Derivatives of the new ring system pyrazolo[4,3‐ d ]‐ v ‐triazine and the synthesis of 5,7‐disubstituted 3‐methylpyrazolo[4,3‐ d ] pyrimidines and 5,7‐disubstituted 3‐methylpyrazolo[4,3‐ d ]pyrimidine 6‐uxides which are structurally related to the nucleoside antibiotics formycin and formycin B

The synthesis of 7‐methylpyrazolo[4,3‐ d ]‐ v ‐triazin‐4‐one ( 6 ), a derivative of the new ring system, pyrazolo[4,3‐ d ]‐ v ‐triazine, has been accomplished by a diazotization reaction. Ring closure of the appropriate pyrazole derivative and oxidation of the preformed bicyclic heterocycle with m ‐chloroperoxybenzoic acid has furnished 7‐substituted 3‐methylpyrazolo[4,3‐ d ]pyrimidine 6‐oxides. Ring closures to yield various 5,7‐disubstituted 3‐methylpyrazolo[4,3‐ d ]pyrimidines are also discussed.