Reactions with thioethoxide ion in dimethylformamide. I. Selective demethylation of aryl methyl ethers

Abstract

Recent methods for demethylating aryl methyl ethers have been briefly reviewed, especially methods involving the use of nucleophilic reagents. Sodium thioethoxide dissolved in N,N-dimethylformamide has been developed as a powerful new reagent for demethylating aryl methyl ethers cleanly and rapidly in high yield. The reaction conditions can be controlled so that aromatic bromo substituents or isolated olefinic bonds are unaffected. Of special interest has been the selective monodemethylation of the methyl ethers of di- and tri-hydric phenols, exemplified by the isolation in high yield of orcinol monomethyl ether, p-methoxyphenol, guaiacol, and phloroglucinol dimethyl ether from the respective fully O-methylated compounds. An exception was pyrogallol trimethyl ether which afforded pyrogallol 1-monomethyl ether in high yield.