Selective Decarbonylation of Fatty Acid Esters to Linear α-Olefins
John, A.; Dereli, B.; Ortuño, M. A.; Johnson, H. E.; Hillmyer, M. A.;
Cramer, C. J.; Tolman, W. B.
Organometallics 2017, 36, 2956 (doi:10.1021/acs.organomet.7b00411).
Selective decarbonylation of p-nitrophenylesters of fatty acids to the corresponding linear α-olefins (LAOs) was achieved using palladium catalysis. After extensive ligand screening, a mixed ligand system exploiting the trans-spanning diphosphine XantPhos and an N-heterocyclic carbene (IPr) was identified as the most effective in yielding high α-selectivity and high conversions of the ester (>98% selectivity, >90% conversion using 2.5 mol% PdCl2 and 5 mol% of the ligands, 190 °C, 2-2.5 h). Based on insights from modeling at the density functional level of theory, we propose that the mixed ligand set achieves high α-selectivity by promoting olefin dissociation from the palladium center following β-hydride elimination, which is especially facilitated both by the combined steric bias of the mixed ligand set as well as by the ability of the XantPhos ligand to coordinate in both mono- and bidentate fashions.