J. Bakos et al., CHIRAL SULFONATED PHOSPHINES - RHODIUM(I)-CATALYZED ASYMMETRIC HYDROGENOLYSIS OF EPOXIDES, Journal of molecular catalysis. A, Chemical, 116(1-2), 1997, pp. 85-97
Rhodium(I) complexes of sulfonated (-)-(2S,4S)-2,4-bis(diphenylphosphi
no)pentane ((S,S)-(BDPP)) are effective as catalyst for asymmetric hyd
rogenolysis of sodium cis-epoxysuccinate to sodium hydroxysuccinate in
aqueous-organic two phase solvent system or in aqueous solution. It h
as been shown by deuterium labelling studies that both hydrogen and wa
ter participate in the aqueous hydrogenolysis as reactants and the rea
ction proceeds via the direct C-O bond cleavage of the epoxy group. Hi
gh pressure NMR studies show the presence of rhodaoxetane-BDPP complex
es as catalytic intermediates, which an formed by the oxidative additi
on of the epoxide to unsaturated Rh(I) species. Accordingly, a reactio
n mechanism has been proposed for the aqueous catalytic process. The u
se of a racemic substrate, sodium trans-phenylglycidate with the aqueo
us Rh-sulfonated (S,S)-BDPP system results in the kinetic resolution o
f the (2S,3R)-epoxide enantiomer. Thus, asymmetric aqueous catalytic h
ydrogenolysis could be a useful synthetic approach not only to chiral
alpha-hydroxycarboxylic acid derivatives but also to chiral trans-subs
tituted epoxides.