Abstract
Summary
Refluxing of trans–2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furan
with dioxane-water (9 : 1) in the presence of various acid catalysts led to the formation of 2-(3,4-dimethoxyphenyl)-
7-methoxy-3-methylbenzo[b]furan, the trans and cis forms of 2-hydroxy-3,3′4′-trimethoxystilbene
and cis–2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furan.
The proportions of the products were strongly dependent on the particular acid used as catalyst. HCl and
to a greater extent HBr favored the formation of the 2-arylbenzofuran (phenylcoumarone) while the
trans-stilbene derivative predominated in reaction products from the experiments with trifluoromethane
sulfonic acid as the catalyst. Isomerization of the starting material occurred, regardless of the nature of
the catalyst (small amounts of the cis-isomer formed). The number of phenylpropane units in spruce
lignin attached to an adjacent unit by a β−5 linkage was estimated to be 6–9% on the basis of 1H NMR
spectrometric measurements of the formation of phenylcoumarone structures on refluxing of milled wood
lignin from spruce with 0.1M HBr in dioxane-water (9 : 1).
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