Herz reaction

The Herz reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline to the benzodithiazolium salt by its reaction with disulfur dichloride.

Hydrolysis of this Herz salt give the corresponding sodium thiolate, which can be further converted to the 2-aminothiophenol.

[1] The 2-aminothiophenols are suitable for diazotization, giving benzothiadiazoles.

Aniline 5 is converted to compound 6, in three steps; 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 isatin results in the thio-Indigo dye 9.