Microwave-assisted synthesis of fused heterocycles incorporating trifluoromethyl moiety

4,4,4-Trifluoro-1-(thien-2-yl)butane-1,3-dione (1) reacts with 5-aminopyrazole, 1,2.4-aminotriazole and 2-aminobenzimidazole derivatives, in the presence of triethylorthoformate under pressurized microwave irradiation to afford the corresponding trifluoromethyl derivatives of pyrazolol[1,5-a]pyrimidine, 1,2,4-triazolo[1,5-a]pyrimidine, and pyrimidol[1,2-a]benzimidazoles. Also, compound 1 couples readily with azole diazonium salts to give pyrazolo[5,1-c]triazine, benzimidazo[5,1-c] 1,2,4-triazine, and triazolo[3,4-c] 1,2.4-triazine derivatives incorporating trifluoromethyl group. (c) 2008 Elsevier B.V. All rights reserved.