Enamino esters in the synthesis of heterocyclic systems. Transformation of diethyl acetone-1,3-dicarboxylate into polysubstituted 1,2,7,8-tetrahydro-2,7- naphthyridine-4-carboxylates

Abstract

A simple three step synthesis of aminosubstituted 1,2,7,8-tetrahydro-2,7- naphthyridine-4-carboxylates is described. Ethyl (3-cyano-6-ethoxy-2-oxo-1,2- dihydropyridin-4-yl)acetate 3, formed by the condensation of diethyl acetone-1,3-dicarboxylate with malononitrile, was transformed with N,N-dimethylformamide dimethylacetal (DMFDMA) into (E)-ethyl 2-(3-cyano-6-ethoxy-2-oxo-1,2-dihydropyridin-4-yl)-3-(dimethylamino)propenoate 4. In further reaction the dimethylamino group was substituted with amino, hydroxy or substituted hydrazino group, followed by cyclisation to afford substituted 1-amino-7,8-dihydro-2,7-naphthyridine-4-carboxylate 6b, 1-imino-7,8-dihydro-1H-pyrano[3,4-c]pyridine-4-carboxylate 8, and 1-imino-2-aminosubstituted 1,2,7,8-tetrahydro-2,7-naphthyridine-4-carboxylates 13a-i. © ARKAT-USA, Inc.