1.3.4- Oxadiazole-2-acetic acid, 5-phenyl

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). 

Chloramine-T reacts with (2-oxo-3-phenyl-27/-[l,8]naphthyridine-l-yl)acetic acid arylidenehydrazides to generate 1-(5-aryl-[1,3,4]-oxadiazol-2-ylmethyl)-3-phenyl-17/-[l,8]naphthyridin-2-ones <2004IJB2014>. 

Benzylic halogenation isafeatureof2-diphenylmethyl-l,3,4-oxadiazole and the ethyl ester of 5-phenyl-l,3,4-oxadiazolyl-2-acetic acid [67AC(P)169]. 

Z)-(2-Aminothiazol-4-yl)methoxyimino acetic acid Bis-(2-oxo-oxazolidinyl)phosphinic chloride 2-Mercapto-5-phenyl-l,3,4-oxadiazole... 

Treatment of 1-cyanoformamidinebenzhydrazide (11) with boiling acetic acid produces 2-phenyl-l,3,4-oxadiazole-5-carboxamide (12) with elimination of NH3 and partial hydrolysis of the CN group, together with 3-cyano-5-phenyl-1,2,4-triazole (13).51 The thermal... 

Dehydrative cyclization of 3-(5-carboxy)-5-phenyl-4-(pyrrol-l-yI)l,2,4-triazole (508) with poly phosphoric acid gave (82G345) the 1,2,4-triazolo[3,4-/7]l,3,4-thiadiazine (509). Ring transformation of 1,3,4-oxadiazoles to 7//-l,2,4-triazolo[3,4-/>]l,3,4-thiadiazines (507) was reported by Sasaki et al. (82JOC2757) through the reaction of [(1,3,4-oxadiazol-2-yl)thio]ketones (123) with hydrazine hydrate in the presence of acetic acid. 

Anodic addition of an oxygen function to a C = N or C = C double bond may be exemplified by the oxidative cyclization of aryl semicarbazones to 1,3,4-oxadiazoles in acetonitrile-acetic acid containing H2SO4 or, under strictly anhydrous conditions (in the presence of acetic anhydride), to triazolinones [40]. Other examples are the anodic oxidation of benzaldehyde-2-hydroxyanil to 2-phenyl-1,3-benzoxazole derivatives [41] and the indirect oxidation of 2-hydroxychalcones to flavonoids using tris(4-bromophenyl)amine in MeOH-CH2Cl2 as mediator [42] ... 

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. ... 

N-(s-Triazoi-4-yl)phenylacetamidine refluxed 12 hrs. with an equimolar amount of ethyl chloroformate in dry nitromethane or acetonitrile 3-phenyl-l,2,4-triazole. Y 91%. - Other acylating agents sudi as acetic anhydride, carboxylic acids, or HCl may be used in place of ethyl diloroformate. F. e. s. H. G. O. Becker et al., J. pr. 311, 471 (1969) synthesis of 1,3,4-oxadiazoles cf. ibid. 311, 646. 

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