DMSO as a Methine Source in TFA-Mediated One-Pot Tandem Regioselective Synthesis of 3-Substituted-1-Aryl-1<i>H</i>-Pyrazolo-[3,4-<i>b</i>]quinolines from Anilines and Pyrazolones

Abstract

An acid-mediated and DMSO participant one-pot tandem synthesis of 3-substituted-1-aryl-1<i>H</i>-pyrazolo-[3,4- <i>b</i>]quinoline from readily available anilines and pyrazolones was achieved. This method enables regioselective construction of the valuable heterocycles under transition-metal and oxidant-free conditions in which DMSO acts as a methine source as well as solvent making this process an environmentally benign approach. A broad range of diversely substituted aryl amines and pyrazolines are successfully employed in this reaction to access a series of pyrazolo[4,3-<i>c</i>]quinolones through a novel cascade mechanism. Furthermore, the application and mechanistic studies of the present methodology also demonstrated.