Naphthyridines by Cyclization of Pyridine Derivatives

Such a synthesis is possible by completion of any one or five bonds of the final naphthyridine. All such possibilities have been attempted, as illustrated in the following examples. 

Ethyl 3-cyanomethyl-4-pyridinecarboxylate (2) gave 3-hydroxy-2,6-naphthyri-din-1 (2//)-one (3) (H2S04, 80°C, 15 min 50% presumably via an intermediate amide) also analogs.710 

The Naphthyridines The Chemistry of Heterocyclic Compounds, Volume 63, by D.J. Brown Copyright 2008 John Wiley Sons, Inc. 

Only an unsuccessful attempt at this procedure has been reported.46 

6-Dimethyl-3-phenylethynyl-4-pyridinecarboxamide (4) gave 5,7-dimethyl-3-phenyl-2,6-naphthyridin-1 (2//)-one (5) (EtONa/EtOH, reflux 73%).1055 

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