Facile and general syntheses of 3- and/or 5-substituted 7H-pyrazolo[4,3-e]-1,2,4-triazolo[4,3-c]pyrimidines as a new class of potential xanthine oxidase inhibitors†

Abstract

Convenient syntheses of 3- and/or 5-substituted 7H-pyrazolo[4,3-e]-1,2,4-triazolo[4,3-c]pyrimidines as a new class of potent xanthine oxidase inhibitors, involving the oxidative cyclisation of 4-alkylidenehydrazino- or 4-arylmethylidenehydrazino-1H-pyrazolo[3,4-d]pyrimidines with 70% nitric acid as the key step, are described.