Introduction
<P>Although NaHSO
4 has been known for a long time, only in recent years it emerged as an efficient catalyst
in organic chemistry. The new interest in this salt is due to environmental and
economical considerations that prompt urgent need to redesign important chemical processes
using suitable catalysts. NaHSO
4 can be used alone or supported on alumina
[
1]
or silica gel, in solvent or under solvent-free conditions. The most often used form
of it is the silica gel supported form. This catalyst promotes various transformations
like selective and regioselective protection and deprotection,
[
2-9]
nitration,
[
10]
nitrosation,
[
11]
oxidation,
[
12]
Beckman rearrangement,
[
1]
synthesis of halide derivatives,
[
13]
[
14]
coupling of indoles,
[
15]
and synthesis of quinazolinones.
16
</P><P>The advantages of using NaHSO
4 include operational simplicity, selectivity, and availability, and it is inexpensive
and ecologically friendly.
</P>
