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The general procedure for the synthesis of tert-butyl 3-alkynylpiperidine-1-carboxylate from dimethyl (1-diazido-2-oxopropyl)phosphonate and 1-Boc-3-piperidinecarboxaldehyde was as follows: a solution of dimethyl 1-diazido-2-oxopropylphosphonate (96 mg, 1.0 mmol) in methanol (2 mL) was slowly added dropwise to a stirred tert-butyl 3-formylpiperidine-1-carboxylate (107 mg, 0.50 mmol) and potassium carbonate (138 mg, 2.0 mmol) in a mixture of methanol (4 mL). The reaction was carried out at room temperature with continuous stirring for 3 hours. After completion of the reaction, the mixture was concentrated to dryness to give the crude product. The crude product was dissolved in ether (10 mL) and washed with saturated aqueous sodium bicarbonate (10 mL). The aqueous phase was back-extracted with ether (10 mL x 2), and all the organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated to give the crude product. The crude product was purified by silica gel column chromatography (12 g silica gel), and the eluent was a mixed solution of petroleum ether and ethyl acetate (the volume fraction of ethyl acetate was increased from 0% to 30% in a gradient, and the elution time was 20 min), and the final product was tert-butyl 3-ethynylpiperidine-1-carboxylate (90 mg, 86.1% yield), which was a colorless oil. Mass spectrometry analysis showed that the m/z of its molecular ion peak (M + Na)+ was 232.2.

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