New ionic liquid crystal compounds having a 1,3-dithiane or 1,3-dioxane ring

New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-dithiane ring in the central core N-substituted 4-(5-alkyl-1,3-dithian-2-yl)pyridinium bromides and the corresponding 1,3-dioxanes were synthesized and their mesomorphic behaviours compared. The principal feature of these compounds is to exhibit a smectic A phase over a very wide temperature range including room temperature.     

Pathways of conformational isomerization of 4-phenyl-1,3-dioxane

A study of the potential energy surface of 4-phenyl-1,3-dioxane by non-empirical quantum chemical RHF/STO-3G and 6-31G(d) approximations reveals six energetically inequivalent pathways of conformational isomerization of equatorial and axial chair forms.     

New side chain liquid crystalline polysiloxanes containing 1,3-dithiane or 1,3-dioxane rings as mesogenic side groups

New liquid crystal materials: 2-\[p-(9-decenyloxy)phenyl]-5-(p -alkoxyphenyl)-1,3-dioxane( 11 ) and 2-\[p-(9-decenyloxy)phenyl]-5-(p -alkoxyphenyl)-1,3-dithiane( 12 ) were synthesized. The mesomorphic behaviour of these compounds was determined. Though the 1,3-dioxane-type monomer exhibited both SmA and nematic phases, the 1,3-dithiane-type monomer only exhibited a nematic phase. By the hydrosilylation of poly(methylhydrosiloxane) and these monomers, side chain polysiloxanes were synthesized. For the monomers, the transition temperatures of the nematic to isotropic transitions of 1,3-dioxane-type compounds are higher than those of the corresponding 1,3-dithiane-type compounds. However, in the polysiloxane polymer this relation reversed.     

Synthesis and stereochemistry of new spiro[5.5]undecane derivatives with 1,3-dioxane, 1,3-dithiane, or 1,3-oxathiane rings

The synthesis and the structural investigations of spiro[5.5]undecane derivatives with S and O containing heterocycles, exhibiting similar [bis(1,3-oxathiane) spiranes] or different (1,3-dioxane-1,3-dithiane spiranes) heterocycles, in the spirane units are reported.     

Conformational analysis of 1,3-dioxane in nanotubes

Russian Journal of Organic Chemistry - Computer simulation of conformational transformations of 1,3-dioxane molecule within model single-walled carbon nanotubes (hybrid DFT-method PBE/3ζ)...     

Conformational analysis of 5,5-dinitro-1,3-dioxane

Study of conformational transformations of 5,5-dinitro-1,3-dioxane by the method HF/6-31G(d), and also hybrid DFT PBE/3z and RI-MP2/λ2 indicated the only inversion route chair-chair through an intermediate minimum corresponding to the 2,5-twist-form. The potential barrier to this process was estimated and also the features of the intramolecular rotation of the axial and equatorial nitro groups in the chair conformer were investigated.     

Theoretical study on conformational conversion of 1,3-dioxane inside a capsular host

The conformational conversion of 1,3-dioxane guest encapsulated inside a cylindrical capsular host was investigated with PM3 method and single point energies were evaluated by B3LYP method. When entrapped in the capsule, the guest tumbles were slower than that in the free condition. The influences of the inner phase of the capsule on the guest conformational conversion were discussed in detail.     

Salt effects on the conformational behavior of 5-carboxy- and 5-hydroxy-1,3-dioxane

The varied and essential involvement of metal ions and inorganic salts in biological and chemical processes motivated the present study where 5-carboxy- and 5-hydroxy-1,3-dioxanes are used as model frameworks for the evaluation of the conformational behavior of oxygen-containing receptors in the presence of Li(+), Na(+), K(+), Ag(+), Mg(2+), Ca(2+), Ba(2+), and Zn(2+). Thus, the position of equilibria, established by means of BF(3), between diastereomeric cis- and trans-5-substituted-2-phenyl-1,3-dioxanes, in solvent THF and in the presence of 0, 1, and 5 equiv of salt, has been determined. The observed Delta G(o) degrees values for the conformational equilibria of 5-carboxy-1,3-dioxane show that Ag(+), Li(+), and Ca(2+) complexation leads to increased stability of the axial isomer. In the case of the 5-hydroxy-1,3-dioxane, Mg(2+), Ag(+), and Zn(2+) are the metal ions that stabilize the axial conformer of the heterocycle upon association. Interpretation of the experimental observations was based on DFT molecular modeling studies at the Becke3LYP/6-31G* and Becke3LYP/6-31+G** levels of theory. Although gas-phase calculations give Delta E values that are too large when modeling equilibria involving ionic species in polar solution, the computational results confirm the structural and energetic consequences of metal cation coordination to the oxygen atom in carbonyls or ethers. The results derived from the present study contribute to our understanding of the chemical processes involved in molecular recognition and physiological events.     

