Tropones. Part III. The mechanism of the production of m-hydroxybenzaldehydes from 2-chlorotropones

Abstract

Using a variety of oxidising agents, nitro-2-chlorotropones are converted into m-hydroxybenzaldehydes in which all the substituents of the original tropone are retained. Thus, 2-chloro-7-nitrotropone gives 4-chloro-3-hydroxy-2-nitrobenzaldehyde, and 2-chloro-5-nitrotropone, gives 2-chloro-3-hydroxy-6-nitrobenzaldehyde. 2-Chloro-5,7-dinitrotropone, obtained by nitrating 2-chloro-5-nitrotropone, gives 2-chloro-3-hydroxy-4,6-dinitrobenzaldehyde as the sole aldehyde when treated with oxidising agents, but in aqueous acetic acid elimination of chloride competes with oxidation and 5-hydroxy-2,4-dinitrobenzaldehyde is obtained. Deuteriation studies have shown that when 2-chloro-7-nitrotropone is converted into 4-chloro-3-hydroxy-2-nitrobenzaldehyde, C-6 becomes the aldehyde carbon.