SYNTHESIS OF FUNCTIONALIZED FULLERENES BY PHOTOADDITION OF N-alpha-TRIMETHYLSILYL-N-CARBOXYMETHYL-N-BENZYLAMINES TO C-60

摘要

Photoaddition reactions of fullerene C-60 with N-alpha-trimethylsilyl-N-carboxymethyl-N-benzylamines, which contain various para-substituents, were explored in order to evaluate factors governing efficiencies of this potentially useful method for preparing functionalized fullerene derivatives. Observations made in this study show that two reaction pathways are followed in these photoreactions. The first involves initial formation of alpha-trimethylsilyl-aminium radicals and the C-60 anion radical by SET from the amines to the triplet excited state of C-60. This step is followed by desilylation to produce alpha-amino radicals. Coupling of these radicals with the anion radical of C-60 followed by protonation or with the hydrofullerene radical generated by protonation of the anion radical of C-60 then produces aminomethyl-1,2-dihydrofullerenes. When limited amounts of (3)o(2) are present in the reaction medium, fulleropyrrolidines are generated in low yields by a competitive pathway involving formation of singlet oxygen, which undergoes sequential H-atom abstractions from the N-alpha-trimethylsilyl-N-carboxymethyl-N-benzylamines to produce azomethine ylide intermediates. Dipolar cyloaddition of the ylides to C-60 then produces fulleropyrrolidines. Photoreactions of the C-60 and the amines in the presence of high (3)o(2) concentrations exclusively produce fulleropyrrolidine. In addition, the results show that photoreactions of non-silicon substituted, N-methyl-N-carboxymethyl-N-benzylamines with C-60 form fulleropyrrolidines independent of the concentration of O-3(2) present in the media.