Reaction Steps
n-Butyllithium (2.5 M soln in hexane, 4.66 mL, 11.64 mmol) was added dropwise to a stirred solution of (+)-pinanediol benzeneboronate 12a (Morandi, F. et al., J. Am. Chem. Soc. 2003, 125, 685-695) (2.48 g, 9.70 mmol) and bromochloromethane (0.95 mL, 14.55 mmol) in THF (25 mL) at −80° C. under argon atmosphere. The mixture was allowed to reach room temperature overnight. Then the solution was partitioned between light petroleum (80 mL) and water (25 mL), the organic phase was washed with saturated ammonium chloride (20 mL) and the combined aqueous phases were extracted with petroleum ether (2×40 mL). The organic phases were dried, filtered and concentrated and the crude residue was purified by gradient chromatography (light petroleum to light petroleum/ethyl ether 95:5), affording 13a as a colorless oil (2.33 g, 89% yield). [α]D+14.2 (c 2.0, CHCl3). 1H-NMR (200 MHz, CDCl3): δ 0.87 (3H, s, pinanyl CH3), 1.10 (1H, d, J 10.8, pinanyl Hendo), 1.30 (3H, s, pinanyl CH3), 1.41 (3H, s, pinanyl CH3), 1.62-2.39 (5H, m, pinanyl protons), 2.37 (2H, s, BCH2), 4.30 (1H, dd, J 8.8, 1.9, CHOB), 7.10-7.31 (5H, m, HAr). 13C-NMR (50 MHz, CDCl3): δ 19.3 (CB), 24.0, 26.4, 27.1, 28.6, 35.5, 38.1, 39.5, 51.3, 78.0, 85.8, 124.8, 128.3, 128.9, 138.8. EI-MS: m/z 217 (M++1, 2%), 270 (M+, 81%), 269 (M+−1, 21%), 255 (32), 229 (24), 214 (32), 201 (88), 200 (33), 187 (30), 179 (28), 174 (100), 135 (58), 134 (38), 119 (32), 118 (26), 117 (28), 109 (24), 93 (44), 91 (74), 83 (75), 82 (32), 81 (34), 79 (24), 77 (26), 67 (66), 65 (27), 55 (47), 53 (29). Anal. Calcd. for C17H23BO2: C, 75.57; H, 8.58. Found: C, 75.39; H, 8.44.
