Meisenheimer complexes as hidden intermediates in the aza-S_NAr mechanism

Abstract

In this work we report a computational study about the aza-SNAr mechanism in fluorine- and chlorine-containing azines with the aim to unravel the physical factors that determine the reactivity patterns in these heterocycles towards propylamine.

Poly(aryl cyanurate)-Based Thin-Film Composite Nanofiltration Membranes

“…In general, the anionic adduct formed when a nucleophile attacks an arene bearing electron-withdrawing groups is known as a Meisenheimer complex. 31 , 32 These adducts, resulting from nucleophilic aromatic substitution reactions, may be reactive intermediates but in some cases have also been isolated. 33 As the leaving group departs, aromaticity of the triazine is restored.…”

“…The electron-deficient carbon atoms of the triazine ring allow for nucleophilic attack by OH – . , The intermediate generally postulated to result from nucleophilic attack at these nitrogen-containing heterocycles features a negative charge that is delocalized over the three nitrogen atoms of the triazine ring. In general, the anionic adduct formed when a nucleophile attacks an arene bearing electron-withdrawing groups is known as a Meisenheimer complex. , These adducts, resulting from nucleophilic aromatic substitution reactions, may be reactive intermediates but in some cases have also been isolated . As the leaving group departs, aromaticity of the triazine is restored.…”

Photoredox Catalyzed Dealkylative Aromatic Halogen Substitution with Tertiary Amines

“…To support the hypothesis of the formation of species A , the free energies of the interaction of aryl radicals with trimethylamine were derived by means of quantum chemical calculations. Energies were calculated at M06-2X/6-31+G(d) [ 35 ], and for the stationary points, energies were calculated by CPCM method in DMSO solution ( Figure 1 ). In case of perfluorinated pyridinyl and benzoxazolyl radicals, in the resulting complexes A1 and A2 , the amine nitrogen is located out of plane of the heteroaromatic ring having relatively long C,N bond of 1.595 Å and 1.559 Å, respectively.…”

How Do Aromatic Nitro Compounds React with Nucleophiles? Theoretical Description Using Aromaticity, Nucleophilicity and Electrophilicity Indices

“…However, even in recent publications on the mechanism of S N Ar reactions this situation was not taken into account [ 3 , 34 ]. Moreover, in all quantum chemical calculations of the energy profiles of the addition of nucleophiles to halonitrobenzenes only the addition at positions occupied by halogens has been considered [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 34 ]. It is really surprising, because calculations of a reaction between two reactants should look for the pathways that proceed via transition states (TS) of the lowest free energies, thus they have ignored faster addition at positions occupied by hydrogen.…”

“…The model nucleophile (chloromethyl phenyl sulfone anion) has been chosen as an example, which, due to its nature, is much less affected by the solvent's effects contrary to the other most common protic or polar nucleophiles [35]. However, even in recent publications on the mechanism of S N Ar reactions this situation was not taken into account [3,34]. Moreover, in all quantum chemical calculations of the energy profiles of the addition of nucleophiles to halonitrobenzenes only the addition at positions occupied by halogens has been considered [7][8][9][10][11][12][13][14][15][16][17][18]34].…”