When discussing the Gattermann–Koch reaction on phenol substrates, it has been said that O-acylation is a problematic competing reaction as
in a phenol, there's high electron density on the O atom [...]
However, there are also numerous other reactions where phenol reacts with electrophiles on the benzene ring. Some examples are:
- the Houben–Hoesch synthesis (a kind of FC acylation);
- the Riemer–Tiemann reaction;
- the reaction of phenol with nitrous acid to form 4-nitrosophenol;
- the Kolbe–Schmitt reaction; and
- the Vilsmeier reaction, amongst others.
Why is the Gatterman–Koch reaction an exception?
