Practical synthesis of 8-acyl-7-alkyl-1,6-naphthyridin-5(6H)-ones

Reaction of a set of enaminones with 2-chloronicotinoyl chloride or 2,6-dichloro-5-fluoronicotinoyl chloride mainly leads to N-acylation products which cyclize directly or reacting with sodium hydride to give 8-acyl-7-alkyl-1,6-naphthyridin-5(6H)-ones. Due to their easy availability these compounds are attractive precursors for synthesis of polycondensed heterocycles like naphtho[2,3-h][1,6]naphthyridin-5-ones and pyrido[3,2-c][1,6]naphthyridin-6-ones.