Formation of Isoeugenol and Eugenol During the Cleavage of β-Aryl Ethers in Lignin by Alcohol-Bisulfite Treatment

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Abstract
Treatment of guaiacylglycerol- and guaiacylpropanediol-β-(2-methoxyphenyl) ethers at 160 C in 50 % alcohol containing magnesium bisulfite was found to cleave the β-aryl ether linkages in these compounds to form isoeugenol and/or eugenol in up to 60 % yield as well as comparable yields of guaiacol. The linkage in a nonphenolic model was not cleaved to a discernible extent. Both an alcohol and bisulfite were essential for this reductive cleavage which proceeded efficiently in ethanol and isopropanol but not efficiently in methanol, t-butanol or dioxane. Magnesium was a better base than sodium for the reaction. Coniferyl alcohol was proposed to be an intermediate compound of this cleavage reaction which reasonably explains the formation of isoeugenol and eugenol from wood during the alcohol bisulfite pulping process.
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