István Jalsovszky

The molecular structure of thiane-1-oxide from electron diffraction

Abstract The molecular structure of thiane-1-oxide has been determined by gas-phase electron diffraction. According to the electron diffraction data the molecule has a chair conformation with C s symmetry. The oxygen atom takes axial position. The following bond distances ( r g in A) and bond angles (deg) were obtained (with estimated total errors): S-C, 1.816±0.004; (S)C-C(C), 1.538±0.003; (C)C-C(C), 1.539±0.003; S-O, 1.483±0.003; C-H, 1.123±0.003; S-C-C, 112.5±0.1; (S)C-C-C(C), 111.5±0.4; (C)C-C-C(C), 114.8±0.7; C-S-C, 91.1±0.7; O-S-C, 108.1±0.3.

Orientational ordering and low-temperature libration in the rotor-stator cocrystals of fullerenes and cubane.

Cocrystals of cubane and fullerenes, C60-cubane and C70-cubane, show distinct rotational ordering transitions. We studied the corresponding structural changes with temperature-dependent X-ray diffraction and the thermodynamics of the phase transitions with adiabatic microcalorimetry and differential scanning calorimetry. C60-cubane has one phase transition around 130 K from a high-temperature fcc phase with freely rotating C60 to a low-temperature orthorombic phase in which the fullerene rotation is frozen. The corresponding enthalpy change is approximately 1170 J/mol, and the entropy change is 9.6 J/(mol K). C70-cubane has two phase transitions. Around 380 K, the high-temperature fcc phase with freely rotating C70 transforms into a bct phase in which the C70 rotates uniaxially around an axis that precesses around the c direction with a full opening angle of 40 degree. Around 170 K, the uniaxial rotation also freezes out, with an accompanying structural transition to monoclinic and enthalpy and entropy changes of 620 J/mol and 8.7 J/(mol K), respectively. The low-temperature specific heat was analyzed in terms of the Debye-Einstein model to estimate the librational energies of the fullerenes and Debye temperatures. We found very similar values for the two cocrystals, approximately Elib = 2.2 meV and TDebye = 23 K. For reference, we also measured the specific heats of pure C60 and C70 and found Elib = 2.96 meV and TDebye = 32 K for C60 and Elib = 1.9 meV and TDebye = 20 K for C70.

Conformational analysis of thiane-1 imides: an x-ray study of thiane-1-tosylimide and diastereoisomeric 2-alkyl- and 4-phenylthiane-1-tosylimides

Abstract The molecular structures of thiane-1-tosylimide and its cis / trans -2-Me, cis -2-Pr i , trans -2-Bu t and cis / trans -4-Ph derivatives have been investigated by X-ray diffraction. The results confirm our earlier 13 C NMR assignments of configurations, giving direct evidence for ring geometry and conformational preference of ring substituents. They show that the electron-withdrawing tosylimino group is axial in both thiane-1-tosylimide and cis disubstituted analogues, whilst it is equatorial in trans compounds. The C -substituents are always equatorial. Distortions of chair-shaped thiane rings of sulphilimines are compared with those of cyclic sulphoxides and sulphonium salts, and explained by steric effects. Conformations of 1,2-disubstituted thiane-1-imides are controlled by both syn -axial interaction and steric repulsion between 1-tosylimino and 2-alkyl groups, with the latter being the more significant. The conformation of the exocyclic S -tosylimide part is also compared with that of known acyclic N -arylsulphonyl sulphilimines. Rotations about S IV —N, NS VI and S VI C ar bonds are discussed and deviations from S -symmetric conformations and “Koch- Moffitts cases IIa of conjugation” are interpreted in terms of steric effects conjugation, n —σ* type stereoelectronic effects and sulphur(IV)—oxygen interaction; S IV C. S VI N and S VI O bond lengths are discussed on the same basis. The SON sp 2 group may substitute SO 2 in the case “case-IIa of conjugation” with the aryl group. In antiperiplanar position there exists a maximum interaction between the nitrogen lone pair and the S VI O bond, resulting in a significant shortening of the S VI N bond.

