Acetic Acid → 4-(3-Bromo-phenyl)-1-methyl-piperidine hydrochloride

Participants

Reaction Conditions

Reaction Steps

A mixture of 4-(3-bromo-phenyl)-piperidine; hydrochloride (1.0 g, 3.6 mmol), 37% formaldehyde in water (3.7 mL, 120 mmol), Acetic acid (0.25 mL, 4.4 mmol) and methanol (20 mL) was stirred for 15 minutes at room temperature. The mixture was cooled to 10° C. in an ice/water bath. Sodium cyanoborohydride (3.0 g, 48 mmol) was added portionwise. A mild exotherm was noted. The mixture was stirred and warmed to room temperature over 18 hours. The mixture was poured into saturated aqueous ammonium chloride (200 mL) and stirred for 1 hour at room temperature. The mixture was extracted with dichloromethane (3×75 ml). The combined organic layers were dried over magnesium sulfate, filtered and evaporated to an oil. The residue was triturated in ether (200 mL) and filtered. The filtrate was evaporated to an oil (0.585 g). The oil was dissolved in ether and stirred. Hydrogen chloride (2.0M in ether, 2.0 mL) was added dropwise and stirred for 30 minutes. The precipitate was filtered and rinsed with ether. 4-(3-Bromo-phenyl)-1-methyl-piperidine hydrochloride was isolated as a crude white solid (0.432 g, 41%). 1H NMR (400 MHz, (D3C)2SO, δ, ppm): 10.52 (s, 1H), 7.47-7.41 (m, 2H), 7.37-7.21 (m, 2H), 3.52-3.41 (m, 2H), 3.10-2.95 (m, 2H), 2.85-2.78 (m, 1H), 2.75 (s, 3H), 2.15-2.78 (m, 4H). MS=254, 256 (MH)+.

Provenance & Evidence