Diazol

The aromatic character is critically dependent upon the position of the heteroatoms in the ring, and oxygenated compounds have marked diene character. Various ERE determinations of 1,2,4-triazole have given values ranging between 83.7 and 205.8 kJ moP (Table 35). LCAO-SCF calculations, however, suggest that the ring is substantially less stable than the diazoles but more stable than tetrazole. 

DIAZINON AG 600 WBC , diazinon, 50 DIAZOL , diazinon, 50 Diazomethane, 50 Dibenz(a,h)anthracene, 50 Dibenzofuran, 51 DIBK, 51 Diborane, 51 DIBROM , naled, 51 Dibromobenzene, 51 Dibromochloromethane, 51... 

Conjugated 1,3-diazadienes are oxidized by m-chloroperoxybenzoic acid to I-oxa-2,4-diazoles [SS] (equation 80)... 

In addition to intermolecular interactions in the solid state, the relative importance of the two resonance structures A and B is an important issue in the structural determinations of selena- and tellura-diazoles. ° The Se-N bond lengths fall within the range 1.78-1.81 A and the Te-N bond lengths are 2.00-2.05 A compared to single bond values of 1.86 and 2.05 A, respectively. It can be concluded that resonance structure A is more important than B for the Se and, especially, the Te... 

Pyrro-nfd-diazole was first obtained by the ovidation ofazimido-toluene, which in tinn was prepared by the action of iiitious acid on u-toluylenediamine. 

The benzofuroxtin [benzofurazan oxide, 3,4-benzo-l,2,6-oxa-diazole-2-oxide, or 2,1,3-benzoxadiazole-l-oxide (1)] ring system has been reviewed briefly on several occasions, notably by Kaufman and Picard,Boyer, and Behr. The mqst recent of these covers the literature until 1959, and since that date there have been many advances in the subject. This, we feel, justifies the field being covered once more, and its separation from the monocyclic 1,2,5-oxadiazole oxides—the furoxans. We consider also other furoxano-fused compounds in this chapter, subject to the limitation that the ring adjacent to the furoxan is aromatic and six-membered. 

The Hurd-Mori synthesis of 1,2,3-thiadiazoles from a-methylene ketones developed in 1955 is, even today, the method of choice for a number of 1,2,3-thia-diazole derivatives. Both the mechanism and the regiochemistry have been extensively studied, but since the isolation of the intermediate by Hurd and Mori (84CHEC-I(6)460), there has been no further work supporting the formation of this intermediate or its conversion into the aromatization product. In 1995 Kobori and coworkers published the isolation of several 1,2,3-thiadiazolin-1-oxides 186, finally demonstrating their participation in the formation of 1,2,3-thiadiazoles. Substituents R and R play an important role in the isolation of 1,2,3-thiadiazolin-1-oxide (95H(41)2413). 

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 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-... 

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. ... 

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... 

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... 

Thiazole with M(CO)6 gives N-coordinated complexes of composition [M(C0)5L] (M = Cr, Mo, W) (81IC2778). Thia(selena)diazole complexes of similar nature and composition are known (81ZN(B)172, 83CB230, 91JOM(405)309). 

Step C Preparation of 3-Morpholino-4-(3-tert-Butylamino-2-Oxopropoxy)-1,2,5-Thia-diazole — The 1-toluenesulfonyloxy-2-oxo-3-tert-butylaminopropane, prepared as described in Step B, (11 mols) is added to 0.80 N methanolic sodium methoxide (15 ml) at 0°C. The mixture is stirred for 15 minutes at 0° to 5°C, treated with 3-morpholino-4-hydroxy-1,2,5-thiadiazole (4.29 grams) and then refluxed for 16 hours. The solvent is evaporated in vacuo and the residue is treated with excess potassium carbonate to provide 3-morpholino-4-(3-butylamino-2-oxopropoxy)-1,2,5-thiadiazole. 

Phenoxaphosphine ring-containing poly (1,3,4-oxa-diazoles) were synthesized by cyclodehydration of poly-hydrazides obtained from (BCPO) and aliphatic and aromatic dihydrazines [152]. All these polymers are soluble in formic acid, w-cresol and concentrated H2SO4. The polyhydrazides yield transparent and flexible films when cast from DMSO solution under reduced pressure at 80-100°C. The polyhydrazides exhibit reduced viscosities of 0.24-0.40 dl/g in DMAC. Phenoxaphosphine ring-containing oxadiazole polymers showed little degradation below 400°C. 

The soft Au+ forms relatively few complexes compared with those of phosphines. Complexes with ammines, nitriles and diazoles like Au(NH3)2 and Au(RCN)2 are known but little studied. In linear Au(NH3)2, Au-N is 2.01-2.03 A [70a], [Au(NCPh)2]+ has been used as a labile source of other gold complexes [70b]. AuCl(piperidine) is a monomer with weak tetra-meric association in contrast AuX(py) (X = Cl, Br, I) are [Aupy2]+[AuX2] with a chain structure in the solid state (and Au-Au interactions), suggesting a close balance between factors for molecular and ionic structures [70c] (note also the tetrahydrothiophene complexes in section 4.10.6). 

The diazotization of heteroaromatic amines is basically analogous to that of aromatic amines. Among the five-membered systems the amino-azoles (pyrroles, diazoles, triazoles, tetrazoles, oxazoles, isooxazoles, thia-, selena-, and dithiazoles) have all been diazotized. In general, diazotization in dilute mineral acid is possible, but diazotization in concentrated sulfuric acid (nitrosylsulfuric acid, see Sec. 2.2) or in organic solvents using an ester of nitrous acid (ethyl or isopentyl nitrite) is often preferable. Amino derivatives of aromatic heterocycles without ring nitrogen (furan and thiophene) can also be diazotized. 

In an analogous way heteroaromatic diazonium ions that contain an acidic NH group in the heteroaromatic ring, e. g., the diazole, triazole, and tetrazole derivatives 5.1, 5.2, and 5.3, lose that proton even in weakly to strongly acidic solutions, as... 

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. 

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