Studies on Seven-membered Ring Compounds. XVIII. Reactions of the Quaternary Ammonium Salts of Cycloheptimidazole Derivatives

Abstract

The quaternary ammonium salt 1-alkylcycloheptimidazol-2(1H)-one afforded1-alkylamino-7-alkyliminocycloheptatriene on heating with alkali. However, treatment of this salt with dilute aqueous sodium hydroxide at room temperature gave a ditropyl ether derivative. Action of active methylene compounds on the ammonium salt in the presence of sodium ethoxide yielded 6-substituted derivatives, which were easily dehydrogenated to the corresponding heptafulvene derivatives. As an example, the reaction of 2-oxo-1, 3-dibenzyl-1, 2-dihydrocycloheptimidazolinium chloride with ethyl cyanoacetate afforded 6-[cyano(ethoxycarbonyl)methyl]-1, 3-dibenzyl-3, 6-dihydrocycloheptimidazol-2(1H)-one, which was dehydrogenated to 6-[cyano(ethoxycarbonyl)methylene]-1, 3-dibenzyl-3, 6-dihydrocycloheptimidazol-2(1H)-one on heating with ethanol. This reaction made it clear that the quaternary ammonium salt has tropylium ion structure. Such reaction occurred also I case of 2-phenylcycloheptimidazole methiodide. The quaternary ammonium salts of 2-amino-and 2-methylthiocycloheptimidazole afforded 1-alkylcycloheptimidazol-2(1H)-one on treatment with acid.