Conformation analysis. XXVI. Conformational equilibriums in 5,5-disubstituted 1,3-dioxanes

Synthesis and surface properties of chemodegradable anionic surfactants: Sodium carboxylates of cis‐1,3‐dioxane derivatives

“…This analysis showed that acids 3a-e were diastereomerically pure cis-2-n-alkyl-5-carboxy-5-methyl-1,3-dioxanes with an equatorial alkyl group at C-2 and an axial carboxyl group at C-5 of the 1,3-dioxane ring. We are convinced that the direct acetalization reaction of DMPA with the aliphatic aldehydes is a much more convenient method for the synthesis of 3 than the procedures presented earlier, where 1,3-dioxane derivatives with methyl and carboxyl groups at C-5 were obtained with poor or moderate yields by oxidation of the appropriate 5-hydroxy-methyl-5-methyl-substituted 1,3-dioxanes with KMnO 4 (26) or with lead tetraacetate followed by silver nitrate (20).…”

“…1 H NMR spectra of the acids showed, surprisingly, that all were pure cis-isomers, and not the expected mixtures of cis-and transisomers usually obtained in the synthesis of 2,5-di-or 2,5,5trisubstituted 1,3-dioxane derivatives (20)(21)(22)(23). It has been reported that in thermodynamically equilibrated mixtures of isomers of 2,5,5-trisubstituted 1,3-dioxane derivatives with an equatorial "holding" substituent at C-2, and a methyl group geminally located with such substituents as -OH (20), -CH 2 OH (20,21,23), -COCH 3 (22,24), -NO 2 (20), or -COOCH 3 (20) at the C-5 carbon atom, the axial configuration is preferred. The rate of preference is dependent both on the kind of substituent and on the conditions of equilibration process-mostly on the polarity of the solvent used (20).…”

“…It has been reported that in thermodynamically equilibrated mixtures of isomers of 2,5,5-trisubstituted 1,3-dioxane derivatives with an equatorial "holding" substituent at C-2, and a methyl group geminally located with such substituents as -OH (20), -CH 2 OH (20,21,23), -COCH 3 (22,24), -NO 2 (20), or -COOCH 3 (20) at the C-5 carbon atom, the axial configuration is preferred. The rate of preference is dependent both on the kind of substituent and on the conditions of equilibration process-mostly on the polarity of the solvent used (20). Probably, the formation of only cis-isomers of 3 from 1 and 2 in the presence of a polar azeotropic agent is an extreme ex-ample of such preference.…”

Synthesis, Surface Properties, and Hydrolysis of Chemodegradable Anionic Surfactants: Diastereomeric Sodium Carboxylates Derived from 1,3-Dioxane

“…1). This observation is an extreme example of the influence of the solvent dielectric constant on the equilibrium state of a cis ⇔ trans isomerization reaction of, for example, 2-isopropyl-5-methyl-5-nitro-or 2-isopropyl-5-carboxymethyl-5-methyl-1,3-dioxanes, which was observed by Eliel (16).…”

“…From the literature data it is well known that 2,5,5-trisubstituted 1,3-dioxane derivatives containing the methyl group and substituents such as -CH 2 OH, -COOCH 3 , or -COCH 3 , at the C5 carbon atom of the 1,3-dioxane ring constitute mixtures of geometric isomers with more or less appreciable predomination of cis isomers with axial configurations of polar substituents (16,17). In the present paper we show that the composition of acetalization reaction products 3, obtained from aliphatic aldehydes 1 and 2,2-bis(hydroxymethyl)propionic acid, or isomerization reaction products cis-3 ⇔ trans-3, is strongly dependent on the reaction medium.…”