Cobalt(0)-Catalyzed Isomerization of Allylamines Promoted by Monodentate Benzofuran Phosphines

Isomerization of C-C double bonds is an efficient tool for converting bulk olefins into high-value compounds. Herein we describe a newly developed homogeneous cobalt-based system which enables the isomerization of allylamines to enamines with similar activity and selectivity to noble metal catalysts. The catalyst activity was bound to the presence of furan-2-yl substituents of the phosphine ligand, while the selectivity was increased with the number of benzofuran-2-yl groups. The resulting cobalt(0) catalysts allowed the isomerization of various aliphatic and aromatic allylamines, including the synthesis of industry-relevant products with high catalytic activity. Potential industrial application of our system was substantiated by the scale-up experiment, which provided 311 g of citronellal in 96% yield. We proposed a plausible mechanism based on EPR and NMR analysis combined with deuterium labeling, radical trapping experiments, and kinetic studies.