Stereoselective synthesis of cis and trans n-tosyl sulphilimines and sulphoxides from 2-alkylthianes and 2-alkylthiolanes assignments of configurations

Abstract Thiane and thiolane derivatives with 2-methyl, 2-ethyl, 2-isopropyl and 2-tert-butyl groups were prepared and converted to cis and trans sulphilimines and sulphoxides by various stereoselective methods. Cis-sulphilimines were formed by using t-BuOCl and TsNH - in a two-stage process, while cyclic sulphides were converted by chloramine-T predominantly to trans-sulphilimines. Sulphoxides enriched in cis and trans isomers were obtained by different methods of oxidation. Diastereoisomeric product distributions were measured by hplc and the configurations of diastereoisomers were assigned by 13 C NMR spectroscopy. Preferred conformations of sulphilimines were determined by analysis of 13 C NMR and X-ray data. As shown by 13 C NMR spectra, the conformations of sulphilimines and sulphoxides are analogous.

Molecular structures of cyclic sulfilimines without and with intramolecular sulfur-oxygen interaction: an X-ray study

Abstract 3-Phenylbenzo[1.3.2]dithiazolium ylide 1.1 dioxide (1) and its o-methoxycarbonyl derivative (2) have been prepared and their structures established by X-ray crystallography from diffractometer data. Compound 1 (C12H9NO2S2) crystallizes in the triclinic space group P 1 with a = 6.664(1), b = 7.881(1), c = 12.437(2) A , α = 98.81(1), β = 97.44(1), γ = 113.05(1)°, V = 580.9(4) A 3 , Z = 2, Dc = 1.51 g.cm−3 and μ(CuKα) = 4.00 mm−1. Compound 2 (C14H11NO4S2) crystallizes in the orthorhombic space group P212121, with a = 7.620(1), b = 8.887(1), c = 20.022(2) A , V = 1355.9(5) A 3 , Z = 4, Dc = 1.57 g.cm−3 and μ(CuKα) = 3.65 mm−1. The crystal structures were solved by direct methods and refined to R = 0.062 for 1 and R = 0.028 for 2, using 1663 and 1424 observed reflections, respectively. In the cyclic N-sulfonyl sulfilimines 1 and 2 the characteristic bond distances and bond angles involving S(IV) and S(VI) atoms do not differ significantly from those found earlier for acyclic sulfilimines. Owing to S(IV)…O(carbonyl) close contact the sulfur(IV) atom in 2 exhibits a sulfuran-like configuration with t almost linear (171°) N = S(IV)…O array ( 1.61 + 2.68 = 4.29 A ). The conformations of 1 and 2 have similar features. In both cases the five-membered dithiazolium ring is practically planar and the two aryl rings about sulfur(IV) atom are nearly perpendicular to the CarS(IV)Car plane (“butterfly conformation”). In contrast with acyclic sulfilimines, the benzene ring connected to S9VI) atom is constrained to be coplanar with the S(VI)NS(IV) plane (Koch and Moffitts case I of conjugation).

The extent of transannular sulfur-nitrogen interactions in stereoisomeric 1,5-thiazocine derivatives: A semiempirical MO study

