V. Beghetto et al., Synthesis of Chiraphos via asymmetric hydrogenation of 2,3-bis(diphenylphosphinoyl)buta-1,3-diene, CHEM COMMUN, (2), 2000, pp. 155-156
(S,S)-2,3-Bis(diphenylphosphinoyl)butane, an immediate precursor of (S,S)-C
HIRAPHOS, can be obtained with 70% de and 71% op via double asymmetric hydr
ogenation of 2,3-bis(diphenylphosphinoyl)buta-1,3-diene in the presence of
Ru-(S)-BINAP catalysts.