Dynamic kinetic resolution of benzoins by lipase-metal combo catalysis.

The synthesis of some noncommercial racemic 1,2-diaryl-2-hydroxyethanones (benzoins) is described, optimizing the previously reported methodologies. In a further step, the kinetic resolution of these substrates is reported, obtaining conversions of around 50% and ee(p) higher than 99% in very short reaction times. As enzymatic catalyst, after screening of several enzymes, the lipase TL (from Pseudomonas stutzeri) was the most efficient, working in an organic solvent with a very low log P value, such as THF. Finally, the dynamic-kinetic resolution of different benzoins using a lipase-ruthenium-catalyzed transesterification in organic solvents is described for the first time, obtaining conversions up to 90% maintaining the excellent enantioselectivity in all cases.