Thiatriazolium-5-olates

Proton NMR data are reported for substituted mesoionic l,2,3,4-thiatriazolium-5-olates and 5-thiolates. Although the spectra are of little diagnostic value they are consistent with the mesoionic structures <79JCS(P1)732>. Representative C shifts for C(5) of 5-substituted thiadiazoles are 5-Ph, 178.46 ppm 5-PhNH, 173.8 ppm 5-BzS, 179.8 ppm 5-PhCOS, 171.5 ppm and for the thiatriazolium salt (9) 186.42 ppm <84CHEC-I(6)579>. 

Araki et al. have found that La wesson s reagent, 2,4-bis(4-methoxyphenyl)-l,3-dithiaphos-phetane-2,4-disulflde, provides a convenient one-step conversion of mesoionic olates to mesoionic thiolates <88BCJ2977>. Thus 3-phenyl-1,2,3,4-thiatriazolium-5-olate (170) was converted to (171) in high yield by refluxing for 50 min in benzene (Equation (14)). This eompound had previously been prepared from compound (161 R = Ph) by treatment with sodium sulfide in aqueous dimethyl-formamide at room temperature <79JCS(Pi)732>. 

Mesoionic 1,2,3,4-oxatriazolium-5-thiolates (172) are convenient starting materials for mesoionic thiatriazole 5-oxides. Thus arylhydrazines and carbon disulfide in ethanol yield arylhydrazinium dithiocarbamate salts, which are nitrosated with sodium nitrite in aqueous hydrochloric acid to give yellow l,2,3,4-oxatriazolium-5-thiolates (172). These heterocycles are isomerized by warming with ammonium hydroxide in ethanol to give colorless crystalline l,2,3,4-thiatriazolium-5-olates (173) (Scheme 36) <76CC306>. 

Corresponding thiatriazolium tetrafluoroborates (161 R = Ar) salts are formed by Meerwein alkylation (triethyloxonium tetrafluoroborate in methylene chloride) of the 5-olates (173) <76CC306>. This type of salt (161) generally serves as starting material for other types of mesoionic compound <76AHC(l9)i>. The l,2,3,4-thiatriazolium-5-olates (173) are reported to be stable towards acid hydrolysis while aryl azide is formed in boiling aqueous sodium hydroxide <76CC306>. 

Sulfide 130 can be alternatively prepared in 93% yield by treatment of 3-phenyl-l,2,3,4-thiatriazolium-5-olates 38 with Lawesson s reagent (2,4-bis(4-methoxyphenyl)-l,3-dithiaphosphetane-2,4-disulfide) 129 (Equation 7) <1988BCJ2977>. 

Alkylation of 3-aryl-l,2,3,4-thiatriazolium-5-olates 38 with triethyloxonium tetrafluoroborate leads to 5-ethoxy substituted thiatriazolium salts 37 (R = Ar) <1975T1783>. In the same manner, the aminides 129 react with iodo-methane to afford the thiatriazolium salts 131 with disubstitution at the exocyclic nitrogen (Scheme 31) <1998JMT27>. Also the mesoionic compounds 127 are readily alkylated with different alkylating agents <1997MRC124>. 

The application of mesoionic compounds, including 3-phenyl-l,2,3,4-thiatriazolium-5-olate, was found to increase the conductivity of DMF based gels <2001PCB9686>. 

Sulfates 83Low, 86Bar, 88Hel l,2,3,4-Thiatriazolium-5-olates 99Jaz... 

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