Where the Two-Atom Synthon Supplies

Nearly all the reported syntheses in this category have used the synthon to supply C2 + C3 of the resulting 1,5-naphthyridine, but C3 + C4 may be so supplied, as illustrated at the end of the following list of typical examples. 

Ethyl 3-aminopicolinate (29) with diethyl malonate gave 4-hydroxy-1,5-naphthyridin-2( l //)-one (30) [neat reactants, 120°C, 5 h solid, EtONa, EtOH, reflux, 5h solid, 2.5M NaOH, reflux until gas ceased 96%].1151 

Somewhat similarly, 3-aminopicolinic acid with ethyl acetoacetate gave 2-methyl-l,5-naphthyridin-4(l//)-one (neat reactants, reflux, 4 h 13%).1000 3-Amino-2-pyridinecarbonitrile (31) with diethyl malonate gave 4-amino-1,5-naphthyridin-2(l//)-one (32) (neat reactants, EtONa, reflux, 7.5 h 36%).725 

2-(a-Hydroxybenzyl)-6-methoxy-3-methylaminopyridine (33) with allyltri-methylsilane gave 2-methoxy-5-methyl-8-phenyl-6-(trimethylsilylmethyl)-5,6, 7,8-tetrahydro-l,5-naphthyridine (34) (reactants, BF.3,Et20. 60-80°C, 4.5 h 50%) analogs likewise.619 

3-Benzylideneamino-6-methoxypyridine (35) underwent partially regioselective cyclocondensation with phenylacetylene in the presence of oxidizing agents to afford a separable mixture of 2-methoxy-6,8-diphenyl-1,5-naphthyridine (36) and 6-methoxy-2,4-diphenyl-1,7-naphthyridine (37) (reactants, FeCl3, 

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