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
The first highly enantioselective hydrogenation of simple indoles was developed with a Brønstedacid as an activator to form the iminium intermediate in situ, which was hydrogenated using Pd(OCOCF(3))(2)/(R)-H8-BINAP catalyst system with up to 96% ee. The present method provides an efficient route to enantioenriched 2-substituted and 2,3-disubstituted indolines.
Kinetic Resolution of 2-Substituted Indolines by <i>N</i>
-Sulfonylation using an Atropisomeric 4-DMAP-<i>N</i>
-oxide Organocatalyst
作者:James I. Murray、Nils J. Flodén、Adriano Bauer、Nico D. Fessner、Daniel L. Dunklemann、Opetoritse Bob-Egbe、Henry S. Rzepa、Thomas Bürgi、Jeffery Richardson、Alan C. Spivey
DOI:10.1002/anie.201700977
日期:2017.5.15
The first catalytic kinetic resolution by N‐sulfonylation is described. 2‐Substituted indolines are resolved (s=2.6–19) using an atropisomeric 4‐dimethylaminopyridine‐N‐oxide (4‐DMAP‐N‐oxide) organocatalyst. Use of 2‐isopropyl‐4‐nitrophenylsulfonyl chloride is critical to the stereodiscrimination and enables facile deprotection of the sulfonamide products with thioglycolic acid. A qualitative model
98% ee using a strong Brønsted acid as the activator. This methodology was applied in the facile synthesis of biologically active products containing a chiral indoline skeleton. The mechanism of Pd-catalyzed asymmetric hydrogenation was investigated as well. Isotope-labeling reactions and ESI-HRMS proved that an iminium salt formed by protonation of the C═C bond of indoles was the significant intermediate
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