1
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Bora SK, Biswas S, Behera BK, Saikia AK. Stereoselective synthesis of gem-dihalopiperidines via the halo-aza-Prins cyclization reaction: access to piperidin-4-ones and pyridines. Org Biomol Chem 2024; 22:3893-3903. [PMID: 38654601 DOI: 10.1039/d4ob00338a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
An efficient methodology for the synthesis of 4,4-dihalopiperidine derivatives in excellent yields has been developed using N-(3-halobut-3-en-1-yl)-4-methylbenzenesulfonamide and an aldehyde catalyzed by In(OTf)3. The reaction involves an initial formation of a six-membered carbocation via the aza-Prins cyclization reaction followed by a nucleophilic attack by a halide ion to give 4,4-dihalopiperidine. The dihalopiperidine is converted to tetrahydropiperidinone using Ac2O/Et3N in DCM/H2O (1 : 1). It is also utilized for the synthesis of pyridine scaffolds by treatment with DBU. Furthermore, the dihalopiperidine is transformed to its enol ether derivatives using KOH in alcohol.
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Affiliation(s)
- Surjya Kumar Bora
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Subhamoy Biswas
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Bipin Kumar Behera
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Anil K Saikia
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
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2
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Hernandez J, Lawrie AP, Frontier AJ. Alkynyl Halo-Aza-Prins Annulative Couplings. J Org Chem 2023; 88:16065-16075. [PMID: 37971946 PMCID: PMC10696554 DOI: 10.1021/acs.joc.3c01305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/22/2023] [Accepted: 10/05/2023] [Indexed: 11/19/2023]
Abstract
This article is a comprehensive report describing our studies in the field of aza-alkynyl Prins chemistry, comparing and contrasting the different reaction partners and reactivities observed during method development. The synthetic strategies combine an alkynyl aza-Prins coupling with an annulation, enabling the preparation of different nitrogen-containing heterocycles. Different iminium ions are explored as viable electrophiles for an alkynyl Prins cyclization, terminated by capture with a halogen nucleophile to form a vinyl halide. The synthetic utility of this functional handle is exploited through a number of Suzuki cross-couplings, allowing for the preparation of a modest library of compounds. In most cases, the Prins couplings are highly selective for the vinyl halides with E geometry, resulting from anti-addition across the alkyne.
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Affiliation(s)
- Jackson
J. Hernandez
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alexandra P. Lawrie
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alison J. Frontier
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
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3
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Biswas S, Shit S, Behera BK, Sahu AK, Saikia AK. Leveraging cascade alkynyl Prins cyclization towards the stereoselective synthesis of spiro-furan quinazolinone scaffolds. Chem Commun (Camb) 2023; 59:14301-14304. [PMID: 37965888 DOI: 10.1039/d3cc04464e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent yields with exclusive E-selectivity under ambient conditions. Furthermore, late-stage modifications incorporate bromide and acetyl functionalities into the synthesized spiro-heterocycles.
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Affiliation(s)
- Subhamoy Biswas
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Sudip Shit
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Bipin Kumar Behera
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Archana Kumari Sahu
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Anil K Saikia
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
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4
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Feng L, Teng Y, Yu X, Wang Z, Rao W. Brønsted Acid-Catalyzed Dehydrative Nazarov-Type Cyclization/C2-N1 Cleavage Cascade of Perfluoroalkylated 3-Indolyl(2-benzothienyl)methanols. Org Lett 2023. [PMID: 37384549 DOI: 10.1021/acs.orglett.3c01503] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
A novel and unprecedented p-toluenesulfonic acid-catalyzed dehydrative Nazarov-type cyclization/C2-N1 bond cleavage cascade reaction of perfluoroalkylated 3-indolyl(2-benzothienyl)methanols has been developed. This reaction provides an efficient and practical protocol for the construction of highly functionalized benzothiophene-fused cyclopentenones with exclusive stereoselectivity. In addition, this cascade transformation also delineates a rare example of the involvement of the selective C2-N1 bond cleavage of indoles.
