Ethyl 4-piperidinecarboxylate → 1-(2-tert-Butoxycarbonylamino-thiazol-5-ylmethyl)-piperidine-4-carboxylic acid ethyl ester

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Reaction Steps

To a single necked round bottom flask (5-Formyl-thiazol-2-yl)-carbamic acid tert-butyl ester (1 g, 4.38 mmol) was dissolved in 20 ml methanol. To it piperidine-4-carboxylic acid ethyl ester (2.02 ml, 13.15 mmol) and 4-drops of glacial acetic acid was added and reaction mixture was stirred at room temperature for 2.5 hr. To it sodium cyanoborohydride (550 mg, 8.76 mmol) was added in portions and stirred for 12 hrs. Methanol was removed under reduced pressure using rotavapour. The residue was taken in water (15 ml) and ethyl acetate (25 ml), layers were separated, and aq. layer was re-extracted with ethyl acetate (25 ml). The combined organic layer was washed with brine (25 ml) and dried over anhydrous sodium sulfate. Solvent was evaporated on rotavapour, to get the yellow solid product. The crude material was purified by silica-gel column chromatography, eluting with 30-50% ethyl acetate in hexane. (0.98 g, 60% yield).

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