Rhodium(I)-Triethylamine-Catalyzed 1,4-Addition of Enones

Significance

The authors describe a highly efficient rhodium-catalyzed 1,4-addition of alkenyl trifluoroborate salts to cyclic enones in the presence of triethylamine. Notably, they found that the use of triethylamine enhanced both reactivity and enantioselectivity. Mechanistic studies revealed that triethylamine forms a complex with rhodium, which serves as the active catalyst because it accelerates the B-Rh transmetalation reaction by displacement of the original ligand on Rh. In addition, it is noteworthy that the authors could achieve the first rhodium-catalyzed 1,4-addition of a (Z)-alkyl-substituted terminal alkenyl group to enones.