3-benzoyl-5-phenyl-l ,2,4-oxadiazole

The role of substituents X on the mononuclear heterocyclic rearrangement (MHR) of 20 phenylhydrazones 54 of 3-benzoyl-5-phenyl-l,2,4-oxadiazole into the triazoles 55 (Equation 2) has been investigated, allowing the influence of X on the product distribution to be evaluated and first-order rate constants and Hammett correlations to be determined <1999T12885>. 

Bei der Oximierung von 3-Benzoyl-5-phenyl-l,2,4-oxadiazol wird ein Gemisch aus 3-( -Hydroximino-benzyl)-5-phenyl-l,2,4-oxadiazol (III 33%) und 4-Benzoylamino-3-phenyl-fura-zan (V 57%) erhaltcn107 ... 

Da unter den Reaktionsbedingungcn das Oxim IV sich zum Furazan V umlagcrt, kann angenommen werden, daB bei dcr Umsetzung von 3-Benzoyl-5-phenyl-l,2,4-oxadiazol mit Hydroxylamin zum Furazan V die Stufe des (Z)-Oxims IV durchlaufen wird. Das Verhiiltnis Oxim/Furazan hangt von den Substituenten am 3-Acyl-l,2,4-oxadiazol ab108,109. 

The addition of amyl nitrate to a suspension of 2,4-diphenyl-5-nitro-soimidazole (37) in ether results in a mixture of 2,4-diphenyl-5-nitroim-idazole (38) and 3-benzoyl-5-phenyl-l, 2,4-oxadiazole (39), but a similar reaction using 4-phenyl-5-nitrosoimidazole gives only 3-benzoyl-1,2,4-oxadiazole (40) (60MI1). 

The kinetics for rearrangement of di-, tri-, tetra-, and penta-substituted (Z)-arylhy-drazones of 3-benzoyl-5-phenyl-l,2,4-oxadiazole to 2-aryl-4-benzoylamino-5-phenyl-... 

Similar behavior is shown by 3-acyl-l,2,4-oxadiazoles and their oximes. Thus 3-benzoyl-5-phenyl-l,2,4-oxadiazole is transformed by hydroxylamine into 3-benzamido-4-phenylfurazan, while the oximes of 3-aroyl- and 3-acetyl-5-methyl-1,2,4-oxadiazoles afford 3-aryl- and 3-methyl-4-aminofurazans in the presence of 6M hydrochloric acid. 

At pS+ > 3.8, compound 48 rearranged to 120. At lower pS+ it also underwent hydrolysis to 3-benzoyl-5-phenyl-l,2,4-oxadiazole and phenyl-hydrazine. 

The inability of ionic liquids to interact strongly with neutral nucleophilic species has been considered recently to be the main factor determining the high rate of rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-l,2,4-oxadiazole in ionic liquids in comparison to molecular solvents (Scheme 5.1-13) [42]. 

The paper of Frenna, Spinelli et al. contained data on the kinetics of the rearrangement of 3-benzoyl-5-phenyl-l,2,4-oxadiazole 129 into the corresponding 2-aryltriazoles 130 (Boulton-Katritzky reaction) [114]. 

D Anna F, Ferroni F, Frenna V, GuemelU S, Lanza CZ, Macaluso G, Pace V, Petrillo G, SpineUi D, Spisani R (2005) On the application of the extended Fujita-Nishioka equation to polysubstituted systems. A kinetic study of the rearrangement of several poly-substituted Z-arylhydrazones of 3-benzoyl-5-phenyl-l,2,4-oxadiazole into 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazoles in dioxane/water. Tetrahedron 61 167-178... 

A few examples, illustrating the principle of this type of degenerate rearrangement, are the thermo-induced equilibrium shift of 3-benzoylamino-5-methyl-l,2,4-oxadiazole into 3-acetylamino-5-phenyl-l,2,4-oxadiazole and the isomerization of 5-benzoyl-methylfuroxan oxime into 4-[a-nitroethyl]-3-phenylfurazan (82G181) (Scheme 1.8). They are extensively discussed in Chapter IV. 

Buscemi S, Pace A, Palumbo Picdonello A, Macaluso G, Vivona N, SpineUi D, Gioigi G (2005) Fluorinated heterocyclic compounds. An effective strategy for the synthesis of fluorinated Z-oximes of 3-perfluoroaIkyl-6-phenyl-2H-l,2,4-triazin-5-ones via a ring-enlargement reaction of 3-benzoyl-5-perfluoroaIkyl-l,2,4-oxadiazoles and hydrazine. J Org Chem 70 3288-3291... 

