Dimethyl Sulfide → Dimethyl 2-pyrrolylsulfonium chloride

To a solution of N-chlorosuccinimide (40 g, 0.3 moles) in anhydrous dichloromethane (3 l), cooled to -30° to -40° C. and maintained in a nitrogen atmosphere, was added, with good stirring, α solution of dimethyl sulfide (20.5 g, 0.66 moles) in dichloromethane (125 ml) over a 1 hour period, the temperature being maintained at -30° to -40° C. After a further hour at this temperature, a solution of pyrrole (20 g, 0.3 moles) in dichloromethane (125 ml) was added over a 1 hour period maintaining a temperature of -30° to -40° C. The solution was stirred for a further 2 hours at -30° to -40° C. and then ether (ca 6 l) was added with strong agitation until the precipitation of the product was complete. The solid was collected by filtration, washed three times with ether and dried in vacuo to give a white solid of dimethyl 2-pyrrolylsulfonium chloride (40 g, 83%) which after crystallization from dichloromethane had mp 115°-116° C. dec.