Dipolar Cycloaddition of Ethyl Isocyanoacetate to 3-Chloro-2-(methylthio)/2-(methylsulfonyl)quinoxalines: Highly Regio- and Chemoselective Synthesis of Substituted Imidazo[1,5-a]quinoxaline-3-carboxylates

An efficient route for regio- and chemoselective synthesis of substituted 3-(carboethoxy)imidazo[1,5-a]quinoxalines and novel diimidazo[1,5-a:5',1'-c]quinoxalines via base-induced cycloaddition of ethyl isocyanoacetate to unsymmetrically substituted 3-chloro-2-(methylthio)/2-(methylsulfonyl)quinoxalines has been reported.