LE PROBLEME DE LA CONJUGAISON A TRAVERS UN ATOME DE SILICIUM ?-LIE DANS LES SYSTEMES SILA-2 BUTADIENIQUES

Article abstract of DOI:10.1016/S0040-4020(01)92358-0

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.