Alcohols are highly reactive. This can be a problem if we want to react on some other part of the molecule. How can we guarantee that a reaction won’t take place at the alcohol?
For example, the following substitution reaction has a major problem as drawn. Can you spot the issue?
Protecting groups are reversible reactions that temporarily block groups from reacting, so that we can transform other parts of the molecule.
One way to protect alcohol is to form a reversible adduct with isobutylene via acid-catalyzed alkoxylation, yielding a temporary tert-butyl ether, which is completely unreactive.
Another group used to protect alcohols are silyl chlorides, namely TBDMS.
Concept: Mechanism of Silyl Ether Protecting Groups.8m
Example: Predict the product of the following reaction.4m