Friedel-Crafts alkylation of polychlorobenzenes with (1,2-dichloroethyl)trichlorosilane

Abstract

(1,2-Dichloroethyl)trichlorosilane (2) reacted with a 6-fold excess of mono-, di-, and trichlorobenzenes at 120 degreesC in the presence of aluminum chloride to give regiospecific (2,2-diarylethyl)trichlorosilanes via a carbocation rearrangement. The yields were 61-69%, and regioisomers of (1,2-diarylethyl)silanes were not obtained. Alkylation of 1,2,3,4-tetrachlorobenzene with 2 did not give [2,2-bis(tetrachlorophenyl)ethyl]trichlorosilane or 9,10-bis-(silyl)methyl-9,10-dihydroanthracenes but gave cyclic silyl-substituted indanes in 84% yield via the acid-catalyzed dimerization of beta-(trichlorosilyl)styrene formed by the first alkylation, followed by dehydrochlorination. The structure of 1,2-trans-2,3-trans-4,5,6,7-tetrachloro-1-(2,3,4,5-tetrachlorophenyl)-2-(trichlorosilyl)-3-((trichlorosilyl)methyl)indane has been determined by X-ray crystallography. The desilylated product, 1,3-cis-4,5,6,7-tetrachloro-1-(2,3,4,5tetrachlorophenyl)-3-((trichlorosilyl)methyl)indane, was reduced by LiAlH4, and its structure was also determined..