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Tandem Nucleophilic Addition/Diels-Alder Reaction of <i>N</i>-Butadienyl <i>N,O</i>-Ketene Silyl Acetals with C<sub>60</sub>: Stereoselective Formation of Bicyclic Octahydroquinolino-1,2,3,4-Tetrahydrobuckminsterfullerenes and Combined NMR Spectroscopic and Computational Evaluation of the Functionalization Reactions
Auteur(s)
Rubin, Yves
Ganapathi, Padma S.
Franz, Andreas
An, Yi-Zhong
Qian, Wenyuan
Date de parution
1999
In
Chemistry - A European Journal, Wiley, 1999/5/11/3162-3184
Résumé
Abstract: We have studied the reactivity of the <i>N,0</i>-ketene <i>N</i>-l,3-butadienyl-<i>N</i>-alkyl-<i>0</i>-silyl acetals <b>1a-e</b> with C<sub>60</sub> proceeding through a tandem process to give the adducts <b>2a-e</b>. The addition order of these tandem reactions has been evaluated. The initial nucleophilic Michael-like addition of the electron-rich <i>N,O</i>-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 <b>2a-e</b> were determined from the <sup>1</sup>H and <sup>13</sup>C 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.
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Type de publication
journal article
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