Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy , Northwest A&F University , Yangling 712100 , China.
Department of Chemistry and Biochemistry , University of California , Santa Barbara , California 93106 , United States.
J Am Chem Soc. 2018 May 2;140(17):5860-5865. doi: 10.1021/jacs.8b01813. Epub 2018 Apr 17.
The [2+2] cycloaddition is a versatile strategy for the synthesis of strained cyclobutenes of high synthetic value. In this study, two efficient intermolecular [2+2] cycloadditions between two different types of chloroalkynes and unactivated alkene are realized with gold catalysis. Of significance is that the reaction works with challenging monosubstituted unactivated alkenes, which is unprecedented in gold catalysis and scarcely documented in other metal-catalyzed/promoted reactions; moreover, the reaction exhibits excellent regioselectivities, which are much better than those reported in literature. With 1,2-disubstituted unactivated alkenes, the reaction is largely stereospecific. The cyclobutene products can be prepared in nearly gram scale and readily undergo further reactions including various cross-coupling reactions using the C(sp)-Cl and/or C(sp)-SPh bond, which in turn substantially broaden the scope of accessible cyclobutenes and enhance the synthetic utility of this bimolecular reaction.
[2+2]环加成反应是一种合成高合成价值的应变环丁烯的通用策略。在这项研究中，通过金催化实现了两种不同类型的氯炔烃与非活化烯烃之间的两种有效的分子间[2+2]环加成反应。重要的是，反应适用于具有挑战性的单取代非活化烯烃，这在金催化中是前所未有的，在其他金属催化/促进的反应中也很少有文献报道；此外，反应表现出优异的区域选择性，优于文献中报道的选择性。对于 1,2-二取代的非活化烯烃，反应具有很大的立体特异性。环丁烯产物可以在近克级规模制备，并容易进行进一步的反应，包括使用 C(sp)-Cl 和/或 C(sp)-SPh 键的各种交叉偶联反应，这反过来又大大拓宽了可获得的环丁烯的范围，并增强了这种双分子反应的合成实用性。
