Bosson Johann
Chemistry Department, Faculty of Sciences, Koç University, İstanbul, Turkiye.
Turk J Chem. 2023 Sep 26;47(6):1420-1428. doi: 10.55730/1300-0527.3624. eCollection 2023.
Xanthones comprise a large family of heterocycles displaying fascinating biological properties. Many synthetic protocols have been developed for the preparation of natural and nonnatural xanthone derivatives. Among them, condensation reactions between salicylic acid derivatives and phenol partners are highly desirable. Those reactions can be satisfactorily performed using Eaton's reagent (PO in CHSOH). Despite being highly effective with a variety of substrates, this approach presents limitations that depend on the electronic nature of the reaction precursors. The scope and limitations of the Eaton's reagent-mediated preparation of xanthones are herein presented and discussed. In short, this approach is limited to the utilization of very electron-rich phenol substrates (like phloroglucinol compounds), or to electron-rich phenol precursors (like resorcinol derivatives) via the isolation of benzophenone intermediates in this latter case. Electron-poor phenols are not amenable to this transformation with Eaton's reagent.
氧杂蒽类化合物构成了一类具有迷人生物学特性的杂环化合物大家族。人们已经开发出许多合成方法来制备天然和非天然的氧杂蒽衍生物。其中，水杨酸衍生物与酚类底物之间的缩合反应备受关注。使用伊顿试剂（PO在CHSOH中）可以顺利进行这些反应。尽管该方法对多种底物都非常有效，但这种方法存在一些局限性，这些局限性取决于反应前体的电子性质。本文介绍并讨论了伊顿试剂介导的氧杂蒽制备方法的适用范围和局限性。简而言之，这种方法仅限于使用电子密度非常高的酚类底物（如间苯三酚化合物），或者在后一种情况下，通过分离二苯甲酮中间体，使用电子密度高的酚类前体（如间苯二酚衍生物）。电子密度低的酚类不适用于伊顿试剂介导的这种转化反应。
