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The general procedure for the synthesis of tert-butyl piperidine-1-carboxylate from hexahydropyridine and di-tert-butyl dicarbonate is as follows: hexahydropyridine (1 mmol) was added to a solution of ethanol (1 mL) containing magnetically stirred guanidine hydrochloride (15 mol%) and di-tert-butyl dicarbonate (1.2 mmol) and the reaction was stirred to completion at 35-40 °C (reaction progress was monitored by TLC or GC). Upon completion of the reaction, the ethanol is evaporated under vacuum and the residue is washed with water to remove the catalyst or dissolved in dichloromethane (or ethyl acetate) and filtered to separate the catalyst. If an organic solvent is used for post-treatment, the product is almost pure after evaporation of the organic solvent. If excess di-tert-butyl dicarbonate is used, the product can be washed with petroleum ether or hexane to recover the residual di-tert-butyl dicarbonate. If necessary, the product can be further purified by crystallization (using hexane and dichloromethane, or ether and petroleum ether as solvents) or silica gel column chromatography (ethyl acetate-hexane (1:6) as eluent).