Alkyl cyclopropyl ketones are introduced as versatile substrates for catalytic formal [3 + 2] cycloadditions with alkenes and alkynes and previously unexplored enyne partners, efficiently delivering complex, sp³-rich products. The key to effectively engaging this relatively unreactive new substrate class is the use of SmI₂ as a catalyst in combination with substoichiometric amounts of Sm⁰; the latter likely acting to prevent catalyst deactivation by returning Sm^III to the catalytic cycle. In the absence of Sm⁰, background degradation of the SmI₂ catalyst can outrun product formation. For the most recalcitrant alkyl cyclopropyl ketones, catalysis is “switched-on” using these new robust conditions, and otherwise unattainable products are delivered. Combined experimental and computational studies have been used to identify and probe reactivity trends among alkyl cyclopropyl ketones, including more complex bicyclic alkyl cyclopropyl ketones, which react quickly with various partners to give complex products. In addition to establishing alkyl cyclopropyl ketones as a new substrate class in a burgeoning field of catalysis, our study provides vital mechanistic insight and robust, practical approaches for the nascent field of catalysis with SmI₂.

中文翻译：

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烷基环丙基酮在催化缩甲醛 [3 + 2] 环加成反应中的作用：SmI2 催化剂稳定化的作用

烷基环丙基酮作为多功能底物被引入，用于与烯烃和炔烃以及之前未开发的烯炔伙伴进行催化形式 [3 + 2] 环加成，有效地提供复杂的、富含 sp ³的产物。有效地参与这种相对不活泼的新底物类别的关键是使用SmI ₂作为催化剂并结合亚化学计量的Sm ⁰；后者可能通过将 Sm ^III返回到催化循环来防止催化剂失活。在不存在Sm ⁰的情况下，SmI ₂催化剂的背景降解可能会超过产物的形成。对于最顽固的烷基环丙基酮，使用这些新的稳健条件“启动”催化，并提供其他方式无法获得的产品。结合实验和计算研究已用于识别和探测烷基环丙基酮之间的反应性趋势，包括更复杂的双环烷基环丙基酮，其与各种伙伴快速反应，产生复杂的产物。除了将烷基环丙基酮确立为新兴催化领域的新底物类别之外，我们的研究还为 SmI ₂催化的新兴领域提供了重要的机理见解和稳健实用的方法。