(2S,5S)-2,5-dimethylpiperazine → (2s,5s)-1-(4-Bromo-alpha-(3-(tert-butyldimethylsilyloxy)phenyl)benzyl)-2,5-dimethylpiperazine

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Reaction Steps

The crude benzhydryl chloride (approx. 42 mmol) was combined with 9.55 g (84 mmol) of (+)-(2S,5S)-2,5-dimethylpiperazine, prepared from L-Ala-L-Ala-diketopiperazine (Bachem Chemicals, Philadelphia, Pa.) as described in J. Org. Chem. 50: 4909-13 (1985), and 30 mL of toluene and heated at reflux overnight under nitrogen. The toluene was removed under vacuum, and the residue was redissolved in diethyl ether and washed with 1.0 M sodium hydroxide followed by saturated aqueous sodium chloride. The ether solution was dried over sodium sulfate and the solvent removed to give a dark oil. The product was purified by chromatography on silica gel (Waters Prep 500) with 0.5-0.7% ethanol in dichloromethane with 0.1% triethylamine to give 8.01 g (39%) of (2S,5S)-1-(4-bromo-α-(3-(tert-butyldimethylsilyloxy)phenyl)benzyl)-2,5-dimethylpiperazine as a 1:1 mixture of diastereomers.

Provenance & Evidence