Electrochemical dehydrogenative and desulfurative annulation for the synthesis of isoxazolines and pyrazolines†

An electrochemical dehydrogenative annulation under mild conditions has been developed, which offers a simple and efficient way to access synthetically useful isoxazolines and pyrazolines. This methodology demonstrates remarkable scalability, as evidenced by successful gram-scale synthesis through both continuous-flow and batch electrolysis. The synthetic utility of this protocol was further highlighted by the efficient preparation of Parecoxib, a clinically important COX-2 inhibitor, on a gram scale from commercially available starting materials. Furthermore, we have also successfully extended this electrochemical strategy to achieve the desulfurative annulation of thioethers.