Cobalt Macrocycle-Catalyzed Electrochemical Coupling Reactions

研究了偕二卤代化合物的电化学还原 亲电试剂的存在具有几个缺点 (poor化学选择性和立体选择性）用于合成 单取代和双取代的材料。 这个过程将是 用钴（I）大环络合物催化，包括 维生素B12，钴双水杨醛乙二胺，和 钴肟。 该策略是将钴物质减少到 反应性Co（I）状态，其预期经历快速的 在介质中与偕二卤化物氧化加成。 的 生成的加合物，一种Co（III）物质，将被原位还原， 排出所需的负碳离子与亲电试剂反应 在介质中。 实际上，钴大环将催化 将孪位卤化物还原成相应的 α-卤代碳负离子 预计催化过程将 发生在远高于立体和化学选择性比 直接电化学过程，并允许转换不 通过直接的过程是完全可能的。 此外，由 在氧化性的电位下进行电解， 发生了向Co（I）的加成但Co（III）加合物是稳定的， 将有可能通过热或化学反应制备自由基， 后者的光化学分解。 一些 合成应用，包括还原亲电 偕二卤代物上的取代（包括开链和 和环状体系），取代的环丙烷的合成， 芳烃和多环体系，以及基于 在这些原则下，将采取。这些原则将 可以进一步扩展到电催化生成 除烷基卤化物以外的基质中的碳负离子。 有机合成计划正在支持这项研究， 开发钴大环催化电化学偶联 反应. 这项研究将导致一个新的和新颖的路线， 合成有用的反应性中间体， 合成越来越复杂的物质， 经济

The electrochemical reduction of geminal dihalides in the presence of electrophilic reagents has several disadvantages (poor chemoselectivity and stereoselectivity) for the synthesis of mono-and bis-substituted materials. The process will be catalyzed with cobalt (I) macrocyclic complexes, including vitamin B12, cobalt bis-salicylideneethylenediamine, and cobaloximes. The strategy is to reduce the cobalt species to the reactive Co(I) state, which is expected to undergo rapid oxidative addition with a geminal dihalide in the medium. The resulting adduct, a Co(III) species, will be reduced in situ to eject the desired carbanion for reaction with an electrophile in the medium. In effect, the cobalt macrocycle will catalyze the reduction of the geminal halide to the corresponding alpha-halocarbanion. The catalytic process is expected to occur in far higher stereoselectivity and chemoselectivity than the direct electrochemical process, and permit conversions not possible at all by the direct process. Furthermore, by carrying out the electrolysis at potentials where oxidative addition to Co(I) takes place but the Co(III) adduct is stable, it will be possible to make radicals by thermal or photochemical decomposition of the latter. A number of synthetic applications, including reductive electrophilic substitution on geminal dihalides (including both open chain and cyclic systems), synthesis of substituted cyclopropanes, arenes, and polycyclic systems, and synthesis of alkenes, based on these principles, will be undertaken. These principles will be further extended to electrocatalytic generation of carbanions from substrates other than alkyl halides. The Organic Synthesis Program is supporting this research to develop cobalt macrocycle-catalyzed electrochemical coupling reactions. This research will lead to a new and novel route to synthetically useful reactive intermediates that can be used to synthesize the increasingly complex substances needed in our economy.