AskDefine | Define thiazole

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Noun

  1. Any of a class of unsaturated heterocyclic compounds containing a ring of three carbon atoms, a sulphur and an nitrogen atom; especially the simplest one, C3H3SN.

Extensive Definition

Thiazole, or 1,3-thiazole, is a clear to pale yellow flammable liquid with a pyridine-like odor and the molecular formula C3H3NS. It is a 5-membered ring, in which two of the vertices of the ring are nitrogen and sulfur, and the other three are carbons .
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. Thiazoles are aromatic.
The thiazole moiety is a crucial part of vitamin B1 (thiamine) and epothilone. Other important thiazoles are benzothiazoles, for example, the firefly chemical luciferin.
Thiazoles are structurally similar to imidazoles. Like imidazoles, thiazoles have been used to give N-S free carbenes and transition metal carbene complexes.
The amino atom can be alkylated to create a thiazolium cation; thiazolium salts are catalysts in the Stetter reaction and the Benzoin condensation. Thiazole dyes are used for dying cotton.
Oxazoles are related compounds, with sulfur replaced by oxygen. Thiazoles are well represented in biomolecules; oxazoles are not.

Organic synthesis

Various laboratory methods exist for the organic synthesis of thiazoles.

Reactions

Thiazoles are characterized by larger pi-electron delocalization than the corresponding oxazoles and have therefore greater aromaticity. This is evidenced by the position of the ring protons in proton NMR (between 7.27 and 8.77 ppm), clearly indicating a strong diamagnetic ring current.
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:
2-(trimethylsiliyl)thiazole (with a trimethylsilyl group in the 2-position) is a stable substitute and reacts with a range of electrophiles such as aldehydes, acyl halides, and ketenes
  • Thiazoles can react in cycloadditions, but in general at high temperatures due to favorable aromatic stabilization of the reactant; Diels-Alder reactions with alkynes are followed by extrusion of sulfur, and the endproduct is a pyridine; in one study , a very mild reaction of a 2-(dimethylamino)thiazole with dimethyl acetylenedicarboxylate (DMAD) to a pyridine was found to proceed through a zwitterionic intermediate in a formal [2+2]cycloaddition to a cyclobutene, then to a 1,3-thiazepine in an 4-electron electrocyclic ring openening and then to a 7-thia-2-azanorcaradiene in an 6-electron electrocyclic ring, closing before extruding the sulfur atom.

References

thiazole in German: Thiazol
thiazole in Italian: Tiazolo
thiazole in Latvian: Tiazols
thiazole in Japanese: チアゾール
thiazole in Polish: Tiazol
thiazole in Turkish: Tiyazol
thiazole in Chinese: 噻唑
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