Tin-catalyzed conversion of trioses to alkyl lactates in alcohol solution

Tin chlorides, SnCl2 and SnCl4·5H2O are excellent catalysts for the reactions of trioses, dihydroxyacetone and glyceraldehyde with alcohols (MeOH, EtOH and nBuOH) to give alkyl lactates, whose reaction mechanism involves the intermediary formation of pyruvic aldehyde followed by its esterification, which is distinctively promoted by tin halides.