, Swamy KCK. Divergent Reactivity of Phosphorylated and Related Allenes: [4 + 2] Cycloaddition with 3,6-Diphenyltetrazine, Self-Addition Leading to Dimers and [Pd]-Complex Formation. J Org Chem 2022; 87:13683-13697. [PMID: 36197101 DOI: 10.1021/acs.joc.2c01337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phosphorus-based naphthalenes are formed by self-dimerization-cum-cyclization of α-aryl allenylphosphonates or allenylphosphine oxides using catalytic Pd(OAc)2in the presence of PPh3 and Et3N . This reaction involves [4 + 2]-cycloaddition with the (β,γ) double bond of one allene as the dienophile; the double bonds at the α-aryl-(β',γ') group and (α,β)-carbons of the second allene act as the diene part. A subsequent proton shift also takes place. Upon treating allenylphosphine oxides with Pd(OAc)2 [stoichiometry 2:1] in the presence of PPh3/Ag2CO3, a [Pd]-complex is isolated and structurally characterized. This complex can be used as a catalyst for C-C bond-forming reactions of phosphorus-based allenes with 2-iodophenol. Densely substituted 3,6-diphenylpyridazines are conveniently obtained in excellent yields by a thermally induced regioselective Inverse Electron Demand Diels-Alder (IEDDA) reaction of allenes with 3,6-diphenyltetrazine, followed by a [1,3]-H shift.
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Affiliation(s)
- Mallepalli Shankar
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Adula Kalyani
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Mandala Anitha
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Alla Siva Reddy
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - K C Kumara Swamy
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
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11
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Guo R, Witherspoon BP, Brown MK. Stereoselective [2+2]-Cycloadditions of chiral allenic ketones and alkenes: Applications towards the synthesis of benzocyclobutenes and endiandric acids. Tetrahedron 2022; 122:132932. [PMID: 36685046 PMCID: PMC9850822 DOI: 10.1016/j.tet.2022.132932] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cyclobutanes are important motifs that have found utility in many contexts. Prior work has demonstrated an enantioselective isomerization/stereoselective [2 + 2] as a means to access bicyclo [4.2.0] octanes. Herein, the utility of this method is demonstrated towards the synthesis of benzocyclobutenes and a key intermediate towards the endiandric acids.
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Affiliation(s)
| | | | - M. Kevin Brown
- Indiana University, Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
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12
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Ota K, Miyaoka H, Kamaike K. Unified Approach to ent-Eudesmane-Type Terpenoid Synthesis: Total Synthesis of Sinupol and Eutyscoparin A. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1643-5729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Abstract
ent-Eudesmane-type terpenoids constitute a large class of natural products derived from plants, animals, and bacteria. We describe a synthetic approach to two ent-eudesmane-type terpenoids, sinupol and eutyscoparin A, that relies on a key π-facial- and endo/exo-selective intramolecular Diels–Alder reaction to set the C-5–C-10 stereotriads. Further key transformations of trans-fused decalin include conversion to methyl ketone via a versatile thioester intermediate and appropriate functionalization toward target compounds.
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13
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Mukhopadhyay S, Boobalan R, Chein RJ. Oxathiaborolium-catalyzed enantioselective [2 + 2] cycloadditions. Org Biomol Chem 2022; 20:8405-8409. [DOI: 10.1039/d2ob01779b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The one-pot-prepared oxathiaborolium pentachlorostannate is an excellent Lewis acid and is successfully used to catalyze the [2 + 2] cycloadditions of N-substituted maleimides and silyl enol ethers with excellent enantioselectivities.
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Affiliation(s)
| | | | - Rong-Jie Chein
- Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan
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14
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Biswas S, Parsutkar MM, Jing SM, Pagar VV, Herbort JH, RajanBabu TV. A New Paradigm in Enantioselective Cobalt Catalysis: Cationic Cobalt(I) Catalysts for Heterodimerization, Cycloaddition, and Hydrofunctionalization Reactions of Olefins. Acc Chem Res 2021; 54:4545-4564. [PMID: 34847327 PMCID: PMC8721816 DOI: 10.1021/acs.accounts.1c00573] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
One of the major challenges facing organic synthesis in the 21st century is the utilization of abundantly available feedstock chemicals for fine chemical synthesis. Regio- and enantioselective union of easily accessible 1,3-dienes and other feedstocks like ethylene, alkyl acrylates, and aldehydes can provide valuable building blocks adorned with latent functionalities for further synthetic elaboration. Through an approach that relies on mechanistic insights and systematic examination of ligand and counterion effects, we developed an efficient cobalt-based catalytic system [(P∼P)CoX2/Me3Al] (P∼P = bisphosphine) to effect the first enantioselective heterodimerization of several types of 1,3-dienes with ethylene. In addition to simple cyclic and acyclic dienes, siloxy-1,3-dienes participate in this reaction, giving highly functionalized, nearly enantiopure silyl enolates, which can be used for subsequent C-C and C-X bond-forming reactions. As our understanding of the mechanism of this reaction improved, our attention was drawn to more challenging partners like alkyl acrylates (one of the largest volume feedstocks) as the olefin partners instead of ethylene. Prompted by the intrinsic limitations of using aluminum alkyls as the activators for this reaction, we explored the fundamental chemistry of the lesser known (P∼P)Co(I)X species and discovered that in the presence of halide sequestering agents, such as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBARF) or (C6F5)3B, certain chiral bisphosphine complexes are superb catalysts for regio- and enantioselective