Ketene → 3-Hydroxy-2-methyl-2-phenylpiperidine

Participants

Reaction Steps

The ketene of (a) above (3.2 g) was suspended in methanol under nitrogen and the temperature brought to -40° C. Sodium borohydride (0.3 g) was added portionwise. The mixture was stirred for 30 min and then concentrated in vacuo, azeotroping with tetrahydrofuran. Borane tetrahydrofuran complex (64 ml, 1.0M in tetrahydrofuran) was added and the mixture was heated at reflux overnight. The mixture was cooled and quenched carefully with methanol, and the mixture was then concentrated in vacuo. The resulting residue was dissolved in ethanol (100 ml) and potassium carbonate (4.2 g) was added. The mixture was heated at reflux for 12 h. The mixture was cooled and evaporated and the residue was extracted with ethyl acetate and water. The organic extract was washed with brine, dried (MgSO4) and evaporated to afford 3-hydroxy-2-methyl-2-phenylpiperidine as a white solid. 1H NMR (360 MHz, CDCl3) δ 7.79 (2H, d, ArH), 7.40 (2H, t, ArH), 7.15-7.19 (1H, m, ArH), 3.89 (1H, mc), 2.89-3.01 (2H, m), 1.67-1.91 (4H, m), 1.39 (3H, s, CH3).

Provenance & Evidence