Water → 5-(2-methyl-2H-pyrazol-3-yl)-thiophene-3-carboxylic acid methyl ester

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5-Bromo-thiophene-3-carboxylic acid methyl ester (0.193 g, 0.87 mmol) was combined with 1-methyl-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (0.2 g, 0.96 mmol), caesium carbonate (0.424 g, 1.3 mmol), and palladium tetrakis(triphenylphosphine) (0.1 g, 0.09 mmol) in DME (10 mL), IMS 2 mL) and water (1 mL). The reaction mixture was degassed then heated by microwave irradiation to 140° C. for 20 minutes. The mixture was diluted with water then extracted with DCM (×3) then the organic solution was dried over sodium sulfate, filtered and the solvent evaporated. The residue was purified by chromatography on a 5 g silica II cartridge, eluting with 5-30% ethyl acetate in cyclohexane to give 5-(2-methyl-2H-pyrazol-3-yl)-thiophene-3-carboxylic acid methyl ester as a brown oil (0.163 g). LCMS m/z 223.24 [M+H]+ R.T.=3.24 min (Analytical Method 6).

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