Lewis Acid-Mediated Isothiocyanation and Chlorination of Quinoxalin-2(1H)-ones under Visible Light Conditions

Lewis acid-mediated selective C3-isothiocyanation of quinoxalin-2(1H)-ones using N-thiocyanatosaccharin as an isothiocyanate source under visible light conditions at room temperature is described. Under similar conditions with N-chlorosaccharin, the C3-chlorination of quinoxalin-2(1H)-ones achieved a 2 h time frame. Good to an excellent yield of products was obtained in both cases with broad functional group tolerance. Control experiments suggest that the reaction proceeds through a radical mechanism. The present procedure demonstrates the applicability at gram-scale reactions and highlights the subsequent conversion of isothiocyanates into representative thiourea derivatives, and one of the chloro derivatives transformed to glycogen phosphorylase inhibitors.