Reaction Steps
n-BuLi (2.5 mL of a 2.5 M solution in hexane, 6.23 mmol) was added dropwise with stirring to a solution of 6 (1.51 g, 5.93 mmol) in THF (9.5 mL) at −78° C. under argon. After 30 min a solution of trimethylborate (0.7 mL, 5.93 mmol) in THF (2 mL) was added and the mixture stirred for 1.5 h; thereafter, the resulting yellow solution was quenched with TMSCl (0.75 mL, 5.93 mmol) and allowed to reach rt. After 1 h (+)-pinanediol (1.01 g, 5.93 mmol) dissolved in a minimum amount of anhydrous Et2O was added one portion to the solution, and then stirred overnight. The reaction mixture was partitioned in Et2O (16 mL) and H2O (10 mL) and the aqueous phase extracted with Et2O (2×10 mL). The combined organic phases were dried on MgSO4, filtered and concentrated to give an orange oil, which was purified by chromatography (7:3 EtPet/EtOAc) and crystallization (EtPet), affording 7 (1.14 g, 54%) as a white crystalline solid, mp 98-101° C., [α]D=+11.2 (c 1.5, CHCl3). IR (KBr): 1646 cm−1. 1H NMR (CDCl3): δ 0.81 (3H, s, pinanyl CH3), 1.22 (1H, d, J=10.5 Hz, pinanyl Hendo), 1.33 (3H, s, pinanyl CH3), 1.40 (6H, s, 2CH3), 1.50 (3H, s, pinanyl CH3), 1.5-2.5 (5H, m, pinanyl protons), 4.22 (2H, s, CH2O), 4.47 (1H, dd, J=8.8, 2.0 Hz, pinanyl CHOB), 7.43 (1H, t, J=7.7 Hz, H5 arom.), 7.92 (1H, dt, J=7.7, 1.5 Hz, H6 arom.), 8.05 (1H, dt, J=7.7, 1.5 Hz, H4 arom.), 8.43 (1H, br s, H2 arom.). 13C NMR (CDCl3): δ 24.4, 26.9, 27.5, 28.8 (2C), 29.1, 35.9, 38.6, 40.0, 51.9, 68.0, 78.8, 79.5, 86.8, 128.1, 131.2, 135.0, 137.8, 162.5, (CB and aromatic quaternary C not seen). EI-MS: m/z 353 (M+), 338 (base peak), 323, 282, 242, 202, 186, 130, 103, 67, 55. Anal. Calcd for C21H28NO3B: C, 71.39; H, 7.99; N 3.96. Found: C, 71.01; H, 8.65; N, 3.89.
