Reactions of 1,8-Naphthyridinecarboxylic Acids

Only decarboxylation, amide formation, and esterification are represented in the 1,6-naphthyridine literature. Examples follow. 

6-Methyl-5-oxo-5,6-dihydro-l,6-naphthyridine-8-carboxylic acid (8, R = C02H) gave 6-methyl-1,6-naphthyridin-5(6//)-one (8, R = H) (neat substrate, 250°C, min 77%) 876 2-oxo-5-(pyridin-4-yl)-l, 2-dihydro-1,6-naphthyridine-3-car-boxylic acid (9, R = C02H) gave 5-(pyridin-4-yl)-l,6-naphthyridin-2(l//)-one (9, R = H) (neat substrate, 370°C, 3 min 72%)490 

7-Dimethyl-4-oxo-l,4-dihydro-l,6-naphthyridine-3-carboxylic acid (10, R = C02H) gave 5,7-di methyl-l,5-naphthyridin-4( 1 //)-one (10, R = H) (substrate, Cu powder, 260°C, 10 mmHg 50% as sublimate).1255 

2-Amino-l,6-naphthyridine-3-carboxyhc acid (13, R = H gave methyl 2-amino-l,6-naphthyridine-3-carboxylate (13, R = Me) (substrate, H2S04 H2S04/ MeOH in dropwise reflux, 3 h with additional reagent every 45 min 70%).247 

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