Ethyl Bromide → Benzyl 4-{[(3R)-1-ethylpiperidin-3-yl]methyl}piperazine-1-carboxylate

Benzyl 4-[(3R)-piperidin-3-ylmethyl]piperazine-1-carboxylate (1.8 g), bromoethane (1.3 ml) and potassium carbonate (3.9 g) was refluxed in acetone (50 ml) for seven hours. The reaction mixture was allowed to cool to room temperature then filtered. The filtrate was concentrated in vacuo and the resulting oil separated between dichloromethane (100 ml) and water (100 ml). The dichloromethane layer was separated, dried over magnesium sulphate, filtered then concentrated in vacuo onto silica gel (5 g). The resulting powder was subjected to chromatography on silica gel (50 g) using a gradient of 100% dichloromethane through to 20% methanolic ammonia in dichloromethane to give the title compound (352 mg).