1.3.4- Thiadiazolium-2-thiolates

Zur Azogruppen-Ubertragung auf 1,3,4-Thiadiazolium-2-thiolat kann auch Dimethoxy-carbonyl-diazen verwendet werden4 z.B. ... 

The mesoionic 4,5-diphenyl-1,3,4-thiadiazolium-2-thiolate (114) reacts with methyl azodicarboxylate to yield the azothiadiazole (115) and not the tetrazine betaine (116) as previously claimed. Compound (115) can also be prepared from 2-amino-5-phenyl-l,3,4-thiadiazole and nitrosobenzene (71CC837). 

Mesoionic compounds (Section 5.07.1.3) are fully aromatic and usually have an exocyclic heteroatom bearing a charge attached to the ring. A new one-step method for converting the exocyclic oxygen of 3-phenyl-l,2,3-thiadiazolium-5-olate 52 into the exocyclic sulfur of 3-phenyl-l,2,3-thiadiazolium-5-thiolate 53 makes use of Lawesson s reagent (Equation 14) <1988BCJ2977>. 

Thiadiazolium-S-olat 3-Phenyl-E8d, 91 (3-Ar—1,2,3-oxadiazo-lium — 5-thiolat-Umlager.)... 

The reaction of 4,5-diphenyl-l,3,4-thiadiazolium-2-thiolate (169) with dimethyl azodicarboxylate does not yield a six-membered mesionic system (172) as previously claimed. The orange product, formed in 30% yield in... 

Meso-ionic l,2,5-thiadiazolium-4-olates (138) are obtained by the action of sulphur monochloride on the A -methylated amino-acid amide (137) " see Scheme 10. Several other meso-ionic thiadiazole derivatives have been reported, especially l,2,3-thiadiazolium-4-(and -5-)olates and -thiolates." ... 

Functionalization of Thiadiazole. Mesoionic compounds prepared on the 1,2,3-thiadiazolium scaffold have been studied for their chemical and biological properties and are known to display monoamine oxidase inhibitory activity. The reaction of 1,2,3-thiadiazole with /7-toluenesulfonic acid affords quantitative conversion to thiazolium /7-toluenesulfonate. The thiazolium tosylate can be reacted with sulfur in the presence of sodium hydride in DMF to afford the 5-thiolated mesoionic compound in 48% yield (eqs 1 and 2). ... 

Meso-ionic 1,3,4-Thiadiazoles.—The synthesis and properties of isomeric pairs of l,3,4-thiadiazolium-2-olates (128) and of l,3,4-oxadiazolium-2-thiolates (127) have been described, thus establishing the existence of isomeric meso-ionic compounds, the interconversion of which [(127) (128)] involves an exchange... 

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