Where the Synthon Supplies Two Ring Atoms

Primary Syntheses of 1,6-Naphthyridines 8.3.2. Where the Synthon Supplies Two Ring Atoms 

Of the many possibilities, only C2 + C3, N6 + C7, and C7 + C8 have been supplied by the synthon in such primary syntheses. Moreover, most of the published procedures involve the provision of C2 + C3, as illustrated by the typical examples that follow. Such condensations may also be used to make fused 1, 6-naphthyridines.24 27 29 41 

2-Amino-3-pyridinecarbaldehyde (82) with ethyl cyanoacetate gave 2-oxo-1,2-dihydro-l,6-naphthyridine-3-carbonitrile (83) (reactants, trace piperidine, EtOH, reflux, 1 h 92%) 247 also analogs similarly.924 

6-Diamino-3-pyridinecarbaldehyde (84) with 2-(2,6-dichlorophenyl)acetoni-trile gave 3-(2,6-dichlorophenyl)-l,6-naphthyridine-2,7-diamine (85) (EtOCH2CH2ONa, EtOCH2CH2OH, reflux, 30 min 82%) 239 also analogous condensations.641,683,974 

4-Amino-3-pyridinecarbaldehyde (86) with limited 2,3-butanedione gave 2,2 -bi-l,6-naphthyridine (87) (substrate, NaOH, H20, EtOH, reflux synthon/ EtOHJ, dropwise during 3h reflux, 8h 81%).620 

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