heterodimerization of 1,3-dienes and alkyl acrylates. We have since found that these cationic Co(I) catalysts, most conveniently prepared in situ by reduction of the corresponding cobalt(II) halide complexes by zinc in the presence of NaBARF, promote enantioselective [2 + 2]-cycloaddition between alkynes and an astonishing variety of alkenyl derivatives to give highly functionalized cyclobutenes. In reactions between 1,3-enynes and ethylene, the [2 + 2]-cycloaddition between the alkyne and ethylene is followed by a 1,4-addition of ethylene in a tandem fashion to give nearly enantiopure cyclobutanes with an all-carbon quaternary center, giving a set of molecules that maps well into many medicinally relevant compounds. In another application, we find that the cationic Co(I)-catalysts promote highly selective hydroacylation and 1,2-hydroboration of prochiral 1,3-dienes. Further, we find that a cationic Co(I)-catalyst promotes cycloisomerization followed by hydroalkenylation of 1,6-enynes to produce highly functionalized carbo- and heterocyclic compounds. Surprisingly the regioselectivity of the alkene addition depends on whether it is a simple alkene or an acrylate, and the acrylate addition produces an uncommon Z-adduct. This Account will provide a summary of the enabling basic discoveries and the attendant developments that led to the unique cationic Co(I)-complexes as catalysts for disparate C-C and C-B bond-forming reactions. It is our hope that this Account will stimulate further work with these highly versatile catalysts which are derived from an earth-abundant metal.
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Affiliation(s)
- Souvagya Biswas
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Mahesh M Parsutkar
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Stanley M Jing
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Vinayak V Pagar
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - James H Herbort
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - T V RajanBabu
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
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15
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Ning X, Chen Y, Hu F, Xia Y. Palladium-Catalyzed Carbene Coupling Reactions of Cyclobutanone N-Sulfonylhydrazones. Org Lett 2021; 23:8348-8352. [PMID: 34623163 DOI: 10.1021/acs.orglett.1c03052] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Described herein are the palladium-catalyzed cross-coupling reactions of cyclobutanone-derived N-sulfonylhydrazones with aryl or benzyl halides, suggesting that the metal carbene process and β-hydride elimination can smoothly occur in strained ring systems. Structurally diversified products including cyclobutenes, methylenecyclobutanes, and conjugated dienes are selectively afforded in good to excellent yields. Preliminary success in asymmetric carbene coupling reactions in strained ring systems has been achieved, providing a promising route for the synthesis of enantioenriched four-membered-ring molecules.
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Affiliation(s)
- Xiaoqin Ning
- West China School of Public Health and West China Fourth Hospital, and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Yongke Chen
- West China School of Public Health and West China Fourth Hospital, and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Fangdong Hu
- School of Chemistry and Chemical Engineering, Linyi University, Linyi 276000, China
| | - Ying Xia
- West China School of Public Health and West China Fourth Hospital, and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, China
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16
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Boobalan R, Chein RJ. Oxathiaborolium-Catalyzed Enantioselective [4 + 2] Cycloaddition and Its Application in Lewis Acid Coordinated and Chiral Lewis Acid Catalyzed [4 + 2] Cycloaddition. Org Lett 2021; 23:6760-6764. [PMID: 34410733 DOI: 10.1021/acs.orglett.1c02345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nascency of second-generation sulfur-stabilized borenium cations by halophilic Lewis acid SnCl4 leads to highly active chiral Lewis acids that are very effective catalysts for [4 + 2] cycloaddition. Oxathiaborolium pentachlorostannate (5-10 mol %) successfully catalyzed cycloaddition of various dienes and dienophiles to afford cycloadducts with excellent enantioselectivity (20 examples, up to 99% ee). This super Lewis acid also exhibited good enantioselectivity for the first Lewis acid coordinated and chiral Lewis acid catalyzed [4 + 2] cycloaddition to α,β-unsaturated mixed ester amide.
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Affiliation(s)
| | - Rong-Jie Chein
- Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan
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17
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Zhong X, Tan J, Qiao J, Zhou Y, Lv C, Su Z, Dong S, Feng X. Catalytic asymmetric synthesis of spirocyclobutyl oxindoles and beyond via [2+2] cycloaddition and sequential transformations. Chem Sci 2021; 12:9991-9997. [PMID: 34377393 PMCID: PMC8317662 DOI: 10.1039/d1sc02681j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 06/22/2021] [Indexed: 02/05/2023] Open
Abstract
Efficient asymmetric synthesis of a collection of small molecules with structural diversity is highly important to drug discovery. Herein, three distinct types of chiral cyclic compounds were accessible by enantioselective catalysis and sequential transformations. Highly regio- and enantioselective [2+2] cycloaddition of (E)-alkenyloxindoles with the internal C[double bond, length as m-dash]C bond of N-allenamides was achieved with N,N'-dioxide/Ni(OTf)2 as the catalyst. Various optically active spirocyclobutyl oxindole derivatives were obtained under mild conditions. Moreover, formal [4+2] cycloaddition products occurring at the terminal C[double bond, length as m-dash]C bond of N-allenamides, dihydropyran-fused indoles, were afforded by a stereospecific sequential transformation with the assistance of a catalytic amount of Cu(OTf)2. In contrast, performing the conversion under air led to the formation of γ-lactones via the water-involved deprotection and rearrangement process. Experimental studies and DFT calculations were performed to probe the reaction mechanism.
