Novel catalytic effects in ester aminolysis in chlorobenzene

Abstract

The mechanism of glyme catalyzed ester aminolysis in chlorobenzene should be modified by including a new reaction pathway that shows a first-order dependence on the concentration of the phase transfer catalyst and a second-order dependence on butylamine.

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…They further concluded that the number of polyether oxygens required for optimum catalysis and the best spacing (in α,ω-dimethoxyalkanes) among these oxygens are strongly dependent on the number of ammonium protons in the transition structure. More recently, Basilio et al 312, 313 studied the butylaminolysis of p -nitrophenyl acetate in chlorobenzene catalyzed by crown ethers or glymes as phase-transfer catalysts, and proposed a reaction pathway to reflect a 1 st -order dependence on the catalyst concentration and a 2 nd -order dependence on butylamine concentration (Scheme 40). The new pathway (red arrows) involves the complexing of ether-TI (ether-tetrahedral intermediate) with an amine molecule, which is an addition to the mechanisms (green and blue arrows) traditionally accepted for the catalysis by phase-transfer agents of aminolysis reactions in aprotic solvents.…”

A New Reaction Pathway in the Ester Aminolysis Catalyzed by Glymes and Crown Ethers

“…As we have shown previously, 25 the mechanism presented in Scheme 1 needs to be further developed in order to explain the observed kinetic data. The presence of a kinetic term showing a second-order dependence on butylamine concentration and a first-order dependence on glyme concentration may be accounted for by the possibility that the C‚T ( complex may decompose by a base-catalyzed pathway.…”

Molecular recognition-based catalysis in nucleophilic aromatic substitution: a mechanistic study

“…In this case, glymes and crown ethers act as base catalysts through a specific host-guest interaction with the ammonium moiety of the reaction intermediate. [5][6][7][8][9][10][11][12][13][14] In order to achieve a better understanding of these molecular-recognition processes, the exploration of alternative reactions involving zwitterionic intermediates appears to be the next logical step. For this purpose, the nucleophilic aromatic substitution (S N Ar) by n-butylamine for two different and representative nitroarenes has been studied in the presence of glymes and crown ethers.…”