Naphthyridines. Part III. Preparation of pyrimido[1,2-a]- and imidazo-[1,2-a]-[1,8]naphthyridines from 2-amino-1,8-naphthyridines

Abstract

2-Amino-1,8-naphthyridines bearing alkyl and aryl substituents are shown to react with ethyl acetoacetate and ethyl ethoxymethylene-malonate, -acetoacetate, and -cyanoacetate to yield 2-(ethoxycarbonylvinylamino)-1,8-naphthyridines. Thermal cyclisation of some of these derivatives yields pyrimido[1,2-a][1,8]naphthyridines. 2-Amino-1,8-naphthyridines are converted into imidazo[1,2-a][1,8]naphthyridines on treatment with α-bromo-carbonyl compounds.