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The acid hydrolysis of a series of 5-aryl-3-(β-thiomorpholinoethyl)-1,2,4-oxadiazoles gave substituted benzoic acids and 2-amino-8-thia-1-aza-5-azoniaspiro[4.5]dec-1-ene chloride hydrate, whose structure was demonstrated by spectral methods and X-ray diffraction structural analysis. [ABSTRACT FROM AUTHOR]

Fatty acid hydrazides of undec-10-enoic, ( Z)-octadec-9-enoic, ( Z)-12-hydroxyoctadec-9-enoic and ( Z)-9-hydroxyoctadec-12-enoic acids are used as cheap starting materials in the synthesis of important biologically active 5-(alkenyl)-2-amino-1,3,4-oxadiazole and 2-(alkenyl)-5-phenyl-1,3,4-oxadiazole using cyanogen bromide and benzoyl chloride or benzoic acid as reagents, respectively. The structure of these compounds was confirmed by IR, 1H NMR, 13C NMR and Mass spectra. All the newly synthesized compounds were screened for their antibacterial activity. Compounds 2c, 2d, 3a, 3c and 3d showed good antimicrobial activity against E. coli where as compounds 2a and 2d were found active against all the bacteria. [ABSTRACT FROM AUTHOR]

Monosubstituted oxadiazoles were synthesized by the reaction of hydrazides with triethyl orthoformate. Their reactions with benzoyl chloride gave benzoylcarbohydrazides, which under the action of thionyl chloride were cyclized to the respective 2,5-disubstituted oxadiazoles. 1-Aryl-4-(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)-pyrrolidin-2-ones were synthesized from acid hydrazides using carbon disulfide under basic conditions. [ABSTRACT FROM AUTHOR]

The reaction of 5-substituted mono-and polytetrazoles with heterocyclic acid chlorides and trifluoroacetic acid anhydride gave branched polynuclear 1,3,4-oxadiazole systems. [ABSTRACT FROM AUTHOR]

Condensation of 3-[(3-hydrazino-3-oxopropyl)anilino]-and 3-[(3-hydrazino-3-oxopropyl)-4-methylanilino]propane hydrazides with 2,4-pentanedione, phenyl isocyanate or phenyl isothiocyanate (with subsequent work up of the semicarbazides obtained by base), and carbon disulfide gave respectively: 1-(3,5-dimethyl-1H-1-pyrazolyl)-3-[3-(3,5-dimethyl-1H-1-pyrazolyl)-3-oxopropylanilino]-1-propanone, 3-(2-{[2-(5-oxo-4-phenyl-4,5-dihydro-1H-1,2,4-triazol-3-yl)ethyl]anilino}ethyl)-4-phenyl-4,5-dihydro-1H-1,2,4-triazol-5-one and its thio analog, and 5-(2-{[2-(2-thioxo-2,3-dihydro-1,3,4-oxadiazol-5-yl)ethyl]anilino}ethyl)-2,3-dihydro-1,3,4-oxadiazole-2(3H)-thione plus their methyl derivatives. [ABSTRACT FROM AUTHOR]

An efficient, rapid, microwave-accelerated one-step synthesis of some 5-aryl-2-(2-hydroxy-phenyl)-1,3,4-oxadiazoles by reaction of salicylic hydrazide with carboxylic acids in the presence of thionyl chloride under neat conditions is described. [ABSTRACT FROM AUTHOR]

We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH2Ph, t-Bu, CH2Cl, CCl3, CF3) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pKBH + is −1.8 to −5.2). The values of pKBH + determined on the H0 and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring. [ABSTRACT FROM AUTHOR]

A theoretical analysis has been carried out of the competing cyclization reactions of 1,2,4-triazahexa-1,3,5-triene and 1,2,4-oxadiazahexa-1,3,5-triene systems using as example C-(arylazo)imines and C-nitrosoimines containing aromatic or aliphatic substituents on the amine nitrogen atom, and also their benzoannelated derivatives. [ABSTRACT FROM AUTHOR]

The infrared absorption spectra of 2-[4-( N -dodecanoylamino)phenyl]-5-(4-nitrophenyl)-1,3,4-oxadiazole (also denoted AF51) in solution and in the solid state as well as the solid-state Raman spectrum of the powdered compound are compared with the infrared linear dichroic (LD) spectra recorded at two orthogonal polarizations. The IR-LD spectra were measured in an anisotropic solvent—the nematic liquid crystal ZLI-1695 (Merck). The solvent spectrum taken under precisely the same experimental conditions and polarized radiation azimuths was subtracted from the polarized sample spectra in order to achieve pure oriented spectra of the compound studied. These spectra were further processed using a stepwise reduction procedure that allows for assignment of vibrational modes having mutually orthogonal dipole moments. [ABSTRACT FROM AUTHOR]

It has been shown that dimethylamino-substituted 2,5-diaryloxazoles and 2,5-diaryl-1,3,4-oxadiazoles undergo heterocyclization under Vilsmeier-Haack conditions with the participation of the dimethylamino group to form quinazolinium salts. The oxazole ring can also be formylated at the free 4 position. In alkaline medium the quinazolinium ring is readily hydrolyzed with desalkylation. [ABSTRACT FROM AUTHOR]

A search has been made for the conditions of heterocyclization of O-aroyl-β-morpholinopropioamide oximes to 5-aryl-3- (β-morpholino) ethyl-1, 2, 4-oxadiazoles. We have investigated the heating of the starting compounds above their melting point, at their melting point, and holding in polar solvents (DMSO and DMF). Heating the 0-aroylamide oxime hydrochlorides in DMF appeared optimal. [ABSTRACT FROM AUTHOR]

The corresponding derivatives of 1,3,4-oxadiazoles have been synthesized by the reaction of monohydrazides of 2-aryl-4-methyl-4-cyclohexen-1,1-dicarboxylic acids with triethyl orthoformate or triethyl orthoacetate. [ABSTRACT FROM AUTHOR]