Under argon atmosphere, ethyl 2-(tert-butoxy)-2-[2,5-dimethyl-4-(tetramethyl-1,3,2-dioxaborolan-2-yl)thiophen-3-yl]acetate (28f) (50 mg, 0.114 mmol), cyclohex-1-en-1-yl trifluoromethanesulfonate (29a) (27.7 mg, 0.120 mmol) and cesium carbonate (112.2 mg, 0.344 mmol) was dissolved in dry N,N-dimethylformamide (570 μL). The solution was degassed under argon and PdCl2(dppf) (5.6 mg, 0.007 mmol) was added. The reaction was heated and shaken at 100° C., for 6.5 hours. The mixture was filtered through Celite®, rinsed with ethyl acetate and dichloromethane. The solution was concentrated in vacuo and partitioned between ethyl acetate and water. The organic layer was washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure. The crude material was purified by preparative TLC (cyclohexane/ethyl acetate 90/01) to provide the desired product (30 mg, 0.09 mmol, 75%).
