4,5-Dichlorophthalic anhydride → 5,6-Dichloro-3H-isobenzofuran-1-one

Participants

Reaction Steps

NaBH4 (5.2 g) was added to a stirred solution of 4,5-dichlorophthalic anhydride (20 g) in anhydrous DMF (100 mL) at 0° C. under nitrogen in small portions over 1 hour. The reaction was warmed to room temperature for a further 2 hours and poured into ice/1M HCl. The resultant white precipitate (4,5-dichloro-2-hydroxymethyl-benzoic acid) was collected by filtration and dried under vacuum. The precipitate was suspended in toluene (200 mL) with catalytic p-toluenesulfonic acid and heated to reflux under Dean-Stark conditions (precipitate dissolves on heating) for 18 hours. The reaction was cooled to room temperature and the resultant white precipitate collected by filtration to give the sub-title compound as a white solid (14.0 g, 75%). 1H NMR (400 MHz, d6-DMSO) δ 5.40 (2H, s), 8.05 (1H, s), 8.15 (1H, s) ppm.

Provenance & Evidence