Heterogeneous Catalytic Hydrogenation of Unprotected Indoles in Water: A Green Solution to a Long-Standing Challenge
作者:Aditya Kulkarni、Weihong Zhou、Béla Török
DOI:10.1021/ol2019899
日期:2011.10.7
An environmentally benign procedure for the hydrogenation of unprotected indoles is described. The hydrogenation reaction is catalyzed by Pt/C and activated by p-toluenesulfonic acid in water as a solvent. The efficacy of the method is illustrated by the hydrogenation of a variety of substituted indoles to their corresponding indolines which were obtained in excellent yields.
Enantiopure 1,2,3,3a,4,8b-hexahydrocyclopenta[b]indole, the starting material of indoline dyes, could be obtained from the diastereomeric salt with N-tosyl-(R)-phenylglycine in ethanol.
Highly Enantioselective Synthesis of Indolines: Asymmetric Hydrogenation at Ambient Temperature and Pressure with Cationic Ruthenium Diamine Catalysts
作者:Zhusheng Yang、Fei Chen、Yanmei He、Nianfa Yang、Qing-Hua Fan
DOI:10.1002/anie.201607890
日期:2016.10.24
asymmetric hydrogenation of 1H‐indoles and 3H‐indoles at ambient temperature and pressure, catalyzed by chiral phosphine‐free cationic ruthenium complexes, has been developed. Excellent enantio‐ and diastereoselectivities (up to >99 % ee, >20:1 d.r.) were obtained for a wide range of indolederivatives, including unprotected 2‐substituted and 2,3‐disubstituted 1H‐indoles, as well as 2‐alkyl‐ and 2‐aryl‐substituted
Quite a pair: The first organocatalytic directasymmetric reduction of unprotected 1H‐indoles to chiral indolines has been developed. The reaction proceeds through the generation of electrophilic indolenium ions by a Brønsted acid, and then chiral Lewisbase (1) mediated enantioselective hydride transfer with HSiCl3. A variety of chiral indolines were obtained with moderate to excellent enantioselectivity
Asymmetric Transfer Hydrogenation of N-Unprotected Indoles with Ammonia Borane
作者:Weiwei Zhao、Zijia Zhang、Xiangqing Feng、Jing Yang、Haifeng Du
DOI:10.1021/acs.orglett.0c01930
日期:2020.8.7
A metal-free asymmetric transfer hydrogenation of unprotected indoles was successfully realized using a catalyst derived from HB(C6F5)2 and (S)-tert-butylsulfinamide with ammonia borane as a hydrogen source. A variety of indolines were achieved in 40–78% yields with up to 90% ee.
使用衍生自HB(C 6 F 5)2和(S)-叔丁基亚磺酰胺的氨硼烷作为氢源,成功实现了未保护的吲哚的无金属不对称转移氢化。各种二氢吲哚的收率为40-78%,ee高达90%。