From a Pyridine Substrate and Two Synthons

3-Pyridinamine (54) with diethyl ethoxymethylenemalonate gave ethyl 4-oxo-l,4-dihydro-l,5-naphthyridine-3-carboxylate (55) (reactants, Dowtherm A, 150°C, reflux, 1 h 80%) 101 somewhat similarly, 5-amino-2(l//)-pyridinone gave ethyl 4,6-dioxo-l,4,5,6-tetrahydro-l,5-naphthyridine-3-carboxylate (56) [Et0CH=C(C02Et)2, Ph20, reflux, 1 h 20%].233 

3-Aminopicolinic acid (57) with ethyl acetoacetate gave 2-methyl-1,5-naphthyr-idin-4( 1 //)-one (58) (neat reactants, reflux, 4h 13%).828,1000 

2-Methoxy-5-nitropyridine (59) with l-phenyl-3-phenylsulfonylpropane (60) gave 2-methyl-6-phenyl-8-phenylsulfonyl-l,5-naphthyridine (61) (reactants, 

This type of synthesis is represented only by several procedures akin to the Doebner-Miller quinoline synthesis, in which both synthons are the same. 

4-Methyl-3-pyridinamine (62) and an excess of acetaldehyde gave 2,8-dimethyl-1,5-naphthyridine (63) (substrate, 10M HC1, 5°C MeCHO in dropwise 0°C, 1 h then reflux, 1 h 16% note the necessity for oxidation, either aerial or by 

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