Toluene → tert-Butyl 4-[(6-ethoxy-1,3-benzothiazol-2-yl)sulfanyl]-1-piperidinecarboxylate

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Reaction Steps

To the mixture of tert-butyl 4-hydroxy-1-piperidinecarboxylate (2 g, 10 mmol), 6-ethoxy-1,3-benzothiazol-2-thiol (2.54 g, 12 mmol), triphenylphosphine (3.9 g, 15 mmol) and THF (60 ml) was dropwise added a solution of 40% diethyl azodicarboxylate in toluene (5.23 g, 15 mmol) under ice cooling over a period of 10 minutes. The mixture was stirred at room tmperature for 20 hours. The reaction mixture was concentrated under reduced pressure, and the concentrate was dissolved in ethyl acetate(50 ml). The organic layer was washed with aqueous solution of 0.5N-sodium hydroxide (30 ml) and saturated aqueous solution of sodium chloride (30 ml), successively, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The concentrate was subjected to flash column chromatography (silica gel 50 g, ethyl acetate/hexane=1/20 to 1/5), and the desired fraction was concentrated under reduced pressure. To the concentrate was added hexane (10 ml) and the precipitates were collected by filtration to give the titled compound (2.6 g, 6.5 mmol) as white powdery crystals.

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