L-Thia-3,4-diazoles

The hydroxy-l-thia-2,4-diazole 125 is reported to exhibit phenolic character and to give a red color with ferric chloride. Infra-rediooa.142,143 ultraviolet spectral evidence indicates that 1-thia-3,4-diazoles of type 126 exist predominantly in an oxo form,... 

The structure of 5-amino-l-thia-2,4-diazoles has been clarified by Goerdeler, Huppertz, and Wember who compared the ultraviolet spectra and basicities of 194 (E, = Me or Ph) and the methylated derivatives 195 and 196, thereby showing that 194 exists in the amino form. This conclusion is supported by polarographic data. ... 

Nitrosamino-3-phenyl-l-thia-2,4-diazole was assigned structure 219 (R = H) by comparison of its ultraviolet spectrum with those of compounds 219 (R — Me) and 220 in which the double bond is fixed... 

The tautoraerism of certain difunctional derivatives of l-thia-3,4-diazole has received considerable attention. Pala assigned structure 156 to 2,5-dimercapto-l-thia-3,4-diazole on the basis of infrared spectral data, and Thorn" reached the same conclusion by comparing its ultraviolet spectrum (measured in ethanol) with those of the four possible methylated derivatives. However, the infrared spectrum of a chloroform solution of the parent compound showed bands at 2600-2550 cm indicating an SH group and the probable occurrence of form 157 under these conditions, and this conclusion is supported by the occurrence of SH bands in solid state spectra obtained by Swiss investigators. For a summary of earlier work on these compounds, see reference 187. 

Jan-niah and reported that 2-amino-l-thia-3,4-diazol-5-... 

Substituted 2-amino-l-thia-3,4-diazoles have been studied by Testa et Comparison of ultraviolet and infrared spectra of the parent compound (197 198) with those of its four possible methylated derivatives indicated that 197 predominates in aqueous solution and... 

The properties of the diazotization product of 2-aminothiophenol are completely different from those of 2-aminophenol. In the reaction shown in Scheme 6-44 the diazo-thiophenolate (6.66) is not detected at all. The benzo-l-thia-2,3-diazole (6.67) is the stable product. A comparison of spectral data for diazophenoxide (6.63), benzo-l-oxa-2,3-diazole (6.64), and benzo-l-thia-2,3-diazole (6.67) is given in Section 4.2. The l-thia-2,3-diazole structure was first postulated by Le Fevre et al. (1954) on the basis of infrared spectra. 

Benzopyrazoles, see Indazoles Benzo-l-thia-2,3-diazole 136 f., 192, 225 Benzo-l,2,3-triazene 225 Benzotriazinones 133 f. 

Janniah and Guha18S>189 reported that 2-amino-l-thia-3,4-diazol-5-thione (158) exists in two forms the sterically-unaceeptable bridged structure 159 was postulated for one of these forms. Bambas190 suggests instead that the two forms may be the individual tautomers 160 and 161. The second explanation is hardly more probable than the first, and the whole problem needs reinvestigation. Certain related compounds with a substituted-amino group have been shown by ultraviolet spectral comparisons to exist in the thione form.190 ... 

Sheinker and his co-workers263 have used ultraviolet and infrared spectroscopic data to show that the imino form of benzenesul-fonamido derivatives of thiazoles and l-thia-3,4-diazoles is preferred to the amino form by a large factor. In view of this work, the formulation of 2-arylsulfonamidooxazoles in the amino form on the basis of chemical evidence260 must be regarded with caution. 

The 3-alkylthio groups in 1,2,4-thiadiazoles are difficult to replace. Thus, 3-alkylthio-l,2,4-thia-diazoles resist the action of aniline at 100°C, ammonia at 120°C, molten urea and ammonium acetate however, hydrazine attacks 3-methylthio-l,2,4-thiadiazole (142) forming 3-amino-1,2,4-triazole (143) (Equation (21)) <65AHC(5)119>. In contrast to 3-alkylthiogroups, 5-sulfonyl groups in... 

