Guiding nitrenes away from a migration Nitrogen conventionally shares its electrons in three bonds with one or more partners. A singly bonded nitrogen, or nitrene, is exceptionally reactive and can insert itself into normally inert C–H bonds. If the nitrene forms next to a carbonyl center, though, it tends to react with the C–C bond on the other side instead. Hong et al. used theory to guide the design of an iridium catalyst that inhibits this rearrangement, steering the nitrene toward C–H insertion to form a variety of useful lactam rings. Science, this issue p. 1016 Theory guides design of a catalyst to cyclize amides via a nitrene intermediate otherwise prone to a competing rearrangement. Intramolecular insertion of metal nitrenes into carbon-hydrogen bonds to form γ-lactam rings has traditionally been hindered by competing isocyanate formation. We report the application of theory and mechanism studies to optimize a class of pentamethylcyclopentadienyl iridium(III) catalysts for suppression of this competing pathway. Modulation of the stereoelectronic properties of the auxiliary bidentate ligands to be more electron-donating was suggested by density functional theory calculations to lower the C–H insertion barrier favoring the desired reaction. These catalysts transform a wide range of 1,4,2-dioxazol-5-ones, carbonylnitrene precursors easily accessible from carboxylic acids, into the corresponding γ-lactams via sp3 and sp2 C–H amidation with exceptional selectivity. The power of this method was further demonstrated by the successful late-stage functionalization of amino acid derivatives and other bioactive molecules.

中文翻译：

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通过定制铱催化剂实现的 C-H 酰胺化选择性形成 γ-内酰胺

引导氮烯远离迁移 氮通常与一个或多个伙伴以三个键共享其电子。单键氮或氮烯具有异常的反应性，可以将自身插入通常惰性的 C-H 键中。但是，如果氮烯在羰基中心旁边形成，它往往会与另一侧的 C-C 键反应。洪等人。使用理论来指导抑制这种重排的铱催化剂的设计，引导氮烯向 C-H 插入以形成各种有用的内酰胺环。科学，这个问题 p。1016 理论指导设计催化剂以通过氮烯中间体环化酰胺，否则容易发生竞争性重排。金属氮烯分子内插入碳氢键形成γ-内酰胺环传统上受到异氰酸酯竞争形成的阻碍。我们报告了应用理论和机理研究来优化一类五甲基环戊二烯基铱 (III) 催化剂以抑制这种竞争途径。密度泛函理论计算表明，将辅助双齿配体的立体电子特性调节为更多的电子供体，以降低有利于所需反应的 C-H 插入势垒。这些催化剂可通过 sp3 和 sp2 C-H 酰胺化以优异的选择性将各种 1,4,2-二恶唑-5-酮、羰基硝基苯前体从羧酸中容易地转化为相应的 γ-内酰胺。氨基酸衍生物和其他生物活性分子的成功后期功能化进一步证明了这种方法的威力。