National Engineering Research Center of Chiral Drugs, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
J Org Chem. 2021 Jan 15;86(2):1779-1788. doi: 10.1021/acs.joc.0c02621. Epub 2020 Dec 30.
An efficient decarboxylative [3 + 2] annulation reaction of ethynylethylene carbonates and azlactones has been developed with a copper salt as catalyst. This practical methodology gives access to a diverse library of γ-butyrolactones bearing α,β-two vicinal quaternary carbon centers in good to high yields with good levels of diastereoselectivities (up to 98% yield, >95:5 dr). Preliminary trials on enantioselective variant with a chiral PyBox ligand provided chiral products in up to 71% ee. This synthetic method features mild reaction conditions, broad functional group tolerance, large-scale synthesis, and versatile products transformation. A plausible catalytic cycle for the protocol is proposed based on previous related studies and our experimental observations.
一种高效的脱羧[3+2]环加成反应，由炔基乙烯碳酸酯和氮杂环丙烷酮引发，以铜盐作为催化剂。该实用方法为含有α,β-两个相邻季碳中心的γ-丁内酯提供了一个多样化的库，产率良好至高产（高达 98%的产率，>95:5 dr）。用手性 PyBox 配体进行对映选择性变体的初步试验，可得到高达 71%ee 的手性产物。该合成方法具有反应条件温和、官能团容忍度广、大规模合成和多功能产物转化的特点。根据先前的相关研究和我们的实验观察，提出了该反应的一个可能的催化循环。