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Affiliation(s)
- Xia Zhong
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Jiuqi Tan
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Jianglin Qiao
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Yuqiao Zhou
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Cidan Lv
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Zhishan Su
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Shunxi Dong
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
| | - Xiaoming Feng
- Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China http://www.scu.edu.cn/chem_asl/
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18
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Barday M, Bouillac P, Coquerel Y, Amatore M, Constantieux T, Rodriguez J. Enantioselective Organocatalytic Syntheses and Ring‐Expansions of Cyclobutane Derivatives. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Manuel Barday
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2 Marseille France
| | - Pierre Bouillac
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2 Marseille France
| | - Yoann Coquerel
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2 Marseille France
| | - Muriel Amatore
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2 Marseille France
| | | | - Jean Rodriguez
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2 Marseille France
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19
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Regio- and stereoselective synthesis of cyclobutanes by nickel-catalyzed homodimerizative [2 + 2] cycloaddition using allenamides. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.152974] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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20
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Yan P, Zhong C, Zhang J, Liu Y, Fang H, Lu P. 3‐(Methoxycarbonyl)Cyclobutenone as a Reactive Dienophile in Enantioselective Diels–Alder Reactions Catalyzed by Chiral Oxazaborolidinium Ions. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202014308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Peng Yan
- Department of Research Center for Molecular Recognition and Synthesis Department of Chemistry Fudan University 220 Handan Lu Shanghai 200433 P. R. China
| | - Changxu Zhong
- Department of Research Center for Molecular Recognition and Synthesis Department of Chemistry Fudan University 220 Handan Lu Shanghai 200433 P. R. China
| | - Jie Zhang
- College of Chemistry and Life Advanced Institute of Materials Science Changchun University of Technology Changchun 130012 P. R. China
| | - Yu Liu
- College of Chemistry and Life Advanced Institute of Materials Science Changchun University of Technology Changchun 130012 P. R. China
| | - Huayi Fang
- School of Materials Science and Engineering Tianjin Key Lab for Rare Earth Materials and Applications Nankai University Tianjin 300350 P. R. China
| | - Ping Lu
- Department of Research Center for Molecular Recognition and Synthesis Department of Chemistry Fudan University 220 Handan Lu Shanghai 200433 P. R. China
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21
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Yan P, Zhong C, Zhang J, Liu Y, Fang H, Lu P. 3-(Methoxycarbonyl)Cyclobutenone as a Reactive Dienophile in Enantioselective Diels-Alder Reactions Catalyzed by Chiral Oxazaborolidinium Ions. Angew Chem Int Ed Engl 2021; 60:4609-4613. [PMID: 33201584 DOI: 10.1002/anie.202014308] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/16/2020] [Indexed: 11/06/2022]
Abstract
Cyclobutenone has been used as a highly reactive dienophile in Diels-Alder reactions, however, no enantioselective example has been reported. We disclose herein a chiral oxazaborolidine-aluminum bromide catalyzed enantioselective Diels-Alder reaction of 3-alkoxycarbonyl cyclobutenone with a variety of dienes. Furthermore, a total synthesis of (-)-kingianin F was completed for the first time via enantioenriched cycloadduct bicyclo[4.2.0]octane derivative.
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Affiliation(s)
- Peng Yan
- Department of Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, P. R. China
| | - Changxu Zhong
- Department of Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, P. R. China
| | - Jie Zhang
- College of Chemistry and Life, Advanced Institute of Materials Science, Changchun University of Technology, Changchun, 130012, P. R. China
| | - Yu Liu
- College of Chemistry and Life, Advanced Institute of Materials Science, Changchun University of Technology, Changchun, 130012, P. R. China
| | - Huayi Fang
- School of Materials Science and Engineering, Tianjin Key Lab for Rare Earth Materials and Applications, Nankai University, Tianjin, 300350, P. R. China
| | - Ping Lu
- Department of Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, P. R. China
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22
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Kumar AS, Chauhan S, Swamy KCK. Contrasting Carboannulation Involving δ-Acetoxy Allenoate as a Four-Carbon Synthon Using DABCO and DMAP: Access to Spiro-carbocyclic and m-Teraryl Scaffolds. Org Lett 2021; 23:1123-1129. [PMID: 33480700 DOI: 10.1021/acs.orglett.1c00076] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Spiro-annulation involving δ-acetoxy allenoate and alkyl benzoisothiazole dioxide (N-sulfonyl ketimine) triggered by DABCO/MeCO2H combination leads to an essentially single diastereomer via chemo- and regiospecific [4 + 2]-carboannulation and a new hydroxyl group is introduced. In contrast, DMAP-catalyzed benzannulation using the same reactants affords unsymmetrical m-teraryls via Mannich coupling, sequential proton transfers, and C-N bond cleavage. Here, δ-acetoxy allenoate serves as a 4C-synthon and the carboannulation is completely base dependent and mutually exclusive.
