The present invention relates to novel processes for preparing triazolo [4,5-d] pyrimidines, including Ticagrelor, via new intermediates and new routes of synthesis. The synthesis begins with readily available and inexpensive starting material such as 5-nitro-2,4,6-trichloropyrimidine and leads to series of novel intermediates, which are commercially viable and industrially advantageous (solid intermediates, high yields and convenient experimental condition) for the preparation of highly pure Ticagrelor.