Acceptorless dehydrogenative coupling of primary alcohols to esters by heterogeneous Pt catalysts

Supported platinum catalysts have been studied for the acceptor-free dehydrogenative coupling of primary alcohols to esters in the liquid phase under solvent-free conditions in N-2 at 180 degrees C. The activity depends on the support material, and Pt-loaded SnO2 (Pt/SnO2) gives the highest activity. Pt/SnO2 shows higher activity than various transition metals (Ir, Re, Ru, Rh, Pd, Ag, Co, Ni, Cu) loaded on SnO2. The Pt/SnO2 catalyst (1 mol%) selectively converted various primary alcohols to their corresponding esters in moderate to high isolated yield (53-91%). This is the first example of reusable heterogeneous catalysts for the acceptor-free dehydrogenative coupling of primary alcohols to esters under additive-free and solvent-free conditions. Mechanistic and infrared (IR) studies are also shown to discuss the reaction pathway and a possible role of the SnO2 support as Lewis acid sites that activate carbonyl groups of adsorbed aldehyde intermediates.