N-Pyrrolylphosphines as ligands for highly regioselective rhodium-catalyzed 1-butene hydroformylation: Effect of water on the reaction selectivity

Abstract

The hydroformylation of 1-butene catalyzed by Rh(acac)(CO)2 with an excess of N-pyrrolylphosphine ligands, L = P(NC4H4)3, PPh2(NC4H4) or PPh(NC4H4)2, was investigated under constant pressure of synthesis gas (4-10 bar, H2/CO = 1) and 2 bar of 1-butene at temperatures ranging from 50 to 80 °C. N-Pyrrolylphosphine ligands facilitated excellent selectivity towards aldehydes and regioselectivity towards linear aldehydes. The application of a higher temperature, the presence of a small amount of water, and a [L]/[Rh] ratio of ca. 13 resulted in the achievement of the highest n/iso values in a short time. A further increase in selectivity was achieved after the addition of water to the reaction mixture. The catalytic performance of the studied systems showed an increase in selectivity (n/iso) with the increase of the number of pyrrolyl groups in phosphine: (P(NC4H4)3 > PPh(NC4H4)2 > PPh2(NC4H4)) > PPh3.