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DOI: 10.1055/s-0034-1378594
SET Sets the Stage: Photochemical Synthesis of Aminomethylfullerenes
Method for the Synthesis of Amine-Functionalized Fullerenes Involving SET-Promoted Photoaddition Reactions of α-Silylamines.
J. Org. Chem. 2014;
79: 6946-6958
Publication History
Publication Date:
18 August 2014 (online)
Key words
fullerenes - single-electron transfer - silyl reagents - aminomethylation - radical reaction
Significance
Fullerene (C60) and its derivatives have found particular use as n-type semiconductors in field-effect transistors and photovoltaic devices. While most transformations of C60 are based on cycloaddition and nucleophilic addition, reactions initiated by photoexcitation are particularly attractive, because the high reduction potential of the triplet state of C60 enables rapid single-electron transfer (SET) with ground-state electron donors, including aliphatic amines. The authors find that photochemical reactions of C60 with trialkylsilylamines 1 are highly efficient and regioselective for 1,2-addition across the [6,6]-juncture.
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Comment
Photoreactions were performed with a mercury lamp (hν < 290 nm) for 4–60 minutes. The use of small amounts of ethanol as a co-solvent was found to be crucial for the formation of 2, as the alcohol promotes desilylation of the radical cation of 1. Because of the rapidity of the SET step, an electron-accepting phthalimide group is tolerated (2c). Interestingly, only monosubstituted products were observed. At longer reaction times, α-silyl amines containing electron-withdrawing groups (such as 1d) produced fulleropyrrolidine side products, which are believed to arise from singlet oxygen mediated formation of azomethine ylides that subsequently undergo cycloaddition with C60.
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