Werth Jacob, Uyeda Christopher
Department of Chemistry , Purdue University , West Lafayette , IN 47907 , USA . Email:
Chem Sci. 2018 Jan 2;9(6):1604-1609. doi: 10.1039/c7sc04861k. eCollection 2018 Feb 14.
A [ PDI]CoBr complex (PDI = pyridine-diimine) catalyzes Simmons-Smith-type reductive cyclopropanation reactions using CHBr in combination with Zn. In contrast to its non-catalytic variant, the cobalt-catalyzed cyclopropanation is capable of discriminating between alkenes of similar electronic properties based on their substitution patterns: monosubstituted > 1,1-disubstituted > ()-1,2-disubstituted > ()-1,2-disubstituted > trisubstituted. This property enables synthetically useful yields to be achieved for the monocyclopropanation of polyalkene substrates, including terpene derivatives and conjugated 1,3-dienes. Mechanistic studies implicate a carbenoid species containing both Co and Zn as the catalytically relevant methylene transfer agent.
一种[PDI]CoBr配合物（PDI = 吡啶二亚胺）使用CHBr与Zn组合催化席曼-史密斯型还原环丙烷化反应。与其非催化变体相比，钴催化的环丙烷化能够根据烯烃的取代模式区分具有相似电子性质的烯烃：单取代>1,1-二取代>(E)-1,2-二取代>(Z)-1,2-二取代>三取代。这种性质使得对于包括萜烯衍生物和共轭1,3-二烯在内的聚烯烃底物的单环丙烷化能够获得合成上有用的产率。机理研究表明，一种同时含有Co和Zn的类卡宾物种是催化相关的亚甲基转移剂。
