Branched-Selective Hydroformylation of Nonactivated Olefins Using an N-Triphos/Rh Catalyst

We report a catalytic system comprised of nitrogen-centered di- or triphosphine ligands in conjunction with rhodium that is capable of delivering branched aldehydes from terminal olefin substrates which commonly give more linear aldehydes than branched. The incorporation of an apical nitrogen atom into the ligand backbone dramatically improves the reaction rate. Mechanistic and labeling studies suggest the unusual selectivity is due to the irreversible trapping of the Rh–alkyl species along the branched pathway, in comparison to the more reversible linear pathway. A precatalytic equilibrium mixture of rhodium species was observed by high-pressure in situ NMR spectroscopy, suggesting this equilibrium is the catalytic resting state.