Cyclic amidines (213) react with chlorocarbonylsulfenyl chloride to give bicyclic 1,2,4-thia-diazoles. The product isolated from this reaction depends on the mode of addition. When (213) is added to chlorocarbonylsulfenyl chloride, 3-oxo derivatives (214) are isolated via the postulated intermediate (215). Addition of chlorocarbonylsulfenyl chloride to (213) leads to 5-oxo derivatives (216), via the proposed bis(intermediate) (217) (Scheme 47) <84CHEC-I(6)463). Cyclic amidines (213) have also been treated with 1-chloro-l-phenyliminomethanesulfenyl chloride (210) to afford 2>H-1,2,4-thiadiazoles (218). The other possible product from this reaction, the 2/7-isomer (219) has been shown to be unstable, rearranging to a benzothiazole. Heterocycles (213) which have been used in this transformation include 2-aminopyridine, 3-aminopyridazine, 2-aminobenzothiazole, 2-aminopyrimidine and 2-aminothiazole (Equation (33)) <86S1027>. 

The first synthesis of an azido substituted 1,2,4-thiadiazole has been reported <86CC800>. When l-alkyl-5-aminotetrazoles (284) are heated with an excess of thionyl chloride, 3-azido-l,2,4-thia-diazoles (130) are formed via the proposed intermediate (285) (Scheme 65). 

Microwave spectroscopy indicates that aromaticity diminishes in the order 1,2,5-thia-diazole > thiophene > l,3,4-thiadiazole> l,2,5-oxadiazole> 1,2,4-oxadiazole <84CHEC-1(4)545, B-85MI 410-01>. The aromaticity of heterocycles has been discussed by Katritzky and Barczynski (90JPR885) and by Bird <94H(37)249>. The thermal stability of 2,5-substituted thiadiazoles (23) was studied by differential scanning calorimetry and shown to increase as the rt-contribution of the substituents becomes greater <89MI410-01>. 

Dialkyl-l,2,4-oxadithiolane-2-5 -oxides (160) have been synthesized from the dihydro thia-diazole (161) via nitrogen extrusion and 1,3-dipolar cycloaddition of the intermediate ylide with sulfur dioxide (Scheme 45) <90BSB265>. The formation and trapping of carbonyl oxides is described... 

By successive quatemization of 3-phenyl-5-methylthio-l,2,4-thia-diazole (324) with dimethyl sulfate at 130°, and treatment with hydrazine hydrate, the hydrazone (326) is obtained the oily material is advantageously isolated as the p-nitrobenzalazine.201 This direct replacement by hydrazine in related heterocycles (e.g. 1,3,4-thiadiazoles,... 

Amino-3-hydroxy(or alkoxy or aryloxy)-l,2,4-thia-diazoles and homologs... 

It is interesting to note that 3,5-diphenyl-l,2,4-oxadiazole (155) undergoes a slow ring cleavage on irradiation in ether, giving benzoyl-benzamidine (156) and 2-phenyl-4-quinazolone (157) as major products.140 Ring cleavage also occurs in 1,2,5-oxadiazoles, 1,2,5-thia-diazoles, and 25-1,2,3-triazoles.141... 

In addition, the following have been described as diazo components 2,5-dichloro-4-nitroaniline (red) [49], 2-chloro-5-trifluoromethylaniline (yellow) [50], 4-nitro-2-trifluoromethylaniline (red) [51], 2-amino-5-trifluoromethyl-l,3,4-thia-diazole (red) [52], 3-methylmercapto-5-amino-l,2,4-thiadiazole (red) [53], 3-methyl-4-nitro-5-aminoisothiazole (blue-violet) [54], 2-amino-6-chlorobenzothia-zole (red) [55], and 3-amino-5-nitro-7-bromobenzisothiazole (blue with a red cast) [56],... 

Upon heating in boiling toluene in the presence of excess triphenylphosphine, l,3-dithiolo[4,5-c] [l,2,5]thiadiazole-5-thione underwent desulfurization to afford 5-[l,3]dithiolo[4,5-c][l,2,5]thia-diazol-5-ylidine (13) (Equation (6)). When trialkylphosphines were used instead of triphenylphosphine a complex mixture of products resulted <93H(35)69>. 

Electronic Structure of Benzo-2,l,3-thia- and -selena-diazoles 523... 

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