Azobisisobutyronitrile → HCID 83909193, compound

A mixture of 4-(4-fluorophenyl)-5-methyl-1,2,3-thiadiazole (6.19 g), N-bromosuccinimide (12.4 g), 2,2′-azobis(isobutyronitrile) (100 mg) and carbon tetrachloride (100 ml) was stirred for 6 hrs. with heating under reflux. The reaction mixture was washed with water, dried over anhydrous magnesium sulfate and concentrated. Sodium acetate (30 g) and acetic acid (100 ml) were added to the residue and the mixture was stirred for 12 hrs. with heating under reflux. 6N Hydrochloric acid (50 ml) was added and the mixture was further stirred for 1 hr. with heating under reflux. The reaction mixture was concentrated, poured into a saturated aqueous sodium hydrogen carbonate solution and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated. The residue was subjected to silica gel column chromatography to give 4-(4-fluorophenyl)-1,2,3-thiadiazole-5-carbaldehyde (360 mg, yield 5.4%) as pale-yellow crystals from a fraction eluted with hexane-ethyl acetate (2:1, v/v).