thiazole - Thiazoles and thiazolium salts, Organic synthesis, Organic reactions

C₃H₃NS, boiling point 117°C. A five-membered ring compound; a colourless liquid, the basis for a range of dyestuffs. This ring system occurs in vitamin B₁ (thiamine).

Thiazole
Chemical formula
Molar mass	85.128 g mol−1
Systematic name	1,3-thiazole
Complete data

Thiazole, or 1,3-thiazole, is an organic chemical compound with the empirical formula C3H3NS.

Thiazole is used for manufacturing biocides, fungicides, pharmaceuticals, and dyes.

Thiazoles and thiazolium salts

Thiazoles are a class of organic compounds related to azoles with a common thiazole functional group.

The thiazole moiety is a crucial part of vitamin B1 (thiamine) and epothilone. Other important thiazoles are Benzothiazoles for example the firefly chemical luciferin. Thiazole dyes are used for dying cotton.

Oxazoles are related compound with sulfur replaced by oxygen.

Organic synthesis

Various laboratory methods exist for the organic synthesis of thiazoles.

The Hantzsch thiazole synthesis (1889) is a reaction between haloketones and thioamides. Certain thiazoles can be accessed though application of the Herz reaction.

Organic reactions

Thiazoles are characterized by larger pi-electron delocalization than the corresponding oxazoles and have therefore greater aromaticity.

The calculated pi-electron density marks C5 as the primary electrophilic site and C2 as the nucleophilic site.

The reactivity of a thiazole can be summarized as follows:

Deprotonation at C2, the negative charge on this position is stabilized as an ylide. Electrophilic aromatic substitution at C5 requires activating groups such as a methyl group in this bromination: Nucleophilic aromatic substitution often requires an electrofuge at C2 such as chlorine with Organic oxidation at nitrogen gives the thiazole N-oxide. Some of the oxidation takes place at sulfur leading to a sulfoxide : Thiazoles are formyl synthons. Thiazoles can react in cycloadditions but in general at high temperatures due to favorable aromatic stabilization of the reactant.