Electrophilic Substitution of Anionic Aluminabenzene via Sequential Reactions with Electrophile and Base

The reaction of an isolable anionic aluminabenzene with
electrophiles,
such as MeOTf and Me3SiOTf, was investigated. The nucleophilic
attack on the pentadienyl moiety of the aluminabenzene ring proceeded
at the 4-position to form the aluminacyclohexadiene bearing a Me or
Me3Si group. Treatment of the resulting methyl- or silyl-substituted
aluminacyclohexadiene with the bulky base MesLi gave the rearomatized
anionic aluminabenzene bearing a Me or Me3Si group. Thus,
this sequential reaction would be considered as an electrophilic substitution
of aluminabenzene. The substituent effect of Me and Me3Si groups on the aluminabenzene ring was also estimated on the basis
of experimental and theoretical studies.