Le probleme de la conjugaison a travers un atome de silicium π-lie dans les systemes sila-2 butadieniques |
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Authors: | G. Bertrand G. Manuel P. Mazerolles G. Trinquier |
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Affiliation: | Laboratoire des Organométalliques, Université Paul-Sabatier, 118 route de Narbonne, 31062 Toulouse Cédex, France;Laboratoire de Physique Quantique, Université Paul-Sabatier, 118 route de Narbonne, 31062 Toulouse Cédex, France |
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Abstract: | The chemical behaviour of sila-2 butadienes, formed as transient intermediates either by thermolysis or by photolysis of various 1-vinylsilacyclobutanes, was studied with respect to hydroxylated compounds of different pKa values Two mechanisms can explain the nature of the products obtained on the co-thermolysis of the cyclic compounds with phenol, one with 1-silacyclobut-1-ene intermediate and the other involving an allylic silicenium cation. In both hypothetical mechanisms, the 2-silabutadienes behave as a conjugated system since they lead either to (2+2) cycloaddition or to (1,2)- and (1,4)-electrophilic addition. This evidence for a conjugation phenomenon through a silicon atom is supported by the calculation of the delocalisation energies of butadiene and 2-silabutadiene. |
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