S. Li, K. Lundquist, G. Stenhagen
1996
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Abstract
Acid treatment (refluxing with 0.1 M HBr in dioxane-water (9:1) for 4h) of 2-(4-hydroxy-3,5-dimethoxyphenyl)-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol gives 2-(4-hydroxy-3,5-dimethoxy-phenyl)-1-(4-hydroxy-3-methoxyphenyl)-1-propanone as a major reaction product. Analogously, 1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxy-3-methoxyphenyl)-1-propanone is the most prominent constituent in the reaction mixture obtained on acid treatment of 1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol. Both the 1,2-diaryl-1-propanones are formed on acid treatment of birch lignin and it could be concluded that they originate from about equal amounts of lignin structures corresponding to the two 1,2-diaryl-1,3-propanediols. HBr favours the formation of 1,2-diaryl-1-propanones from the 1,2-diaryl-1,3-propanediols while trans-4,4'-dihydroxy-3,3',5-trimethoxystilbene is obtained in very high yield when CH 3 SO 3 H is used as the catalyst.