A Review on the Conformational Aspects in the 1,3-Dioxane System

Anteunis, M.; Tavernier, D.; Borremans, Frans

doi:10.3987/r-1976-02-0293

Cited by 105 publications

(46 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…45 Molecular mechanics calculated the 1,4-twist (2a) and 2,5-twist (2b) conformers to be 3.1 kcal/mol and 4.2 kcal/mol, respectively, higher in energy than the chair conformer (1). 29,30 The HF chair (1)-1,4-twist (2a) free energy difference (⌬GЊ c-t ϭ 4.93 for 1,4-dithiane at 298.15 K was comparable to the estimated experimental value for cyclohexane (⌬GЊ c-t ϭ 4.9 kcal/mol), 6 lower than some of the estimated experimental values for 1,3-dioxane (⌬GЊ c-t ϭ 5.7 kcal/ mol), 6,13,68 and larger than the estimated experimental values for 1,3-dithiane (⌬GЊ c-t ϭ 2.9 kcal/mol). ‡ ) is 3.151 Å, which is less than the sum of the van der Waals radius (r vdw ϭ 1.80 Å) for sulfur.…”

Section: Resultsmentioning

confidence: 91%

A computational study of conformational interconversions in 1,4‐dithiacyclohexane (1,4‐dithiane)

Freeman

Derek

2003

J Comput Chem

View full text Add to dashboard Cite

Ab initio molecular orbital theory with the 6-31G(d), 6-31G(d,p), 6-31+G(d), 6-31+G(d,p), 6-31+G(2d,p), 6-311G(d), 6-311G(d,p), and 6-311+G(2d,p) basis sets and density functional theory (BLYP, B3LYP, B3P86, B3PW91) have been used to locate transition states involved in the conformational interconversions of 1,4-dithiacyclohexane (1,4-dithiane) and to calculate the geometry optimized structures, relative energies, enthalpies, entropies, and free energies of the chair and twist conformers. In the chair and 1,4-twist conformers the C-Hax and C-Heq bond lengths are equal at each carbon, which suggest an absence of stereoelectronic hyperconjugative interactions involving carbon-hydrogen bonds. The 1,4-boat transition state structure was 9.53 to 10.5 kcal/mol higher in energy than the chair conformer and 4.75 to 5.82 kcal/mol higher in energy than the 1,4-twist conformer. Intrinsic reaction coordinate (IRC) calculations showed that the 1,4-boat transition state structure was the energy maximum in the interconversion of the enantiomers of the 1,4-twist conformer. The energy difference between the chair conformer and the 1,4-twist conformer was 4.85 kcal/mol and the chair-1,4-twist free energy difference (deltaG degrees (c-t)) was 4.93 kcal/mol at 298.15 K. Intrinsic reaction coordinate (IRC) calculations connected the transition state between the chair conformer and the 1,4-twist conformer. This transition state is 11.7 kcal/mol higher in energy than the chair conformer. The effects of basis sets on the 1,4-dithiane calculations and the relative energies of saturated and unsaturated six-membered dithianes and dioxanes are also discussed.

show abstract

Section: Resultsmentioning

confidence: 91%

A computational study of conformational interconversions in 1,4‐dithiacyclohexane (1,4‐dithiane)

Freeman

Derek

2003

J Comput Chem

View full text Add to dashboard Cite

show abstract

“…In all the investigated structures the 1,3-dioxane rings exhi- bit chair conformations and the bond lengths, bond angles, and torsion angles show normal values. [26] In 5a the dihedral angles between the best plane of each heterocycle (the plane formed by the exocyclic bonds of the acetal carbon atom) and the plane of the corresponding aromatic ring exhibit values close to 90°( C 7 The investigated crystal of 5b (selected from the mixture of isomers) contains a centrosymmetric molecule (group P 21/c) and represents the unlike isomer. Two of the aromatic rings exhibit orthogonal disposition (…”

Section: Solid-state Molecular Structuresmentioning

confidence: 99%

“…A Ph ϭ 13.04 kJ/mol) [26] determines the strong shifting of the conformational equilibria involving the flipping of the 1,3-dioxane rings towards the conformer with both aryl groups in equatorial orientation. Owing to the chirality of the spiro skeleton, these compounds show separable enantiomers and are obtained under the usual conditions of the acetalisation reaction as racemic mixtures (P and M configurations of the helix, Scheme 2).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Structure of New Macrocycles Including Spiro‐1,3‐Dioxane Units

et al. 2003

View full text Add to dashboard Cite

The efficient synthesis of new macrocycles — “monomers” and “dimers” — containing spiro‐1,3‐dioxane units is reported. The structure of the compounds was determined from high‐field NMR spectra, FAB and MALDI+ mass spectrometry investigations. The solid‐state molecular structures of three compounds was determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

show abstract

“…Four configuration isomers are possible: cis-cis-cis (I); cis-cis-trans (II); cis-trans-trans (III) and trans-trans-trans (IV) (Scheme 7). The A-values of methyl and ethyl substituents at position 5 of the 1,3-dioxane ring are very close (A Me = 3.7 kJ/mol [10]; A Et = 3.3 kJ/mol [10]), while the aromatic substituent in the ketal part (positions 2', 2", 2"') strongly prefers the axial orientation. The isomers of 5 exhibit anancomeric structures (as the NMR spectrum of the row product shows) with axial orientation of the aromatic group and with statistically equal axial and equatorial orientations of the methyl and ethyl groups at positions 5', 5" and 5"'.…”

Section: Scheme 4 Synthesis Of Compdmentioning

confidence: 96%

Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

Florian¹,

Cîrcu

Toupet

et al. 2006

Open Chemistry

View full text Add to dashboard Cite

Abstract:The synthesis and the stereochemistry of new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives are reported. The anancomeric structure and the axial orientation of the aryl group with respect to all 1,3-dioxane rings, and the cis-trans isomerism of some of the compounds are revealed. The data are supported by NMR investigations and by the molecular structure of one compound determined by single crystal X-ray diffractometry.

show abstract

A Review on the Conformational Aspects in the 1,3-Dioxane System

Cited by 105 publications

References 0 publications

A computational study of conformational interconversions in 1,4‐dithiacyclohexane (1,4‐dithiane)

A computational study of conformational interconversions in 1,4‐dithiacyclohexane (1,4‐dithiane)

Synthesis and Structure of New Macrocycles Including Spiro‐1,3‐Dioxane Units

Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

Contact Info

Product

Resources

About