Phase transfer-catalysed transfer hydrogenation of ketones using iron carbonyls as catalysts

Abstract

Transfer hydrogenation of ketones to alcohols using iron carbonyls as catalysts in liquid-liquid phase occurs in the presence of phase transfer catalysts (PTC). Based on the percentage yield of the products, the efficiencies of the phase transfer agent, iron carbonyls and the donors are compared. Benzyltriethylammonium chloride and 18-crown-6 are equally effective and better than tricaprylmethylammonium chloride (Aliquat® 336). Among the three iron carbonyls the order of efficiency is Fe3(CO)12 > Fe2(CO)9 > Fe(CO)5. 1-Phenylethanol is a better donor than isopropanol. The relative ease of reducibility of various ketones increases with increasing reduction potential. The stereochemistry of reduction of 4-t-butylcyclohexanone is discussed.