The Asymmetric Homogeneous Hydrogenation of Olefins with the Rhodium Complexes of (1S,2S)-1,2-Bis(diphenylphosphinamino)cyclohexane and (2S,3S)-2,3-Bis(diphenylphosphinamino)butane

The effect of triethylamine on asymmetric hydrogenation has been studied using the cationic rhodium complex of (1S,2S)-1,2-bis(diphenylphosphinamino)cyclohexane or (2S,3S)-2,3-bis(diphenylphosphinamino)butane as a catalyst. By the addition of triethylamine, higher optical yields are achieved in the hydrogenation of (Z)-α-acetamidocinnamic acid and itaconic acid and higher conversion rates are obtained in the hydrogenation of (E)-2-methylcinnamic acid, mesaconic acid, and citraconic acid. The specific effect of triethylamine on the substrates with a carboxyl group may be explained by the ionization of the carboxyl group, which coordinates the catalytic rhodium complex firmly.