The stabilization of the cation weakens the C-Si bond by the delocalization of the electron density. The attack of a nucleophile on silicon readily removes it from the organic fragment and the net result is the electrophilic substitution in that the silicon is replaced by the electrophile (Scheme 7).

Scheme 7

10.3.3.2 Vinyl Silanes

The controlled reduction of alkynyl silanes can produce vinayl silanes. The stereochemistry depends on the methods used. Lindlar hydrogenation takes place via cis fashion, while red Al reduction of propargylic alcohol gives E -isomer (Scheme 8).

Scheme 8

Alternatively, hydrosilylation of simple alkyne can give E-vinyl silane that could be irradiated to afford Z-isomer (Scheme 9).

Scheme 9