Naphthyridines by Cyclocondensation of Pyridine Substrates with Synthons

7-Naphthyridines by Cyclocondensation of Pyridine Substrates with Synthons 

In this potentially wide category of primary syntheses, the few reported types are classified according to the ring atom(s) supplied to the naphthyridine by the synthon. 

4-[2-Ethoxycarbonyl-2-(triphenylphosphoranylideneamino)vinyl]pyridine (21) and phenyl isocyanate gave ethyl l-anilino-2,7-naphthyridine-3-carboxylate (22) (PhMe, 150°C 59%) analogs likewise).442 

Ethyl 2,6-dimethyl-4-phenylethynyl-3-pyridinecarboxylate (23) with ethanolic ammonia gave 6,8-dimethyl-3-phenyl-2,7-naphthyridin-l(2//)-one (24) (120°C, sealed 85%).1055 

Methyl 5-acetyl-4-methoxycarbonylmethyl-3-pyridinecarboxylate (25) gave methyl 8-methyl-6-oxo-6,7-dihydro-2,7-naphthyridine-4-carboxylate (26) (neat reactants, 150°C 75%)206 or the 5,6,7,8-tetrahydro derivative, jasmi-nine [NH4C1, Et3N, Ti(OPr )4, MeOH, 20°C then NaBH4 25%] 206 an alkaloid isolated577 from several species of Oleaceae. 

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