Asymmetric hydrogenation of 2,4-dioxo esters: Selective synthesis of 2-hydroxy-4-oxo esters and direct access to chiral 2-hydroxy-4-butyrolactones

2,4-Dioxoesters la-e are selectively converted into optically active 2-hydr oxy-4-oxoesters 2a-c by hydrogenation with chiral rhodium-aminophosphane-ph osphinite catalysts (82-88% ee) or ruthenium-bisphosphane catalysts (52-67% ee), Direct one-pot hydrogenation of 2,4-dioxoesters la-e to 2-hydroxy-4-b utyrolactones 4a-c proceeds in high yields; catalytic activities, chemo-, d ia-, and enantioselectivities are strongly dependant upon the nature of the substrate and the catalyst.