Bis(triarylmethylium)-Mediated Diaryl Ether Synthesis:Oxidative Arylation of Phenols with N,N-Dialkyl-4-phenylthioanilines

摘要

Diaryl ethers constitute an important class of compounds in medicinal and agricultural chemistry,exemplified by the vanco-mycin family.The classical Ullmann ether synthesis,copper(I)-mediated coupling between phenols and aryl halides,has been extensively used for the preparation of diaryl ethers;however,harsh reaction conditions at high temperatures for long hours have severely limited its utility.Recently,several improved methods have been reported for the Ullmann synthesis that use ionic liquidsor catalysts,such as copper-phenanthroline complexes,a 1,3-diketone,5 or an amino acid.Moreover,palladium-catalyzed coupling reactions using electron-rich bulky phosphine ligands and SNAr-based reactions of aryl fluorides or metal-arene complexes have been employed for diaryl ether formation.