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Affiliation(s)
- A Sanjeeva Kumar
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Sachin Chauhan
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - K C Kumara Swamy
- School of Chemistry, University of Hyderabad, Hyderabad 500046, Telangana, India
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23
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Zeng L, Xu J, Zhang D, Yan Z, Cheng G, Rao W, Gao L. Catalytic Enantioselective [2+2] Cycloaddition of α-Halo Acroleins: Construction of Cyclobutanes Containing Two Tetrasubstituted Stereocenters. Angew Chem Int Ed Engl 2020; 59:21890-21894. [PMID: 32803881 DOI: 10.1002/anie.202008465] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/31/2020] [Indexed: 01/16/2023]
Abstract
A catalytic enantioselective formal [2+2] cycloaddition between α-halo acroleins and electronically diverse arylalkenes is described. In the presence of (S)-oxazaborolidinium cation as the catalyst, densely functionalized cyclobutanes containing two vicinal tetrasubstituted stereocenters were produced in high yields and high diastereoselectivities with excellent enantioselectivities. Mechanistic studies revealed that the cis isomer could be transformed into the trans isomer via an enantiocontrolled process. A gram-scale reaction of this catalytic method was used to demonstrate its synthetic potential.
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Affiliation(s)
- Lei Zeng
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
| | - Jingjing Xu
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
| | - Dongsheng Zhang
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
| | - Zhongliang Yan
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
| | - Guolin Cheng
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
| | - Weidong Rao
- Jiangsu Key Laboratory of Biomass-Based Green Fuels and Chemicals, College of Chemical Engineering, Nanjing Forestry University, Nanjing, China
| | - Lizhu Gao
- College of Materials Science and Engineering, Huaqiao University, No.668 Jimei Avenue, Xiamen, Fujian, China
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24
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He D, Xu X, Lu Y, Zhou MJ, Xing X. Asymmetric Transfer Hydrogenation of Densely Functionalized Diheteroaryl and Diaryl Ketones by a Ru-Catalyst of Minimal Stereogenicity. Org Lett 2020; 22:8458-8463. [PMID: 33044077 DOI: 10.1021/acs.orglett.0c03064] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A highly enantioselective asymmetric transfer hydrogenation (ATH) of densely functionalized diheteroaryl and diaryl ketones was developed using Ru-catalysts of minimal stereogenicity. Various ketone substrates with structurally and electronically similar groups attached to the prochiral centers were reduced successfully in good to excellent enantioselectivities and yields. This protocol provides practical and efficient access to chiral diheteroarylmethanols and benzhydrols, which are key intermediates in pharmaceuticals and biologically active compounds.
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Affiliation(s)
- Dongxu He
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xingjun Xu
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China.,College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Yi Lu
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - Min-Jie Zhou
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xiangyou Xing
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
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25
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Guo R, Beattie SR, Krysan DJ, Brown MK. Enantioselective Synthesis of (+)-Hippolide J and Reevaluation of Antifungal Activity. Org Lett 2020; 22:7743-7746. [PMID: 32969231 DOI: 10.1021/acs.orglett.0c02979] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A synthesis of the reported antifungal agent (+)-hippolide J is presented. The rapid assembly of the natural product was enabled through implementation of an enantioselective isomerization/[2 + 2]-cycloaddition sequence. Due to the simplicity of the route, >100 mg of the natural product were prepared in a single pass. Anitfungal assays of hippolide J, however, confirmed that it showed no activity against several fungal strains, contrary to the isolation report.
