A practical synthesis of pyrazolo [4, 3-e][1, 2, 4] triazolo [1, 5-c] pyrimidines, which are key intermediates in the preparation of adenosine receptor antagonists, is developed. The method allows introduction of a variety of aryl substituents at position 2 of the pyrazolo [4, 3- e][1, 2, 4] triazolo [1, 5-c] pyrimidine system via cyclocondensation of 5-amino-4- iminopyrazolo [3, 4-d] pyrimidine with benzaldehydes accompanied with oxidation by ...
