Pyrazolopyridines. Part II. Preparation of 3-substituted 2-aryl-2H-pyrazolo[4,3-b]pyridines. Acid-catalysed cyclisation of 2-arylaminomethyl-3-nitropyridines

Abstract

The reactions of 2-arylaminomethyl-3-nitropyridines with primary aromatic amines, hydrogen chloride, and ethanol gave 3-arylamino-, 3-chloro-, and 3-ethoxy-2-arylpyrazolo[4,3-b]pyridines, respectively. Cyciisation of 2-arylaminomethyl-3-nitropyridines in acetic acid yielded 2-arylpyrazolo[4,3-b]pyridin-3(2H)-ones. Mechanisms for the formation of these compounds are suggested.