Asymmetric Friedel-Crafts Alkylation of Indoles with Trifluoromethyl Pyruvate Catalyzed by a Dinuclear Zinc Catalyst

J Org Chem. 2018 Feb 2;83(3):1160-1166. doi: 10.1021/acs.joc.7b02599. Epub 2018 Jan 16.

Abstract

A bimetallic cooperative catalysis model has been reported for the asymmetric Friedel-Crafts (F-C) alkylation of indoles with trifluoromethyl pyruvates using Trost's intramolecular dinuclear zinc complex as the catalyst. This dinuclear zinc catalyst was prepared in situ by reacting the chiral ligand (S,S)-L2b with 2 equiv of ZnEt2. A series of trifluoromethyl alcohol and indole-containing biological compounds were formed in moderate to good yields (up to 95%) with good enantioselectivity (up to 88% enantiomeric excess (ee)) in the presence of 10 mol % catalyst under mild conditions. A synergistic transition state model was proposed to explain the origin of the asymmetric induction.

Publication types

  • Research Support, Non-U.S. Gov't