v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part XII. Cleavage of the pyrimidine ring in 8-azapurines by some active methylene reagents and eventual closure to give v-triazolo[4,5-b]pyridines

Abstract

8-Azapurine (1) and its 2-amino-, 2-thioxo-, and 2-oxo-derivatives reacted with ethyl cyanoacetate to form 4-aminomethyleneamino-, 4-diaminomethyleneamino-, 4-thioureido-, and 4-ureido-5-(2-cyano-2-ethoxycarbonylvinyl)-1,2,3-triazoles [(4a), (4b), (5a), and (5b), respectively], and with malononitrile to form the corresponding derivatives of 5-(2,2-dicyanovinyl)-1,2,3-triazole [(4c), (4d), (5c), and (5d), respectively]. The triazoles underwent cyclisation either to regenerate the starting azapurine or to form 5-amino-6-cyano-v-triazolo[4,5-b]pyridine (7a). 8-Azapurine and its 2-oxo-derivative reacted with cyanoacetamide to give 5-amino-6-carbamoyl-v-triazolo[4,5-b]pyridine (7b), and with dimedone to give 5,6-dihydro-6,6-dimethyl-v-triazolo[4,5-b]quinolin-8(7H)-one (10). 8-Azapurine formed 6-acetyl- and 6-ethoxycarbonyl-5-methyl-v-triazolo[4,5-b]pyridine (11a and b) in reactions with acetylacetone and ethyl acetoacetate, respectively.

U.v. and ¹H n.m.r. spectra are reported and discussed.