Gabriella Macaluso

Heterocyclic photorearrangements ― Photochemical behaviour of some 3-acetylamino-5-aryl-1,2,4-oxadiazoles: a photoinduced iso-heterocyclic rearrangement

La photoreaction a lieu a 254 nm dans le methanol. On obtient des acetamido-2 alkyl-7 quinazolones-4

Rearrangement of 3-(N-Heteroarylamino)-1,2,5-oxadiazoles: Triazolo[1,5-a]quinolines and Triazolo[1,5-a]pyridines

The rearrangement reaction of 1,2,5-oxadiazole derivatives bearing quinoline and pyridine heterocycles in a N-C-N side chain sequence was investigated. Triazolo[1,5-a]quinoline and triazolo[1,5-a]pyridine oximes were obtained in good yield

Mononuclear heterocyclic rearrangements. Part 14. Rearrangement of some Z-arylhydrazones of 3-benzoyl-5-phenylisoxazole to 2-aryl-4-phenacyl-1,2,3-triazoles in dioxane–water

The kinetics of the title reaction have been measured at various pS+ values. The results show the occurrence of general base catalysis and furnish information about substituent effects on the studied reaction. A reaction mechanism analogous to that proposed for the rearrangement of the arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole is suggested. The reactivity of isoxazole derivatives is much lower than that of 1,2,4-oxadiazole derivatives.

Mononuclear heterocyclic rearrangements. Effect of the structure of the side chain on the reactivity. Part 3. Rearrangement of some N-(5-phenyl-1,2,4-oxadiazol-3-yl)-N′-arylformamidines into 1-aryl-3-benzoylamino-1,2,4-triazoles in acetonitrile in the presence of triethylamine

The apparent pseudo-first-order rate constants for the title reaction give a curvilinear plot versus tertiary amine concentration, according to the equation kA  (ku, + K1k2[TEA])/(1 + K1[TEA]). This shows the occurrence of two different reaction pathways; the one, independent of [TEA] and the other, dependent on [TEA], which involves a fast conversion of the substrate into an acid-base adduct or an ion pair followed by its slow conversion into the corresponding triazole. The substituent effects on these reactions have also been studied.

Mononuclear heterocyclic rearrangements. Part 16. Kinetic study of the rearrangement of some ortho-substituted Z-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazoles in dioxane-water and in benzene

Abstract The effects of six ortho -substituents (Me, Et, F, Cl, Br and NO 2 ), showing different electronic and proximity effects, on the rate of the title reaction have been studied at 313.15 K in dioxane/water at various p S + values (3.8–12.7) and in benzene at various piperidine concentrations. The kinetic data obtained have been treated by using a Fujita-Nishioka approach with a dissection of the ortho -substituent effect in ‘ordinary polar effect’, ‘proximity polar effect’ and ‘primary steric effect’. The different contributions calculated have been discussed in the framework of the various mechanisms proposed for the studied rearrangement.

A synthesis of 1,2,4-triazolo-[1,5-f]phenanthridines by rearrangements of 1,2,5-oxadiazoles involving an NCN sequence with the imine nitrogen in an aromatic heterocyclic ring

A synthetic pathway to 1,2,4-triazolo[1,5-f]phenanthridine system by a base catalyzed rearrangement of 3-(6-phenanthridine)amino-1,2,5-oxadiazoles (5a,b) has been investigated. This ring transformation is the first example of the applicability of the mononuclear heterocyclic rearrangement involving an NCN sequence to the synthesis of bridged nitrogen systems

Aromatic nucleophilic substitution reactions of some 3-nitro-2- p -nitro-phenoxy-5-X-thiophenes with substituted anilines in methanol

A series of optimised ‘thiophene’ sigma constant values has been calculated by using the reactions of some 3-nitro-2-p-nitrophenoxy-5-X-thiophenes with some substituted anilines. The susceptibility constants obtained are discussed in the framework of the reactivity–selectivity principle.

Rarrangements of N-ureidopyrroles : a case of mononuclear heterocyclic rearrangement involving an aromatic heterocycle as carbon-nitrogen-nitrogen sequence

The rearrangement, under basic conditions, of the N-ureidopyrroles (8) directly led to the pyrrolylalkenes (14). The reaction was explained in terms of initial mononuclear heterocyclic rearrangement leading to the pyrrolo[1,2-c] [1,2,3]-triazoles (12) followed by their decomposition to the final products under the reaction conditions. Attempts to thermally rearrange compound (8b) only gave products of decomposition of the ureido moiety

Mononuclear heterocyclic rearrangements. Part 10. Rearrangements in the 1,2,5-oxadiazole series

By studying the chemical behaviour of N-(4-methyl-1,2,5-oxadiazol-3-yl)-N′-phenylurea and of N-(4-methyl- or phenyl-1,2,5-oxadiazol-3-yl)-N′-arylformamidines in mononuclear heterocyclic rearrangements and comparing these results with those already obtained in the 1,2,4-oxadiazole and isoxazole series, relative tendencies towards mononuclear heterocyclic rearrangement have been estimated; viz. 1,2,4-oxadiazole > isoxazole > 1,2,5-oxadiazole.

Apolar versus Polar Solvents: A Comparison of the Strength of Some Organic Acids against Different Bases in Toluene and in Water

The constants of ion-pair formation with 3-nitroaniline (3NO(2)A) for eight halogenoacetic acids (HAAs, 3a-h: TFA, TCA, TBA, DFA, DCA, DBA, MCA, and MBA), and five 2,2-dichloroalkanoic acids containing 3-8 carbon atoms (HAs, 5a-e: DCPA, DCBA, DCMBA, DCVA, and DCOA) have been determined in TOL at 298.1 K. The results obtained brought to evidence for HAAs the formation of ion-pairs with two different stoichiometries (base-acid, 1:1 or 1:2), while in contrast the HAs furnish only the 1:1 pairs. The different steric and electronic requirements of HAAs and HAs seem to be responsible for such an unlikely behavior. At the same time, the acid-catalyzed MRH of the (Z)-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole (1) into (2,5-diphenyl-2H-1,2,3-triazol-4-yl)urea (2) in the presence of the five HAs above has been investigated in TOL at 313.1 K. Thus, in contrast with previous results in the presence of several HAAs, a unique pathway for the rearrangement has been observed, again pointing out the importance of the above effects on the initial acid/base interactions. Finally the acidic strength of TFA against seven nitroanilines (NA, 4a-g: 4NO(2)A, 3NO(2)A, 3Me4NO(2)A, 4Me3NO(2)A, 2Me3NO(2)A, 2NO(2)A, and 3,5diNO(2)A) characterized by a very different basicity has been measured in TOL at 298.1 K.