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

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.

Graphical abstractEthyl 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).Figure optionsDownload full-size imageDownload as PowerPoint slide