Asymmetric Construction of Cyclobutanes via Direct Vinylogous Michael Addition/Cyclization of β,γ-Unsaturated Amides

• DOI: 10.1021/acs.orglett.0c02488
• Publication Date: 2020-09-09T18:20:07Z
• Authors: Yuzhen Chen; Yichen Wang; Shuzhong Wang; Yan-Yan Ma; Deng-Gao Zhao; Ruoting Zhan; Huicai Huang
• Keywords: Cyclobutanes; Michael reaction

The construction of cyclobutanes has attracted much attention because its unique four-membered ring skeleton. Herein, we report the highly enantioselective direct vinylogous Michael reaction β,γ-unsaturated pyrazole amides and nitroolefin using a squaramide catalyst. Cyclobutane derivatives were obtained by subsequent cyclization in good yields (up to 85%) with excellent enantioselectivities 99% ee). Importantly, large-scale experiment confirmed reliability reaction. Furthermore, synthetic utility adducts cyclobutane been realized.