To a solution of methyl 5-chloro-4-iodo-2-thiophenecarboxylate (1.75 g, 5.8 mmol) in dioxane/H2O (50:5 mL) was added K2CO3 (3.4 g, 24.9 mmol), tetrakistriphenylphosphine Pd(0) (0.96 g, 0.83 mmol), and 5-(5,5-dimethyl-1,3,2-dioxaborinan-2-yl)-1-methyl-1H-pyrazole (3.4 g, 16.5 mmol). The reaction mixture was heated to 80° C. in a sealed tube for 15 h. The reaction solution was concentrated under vacuum and purified on silica gel (hexanes/EtOAc, 4:1) to give the title compound (0.35 g, 24%) as a yellow oil: LC-MS (ES) m/z=257 (M+H)+.
