Search results for "Diazole"
showing 10 items of 263 documents
A new palladium(II)-catalyzed [3,3] aza-Claisen rearrangement of 3-allyloxy-5-aryl-1,2,4-oxadiazoles
2011
Abstract A new efficient palladium(II)-catalyzed [3,3] aza-Claisen, formal sigmatropic rearrangement of 3-allyloxy-5-aryl-1,2,4-oxadiazoles was developed. The mechanism was studied by analyzing the regiochemical and stereochemical course of the reaction. The results obtained indicated the intervention of a cationic pallada-cycle similar to the one postulated for the Cope rearrangement of 1,5-dienes.
Isomerization and rearrangement of (E)- and (Z)-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole: evidence for a “new” type of acid-catalysis …
2008
A kinetic investigation in methanol of the title reaction has evidenced the occurrence of two processes: the 1-E1-Z isomerization and the rearrangement of the (Z)-isomer into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (1-Z T). The latter reaction is in line with the ability of the (Z)-phenylhydrazones of 3-benzoyl-1,2,4-oxadiazoles to undergo the so called mononuclear rearrangement of heterocycles (MRH). The occurrence of both the examined reactions is dependent on a Lewis-acid-catalysis. The obtained results have shown the possibility of a ‘new’ type of acid-catalysis (bifunctional catalysis by Lewis salts) in the MRH. This catalysis operates through a completely different me…
A deep insight into the mechanism of the acid-catalyzed rearrangement of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole in a non-polar s…
2010
The conversion of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole (1a) into the relevant 1,2,3-triazole (2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids (HAAs, 3a–h). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (kIII/kII) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAAs (3a–h) with 4-nitroaniline (4) in toluene. …
Synthesis and preliminary antibacterial evaluation of Linezolid-like 1,2,4-oxadiazole derivatives
2012
In the present study the synthesis of new Linezolid-like molecules has been achieved by substitution of the oxazolidinone central heterocyclic moiety with a 1,2,4-oxadiazole ring. Two series of 1,2,4-oxadiazoles, bearing different side-chains and containing a varying number of fluorine atoms, were synthesized and preliminarily tested for biological activity against some Gram-positive and Gram-negative bacteria using Linezolid and Ceftriaxone as reference drugs
A new tetranuclear copper(I) complex based on allyl(5-phenyl-1,3,4-thiadiazol-2-yl)azanide ligand: Synthesis and structural characterization
2015
Abstract By means of alternating current electrochemical technique a new tetranuclear crystalline copper(I) complex [Cu I 4 ( L − ) 4 ] ( L − – allyl(5-phenyl-1,3,4-thiadiazol-2-yl)azanide ion) has been obtained and characterized by X-ray single crystal diffraction ( Sp. gr. I 4 1 / a ) and Raman spectroscopy. The metal center adopts linear arrangement, composed of one thiadiazole N atom from the one L − anion and one azanide N atom of the other L − ligand. A bridged Cu atoms stitch four L − ligands into the firstly observed tetranuclear copper(I) azanide complex with intramolecular Cu(I)⋯Cu(I) interactions at the distance of 2.7451(6) A. Molecular structure and Raman spectrum of the compo…
Mononuclear rearrangement of heterocycles in zwitterionic micelles of amine oxide surfactants.
2012
Abstract Rate constants for the mononuclear rearrangement (MRH) of Z -phenylhydrazones of some 5-substituted-3-benzoyl-1,2,4-oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N -tetradecyl- N , N -dimethylamineoxide (C 14 DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudo-phase model and compared with those obtained in non-ionic micelles (Triton X-100). Evidence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement…
On the application of the extended Fujita-Nishioka equation to polysubstitued system. A kinetic study of the rearrangement of several poly-substitued…
2005
Abstract The rearrangement rates of several di-, tri-, tetra- or penta-substituted Z -arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole ( 1a – 18a ) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazoles ( 1b – 18b ) have been determined in 1:1 (v:v) dioxane/water in a wide range of p S + (3.80–12.50) at different temperatures. The kinetic data obtained have been correlated with those previously collected for the rearrangement of ortho -, meta - and para -substituted Z -arylhydrazones ( 19a – 38a ) by means of an extension of the linear free-energy relationship (LFER) proposed by Fujita and Nishioka, thus considering steric ( E s ) and field ( F o ) proximity effects in additi…
Acid- and Base-Catalysis in the Mononuclear Rearrangement of Some (Z)-arylhydrazones of 5-Amino-3-benzoyl-1,2,4-oxadiazole in Toluene: Effect of Subs…
2011
The reaction rates for the rearrangement of eleven (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole 3a-k into the relevant (2-aryl-5-phenyl-2H-1, 2,3-triazol-4-yl)ureas 4a-k in the presence of trichloroacetic acid or of piperidine have been determined in toluene at 313.1 K. The results have been related to the effect of the aryl substituent by using Hammett and/or Ingold-Yukawa-Tsuno correlations and have been compared with those previously collected in a protic polar solvent (dioxane/water) as well as with those on the analogous rearrangement of the corresponding (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole 1a-k in benzene. Some light can thus be shed on the general di…
Chemistry of Fluorinated Oxadiazoles and Thiadiazoles
2014
A literature survey of the chemistry of fluorinated oxadiazoles and thiadiazoles is presented. The core part on synthetic procedures is given by type of heterocycle and includes recent developments up to the end of 2012. Reactivity is discussed when induced by the presence of the fluorinated moiety. Selected examples of bioactive compounds and applications are illustrated.
Multiple 1,2,3-thiadiazoles
1997
A series of compounds 3a-d,i-n with two or three 1,2,3-thiadiazole rings, useful for photocrosslinking processes, was prepared from the di- or triketones 1a-d,i-n via the corresponding hydrazones 2a-d,i-n by applying the Hurd-Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g, was elaborated for the olefinic system 3h.