Tropones. Part I. The action of alkali on 2-halogenotropones

Abstract

When treated with concentrated aqueous sodium hydroxide, 2-chlorotropone yields only benzoic acid. With more dilute alkali, salicylaldehyde (up to 40%) is also formed. 2-Bromo- and 2-iodo-tropone behave similarly. Deuteriation studies have shown that carbon-3 in the chlorotropone becomes the aldehyde carbon in the rearrangement. This is confirmed by the production of 4-methylsalicylaldehyde by the action of alkali on 2-chloro-6-methyltropone. A mechanism for the formation of the aldehyde is proposed.