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Lu YN, Che C, Zhen G, Chang X, Dong XQ, Wang CJ. Visible-light-enabled stereoselective synthesis of functionalized cyclohexylamine derivatives via [4 + 2] cycloadditions. Chem Sci 2024; 15:6507-6514. [PMID: 38699278 PMCID: PMC11062095 DOI: 10.1039/d4sc00667d] [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: 01/28/2024] [Accepted: 03/26/2024] [Indexed: 05/05/2024] Open
Abstract
An unprecedented intermolecular [4 + 2] cycloaddition of benzocyclobutylamines with α-substituted vinylketones, enabled by photoredox catalysis, has been developed. The current method enables facile access to highly functionalized cyclohexylamine derivatives that were otherwise inaccessible, in moderate to good yields with excellent diastereoselectivities. This protocol has some excellent features, such as full atom economy, good functional-group compatibility, mild reaction conditions, and an overall redox-neutral process. Additionally, an asymmetric version of this cycloaddition was preliminarily investigated via the incorporation of a chiral phosphoric acid (CPA), and moderate to good enantioselectivity could be effectively realized with excellent diastereoselectivity. Synthetic applications were demonstrated via a scale-up experiment and elaborations to access amino alcohol and cyclobutene derivatives. Based on the results of control experiments, a reasonable reaction mechanism was proposed to elucidate the reaction pathway.
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Affiliation(s)
- Yi-Nan Lu
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
| | - Chao Che
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
| | - Guangjin Zhen
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
| | - Xin Chang
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
| | - Xiu-Qin Dong
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
| | - Chun-Jiang Wang
- College of Chemistry and Molecular Sciences, Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, Wuhan University Wuhan Hubei 430072 China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry Shanghai 230021 China
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2
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Sun Z, Ma W, Cao Y, Wei T, Mo X, Chow HY, Tan Y, Cheung CH, Liu J, Lee HK, Tse EC, Liu H, Li X. Superfast desulfurization for protein chemical synthesis and modification. Chem 2022. [DOI: 10.1016/j.chempr.2022.07.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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3
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Pruteanu E, Tappin NDC, Kulciţki V, Renaud P, Gîrbu V, Morarescu O, Dénès F. Forskolin Editing via Radical Iodo- and Hydroalkylation. SYNTHESIS-STUTTGART 2021. [DOI: 10.1055/s-0040-1706003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
AbstractThe modification of highly oxygenated forskolin as well as manoyl and epi-manoyl oxide, two less functionalized model substrates sharing the same polycyclic skeleton, via intermolecular carbon-centered radical addition to the vinyl moiety has been investigated. Highly regio- and reasonably stereoselective iodine atom transfer radical addition (ATRA) reactions were developed. Unprotected forskolin afforded an unexpected cyclic ether derivative. Protection of the 1,3-diol as an acetonide led the formation of the iodine ATRA product. Interestingly, by changing the mode of initiation of the radical process, in situ protection of the forskolin 1,3-diol moiety as a cyclic boronic ester took place during the iodine ATRA process without disruption of the radical chain process. This very mild radical-mediated in situ protection of 1,3-diol is expected to be of interest for a broad range of radical and non-radical transformations. Finally, by using our recently developed tert-butylcatechol-mediated hydroalkylation procedure, highly efficient preparation of forskolin derivatives bearing an extra ester or sulfone group was achieved.
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Affiliation(s)
- Elena Pruteanu
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern
- Institute of Chemistry MECR
| | - Nicholas D. C. Tappin
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern
| | | | - Philippe Renaud
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern
| | - Vladilena Gîrbu
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern
- Institute of Chemistry MECR
| | | | - Fabrice Dénès
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern
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4
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Zhang JW, Wang YR, Pan JH, He YH, Yu W, Han B. Deconstructive Oxygenation of Unstrained Cycloalkanamines. Angew Chem Int Ed Engl 2020; 59:3900-3904. [PMID: 31869508 DOI: 10.1002/anie.201914623] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/18/2019] [Indexed: 12/20/2022]
Abstract
A deconstructive oxygenation of unstrained primary cycloalkanamines has been developed for the first time using an auto-oxidative aromatization promoted C(sp3 )-C(sp3 ) bond cleavage strategy. This metal-free method involves the substitution reaction of cycloalkanamines with hydrazonyl chlorides and subsequent auto-oxidative annulation to in situ generate pre-aromatics, followed by N-radical-promoted ring-opening and further oxygenation by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and m-cholorperoxybenzoic acid (mCPBA). Consequently, a series of 1,2,4-triazole-containing acyclic carbonyl compounds were efficiently produced. This protocol features a one-pot operation, mild reaction conditions, high regioselectivity and ring-opening efficiency, broad substrate scope, and is compatible with alkaloids, osamines, and peptides, as well as steroids.
