An efficient synthesis of 1-oxo-1,2-dihydrobenzo[b][1,6]naphthyridine-4-carbonitriles

Abstract

Abstract Ethyl α -(dimethylaminomethylene)-2-cyanomethyl-4-phenylquinoline-3-carboxylate ( 2 ) as new synthons directed to 1-oxo-1,2-dihydrobenzo[b][1,6]naphthyridine-4-carbonitriles was obtained by the condensation of ethyl 2-cyanomethyl-4-phenylquinoline-3-carboxylate ( 1 ) and N , N -dimethylformamide dimethyl acetal (DMFDMA). Reaction of this enamine with primary amines ( 3 ) in HOAc-DMF at 120 °C then affords 2-substituted 1-oxo-1,2-dihydrobenzo[b][1,6]naphthyridine-4-carbonitrile derivatives ( 4 ) in good yields by a tandem addition–elimination–cyclization reaction.