Where the Synthon Supplies One Ring Atom

Of the 10 possibilities, only the Nl, N6, or C7 atoms of 1, 6-naphthyridines have been provided by the synthon in such primary syntheses. Classified examples follow. 

2-Dicyanovinyl)-1 -p-ethoxycarbonylphenyl-4-(pyrrolidin-1 -yl)-1,2,5,6-tet-rahydropyridine (67) with ammonia gave 2-amino-6-/ -ethoxycarbonylphe-nyl-5,6,7,8-tetrahydro-1,6-naphthyridine-3-carbonitrile (68) (NH3/MeOH, 30°C, 12 h 96%) analogs likewise.378 

3-(2-Benzoylethyl)-2,2,6,6-tetramethyl-4-piperidinone (69) with ammonium ion gave 5,5,7,7-tetramethyl-2-phenyl-5,6,7,8-tetrahydro- 1,6-naphthyridine (70) (substrate. HC1, NH4C1, EtOH, reflux, 4h 77%) analogs likewise.933,1351 

5-[2-(Carboxymethyl)heptyl]-l-veratryl-2,4-piperidinedione (71) with veratry-lamine gave 4-hexyl-1,6-diveratryl-3,4,4a,5-tetrahydro-1,6-naphthyridine-2,7-dione (72) (PhH, reflux, water removal, 12 h 60%).549 

5-Acetyl-3-bromo-6-(2-dimethylaminovinyl)-2(177)-pyridinone (73) with ammonium acetate gave 3-bromo-5-methyl-1,6-naphthyridin-2( 1 //)-one (74) (AcONH4, Me2NCHO, 95°C, 5 h 54%) 928 analogs likewise.928 1166 

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