In a sealable vessel, benzyl 4-(2-azidoacetyl)morpholine-2-carboxylate (0.096 g, 0.32 mmol) was suspended in t-BuOH (1 mL) and water (1 mL) was added. An aqueous solution of sodium ascorbate (1.0 M, 0.032 ml, 0.032 mmol) and an aqueous solution of copper(II) sulfate pentahydrate (0.30 M, 0.079 ml, 0.024 mmol) were added, followed by pent-1-yne (0.040 ml, 0.41 mmol). The vessel was sealed and placed in a 65 deg oil bath, whereupon the mixture was stirred for 14 h. The reaction mixture was cooled to RT, taken up in EtOAc (60 mL), and the organic layer was extracted with dilute sodium bicarbonate (5 mL), dilute brine (5 mL), and saturated brine (5 mL), then was dried over sodium sulfate and concentrated. The residue was purified through silica gel (25 mL) eluting with EtOAc, affording the title compound (105 mg, 0.28 mmol). MS m/z 373 (M+1).