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Affiliation(s)
- Li Feng
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Yuling Teng
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Xiangdong Yu
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Zeliang Wang
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Weidong Rao
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
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5
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Milosavljevic A, Holt C, Frontier AJ. Nitrogen-interrupted halo-Prins/ halo-Nazarov fragment coupling cascade for the synthesis of indolines. Chem Sci 2023; 14:5431-5437. [PMID: 37234889 PMCID: PMC10208031 DOI: 10.1039/d3sc00986f] [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: 02/22/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023] Open
Abstract
The nitrogen-interrupted Nazarov cyclization can be a powerful method for the stereocontrolled synthesis of sp3-rich N-heterocycles. However, due to the incompatibility between the basicity of nitrogen and the acidic reaction conditions, examples of this type of Nazarov cyclization are scarce. Herein, we report a one-pot nitrogen-interrupted halo-Prins/halo-Nazarov coupling cascade that joins two simple building blocks, an enyne and a carbonyl partner, to furnish functionalized cyclopenta[b]indolines with up to four contiguous stereocenters. For the first time, we provide a general method for the alkynyl halo-Prins reaction of ketones, thus enabling the formation of quaternary stereocenters. Additionally, we describe the outcomes of secondary alcohol enyne couplings, which exhibit helical chirality transfer. Furthermore, we investigate the impact of aniline enyne substituents on the reaction and evaluate the tolerance of different functional groups. Finally, we discuss the reaction mechanism and demonstrate various transformations of the prepared indoline scaffolds, highlighting their applicability in drug discovery campaigns.
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Affiliation(s)
| | - Connor Holt
- Department of Chemistry, University of Rochester Rochester NY USA 14627-0216
- Worldwide Research and Development, Pfizer, Inc. Eastern Point Road, Groton Connecticut 06340 USA
| | - Alison J Frontier
- Department of Chemistry, University of Rochester Rochester NY USA 14627-0216
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6
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Hernandez JJ, Frontier AJ. Alkynyl Prins carbocyclization cascades for the synthesis of linear-fused heterocyclic ring systems. Chem Sci 2022; 13:13836-13842. [PMID: 36544720 PMCID: PMC9710218 DOI: 10.1039/d2sc04750k] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/04/2022] [Indexed: 11/12/2022] Open
Abstract
We report a Brønsted acid-catalyzed carbocyclization cascade, featuring condensation of an alcohol/sulfonamide with an aldehyde followed by an intramolecular three-component coupling involving an alkyne, an oxocarbenium/iminium ion, and an arene. A formal cycloaddition is embedded in the cationic cascade, which enables the synthesis of a wide range of fused heterotricycles. The diastereoselectivity of the cascade is studied using secondary alcohols/sulfonamides with different carbonyl partners. The described method results in the preparation of synthetically versatile scaffolds with ample opportunity for further derivatization at the resulting tetrasubstituted olefin, or by inclusion of other functionalizable motifs from the starting materials. It is worth noting that this chemistry also facilitates the synthesis of piperidines and 1,4-oxazepanes, as well as the inclusion of indoles and benzofurans, which are privileged motifs for medicinal chemistry. Herein we present the generality of this approach and some chemical transformations that can be achieved with our substrates.
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Affiliation(s)
- Jackson J. Hernandez
- Department of Chemistry, University of Rochester120 Trustee RoadRochesterNew York 14611USA
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester120 Trustee RoadRochesterNew York 14611USA
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7
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Gharpure SJ, Fartade DJ, Gupta KS, Patel RK. Transposition of an acrylate moiety in TMSOTf-mediated reaction of alkynyl vinylogous carbonates gives heterocyclic dienes. Chem Commun (Camb) 2022; 58:9762-9765. [PMID: 35959727 DOI: 10.1039/d2cc03802a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
TMSOTf-mediated reaction of alkynyl vinylogous carbonates serendipitously gave 1,4-oxazepine and dihydropyran dienes via transposition of an ethyl acrylate moiety involving intramolecular cascade Prins-type cyclization/retro-oxa-Michael reaction/cycloisomerisation. The developed atom-economical protocol selectively provides an E double bond geometry. Dihydropyran dienes could be reduced diastereoselectively using Et3SiH/TMSOTf or could be transformed into polycyclic heterocycles by Heck reaction.
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Affiliation(s)
- Santosh J Gharpure
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India.
| | - Dipak J Fartade
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India.
| | - Krishna S Gupta
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India.
| | - Raj K Patel
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India.
