We developed a new reactive iron (III) initiator for radical cation [4+2] cycloaddition. In the presence of 10 mol% of FeCl₃ and 30 mol% of AgSbF_6, [4+2] cycloaddition of non-conjugated tetrasubstituted alkenes with 2,3-dimethyl-1,3-butadiene provided the cycloadduct in up to 99% yield. In addition, a kinetic study suggested that ring closure is the rate-determining step, which could be accelerated by intramolecular single electron transfer.

中文翻译：

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FeCl3/AgSbF6 共引发剂对非共轭四取代烯烃的自由基阳离子 [4+2] 环加成反应

我们开发了一种用于自由基阳离子 [4+2] 环加成的新型活性铁 (III) 引发剂。在 10 mol% FeCl ₃和 30 mol% AgSbF _{6 存在下，}非共轭四取代烯烃与 2,3-二甲基-1,3-丁二烯的 [4+2] 环加成提供高达 99% 的环加合物屈服。此外，动力学研究表明闭环是决定速率的步骤，可以通过分子内单电子转移加速。