Oxidation ofo-Methoxyphenols with a Hypervalent Iodine Reagent: Improved Synthesis of Asatone and Demethoxyasatone

Oxidative Dearomatization of Phenols: Why, How and What For?

“…For example, simple 6,6-dimethoxycyclohexa-2,4-dienones, which can be easily generated by oxidative dearomatizing methoxylation of 2-methoxyphenols using either Wessely 13,14 or Pelter [15][16][17][18] reaction conditions [i.e., lead tetraacetate or PIDA in MeOH], are often utilized in situ in the presence of an excess of a diene or dienophile in order to favor [4+2] cycloaddition with these reaction components. Although this experimental trick has been proven useful in many examples, 3,4 it really boded no good for our objective of expanding the chemistry of ortho-quinone monoketals beyond their participation in Diels-Alder reactions.…”

Mechanistic Insight into Phenol Dearomatization by Hypervalent Iodine: Direct Detection of a Phenoxenium Cation

“…Methoxy groups strongly stabilize the corresponding phenoxenium cation TMP-O + due to the delocalization of the positive charge on the ortho and para positions, which made clear detection possible . Similar reactions using methoxy-substituted phenols have been used for useful synthesis in the context of HVI reactions. − However, phenoxenium cations are not readily observed during HVI oxidation reactions when using less electron-rich phenols (vide infra), while the presence of a phenoxyl radical intermediate could be detected by UV–vis and EPR. Using spectroscopic and DFT methods, we explore possible mechanistic outcomes for the oxidation of a trimethoxy-substituted phenol with HVI.…”

Antitumor benzothiazoles. 13. (Diacetoxy)iodobenzene (DAIB) oxidation of 2-(4-hydroxy-3-methoxyphenyl)benzothiazole and related compounds in the presence of dienophiles

“…6 Although these compounds are often too unstable to isolate (in contrast to 2-acyloxy-2-alkoxy-3,5-cyclohexadieones) 3,7 their presence in the reaction mixture may be inferred by the isolation of their Diels-Alder dimers. 8,9 A number of recent publications have demonstrated that trapping OQMs, Our own interest in this chemistry stems from our efforts to understand both the role of oxidation of phenols in their biological activity and the routes by which they may be oxidised during bioactivating/deactivating processes. In this paper we have compared the DAIB oxidations of vanillin (5; R = CHO), and analogs with related EWG groups, with published information on similar oxidations of methyl vanillate (5; R = CO 2 Me).…”