Dichloromethane → (-)-(2R,5S)-1-allyl-2,5-dimethylpiperazine

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Reaction Steps

A mixture of racemic 1-allyl-2,5-dimethylpiperazine (3.82 g, 24.8 mmol, Example 42, infra) and (+)-di-p-toluoyl-D-tartaric acid (9.55 g, 24.8 mmol) in absolute ethanol (40 mL) was heated to reflux and allowed to cool gradually to room temperature. After standing for one day the salt was collected by filtration, washed with ethanol and dried to give 11.0 g. This was recrystallized four times from absolute ethanol to give the salt (4.5 g, 68% of theoretical for one enantiomer) as a white solid. The salt (3.3 g, 6.1 mmol) was partitioned between 2N sodium hydroxide solution and dichloromethane. The dichloromethane phase was separated, the alkali washed twice with dichloromethane, and the combined dichloromethane phases were dried with magnesium sulfate and evaporated to give (-)-(2R,5S)-1-allyl-2,5-dimethylpiperazine, (0.92 g, 98% recovery from the salt), [α]D20 =-55.7° (ethanol, c=1.8).

Provenance & Evidence