Introduction
<P>Thionyl chloride exhibits several features which have made it particularly attractive
as a reagent in organic synthesis. It is often applied as a powerful chlorinating
reagent, and reacts as such with carbonyl compounds, aromatic sulfochlorides, and
aliphatic alcohols; the formed intermediates can be further transformed to other useful
compounds.
[
1]
It can also be used as an HCl precursor and reacts in electrophilic additions or
substitutions with compounds containing C-C multiple bonds. Thionyl chloride also
reacts with amines or imines to form sulfinyl chlorides and it reacts with active
methyl or active methylene compounds to form sulfenyl chlorides through Pummerer-type
rearrangement.
[
2]
In addition, it can also be used as a chlorinating reagent through its oxidation and
partial dehydrogenation of organic compounds to give sulfuryl chloride. In some reactions
it serves as condensing reagent to form heterocyclic compounds, or it can be used
as catalyst.</P><P>In industrial production, thionyl chloride is used for the synthesis
of carboxylic acid chlorides. These products are frequently used as intermediates
for the production of pharmaceutical active ingredients, crop protection reagents,
and dyestuffs.</P><P>Compared with other chlorinating reagents, thionyl chloride
has many advantages: The end product is easy to isolate, it is comparatively easy
to handle, and the yields are generally high. It is miscible with nearly all organic
solvents and is itself a good solvent for most organic compounds.</P>
