B(C6F5)3-catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes
Lei Xiao1, Lvnan Jin1, Yunbo Zhao1
1Institute of Drug Discovery Technology, Ningbo University, Zhejiang, China. guojing@nbu.edu.cn.
Abstract:
Spirocyclopropane-oxindoles are key motifs in biologically active compounds and are versatile synthetic intermediates. Herein, we report a metal-free, B(C6F5)3 catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes. This provides 25 variants of spirocyclopropane-oxindole derivatives. These spirocyclopropane-oxindole products were obtained in good to excellent yields (up to 99%) and high diastereoselectivities (up to 20 : 1 d.r.) under mild reaction conditions and could be performed on a gram scale.
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