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Affiliation(s)
- Renyu Guo
- Indiana University, Department of Chemistry, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Sarah R Beattie
- University of Iowa, Carver College of Medicine, Departments of Pediatrics and Microbiology/Immunology, 200 South Grand Avenue, Iowa City, Iowa 52242, United States
| | - Damian J Krysan
- University of Iowa, Carver College of Medicine, Departments of Pediatrics and Microbiology/Immunology, 200 South Grand Avenue, Iowa City, Iowa 52242, United States
| | - M Kevin Brown
- Indiana University, Department of Chemistry, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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26
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Zeng L, Xu J, Zhang D, Yan Z, Cheng G, Rao W, Gao L. Catalytic Enantioselective [2+2] Cycloaddition of α‐Halo Acroleins: Construction of Cyclobutanes Containing Two Tetrasubstituted Stereocenters. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Lei Zeng
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
| | - Jingjing Xu
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
| | - Dongsheng Zhang
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
| | - Zhongliang Yan
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
| | - Guolin Cheng
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
| | - Weidong Rao
- Jiangsu Key Laboratory of Biomass-Based Green Fuels and Chemicals College of Chemical Engineering Nanjing Forestry University Nanjing China
| | - Lizhu Gao
- College of Materials Science and Engineering Huaqiao University No.668 Jimei Avenue Xiamen Fujian China
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27
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Schwinger DP, Bach T. Chiral 1,3,2-Oxazaborolidine Catalysts for Enantioselective Photochemical Reactions. Acc Chem Res 2020; 53:1933-1943. [PMID: 32880165 PMCID: PMC7497702 DOI: 10.1021/acs.accounts.0c00379] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Asymmetric synthesis has posed a significant challenge to organic chemists for over a century. Several strategies have been developed to synthesize enantiomerically enriched compounds, which are ubiquitous in the pharmaceutical and agrochemical industries. While many organometallic and organic catalysts have been found to mediate thermal enantioselective reactions, the field of photochemistry lacks similar depth. Recently, chiral 1,3,2-oxazaborolidines have made the transition from Lewis acids that were exclusively applied to thermal reactions to catalysts for enantioselective photochemical reactions. Due to their modular structure, various 1,3,2-oxazaborolidines are readily available and can be easily fitted to a given chemical transformation. Their use holds great promise for future developments in photochemistry. This Account gives an overview of the substrate classes that are known to undergo enantioselective photochemical transformations in the presence of chiral 1,3,2-oxazaborolidines and touches on the catalytic mode of action, on the proposed enantiodifferentiation mechanism, as well as on recent computational studies.Based on the discovery that the presence of Lewis acids enhances the efficiency of coumarin [2 + 2] photocycloadditions, chiral 1,3,2-oxazaborolidines were applied in 2010 for the first time to prepare enantiomerically enriched photoproducts. These Lewis acids were then successfully used in intramolecular [2 + 2] photocycloaddition reactions of 1-alkenoyl-5,6-dihydro-4-pyridones and 3-alkenyloxy-2-cycloalkenones. In the course of this work, it became evident that the chiral 1,3,2-oxazaborolidine must be tailored to the specific reaction; it was shown that both inter- and intramolecular [2 + 2] photocycloadditions of cyclic enones can be conducted enantioselectively, but the aryl rings of the chiral Lewis acids require different substitution patterns. In all [2 + 2] photocycloaddition reactions in which chiral 1,3,2-oxazaborolidines were used as catalysts, the catalyst loading could not be decreased below 50 mol % without sacrificing enantioselectivity due to competitive racemic background reactions. To overcome this constraint, substrates that reacted exclusively when bound to an oxazaborolidine were tested, notably phenanthrene-9-carboxaldehydes and cyclohexa-2,4-dienones. The former substrate class underwent an ortho photocycloaddition, the latter an oxadi-π-methane rearrangement. Several new 1,3,2-oxazaborolidines were designed, and the products were obtained in high enantioselectivity with only 10 mol % of catalyst. Recently, an iridium-based triplet sensitizer was employed to facilitate enantioselective [2 + 2] photocycloadditions of cinnamates with 25 mol % of chiral 1,3,2-oxazaborolidine. In this case, the relatively low catalyst loading was possible because the oxazaborolidine-substrate complex exhibits a lower triplet energy and an improved electronic coupling compared to the uncomplexed substrate, allowing for a selective energy transfer.By synthetic and theoretical studies, it has become evident that chiral 1,3,2-oxazaborolidines are multifaceted catalysts: they change absorption behavior, alter energetic states, and induce chirality. While a diverse set of substrates has been shown to undergo enantioselective photochemical transformations in the presence of chiral 1,3,2-oxazaborolidines either through direct excitation or through triplet sensitization, these catalysts took on different roles for different substrates. Based on the studies presented in this Account, it can be assumed that there are still more photochemical reactions and substrate classes that could profit from chiral 1,3,2-oxazaborolidines.
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Affiliation(s)
- Daniel P. Schwinger
- Department of Chemistry and Catalysis Research Center (CRC), Technical University of Munich, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Thorsten Bach
- Department of Chemistry and Catalysis Research Center (CRC), Technical University of Munich, Lichtenbergstrasse 4, 85747 Garching, Germany
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28
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Yang LL, Evans D, Xu B, Li WT, Li ML, Zhu SF, Houk KN, Zhou QL. Enantioselective Diarylcarbene Insertion into Si-H Bonds Induced by Electronic Properties of the Carbenes. J Am Chem Soc 2020; 142:12394-12399. [PMID: 32539369 PMCID: PMC7605718 DOI: 10.1021/jacs.0c04725] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Catalytic enantioselection usually depends on differences in steric interactions between prochiral substrates and a chiral catalyst. We have discovered a carbene Si-H insertion in which the enantioselectivity depends primarily on the electronic characteristics of the carbene substrate, and the log(er) values are linearly related to Hammett parameters. A new class of chiral tetraphosphate dirhodium catalysts was developed; it shows excellent activity and enantioselectivity for the insertion of diarylcarbenes into the Si-H bond of silanes. Computational and mechanistic studies show how the electronic differences between the two aryls of the carbene lead to differences in energies of the diastereomeric transition states. This study provides a new strategy for asymmetric catalysis exploiting the electronic properties of the substrates.
