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]

Applications[]

Benzothiadiazoles[]

The Herz salts hydrolyze to give aminothiophenols, which are suitable for diazotization, giving Benzothiadiazoles.^[2]

Benzothiazoles[]

The sodium thiolate 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.

Dyes[]

Aniline 5 is converted to compound 6, in three steps;

1. conversion to an ortho- 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, (, 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 isatin results in the thio-Indigo dye 9.

References[]