Herz reaction

What is Herz reaction?

The Herz reaction is a chemical reaction discovered by Herz in 1914, which involves the reaction of primary aromatic amines, their salts, or N-acetyl derivatives with sulfur monochloride S2Cl2 to form 1,3,2-benzothiazathiolium chlorides, known as the Herz compounds.

Herz reaction - general reaction scheme
Herz reaction

Herz reaction is typically conducted in the presence of an inert solvent and is always accompanied by chlorination on the aromatic nucleus, primarily at the para-position of the amino group. The Herz compounds are difficult to purify and are typically converted into other derivatives, such as 1,2,3-benzodithiazole 2-oxide, o-amino thiophenol, substituted benzothiozoles, or o-aminophenylthioglycolic acid derivatives, which are used as intermediates to produce thioindigo dyestuffs in the industry.