Tin(IV) ethoxide-catalysed hydride transfer from alcohols to carbonyl compounds

In aprotic, apolar solvents tin(IV) ethoxide has been proved to be an efficient catalyst for the selective hydride transfer from alcohols to carbonyl compounds. Primary, secondary, and benzyl alcohols have shown hydride-donating ability, and this ability decreases in the order benzyl secondary >primary. The mechanism of hydride transfer from 1-phenylethanol to cyclohexanone has been investigated. Catalysis is inferred to proceed in the following order: (a) alcoholysis of SnIV ethoxide to form a mixed metal alkoxide, (b) co-ordination of the acceptor to the metal, (c) direct hydride transfer from the alkoxide moiety to the co-ordinated carbonyl compound and loss of the active catalyst. The kinetic isotope effect measurements and other data suggest that step (c) is the rate-determining step of the reaction.