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8
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Zhang Y, Chen Y, Song M, Tan B, Jiang Y, Yan C, Jiang Y, Hu X, Zhang C, Chen W, Xu J. Total Syntheses of Calyciphylline A-Type Alkaloids (-)-10-Deoxydaphnipaxianine A, (+)-Daphlongamine E and (+)-Calyciphylline R via Late-Stage Divinyl Carbinol Rearrangements. J Am Chem Soc 2022; 144:16042-16051. [PMID: 36007885 DOI: 10.1021/jacs.2c05957] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Among the famous Daphniphyllum alkaloids family, the calyciphylline A-type subfamily has triggered particular interest from the organic synthesis community in recent years. Here, we report divergent total syntheses of three calyciphylline A-type alkaloids, namely, (-)-10-deoxydaphnipaxianine A, (+)-daphlongamine E, and (+)-calyciphylline R. Our work highlights an efficient, divergent strategy via late-stage divinyl carbinol rearrangements, including an unprecedented oxidative Nazarov electrocyclization using an unfunctionalized tertiary divinyl carbinol and an unusual allylic alcohol rearrangement. A highly efficient "donor-acceptor" platinum catalyst was used for a critical nitrile hydration step. Moreover, the power of selective amide reductions has also been showcased by novel and classic tactics.
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Affiliation(s)
- Yan Zhang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuye Chen
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Manrong Song
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Bin Tan
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yujia Jiang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Chongyuan Yan
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuyang Jiang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xinyue Hu
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Chengqian Zhang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wenqing Chen
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jing Xu
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
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9
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Motiwala HF, Armaly AM, Cacioppo JG, Coombs TC, Koehn KRK, Norwood VM, Aubé J. HFIP in Organic Synthesis. Chem Rev 2022; 122:12544-12747. [PMID: 35848353 DOI: 10.1021/acs.chemrev.1c00749] [Citation(s) in RCA: 124] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) is a polar, strongly hydrogen bond-donating solvent that has found numerous uses in organic synthesis due to its ability to stabilize ionic species, transfer protons, and engage in a range of other intermolecular interactions. The use of this solvent has exponentially increased in the past decade and has become a solvent of choice in some areas, such as C-H functionalization chemistry. In this review, following a brief history of HFIP in organic synthesis and an overview of its physical properties, literature examples of organic reactions using HFIP as a solvent or an additive are presented, emphasizing the effect of solvent of each reaction.
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Affiliation(s)
- Hashim F Motiwala
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Ahlam M Armaly
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Jackson G Cacioppo
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Thomas C Coombs
- Department of Chemistry, University of North Carolina Wilmington, Wilmington, North Carolina 28403 United States
| | - Kimberly R K Koehn
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Verrill M Norwood
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Jeffrey Aubé
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
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10
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Wang Z, Yamazaki S, Mikata Y, Oba M, Takashima H, Morimoto T, Ogawa A. Intramolecular Diels-Alder Reactions of α-Bromostyrene-Functionalized Unsaturated Carboxamides. J Org Chem 2022; 87:11148-11164. [PMID: 35944162 DOI: 10.1021/acs.joc.2c01417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intramolecular cycloaddition reactions of α-bromostyrene-functionalized amides of monomethyl fumarate were investigated. The reaction of the amides with Et3N in toluene at 110 °C gave 1,4-dihydronaphthalenes. The 1,4-dihydronaphthalenes may be produced via the intramolecular Diels-Alder reaction, proton transfer, and dehydrobromination by a base, along with C═C bond isomerization by proton transfer. The reaction of amide derivatives with halogen on a benzene ring and alkali metal carbonates in toluene at 110 °C gave naphthalene derivatives directly. Dehydrogenation of various 1,4-dihydronaphthalenes with cesium or rubidium carbonate in toluene at 110 °C gave naphthalene derivatives. The retardation by TEMPO, acceleration by air for some substrates, and density functional theory calculations suggest a radical mechanism caused by intervention of molecular oxygen.
