2,4-Dioxoesters 1a–c are selectively converted into optically active 2-hydroxy-4-oxoesters 2a–c by hydrogenation with chiral rhodium-aminophosphane-phosphinite catalysts (82–88% ee) or ruthenium-bisphosphane catalysts (52–67% ee). Direct one-pot hydrogenation of 2,4-dioxoesters 1a–c to 2-hydroxy-4-butyrolactones 4a–c proceeds in high yields; catalytic activities, chemo-, dia-, and enantioselectivities
The hydrogenation of ethyl 2,4-dioxovalerate in the presence of chiral rhodium or ruthenium catalysts provides direct access to 2-hydroxy-4-methyltetrahydrofuran-2-one 4 with syn:anti ratios of up to 84:16 and with up to 98% and 94% e.e. in the syn and anti form, respectively. (C) 1998 Elsevier Science Ltd. All rights reserved.