Mikhael Myriam, Adler Sophia A, Wengryniuk Sarah E
Temple University , Department of Chemistry , 1901 North 13th Street , Philadelphia , Pennsylvania 19122 , United States.
Org Lett. 2019 Aug 2;21(15):5889-5893. doi: 10.1021/acs.orglett.9b02018. Epub 2019 Jul 16.
The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ-iodanes (-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent () is readily synthesized from commercial PhI(OAc) and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
在复杂多元醇中实现醇的位点选择性和化学选择性官能团化仍然是一项艰巨的合成挑战。尽管在氧中心的选择性衍生化方面已经取得了重大进展，但将醇化学选择性氧化为相应羰基的研究仍相对较少。在环状体系中，轴向醇的选择性氧化已为人熟知，而互补的赤道面选择性氧化过程尚未见报道。在此，我们报道了氮配位（双）阳离子λ-碘烷（-HVIs）用于醇氧化的效用，以及它们对赤道面醇相对于轴向醇氧化的前所未有的选择性水平。反应条件温和，简单的吡啶配位试剂（）可由市售的PhI(OAc)轻松合成，既可以分离得到，也可以原位生成。在柔性的1,2-取代环己醇和刚性多元醇支架中均展示了构象选择性，为化学家提供了一种化学选择性氧化的新工具。
