Phosphorus pentachloride → (4-Cyanophenyl)methanesulfonyl chloride

5 g (22.83 mmol) of 4-cyanobenzylsulfonic acid, sodium salt, were moistened with approx. 20 ml of phosphoryl chloride after which 5.2 g (25.11 mmol) of PCl5 were added and the mixture was stirred for 15 min while being cooled with ice. The mixture was then heated at 80° C. for 4 h. After that, the mixture was poured onto ice and this fresh mixture was stirred vigorously for 30 min; the product then separated out on the ice as a white solid. After the ice had partially thawed, the mixture was filtered through a frit and the product/ice mixture which remained was washed several times with water. The crystals which remained were dried in vacuo and used directly for the next step in the synthesis.