Asymmetric Construction of Cyclobutanes via Direct Vinylogous Michael Addition/Cyclization of β,γ-Unsaturated Amides
Yuzhen Chen, Yichen Wang, Shuzhong Wang, Yanyan Ma, Deng‐Gao Zhao, Ruoting Zhan, Huicai Huang
Abstract
The construction of cyclobutanes has attracted much attention because of its unique four-membered ring skeleton. Herein, we report the highly enantioselective direct vinylogous Michael reaction of 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 (up to 99% ee). Importantly, the large-scale reaction experiment confirmed the reliability of the vinylogous reaction. Furthermore, the synthetic utility of the vinylogous adducts and cyclobutane derivatives has been realized.
Topics & Concepts
CyclobutanesCyclobutaneChemistryAdductEnantioselective synthesisRing (chemistry)CatalysisMichael reactionStereochemistryOrganic chemistryAsymmetric Synthesis and CatalysisAsymmetric Hydrogenation and CatalysisSynthetic Organic Chemistry Methods