Rhodium complexes of (R)-Me-CATPHOS and (R)-(S)-JOSIPHOS: highly enantioselective catalysts for the asymmetric hydrogenation of (E)- and (Z)-β-aryl-β-(enamido)phosphonates
摘要:
Rhodium complexes of (R)-Me-CATPHOS and (R)-(S)-JOSIPHOS form a complementary pair of catalysts for the highly efficient asymmetric hydrogenation of a selection of (E)- and (Z)-beta-aryl-beta-(enamido)phosphonates, respectively, in the majority of cases giving excellent yields and ee's in excess of 99%: the highest to be reported for this Class Of substrate. (C) 2009 Elsevier Ltd. All rights reserved.
Newly developed ClickFerrophos II ligands were applied in the hydrogenation of alpha,beta-unsaturated phosphonates. The use of a rhodium/ClickFerrophos II catalyst was examined in the hydrogenation of fimctionalized alpha,beta-unsaturated phosphonates and was revealed to be effective for beta-alkyl-beta-aryl or beta-dialkyl phosphonates, (Z)-beta-enolester phosphonates, and alpha-phenylethenyl phosphonates, producing the corresponding chiral phosphonates in good yields with high enantioselectivities (up to 96% ee).