Asymmetric synthesis by chiral ruthenium complexes : III. Regioselectivity and asymmetric induction in catalytic hydrogenation of α,β-unsaturated dicarboxylic acids

Abstract

The homogeneous catalytic hydrogenation of citraconic and mesaconic acids in the presence of H 4Ru 4(CO) 8[(—)-DIOP] 2 gives, in addition to (—)( S)-methylsuccinic acid, a mixture of λ-lactones in ratios which depend on the substrate and the reaction temperature. An exceptionally high regioselectivity is obtained in the hydrogenation at 120°C of the more hindered carboxyl group of mesaconic acid.