Benzyl Bromide → (1S,4R)-2-benzyl-2-azabicyclo[2.2.1]hept-5-ene

Participants

Reaction Conditions

Reaction Steps

To a round bottom flask containing commercially available, (1S,4R)-2-azabicyclo[2.2.1]hept-5-en-3-one (2.0 g, 18.3 mmol), in THF (100 mL) at 0° C. was added a solution of LiAlH4 (1 M in THF, 40.3 mL, 40.3 mmol), and the reaction mixture was refluxed overnight. The reaction mixture was then cooled to 0° C. and carefully quenched by the dropwise addition of H2O (15 mL). Celite and solid Na2CO3 were added to the slurry and the reaction mixture was vigorously stirred at room temperature for 3 h. The slurry was then filtered and the solids washed with THF. Benzyl bromide (2.4 mL, 20.2 mmol) and an aqueous solution of Na2CO3 (3.2 g in 30 mL H2O) were added to the filtrate and the reaction mixture stirred at room temperature overnight. Upon completion of the reaction, the reaction mixture was extracted with EtOAc (3×). The combined organics were washed with H2O, brine, dried with MgSO4, filtered, and concentrated to provide crude (1S,4R)-2-benzyl-2-azabicyclo[2.2.1]hept-5-ene as a yellow oil, which was directly hydroborated according to the procedure of F. Carroll et al. [J. Med. Chem. 1992, 35, 2184-2191]. The crude alcohol was purified by silica gel chromatography (0-15% MeOH (with 5% NH4OH) in DCM) to give intermediate B-6 as a clear oil (2.66 g, 13.1 mmol, 71% over 3 steps). MS (ESI) mass calcd for C13H17NO, 203.1. m/z found 204.1 [M+H]+. 1H NMR (500 MHz, Chloroform-d) δ 7.39-7.28 (m, 4H), 7.26-7.21 (m, 1H), 4.18-4.09 (m, 1H), 3.76-3.66 (m, 2H), 3.06 (br. s, 1H), 2.51 (dt, J=9.0, 3.0 Hz, 1H), 2.44-2.35 (m, 2H), 1.90-1.81 (m, 1H), 1.68-1.53 (m, 2H), 1.38-1.30 (m, 1H).

Provenance & Evidence