Catalytic Enantioselective Allylboration and Related Reactions of Isatins Promoted by Chiral BINOLs: Scope and Mechanistic Studies - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Journal of Organic Chemistry Année : 2023

Catalytic Enantioselective Allylboration and Related Reactions of Isatins Promoted by Chiral BINOLs: Scope and Mechanistic Studies

Résumé

An improvement in the catalytic enantioselective allylboration of isatins with 2-allyl-1,3,2-dioxaborolane in the presence of chiral BINOL derivatives is reported, offering an efficient one-step access to enantioenriched N-unprotected 3-allyl-3-hydroxy-2-oxindoles. This catalytic process is also effective for the crotylboration reaction with enantiomeric ratios (er) up to 97:3, as well as for the asymmetric synthesis of homopropargylic alcohols via an allenyl addition to indoline-2,3-diones. Origins of the high enantioselectivity in chiral BINOL-catalyzed allylboration of isatins were examined by DFT calculations. A hypothetical scenario suggested a crucial internal hydrogen bonding between the amide group (C═O···H-O) and the ethylene hydroxyl of the transient chiral mixed boronate ester, generating a rigid and stabilized system that favors the addition of the allylboron species to the Re face of the ketone function. The key role of the alcohol additive (t-BuOH or t-AmOH) in the enantioselective allylboration reaction of isatins has also been shown on the basis of a kinetics study and computational calculations by favoring the transesterification of the 2-allyl-1,3,2-dioxaborolane with BINOL via proton transfer processes.

Domaines

Chimie
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Dates et versions

hal-03971612 , version 1 (12-10-2023)

Identifiants

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Julien Braire, Aurélie Macé, Rania Zaier, Marie Cordier, Joëlle Vidal, et al.. Catalytic Enantioselective Allylboration and Related Reactions of Isatins Promoted by Chiral BINOLs: Scope and Mechanistic Studies. Journal of Organic Chemistry, 2023, 88 (3), pp.1469-1492. ⟨10.1021/acs.joc.2c02476⟩. ⟨hal-03971612⟩
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