Heterocyclic studies. Part XXXI. New routes to reduced imidazole, pyrimidine, and pyridopyrimidine derivatives

Abstract

Treatment of 4-(substituted amino)-6-chloro-5-nitropyrimidines (4-substituents N-ethylanilino, hexamethylene-amino, N-methyl-2-hydroxyethylamino, 2-hydroxyethylamino, allylamino, and benzylamino) with dilute acetic acid gave corresponding 3-(substituted amino)-3-amino-2-nitroacrylonitrile derivatives. Cyclisation of 4-(N-alkyl-2-chloroethylamino)-6-chloro-5-nitropyrimidines gave imidazopyrimidines which were immediately cleaved to give dihydroimidazoles with a 2-[cyano(nitro)methylene] substituent. Similarly 4-(N-alkyl-3-hydroxypropylamino)-pyrimidines gave pyrimidopyrimidines which were cleaved to give reduced pyrimidines. Hexahydropyridopyrimidines were obtained in analogous fashion from 4-[2-(2-hydroxyethyl)piperidino]pyrimidines. Mechanisms of the ring-cleavage reactions are discussed.