1.2.4- Oxadiazole, 5- -3-phenyl

N N 3-( p-Bromophenyl)-4-methyl- 1,2,5-oxadiazole 2-oxide 3-(p-bromo-phenyl)-4-methyl-l,2,5-oxadiazole 5-oxide 3,4-diphenyl-l,2,5-oxadiazole... 

Isoxazoles unsubstituted in the 3-position react with hydroxide or ethoxide ions to give )3-keto nitriles (243) -> (244). This reaction involves nucleophilic attack at the 3-CH group. 1,2-Benzisoxazoles unsubstituted in the 3-position similarly readily give salicylyl nitriles (67AHC(8)277), and 5-phenyl-l,3,4-oxadiazole (245) is rapidly converted in alkaline solution into benzoylcyanamide (246) (61CI(L)292). A similar cleavage is known for 3-unsubstituted pyrazoles and indazoles the latter yield o-cyanoanilines. 

Phenylisothiazole is nitrated predominantly in the meta position of the phenyl group, whereas 4-phenylisothiazole is nitrated ortho and para in the phenyl group <72AHC(14)1). Nitration of 3-phenyl-l,2,4-oxadiazole gives a mixture of m- and p-nitrophenyl derivatives <6301196). 

Methyl groups on C-linked phenyl attached to oxazoles, isoxazoles and oxadiazoles react with benzylidineaniline to give stilbene derivatives (Scheme 51) <78AHC(23)l7l). 

Oxadiazole, 5-ethyl-3-phenyl-dipole moment, 6, 379 (77JOC1555)... 

Oxadiazole, 2-amino-5-phenyl-mass spectra, 6, 429 methylation, 6, 431... 

Oxadiazole, 2-phenyl-melting point, 6, 430 molecular diagrams, 6, 428 reactions... 

I-Cyano-3-phenylurea, first obtained by the alkaline hydrolysis of 5-anilino-3- -toluyl-l,2,4-oxadiazole, has been prepared by tlic condensation of phenyl isocyanate and the sodium salt of cyanamide. However, in these publications an incorrect structural assignment for the product was made. 1-Cyano-3-phenyl-urea is obtained also, together with other products, by warming gently l-cyano-3-phenylthiourea with caustic soda in the presence of ethylene chlorohydrin, or by gradually adding caustic )otash to a boiling solution of 1-phenyldithiobiuret and ethylene clilorohydrin in ethanol. ... 

A mixture of 3-hydroxy-4-phenylfurazan and 1,2,4-oxadiazole 243 was prepared from a-phenyl-a-hydroximino hydroxamic acid by acylation and subsequent treatment with 15% aqueous NaOH (Scheme 164) (25G201). The reaction of tetraacetate 244 with sodium acetate hydrate in glacial acetic acid at 70°C gives 3,4-dihydroxyfurazan (9%) (92URP1752734). a-Hydroximino ester 245 reacts with hydroxylamine to form furazan 246 in 25% yield (Scheme 164) (79JHC689). 

The irradiation of 3-amino-5-phenyl-l,2,4-oxadiazole (98) gave the corresponding 1,3,4-oxadiazole (99) (Scheme 41) [88JCS(P1)1313 88JHC931 95FI(41)2095). The formation of 99 has been explained by assuming a RCRE mechanism. 

Fig. 21. Relative energy of the exeited states of 3-amino-5-phenyl-l,2,4-oxadiazole and of some reaetive intermediates.

Fig. 23. Relative energy of the excited states of 3,4-phenyl-1,2,5-oxadiazole and of some reactive intermediates.

Chemical Name N,N-dibutyl-N -(3-phenyl-1,2,4-oxadiazol-5-yl)-1,2-ethanediamine hydrochloride... 

Benzaldehyde and hydroxylamine may be reacted, the product chlorinated and then reacted with cyanamid to give 5-amino-3-phenyl-1,2,4-oxadiazole. 

Symmetrisch substituierte 1,3,4-Oxadiazole liefern dagegen die Tetrahydro-1,3,4-oxadiazole, wahrend 5(2)-Phenyl-2(5)-naphthyl-(2)-l,3-oxazole nur zu 5(2)-Phenyl-2(5)-naphthyl-( 1 )-2,3-dihydro-1,3-oxazolen reduziert werden1 ... 

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