Triisopropyl borate → (2-(But-3-en-1-yl)phenyl)boronic acid

Participants

Reaction Steps

Ref Li, W., Nelson, D. P., Jensen, M. S., Hoerrner, R. S., Cai, D., Larsen, R. D., Reider, P. J. J. Org. Chem., 2002, 67, 5394-5397. A solution of 1-bromo-2-(but-3-en-1-yl)benzene (9.46 g, 44.8 mmol) in dry THF (44.8 ml) was cooled (−78° C.) and treated with 2.5 M n-BuLi in hexanes (19.7 ml, 49.3 mmol). The mixture was stirred for 20 min, and then treated with triisopropyl borate (51.5 ml, 224 mmol). After 90 min, the reaction mixture was warmed to room temperature over 1 h. Then, the reaction was quenched with 2.0 N aq. HCl (240 mL), diluted with Et2O (120 mL), and the layers were stirred vigorously for several minutes. The resulting white precipitate was removed by filtration and then the filtrate layers were separated. The organic layer was dried (Na2SO4), filtered, and concentrated, affording a pale yellow oil which partially solidified upon standing. These solids were triturated with hexanes and then dried under vacuum. The decantate was concentrated to an oil, dissolved in fresh hexanes (˜15 mL) and stored (−40° C.) for 16 h. A second crop of solid was collected, washing with a small volume of hexanes, and dried under vacuum Both crops were combined to afford the desired product (5.46 g, 31.0 mmol, 69.2% yield) as a white crystalline solid. 1H NMR (500 MHz, CDCl3) δ 8.24 (dd, J=7.8, 1.3 Hz, 1H), 7.52 (td, J=7.5, 1.4 Hz, 1H), 7.30-7.36 (m, 2H), 5.96 (ddt, J=17.0, 10.3, 6.5 Hz, 1H), 5.04-5.10 (m, 1H), 5.02 (dd, J=10.2, 1.6 Hz, 1H), 3.29-3.40 (m, 2H), 2.50 (td, J=7.9, 6.6 Hz, 2H). LCMS (M−H)=175.11.

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