Ammonia → 3-Chloro-4,4-dimethylpent-2-enal

Phosphorous oxychloride (18.77 mL, 200 mmol) was added dropwise to DMF (30.8 mL, 400 mmol) at 0-5° C. for 30 min. Pinacolone (10 g, 100 mmol) was added dropwise to the reaction mixture at the same temperature for 30 min. The mixture was allowed to rt and stirred for 2 h. The reaction mixture was poured into ice cold water and basified with ammonia solution. The solution was extracted with chloroform (3×200 mL) and the combined chloroform layer was washed with water, brine and dried over sodium sulfate. The solution was filtered and evaporated the solvent. The residue was chromatographed over silica gel column using hexane-EtoAc (97:3) as eluents to give the product as a pale green color oil (11.7 g, 80%).