2-Thiophenecarbonyl chloride → Tert-butyl 4-(5-(2-thienyl)-1,2,4-oxadiazol-3-yl)piperazine-1-carboxylate

Participants

Reaction Steps

To a cold (0° C.) solution of tert-butyl 4-[(hydroxyamino)(imino)methyl]piperazine-1-carboxylate (8 g, 32.7 mmol) in anhydrous DCM (150 mL) was added thiophene-2-carbonyl chloride (4.8 g, 32.7 mmol) followed by DIEA (7.2 mL, 39.2 mmol). The reaction mixture was stirred at RT for 12 hours and then filtered. The filtrate was evaporated and the residue was refluxed in pyridine (100 mL) for 3 hours. The solvent was removed under vacuum and the residue was dissolved in DCM. The organic layer was washed with a 10% aq. solution of sodium bicarbonate, water, brine and dried. The solvent was concentrated and the residue was purified by chromatography (Pet. Ether/EtOAc 7/3) to give 2.2 g (20%) of The title compound as a solid. TLC—Pet ether/EtOAc (9/1): Rf=0.75. HPLC purity>97%.

Provenance & Evidence