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Affiliation(s)
- Zhichao Wang
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Shoko Yamazaki
- Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan
| | - Yuji Mikata
- Laboratory for Molecular and Functional Design, Department of Engineering, Nara Women's University Nara 630-8506, Japan
| | - Miho Oba
- Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Hiroshi Takashima
- Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Tsumoru Morimoto
- Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Takayama, Ikoma, Nara 630-0192, Japan
| | - Akiya Ogawa
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Nakaku, Sakai, Osaka 599-8531, Japan
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11
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Alachouzos G, Schulte AM, Mondal A, Szymanski W, Feringa BL. Computational Design, Synthesis, and Photochemistry of Cy7-PPG, an Efficient NIR-Activated Photolabile Protecting Group for Therapeutic Applications. Angew Chem Int Ed Engl 2022; 61:e202201308. [PMID: 35181979 PMCID: PMC9311213 DOI: 10.1002/anie.202201308] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Indexed: 12/14/2022]
Abstract
Photolabile Protecting Groups (PPGs) are molecular tools used, for example, in photopharmacology for the activation of drugs with light, enabling spatiotemporal control over their potency. Yet, red-shifting of PPG activation wavelengths into the NIR range, which penetrates the deepest in tissue, has often yielded inefficient or insoluble molecules, hindering the use of PPGs in the clinic. To solve this problem, we report herein a novel concept in PPG design, by transforming clinically-applied NIR-dyes with suitable molecular orbital configurations into new NIR-PPGs using computational approaches. Using this method, we demonstrate how Cy7, a class of NIR dyes possessing ideal properties (NIR-absorption, high molecular absorptivity, excellent aqueous solubility) can be successfully converted into Cy7-PPG. We report a facile synthesis towards Cy7-PPG from accessible precursors and confirm its excellent properties as the most redshifted oxygen-independent NIR-PPG to date (λmax =746 nm).
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Affiliation(s)
- Georgios Alachouzos
- Centre for Systems Chemistry, Stratingh Institute for ChemistryFaculty for Science and EngineeringUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
| | - Albert M. Schulte
- Centre for Systems Chemistry, Stratingh Institute for ChemistryFaculty for Science and EngineeringUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
| | - Anirban Mondal
- Centre for Systems Chemistry, Stratingh Institute for ChemistryFaculty for Science and EngineeringUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
| | - Wiktor Szymanski
- Department of RadiologyMedical Imaging CenterUniversity Medical Center GroningenUniversity of GroningenHanzeplein 19713 GZGroningenThe Netherlands
| | - Ben L. Feringa
- Centre for Systems Chemistry, Stratingh Institute for ChemistryFaculty for Science and EngineeringUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
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12
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Alachouzos G, Schulte AM, Mondal A, Szymanski W, Feringa BL. Computational Design, Synthesis, and Photochemistry of Cy7PPG, an Efficient NIR‐Activated Photolabile Protecting Group for Therapeutic Applications. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Georgios Alachouzos
- Groningen University Faculty of Mathematics and Natural Sciences: Rijksuniversiteit Groningen Faculty of Science and Engineering Stratingh Institute for Chemistry NETHERLANDS
| | - Albert M. Schulte
- Groningen University Faculty of Mathematics and Natural Sciences: Rijksuniversiteit Groningen Faculty of Science and Engineering Stratingh Institute for Chemistry NETHERLANDS
| | - Anirban Mondal
- Groningen University Faculty of Mathematics and Natural Sciences: Rijksuniversiteit Groningen Faculty of Science and Engineering Stratingh Institute for Chemistry NETHERLANDS
| | - Wiktor Szymanski
- University Medical Centre Groningen: Universitair Medisch Centrum Groningen Department of Radiology NETHERLANDS
| | - Ben L Feringa
- University of Groningen Stratingh Institute for Chemistry, Faculty of Science and Engineering Nijenborgh 4 9747 AG Groningen NETHERLANDS
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13
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García-Pedrero O, Rodríguez F. Cationic cyclization reactions with alkyne terminating groups: a useful tool in biomimetic synthesis. Chem Commun (Camb) 2022; 58:1089-1099. [PMID: 34989726 DOI: 10.1039/d1cc05826f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclization reactions through cationic intermediates have become a highly valuable tool in organic synthesis. The use of alkynes as the terminating group in this type of cationic process offers wide synthetic possibilities because this group can serve as a precursor of different functionalities. This article shows relevant examples of cationic cyclization reactions with alkynes as terminating groups with the intention of demonstrating the potential of this type of process, particularly in the context of biomimetic synthesis of natural products.
