2- azole-4-sulfonic

Sulfonation conditions are given in Table 4. The orientation is as expected. Azolinones react as readily as the corresponding azoles sulfonation of (117) occurs at the positions indicated (H2SO4/SO3 at 100 °C). Imidazoles are readily chlorosulfonated at C-4. 

Hasiotis, C. et al.. Development and characterization of acid-doped polybenzimid-azole/sulfonated polysulfone blend polymer electrolytes for fuel cells, J. Electrochem. Soc., 148, A513, 2001. 

Xu, C., Cao,Y, Kumar, R., Wu, X., Wang, X., and Scott, K. (2011) A polybenzimid-azole/sulfonated graphite oxide composite membrane for high temperature polymer membrane fuel cells, J. Mater. Chem., 21, 11359-11364. 

Amination at an azole ring nitrogen is known for Af-unsubstituted azoles. Thus 4,5-diphenyl-1,2,3-triazole with hydroxylamine-O-sulfonic acid gives approximately equal amounts of the 1- (104) and 2-amino derivatives (105) (74AHC(16)33). Pyrazole affords (106) and indazole gives comparable amounts of the 1- and 2-amino derivatives. 

In azole chemistry the total effect of the several heteroatoms in one ring approximates the superposition of their separate effects. It is found that pyrazole, imidazole and isoxazole undergo nitration and sulfonation about as readily as nitrobenzene thiazole and isothiazole react less readily ica. equal to m-dinitrobenzene), and oxadiazoles, thiadiazoles, triazoles, etc. with great difficulty. In each case, halogenation is easier than the corresponding nitration or sulfonation. Strong electron-donor substituents help the reaction. 

The general discussion (Section 4.02.1.4.1) on reactivity and orientation in azoles should be consulted as some of the conclusions reported therein are germane to this discussion. Pyrazole is less reactive towards electrophiles than pyrrole. As a neutral molecule it reacts as readily as benzene and, as an anion, as readily as phenol (diazo coupling, nitrosation, etc.). Pyrazole cations, formed in strong acidic media, show a pronounced deactivation (nitration, sulfonation, Friedel-Crafts reactions, etc.). For the same reasons quaternary pyrazolium salts normally do not react with electrophiles. 

It is important to note that SNAr displacement reactions of heteroatom functional groups other than halides have been demonstrated on purine substrates, including mesitylenesulfonates <20000L927>, sulfones (see Section 10.11.7.5), nitro substituents <2006S2993>, and T-azoles (see Section 10.11.7.3.2). Halopurines have been reduced using sodium naphthalenide <1997T6295>. 

Thiazoles, vinyl-radical polymerization, 6, 278 Thiazole-5-sulfonic acid, 2-amino-synthesis, 6, 255-256 Thiazole-2-sulfonic acids reactions, 5, 104 6, 291 Thiazole-5-sulfonic acids synthesis, 6, 255 Thiazole-5-thione, 2-phenyl-tautomerism, 6, 249 Thiazolethiones reactivity, 6, 250 Thi azole-2-thiones reactions, 5, 102 tautomerism, 5, 367 Thiazolidine, 2-alkyl-occurrence, 6, 327 Thiazolidine, 2-arylimino-X-ray analysis, 6, 238 Thiazolidine, 4-imino-mesoionic didehydro derivative nomenclature, 1, 34 nomenclature, 1, 34... 

Oxidation of sulfur-containing azoles quite often leads to the formation of sulfones and sulfoxides. Thus, 3-alkyl-1,2-benzisothiazoles 142 with MCPBA give the oxaziridines 143, and the use of a chiral 3-alkyl substituent leads to pure diastereomers. Reaction of 1,2,3-benzothiadiazole with 30% hydrogen peroxide in a mixture of acetic acid and methanol for 45 days affords 144 in 60% yield. 

Wycisk, R., Lee, J.K., and Pintauro, P.N., Sulfonated polyphosphazene-polybenzimid-azole membranes for DMFCs, J. Electrochem. Soc., 152, A892, 2005. 

Sulfur is a useful link for heterocycles because its use as a leaving group (or better, after conversion to sulfoxide or sulfone) can bring about cleavage from the support combined with addition of a nucleophile. This method has been nsed for both azoles and azines, as shown below. 

Carboxymethylaminomethy 1)azole-4-sulfonic acid (N-(4-sulfonyl-2-pyrrylmethyl)glycine)... 

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