To a solution of 5-bromo-2-thiophenecarboxylic acid (100 mg, 0.48 mmol) in dioxane/H2O (5:1, 6 mL) was added K2CO3 (267 mg, 1.93 mmol), tetrakistriphenylphosphine Pd(0) (28 mg, 24 umol) and 5-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)-1-methyl-1H-pyrazole (94 mg, 0.48 mmol). The reaction mixture was heated to 80° C. in a sealed tube for 12 h and was then partitioned between 6N NaOH and DCM. The pH of the aqueous phase was adjusted to ˜3 with 3M HCl and washed several times with DCM. The combined organic fractions were dried (Na2SO4), concentrated under vacuum and used directly without further purification (˜100 mg, quant.): LC-MS (ES) m/z=209 (M+H)+.
