Synergistic Ligand Effect in Rhodium(I)-Catalyzed Regio-Controlled Propene Hydroformylation

Abstract

Propene (propylene) is the most important hydroformylation reactant on an industrial scale, representing approximately 75% of the global consumption of oxo chemicals. Both n-butanal and isobutanal, the products of propene hydroformylation, are valuable precursors, and thus controlling the regioselectivity in this reaction is of academic and industrial interest. In the Rh-catalyzed propene hydroformylation, regioselective reactions have been achieved by a modifying ligand. Although highly normal selective (n/iso > 50) ligands have been reported, iso-selective (n/iso < 1) ligands are limited and more importantly show a significantly reduced activity (TOF < 1000 h-1). Herein, we report a highly reactive and regio-controlled (n/iso = 1) propene hydroformylation enabled by Rh catalysis with a sterically bulky pi-acceptor phosphorus (bicyclic bridgehead phosphoramidite (briphos)) ligand. In addition, a briphos/PPh3 ligand combination results in a mixed-ligand Rh(I) complex that shows regioselectivity (n/iso = 1) and high reactivity (TOF = 22,700 h-1) and stability during propene hydroformylation.