Aromatic nucleophilic substitution reactions of oxime ethers with aliphatic primary and secondary amines in benzene

Abstract

Reactions of various oxime ethers with the primary alkylamines propyl-, butyl-, pentyl-, and hexylamine and with pyrrolidine, a secondary alkyl amine, have been studied in benzene at 35 ± 0.1 °C. These reactions have all been found to be wholly base catalysed. Some reactions, especially those involving strong nucleophiles and substrates with poor leaving groups, exhibit a third-order dependence on amine concentration which has been explained on the basis of a cyclic transition-state mechanism. These reactions also show an inverse-temperature effect. Reactions with substrates which have good leaving groups and with weaker nucleophiles show a second-order dependence on amine concentration. These reactions show normal temperature effects with a low energy of activation. This low energy of activation and high negative entropy of activation support the cyclic transition-state mechanism invoked to explain these data.