ArSO2R

ArSO2R is a generic notation used in organic chemistry to denote a sulfone functional group in which an aryl group (Ar) is bonded to a sulfonyl group (-SO2-) that carries a second substituent (R) on sulfur. The general structure is Ar-SO2-R, with sulfur in the +6 oxidation state. Ar is typically an aromatic ring (for example phenyl or a substituted aryl such as p-tolyl), and R can be an alkyl, aryl, or other substituent. ArSO2R encompasses a family of sulfones, including sulfonyl chlorides (R = Cl) and aryl sulfonate esters (R = OR′).

Nomenclature and common instances. Benzenesulfonyl chloride (PhSO2Cl) and p-toluenesulfonyl chloride (TsCl) are classic examples of ArSO2Cl, where Ar is phenyl or p-tolyl, respectively. When the sulfonyl group bears an alkyl or other substituent, the motif is often described as a sulfone with one aryl and one additional substituent, for example Ar-SO2-R (R = aryl, alkyl, etc.). A related set of compounds are aryl sulfonate esters ArSO2OR′, formed when the arylsulfonyl group acts as a leaving group in substitution reactions. Sulfonamides are also related, having the ArSO2–NR2 connectivity.

Structure and properties. The sulfur atom is hexavalent and bonded to two oxygens via double bonds and to Ar and R. Sulfones are typically highly polar and chemically robust, showing stability to many acids and bases, though they can participate in a range of transformations when activated or under strong conditions.

Preparation and reactions. Sulfones can be prepared by oxidation of sulfides to sulfones using oxidants such as mCPBA, Oxone, or hydrogen peroxide. They can also be formed by coupling sulfonyl chlorides with nucleophiles to give symmetric or unsymmetric ArSO2R sulfones. The arylsulfonyl motif is widely used as a protecting or activating group in synthesis (tosyl, nosyl, and related derivatives) and as a leaving group in various substitution reactions.

Applications. ArSO2R groups serve as protecting groups for amines (tosylation, nosylation) and as versatile leaving groups in organic synthesis. Sulfone building blocks derived from ArSO2R are valuable in medicinal chemistry, materials science, and cross-coupling reactions.