Under argon atmosphere, sodium carbonate (18 mg, 0.169 mmol), water (1.1 mL) and iodobenzene (19 μL, 0.17 mmol) were added to a solution of ethyl 2-(tert-butoxy)-2-[2,5-dimethyl-4-(tetramethyl-1,3,2-dioxaborolan-2-yl)thiophen-3-yl]acetate (28f) (70 mg, 0.16 mmol) in N,N-dimethylformamide (3.4 mL). The solution was degassed under argon and palladium tetrakis(triphenylphosphine) (37 mg, 0.032 mmol) was added. The mixture was heated at 100° C. for 3 hours. The mixture was then cooled at room temperature, water was added and the aqueous layer was extracted with ethyl acetate. The organic layer was washed with brine, dried over sodium sulfate, filtered and evaporated under reduced pressure. The residue was purified by preparative TLC (cyclohexane/ethyl acetate 90/10) to afford the desired product ethyl (28g) (42 mg, 0.121 mmol, 75%).