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Affiliation(s)
- Liang-Liang Yang
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Declan Evans
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Bin Xu
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Wen-Tao Li
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Mao-Lin Li
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Shou-Fei Zhu
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| | - K N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Qi-Lin Zhou
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
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29
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Hancock EN, Wahl JM, Brown MK. Recent advances in the synthesis of gem-dimethylcyclobutane natural products. Nat Prod Rep 2020; 36:1383-1393. [PMID: 30855044 DOI: 10.1039/c8np00083b] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Covering: January 2000 to July 2018 gem-Dimethylcyclobutanes are a common motif found in a multitude of natural products, and thus these structures have captivated synthetic chemists for years. However, until the turn of the century, most synthetic efforts relied upon the use of widely available terpenes, such as pinene or caryophyllene, that already contain the gem-dimethylcyclobutane motif. This approach limits the scope of molecules that can be accessed readily. This review highlights recent syntheses in which the gem-dimethylcyclobutane is assembled via de novo approaches. An outlook on the future of this research area is also provided.
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Affiliation(s)
- Erin N Hancock
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, IN 47405, USA.
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30
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Xu D, Li H, Pan G, Huang P, Oberkofler J, Reich RM, Kühn FE, Guo H. Visible-Light-Induced Dehydrohalogenative Coupling for Intramolecular α-Alkenylation: A Way to Build Seven- and Eight-Membered Rings. Org Lett 2020; 22:4372-4377. [DOI: 10.1021/acs.orglett.0c01391] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Dawen Xu
- Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, P.R. China
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Han Li
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Guangxing Pan
- Academic for Engineering and Technology, Fudan University, 220 Handan Road, Shanghai, 200438, P.R. China
| | - Pan Huang
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Jens Oberkofler
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Robert M. Reich
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Fritz E. Kühn
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
| | - Hao Guo
- Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, P.R. China
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31
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Guo R, Witherspoon BP, Brown MK. Evolution of a Strategy for the Enantioselective Synthesis of (-)-Cajanusine. J Am Chem Soc 2020; 142:5002-5006. [PMID: 32149511 PMCID: PMC7252469 DOI: 10.1021/jacs.0c00359] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The first enantioselective synthesis of (-)-cajanusine is presented. Key features of the route include a rapid synthesis of the [4.2.0]bicyclooctane core by an enantioselective isomerization/stereoselective [2+2]-cycloaddition strategy as well as prominent use of catalytic methods for bond construction. The evolution of the approach is also presented that highlights unexpected roadblocks and how novel solutions were developed.
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Affiliation(s)
- Renyu Guo
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Brittany P Witherspoon
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - M Kevin Brown
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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32
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Hancock EN, Kuker EL, Tantillo DJ, Brown MK. Lessons in Strain and Stability: Enantioselective Synthesis of (+)-[5]-Ladderanoic Acid. Angew Chem Int Ed Engl 2020; 59:436-441. [PMID: 31650679 PMCID: PMC6923594 DOI: 10.1002/anie.201910901] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/14/2019] [Indexed: 11/07/2022]
Abstract
The synthesis of structurally complex and highly strained natural products provides unique challenges and unexpected opportunities for the development of new reactions and strategies. Herein, the synthesis of (+)-[5]-ladderanoic acid is reported. En route to the target, unusual and unexpected strain release driven transformations were uncovered. This occurrence required a drastic revision of the synthetic design that ultimately led to the development of a novel stepwise cyclobutane assembly by an allylboration/Zweifel olefination sequence.
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Affiliation(s)
- Erin N. Hancock
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave. Bloomington, IN 47401
| | - Erin L. Kuker
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave. Bloomington, IN 47401
| | - Dean J. Tantillo
- Department of Chemistry, University of California Davis, 1 Shields Ave. Davis, CA 95616
| | - M. Kevin Brown
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave. Bloomington, IN 47401
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33
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Wen KG, Peng YY, Zeng XP. Advances in the catalytic asymmetric synthesis of quaternary carbon containing cyclobutanes. Org Chem Front 2020. [DOI: 10.1039/d0qo00685h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The advances in the catalytic asymmetric synthesis of quaternary carbon containing cyclobutanes are described.
