16322-19-3Relevant academic research and scientific papers
The N-alkylation of 4-nitrobenzochalcogenadiazoles: Synthesis and theoretical approach
Salah, Saida B.,Zaier, Rania,Ayachi, Sahbi,Goumont, Régis,Boubaker, Taoufik
, p. 80 - 86 (2019/07/18)
A facile synthetic method for N-alkylated substituted benzochalcogenadiazoles is described. When treated with Meerwein salt, the 4-nitrobenzochalcogenadiazoles have undergone an N-alkylation to afford the expected salts as a mixture of two N1/N3 isomers in toluene. The regioselectivity of the alkylation reaction was then confirmed by spectroscopic data as well as theoretical calculations.
Reactions of substituted phenylnitromethane carbanions with aromatic nitro compounds in methanol: Carbanion reactivity, kinetic, and equilibrium studies
Asghar, Basim H.
, p. 477 - 488 (2014/07/08)
The feasibility of carrying out nucleophilic addition from electron-deficient heteroaromatics has been addressed through a detailed investigation of the interaction of a two 7-substituted-nitrobenzofurazan (R = OMe 2a; R = Cl 2b) with a series of substituted-nitroaryl anions (X = 4-NO 2 1a; X = 3-NO2 1b; X = 4-CN 1c; X = 4-Br 1d), all reactions first lead to the quantitative formation of the σ-adducts 3a-d and 4a-d arising from covalent addition of the nucleophile to the C-5 carbon. The rate and equilibrium constants for the formation of σ-adducts 3a-d and 4a-d (k5, K5) together with the rate constants for their decomposition (k-5) have been determined in methanol at 25C, allowing a determination of intrinsic rate constants, k0 = 0.03, the lower k0 value reflects the very strong salvation by methanol of the negative charge on the nitro group. The discovery of a linear correlation between the E and pKaMeOH parameters allows a calibration of the electrophilicity power of 2a and 2b, E = -11.67 and -10.29, respectively. Applying the general approach to nucleophilicity/electrophilicity recently developed by Mayr et al. through the relationship log k = s(E + N), a successful ranking of our nitroaryl anions 1a-d on the general nucleophilicity scale (N) has been carried out. The N values of 1a-d are found to cover a range from 15.78 to 16.69. The results are compared with previously reported data in water and DMSO.
Porphyrins with exocyclic rings. Part 20: Synthesis and spectroscopic characterization of porphyrins with fused 2,1,3-benzoxadiazole and 2,1,3-benzoselenadiazole moieties
Cillo, Catherine M.,Lash, Timothy D.
, p. 11615 - 11627 (2007/10/03)
Porphyrins with fused 2,1,3-benzoxadiazole and 2,1,3-benzoselenadiazole units were prepared by the '3+1' MacDonald-type methodology. 4-Nitro-2,1,3-benzoxadiazole, 6-chloro-4-nitro-2,1,3-benzoxadiazole and 4-nitro-2,1,3-benzoselenadiazole condensed with isocyanoacetates in the presence of the non-nucleophilic base DBU to give tricyclic pyrrole derivatives in excellent yields. Further cleavage of the ester moieties and decarboxylation afforded α-unsubstituted pyrroles and these were further condensed with 2 equiv of an acetoxymethylpyrrole tert-butyl ester to give crude preparations of tripyrranes. The tert-butyl ester protective groups were cleaved with TFA and following dilution with dichloromethane, '3+1' condensation with a pyrrole dialdehyde, and oxidation with ferric chloride, the heterocyclic ring fused porphyrins were obtained in moderate yields. The yields were lower than expected because of difficulties in preparing required tripyrranes due to the reduced reactivity of the pyrrolic intermediates. The UV-vis spectra of these new porphyrin systems were highly modified showing broadened split Soret bands. In addition, the nickel(II), copper(II) and zinc complexes gave unusual UV-vis spectra with weakened split Soret bands and strong Q-type absorptions above 600 nm. These modified structures show some potential for applications as photosensitizers in photodynamic therapy.
A new cyclization involving the diazonium and ortho-(tert-butyl)-NNO-azoxy groups - Synthesis of 1,2,3,4-benzotetrazine 1-oxides
Lipilin, Dmitry L.,Smirnov, Oleg Yu.,Churakov, Aleksandr M.,Strelenko, Yuri A.,Ioffe, Sema L.,Tartakovsky, Vladimir A.
