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 HCO 2 H/NEt 3 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.