SYNTHESIS OF 4-NITRO-γ-CARBOLINES BY GRAEBE–ULLMANN REACTION

Abstract

Graebe–Ullmann reaction was used to synthesize 3-aryl(methyl)-1-methyl(cyclopropyl)-4-nitro-5Н-pyrido[4,3-b]indoles containing substituents in the pyridine ring. A new scheme was developed for the synthesis of the starting 1-[6-aryl(methyl)-2-methyl(cyclopropyl)-3-nitropyridin-4-yl]-1Н-1,2,3-benzotriazoles: 1) ammonolysis of 3-nitroisonicotinic acid ethyl esters, 2) a modified Hofmann reaction of 3-nitroisonicotinamides, 3) cleavage of ethyl (2-aryl-3-nitropyridin-4-yl)carbamates, 4) synthesis of 4-chloro-3-nitropyridines by diazotation reaction of 4-amino-3-nitropyridines, followed by nucleophilic substitution of diazo group in 4-pyridyldiazonium salts with a
chlorine atom.