Tunable Bromomagnesium Thiolate Tishchenko Reaction Catalysts: Intermolecular Aid ehyde-Trifluoromethylketone Coupling

摘要

The Tishchenko reaction (discovered by Claisen in 1887) is the disproportionation of two aldehyde molecules to furnish an ester product (Scheme 1). Aluminum alkoxides and boric acid, were the first classes of synthetically relevant homogeneous catalysts for this reaction, these were then followed by a range of transition-metal complexes of low to high catalytic activity but often limited practical utility. More recently, lanthanide, actinide, and calcium complexes capable of promoting aldehyde dimerization with excellent activity have been reported. A generalized mechanistic outline of the process is given in Scheme 1: reaction of the transition-metal complex 1 with the aldehyde generates the metal alkoxide 2, which acts as the hydride-transfer agent in a metal-mediated redox process (i.e. 3) leading to ester 4.