To a solution of starting amine (1 mmol) in dichloromethane (5 mL) at rt are added 1,3-bis(tert-butoxycarbonyl)thiourea (1.05 mmol) and triethylamine (3 mmol). Under stirring, copper(II) chloride (1.05 mmol) is added and the reaction is stirred at rt until adjudged complete by TLC analysis. The reaction is diluted with EtOAc (30 mL) and filtered through a pad of celite. The filtrate is washed with brine (30 mL) and water (30 mL) and dried using anhydrous MgSO₄. Filtration and removal of solvent under reduced pressure yields a residue which is purified by silica gel chromatography using gradient elution (hexane : EtOAc). Removal of solvents under vacuum affords the product.