A Bimetallic Titanium Catalyst for the Enantioselective Cyanation of Aldehydes Based on Cooperative Catalysis

Joined at the hip: By linking two salen ligands together with a strap of appropriate size and shape, the effectiveness of a bimetallic titanium(salen) complex as a catalyst for asymmetric cyanohydrin synthesis can be increased by up to two orders of magnitude. The optimal catalyst is active at a catalyst loading as low as 0.0005 mol % and will accept both trimethylsilyl cyanide and sodium cyanide/acetic anhydride as the cyanide source (see scheme).