9-Ethynylfluoroenyl Radicals: Regioselective Dimerization and Post Ring-Cyclization Reactions

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• 作者：Shuhai Qiu ; Youyu Zhang ; Xiaobo Huang ; Lipiao Bao ; Youhua Hong ; Zebing Zeng ; Jishan Wu
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：December 2, 2016
• 年：2016
• 卷：18
• 期：23
• 页码：6018-6021
• 全文大小：344K
• ISSN：1523-7052

文摘

9-Ethynylfluorenyl radical derivatives were readily prepared in situ and underwent simultaneous intermolecular coupling reactions. Interestingly, the dimerization process took place in either a head-to-tail or a head-to-head mode between the acetylenic or the allenic resonance forms dependent on the terminal substituents, which could be well explained by their different spin distribution and steric hindrance effects. The structures of the products were confirmed by X-ray crystallographic and other spectroscopic analyses. It was also found that the newly generated dipropinyl dimers underwent a rearrangement and ring-cyclization reaction at room temperature, eventually giving unique difluorenylidene cyclobutene derivatives.