无保护基团转化是原子经济有机合成中一个具有挑战性和重要的问题。η(6)-芳烃/N-Me-磺酰二胺-Ru(II)-BF4 配合物催化2-取代的未保护吲哚在弱酸性六氟异丙醇中的不对称氢化得到具有高达>99% ee 的旋光二氢吲哚化合物。在温和的反应介质下,吲哚上的卤素原子和合成上重要的保护基团(例如甲硅烷基醚、缩醛、苄基醚和酯)得以保留,这有利于进一步合成复杂的二氢吲哚分子。
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%。
Brønsted-Acid-Promoted Rh-Catalyzed Asymmetric Hydrogenation of N-Unprotected Indoles: A Cocatalysis of Transition Metal and Anion Binding
作者:Jialin Wen、Xiangru Fan、Renchang Tan、Hui-Chun Chien、Qinghai Zhou、Lung Wa Chung、Xumu Zhang
DOI:10.1021/acs.orglett.8b00312
日期:2018.4.20
catalysis enables an efficient method to synthesize chiral indolines via hydrogenation of indoles. Catalyzed by a rhodium/ZhaoPhos complex, asymmetric hydrogenation of unprotected indoles is performed smoothly with excellent enantioselectivities (up to 99% ee, up to 400 TON). Brønsted acid HCl activates indoles to form iminiumionintermediates. Mechanistic studies support the assumption that anion binding
Kinetic Resolutions of Indolines by a Nonenzymatic Acylation Catalyst
作者:Forrest O. Arp、Gregory C. Fu
DOI:10.1021/ja0657859
日期:2006.11.1
The first method for the kinetic resolution of indolines through catalytic N-acylation is described. To improve the selectivity factor, new planar-chiral PPY-derived catalysts were synthesized, wherein the chiral environment was systematically modified. This work provides a rare example of a nonenzyme-based acylation catalyst for the kinetic resolution of amines.