Phosphorus oxychloride → HCID 83410607, compound

Participants

Reaction Steps

(I14B): Phosphoryl trichloride (8.0 ml, 86 mmol) was added to a suspension of 3,5-dibromo-4-fluorobenzamide (11.27 g, crude, ˜22.7 mmol) in acetonitrile (400 ml) at room temperature. The reaction mixture was heated to reflux for 30 minutes. Additional Phosphoryl trichloride (8.0 ml, 86 mmol) was added and the mixture heated to reflux for an additional hour, then stirred at room temperature overnight. A precipitate had formed and was removed by filtration. (The product is well soluble in acetonitrile) The reaction mixture was evaporated to dryness, then partitioned between EtOAc and aq. NaHCO3 solution. The organic layer was washed one more time with aq. NaHCO3 solution, once with brine, then dried over MgSO4, filtered and evaporated to dryness. Purification by column chromatography on silica (gradient 100% hexanes to 25% DCM in hexanes). 3,5-dibromo-4-fluorobenzonitrile (7.5 g) was obtained. The material is (by 1H NMR and 19F NMR) a 76:17:7 mixture of 3,5-dibromo-4-fluorobenzonitrile (desired product), 2,3,5-tribromo-4-fluorobenzonitrile (over-bromination) and 2,5-dibromo-4-fluorobenzonitrile (wrong regio-isomere). The material was used without further purification in the next reaction.

Provenance & Evidence