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Affiliation(s)
- Olaya García-Pedrero
- Instituto Universitario de Química Organometálica "Enrique Moles", Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Oviedo, Julián Clavería, 8, Oviedo-33006, Spain.
| | - Félix Rodríguez
- Instituto Universitario de Química Organometálica "Enrique Moles", Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Oviedo, Julián Clavería, 8, Oviedo-33006, Spain.
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14
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Alachouzos G, Frontier AJ. Cyclization Strategies for the Concurrent Installation of Multiple Quaternary Stereogenic Centers. Isr J Chem 2021. [DOI: 10.1002/ijch.202100014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Georgios Alachouzos
- Stratingh Institute of Chemistry Rijksuniversiteit Groningen Nijenborgh 4 9747AG Groningen, The Netherlands
| | - Alison J. Frontier
- Department of Chemistry University of Rochester 414 Hutchison Hall, 100 Trustee Road Rochester New York 14627-0216 United States
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15
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Frontier AJ, Sinclair PP. Merging Strategy, Improvisation, and Conversation to Solve Problems in Target Synthesis. Acc Chem Res 2021; 54:1817-1829. [PMID: 33705115 DOI: 10.1021/acs.accounts.0c00804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Total synthesis has long been depicted as the quest to conquer the structures created by nature, requiring an unflinching, single-minded devotion to the task. The goal is achieved by chemists with grit, strength of will, and a competitive spirit. While there is some truth to this viewpoint, it does not fully capture the rich experiences gained in this research realm. In our lab, strategic planning, improvisation, and conversation have worked in concert to enable progress. This Account summarizes our efforts to synthesize four different bioactive targets: merrilactone A, rocaglamide, phomactin A, and tetrapetalone A. Certain missteps were integral to success in these synthetic projects. As such, we include the hiccups, and their roles in the evolution of the strategies, along with the results that aligned with our expectations.Two of these projects (merrilactone A and rocaglamide) culminated in the total synthesis of the targets. The challenges presented by merrilactone A spawned a new design strategy for pentannulation using Nazarov cyclization chemistry. This work demonstrated that Lewis acid catalysis is often a viable electrocyclization strategy in activated, polarized pentadienyl cation intermediates. We sought to apply the same logic to the rocaglamide target, but precursors we prepared did not behave according to plan. This situation pushed us to adapt our approach to match the innate reactivity of the substrate, resulting in an on-the-spot improvisation that was not only integral to the success of the project but also expanded our understanding of pentadienyl cation chemistry. In the other two projects (phomactin A and tetrapetalone A), we did not complete a total synthesis but did build the polycyclic core of the target. Even though the hetero [4 + 2] cycloaddition plan for assembling the macrocyclic oxadecalin ring system of phomactin A failed, the original experimental design still enabled us to solve the problem. Through a wholly unanticipated series of events, our focus on the oxadecalin ring system primed us for the discovery of a sequential iodoaldol/oxa-Michael sequence, using the original [4 + 2] building blocks. Then, the bridging ring present in phomactin A demanded we implement this sequence in a transannular fashion. Finally, our successful synthesis of the tetrapetalone core was enabled by consultations with others in the community. Each bond formation seemed to require different expertise, and in three separate instances (C-N cross-coupling, diastereoselective ring-closing metathesis, and oxidative dearomatization) synthetic challenges were overcome through conversation and collaboration.In our experience, the amount of creative power we summon during a target synthesis project correlates directly with the magnitude of the structural challenges we face. When reactivity surprises us, we analyze the problem anew, consult with colleagues, and improvise with the tools at hand. The inevitable misbehavior of a complex system is a strong motivating force, and one that has helped to shape our research program for nearly two decades.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
| | - Paul P. Sinclair
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
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Amemiya S, Okemoto S, Tsubouchi A, Saito A. Synthesis of α-(aminoethyl)-α,β-enones via alkyne aza-Prins cyclization and their synthetic application to pyrrolidines. Org Biomol Chem 2021; 19:2959-2967. [PMID: 33729258 DOI: 10.1039/d1ob00072a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We developed a synthetic method for α-(aminoethyl)-α,β-enones from aryl-substituted homopropargyl sulfonamides and aldehydes, representing the first synthesis of conjugated enones via alkyne aza-Prins cyclization. These products could be converted into pyrrolidines by a formal 5-endo-trig cyclization.
