- Reactions of Methyl threo-2-Acetoxy-3-chloro-3-(4-methoxyphenyl)propanoate and Methyl cis-2,3-Epoxy-3-(4-methoxyphenyl)propanoate with 3,5-Dimethoxyphenol: Potential Routes to Flavan-3-ols
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Attempted syntheses of flavan-3-ols by reaction of either methyl threo-2-acetoxy-3-chloro-3-(4-methoxyphenyl)propanoate (3) or methyl cis-2,3-epoxy-3-(4-methoxyphenyl)propanoate (14) with 3,5-dimethoxyphenol failed to give the required aryl ethers.Products usually were derived from C-alkylation of the electron-rich phenol although reaction of the chloro acetate (3) with the phenoxide ion gave the furanone (5).The single-crystal X-ray structures of methyl 4-hydroxy-3-(4-methoxyphenyl)-2-(4-methoxyphenylmethyl)-5-oxo-2,5-dihydrofuran-2-carboxylate and cis-3-hydroxy-5,7-dimethoxy-4-(4-methoxyphenyl)-3,4-dihydro-2H-1-benzopyran-2-one have been determined.
- Brown, Roger. F. C.,Jackson, W. Roy,McCarthy, Tom D.,Fallon, Gary D.
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p. 1833 - 1843
(2007/10/02)
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- Some Novel Photochemical and Related Aryl Couplings and Migrations in Flavonoid Synthesis
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2'-Methoxymethoxy-4,4',6'-trimethoxychalcone epoxide couples at the β-position with 3,5-dimethoxyphenol under photolytic conditions to form isomeric 1,3,3-triaryl-2-hydroxypropiophenones.These propiophenones are subject to photo-induced α-ketol rearrangements yielding isomeric 1-hydroxypropan-2-ones.Together these serve as useful synthetic intermediates for 4-arylflavan-3-ones and novel 2-hydroxy-2-arylbenzylbenzofuran-3(2H)-ones and 4-aryl-3-hydroxy-3,4-cis-dihydrocoumarins.The same epoxide reacts ionically under ambient conditions with 2,4,6-trihydroxybenzoic acid to afford a 3-O-benzoylpropiophenone intermediate, which provides novel access to isoflavones in high overall yield.Analogous coupling of phloroglucinol to epoxycinnamates gives diastereoisomeric 3,3-diaryl-2-hydroxypropionates which serve as precursors for 3,4-trans- and 3,4-cis-4-aryl-3-hydroxydihydrocoumarins and thence for 3-aryl- and 3-hydroxycoumarins.
- Westhuizen, Jan H. van der,Ferreira, Daneel,Roux, David G.
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p. 2856 - 2865
(2007/10/02)
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