Heterogeneous enantioselective hydrogenation of 2-pyrones over cinchona-modified palladium

Abstract

Asymmetric hydrogenation of 4-alkoxy and 4-methyl derivatives of 2-pyrones to the corresponding dihydro- or tetrahydropyrones over cinchona-modified Pd/TiO2 is fast under ambient conditions and affords good yields and high ee. cis-Tetrahydropyrones are obtained with 98–99% de. The ee can be further increased by kinetic resolution.