2-Mercaptothiazoles, synthesis

In the first chapter, devoted to thiazole itself, specific emphasis has been given to the structure and mechanistic aspects of the reactivity of the molecule most of the theoretical methods and physical techniques available to date have been applied in the study of thiazole and its derivatives, and the results are discussed in detail The chapter devoted to methods of synthesis is especially detailed and traces the way for the preparation of any monocyclic thiazole derivative. Three chapters concern the non-tautomeric functional derivatives, and two are devoted to amino-, hydroxy- and mercaptothiazoles these chapters constitute the core of the book. All discussion of chemical properties is complemented by tables in which all the known derivatives are inventoried and characterized by their usual physical properties. This information should be of particular value to organic chemists in identifying natural or Synthetic thiazoles. Two brief chapters concern mesoionic thiazoles and selenazoles. Finally, an important chapter is devoted to cyanine dyes derived from thiazolium salts, completing some classical reviews on the subject and discussing recent developments in the studies of the reaction mechanisms involved in their synthesis. 

In 1892, Marchesini (94) described the synthesis of 4-phenyl-2-mercaptothiazole (62) by condensing bromoacetophenone with ammonium dithiocarbamate. 

The synthesis of sulfides (172) can be carried out by condensing 2-mercaptothiazoles and the required o-bromo compounds in basic solution at room temperature (488). 

Reactions of alkynyliodonium salts with multidentate nucleophiles can be employed for the synthesis of heterocyclic compounds. Recent examples include preparations of thiazoles, selenazoles, and 2-mercaptothiazoles by the treatment of alkynyliodonium mesylates or tosylates with thioamides, selenoamides, and ammonium dithiocarbamate (Scheme 62) [169-171]. A novel hetero-Claisen rearrangement of tricovalent iodine(III) intermediates was proposed to account for the 2,4-disubstitution pattern of the thiazoles [169]. 

Ammonium dithiocarbamate is useful in the synthesis of heterocyclic compounds, particularly mercaptothiazoles. 

In addition to the syntheses described above, many other processes for the use of formaldehyde in the production of dyes and dy e intermediates are described in the patent hterature. Recent patents,for example, includethe production of benzene-soluble azo dyes by coupling diazotized arj lamines with aromatic hydroxy compounds plus formaldehyde , preparation of vat dyes by condensation of formaldehyde with ST-dihy di O-l,2,T,2 -anthra-quinone azities , synthesis of nitroso dy es by. reacting formaldehyde viith p-X-alky laminonitrosoben2ene del i atives, formation of thiazole dyes from mercaptothiazoles, primary amines, and foimaldehyde , production of diphenyimethane intermediates , etc. 

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