Conformational analysis of a 12‐membered crown dithioether in the solid state and in solution

Abstract

The solid-state molecular structure and the conformational behaviour in solution of the 12-membered crown dithioether 8-methyl-1,4-dioxa-7,10-dithiacyclododecane-5,12-dione were studied by x-ray crystallography, 1 H and 13 C NMR spectroscopy and molecular mechanics. The conformational rigidity of some constituent structural fragments allowed a detailed analysis of the structure and distribution of the conformers. A protocol for studies of multiconformational equilibrium was developed by means of the combined use of structure calculations and dynamic NMR measurements.

Synthesis and extraction properties of oxathiacrown compounds containing benzyl groups

“…In the 13 C NMR spectra of macrocycles 5 and 6 the number of signals in the aliphatic region was 9 and 11, which clearly confirms the proposed structures. The range of shielding of the remote protons was significantly less than for protons of CH 2 groups linked to sulfur, which is in good agreement with data previously obtained for 12-membered thiacrown ethers [18]. Systematic analysis of the structure of multiplets in the 1 H NMR spectra together with information on cross peaks in the correlation pictures enabled an unequivocal assignment to be made of all the signals in the 13 C NMR and of the multiplets in the 1 H NMR spectra (see EXPERIMENTAL).…”

“…Systematic analysis of the structure of multiplets in the 1 H NMR spectra together with information on cross peaks in the correlation pictures enabled an unequivocal assignment to be made of all the signals in the 13 C NMR and of the multiplets in the 1 H NMR spectra (see EXPERIMENTAL). This has been noted previously for thiacrown [18], crown [19], and azacrown ethers [20]. The starting point was the assignment of the benzylic CH 2 group signals where the spin of the carbon atom is linked with the ortho protons of the phenyl groups in both compounds 5 and 6 [16,17].…”

Cyclohexane-Based Conformationally Controlled Crowns and Podands

“…A complete conformational analysis for crown compounds is an extremely difficult task due to the enormous number of possible conformers (for example, see [37]). Relatively rigid structural fragments may simplify the analysis [37].…”