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To a solution of 4-chloro-N-methyl-benzamide (3.1 g) in THF (30 mL) was added n-butyl lithium (30.1 mL of 2.5M hexane solution) and the solution refluxed for 45 min. The solution was then cooled to 0° C. and N-methylformanilide (9.27 mL) added dropwise over 2 min. The solution was then refluxed for 2 h and then cooled to ambient temperature, water (80 mL) added and the solution acidified to pH 1 with 2M HCl. The solution was then extracted three times with ethyl acetate (3×50 mL), washed with brine (20 mL), dried (MgSO4) and concentrated in vacuo. The resulting brown oil was purified on silica by flash chromatography to afford the sub-titled product as a pale yellow solid (2.13 g; 59%); 1H NMR (400 MHz, CDC13) δ 2.90 (3H, s), 4.25 (1H, d) 5.60 (1H, d), 7.35 (2H, s), 7.60 (1H, s).

1. temperaturethe solution refluxed for 45 min
2. temperatureThe solution was then refluxed for 2 h
3. temperaturecooled to ambient temperature
4. extractionThe solution was then extracted three times with ethyl acetate (3×50 mL)
5. washwashed with brine (20 mL)
6. dry with materialdried (MgSO4)
7. concentrationconcentrated in vacuo
8. customThe resulting brown oil was purified on silica by flash chromatography