Ruthenium-catalyzed Reduction of Carbonyl Compounds Using Formic Acid

Carbonyl compounds were hydrogenated to the corresponding alcohols in excellent yields using formic acid with a ruthenium complex at 125 °C for 3 h. 2-Propanone was reduced to 2-propanol by RuCl2(PPh3)3–HCOOH system in 94% yield with 98% selectivity. 3-Pentanone, cyclohexanone, acetophenone, and propiophenone were hydrogenated to the corresponding alcohols in 86, 78, 84, and 86% yields respectively. The ketone having the bulkier alkyl groups showed lower reactivity. The catalytic activity was found to decrease in the order RuCl2(PPh3)3, RuHCl(PPh3)3, RuHCl(CO)(PPh3)3, and RuH2(PPh3)4.