Solvent Effect in the Reduction of α-Keto Esters by Aqueous Titanium Trichloride

Article abstract of DOI:10.1021/jo00232a008

In the reduction of 1 by Ti(III) ion the dimeric 3 or monomeric 4 reduction products could be made to predominate by the choice of the solvent.It is found that (a) dimerization, via coupling of two radicals 2, increases with increasing simultaneously the dielectric constant and the hydrogen ion concentration of the reaction medium and (b) alcohol formation, which occurs via electron transfer between radical species having different redox potentials, increases with decreasing the hydrogen ion concentration of the medium.Under appropriate reaction conditions, the dimerization process is partially stereoselective.Reaction mechanisms are proposed which account for the ratio of both dimer / alcohol and meso / dl under different experimental conditions.