Late-stage C-H functionalization and C-C/N coupling enabled by new strategies for electrochemically-controlled radical formation

项目摘要 这项拟议的研究旨在开发金属催化的C-C和C-N键形成方法 通过利用电化学对电子传递提供的独特控制来简化有机合成。 FER事件。特别是，这项工作将开发基于双催化剂系统的合成方法。一 催化剂是电化学活化的，以介导烷基自由基的形成，而第二种催化剂选择- 有效地激活互补底物以实现与电生自由基的偶联。 该计划的长期目标是在某种程度上将电化学确立为标准的合成策略 这是对光氧化还原催化与有机合成成功结合的补充：另一种双催化剂 一种依靠一种催化剂促进电子转移，另一种催化剂促进成键反应的体系。 拟议的研究依赖于多个科学领域的合并来开发下一代方法 在有机合成中。塞沃夫团队在合成方法论、机械-- 自然有机金属化学和均相电化学将导致新的合成策略 这既影响了新治疗剂的发现速度，也影响了新治疗剂的大规模合成。这些战略和 该提案的目标转型摘要如下： 目标1.发展与烷基亲电体的C-C和C-N偶联反应：电化学驱动 交叉偶联将使用双催化剂系统来开发，该系统允许每个衬底通过 独特的催化剂。将开发专用的电催化剂，以促进烷基生成烷基 卤化物或醚/环氧化物。自由基中间体将被辅助催化剂截取和功能化， 唯一的(I)活化芳基氯化物和醚形成烷基芳烃，(Ii)从高价碳-氮偶联。 或(Iii)利用手性非外消旋配体实现对映体选择性的C-C/N偶联。 目标2.发展C(SP3)-H键烷基化/芳基化和胺化：脂肪族C-H键的活化 通过直接从系留芳基上提取氢原子(HAA)完成。将生成芳基自由基 通过电还原Ni(II)芳基中间体形成易受影响的低价有机镍(I)络合物 对Ni-C键的均解。通过HAA从芳基定向基团到烷基侧链的自由基继电提供 进入C-X偶联的活化脂肪族部位。 目标3.发展羧酸的脱羧基功能化：两个互补中的第一个 将研究脉冲电解技术，使其能够在温和的电位下进行脱羧化 并与生成的烷基的选择性C-C/N/X催化剂兼容。第二种方法将利用 在温和电位下氧化时具有光活性的电催化剂。氧化物种的光激发 会瞬间产生一种高能氧化剂，可以影响氧化脱羧基形成烷基自由基。

Project Summary The proposed research seeks to develop metal-catalyzed C–C and C–N bond-forming methodologies that streamline organic synthesis by leveraging the unique control that electrochemistry provides over electron trans- fer events. In particular, this work will develop synthetic methodologies based on dual-catalyst systems. One catalyst is electrochemically activated to mediate the formation of alkyl radicals, while a second catalyst selec- tively activates the complementary substrate to effect coupling with the electrogenerated radicals. The long-term goal of this program is to establish electrochemistry as a standard synthetic strategy in a way that complements the successful integration of photoredox catalysis into organic synthesis: another dual-catalyst system that relies on one catalyst to promote electron transfer and a second to mediate bond-forming reactions. The proposed research relies on the merger of multiple scientific fields to develop next-generation methodologies in organic synthesis. The Sevov team has a unique combination of expertise in synthetic methodology, mecha- nistic organometallic chemistry, and homogeneous electrochemistry that will lead to new synthetic strategies that impact both the rate of discovery and large-scale synthesis of new therapeutic agents. These strategies and the targeted transformations of the proposal are summarized below: Goal 1. to develop C–C and C–N coupling reactions with alkyl electrophiles: Electrochemically-driven cross-coupling will be developed using a dual-catalyst system that allows each substrate to be activated by a distinct catalyst. Dedicated electrocatalysts will be developed that mediate formation of alkyl radicals from alkyl halides or ethers/epoxides. The radical intermediates will be intercepted and functionalized by co-catalysts that exclusively (i) activate aryl chlorides and ethers to form alkyl arenes, (ii) mediate C–N coupling from high-valent complexes to form amines, or (iii) utilize chiral nonracemic ligands to enable enantioselective C–C/N coupling. Goal 2. to develop C(sp3)–H bond alkylation/arylation and amination: Aliphatic C–H bond activation will be accomplished via directed H-atom abstraction (HAA) from a tethered aryl radical. Aryl radicals will be generated by electroreduction of Ni(II)aryl intermediates to form low-valent organonickel(I) complexes that are susceptible to Ni–C bond homolysis. Radical relay by HAA from the aryl directing group to the alkyl side-chain provides access to an activated aliphatic site for C–X coupling. Goal 3. to develop decarboxylative functionalization of carboxylic acids: The first of two complementary approaches will investigate pulsed-electrolysis techniques to enable decarboxylation at potentials that are mild and compatible with catalysts for selective C-C/N/X of the resulting alkyl radicals. A second approach will utilize electrocatalysts that are photoactive upon oxidation at mild potentials. Photoexcitation of the oxidized species will transiently generate a high energy oxidant that can effect oxidative decarboxylation to form alkyl radicals.