Electrooxidative Allene Annulations by Mild Cobalt-Catalyzed C–H Activation

Versatile cobalt catalysis enabled electrochemical C–H activation with allenes. Thus, allene annulations were accomplished in terms of C–H/N–H functionalizations with excellent levels of chemoselectivity, site selectivity, and regioselectivity under exceedingly mild conditions. Detailed mechanistic studies were conducted, including reactions with isotopically labeled compounds, kinetic investigations, and in-operando infrared spectroscopic studies. Further, computational studies were supportive of a non-rate-determining C–H cleavage and gave key insights into the regioselectivity of the allene annulation. The practical utility of the user-friendly approach was furthermore highlighted by gram-scale electrocatalysis.