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Reactions of Nitroheteroarenes with Carbanions: Bridging Aromatic, Heteroaromatic, and Vinylic Electrophilicity
Author(s) -
Seeliger Florian,
Błażej Sylwia,
Bernhardt Sebastian,
Mąkosza Mieczysław,
Mayr Herbert
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800329
Subject(s) - electrophile , nitrobenzene , chemistry , carbanion , nucleophile , electrophilic substitution , reaction rate constant , medicinal chemistry , computational chemistry , sulfone , substitution reaction , sn2 reaction , nucleophilic substitution , organic chemistry , kinetics , catalysis , physics , quantum mechanics
The relative rate constants for the vicarious nucleophilic substitution (VNS) of the anion of chloromethyl phenyl sulfone ( 1 − ) with a variety of nitroheteroarenes, for example, nitropyridines, nitropyrroles, nitroimidazoles, 2‐nitrothiophene, and 4‐nitropyrazole, have been determined by competition experiments. It was shown that nitropyridines are approximately four orders of magnitude more reactive than nitrobenzene. Among the five‐membered heterocycles 2‐nitrothiophene is the most active followed by nitroimidazoles and 4‐nitropyrazole. Nitropyrroles are the least electrophilic nitroheteroarenes with reactivities comparable to nitrobenzene. Quantum chemically calculated methyl anion affinities (B3LYP/6–311G(d,p)//B3LYP/6–31G(d)) of the nitroarenes correlated only moderately with the partial relative rate constants. The correlation of these activities with the LUMO energies of nitroarenes is even worse. By measuring the second‐order rate constants of the addition of 1 − to nitroarenes and to diethyl arylidenemalonates 10 , it was possible to link the electrophilic reactivities of nitroheteroarenes with the comprehensive electrophilicity scale based on the linear‐free‐energy‐relationship log k (20 °C)= s ( N + E ).