Highly Enantioselective Synthesis of Indazoles with a C3-Quaternary Chiral Center Using CuH Catalysis
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Submitted version
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Author(s)
Ye, Yuxuan
Kevlishvili, Illia
Feng, Sheng
Liu, Peng
Buchwald, Stephen Leffler
Date Issued
2020
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Version
Original manuscript
Abstract
Copyright © 2020 American Chemical Society. C3-substituted 1H-indazoles are useful and important substructures in many pharmaceuticals. Methods for direct C3-functionalization of indazoles are relatively rare, compared to reactions developed for the more nucleophilic N1 and N2 positions. Herein, we report a highly C3-selective allylation reaction of 1H-N-(benzoyloxy)indazoles using CuH catalysis. A variety of C3-allyl 1H-indazoles with quaternary stereocenters were efficiently prepared with high levels of enantioselectivity. Density functional theory (DFT) calculations were performed to explain the reactivity differences between indazole and indole electrophiles, the latter of which was used in our previously reported method. The calculations suggest that the indazole allylation reaction proceeds through an enantioselectivity-determining six-membered Zimmerman-Traxler-type transition state, rather than an oxidative addition/reductive elimination sequence, as we proposed in the case of indole alkylation. The enantioselectivity of the reaction is governed by both ligand-substrate steric interactions and steric repulsions involving the pseudoaxial substituent in the six-membered allylation transition state.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/JACS.0C04286
