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.
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.
^The Chemistry of Heterocycles : Structure, Reactions, Syntheses, and Applications Theophil Eicher, Siegfried Hauptmann ISBN 3-527-30720-6
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^ George Schwarz (1955). "2,4-Dimethylthiazole". Org. Synth.; Coll. Vol.3: 332.
^ ab Mateo Alajarín, José Cabrera, Aurelia Pastor, Pilar Sánchez-Andrada, and Delia Bautista (2006). "On the [2+2] Cycloaddition of 2-Aminothiazoles and Dimethyl Acetylenedicarboxylate. Experimental and Computational Evidence of a Thermal Disrotatory Ring Opening of Fused Cyclobutenes". J. Org. Chem.71 (14): 5328 - 5339. doi:10.1021/jo060664c.
^ ab Alessandro Dondoni and Pedro Merino (1998). "Diastereoselective Homologation of D-(R)-Glyceraldehyde Acetonide using 2-(Trimethylsilyl)thiazole". Org. Synth.; Coll. Vol.9: 952.
^ Elizabeta Amir and Shlomo Rozen (2006). "Easy access to the family of thiazole N-oxides using HOF·CH3CN". Chemical Communications2006: 2262 - 2264. doi:10.1039/b602594c.