Tautomeric 1,5-Naphthyridinones and Extranuclear Hydroxy- 1,5-Naphthyridines

From an overwhelming mass of data on 7t-deficient nitrogenous heterocycles, it is usually considered axiomatic that (wherever possible) hydroxy-1,5-naphthyridines will exist predominantly as their respective 1,5-naphthyridinone tautomers for example, l,5-naphthyridin-2-ol (2) will exist as l,5-naphthyridin-2( 1 //)-one (3). This postulate has been strengthened by ionization constant, infrared spectral, and ultraviolet spectral measurements on simple 1,5-naphthyridinones 887,1026,1027,1035,1040 calculations have been less meaningful.1295 

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

The mass spectra of 1,5-naphthyridin-2( 1 //)-one, 1,5-naphthyridin-4( 1 //)-one, and 4-hydroxy-l,5-naphthyridin-2(17f)-one have been compared with those of isomeric naphthyridinones.1253 

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