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Affiliation(s)
- Kai-Ge Wen
- Key Laboratory of Small Functional Organic Molecule
- Ministry of Education and Jiangxi Key Laboratory of Green Chemistry
- College of Chemistry and Chemical Engineering
- Jiangxi Normal University
- Nanchang
| | - Yi-Yuan Peng
- Key Laboratory of Small Functional Organic Molecule
- Ministry of Education and Jiangxi Key Laboratory of Green Chemistry
- College of Chemistry and Chemical Engineering
- Jiangxi Normal University
- Nanchang
| | - Xing-Ping Zeng
- Key Laboratory of Small Functional Organic Molecule
- Ministry of Education and Jiangxi Key Laboratory of Green Chemistry
- College of Chemistry and Chemical Engineering
- Jiangxi Normal University
- Nanchang
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34
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Hancock EN, Kuker EL, Tantillo DJ, Brown MK. Lessons in Strain and Stability: Enantioselective Synthesis of (+)‐[5]‐Ladderanoic Acid. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201910901] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Erin N. Hancock
- Department of Chemistry Indiana University 800 E. Kirkwood Ave. Bloomington IN 47401 USA
| | - Erin L. Kuker
- Department of Chemistry Indiana University 800 E. Kirkwood Ave. Bloomington IN 47401 USA
| | - Dean J. Tantillo
- Department of Chemistry University of California Davis 1 Shields Ave. Davis CA 95616 USA
| | - M. Kevin Brown
- Department of Chemistry Indiana University 800 E. Kirkwood Ave. Bloomington IN 47401 USA
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35
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Parsutkar MM, Pagar VV, RajanBabu TV. Catalytic Enantioselective Synthesis of Cyclobutenes from Alkynes and Alkenyl Derivatives. J Am Chem Soc 2019; 141:15367-15377. [PMID: 31476274 DOI: 10.1021/jacs.9b07885] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Discovery of enantioselective catalytic reactions for the preparation of chiral compounds from readily available precursors, using scalable and environmentally benign chemistry, can greatly impact their design, synthesis, and eventually manufacture on scale. Functionalized cyclobutanes and cyclobutenes are important structural motifs seen in many bioactive natural products and pharmaceutically relevant small molecules. They are also useful precursors for other classes of organic compounds such as other cycloalkane derivatives, heterocyclic compounds, stereodefined 1,3-dienes, and ligands for catalytic asymmetric synthesis. The simplest approach to make cyclobutenes is through an enantioselective [2 + 2]-cycloaddition between an alkyne and an alkenyl derivative, a reaction which has a long history. Yet known reactions of this class that give acceptable enantioselectivities are of very narrow scope and are strictly limited to activated alkynes and highly reactive alkenes. Here, we disclose a broadly applicable enantioselective [2 + 2]-cycloaddition between wide variety of alkynes and alkenyl derivatives, two of the most abundant classes of organic precursors. The key cycloaddition reaction employs catalysts derived from readily synthesized ligands and an earth-abundant metal, cobalt. Over 50 different cyclobutenes with enantioselectivities in the range of 86-97% ee are documented. With the diverse functional groups present in these compounds, further diastereoselective transformations are easily envisaged for synthesis of highly functionalized cyclobutanes and cyclobutenes. Some of the novel observations made during these studies including a key role of a cationic Co(I)-intermediate, ligand and counterion effects on the reactions, can be expected to have broad implications in homogeneous catalysis beyond the highly valuable synthetic intermediates that are accessible by this route.
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Affiliation(s)
- Mahesh M Parsutkar
- Department of Chemistry and Biochemistry , The Ohio State University , 100 West 18th Avenue , Columbus , Ohio 43210 , United States
| | - Vinayak Vishnu Pagar
- Department of Chemistry and Biochemistry , The Ohio State University , 100 West 18th Avenue , Columbus , Ohio 43210 , United States
| | - T V RajanBabu
- Department of Chemistry and Biochemistry , The Ohio State University , 100 West 18th Avenue , Columbus , Ohio 43210 , United States
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36
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O'Hara C, Yang CH, Francis AJ, Newell BS, Wang H, Resendiz MJE. Photocycloaddition of S, S-Dioxo-benzothiophene-2-methanol, Reactivity in the Solid State and in Solution: Mechanistic Studies and Diastereoselective Formation of Cyclobutyl Rings. J Org Chem 2019; 84:9714-9725. [PMID: 31298854 DOI: 10.1021/acs.joc.9b01354] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation of cyclobutane rings is a promising strategy in the development of potential drugs and/or synthetic intermediates, typically challenging to obtain due to their constrained nature. In this work, the [2 + 2] photocycloaddition reaction of S,S-dioxobenzothiophene-2-methanol was explored in microcrystalline powders and its outcome was compared to that observed in solution. It was found that the molecular constraints inherited within the crystal lattice provide an optimal environment that leads to photodimer 4 as the major product in ca. 9.6:0.4 diastereomeric ratios with conversions >95%. The photoreaction was analyzed via X-ray, displaying a crystalline-to-amorphous transformation and showing that units of monomer 2 align to generate the corresponding dimer with a syn-head-to-tail regio- and diastereoselectivity. This result contrasted with that obtained in solution, where the diastereomeric ratio varied as a function of the excited state that is generated, to yield mixtures of dimers 4 and 5 (anti-head-to-tail), or exclusively 5 in the triplet-sensitized photoreaction, in the presence of benzophenone. Density functional theory was used to elucidate a plausible detailed mechanism for the phototransformation, which aided in justifying the results that led to the corresponding dimers. X-ray crystallography allowed us to establish the stereochemical assignment of the obtained cyclobutyl rings. Thus, the use of solid-state or solution photochemistry can be used to gain control of diastereo- and regioselectivities in the formation of this important moiety.
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Affiliation(s)
- Chelsea O'Hara
- Department of Chemistry , University of Colorado Denver , Science Building 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Chou-Hsun Yang
- Department of Chemistry , University of Colorado Denver , Science Building 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Andrew J Francis
- Department of Chemistry , University of Colorado Denver , Science Building 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Brian S Newell
- Department of Chemistry, Central Instrument Facility , Colorado State University , C1D Chemistry Building 1872, Campus Delivery , Fort Collins , Colorado 80523-1872 , United States
| | - Haobin Wang
- Department of Chemistry , University of Colorado Denver , Science Building 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Marino J E Resendiz
- Department of Chemistry , University of Colorado Denver , Science Building 1151 Arapahoe Street , Denver , Colorado 80204 , United States
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37
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Conner ML, Wiest JM, Brown MK. Thioallenoates in Catalytic Enantioselective [2+2]-Cycloadditions with Unactivated Alkenes. Tetrahedron 2019; 75:3265-3271. [PMID: 33100416 DOI: 10.1016/j.tet.2019.04.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The application of thioallenoates to catalytic enantioselective [2+2]-cycloadditions with unactivated alkenes is reported.In many cases, the thioallenoates examined exhibit superior reactivity and selectivity compared to the alkoxy analogs generally used in these cycloadditions.
