2-(1-Benzothiophen-5-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

Synthesis

5-Bromobenzo[b]thiophene (49 g, 7.0 mmol) was dissolved in DMSO (40 mL). To this solution, bis(pinacolato)diboron (7 mmol), PdCl2(dppf)-CH2Cl2 (0.33 mmol) and KOAc (20 mmol) were added sequentially. After displacement of the reaction system with nitrogen, the reaction mixture was heated to 80 °C with stirring. After maintaining the reaction at this temperature for 3 h, the reaction mixture was cooled to room temperature. Water (66 mL) was added to the reaction mixture and the aqueous layer was subsequently extracted with EtOAc (3 x 66 mL). The organic layers were combined, dried with anhydrous Na2SO4, filtered and concentrated. Finally, purification by fast column chromatography (silica gel, 0-5% Et2O/pentane as eluent) afforded 2-(1-benzothiophen-5-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 1.56 g in 86% yield.

References

[1] Patent: WO2004/9086, 2004, A1. Location in patent: Page/Page column 49
[2] Patent: US2006/52378, 2006, A1. Location in patent: Page/Page column 104
[3] Journal of the American Chemical Society, 2017, vol. 139, # 24, p. 8267 - 8276
[4] Angewandte Chemie - International Edition, 2018, vol. 57, # 34, p. 10999 - 11003
[5] Angew. Chem., 2018, # 130, p. 11165 - 11169,5