Reactions of 4-Silatriafulvene with Carbon-Electrophiles

摘要

Among various triafulvene analogs having potential aromaticity, 4-silatriafulvene is unique with an exo Si=C double bond that is intrinsically polarized as Si~+-C~- in contrast to a typical 4-heterosubstituted triafulvene such as cyclopropenone. The polarity of the Si=C double bond is expected to be reduced by the contribution of a zwitterion aromatic resonance structure. We have recently demonstrated unusual reactivity of silatriafulvene derivatives generated as an isolable compound as well as a reactive intermediate. 1,2-Di-t-butyl-4,4-bis(t-butyl-dimethylsilyl)-4-silatriafulvene 1 reacts with methanol immediately at rt to give 2 in 73% yield (Scheme 1). The regioselectivity of this reaction is quite unusual but in accord with the inversed polarity of the Si=C bond of 1b. The result prompted us to study reactivity of 1 with various carbon electrophiles: enones, unsaturated lactones, and acetylenes.