799291-50-2Relevant articles and documents
Infrared irradiation: Effective promoter in the formation of N-benzylideneanilines in the absence of solvent
Vazquez, Miguel A.,Landa, Miguel,Reyes, Leonor,Miranda, Rene,Tamariz, Joaquin,Delgado, Francisco
, p. 2705 - 2718 (2007/10/03)
Infrared irradiation promoted the formation of a series of Schiff bases in the condensation reaction between benzaldehydes and anilines, in the absence of solvent. Benzaldehydes and anilines, containing either electron-withdrawing or electron-releasing groups, were assessed to identify any substituent effect on the formation of the Schiff bases. This methodology is characterized by ease of set-up and work-up, and the reaction yields were comparable with those obtained in the methods reported previously. Moreover, this new procedure is environmentally benign because no solvent was employed in the transformations.
Modeling substituent-dependence of the twist and shielding in a series of 4-substituted N-(4-nitrobenzylidene)anilines
Proks, Vladimir,Holik, Miroslav
, p. 1566 - 1576 (2007/10/03)
A series of 15 4-substituted N-(4-nitrobenzylidene)anilines was synthesized and studied by 1H NMR spectroscopy. Their ab initio calculated geometries and the shielding as expressed by aromatic ring currents were used in correlation analysis. The geometries were fully optimized using density functional theory B3LYP/6-311G** approaches. For the determination of the ring current contribution to the shielding of azomethine hydrogens H α was used direct ab initio calculation of the chemical shielding in a model system. Experimental chemical shift values free of these contributions were successfully correlated with increments ap of chemical shift for monosubstituted benzenes. In the same manner, the contribution of the anisotropy of C=N double bond to Hm hydrogen were calculated and values of the Hm chemical shift free of this contribution were successfully correlated with increments of chemical shift am.
Mechanism of Thermal Z/E Isomerization of Substituted N-Benzylideneanilines. Nature of the Activated Complex with an sp-Hybridized Nitrogen Atom
Asano, Tsutomu,Furuta, Hiroyuki,Hofmann, Hans-Joerg,Cimiraglia, Renzo,Tsuno, Yuho,Fujio, Mizue
, p. 4418 - 4423 (2007/10/02)
In order to study the mechanism of thermal geometrical isomerization involving a sp2-hybridized nitrogen atom, kinetic effects of substituent, solvent, and pressure were studied in substituted N-benzylideneanilines.The effect of the substituent on the aniline moiety was almost independent of the electronic nature of the benzylidene group, and the results could be described satisfactorily by log (k/k0) = ρ0 + r+(?+ - ?0) + r-(?- - ?0)>, except for the 4-(dimethylamino) group.The r- values were more than twice as large as r0, suggesting strongly that the aniline ring is in conjugation not with the carbon-nitrogen ? bond but with the nitrogen lone pair in the transition state.The lower activation enthalpies and fairly large negative activation entropies observed in N-(4-X-benzylidene)-4-nitroanilines also support this view.When a dimethylamino group exists in the 4-position of the aniline ring, the rate constants observed were larger than that expected from the above equation.This deviation suggests the existence of a reaction route where the two phenyl groups become coplanar in the transition state.Ab initio calculations on selected N-phenylformaldimines and N- benzylideneanilines were performed to characterize the actual relation between both reaction possibilities as alternative and parallel routes, respectively.On the basis of the experimental data, the rate constants for the two inversion isomerizations were estimated by assuming parallel reactions for three cases.
