Synthesis of organosilicon compounds. XI. On the reaction of p- and m-(trimethylsilyl)chlorobenzene with electrophilic reagents

Abstract

Reaction of p-(trimethylsilyl)- (IV) and m-(trimethylsilyl)chlorobenzene (V) with various electrophilic reagents was examined. Bromination, nitration with acetyl nitrate, and Friedel-Crafts acylation of IV respectively afforded p-bromo-chlorobenzene, p-chloro-nitrobenzene, and p-chloro-acylphenone. Nitration of V resulted in substitution of the chlorine in paraposition with a nitro group to produce 2-(trimethylsilyl)-4-chloro-nitrobenzene (VII), which was reduced to 2-(trimethylsilyl)-4-chloroaniline (VIII) and further decomposed by acid to p-chloroaniline. Bromination and Friedel-Crafts acylation of V do not result in substitution of the chlorine in para-position and desilylation occurs in meta-position to produce m-bromo-chlorobenzene and m-chloro-acylphenone. Such a reaction does not occur in other meta-substituted (trimethylsilyl)benzenes. It is assumed that such independence of the substituent position from the +M effect of the functional group and desilylation by electrophilic reagents occurring solely by the + I effect of the trimethylsilyl group would appear as the +M effect of the functional group becomes smaller.