Retro-Bingel reaction in the electrochemical reduction of bis(dialkoxyphosphoryl)methanofullerenes |
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Authors: | Yanilkin V V Nastapova N V Gubskaya V P Morozov V I Berezhnaya L Sh Nuretdinov I A |
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Institution: | (1) Kazan Scientific Center of the Russian Academy of Sciences, A. E. Arbuzov Institute of Organic and Physical Chemistry, 8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation |
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Abstract: | Four steps of reduction were detected for bis(diethoxyphosphoryl)- and bis(diisopropoxyphosphoryl)methano60]fullerenes (1, 2) and bis(diethoxyphosphoryl)methano70]fullerene (3) by cyclic voltammetry in the o-dichlorobenzene—DMF (3 : 1, v/v)/Bu4NBF4 (0.1 mol L–1) system on a glass-carbon electrode. At the first step the reversible transfer of one electron affords stable radical anions 1 and 2 (g = 1.9999, H = 1.9 G). When two electrons per molecule are transferred, the methano fragment is rapidly eliminated (retro-Bingel reaction). This process involves the step-by-step cleavage of two C—C bonds of exo-carbon with the fullerene shell in combination with the stepwise transfer of other two electrons and a proton to form finally the carbanion of the methano fragment and fullerene dianion. For all studied compounds, the elimination rate is much higher than that for bis(alkoxycarbonyl)- and dialkoxyphosphoryl(alkoxycarbonyl)methano60]fullerenes, which makes it possible to propose bisphosphorylmethane groups as protective in synthesis of new fullerene derivatives. |
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Keywords: | bisphosphorylmethanofullerenes electrochemical reduction Bingel reaction retro-Bingel reaction radical anion dianion elimination of methano fragment ESR |
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