Synthesis and Characterization of Ru(II)-NSHC Catalysts Bearing Thiamine Analogs in Water-Solvent Transfer Hydrogenation Catalysis

Abstract

Thiamine analogues with 3-methyl and 4-(2-hydroxyethyl) substituents on the backbone of thiazole ring, were used to synthesize monodentate Ru(II)-thiazolylidene complexes in a single step via transmetalation under mild conditions. These novel complexes catalyze the conversion of ketones and aldehydes to alcohols by transfer hydrogenation in a 5 : 2 HCO2H/NEt3 buffer in water. However, their efficiency was found to be much lower than the thiamine-derived bidentate Ru(II) complexes, which strongly indicates that the 'N-H' plays a crucial role in the reaction.