Asymmetric trifluoromethylation of aromatic aldehydes by cooperative catalysis with (IPr)CuF and quinidine-derived quaternary ammonium salt

A general enantioselective trifluoromethylation of aldehydes has been developed using (IPr)CuF and quinidine-derived quaternary ammonium salt as the cooperative catalyst. Thus, a wide range of aromatic aldehydes have been converted to the corresponding products in up to 92% yield and 81% ee at 2 mol% of catalyst loading. The greatly enhanced activity and enantioselectivity result from the initiative generation of active [(IPr)CuCF₃] as well as additional coordination activation of other copper species.