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Affiliation(s)
- Jian-Wu Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Yuan-Rui Wang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Jia-Hao Pan
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Yi-Heng He
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Wei Yu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Bing Han
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
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5
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Zhang J, Wang Y, Pan J, He Y, Yu W, Han B. Deconstructive Oxygenation of Unstrained Cycloalkanamines. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914623] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jian‐Wu Zhang
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
| | - Yuan‐Rui Wang
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
| | - Jia‐Hao Pan
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
| | - Yi‐Heng He
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
| | - Wei Yu
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
| | - Bing Han
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
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6
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Hu F, Wang L, Xu L, Li SS. Aromatization-driven deconstruction/refunctionalization of unstrained rings. Org Chem Front 2020. [DOI: 10.1039/d0qo00344a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Aromatization-driven ring-opening/functionalization of common unstrained rings has been developed with the in situ generation of pre-aromatic fused spiro heterocycles as the key step.
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Affiliation(s)
- Fangzhi Hu
- College of Chemistry and Pharmaceutical Sciences
- Qingdao Agricultural University
- Qingdao 266109
- China
| | - Liang Wang
- College of Chemistry and Pharmaceutical Sciences
- Qingdao Agricultural University
- Qingdao 266109
- China
- College of Chemistry and Molecular Engineering
| | - Lubin Xu
- College of Chemistry and Pharmaceutical Sciences
- Qingdao Agricultural University
- Qingdao 266109
- China
| | - Shuai-Shuai Li
- College of Chemistry and Pharmaceutical Sciences
- Qingdao Agricultural University
- Qingdao 266109
- China
- College of Chemistry and Molecular Engineering
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7
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Muratov K, Kuchuk E, Vellalath S, Afanasyev OI, Moskovets AP, Denisov G, Chusov D. Formal reductive addition of acetonitrile to aldehydes and ketones. Org Biomol Chem 2018; 16:7693-7701. [PMID: 30288533 DOI: 10.1039/c8ob01992d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
An efficient and highly productive rhodium-catalyzed method for the synthesis of nitriles employing aldehydes or ketones, methyl cyanoacetate, water and carbon monoxide as starting materials has been developed. Simple rhodium chloride without any ligands can be used. The fine tuning of the substrate can lead to the activity higher than 5000 TON.
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Affiliation(s)
- Karim Muratov
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
| | - Ekaterina Kuchuk
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
| | - Sreekumar Vellalath
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76798, USA
| | - Oleg I Afanasyev
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
| | - Alexei P Moskovets
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
| | - Gleb Denisov
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
| | - Denis Chusov
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia.
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8
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Soulard V, Villa G, Vollmar DP, Renaud P. Radical Deuteration with D 2O: Catalysis and Mechanistic Insights. J Am Chem Soc 2017; 140:155-158. [PMID: 29240406 DOI: 10.1021/jacs.7b12105] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Selective incorporation of deuterium atoms into molecules is of high interest for labeling purposes and for optimizing properties of drug candidates. A mild and environmentally benign method for the deuteration of alkyl iodides via radical pathway using D2O as source of deuterium has been developed. The reaction is initiated and mediated by triethylborane in the presence of dodecanethiol as a catalyst. This method is compatible with a wide range of functional groups and provides the monodeuterated products in good yields and with a high level of deuterium incorporation. It opens promising opportunities for the development of enantioselective radical reactions. Moreover, a revision of the mechanism of the deoxygenation reaction of xanthates using R3B and water (Wood deoxygenation) is presented.