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Affiliation(s)
- Sho Amemiya
- Division of Applied Chemistry, Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
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Hernandez JJ, Frontier AJ. Synthesis of Spirocyclic Isoindolones Using an Alkynyl aza-Prins/Oxidative halo-Nazarov Cyclization Sequence. Org Lett 2021; 23:1782-1786. [PMID: 33591209 DOI: 10.1021/acs.orglett.1c00191] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In this report, we describe an alkynyl halo-aza-Prins cyclization of 3-hydroxyisoindolones to prepare aza-Prins products. These Prins adducts undergo oxidation at the 3-isoindolone position after activation of the amide by triflic anhydride and 2-chloropyridine to form a pentadienyl cation capable of undergoing a halo-Nazarov cyclization. Using this methodology, angular-fused N-heterocyclic small molecules with two new rings, two new carbon-carbon bonds, a vinyl halide, and an aza-tertiary stereocenter can be obtained in good yields.
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Affiliation(s)
- Jackson J Hernandez
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alison J Frontier
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
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Abstract
The defining feature of the Nazarov cyclization is a 4π-conrotatory electrocyclization, resulting in the stereospecific formation of functionalized cyclopentanones. The reaction provides access to structural motifs that are found in many natural products and drug targets. Harnessing the full potential of the Nazarov cyclization broadens its utility by enabling the development of new methodologies and synthetic strategies. To achieve these goals through efficient cyclization design, it is helpful to think of the reaction as a two-stage process. The first stage involves a 4π-electrocyclization leading to the formation of an allylic cation, and the second stage corresponds to the fate of this cationic intermediate. With a complete understanding of the discrete events that characterize the overall process, one can optimize reactivity and control the selectivity of the different Stage 2 pathways.In this Account, we describe the development of methods that render the Nazarov cyclization catalytic and chemoselective, focusing specifically on advances made in our lab between 2002 and 2015. The initial discovery made in our lab involved reactions of electronically asymmetric ("polarized") substrates, which cyclize efficiently in the catalytic regime using mild Lewis acidic reagents. These cyclizations also exhibit selective eliminative behavior, increasing their synthetic utility. Research directed toward catalytic asymmetric Nazarov cyclization led to the serendipitous discovery of a 4π-cyclization coupled to a well-behaved Wagner-Meerwein rearrangement, representing an underexplored Stage 2 process. With careful choice of promoter and loading, it is possible to access either the rearrangement or the elimination pathway. Additional experimental and computational studies provided an effective model for anticipating the migratory behavior of substiutents in the rearrangements. Problem-solving efforts prompted investigation of alternative methods for generating pentadienyl cation intermediates, including oxidation of allenol ethers and addition of nucleophiles to dienyl diketones. These Nazarov cyclization variants afford cyclopentenone products with vicinal stereogenic centers and a different arrangement of substituents around the ring. A nucleophilic addition/cyclization/elimination sequence can be executed enantioselectively using catalytic amounts of a nonracemic chiral tertiary amine.In summary, the discovery and development of several new variations on the Nazarov electrocyclization are described, along with synthetic applications. This work illustrates how strongly substitution patterns can impact the efficiency of the 4π-electrocyclization (Stage 1), allowing for mild Lewis acid catalysis. Over the course of these studies, we have also identified new ways to access the critical pentadienyl cation intermediates and demonstrated strategies that exploit and control the different cationic pathways available post-electrocyclization (Stage 2 processes). These advances in Nazarov chemistry were subsequently employed in the synthesis of natural product targets such as (±)-merrilactone A, (±)-rocaglamide, and (±)-enokipodin B.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jackson J. Hernandez
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Alachouzos G, Holt C, Frontier AJ. Stereochemical Relay through a Cationic Intermediate: Helical Preorganization Dictates Direction of Conrotation in the halo-Nazarov Cyclization. Org Lett 2020; 22:4010-4015. [PMID: 32352794 DOI: 10.1021/acs.orglett.0c01330] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A stereocontrolled halo-Prins/halo-Nazarov cyclization protocol is reported, where chiral information from a secondary alcohol is relayed through several intermediates yielding halocyclopentene products diastereoselectively. An enantiopure product is obtained when a nonracemic secondary alcohol is used. Experimental and computational studies are described, enabling the design and synthesis of systems that ionize and cyclize with >95% chirality transfer through a mechanism involving the creation and preservation of transient helical chirality in a pentadienyl cation intermediate. First, a diastereoselective alkynyl Prins cyclization is executed to synthesize a conformationally distorted dihydropyran intermediate with a curved backbone and high reactivity. This chiral precursor adopts a specific helical alignment early in the subsequent cationic ionization/halo-Nazarov cyclization process, dictating the direction of conrotation in the electrocyclization. Notably, despite the ablation of an sp3 stereogenic center during ionization, the low halo-Nazarov barrier enables efficient capture of a cationic intermediate with dynamic conformational chirality. The ionization and electrocyclization thus occur with "memory of chirality".
