Chiral Guanidine/Copper Catalyzed Asymmetric Azide-Alkyne Cycloaddition/[2+2] Cascade Reaction
Songsong Guo1, Pei Dong1, Yushuang Chen1
1Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, 610064, China.
Abstract:
We report the development of a chiral guanidine-based copper(I) catalyst for the asymmetric azide-alkyne cycloaddition/[2+2] cascade reaction. Optically active spiroazetidinimine oxindoles were constructed by trapping the ketenimine species under mild reaction conditions. High level of enantioinduction and excellent isolated yields were achieved in the three-component reaction of various isatin-derived ketimines, sulfonyl azides, and terminal alkynes. Control experiments and X-ray crystallography were used to probe into the interaction of chiral guanidinium salt with copper salt.
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