β-Trichlorosilylstyrene oligomers

Abstract

Under cationic conditions using triflic acid as the initiator, it is possible to oligomerize Ptrichlorosilylstyrene 2 to low molecular weight oligomers 14 with a maximum degree of polymerization of about 9. Termination of the process was shown to occur by an intramolecular FriedelLCrafts reaction, leading to highly functionalized, indane-terminated oligomers 9, 12, etc. At lower temperatures, the reaction is diastereoselective. The oligomerization process was shown to require electron-withdrawing groups on silicon; the replacement of C1 spectator ligands with alkoxy or alkyl groups led to protiodesilylation. The mechanism for formation of the indane-terminated oligomers is discussed.Key words: cationic polymerization, P-silylstyrene, stereoselective oligomerization, indene termination.RCsumC : Sous des conditions cationiques utilisant de l'acide triflique comme initiateur, il est possible de provoquer une oligomCrisation du P-trichlorosilylstyrkne, 2, en oligomkres 14 de bas poids molCculaire et comportant un degrC maximal de polymCrisation d'environ 9. On a montrC que le processus de terminaison se produit par une rCaction de FriedelLCrafts intramolCculaire conduisant B des oligomkres 9,12, etc. se terminant par des indanes hautement fonctionnalisCs. A des tempkratures plus basses, la rCaction est diastCrCosClective. On a montrC que le processus dLoligomCrisation nCcessite la presence de groupes Clectroattracteurs sur le silicium; le remplacement des coordinateurs C1 agissant comme spectateurs par des groupes alkoxyles ou alkyles conduit t i une protiodCsilylation. On discute du mecanisme de formation des oligomkres se terminant par un indane.Mots clks : polymCrisation cationique, P-silylstyrkne, oligomCrisation stCrCosClective, terminaison par un indkne.[Traduit par le rCdaction]

Friedel−Crafts Alkylation of Polychlorobenzenes with (1,2-Dichloroethyl)trichlorosilane

“…During the dimerization studies of β-(trichlorosilyl)styrene in the presence of triflic acid, two isomeric products, 1,2- cis -2,3- trans -2-trichlorosilyl-1-((trichlorosilyl)methyl)-3-phenylindane and 4 , were obtained at room temperature. However, the kinetically favored 1,2-cis-2,3-trans isomer was the major product compared to the thermodynamically favorable 1,2-trans-2,3-trans isomer 4 at low reaction temperatures …”