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Byun S, Hwang MU, Wise HR, Bay AV, Cheong PHY, Scheidt KA. Light-Driven Enantioselective Carbene-Catalyzed Radical-Radical Coupling. Angew Chem Int Ed Engl 2023; 62:e202312829. [PMID: 37845183 PMCID: PMC10841513 DOI: 10.1002/anie.202312829] [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: 08/31/2023] [Revised: 10/13/2023] [Accepted: 10/13/2023] [Indexed: 10/18/2023]
Abstract
An enantioselective carbene-catalyzed radical-radical coupling of acyl imidazoles and racemic Hantzsch esters is disclosed. This method involves the coupling of an N-heterocyclic carbene-derived ketyl radical and a secondary sp3 -carbon radical and allows access to chiral α-aryl aliphatic ketones in moderate-to-good yields and enantioselectivities without any competitive epimerization. The utility of this protocol is highlighted by the late-stage functionalization of various pharmaceutical compounds and is further demonstrated by the transformation of the enantioenriched products to biologically relevant molecules. Computational investigations reveal the N-heterocyclic carbene controls the double-facial selectivity of the ketyl radical and the alkyl radicals, respectively.
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Affiliation(s)
- Seunghwan Byun
- Department of Chemistry, Northwestern University Silverman Hall, Evanston, Illinois 60208 (USA)
| | - Meemie U. Hwang
- Department of Chemistry, Northwestern University Silverman Hall, Evanston, Illinois 60208 (USA)
| | - Henry R. Wise
- Department of Chemistry, Oregon State University 153 Gilbert Hall, Corvallis, Oregon 97331 (USA)
| | - Anna V. Bay
- Department of Chemistry, Northwestern University Silverman Hall, Evanston, Illinois 60208 (USA)
| | - Paul H.-Y. Cheong
- Department of Chemistry, Oregon State University 153 Gilbert Hall, Corvallis, Oregon 97331 (USA)
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Lam CC, Goodman JM. Reaction dynamics as the missing puzzle piece: the origin of selectivity in oxazaborolidinium ion-catalysed reactions. Chem Sci 2023; 14:12355-12365. [PMID: 37969604 PMCID: PMC10631253 DOI: 10.1039/d3sc03009a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 10/18/2023] [Indexed: 11/17/2023] Open
Abstract
The selectivity in a group of oxazaborolidinium ion-catalysed reactions between aldehyde and diazo compounds cannot be explained using transition state theory. VRAI-selectivity, developed to predict the outcome of dynamically controlled reactions, can account for both the chemo- and the stereo-selectivity in these reactions, which are controlled by reaction dynamics. Subtle modifications to the substrate or catalyst substituents alter the potential energy surface, leading to changes in predominant reaction pathways and altering the barriers to the major product when reaction dynamics are considered. In addition, this study suggests an explanation for the mysterious inversion of enantioselectivity resulting from the inclusion of an orthoiPrO group in the catalyst.
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Affiliation(s)
- Ching Ching Lam
- Yusuf Hamied Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Jonathan M Goodman
- Yusuf Hamied Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
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Wang ZS, Bennett SH, Kicin B, Jing C, Pradeilles JA, Thai K, Smith JR, Bacoş PD, Fasano V, Saunders CM, Aggarwal VK. De Novo Synthesis of Dihydrobenzofurans and Indolines and Its Application to a Modular, Asymmetric Synthesis of Beraprost. J Am Chem Soc 2023. [PMID: 37326516 DOI: 10.1021/jacs.3c04582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Dihydrobenzofurans and indolines are important constituents of pharmaceuticals. Herein, we describe a novel strategy for their construction in which the aromatic ring is created de novo through an inverse-electron demand Diels-Alder reaction and cheletropic extrusion sequence of a 2-halothiophene-1,1-dioxide with an enol ether/enamide, followed by aromatization. Unusually, the aromatization process proved to be highly challenging, but it was discovered that treatment of the halocyclohexadienes with a base effected an α-elimination-aromatization reaction. Mechanistic investigation of this step using deuterium-labeling studies indicated the intermediacy of a carbene which undergoes a 1,2-hydrogen shift and subsequent aromatization. The methodology was applied to a modular and stereoselective total synthesis of the antiplatelet drug beraprost in only 8 steps from a key enal-lactone. This lactone provided the core of beraprost to which both its sidechains could be appended through a 1,4-conjugate addition process (lower ω-sidechain), followed by de novo construction of beraprost's dihydrobenzofuran (upper α-sidechain) using our newly developed methodology. Additionally, we have demonstrated the breadth of our newly established protocol in the synthesis of functionalized indolines, which occurred with high levels of regiocontrol. According to density-functional theory (DFT) calculations, the high selectivity originates from attractive London dispersion interactions in the TS of the Diels-Alder reaction.
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Affiliation(s)
- Ze-Shu Wang
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Steven H Bennett
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Bilal Kicin
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Changcheng Jing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Johan A Pradeilles
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Karen Thai
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - James R Smith
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - P David Bacoş
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Valerio Fasano
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Carla M Saunders
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Varinder K Aggarwal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
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Tavakoli A, Dudley GB. Synthesis of Coprinol and Several Alcyopterosin Sesquiterpenes by Regioselective [2 + 2 + 2] Alkyne Cyclotrimerization. J Org Chem 2022; 87:14909-14914. [PMID: 36215202 DOI: 10.1021/acs.joc.2c01741] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Alkyne [2 + 2 + 2] cyclotrimerization is a strategically attractive but tactically challenging approach to the synthesis of highly substituted benzene rings. Here, a bimolecular regioselective cyclotrimerization is applied to the total synthesis of the natural product coprinol and several related alcyopterosins from the illudalane family of sesquiterpenes. The synthesis of coprinol from dimedone was completed in six steps and a 57% overall yield. Alternative functional group manipulations lead to alcyopterosins A, B, and O and two additional congeners, all within six steps.
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Affiliation(s)
- Amir Tavakoli
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26505, United States
| | - Gregory B Dudley
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26505, United States
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