The Ring-opening Addition Reactions of Exo-imino Cyclic Compounds with Carboxylic Acids

The rate constants, the activation energies and the entropies of the activation of the ring-opening addition reactions of exo-imino cyclic compounds, such as ethylene N-phenyliminocarbonate, 2-phenylimino-3-methyloxazolidine and N-substituted 2-iminotetrahydrofurans, with carboxylic acids in various solvents have been determined in order to study the mechanism of these reactions. The rate of the reactions increases as the acidity of carboxylic acids increases, and the linear Hammett relation is observed in the reactions of ethylene N-phenyliminocarbonate or 2-phenylimino-3-methyloxazolidine with meta- and para-substituted benzoic acids. The relative rate of the reactions of the three exo-imino cyclic compounds, ethylene N-phenyliminocarbonate, 2-phenylimino-3-methyloxazolidine and 2-phenyliminotetrahydro-furan, with carboxylic acids is as follows: (Remark: Graphics omitted.) These results show that the ring-opening addition reaction involves two stages, namely, the initial formation of the intermediate salt from the exo-imino cyclic compound with carboxylic acid, followed by the reaction of the salt with the other acid to give the ring-opening addition compound.