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Affiliation(s)
- Georgios Alachouzos
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Connor Holt
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Alison J Frontier
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
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Li XS, Han YP, Xu DT, Li M, Wei WX, Liang YM. Silver Trifluoromethanesulfonate-Catalyzed Annulation of Propargylic Alcohols with 3-Methyleneisoindolin-1-one. J Org Chem 2020; 85:2626-2634. [PMID: 31880453 DOI: 10.1021/acs.joc.9b02533] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A silver-catalyzed formal [3 + 3] annulation of 3-methyleneisoindolin-1-one with alkynol for the synthesis of 1,5-dihydroindolizin-3(2H)-one derivatives is disclosed. The protocol allows practical synthesis of N-heterocyclic scaffolds with a broad scope of functional groups and could be efficiently scaled up to gram scale, which incarnates a potential application of this methodology. In addition, a range of chlorine anion substitution of alkenes can be constructed by adjusting the structure of the alkynol substrates with the use of TMSCl.
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Affiliation(s)
- Xue-Song Li
- State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , P.R. China
| | - Ya-Ping Han
- School of Chemical Engineering and Technology , Hebei University of Technology , Tianjin 300130 , P.R. China
| | - Dan-Tong Xu
- State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , P.R. China
| | - Ming Li
- State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , P.R. China
| | - Wan-Xu Wei
- State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , P.R. China
| | - Yong-Min Liang
- State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , P.R. China
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Affiliation(s)
- Anton V. Yadykov
- N. D. Zelinsky Institute of Organic ChemistryRussian Academy of Sciences 47 Leninsky prosp., 119991 Moscow Russian Federation
| | - Valerii Z. Shirinian
- N. D. Zelinsky Institute of Organic ChemistryRussian Academy of Sciences 47 Leninsky prosp., 119991 Moscow Russian Federation
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Kotipalli T, Hou D. Synthesis of 3‐Bromoindenes from 4‐Alkynyl Alcohols/Sulfonamides and Aldehydes via Prins Cyclization, Ring‐Opening and Friedel‐Crafts Reactions. ASIAN J ORG CHEM 2019. [DOI: 10.1002/ajoc.201900292] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Trimurtulu Kotipalli
- Department of ChemistryNational Central University Jhong-Li City Taoyuan Taiwan 32001
| | - Duen‐Ren Hou
- Department of ChemistryNational Central University Jhong-Li City Taoyuan Taiwan 32001
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Markham JP, Wang B, Stevens ED, Burris SC, Deng Y. ortho
‐Alkylation of Pyridine
N
‐Oxides with Alkynes by Photocatalysis: Pyridine
N
‐Oxide as a Redox Auxiliary. Chemistry 2019; 25:6638-6644. [DOI: 10.1002/chem.201901065] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Jonathan P. Markham
- Chemistry DepartmentWestern Kentucky University 1906 College Heights Boulevard Bowling Green Kentucky 42101 USA
| | - Ban Wang
- Chemistry DepartmentWestern Kentucky University 1906 College Heights Boulevard Bowling Green Kentucky 42101 USA
| | - Edwin D. Stevens
- Chemistry DepartmentWestern Kentucky University 1906 College Heights Boulevard Bowling Green Kentucky 42101 USA
| | - Stuart C. Burris
- Chemistry DepartmentWestern Kentucky University 1906 College Heights Boulevard Bowling Green Kentucky 42101 USA
| | - Yongming Deng
- Chemistry DepartmentWestern Kentucky University 1906 College Heights Boulevard Bowling Green Kentucky 42101 USA
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Holt C, Alachouzos G, Frontier AJ. Leveraging the Halo-Nazarov Cyclization for the Chemodivergent Assembly of Functionalized Haloindenes and Indanones. J Am Chem Soc 2019; 141:5461-5469. [DOI: 10.1021/jacs.9b00198] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Connor Holt
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Georgios Alachouzos
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
