Macrocyclization of <i>bis</i>(7''-oxooctyl)hexanedioates with phthalic and terephthalic dihydrazides
In this article the authors consider a macrocyclization reaction of bis(7-oxooctyl)adipate from tetrahydropyran under the influence of phthalic and terephthalic dihydrazides because significant portion of macroheterocycles used in complexation comprises aryl moieties linked to the nitrogen atom. We have found that the [1+1]-condensation reaction of bis(7-oxooctyl)adipate with phthalic dihydrazide at room temperature in dioxane under high-dilution conditions does not result, even with a low yield, in macrolide containing phthalic dihydrazide fragment. The same situation is observed using an equimolar mixture of dioxane and water as a solvent; in this case, however, high yield are seen in the corresponding azine derived previously via [1+1]-condensation of the above-mentioned substrate [bis(7-oxooctyl)adipate] with hydrazine hydrate. The formation of macrolide with azine fragment can be explained by the possibility of hydrazine to be generated in the breakdown of phthalic dihydrazide and its involvement into the [1+1]-condensation reaction with bis(7-oxooctyl)adipate. The macrocyclization reaction of bis(7-oxooctyl)adipate with terephthalic dihydrazide was aimed at producing the compound containing dihydrazide fragments. However, yield of the latter does not exceed 10%. It is apparent that in these reactions a lower reactivity of phthalic and terephthalic dihydrazides is conditioned by participation of the conjugated aromatic fragment that causes a decrease in basicity of NH2-groups.