Herz reaction


The Herz reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline-derivative to a so-called Herz salt with disulfur dichloride, followed by hydrolysis of this Herz salt to the corresponding sodium thiolate :

Applications

Benzothiazoles

The sodium thiolate 3 can be converted to an intermediate zinc mercaptide with zinc sulfate, followed by reaction of the mercaptide with for instance benzoyl chloride, forming a 1,3-benzothiazole 4.

Dyes

Aniline 5 is converted to compound 6, in three steps;
  1. conversion to an ortho-aminothiol through the Herz-reaction, followed by
  2. conversion to an ortho-aminoarylthioglycolacid and
  3. conversion of the aromatic amine function to a nitrile via the Sandmeyer reaction.
  4. In a last step the nitrile is hydrolysed resulting in 6. This compound is converted to 7 via a ring-closing reaction and decarboxylation.
The compound, is an important intermediate in the organic synthesis of some dyes. Condensation with acenaphthoquinone gives 8, a dye of the so-called Ciba-Scarlet type, while condensation of 7 with isatin results in the thio-Indigo dye 9.