2-Fluorobenzoic acid → 2-Fluoro-5-chlorosulfonylbenzoic acid

Participants

Reaction Conditions

Reaction Steps

5-(Chlorosulfonyl)-2-fluorobenzoic acid was prepared from 2-fluorobenzoic acid using a Biotage Initiator 8 microwave set to high absorbance as follows. Using conditions described, the reaction typically reached a pressure of 12 barr. The pressure was reduced to 3 barr after cooling and was vented prior to decapping the reaction vessel. To a 5 ml Biotage microwave reaction tube was added 2-fluorobenzoic acid (0.5 g, 3.57 mmol) and a Teflon covered magnetic stir-bar. To this was added 2 ml of chlorosulfuric acid. The vessel was capped and heated to 200° C. for 3.25 min. After cooling to room temperature, the remaining pressure was vented into a 50 ml syringe and discharged into 30 ml 1M NaOH. Reaction was quenched by adding dropwise to 30 ml of crushed ice. The solid product was collected by vacuum filtration, washed with water (5 ml, 3×) and air-dried under vacuum for 2 h, yielding 5-(chlorosulfonyl)-2-fluorobenzoic acid as a light yellow solid.

Provenance & Evidence