FLPNO Nitroxide Radical Formation by a 1,1-Carboboration Route

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• 作者：René Liedtke ; Christina Eller ; Constantin G. Daniliuc ; Kamille Williams ; Timothy H. Warren ; Matthias Tesch ; Armido Studer ; Gerald Kehr ; Gerhard Erker
• 刊名：Organometallics
• 出版年：2016
• 出版时间：January 11, 2016
• 年：2016
• 卷：35
• 期：1
• 页码：55-61
• 全文大小：564K
• ISSN：1520-6041

文摘

The 1-trimethylsilylethynyl-2-diarylphosphanylethynylbenzene substrates 7a–7c, with the diarylphosphanyl groups = PPh₂, P(o-tolyl)₂, or P(mesityl)₂, were reacted with the strong boron Lewis acid B(C₆F₅)₃ at ambient conditions. The starting materials 7a and 7b, featuring rather small nucleophilic phosphanyl substituents, underwent selective 1,1-carboboration at the C≡C-PAr₂ moiety, forming rather unreactive unsaturated vicinal P/B Lewis pairs 8a and 8b that show a relatively strong internal P···B Lewis base/Lewis acid interaction. In contrast, the PMes₂ system 7c reacted with B(C₆F₅)₃ by a reaction sequence which was initiated by 1,1-carboboration and involved tandem C₆F₅ and mesityl group migration to yield the unsaturated annulated P/B Lewis pair 9, featuring an electron-withdrawing C₆F₅ group at phosphorus. Compound 9 underwent cooperative P/B addition to the nitrogen atom of nitric oxide to give the persistent FLPNO^? nitroxide radical 12. Radical 12 was characterized by electron spin resonance spectroscopy and by X-ray diffraction. It showed typical nitroxide radical reactions.