FeCl3/SiO2 Reacts as Oxidant or Lewis Acid with Phenol Ethers

Article abstract of DOI:10.1021/jo00335a045

Adsorption of FeCl3*6H2O onto silica gel produces a supported reagent FeCl3/SiO2.This reagent is insoluble in CH2Cl2 and is used in that solvent for reaction with phenol ethers.Dimethoxy aromatics are coupled to produce biaryls in high yield.Seven examples including both inter- and intramolecular couplings are reported.The effect of various support materials is explored.An electron-transfer mechanism is proposed.Disiloxy aromatics are oxidized to quinones.Ten examples of substituted 1,4-bis(trimethylsiloxy)- or 1,4-bis(tert-butyldimethylsilyloxy)benzene oxidations are reported.In one example the reaction is catalytic in FeCl3, being driven by oxygen.Benzyloxy aromatics are cleaved to phenols.In this reaction FeCl3 acts on a Lewis acid.The importance of coadsorbing the reagent and the aromatic ether in the absence of solvent is demonstrated.