Catalysis Today, Vol.247, 14-19, 2015
Unexpectedly fast catalytic transfer hydrogenation of aldehydes by formate in 2-propanol-water mixtures under mild conditions
Unsaturated aldehydes were efficiently reduced by transfer hydrogenation from sodium formate in water-2-propanol mixtures using a water-soluble Ru(II)-tertiary phosphine catalyst. The reaction yielded unsaturated alcohols with complete selectivity and without hydrogenation or isomerization of C=C bonds of the substrates. Very high reaction rate was observed in the transfer hydrogenation of cinnamaldehyde already at 30 degrees C with turnover frequency of 160 h(-1) and this increased to 3800 h(-1) at 70 degrees C. Consequently, the method is applicable to the synthesis of unsaturated alcohols in case of heat sensitive or highly volatile aldehydes, too. Based on multinuclear NMR investigations, trans-[RuH2(H2O)(mtppms)(3)] is suggested as the key catalytic species. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Unsaturated aldehyde;Transfer hydrogenation;Ruthenium-phosphine catalyst;Sodium formate;Water;2-Propanol