The development of a general catalytic method for the direct and stereoselective construction of cyclopropanes bearing highly congested vicinal all-carbon quaternary stereocenters remains a formidable challenge in chemical synthesis. Here, we report an intramolecular radical cyclopropanation of unactivated alkenes with simple α-methylene group of aldehydes as C1 source via a Cu(I)/secondary amine cooperative catalyst, which enables the single-step construction of bicyclo[3.1.0]hexane skeletons with excellent efficiency, broad substrate scope covering various terminal, internal alkenes as well as diverse (hetero)aromatic, alkenyl, alkyl-substituted geminal alkenes. Moreover, this reaction has been successfully realized to an asymmetric transformation, providing an attractive approach for the construction of enantioenriched bicyclo[3.1.0]hexanes bearing two crucial vicinal all-carbon quaternary stereocenters with good to excellent enantioselectivity. The utility of this method is illustrated by facile transformations of the products into various useful chiral synthetic intermediates. Preliminary mechanistic studies support a stepwise radical process for this formal [2 + 1] cycloaddition.

中文翻译：

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醛的自由基不对称分子内α-环丙烷向含有邻位全碳四元立体中心的双环[3.1.0]己烷的转化。

对于具有高度拥挤的邻近全碳四元立体中心的环丙烷的直接和立体选择结构的通用催化方法的发展，仍然是化学合成中的巨大挑战。在这里，我们报告通过Cu（I）/仲胺协同催化剂，用简单的醛类的简单α-亚甲基作为C1源的未活化烯烃进行分子内自由基环丙烷化，从而实现双环[3.1.0]己烷骨架的单步构建以优异的效率，广泛的底物范围涵盖了各种末端，内部烯烃以及各种（杂）芳烃基，烯基，烷基取代的双链烯烃。而且，该反应已经成功地实现了不对称转化，为构建对映体富集的双环[3.1]提供了诱人的方法。0]己烷带有两个关键的邻位全碳四元立体中心，对映选择性很好。该方法的实用性通过将产物容易地转化成各种有用的手性合成中间体来说明。初步的力学研究支持这种正式的[2 +1]环加成反应的逐步激进过程。