Asymmetric hydrogenation reactions mediated by a new class of bicyclic bisphosphinites

The bicyclic alcohol (-)-4 was prepared from (-)-bicyclo[3.2.0]hept-2-en-6-one (-)-1 in 50% yield. The diol (-)-4 was coupled to selected chlorophosphines 6-12 to produce a series of bisphosphinites 13-19 in 89-95% yield. From these bisphosphinites were prepared the rhodium complexes 20-26 which were characterised by P-31 NMR and used in situ for the asymmetric hydrogenation of alpha-enamides 27-29. Complexes 21, 23-25 proved to be the superior catalysts for the production of (R)-N-acetylphenylalanine (91, 84, 90 and 87.5% ee) from 27 and (S)-N-acetylalanine methyl ester (70, 72, 68 and 71% ee) from 28. (C) 1999 Elsevier Science Ltd. All rights reserved.