1.2.4- Triazoles 3,5-diaryl— from

Copper-mediated synthesis of 1,4-diaryl-l,2,3-triazoles 97 from iV-tosylhydrazones 96 and aniline was reported (13AG(E) 13324). Cu(ll)-catalyzed domino reactions of 2ff-azirines with diazotetramic and diazotet-ronic acids yielded synthesis of 2-substituted-2H-l,2,3-triazoles (130BC5535). Photooxygenation of azidoalkyl furans provided an endo-peroxide intermediate which underwent [3+ 2] cydoaddition to give... 

Cycloadditions have been carried out to 37/-indoles (222, 223) (125,126), N-arylmaleimides (224) (127,128), l,2), -azaphospholes (225) (129), 5(47/)-oxazo-lones (226) (130), and 4,5-dihydrooxazoles (230) (131). The primary cycloadducts from the reaction of oxazolones (e.g., 226 with diaryl nitrile imines), derived from tetrazoles in refluxing anisole, do not survive. They appear to lose carbon dioxide and undergo a dimerization-fragmentation sequence to give the triazole 228 and the diarylethene 229 as the isolated products (130). In cases where the two aryl substituents on the oxazole are not the same, then, due to tautomerism, isomeric mixtures of products are obtained. 

Triazolopyridines and 1,2,4-triazolopyrimidines were synthesized using a modified Mitsunobu reaction starting from acylated 2-hydrazinopyridines and acylated-hydrazinopyrimidines under mild conditions <07ARK132>. A series of 3-alkylthio-4,5-diaryl-4//-1,2,4-triazoles were prepared from benzoic acid hydrazides <07JHC1323>. 

Photochemically induced ring contraction of novel 4-iminodi-hydro-1,2,3-triazoles to the corresponding ( )- and (Z)-aziridin-imines has also been reported. A different pathway is followed in the 6-(l -triazolyl)uracils (24) which on irradiation in acetonitrile were converted into the pyrrolo[2,3-d]pyrimidines (25) via triplet biradical intermediates a novel cyclisation leading to the formation of pyrimido[4,5-c]isoquinolines is observed, however, when C-5 phenyl substituents are present on the triazole ring. Rate constants for the cycloaddition f diarylnitrilimines, generated by photoelimination of nitrogen from diaryl 2H-tetra-zoles, to various dipolarophiles have been determined experiment-... 

Cycloaddition reactions of l,3,4-oxadiazin-6-ones 97 (R = Ph, R = Ar), via their 2,3-diaza-l,3-diene functionality, are observed by treatment with dipolarophiles. Thus, 2,5-diaryl-l,3,4-oxadiazines 97 react with diaryl nitrilimines 115, which are liberated in situ from the corresponding hydrazonoyl chlorides 114 and triethylamine, to give 1//-1,2,4-triazole A -imines 118 and open-chain products 119 <1996JHG591>. It is reasonable to conclude that intermediates 116 are formed initially from cycloaddition across the adjacent carbonyl-carbon nitrogen double bond and that subsequent CO abstraction gives 177-1,2,4-triazole A -imine derivatives 118. The open-chain adducts 119 are formed from intermediates 117, which result from the reaction of 115 at the carbonyl double bond of the oxadiazinones 97 (Scheme 15). 

Triazole is chlorinated at C-3 through a 1-chloro-derivative that can be isolated. The 3,5-dibromo-1,2,4-triazole is prepared from the parent 1,2,4-triazole in a 90% isolated yield.The 3,5-dibromo-1,2,4-triazole can be reacted with stannyl derivatives in a microwave to yield 5-aryl-1,2,4-triazoles that can then be further elaboarated to 3,5-diaryl-1,2,4-triazoles. 

Various synthetic protocols were available for the preparation of 1,2,4-triazoles and derivatives thereof Efhcient synthesis of 3,4,5-tri-substituted 1,2,4-triazoles 171 was accompHshed from the reaction of guanidines 169 with 2,2,2-tri-chloroethylimidates 170 in PEG-400 (14TL177). 3,5-Diaryl-l,2,4-triazoles 173 were synthesized from a domino nucleophilic substitution/ oxidative cycfr-zation sequence from 2 equivalents of amidines 172 with copper catalyst, sodium bicarbonate as base, 1,10-phenanthroline as an additive, and K3[Fe(CN)6]/air as the oxidant (14T1635). Sulfur-substituted 1,2,4-triazoles... 

Among (halkyl and diaryl (3-methylthio-l,2,4-triazol-5-yl)iminodithiocar-bonates prepared from 5-amino-1,2,4-triazoles, carbon disulfide, and an excess of potassium hydroxide with 2 mol equivalents of the corresponding alkyl or aralkyl hahdes, dimethyl (3-methylthio-l,2,4-triazole-5-yl)imino-dithiocarbamate 18 was isolated in both desmotropic forms. The form 18a crystaUized from hot acetonitrile, while the form 18b crystallized slowly from dilute ethanol. Both forms are stable enough in fresh -heptane and benzene-d solutions to give a possibility to differentiate them by UV and NMR (Scheme 12) (1990JHC1689). 

Diaryl-1,2,4-triazoles from carboxylic acid hydrazide sulfonates and nitriles s. 11, 469 o... 

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