Selective Synthesis of ortho-Substituted Diarylsulfones by Using NHC-Au Catalysts under Mild Conditions.

A single-step gold(I)-catalyzed chemoselective protocol to access ortho-substituted diarylsulfones has been established. Acenaphthoimidazolylidene gold complexes are effective catalysts for the arylsulfonylation of boronic acids by potassium metabisulfite (K2S2O5) and diaryliodonium salts to access (poly-) ortho-substituted diarylsulfones even in gram scale. Unlike the transition metal-catalyzed two-component coupling systems, the sterically hindered aryl groups in diaryliodonium salts are preferentially transferred over less bulky ones to form synthetically difficult targets, including those of pharmaceutical importance.