The reactions of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one and its derivatives in the synthesis of benzodiazepines and benzimidazoles: reinvestigation, structural reassignment, and new insight

Abstract The reaction of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1 H )-one with the Vilsmeier reagent, the treatment of 3-(3,4-dihydroquinoxalin-2(1 H )-on-3-yl)-1,2-dihydro-1,5-benzodiazepin-2(1 H )-one hydrochloride with 10% sodium hydroxide and 3-benzimidazoylquinoxalin-2(1 H )-one with both 1,2-phenylenediamine dihydrochloride, and the reactions of 1,2-phenylenediamine have been reinvestigated and the structures of these reaction products have been revised. It has been shown that in all the three cases other regioisomers of products have been formed as distinct from the literature data. The mechanisms to explain the formation of the products are suggested.