From a Pyridine Substrate and Synthon s

2-Dicyano-1 -(o-methoxypheny 1)vinylamino] -1 -methylpiperidine (25) gave the 4-amino-2-(/ -methoxyphenyl)-8-methyl-5,6,7,8-tetrahydro-l, 8-naphthyr-idine-3-carbonitrile (26) (NaH/Me2NCHO 85%).1177 

Of the many possibilities within this type of synthesis, only nine are exemplified in the literature where one synthon supplies Nl, C2, C2 + C3, C4a + C8a, N1+C2 + C3, C2 + C3 + C4, or Nl + C2 + C3 + C4 or when two synthons supply N1 and C2 or C2 and C3 + C4. The following examples illustrate each of these primary synthetic routes. 

2-Chloro-3-(2-ethoxycarbonylvinyl)pyridine (27) gave 1,8-naphthyridin-2( 1//)-one (28) (NH3/EtOH 74%).1044 

3-(2-Nitrovinyl)-2-pyridinamine (29) gave 3-nitro-2-phenyl-l,8-naphthyridine (30) (PhCHO, xylene 75%).1278 

2-Chloro-6-methyl-3-(sulfamoylacetyl)pyridine gave 1 -ethyl-7-methyl-4-oxo-l,4-dihydro-l,8-naphthyridine-3-sulfonamide (31) [HC(OEt)3, heat 44%].1045 

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