Microwave-Assisted Synthesis of Trifluoromethyl-Containing Heterocycles

Significance

Reported is a microwave-assisted synthesis of trifluoromethyl derivatives of pyrazolo­pyrimidine 1, triazolopyrimidine 2 and pyrimidobenzimidazole 3 from the reaction of triethylorthoformate with 4,4,4-trifluoro-1-(thien-2-yl)butane-1,3-dione in the presence of the corresponding 5-amino-1H-pyrazole derivatives, 3-amino-1,2,3-triazole and 2-amino-benzimidazole. The structure of 5-trifluoromethyl-pyrazolo[1,5-a]pyrimidine 1 (R^¹ = Me, R^² = H) was confirmed by X-ray crystallography. 4,4,4-Trifluoro-1-(thien-2-yl)butane-1,3-dione was also coupled with azole diazonium salts to afford trifluoromethyl-substituted triazolo[3,4-c]1,2,4-triazine 4, pyrazolotriazine 5, and benzimidazo[5,1-c]1,2,4-triazine 6.