Huang Xiaoqiang, Lin Jiahui, Shen Tianqi, Harms Klaus, Marchini Marianna, Ceroni Paola, Meggers Eric
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany.
Department of Chemistry "Giacomo Ciamician", University of Bologna, 40126, Bologna, Italy.
Angew Chem Int Ed Engl. 2018 May 4;57(19):5454-5458. doi: 10.1002/anie.201802316. Epub 2018 Apr 10.
The herein reported visible-light-activated catalytic asymmetric [3+2] photocycloadditions between cyclopropanes and alkenes or alkynes provide access to chiral cyclopentanes and cyclopentenes, respectively, in 63-99 % yields and with excellent enantioselectivities of up to >99 % ee. The reactions are catalyzed by a single bis-cyclometalated chiral-at-metal rhodium complex (2-8 mol %) which after coordination to the cyclopropane generates the visible-light-absorbing complex, lowers the reduction potential of the cyclopropane, and provides the asymmetric induction and overall stereocontrol. Enabled by a mild single-electron-transfer reduction of directly photoexcited catalyst/substrate complexes, the presented transformations expand the scope of catalytic asymmetric photocycloadditions to simple mono-acceptor-substituted cyclopropanes affording previously inaccessible chiral cyclopentane and cyclopentene derivatives.
本文报道的环丙烷与烯烃或炔烃之间的可见光活化催化不对称[3+2]光环加成反应，分别以63-99%的产率和高达>99% ee的优异对映选择性，提供了获得手性环戊烷和环戊烯的方法。反应由单一的双环金属化金属手性铑配合物（2-8 mol%）催化，该配合物与环丙烷配位后生成吸光配合物，降低环丙烷的还原电位，并提供不对称诱导和整体立体控制。通过直接光激发的催化剂/底物配合物的温和单电子转移还原实现，所展示的转化将催化不对称光环加成反应的范围扩展到简单的单受体取代环丙烷，得到以前难以获得的手性环戊烷和环戊烯衍生物。
