Ammonium Chloride → (3R,5S)-1-Benzyl-3,5-dimethylpiperidin-4-one

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Reaction Steps

The crude cis:trans mixture of 1-benzyl-3,5-dimethylpiperidin-4-one (typically 6:1 cis:trans) (45 g) was added to a 5% solution of sodium methoxide in methanol (500 mL) and stirred at room temperature for 6 hours. Saturated aqueous ammonium chloride (30 mL) was added and the mixture stirred for a further 30 minutes at room temperature. The mixture was evaporated to dryness and then redissolved in dichloromethane (500 mL). The insoluble solids were filtered off and the solvent was then evaporated to give an enriched mixture 96:4 cis:trans by 1H NMR (quantitative mass recovery). Longer reaction times did not give any further enrichment. If required, pure cis-product could then be obtained by chromatographic purification as described above.

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