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Ketyl radical reactivity via atom transfer catalysis
Science ( IF 56.9 ) Pub Date : 2018-10-11 , DOI: 10.1126/science.aau1777
Lu Wang 1 , Jeremy M. Lear 1 , Sean M. Rafferty 1 , Stacy C. Fosu 1 , David A. Nagib 1
Affiliation  

Iodine smooths the way to ketyl radicals Chemists typically transform carbonyl compounds through polar two-electron reactions. It is also possible to pursue radical coupling strategies by adding just one electron to form a ketyl group. However, the strong reductant supplying that electron often limits the reaction's versatility. Wang et al. report a mild means of forming ketyls by first adding acetyl iodides across the C=O bond (see the Perspective by Blackburn and Roizen). A photoactivated manganese catalyst then temporarily pulls the iodine away, leaving a ketyl to couple with alkynes. The iodine then returns to one of the alkyne's carbons, stabilizing the product but remaining poised for further transformations. Science, this issue p. 225; see also p. 157 Adding acetyl iodide across carbonyls offers easy access to ketyls via transient I atom abstraction by a manganese catalyst. Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals. The in situ conversion of aldehydes to α-acetoxy iodides lowers their reduction potential by more than 1 volt, allowing for milder access to the corresponding ketyl radicals and an oxidative termination event. Upon subjecting these iodides to a dimanganese decacarbonyl precatalyst and visible light irradiation, an atom transfer radical addition (ATRA) mechanism affords a broad scope of vinyl iodide products with high Z-selectivity.

中文翻译:

通过原子转移催化的羰基自由基反应性

碘为酮基自由基铺平道路 化学家通常通过极性双电子反应转化羰基化合物。也可以通过仅添加一个电子来形成羰基来追求自由基偶联策略。然而,提供电子的强还原剂通常限制了反应的多功能性。王等人。报道了一种通过首先在 C=O 键上添加乙酰碘来形成酮基的温和方法(参见 Blackburn 和 Roizen 的观点)。然后光活化的锰催化剂暂时将碘带走,留下一个与炔烃结合的羰基。然后碘返回到炔烃的碳之一,稳定产物但仍为进一步转化做好准备。科学,这个问题 p。225; 另见第。157 在羰基化合物上添加乙酰碘可通过锰催化剂的瞬态 I 原子提取轻松获得酮基。将羰基单电子还原为酮基,可以访问该基石官能团的极性反转反应平台。然而,羰基自由基的合成效用受到其生成所需的强还原剂的阻碍,这也限制了其对净还原机制的反应性。我们报告了一种用于净氧化还原中性生成和羰基自由基反应的策略。醛到 α-乙酰氧基碘化物的原位转化使它们的还原电位降低了 1 伏以上,从而可以更温和地获得相应的羰基自由基和氧化终止事件。在对这些碘化物进行十羰基二锰预催化剂和可见光照射后,
更新日期:2018-10-11
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