Azobisisobutyronitrile → 4-(Bromomethyl)-2,5-difluoro-N-(methylsulfonyl)benzamide

Participants

Reaction Steps

A stirred mixture of 2,5-difluoro-4-methyl-N-(methylsulfonyl)benzamide (Preparation 244, 5.07 g, 20.3 mmol), N-bromosuccinimide (freshly recrystallised and dried, 4.71 g, 26.4 mmol) and azobisisobutyronitrile (0.05 g, 0.30 mmol) in 1,2-dichloroethane (100 mL) was heated at reflux under nitrogen whilst being irradiated with light from a lamp. After 2 hours, additional azobisisobutyronitrile (0.05 g, 0.30 mmol) was added and the reaction heated under reflux for 2 hours more. The reaction mixture was cooled to room temperature and evaporated in vacuo. The resulting residue was partitioned between brine (200 mL) and EtOAc (2×150 mL). The combine organic extracts were dried over magnesium sulphate and concentrated in vacuo to yield a pale yellow oil which solidified on standing (7.88 g). The solid was purified by silica gel chromatography eluting with 0 to 30% EtOAc in heptane to afford the title compound as a white solid (3.71 g, 56%):

Provenance & Evidence