Brønsted Acid Catalyzed 1,2-Silyl Shift in Propargyl Silanes: Synthesis of Silyl Dienes and Silyl Indenes

A general method for generation of
allyl carbenium ions from propargyl
silanes via a 1,2-silyl shift by Brønsted acids is reported.
Two possible reaction pathways are described. Deprotonation results
in silyl dienes with yields from 52% to 92%. Intramolecular Friedel–Crafts
reactions of aryl-substituted systems give access to silyl indenes
with yields of 18–90% depending on the substitution pattern.
The obtained products have been shown to react as alkenyl silanes
in Hiyama coupling and electrophilic substitution and as dienes in
Diels–Alder cycloaddition.