Synthesis
General procedure for the synthesis of (E)-2-(ethoxycarbonyl)vinylboronic acid pinacol ester from pinacol ester of bis(boronic acid) and ethyl propiolate: CuCl (1.5 mg, 0.015 mmol), NaOt-Bu (2.9 mg, 0.03 mmol) and Xantphos ligand (8.7 mg, 0.015 mmol) were placed in a nitrogen protected and THF (0.45 mL) treated oven-dried Schlenk tubes. A solution of bis(pinacolato)diboron (127 mg, 0.5 mmol) in THF (0.3 mL) was added to the reaction mixture, followed by stirring for 30 min at room temperature. Next, α,β-alkyne genistein (0.5 mmol) and MeOH (40 μL, 1 mmol) were added. The reaction tube was washed with additional THF (0.2 mL), sealed and stirring was continued until complete consumption of the starting material was confirmed by TLC detection. Upon completion of the reaction, the mixture was filtered through a diatomaceous earth pad and concentrated. Finally, the target product was purified by silica gel column chromatography.
References
[1] Journal of Medicinal Chemistry, 2012, vol. 55, # 20, p. 8903 - 8925,23
[2] Organic and Biomolecular Chemistry, 2015, vol. 13, # 26, p. 7136 - 7139
[3] New Journal of Chemistry, 2018, vol. 42, # 21, p. 17346 - 17350
[4] Chemical Communications, 2008, # 6, p. 733 - 734
[5] Tetrahedron, 2012, vol. 68, # 17, p. 3444 - 3449
