Pyridine → (S)-4-benzyl-2-(2-methanesulfonyloxy-ethyl)piperazine-1-carboxylic acid tert-butyl ester

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Reaction Steps

To a solution of (S)-4-benzyl-2-(2-hydroxyethyl)piperazine-1-carboxylic acid tert-butyl ester (4.87 g, 15.2 mmol) in dichloromethane (200 mL), add pyridine (1.84 mL, 22.8 mmol) followed by methanesulfonyl chloride (1.29 mL, 16.7 mmol). Stir at room temperature overnight, then dilute with saturated aqueous sodium bicarbonate. Extract three times with dichloromethane; dry combined organic extracts over sodium sulfate, filter and concentrate in vacuo to give a brown residue. Redissolve residue in dichloromethane and apply to a plug of silica gel. Wash plug with 5% 2N ammonia-methanol in dichloromethane to obtain (S)-4-benzyl-2-(2-methanesulfonyloxy-ethyl)piperazine-1-carboxylic acid tert-butyl ester (3.74 g, 62%) as a yellow-brown thick oil.

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