Zur stereochemie S-alkylierter 1,3-dithiane

The steric relationships of some mono- and bis-sulfonium-salts of 1,3-dithianes previously described by us are discussed by NMR-spectroscopic measurements.     

Conformational analysis of 5-bromo-5-nitro-1,3-dioxane

Conformational analysis of 5-bromo-5-nitro-1,3-dioxane has been performed by computer simulation in terms of HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 quantum chemical methods. The global minimum on the potential energy surface corresponds to the chair conformer with axial nitro group, and the other two minima have been identified as chair conformer with equatorial nitro group and 2,5-twist. All transition states on the route of conformational transformations of the title molecule have been revealed.     

Liquid-crystalline derivatives of 1,3-dioxane

Some 5-(2-pentyl-1,3-dioxanyl) 4-(4-substituted benzylidenamino)benzoates with smectic and nematic liquidcrystalline properties have been synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 759–760, June, 1993.     

Synthesis and conformational analysis of 1,3-azasilinanes

1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature ¹H/¹³C NMR spectroscopy, iteration of the ¹H NMR spectra and quantum chemical calculations showed slight predominance of the Ph_eqMe_ax over the Ph_axMe_eq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol.     

Crystal structures of 2-ferrocenylmethylidenehydrazono-1,3-dithiane and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane

Two compounds of 2-ferrocenylmethylidenehydrazono-1,3-dithiane (1) and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane (2) are synthesized and their single crystal structures are determined by the X-ray diffraction method. Compound 1 belongs to the orthorhombic Pca2₁ space group with the cell parameters: a = 13.989(4) Å, b = 5.785(2) Å, c = 18.231(5) Å, V = 1475.4(7) ų; while compound 2 crystallizes in a monoclinic symmetry, P2₁/c space group with a = 15.320(2) Å, b = 5.8028(6) Å, c = 36.584(4) Å, β = 91.932(1)° and V = 3250.4(6) ų.     

Rotamere 2-Phenyl-1,3-dioxane

By means of dipole moment measurements, NMR-spectroscopical methods and force field calculations of o-, m- and p-substituted 2-phenyl-1,3-dioxanes a systematic study concerning the rotameric behaviour of the phenyl group was performed.In o-substituted 2-phenyl-1,3-dioxanes the preferred conformation of the phenyl ligand was found to be displaced about 60 degs. from thecisoid-bisectional conformer. Introduction of an additional substituent in the second o-position gives rise to a change in the rotameric state, the preferred conformation now being bisectional. In contrast, the barriers resisting rotation about the C_ar–C-2-bond in 2-phenyl-1,3-dioxane and its m- and p-substituted derivates turn out to be much lower. Thus at room temperature an ensemble of approximately bisectional rotamers exists.The conformations and rotational barriers determined are discussed in terms of non bonded and dipole-dipole interactions.

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6. Mitt.:H. Lehner, Mh. Chem.107, 565 (1976).     

Cationic copolymerization of 2-methylene-5,5-dimethyl-1,3-dioxane with 2-methylene-1,3-dioxolane and 2-methylene-1,3-dioxane

Copolymers of the cyclic ketene acetals, 2-methylene-5,5-dimethyl-1,3-dioxane, 3 , (M₁) with 2-methylene-1,3-dioxolane, 4 , (M₂) or 2-methylene-1,3-dioxane, 5 , (M₂), were synthesized by cationic copolymerization. An experimental method was designed to study the reactivity of these very reactive and extremely acid sensitive cyclic ketene acetal monomers. The reactivity ratios, calculated using a computer program based on a nonlinear minimization algorithm, were r₁ = 6.36 and r₂ = 1.25 for the copolymerization of 3 with 4 , and r₁ = 1.56 and r₂ = 1.42 for the copolymerization of 3 with 5. FTIR and ¹H-NMR spectra when combined with the values of r₁ and r₂ showed that these copolymers were formed by a cationic 1,2-polymerization (ring-retained) route. Furthermore the tendency existed to form very short blocks of M₁ or M₂ within the copolymers. Cationic copolymerization of cyclic ketene acetals have the potential to be used for synthesis of novel polymers. © 1996 John Wiley & Sons, Inc.     

New 1,3-dithiane type ionic liquid crystal compounds

New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-dithiane ring in their central core, N -substituted-4-(5-alkyl-1,3-dithian-2-yl)pyridinium bromides ( 8 ), were synthesized. These compounds exhibited a smectic A phase over a very wide temperature range including room temperature.