Herz reaction

The Herz-reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline-derivative (1) to a so-called Herz-salt (2) with disulfur dichloride, followed by hydrolysis of this Herz-salt (2) to the corresponding sodium thiolate (3) ^[1]:

Additional recommended knowledge

Essential Laboratory Skills Guide

Recognize and detect the effects of electrostatic charges on your balance

What is the Correct Way to Check Repeatability in Balances?

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 in three steps to compound 6, in three steps;

1. conversion to an ortho-aminothiol through the Herz-reaction (aniline 5 and disulfur dichloride), 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, (thioindoxyl, 7) 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 isatine results in the thio-Indigo dye 9.

References

1. ^ W. Warburton Chem. Rev. 57 (1957) p1011.