A solvent-free synthesis of 5-methyl-1,2,4-triazolo[1,5- a ]pyrimidine-7(4 H ), an intermediate in the synthesis of antiviral Triazide® drug, in supercritical CO2 (200 bar) iwas first performed through cyclocondensation of 5-amino-3 H -1,2,4-triazole with acetoacetic ester in the presence of catalytic amounts of ZnCl2. Conversion was 90% depending on the temperature and reaction time.