State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China.
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300071, China.
Chem Asian J. 2018 Sep 17;13(18):2606-2610. doi: 10.1002/asia.201800934. Epub 2018 Aug 3.
The transition-metal-catalyzed formal C-C bond insertion reaction of diazo compounds with monocarbonyl compounds is well established, but the related reaction of 1,3-diketones instead gives C-H bond insertion products. Herein, we report a protocol for a gold-catalyzed formal C-C bond insertion reaction of 2-aryl-2-diazoesters with 1,3-diketones, which provides efficient access to polycarbonyl compounds with an all-carbon quaternary center. The aryl ester moiety plays a crucial role in the unusual chemoselectivity, and the addition of a Brønsted acid to the reaction mixture improves the yield of the C-C bond insertion product. A reaction mechanism involving cyclopropanation of a gold carbenoid with an enolate and ring-opening of the resulting donor-acceptor-type cyclopropane intermediate is proposed. This mechanism differs from that of the traditional Lewis-acid-catalyzed C-C bond insertion reaction of diazo compounds with monocarbonyl compounds, which involves a rearrangement of a zwitterion intermediate as a key step.
过渡金属催化的重氮化合物与单羰基化合物的形式 C-C 键插入反应已经得到很好的证实，但相关的 1,3-二酮的反应则得到 C-H 键插入产物。在此，我们报告了一个金催化的 2-芳基-2-重氮酯与 1,3-二酮的形式 C-C 键插入反应的方案，该方案为具有全碳季碳中心的多羰基化合物提供了有效的途径。芳基酯部分在不寻常的化学选择性中起着关键作用，并且向反应混合物中添加布朗斯台德酸可以提高 C-C 键插入产物的收率。提出了一种涉及金卡宾与烯醇化物的环丙烷化和所得给体-接受型环丙烷中间体的开环的反应机理。该机理与传统的路易斯酸催化的重氮化合物与单羰基化合物的 C-C 键插入反应的机理不同，后者涉及作为关键步骤的两性离子中间体的重排。
