Aza-analogues of pteridine. III. Some monomethoxy-1,2,4,6,8-pentaazanaphthalenes and related compounds

4-Hydrazino-2-methoxy-6-methyl-5-nitropyrimidine reacted with triethyl orthoformate to give the ethoxymethylenehydrazino analogue or 4-methoxy-6-methyl-7-nitro-1,2,3a,5-tetraazaindene according to conditions. The first of these products was converted by reductive cyclization and subsequent dehydrogenation into 7-methoxy-5-methyl- 1,2,4,6,8-pentaazanaphthalene. Attempts to hydrolyse this and related compounds to the corresponding 7-hydroxypentaazanaphthalenes failed and direct approaches via appropriate 2-hydroxypyrimidines gave only 4- hydroxy-7-nitrotetraazaindenes. ��� 5-Alkoxypentaazanaphthalenes were prepared via 1,2-dihydropentaaza- naphthalene or its 5-chloro derivative. Nucleophilic displacements were used to make the 5-hydroxy, 5-methylthio, 5-diethylamino, and other analogues from 5-methoxy-3-methylpentaazanaphthalene. ��� The ionization constants, ultraviolet spectra, and proton magnetic resonance spectra of members of both bicyclic series are tabulated and discussed.