4- Methyl-benzo -1,7-naphthyridine

The benzo-fused dihydrotetrazolo[2,7]naphthyridine 308 is a minor end-product of a mixed Hantzsch pyridine synthesis involving 2-azido-3-nitrobenzaldehyde, /3-aminocrotononi trile, and methyl /3-aminocrotonate in ethanol (Scheme 76) <2001TL4507>. 

Acetyl-8,9-dimethoxy-5,6-dihydro-4/7-benzo[iie][l,6]naphthyridine (159) underwent ozonolysis to afford methyl l-acetyl-4-methoxycarbonylmethylene-l,2,3,4-tetrahydro-l,6-naphthyridine-5-carboxylate (160) (or tautomer) (substrate, MeOH, 03, —78°C, 1 h Me2S, 20°C %).1143... 

Dimethyl-l,8-naphthyridin-2(l//)-one with butyllithium followed by benzo-nitrile and then hydrochloric acid gave 5-methyl-7-phenacyl-l,8-naphthyr-idin-2(l//)-one (39) in contrast, the same substrate treated similarly, but with sodium amide/ammonia in place of butyllithium, gave the isomeric 7-methyl-5-phenacyl-l,8-naphthyridin-2(l//)-one (40) (49%).401... 

The reactivity of 4,6-benzo[/ ][l,7]naphthyridine in Diels-Alder reactions with maleic acid and dimethyl acetylenedicarboxylate was examined. The reaction afforded adduct 332 (1996MI5). 6-Ethoxycarbonyl- 333a and phenacylmethylides 333b were used as 1,3-dipolar reagents in reactions with methacrylic acid, methyl methacrylate, butyl vinyl ether, methyl vinyl ketone, maleic anhydride and dimethyl acetylenedicarboxylate (1996MI5, 1999AJC149). 

---