4-Chloro-N-(1,1-dimethyl-2-propynyl)benzamide → 2-(4-Chlorophenyl)-4,5-dihydro-4,4-dimethyl-5-methyleneoxazole

A round bottom flask was charged with N-(3-methylbutyn-3-yl)-4-chlorobenzamide (4.5 g, 19.09 mmol), copper(I) chloride (9.5 mg, 0.5 mol %), and n-butyl acetate (20 mL). The resulting mixture was heated to 95° C. for 4 h, then cooled to room temperature. The reaction was washed with 1 M hydrochloric acid solution and with water. The organic layer was dried over anhydrous sodium sulfate. The solvent was removed by evaporation under reduced pressure, and the residue was dried in a vacuum oven to afford 2-(4-chlorophenyl)-4,4-dimethyl-5-methyleneoxazoline (4.24 g, 94% yield) as a pale yellow oil (bp 95° C., 0.6 mm Hg).