Sulfonyl chlorides
Sulfonyl chlorides are chlorides of appropriate sulfonic acids.
Aryl sulfonyl chlorides are made industrially in a two-step, one-pot reaction from an arene and chlorosulfuric acid. They can be easily obtained from sulfinic acid by chlorination with thionyl chloride or phosphorus pentachloride. They are a powerful arylating agents for the C–C bonds formation through desulfitative cross-coupling reactions. In the laboratory, useful reagents for activation of hydroxy group include derivatives of benzene sulfonyl chloride (tosyl, brosyl, nosyl chlorides) and methyl sulfonyl (mesyl) chloride.
Alkyl sulfonyl chlorides ca be prepared by the Reed reaction (radical reaction of chlorine and sulfur dioxide under UV-radiation). These compounds react readily with nucleophiles, most notably alcohols and amines (Hinsberg reaction).