Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, USA.
J Am Chem Soc. 2010 Apr 14;132(14):5027-9. doi: 10.1021/ja100185p.
The first organocatalytic enantioselective radical polycyclization has been accomplished using singly occupied molecular orbital (SOMO) catalysis. The presented strategy relies on a selective single-electron oxidation of chiral enamines formed by condensation of polyenals with an imidazolidinone catalyst employing a suitable copper(II) oxidant. The reaction proceeds under mildly acidic conditions at room temperature and shows compatibility with an array of electron-poor as well as electron-rich functional groups. Upon termination by radical arylation followed by subsequent oxidation and rearomatization, a range of polycyclic aldehydes were accessed (12 examples, 54-77% yield, 85-93% ee). The enantioselective formation of up to six new carbocycles in a single catalyst-controlled cascade is described. Evidence for a radical-based cascade mechanism is indicated by a series of experimental results.
首次利用单占分子轨道（SOMO）催化实现了首例有机催化对映选择性自由基多环化反应。该策略依赖于缩合多烯醛与咪唑烷酮催化剂形成的手性烯胺的选择性单电子氧化，使用合适的铜（II）氧化剂。反应在温和的酸性条件下在室温下进行，并与一系列缺电子和富电子官能团兼容。通过自由基芳基化反应终止，然后进行后续的氧化和再芳构化，可获得一系列多环醛（12 个实例，产率为 54-77%，对映选择性为 85-93%）。描述了在单个催化剂控制的级联中对映选择性形成多达六个新的碳环。一系列实验结果表明存在基于自由基的级联机制的证据。
