1,2-Oxa/thia-3-azoles

This chapter describes the chemistry of 1,2,3-dithiazoles and 1,2,3-oxathiazoles. 1,2,5-Oxathiazoles have not been reported at this time. New families of neutral heterocyclic 1,2,3-dithiazolyl radicals have been investigated by density functional theory and ab initio theoretical calculations, and a range of experimental methods including X-ray diffraction, electron spin resonance spectroscopy, and cyclic voltammetry, and have been proposed as synthetic conductors. A new application of Burgess and Burgess-type reagents in preparation of enantiopure 1,2,3-oxathiazole di-S-oxides has been developed; oxiranes and vic-diols were involved in this transformation. The reaction of cyclic sulfamidates with nucleophiles was extensively studied; three types of products were formed: by nucleophilic displacement of sulfamide and proton abstraction at carbon atoms. A new chemistry of 4-chloro-1,2,3-dithiazolo-5-imines, 5-one, 5-thione, and 5-ylidenes readily obtained from Appel salt (4,5-dichloro-1,2,3-dithiazolium chloride) was an important subject; a number of heterocyclic (quinazolines, thiadiazole oxides, benzimidazoles, etc.) and nitrogen-containing compounds (amidines, isothiocyanates, formamidoximes, and thioformamides) were obtained. The reactivity of cyclic sulfamidates has been studied to give enantiopure aminoacids, β-aminoalcohols, and sugars with functional groups.