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H. Yamashita, B. L. Roan, T. Sakakura, and M. Tanaka
[J. Mol. Catal., Vol.81, pp.255-265, 1993]
In the hydroformylation of ethyl acrylate, Rh(acac)(CO)_{2}-P(O-p-XC_{6}H_{4})_{3} (X=H, Me, Cl) catalyst systems showed high activities under the conditions, 40°C and 1 atm of CO-H_{2} (1:1), to give β-formylpropionate as the main product (eq.1). Rh(acac)(CO)_{2}-PR_{3} (R=Ph, Me) systems were almost inactive. When P(O-i-Pr)_{3} was used as the ligand, hydrogenation of the acrylate proceeded exclusively. The catalyst with P(OMe)_{3} or P(OCH_{2})_{3}CEt mainly afforded the α-formylated product, although its activity was much lower. Higher molar ratios of P/Rh up to about five, as well as higher catalyst concentration, were favorable for β-formylation in the Rh(acac)(CO)_{2}-P(OPh)_{3} system. Raising the temperature promoted hydrogenation with suppression of α-formylation. Increasing the pressure of CO-H_{2} caused selective formation of α-formylpropionate.
