Trimethylboroxine → Methyl 3,4-dimethylthiophene-2-carboxylate

A solution of methyl 3-iodo-4-methylthiophene-2-carboxylate (400 mg, 1.418 mmol), trimethylboroxine (793 μL, 5.67 mmol) and 1,1′-bis(di-tert-butylphosphino)ferrocene palladium dichloride (92 mg, 0.142 mmol) in THF (2363 μL) was degassed by bubbling N2 through the solution. 1N aq. K2CO3 (2363 μL) was added and N2 was bubbled through the mixture for 30 s. The mixture was subjected to microwave irradiation in a sealed tube at 120° C. for 30 min. The reaction mixture was filtered through a plug of silica, eluted with EtOAc and the filtrate was washed with 1N aq. NaOH (2×), dried (Na2SO4) and concentrated in vacuo to afford the crude product. This was purified by flash chromatography (Biotage Horizon, 25M, Si, ˜20 mL/min, 100% hexanes for 144 mL, gradient to 10% EtOAc in hexanes over 1140 mL) to afford methyl 3,4-dimethylthiophene-2-carboxylate.