Base‐Mediated O‐Arylation of Alcohols and Phenols by Triarylsulfonium Triflates

A mild and efficient protocol for O‐arylation of alcohols and phenols (ROH) by triarylsulfonium triflates was developed under transition‐metal‐free conditions. Various alcohols, including primary, secondary and tertiary, and phenols bearing either electron‐donating or electron‐withdrawing groups on the aryl rings were smoothly converted to form the corresponding aromatic ethers in moderate to excellent yields. The reactions were conducted at 50 or 80 °C for 24 h in the presence of a certain base and showed good functional group tolerance. The base‐mediated arylation with asymmetric triarylsulfonium salts could selectively transfer the aryl groups of sulfoniums to ROH, depending on their inherent electronic nature. The mechanistic studies revealed that the reaction might proceed through the nucleophilic attack of the in situ formed alkoxy or phenoxy anions at the aromatic carbon atoms of the C−S bonds of triarylsulfonium cations to furnish the target products. Transition‐metal‐free reactions of alcohols and phenols with triarylsulfonium triflates in the presence of CsOH gave a variety of O‐arylated products in moderate to excellent yields. The reaction proceeded under environmentally benign conditions and showed good functional group tolerance. The studies also suggested that the reaction might involve a nucleophilic substitution mechanism other than an aryne intermediate.