Benzo -1,6-naphthyridine-3-carboxylates

JHC961). When 2,7-naphthyridine (192) was brominated, a mixture of 4-bromo and 4,5-dibromo products was formed (70JHC419). In basic medium bromine converted benzo[6][l,8]naphthyridine-9-carboxaldehyde into the 3,7-dibromo-9-carboxylic acid (92JHC1197). 

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... 

In a cydization involving substituents in peri positions, carboxylation of the dianion from reaction of the quinoline (131) with two equivalents of LDA gives the benzo[/,y]-2,7-naphthyridine (132), as shown in Scheme 28 (82H2089). 

The treatment of 2,5-dichloro-3,6-dihydroxycyclohexa-2,5-diene-l,4-dione 269 with 2-substituted-l,8-naphthyr-idine-3-carboxylic acid hydrazides 270 in ethanol under reflux resulted in the formation of 3,8-di(2-substituted-l,8-naphthyridin-3-yl)benzo(l,2-r 4,5- )bis[l,3,4]oxadiazine-5,10[l//,6//]diones 271 <2000IJH311> (Equation 42). 

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