Pyridylaminomethylenemalonates, Their N-Oxides, and Related Systems

When 3-aminopyridine was reacted with EMME in Dowtherm A, first at 150°C for 1 hr and then at boiling temperature for 1 hr, ethyl 4-hydroxy-1,5-naphthyridine-3-carboxylate was obtained in 73-82% yields (46JA-1317). 

The reaction of 5-amino-2-hydroxypyridine and EMME refluxing diphenyl ether for 1 hr gave 4,6-dihydroxy-1,5-naphthyridine-3-carboxylate in 20% yield after vacuum sublimation of the crude product (71JOC1331). 

N-(6-Substituted 3-pyridyl)aminomethylenemalonate was heated in Dowtherm A at 250-270°C for 10-20 min under nitrogen to give 6-substi-tuted l,5-naphthyridine-3-carboxylates in 71-87% yields [84JAP(K)-93080]. 

8-Dihydroxy- and 4-hydroxy-8-methoxy-l, 5-naphthyridine-3-carbox-ylates (981) were prepared in 50% and 72% yields, respectively, by the 

The cyclization of diethyl N-( l-methyl-4-oxo-1,4-dihydropyrid-3-yl) aminomethylenemalonate by heating in boiling Dowtherm A for 15 min afforded 1,5-naphthyridine-3-carboxylate (982) in 35% yield (78JOC1331). 

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