3,4-DIMETHOXYPHENYLBORONIC ACID, PINACOL ESTER

Synthesis

The reaction of 1,2-dimethoxybenzene (69.9 mg, 0.506 mmol, 1.0 eq.) and bis(pinacolato)diboron (124 mg, 0.486 mmol, 0.96 eq.) was catalyzed by 2,2'-bipyridine (1.7 mg, 11 μmol, 2.2 mol%) and [IrCl(cod)]2 (2.3 mg, 3.4 μmol , 0.68 mol%) were catalyzed by a stirring reaction in heptane (2.5 mL) at 95 °C for 24 hours. After completion of the reaction, the reaction was cooled to room temperature and the reaction mixture was concentrated under reduced pressure and used directly in the next step of the reaction. Subsequently, S-(4-tolyl)-4-toluene thiosulfonate (2a) (69.1 mg, 0.248 mmol, 1.0 equiv), copper sulfate (2.0 mg, 13 μmol, 5.0 mol%), cesium fluoride (80.6 mg, 0.530 mmol, 2.1 equiv), and TMEDA (1.9 mg, 0.16 μmol, 6.6 mol%) were added to the above crude product, dissolved in methanol (2.5 mL) and stirred at 50 °C for 24 hours. After completion of the reaction, it was cooled to room temperature, filtered through a diatomaceous earth pad and the filtrate was concentrated under reduced pressure. The residue was dissolved with ethyl acetate (20 mL), washed sequentially with saturated aqueous sodium bicarbonate (20 mL x 2) and brine (20 mL), and dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure and purified by preparative TLC (n-hexane/ethyl acetate=10/1) to afford 3,4-dimethoxyphenyl 4-methylphenyl sulfide (3t) (39.7 mg, 61.4%) as a light yellow oil.

References

[1] Patent: WO2013/175415, 2013, A1. Location in patent: Page/Page column 46
[2] Journal of the American Chemical Society, 2015, vol. 137, # 7, p. 2665 - 2673
[3] Journal of the American Chemical Society, 2014, vol. 136, # 18, p. 6566 - 6569
[4] Journal of the American Chemical Society, 2002, vol. 124, # 3, p. 390 - 391
[5] Journal of the American Chemical Society, 2015, vol. 137, # 15, p. 5193 - 5198