The reactions of the β-aryl ether lignin model 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol on heating in aqueous solution have been studied. Guaiacol, isoeugenol, vanillin, 1-(4-hydroxy-3-methoxyphenyl)-1-ethanol, 1,2-bis(4-hydroxy-3-methoxyphenyl)-1-propanol, 2-(4-hydroxy-3-methoxyphenyl)-7-methoxy-3-methyl-2,3-dihydrobenzo[b]furan, dehydrodiisoeugenol and trans-1,2-dihydrodehydroguaiaretic acid were detected in the reaction mixtures. The formation of the products can
be envisioned to proceed via homolysis of an intermediate quinone methide. When 2,6-dimethoxyphenol
was present in the reaction mixtures large amounts of 1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxy-3-methoxyphenyl)-1-propanol were formed and the yields of guaiacol and isoeugenol were
comparatively high. The reaction product pattern can be explained by the occurrence of radical-exchange
reactions. The presence of wood meal in the reaction mixtures resulted in an increase in the yield of
isoeugenol and a lowering of the yield of dehydrodiisoeugenol. The changes in yields in this case can
also be explained by radical-exchange reactions. The significance of homolytic cleavage of β-aryl ether
linkages in connection with the technical processing of wood is discussed.
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
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).
Several chiral neolignan skeletons and a benzodioxane were prepared from a tartrate derivative with the
crucial chiral aryl alkyl ether formation being accomplished with cesium phenolate and 18-crown-6.
These compounds have greater than 96% enantiomeric excess, and this work represents the first successful
synthetic preparation of optically active 8-O-4′ type neolignan skeletons. The chiral aryl alkyl
ethers were also synthesized from several protected carbohydrates, which can serve as chiral auxiliaries
for a wide variety of target molecules.
Wood products with anti-electrostatic properties have
wide applications in many fields. However, wood is an
insulator and does not itself have anti-electrostatic ability.
This study investigated several ionic liquids as anti-electrostatic
agents for wood. Ionic liquids are liquids at room
temperature (or close to room temperature), possess no
vapor pressure and are excellent conductors for electric
current. Maple and pine veneers were either soaked in or
brushed with five ionic liquids: 1-butyl-3-methylimidazolium
hexafluorophosphate, 1-butyl-3-methylimidazolium chloride,
1-ethyl-3-methylimidazolium tetrafluoroborate and
1-ethyl-3-methylimidazolium hexafluorophosphate. The
ionic liquid-treated wood specimens were then measured
for surface resistivity and volume resistivity in accordance
with ASTM standards. The effects of application
method (brushed vs. soaked) and storage time were
investigated. All the ionic liquids studied were effective
anti-electrostatic agents for pine and maple. For all ionic
liquids tested, pine had lower resistivity, and thus higher
anti-electrostatic ability, than maple.
For a multivariate normally distributed n × p random matrix Y with mean μ and covariance ΣY = V1⊗Σ1 + V2⊗Σ2, necessary and sufficient conditions, under which Y′WY follows a Wishart distribution, are obtained, where W is a symmetric matrix, V1 and V2 are known nonnegative definite matrices, and Σ1 and Σ2 are unknown nonnegative definite parameter matrices. Several examples are given to illustrate our main results.