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Affiliation(s)
- Michael L Conner
- Indiana University, Department of Chemistry, 800 E. Kirkwood Ave. Bloomington, IN 47405
| | - Johannes M Wiest
- Indiana University, Department of Chemistry, 800 E. Kirkwood Ave. Bloomington, IN 47405
| | - M Kevin Brown
- Indiana University, Department of Chemistry, 800 E. Kirkwood Ave. Bloomington, IN 47405
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38
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Daub ME, Jung H, Lee BJ, Won J, Baik MH, Yoon TP. Enantioselective [2+2] Cycloadditions of Cinnamate Esters: Generalizing Lewis Acid Catalysis of Triplet Energy Transfer. J Am Chem Soc 2019; 141:9543-9547. [PMID: 31145856 DOI: 10.1021/jacs.9b04643] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We report the enantioselective [2+2] cycloaddition of simple cinnamate esters, the products of which are useful synthons for the controlled assembly of cyclobutane natural products. This method utilizes a cocatalytic system in which a chiral Lewis acid accelerates the transfer of triplet energy from an excited-state Ir(III) photocatalyst to the cinnamate ester. Computational evidence indicates that the principal role of the Lewis acid cocatalyst is to lower the absolute energies of the substrate frontier molecular orbitals, leading to greater electronic coupling between the sensitizer and substrate and increasing the rate of the energy transfer event. These results suggest Lewis acids can have multiple beneficial effects on triplet sensitization reactions, impacting both the thermodynamic driving force and kinetics of Dexter energy transfer.
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Affiliation(s)
- Mary Elisabeth Daub
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Hoimin Jung
- Department of Chemistry , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea.,Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 34141 , Republic of Korea
| | - Byung Joo Lee
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Joonghee Won
- Department of Chemistry , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea.,Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 34141 , Republic of Korea
| | - Mu-Hyun Baik
- Department of Chemistry , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , Republic of Korea.,Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 34141 , Republic of Korea
| | - Tehshik P Yoon
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
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39
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Wang ZX, Li BJ. Construction of Acyclic Quaternary Carbon Stereocenters by Catalytic Asymmetric Hydroalkynylation of Unactivated Alkenes. J Am Chem Soc 2019; 141:9312-9320. [PMID: 31117476 DOI: 10.1021/jacs.9b03027] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Quaternary carbon stereocenters are common structural motifs in organic synthesis. The construction of these stereocenters in a catalytic and enantioselective manner remains a prominent synthetic challenge. In particular, methods for the synthesis of alkyne-substituted quaternary carbon stereocenters are very rare. Previous catalytic systems for hydroalkynylation of alkenes create tertiary stereocenters. We describe here an iridium catalyzed asymmetric hydroalkynylation of nonactivated trisubstituted alkene. The hydroalkynylation of β,γ-unsaturated amides occurs with high regio- and enantioselectivities to afford alkyne-substituted acyclic quaternary carbon stereocenters. Computational and experimental data suggest that the enantioselectivity is not only determined by the facial selectivity of the alkene but also by an alkene isomerization process. This strategy provides an efficient method to access alkyne-substituted acyclic quaternary carbon stereocenters with minimally functionalized starting materials.
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Affiliation(s)
- Zi-Xuan Wang
- Center of Basic Molecular Science (CBMS), Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Bi-Jie Li
- Center of Basic Molecular Science (CBMS), Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
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40
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Poplata S, Bauer A, Storch G, Bach T. Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications. Chemistry 2019; 25:8135-8148. [PMID: 30983074 PMCID: PMC6618137 DOI: 10.1002/chem.201901304] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Indexed: 11/16/2022]
Abstract
The intramolecular [2+2] photocycloaddition of 3‐alkenyl‐2‐cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3‐activated oxazaborolidine as the Lewis acid. An extensive screening of proline‐derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3‐position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)‐italicene.
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Affiliation(s)
- Saner Poplata
- Department Chemie and Catalysis Research Center (CRC), Technische Universität München, 85747, Garching, Germany
| | - Andreas Bauer
- Department Chemie and Catalysis Research Center (CRC), Technische Universität München, 85747, Garching, Germany
| | - Golo Storch
- Department Chemie and Catalysis Research Center (CRC), Technische Universität München, 85747, Garching, Germany
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC), Technische Universität München, 85747, Garching, Germany
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41
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Wei S, Yin L, Wang SR, Tang Y. Catalyst-Controlled Chemoselective All-Alkene [2 + 2 + 2] and [2 + 2] Cyclizations of Enamides with Electron-Deficient Alkenes. Org Lett 2019; 21:1458-1462. [DOI: 10.1021/acs.orglett.9b00209] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Song Wei
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
| | - Lei Yin
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
| | - Sunewang R. Wang
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
| | - Yong Tang
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
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