10.3.2 Application as Protecting Groups for Alcohols

Silicon based protecting groups are the versatile for alcohols. They can be easily introduced and removed in high yield without affecting the rest of the molecule in a wide range of conditions. The rate of the introduction as well as the removel depends on the steric nature of the alcohols as well as the silyl group (Scheme 4).

Scheme 4

Some the commonly used protecting for alcohols follows:

10.3.3 Application as Protecting Groups for Alkynes

The silyl group can be used to protect the terminus of the alkyne during the reaction and can also be easily removed with fluoride or sodium hydroxide (Scheme 5).

Scheme 5

10.3.3 Directive Influence of SiR₃ in Electrophilic Reactions

10.3.3.1 Alkynylsilanes

Similar to alkynes, silylated alkynes are too nucleophilic towards electrophiles. However, the presence of silicon has a dramatic effect on the regioselectivity of the reaction: the attack occurs only at the atom directly bonded to silicon (Scheme 6). This is due to the stabilization of the intermediate vacant p orbital by the filled C-Si sigma orbital.

Scheme 6