Synthesis of novel 1,4,5-trisubstituted 3-trifluoromethylpyrazoles via microwave-assisted Stille coupling reactions

1,5-Disubstituted 3-trifluoromethylpyrazoles were reacted with N-bromosuccinimide in DMF at room temperature or 70-80 °C for 1-2 h to afford the corresponding 4-bromo-substituted pyrazoles 2 in 95-99% yields. The microwave-assisted Stille coupling reactions of 2 with arylstannanes having a substituent on the benzene ring and allylstannane in refluxing CH₃CN in the presence of Pd(PPh₃)₄ provided the corresponding 1,4,5-trisubstituted 3-trifluoromethylpyrazoles 3 in 75-98% yields.