Regioselective synthesis of 2- and 5-trifluoromethyl-or 2- and 5-difluoromethylpyrazolo[1,5-c]pyrimidines based on 7,7,7-trifluoro-or 7,7-difluoro-2,4,6-trioxoheptanoic and 6-trifluoromethyl-or 6-difluoromethylcomanic acids

6-Tri- and 6-difluoromethylcomanic acids and their ethyl esters reacted with aminoguanidine, predominantly giving 5-R F -pyrazolo[1,5- c ]pyrimidines, whereas the reaction of the openchain synthetic equivalents, i.e. , ethyl 7,7,7-trifluoro- and 7,7-difluoro-2,4,6-trioxoheptanoates, with this polynucleophile allowed us to obtain regioselectively 2-R F -pyrazolo[1,5- c ]pyrimidines.