Thiazoles and Selenazoles

General.—The three-part book on thiazoles, which includes a chapter on selenazoles, has been mentioned earlier. 

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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. 

Furthermore, the strongly metallic character of selenium weakens the C-Se bond and thus favors reactions involving opening of the ring. The basicity of the three heterocycles is approximately in the same order, the nitrogen atom of selenazole and thiazole possessing much the same properties as the heteroatom of pyridine. Of the two carbon atoms ortho to nitrogen, that is, the 2-carbon and the 4-carbon, only the one in the 2-position is fairly active as a result of its interaction with selenium or sulfur. The 4- and 5-positions of thiazole and selenazole are more susceptible to electrophilic substitution than the 3- and 5-positions of pyridine. This is particularly true of the 5-position of selenazole. Thus it can be said that the 2- and 5-positions of the selenazoles and thiazoles... 

These derivatives occur when 6-benzalamino-2-phenylbenzoselenazole is fused with sulphur, and contain both the thiazole and selenazole groupings, the structure being numbered as follows ... 

F.T. Burling, B.M. Goldstein, Computational studies of nonbonded sulfur-oxygen and selenium-oxygen interactions in the thiazole and selenazole nucleosides. J. Am. Chem. Soc. 114, 2313-2320 (1992)... 

Napolitano E, Pelosi P. Synthesis of thiazole and selenazole derivatives with affinity for the odorant-binding protein. Bioorg. Med. Chem. Lett. 1992 2 1603-1606. 

Violene Radicals from Oxazoles, Thiazoles, and Selenazoles... 

The cycloaddition of mesoionic thiazoles and selenazoles was explained using second-order perturbation theory, limited to frontier orbitals. Only a detailed study of the sulfur case was reported, but an understanding of the selenium model may be gained <82T2129>. 

Thiazolo[4,5-d]-oxazole, -thiazole, and -selenazole [C NX-CiNS], The cycloaddition of ethyl 3-p-anisyl-5-bromo-4-oxothiazolidin-2-ylidenecyano-acetate with KOCN gives the 2,3,4,5-tetrahydrothiazolo[4,5-d] oxazol-2-one derivative (227 X = 0). The sulphur and selenium analogues can be obtained, starting from KSCN and KSeCN, respectively. 

Kumar Y, Green R, Borysko K. Z, Wise D. S, Wotring L. L, Townsend L. B. Synthesis of 2,4-disubstituted thiazoles and selenazoles as potential antitumor and antifilarial agents. 1. Methyl 4-(isothiocyanatomethyl)thiazole-2-carbamates, -selenazole-2-car-bamates, and related derivatives, J. Med. Chem. 1993. p. 3843 - 3848. DOI 10.1021/ jm00076a012... 

Incorporation of Fluorine Groyps into Thiazoles and Selenazoles. 442... 

Abstract This chapter provides information about the methods of synthesis, chemical properties and applications of flnorine-containing oxazoles, thiazoles and selenazoles and their benzo analogues. 

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