Premium
Chiral Brønsted Acid from Chiral Phosphoric Acid Boron Complex and Water: Asymmetric Reduction of Indoles
Author(s) -
Yang Kai,
Lou Yixian,
Wang Chenglan,
Qi LiangWen,
Fang Tongchang,
Zhang Feng,
Xu Hetao,
Zhou Lu,
Li Wangyang,
Zhang Guan,
Yu Peiyuan,
Song Qiuling
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201913656
Subject(s) - brønsted–lowry acid–base theory , protonation , phosphoric acid , chemistry , boron , alkyl , hydride , catalysis , aryl , enantioselective synthesis , functional group , indole test , combinatorial chemistry , organic chemistry , ion , polymer , hydrogen
A new chiral Brønsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This “designer acid catalyst”, which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2‐aryl‐substituted N‐unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3‐protonation and hydride‐transfer processes. Besides, bulky C2‐alkyl‐substituted N‐unprotected indoles are also suitable for this system.