Ligand Promoted and Cobalt Catalyzed Electrochemical C−H Annulation of Arylphosphinamide and Alkyne

A cobaltaelectro-catalyzed dehydrogenative [4+2] annulation of arylphosphinamides with alkynes was proposed in the present study to selectively construct a range of cyclic phosphinamide derivatives. Picolinic acid acted as a ligand to promote this transformation. A total of 38 examples demonstrated broad substrate scope, sufficient functional tolerance and excellent regioselectivity. Moreover, no additional oxidants and electrolytes were needed and it was possible to achieve gram scale synthesis, late-stage diversification and the removal of the directing group. Cyclic voltammetry and kinetic isotope experiments provided a better understanding to the reaction mechanism.