Beim Erhitzen von Malonsaure-amid-(2-benzoyl-hydrazonid)-nitril in Eisessig erfolgt Cyclisie-rung unter Ammoniak-Eliminierung zu 2-Aminocarbony 1-5-phenyl-1,3,4-oxadiazol (31% Schmp. 163 -168°) und 3-Cyan-5-phenyl-l,2,4-triazol4 14. ... 

The reaction of methylene triphenylarsorane with benzonitrile oxide in DMSO gave rise to 3,5-diphenylisoxazole (53) along with the 3-phenyl-4-benzoyl-2-isoxazoline oximes 54 and 55 ( /). When the reaction took place in ether instead of DMSO, a mixture of 3,5-diphenyl-l,2,4-oxadiazole (56) and 3,5-diphenylisoxazole (53) was obtained (31). 

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... 

The reaction of imidazole with benzonitrile oxide (in excess) gives little (Z)-l-benzoylimidazole oxime (70) besides (Z)-3-benzoyl-2,3-dihydro-l//-imidazol-2-one oxime (73) and benzonitrile (and in addition some side products). In the solid state only the chain form (70) is observed, but the formation of (72) indicates a chain-ring tautomerism in solution. The latter tautomer (71) is supposed to undergo nucleophilic addition to benzonitrile oxide. The resultant 7-benzoyl-3-phenyl-7, 7a-dihydroimidazo [4,5-a][l,2,4]oxadiazole (72) is considered the key intermediate suffering a [3 + 2]... 

Other non-traditional preparations of 1,2,3-triazoles have been reported. The rearrangement in dioxane/water of (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-27/-l,2,3-triazol-4-yl)ureas was investigated mechanistically in terms of substituents on different pathways <06JOC5616>. A general and efficient method for the preparation of 2,4-diary 1-1,2,3-triazoles 140 from a-hydroxyacetophenones 139 and arylhydrazines is reported <06SC2461>. 5-Alkylamino-] //-], 2,3-triazoles were obtained by base-mediated cleavage of cycloadducts of azides to cyclic ketene acetals <06S1943>. Oxidation of N-... 

Bei der Oximierung von 5-Amino-3-benzoyl-l,2,4-oxadiazol erhalt man 3-Phenyl-4-ureido-fu-razan110,111. 

DFT calculations have probed electronic effects in the reaction of 2-arylhydrazono acetic acid with pyruvic acid to give (2Z)- and (2 )-3-aryl acrylic acids. Rearrangement of 11 (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole to give 2-aryl-5-phenyl-(2//-triazol-4-yl)ureas has been studied in toluene, with catalysis by TEA or piperidine, and compared to earlier results in more polar media. The kinetics of the acetophenone-phenylhydrazine reaction has been studied for a variety of solvents and ketone ring substituents. ... 

The acid-catalysed rearrangement of benzyl phenolic ethers to diphenylmethane compounds and the rates of rearrangement of (Z)-aryUiydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-2H-l,2,3-triazol-4-yl)ureas have been reported. ... 

Mercapto-5-phenyl-l,3,4-oxadiazol Eine Losung von 1,25 g (5,5 mmol) Kalium-C-(2-benzoyl-hydrazi-no)-dithiocarbonat erhitzt man in 10 m/ DMF 15 min unter RiickfluB, wobei sich eine Festsubstanz ab-scheidet. Die Reaktionsmischung wird mit Wasser verdiinnt und mit verd. Salzsaure versetzt. Die so er-haltene Substanz kristallisiert man aus 50%igem Ethanol um Ausbeute 0,65 g (73%) Schmp. 219-220°. 

Benzoyl-hydrazin cyclisiert mit Kohlensaure-(chloracetyl-imid)-chlorid-phenylester zu 2-[Chloracetyl-ami-no -5-phenvl-l,3,4-oxadiazol (71 % Schmp. 201 -202°)232. das rationellcr durch Acylierung von 2-Amino-5-phenyl-1.3,4-oxadiazol synthetisierl werden kann (vgl. S.604). Diese Mcthode hat bislang keine allgemeine preparative Anwendung gefunden. 

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