Faculté des sciences

Tandem Nucleophilic Addition/Diels-Alder Reaction of N-Butadienyl N,O-Ketene Silyl Acetals with C60: Stereoselective Formation of Bicyclic Octahydroquinolino-1,2,3,4-Tetrahydrobuckminsterfullerenes and Combined NMR Spectroscopic and Computational Evaluation of the Functionalization Reactions

Rubin, Yves ; Ganapathi, Padma S. ; Franz, Andreas ; An, Yi-Zhong ; Qian, Wenyuan ; Neier, Reinhard

In: Chemistry - A European Journal, 1999, vol. 5, no. 11, p. 3162-3184

Abstract: We have studied the reactivity of the N,0-ketene N-l,3-butadienyl-N-alkyl-0-silyl acetals 1a-e with C60 proceeding through a tandem process to give the adducts 2a-e. The addition order of these tandem reactions has been evaluated. The initial nucleophilic Michael-like addition of the electron-rich N,O-ketene acetal moiety... Plus

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    Summary
    Abstract: We have studied the reactivity of the N,0-ketene N-l,3-butadienyl-N-alkyl-0-silyl acetals 1a-e with C60 proceeding through a tandem process to give the adducts 2a-e. The addition order of these tandem reactions has been evaluated. The initial nucleophilic Michael-like addition of the electron-rich N,O-ketene acetal moiety proceeds unusually fast at 25°C, followed by an intramolecularly accelerated Diels-Alder step that is highly diastereoselective. The structures of compounds 2a-e were determined from the 1H and 13C NMR shifts and from H - H coupling patterns, while their stereochemistry was deduced from 2D T-ROESY NMR experiments. The proposed mechanism for the nucleophilic addition involves single electron transfer followed by radical anion - radical cation recombination. Computational investigations of the reaction pathways, transition states, and conformational energies have been carried out to corroborate the experimental data.