, p. 3435 - 3446 (2007/10/03)
The synthesis of 1,2,3,4-benzotetrazine 1-oxides (BTOs) is described. Bromo-BTOs 4b-d were prepared by the intramolecular cyclization of diazonium salts bearing an ortho-(tert-butyl)-NNO-azoxy group. BTOs bearing electron-releasing substituents were obtained by nucleophilic displacements of bromine in 4b-d. The formation of the BTO cyclic system involves the intermediate 2-(tert-butyl)-1,2,3,4-benzotetrazinium 4-oxides, which arise from an N,N-[1,21-shift of the tert-butyl group. Decomposition of BTOs involves opening of the tetrazine ring to afford ortho-azidonitroso derivatives, followed by their cyclization with the evolution of the N2 molecule to give benzofurazans. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Kinetic and equilibrium studies of the reactions of 4-nitrobenzo-furazan and some derivatives with sulfite ions in water. Evidence for the Boulton-Katritzky rearrangement in a σ-adduct
Crampton, Michael R.,Pearce, Lyndsey M.,Rabbitt, Lynsey C.
, p. 257 - 261 (2007/10/03)
The reactions with sulfite ions in water of 4-nitrobenzofurazan, 1, 4-nitrobenzofuroxan, 2, and three 4-nitro-7-substituted benzofurazans have been examined by 1H NMR spectroscopy and stopped-flow spectrophotometry. For each substrate the initial reaction occurs at the 5-position to give σ-adducts which have considerably higher thermodynamic stability than the corresponding adduct of 1,3,5-trinitrobenzene. In the cases of 1 and 2 isomerisation of the 5-adducts occurs slowly to yield adducts carrying sulfite at the 7-position. 1H NMR measurements on 2 labelled with 15N provide evidence that here the rearrangement involves an intramolecular Boulton-Katritzky mechanism.
Thermal Stability Studies on a Homologous Series of Nitroarenes
Oxley, Jimmie C.,Smith, James L.,Ye, Hong,McKenney, Robert L.,Bolduc, Paul R.
, p. 9593 - 9602 (2007/10/02)
The thermal stabilities of a number of nitroarenes were examined in solution and in condensed phase.In general, increasing the number of nitro groups decreased thermal stability.Changing the substituent on 1-X-2,4,6-trinitrobenzene from X = H to NH2 to CH3 to OH accelerated decomposition; this effect was attributed to increased ease of intramolecular proton transfer to an ortho nitro group, thus weakening the carbon-nitrogen bond.In solution, the effect of increasing substitution from n = 1 to n = 3 on Xn(NO2)3C6H3-n was uniformly that of decreasing the thermal stability of the species.However, in condensed phase, results suggested that crystal habit may be more important than molecular structure; for X = Br, CH3, and NH2, the more substituted species was the more stable.
Synthesis of 4,6-Dinitrobenzofurazan, a New Electron-Deficient Aromatic
Read, Roger W.,Spear, Robert J.,Norris, William P.
, p. 1227 - 1237 (2007/10/02)
Preparation of 4,6-dinitrobenzofurazan (6) has been investigated by a number of routes.Its synthesis from 4,6-dinitrobenzofuroxan (4,6-dinitrobenzofurazan 1-oxide) (1) by reduction with triphenylphosphine proceeds in similar overall yield to the known method of nitration of 5-nitrobenzofurazan (8) but in fewer steps.Nitration of 4-nitrobenzofurazan (7) was studied as an alternative route, and the difference in reactivity between (7) and (8) is discussed.The benzofurazan (6) readily forms hydroxy and methoxy Meisenheimer complexes which have been isolated as stable, but highly explosive, potassium salts.
Concurrent Methoxide Ion Attack at the 5- and 7-Carbons of 4-Nitrobenzofurazan and 4-Nitrobenzofuroxan. A Kinetic Study in Methanol
Terrier, Francois,Chatrousse, Alain-Pierre,Millot, Francois
, p. 2666 - 2672 (2007/10/02)
In methanolic solution,methoxide ions attack both the 5- and 7-carbons of 4-nitrobenzofurazan (5) and 4-nitrobenzofuroxan (8) to give the Meisenheimer-type complexes 6, 9 and 7, 10.The kinetics of the interactions have been studied by the stopped-flow method.The formation of the 5-methoxyl adducts 6 and 9 is found to always precede that of the thermodynamically more stable 7-methoxyl isomers 7 and 10.The results indicate that the para-like 4-nitro group is more efficient than the furazan and the furoxan rings in delocalizing the negative charge in 7 and 10.The kinetic and thermodynamic parameters Δ H0, Δ S0, Δ H(excit.), and Δ S(excit.) or the various reactions have been determined.It appears that only a large positive entropy change, Δ S0 (about +80 J/mol*K), is responsible for both the formation and the greater stability of the 7-methoxyl complexes 7 and 10 as compared to that of their 5-methoxyl analogues.Stabilization of 7 and 10 by association of the 4-nitro group with the potassium counterion is suggested.
