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.

中文翻译：

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B(C6F5)3-催化 3-烯基-羟吲哚与重氮甲烷的环丙烷化反应

Spirocyclopropane-oxindoles 是生物活性化合物中的关键基序，是多功能的合成中间体。在此，我们报告了3-烯基羟吲哚与重氮甲烷的无金属 B(C ₆ F ₅ ) _{3催化环丙烷化反应。}这提供了螺环丙烷-羟吲哚衍生物的 25 种变体。这些螺环丙烷-羟吲哚产物在温和的反应条件下以良好至优异的产率（高达 99%）和高非对映选择性（高达 20:1 dr）获得，并且可以在克规模上进行。