Preparation of Tautomeric 1,5-Naphthyridinones and the Like

Most such naphthyridinones have been made by primary synthesis (see Chapter 1) and some by hydrolysis of halogeno-1,5-naphthyridines (see Section 3.2.3). Other preparative routes are illustrated by the following examples. 

4-Chloro-2-methoxy-l,5-naphthyridine (12) gave 4-chloro-l,5-naphthyridin-2(l//)-one (13) (5M HC1, dioxane, reflux, 1 h 50% note survival of the chloro substituent under these mild conditions).1151 

Ethyl 6-p-chlorophenoxy-4-(3-diethylaminopropyl)amino-1,5-naphthyridine-3-carboxylate (9a, R = C02Et) gave 2-/ -chlorophenoxy-8-(3-diethylaminopro-pyl)amino-7-hydroxymethyl-l,5-naphthyridine (9a, R = CH2OH) 11AIH,-Et20, 10 min substrate/Et2OJ, dropwise then 20°C, 1 h 32%).967 

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