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Li L, Zhu XQ, Zhang YQ, Bu HZ, Yuan P, Chen J, Su J, Deng X, Ye LW. Metal-free alkene carbooxygenation following tandem intramolecular alkoxylation/Claisen rearrangement: stereocontrolled access to bridged [4.2.1] lactones. Chem Sci 2019; 10:3123-3129. [PMID: 30996895 PMCID: PMC6429610 DOI: 10.1039/c9sc00079h] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 01/23/2019] [Indexed: 12/14/2022] Open
Abstract
Alkene carbooxygenation has attracted considerable attention over the past few decades as this approach provides an efficient access to various oxygen-containing molecules, especially the valuable O-heterocycles. However, examples of catalytic alkene carbooxygenation via a direct C-O cleavage are quite scarce, and the C-O cleavage in these cases is invariably initiated by transition metal-catalyzed oxidative addition. We report here a novel Brønsted acid-catalyzed intramolecular alkoxylation-initiated tandem sequence, which represents the first metal-free intramolecular alkoxylation/Claisen rearrangement. Significantly, an unprecedented Brønsted acid-catalyzed intramolecular alkene insertion into the C-O bond via a carbocation pathway was discovered. This method allows the stereocontrolled synthesis of valuable indole-fused bridged [4.2.1] lactones, providing ready access to biologically relevant scaffolds in a single synthetic step from an acyclic precursor. Moreover, such an asymmetric cascade cyclization has also been realized by employing a traceless chiral directing group. Control experiments favor the feasibility of a carbocation pathway for the process. In addition, biological tests showed that some of these newly synthesized indole-fused lactones exhibited their bioactivity as antitumor agents against different breast cancer cells, melanoma cells, and esophageal cancer cells.
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Affiliation(s)
- Long Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
| | - Xin-Qi Zhu
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
| | - Ying-Qi Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
| | - Hao-Zhen Bu
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
| | - Peng Yuan
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
| | - Jinyu Chen
- State Key Laboratory of Cellular Stress Biology , School of Life Sciences , Xiamen University , Xiamen , Fujian 361102 , China
| | - Jingyi Su
- State Key Laboratory of Cellular Stress Biology , School of Life Sciences , Xiamen University , Xiamen , Fujian 361102 , China
| | - Xianming Deng
- State Key Laboratory of Cellular Stress Biology , School of Life Sciences , Xiamen University , Xiamen , Fujian 361102 , China
| | - Long-Wu Ye
- State Key Laboratory of Physical Chemistry of Solid Surfaces , Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China .
- State Key Laboratory of Organometallic Chemistry , Shanghai Institute of Organic Chemistry , Chinese Academy of Sciences , Shanghai 200032 , China
- State Key Laboratory of Elemento-Organic Chemistry , Nankai University , Tianjin 300071 , China
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Alachouzos G, Frontier AJ. Cationic Cascade for Building Complex Polycyclic Molecules from Simple Precursors: Diastereoselective Installation of Three Contiguous Stereogenic Centers in a One-Pot Process. J Am Chem Soc 2018; 141:118-122. [DOI: 10.1021/jacs.8b11713] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Georgios Alachouzos
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
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Congmon J, Tius MA. Contiguous Quaternary Centers from a Au
I
‐Catalyzed Nazarov Cyclization. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800604] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jonathan Congmon
- Chemistry Department University of Hawaii at Manoa 2545 The Mall 96822 Honolulu HI USA
| | - Marcus A. Tius
- Chemistry Department University of Hawaii at Manoa 2545 The Mall 96822 Honolulu HI USA
- University of Hawaii Cancer Center 701 Ilalo Street 96813 Honolulu HI USA
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