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Affiliation(s)
- Valentin Soulard
- Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Giorgio Villa
- Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Denis Patrick Vollmar
- Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Philippe Renaud
- Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland
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9
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Povie G, Ford L, Pozzi D, Soulard V, Villa G, Renaud P. Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201604950] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Guillaume Povie
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Leigh Ford
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Davide Pozzi
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Valentin Soulard
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Giorgio Villa
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Philippe Renaud
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
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10
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Povie G, Ford L, Pozzi D, Soulard V, Villa G, Renaud P. Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions. Angew Chem Int Ed Engl 2016; 55:11221-5. [DOI: 10.1002/anie.201604950] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Guillaume Povie
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Leigh Ford
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Davide Pozzi
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Valentin Soulard
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Giorgio Villa
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
| | - Philippe Renaud
- Department of Chemistry and Biochemistry; University of Bern; Freiestrasse 3 3012 Bern Switzerland
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11
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Wang J, Zheng N. The Cleavage of a C-C Bond in Cyclobutylanilines by Visible-Light Photoredox Catalysis: Development of a [4+2] Annulation Method. Angew Chem Int Ed Engl 2015; 54:11424-7. [PMID: 26228259 PMCID: PMC4653064 DOI: 10.1002/anie.201504076] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Indexed: 11/11/2022]
Abstract
We report the first example of an intermolecular [4+2] annulation of cyclobutylanilines with alkynes enabled by visible-light photocatalysis. Monocyclic and bicyclic cyclobutylanilines successfully undergo the annulation with terminal and internal alkynes to generate a wide variety of amine-substituted cyclohexenes including new hydrindan and decalin derivatives with good to excellent diastereoselectivity. The reaction is overall redox neutral with perfect atom economy.
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Affiliation(s)
- Jiang Wang
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701 (USA) http://www.zhenggroup.org
| | - Nan Zheng
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701 (USA) http://www.zhenggroup.org.
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12
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Wang J, Zheng N. The Cleavage of a CC Bond in Cyclobutylanilines by Visible-Light Photoredox Catalysis: Development of a [4+2] Annulation Method. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504076] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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13
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Abstract
This review article focuses on state-of-the-art borohydride based radical reactions, also covering earlier work, kinetics and some DFT calculations with respect to the hydrogen transfer mechanism.
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Affiliation(s)
- Takuji Kawamoto
- Department of Chemistry
- Graduate School of Science
- Osaka Prefecture University
- Sakai, Japan
| | - Ilhyong Ryu
- Department of Chemistry
- Graduate School of Science
- Osaka Prefecture University
- Sakai, Japan
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14
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Povie G, Marzorati M, Bigler P, Renaud P. Role of equilibrium associations on the hydrogen atom transfer from the triethylborane-methanol complex. J Org Chem 2013; 78:1553-8. [PMID: 23330643 DOI: 10.1021/jo302576c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The triethylborane-methanol system used in radical deoxygenation and dehalogenation processes has been investigated. Unambiguous evidence for the formation of a complex between triethylborane and methanol is provided. It was shown that the complexation process is exothermic (ΔH° ≈ -7.6 kcal mol(-1)) while being entropically disfavored (ΔS° ≈ -24 cal mol(-1) K(-1)). This study demonstrates that only very small quantities of complex (1-2%) are present in most of the reported conditions used in dehalogenation and deoxygenation processes. Recalculating the rate constant for the hydrogen transfer to a secondary alkyl radical with this concentration suggests a value in the 10(6) M(-1) s(-1) range for the complex itself, indicating a much more important activation of the O-H bond than previously thought. The importance of solvent effects is also highlighted. The formation of a larger amount of complex by the addition of methanol is accompanied by its deactivation via hydrogen bonding. These observations open new opportunitites for the future preparation of more effective hydrogen atom donors involving borane complexes.
