Friedel-Crafts polyalkylation of alkylbenzenes with dichloromethylvinylsilane

Abstract

The Friedel-Crafts alkylation of alkylbenzenes such as toluene, ethylbenzene, n-propylbenzene, 12-butylbenzene, o-, m-, p-xylene, and mesitylene with dichloromethylvinylsilane in the presence of aluminum chloride catalyst has been studied under mild conditions. Alkylation with dichloromethylvinylsilane at room temperature gave peralkylated products in yields ranging from 25 to 63%, depending upon the number of substituents on the benzene ring. Less alkylated compounds were also obtained as minor products along with alkyl-reoriented products or transalkylated products. The alkylations of substituted benzenes such as chlorobenzene and anisole did not give the peralkylated products under the same conditions. The molecular structure of tris(dichloromethylsilylethyl)mesitylene has been determined by X-ray diffraction studies. The two chlorosilyl group containing substituents are arranged above the benzene plane and the other one below. Peralkylated compounds were methylated or reduced to the corresponding derivatives by reacting with methyl Grignard reagent and LiAlH4. (C) 1997 Elsevier Science S.A.