High-turnover hypoiodite catalysis for asymmetric synthesis of tocopherols
High-turnover hypoiodite catalysis for asymmetric synthesis of tocopherols
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DOI：
10.1126/science.1254976
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发表时间：
2014-07-18
期刊：
影响因子：
56.9
通讯作者：
Ishihara, Kazuaki
中科院分区：
文献类型：
--
作者：
Uyanik, Muhammet;Hayashi, Hiroki;Ishihara, Kazuaki
生育酚及其类似物的多样生物活性激发了人们对开发其有效不对称合成路线的极大兴趣。在这里，我们报道了手性次碘酸铵盐催化γ-（2-羟基苯基）酮的高度化学和对映选择性氧化环化为2-酰基色满轴承季立体中心，作为生产生育酚的合成中间体。四丁基碘化铵和叔丁基过氧化氢的溶液的拉曼光谱分析揭示了原位生成的次碘酸盐作为不稳定的催化活性物种和三碘化物盐作为稳定的惰性物种。通过在碳酸钾碱存在下次碘酸盐和三碘化物之间的可逆平衡，实现了高性能的催化氧化系统（周转数接近200）。我们预计，这些发现将打开高周转氧化还原有机催化的发展进一步的前景。
The diverse biological activities of tocopherols and their analogs have inspired considerable interest in the development of routes for their efficient asymmetric synthesis. Here, we report that chiral ammonium hypoiodite salts catalyze highly chemo-and enantioselective oxidative cyclization of gamma-(2-hydroxyphenyl) ketones to 2-acyl chromans bearing a quaternary stereocenter, which serve as productive synthetic intermediates for tocopherols. Raman spectroscopic analysis of a solution of tetrabutylammonium iodide and tert-butyl hydroperoxide revealed the in situ generation of the hypoiodite salt as an unstable catalytic active species and triiodide salt as a stable inert species. A high-performance catalytic oxidation system (turnover number of similar to 200) has been achieved through reversible equilibration between hypoiodite and triiodide in the presence of potassium carbonate base. We anticipate that these findings will open further prospects for the development of high-turnover redox organocatalysis.