Avullala Thirupataiah, Nguyen Hiep H, Dakarapu Udaya Sree, Asgari Parham, Hua Yuanda, Jeon Junha
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States.
ACS Catal. 2022 Feb 4;12(3):1764-1774. doi: 10.1021/acscatal.1c04628. Epub 2022 Jan 18.
Redox-neutral carbon-carbon (C-C) bond activation and functionalization strategies of cyclopropanols that give metallo homoenolate have offered merits to construct a range of useful -functionalized ketones in an inverse-polarity fashion. Discovery and identification of oxidative C-C activation reactions of cyclopropanols that generate metallo enolate-homoenolate would provide an opportunity to afford ,-difunctionalized ketones. We report catalytic, net oxidative C-C activation, and silylation of cyclopropanols with traceless acetal directing groups under consecutive Ir and Rh catalysis in regio-, stereo-, and chemo-selective fashion. In detail, Ir-catalyzed hydrosilylation of cyclopropyl acetates provides the acetal directing group in quantitative yield. Rh-catalyzed proximal C-C silylation of the resulting cyclopropyl silyl acetal produces the metallo enolate-homoenolate equivalent, dioxasilepine, which uniquely holds an interconnected -silyl moiety and Z-vinyl acetal. Upon sequential treatment of a silaphile that removes the acetal directing group and electrophile, the seven-membered silicon-containing heterocycle, serving as the ketone ,-dianion equivalent, delivers ,-difunctionalized ketones. Scope of the hitherto unexplored reactivity of cyclopropanols toward net oxidative C-C silylation and the versatility of the resulting dioxasilepines were demonstrated. These include late-stage, net oxidative C-C silylation of biologically relevant molecules and facile production of a range of ,-difunctionalized ketones. Preliminary mechanistic studies suggest that the C-C activation harnessing the electron-rich Wilkinson-type catalyst is likely the turnover-determining step and a Rh- interaction is the key to the efficient metal insertion to the proximal C-C bond in cyclopropanols.
环丙醇的氧化还原中性碳-碳（C-C）键活化和官能团化策略可生成金属均烯醇盐，这为以反极性方式构建一系列有用的官能团化酮提供了优势。发现并鉴定能生成金属烯醇盐-均烯醇盐的环丙醇的氧化C-C活化反应，将为制备α,β-双官能团化酮提供机会。我们报道了在连续的铱（Ir）和铑（Rh）催化下，环丙醇与无痕缩醛导向基团进行催化、净氧化C-C活化和硅基化反应，该反应具有区域选择性、立体选择性和化学选择性。具体而言，铱催化的环丙基乙酸酯的硅氢化反应能定量产率地提供缩醛导向基团。铑催化所得环丙基硅基缩醛的近端C-C硅基化反应生成金属烯醇盐-均烯醇盐等价物二氧杂硅环庚烷，其独特地含有一个相互连接的硅基部分和Z-乙烯基缩醛。在依次用一个能除去缩醛导向基团的亲硅体和亲电试剂处理后，这个作为酮α,β-双阴离子等价物的七元含硅杂环可生成α,β-双官能团化酮。展示了环丙醇对净氧化C-C硅基化反应迄今未被探索的反应活性范围以及所得二氧杂硅环庚烷的多功能性。这些包括生物相关分子的后期净氧化C-C硅基化反应以及一系列α,β-双官能团化酮的简便制备。初步机理研究表明，利用富电子威尔金森型催化剂的C-C活化可能是周转决定步骤，而铑-相互作用是金属有效插入环丙醇近端C-C键的关键。
