3- Phenyl-1,2,4-triazole

The nmr of the isolated metabolite 5, a glucuronide, suggested that it existed as a mixture of rotational isomers (rotamers), as did the acylat glucuronide 6, due to the hindered rotation about the triazole-phenyl bond. When the structure was confirmed by synthesis from 2-amino-6-methylbenzothiazole, 7, by a series of steps outlined in Scheme 2, the synthesized glucuronides also appeared to exist as a mixture of rotamers. Further, these rotamers were separate as the acylated ucuronides by liquid chromatography and characterized by their nmr spectra which differed in the proton resonances of the peaks assigned to the 2-methyl, the thiomethyl, and the triazole hydrogen. 

When either pure rotamer was heated in diphenylether at 200°C they reverted to a mixture of rotamers, as determined by the nmr spectra of the mixture. Computer modeling of 5 and 6 further suggested that the rotation about the triazole-phenyl bond could be hindered by the bulky groups in the 2-and 6-posidons on the phenyl ring. 

C2N3 N N N — — l,3-Dimethyl-4-(l,2,3-triazolyl) sulfide 3-methyl-2-phenyl-l,2,3-triazol-l-ine-4-thione... 

Ring substituents can have a considerable effect on the acidity of the system. In the 1,2,4-triazole series a 3-amino group decreases the acidity to 11.1, a 3-methyl group to 10.7, whereas a 3-phenyl group Increases the acidity to 9.6, and 3,5-dlchloro substitution to 5.2 (71PMH(3)1). 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

N-Unsubstituted 1,2,3-triazoles are methylated mainly in the 1-position with methyl iodide and silver or thallium salts, but mainly in the 2-position by diazomethane. There is also some steric control. For example, 4-phenyl-l,2,3-triazole with dimethyl sulfate gives the 2-methyl-4-phenyl (38%) and l-methyl-4-phenyl isomers (62%), but none of the more hindered 1-methyl-5-phenyltriazole (74AHC(16)33). JV-Unsubstituted 1,2,4-triazoles are generally alkylated at N-1. 

Enamines and enolate anions react with benzofuroxan to give quinoxaline di-A -oxides (Scheme 38) (69AHC(10)1). Sydnones (274) with phenyl isocyanate give 1,2,4-triazoles (275) (76AHC(19)l), and from (276) the intermediate adduct (277) can be isolated (73JA8452). This is one of the few instances in which such primary cycloadducts have been isolated in the oxazole series of mesoionic compounds. 

Oxidation of the hydrazone of 2-hydrazinopyrazole (226) with Pb(OAc)4 in CH2CI2 is a two-step reaction. The azine (227) was formed as an intermediate and this underwent ring closure to the 3H-pyrazolo[5,l-c][l,2,4]triazole (228) (79TL1567). A similar reaction applied to the benzal derivative of 2-hydrazinobenzothiazole (229) gave 3-phenyl-[l,2,4]triazolo[3,4-6]benzothiazole (230) together with a by-product (231) (72JCS(P1)1519). 

The 1-azirines obtained from the vapor phase pyrolysis of 4,5-disubstituted 1-phthalimido-1,2,3-triazoles (157) have been found to undergo further thermal reactions (71CC1S18). Those azirines which contain a methyl group in the 2-position of the ring are cleaved to nitriles and phthalimidocarbenes, whereas those azirines which possess a phenyl substituent in the 2-position rearrange to indoles. 

Triazole-l-carboxylic acid, 4-phenyl-, ethyl ester... 

Triazole-4-carboxylic acid, 5-chloro-1-phenyl-UV, 5, 685 (55JA6532)... 

Thieno[3,4-d][ 1,2,3]triazole, tetramethyl-synthesis, 6, 1015 Thieno[3,4-c][ 1,2,3]triazoles synthesis, 6, 1042 Thieno[3,4-d][ 1,2,3]triazoles reactions, 6, 1036 synthesis, 6, 1044 Thienyl radicals generation, 4, 832 Thiepane, 2-acetoxy-synthesis, 7, 574 Thiepane, 2-chloro-nucleophilic substitution, 7, 573 synthesis, 7, 574 Thiepane, 2-methyl-synthesis, 7, 573 Thiepane, 2-phenyl-synthesis, 7, 573 Thiepane, 3,3,6,6-tetramethyl-cycloaddition reactions, 7, 574 Thiepanes, 7, 547-592 applications, 7, 591... 

Triazole, 5-amino-1-phenyl-Dimroth rearrangement, 5, 94 4-substituted... 

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