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Affiliation(s)
- Guillaume Povie
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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15
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Mackie ID, DiLabio GA. Ring-opening radical clock reactions: many density functionals have difficulty keeping time. Org Biomol Chem 2011; 9:3158-64. [DOI: 10.1039/c0ob01246g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Gansäuer A, Shi L, Otte M, Huth I, Rosales A, Sancho-Sanz I, Padial NM, Oltra JE. Hydrogen atom donors: recent developments. Top Curr Chem (Cham) 2011; 320:93-120. [PMID: 21452081 DOI: 10.1007/128_2011_124] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This review highlights recent developments in the field of hydrogen atom transfer (HAT) reagents that circumvent the disadvantages of classical group 14 reagents, such as Bu₃SnH. Special emphasis is laid on the lowering of bond dissociation energies (BDEs) of molecules that could, as yet, not be used as HAT reagents and on the use of organometallic HAT reagents.
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Affiliation(s)
- Andreas Gansäuer
- Kekulé Institut für Organische Chemie und Biochemie der Universität Bonn, Germany.
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17
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Abstract
The thermodynamic stability of carbon-centered radicals may be defined in quantitative terms using the hydrogen transfer reaction shown in . The stability values obtained in this way for substituted systems may be understood as the stabilizing or destabilizing influence of substituents on the neighboring radical center. This approach can be easily adapted to oxygen- or sulfur-centered radicals as expressed in eqn (b). [Formula: see text] The stability values obtained in this way do not only serve as a quantitative basis for the discussion of substituent effects, but also allow for quantitative estimates of reaction energies for hydrogen transfer reactions. These occur as key steps in a multitude of synthetically useful radical-chain processes in apolar solution, in enzyme-mediated non-chain processes in biological systems, and in the oxidative degradation of a variety of biomolecules. The review will highlight the usefulness of radical stability values for the rationalization of successful (and not so successful) synthetic radical reactions as well as the potential design of new radical reactions.
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Affiliation(s)
- Johnny Hioe
- Department of Chemistry, LMU München, Butenandtstrasse 5-13, D-81377 München, Germany
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18
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Povie G, Villa G, Ford L, Pozzi D, Schiesser CH, Renaud P. Role of catechol in the radical reduction of B-alkylcatecholboranes in presence of methanol. Chem Commun (Camb) 2010; 46:803-5. [DOI: 10.1039/b917004a] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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19
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Ueng SH, Solovyev A, Yuan X, Geib SJ, Fensterbank L, Lacôte E, Malacria M, Newcomb M, Walton JC, Curran DP. N-heterocyclic carbene boryl radicals: a new class of boron-centered radical. J Am Chem Soc 2009; 131:11256-62. [PMID: 19606860 DOI: 10.1021/ja904103x] [Citation(s) in RCA: 227] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reduction of xanthates by N-heterocyclic carbene boranes (NHC-boranes) has been suggested to occur by a radical chain mechanism involving heretofore unknown NHC-boryl radicals. In support of this suggestion, both the expected borane dithiocarbonate product and an unexpected borane xanthate product have now been isolated. These are the first NHC-boranes with boron-sulfur bonds, and their structures have been secured by spectroscopic and crystallographic means. The first rate constants for H-atom transfer from an NHC borane complex were determined by using the ring opening of a substituted cyclobutylcarbinyl radical as a clock reaction. The rate constant for reaction of the NHC-borane with a secondary alkyl radical at ambient temperature is 4 x 10(4) M(-1) s(-1), and the Arrhenius function displayed an entropic term (log A term) that was typical for a bimolecular reaction. The B-H bond dissociation energy of an NHC-borane complex has been estimated at 88 kcal/mol. The putative NHC-boryl radical in these transformations has been detected by EPR spectroscopy. Spectral analysis suggests that it is a pi-radical, analogous to the benzyl radical.
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Affiliation(s)
- Shau-Hua Ueng
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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Hopper DW, Crombie AL, Clemens JJ, Kwon S. Chapter 6.1: Six-Membered Ring Systems: Pyridine and Benzo Derivatives. PROGRESS IN HETEROCYCLIC CHEMISTRY 2009. [DOI: 10.1016/s0959-6380(09)70039-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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21
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Jin J, Newcomb M. Rate Constants for Hydrogen Atom Transfer Reactions from Bis(cyclopentadienyl)titanium(III) Chloride-Complexed Water and Methanol to an Alkyl Radical. J Org Chem 2008; 73:7901-5. [PMID: 18800812 DOI: 10.1021/jo801869r] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jing Jin
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607
| | - Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607
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