To a stirred solution of 4-{[3-(2-tert-butylphenoxy)azetidin-1-yl]carbonyl}benzonitrile (2.00 g, 6.00 mmol) in DMSO (5.0 mL) was added hydroxylammonium chloride (2.08 g, 30.0 mmol) and sodium hydrogen carbonate (2.52 g, 30.0 mmol) at 90° C. After 1 h the reaction mixture was partitioned between ethyl acetate and water and separated. The organic layer was washed with saturated sodium chloride, dried (Na2SO4), filtered and concentrated under reduced pressure. The residue was dissolved in THF (10.0 mL), added to a stirred solution of 1,1′-carbonylbis-1H-imidazole (1.07 g, 6.6 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene (1.07 g, 6.6 mmol) in THF (10.0 mL) and the resulting reaction mixture was stirred at room temperature for 2 h. Then, the reaction mixture was poured into 1N HCl water solution (150.0 mL) and extracted with ethyl acetate (2×100.0 ml). The combined organics were washed with water (2×150 mL), saturated sodium chloride (100 mL), dried (MgSO4), filtered, and concentrated under reduced pressure. The resulting mixture was washed with acetonitrile and diethyl ether to provide 3-(4-{[3-(2-tert-butylphenoxy)azetidin-1-yl]carbonyl}phenyl)-1,2,4-oxadiazol-5(4H)-one (1.40 g, 59%) as a colorless solid.
