Asymmetric hydrogenation of 3,5-Dioxoesters catalyzed by Ru-binap complex: A short step asymmetric synthesis of 6-substituted 5,6-dihydro-2-pyrones

Asymmetric hydrogenation of 3,5-dioxoesters 1a-c using Ru2(Cl4((R) or (S)-binap)2(NEt3) as the catalyst gave anti 3,5-dihydroxyesters 2, which were then converted into unsaturated lactones 5a-c (70-80% e.e.). It was revealed that the Ru-binap catalyzed hydrogenation of 1a-b proceeds mainly via the β-diketone mode. A convenient asymmetric synthesis of hydroxylactone 3c and unsaturated lactone 5c was presented.