Thiocarboxylic acids are rare in nature, however the biosynthetic components for producing them appear widespread in bacteria.
[6] 2,6-Pyridinedicarbothioic acid is synthesized by treating the diacid dichloride with a solution of H2S in pyridine: This reaction produces the orange pyridinium salt of pyridinium-2,6-dicarbothioate.
The halide is displaced to give a thioester intermediate, which is then hydrolyzed: Thiocarboxylic acids react with various nitrogen functional groups, such as organic azide, nitro, and isocyanate compounds, to give amides under mild conditions.
[10][11] This method avoids needing the amine to initiate an amide-forming acyl substitution but does requires synthesis and handling of the unstable thiocarboxylic acid.
Halogens or their equivalents (e.g. sulfuryl chloride) oxidize thiocarboxylic acids to acylsulfenyl halides.