Rapid access to pyrrolo[3,4-c]quinoline-1,3-diones: An improved synthetic protocol using a precursor prepared by Pfitzinger reaction

An efficient pTSA-mediated cyclization cascade reaction of Pfitzinger's ester and benzoyl hydrazines has been developed providing a simple procedure for synthesis of pyrrolo [3,4-c]quinoline-1,3-dione derivatives. Unlike traditional synthetic protocol, this method avoids an additional step of conversion of quinoline-3,4-dicarboxylic acids to an anhydride, allowing direct reaction of ester derivative with hydrazine nucleophiles.