Electrochemical oxidative [4 + 2] annulation of tertiary anilines and alkenes for the synthesis of tetrahydroquinolines

Heterocyclic compounds, especially nitrogen heterocycles, are one of the most important classes of compounds in the pharmaceutical and agrochemical industries. The oxidative [4 + 2] annulation reaction provides a powerful tool for the rapid construction of six-membered heterocycles. Herein, we report a metal- and external oxidant-free method for the uniform synthesis of tetrahydroquinolines through the electrochemical oxidative [4 + 2] annulation of tertiary anilines and alkenes. In this strategy, one partner loses only two hydrogen atoms while another partner reduces one degree of unsaturation, accompanied by the generation of hydrogen. Under the conditions of an undivided cell and room temperature, a series of tetrahydroquinoline derivatives were prepared with good yields.