The synthesis of hydrogen-bonded xanthones by using biorenewable hydrogenated cardanol (3-pentadecylphenol) is described. Hydrogenated cardanol was initially converted into various hydroxybenzophenones. These benzophenones were converted into xanthones by utilizing an oxidative ceric ammonium sulfate-mediated reaction. A subsequent ruthenium-mediated late-stage oxidation of the xanthones provided hydrogen-bonded xanthones, which displayed good UVA and UVB absorbing properties.
Key steps in the synthesis of derivatives of the angucycline, tetrangulol include the use of a palladium catalyzed Suzuki-Miyaura cross-coupling reaction for the assembly of 2-(1,4dimethoxy-3-(2-methylprop-1-en-1-yl)naphthalen-2-yl)-3-methoxy-5-methylbenzaldehyde from 2-iodo-3-methoxy-5-methylbenzaldehyde and 2-(1,4-dimethoxy-3-(2-methylprop-1-en-1yl)naphthalen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. The biaryl product was then subjected to an iron-catalyzed ring-closing carbonyl-olefin metathesis reaction to afford 1,7,12trimethoxy-3-methyltetraphene, which was oxidized to the corresponding quinone. Late stage oxidation of the quinone with Ru[Cl 2 (p-cymene)] 2 and an oxidant unexpectedly afforded the chlorinated compounds, 2,4-dichloro-11-hydroxy-1-methoxy-3-methyltetraphene-7,12-dione and 2,4-dichloro-6-hydroxy-1-methoxy-3-methyltetraphene-7,12-dione.
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