Preparation of 1,8-Naphthyridinones and the Like

Many tautomeric and nontautomeric naphthyridinones have been made by primary synthesis (see Chapter 8) and a few by ozonolysis of alkylidene-l,6-naphthyridines (see Section 9.2.2) or by hydrolysis of halogeno-l,6-naphthyridines (see Section 10.4.2). Other preparative routes are illustrated by the following examples. 

Ethyl 5-amino-7-benzylseleno-8-cyano-2-methyl-l,6-naphthyridine-3-carboxy-late gave ethyl 7-benzylseleno-8-cyano-2-methyl-5-oxo-5,6-dihydro-l,6-naphthyridine-3-carboxylate (5) (substrate, AcOH, reflux, NaOH[, slowly, then reflux, 30 min 47%).959 

Irradiation of 1,6-naphthyridine 1,6-dioxide in water gave 1,6-naphthyridin-2(1 A)-one 6-oxide (no details).216 

Note This oxidative process provides nontautomeric naphthyridinones. 1,6-Naphthyridine 6-methiodide (11, R = H) underwent oxidation to 6-methyl -l,6-naphthyridin-5(6//)-one (12, R = H) [substrate, H20, 0°C, NaOH/H20[ during 5 min K3Fe(CN)6/H2OJ, during 30 min 0°C, 90 min 20°C, 5 h  

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