Enantioselective Alkynylation of Trifluoromethyl Ketones Catalyzed by Functionalized-Salen Ni Complexes

Abstract

Cooperative catalysis has emerged as a powerful strategy in catalytic asymmetric synthesis. As a part of our program aiming at asymmetric cooperative catalysts, we have developed a series of functionalized salen transition metal catalysts to facilitate challenging bimetallic reactions through the H-bond mediated self-assembly. Recently we also reported that the urea-functionalized-salen Co catalysts could provide an alternative bifunctional activation of an anionic nucleophile (by H-bond) and an aldehyde (by Lewis acid metal center). Herein we wish to report that novel functionalized-salen Ni complexes are highly efficient catalysts for the enantioselective direct alkynylation of trifluoromethyl ketones, affording enantioenriched propargyl alcohol products in high yields and enantioselectivities. The current methodology is operationally simple and allow for the use of substoichiometric amount of base. Ligand synthesis, catalyst/reaction optimization, substrate scope study results will be discussed in detail in the presentation.