A mixture of methyl 4-bromo-5-(trifluoromethyl)-2-thiophenecarboxylate (0.8 g, 40% purity, 1.11 mmol), 1-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (0.299 g, 1.434 mmol), tetrakis (0.128 g, 0.11 mmol) and K2CO3 (0.459 g, 3.32 mmol) in dioxane/H2O (5 mL/1 mL) was heated to 70° C. in a sealed tube. After 12 h, the reaction mixture was concentrated under vacuum and purified on silica (EtOAc/Hex, 40-60%) to afford the title compound (0.25 g, 70%) as a light yellow solid: LC-MS (ES) m/z 291 (M+H)+.