Abstract The stereoisomers of 7-acetylbenzo[b]naphtho[1,8-f,g]thiazocin-8(7H)-one 13-oxide (1) were studied by a semiempirical MO method (AM1). The structure of the sulfoxide-lactam-type title compound is determined by the position of the sulfinyloxygen (equatorial/axial; E/A) and by the cis/trans configuration of both the endocyclic and exocyclic amide moieties (enC/ enT and exC/exT). The shape of the eight-membered 1,5-thiazocine ring (boat/chair/twist-chair; Bt/Ch/Tw) is controlled by the variation of configuration parameters. By using an automatic research program the expected eight energy minima were found on the potential energy hypersurface. The structure belonging to the global minimum (1a) agrees well with that found experimentally by X-ray methods (Bt-E-enC-exT). Here, in the global minimum, the sulfur atom exhibits a sulfurane-like configuration with a relatively short transannular S ··· N nonbonded distance (2.85 A). An analogous situation emerges by rotating the exocyclic amide moiety in the cis position (ΔE = 0.9 kcal mol−1). The change in the sulfur configuration (E → A) causes an increase in energy (ΔE = 3.8–9.3 kcal mol−1) and the disappearance of the sulfurane-like geometry with elongation of the S ··· N distance (3.15–3.16 A). The cis-trans change in the endocyclic amide part is associated with a Bt → Ch transformation causing appreciable steric constraint and energy increase (ΔE = 11.5–14.1 kcal mol−1). The sulfurane geometry is somewhat distorted and the S ··· N distance is significantly increased (3.28–3.30 A). Simultaneous E → A and enC → enT changes both bring about a Bt → Tw transformation with a large increase in energy (ΔE = 7.0–22.2 kcal mol−1); the sulfurane geometry disappears and the r(S ··· N) distance increases (3.06 A). The extremely high energy value obtained for the Tw-A-enT-exT structure is attributed both to the twist-chair ring structure and the unfavorable close contact of oxygen atoms belonging to the sulfur and endo-carbonyl-carbon atoms. The spirosulfurane isomer (3) of the title compound is computed to be more stable than 1a (ΔE = −11 kcal mol−1).

Vibrational spectra of C60·C8H8 and C70·C8H8 in the rotor-stator and polymer phases

C(60).C(8)H(8) and C(70).C(8)H(8) are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C(60)C(8)H(8)) and poly(C(70)C(8)H(8)) resulting from a solid-state reaction occurring on heating. On the basis of the spectra, we propose a connection pattern for the fullerene in poly(C(60)C(8)H(8)), where the symmetry of the C(60) molecule is D(2h). On illuminating the C(60).C(8)H(8) cocrystal with green or blue light, a photochemical reaction was observed leading to a product similar to that of the thermal polymerization.

Transannular sulfur-nitrogen interactions in stereoisomeric 1,5-thiazocine derivatives: An ab initio MO study

Abstract The stereoisomers of 7-acetyl-benzo[b]naphtho[1,8-f,g]thiazocin-8(7H)-one 13-oxide (1) were studied by ab initio MO method at the HF/3–21G level of theory, and the results were compared with those obtained at the semiempirical MO (AM1) level of theory. Of the eight energy-minimum structures optimized by the semiempirical methods two were rather distorted in their molecular geometries. These two structures were annihilated at the ab initio level of theory. The relative order of stability obtained by the two methods was qualitatively the same. Quantitatively, however, the corresponding structures differed somewhat from each other both in their geometry data and relative energy values. Bader-type electron density analysis suggested that the transannular S…N interactions in some stereoisomers of 1,5-thiazocine derivative 1 may be regarded in the vicinity of 10% of a single bond.

Structure and properties of new liquid crystalline cubane‐1,4‐dicarboxylic acid derivatives

New symmetrical esters of cubane‐1,4‐dicarboxylic acid have been prepared. These compounds have the bulky cubane moiety as the central building block. Five classes of derivative have been synthesized: (a) bis[(4‐alkyl)phenyl]cubane‐1,4‐dicarboxylates; (b) bis[(4‐alkoxy)phenyl]cubane‐1,4‐dicarboxylates; (c) the two chiral derivatives bis(cholestenyl)cubane‐1,4‐dicarboxylate, and (S)‐bis[4‐(2‐methylbutyloxycarbonyl)phenyl]cubane‐1,4‐dicarboxylate; (d) three members of the bis [4‐(2,2‐alkoxycarbonylvinyl)phenyl]cubane‐1,4‐dicarboxylates; and (e) bis[(4′‐ethoxycarbonyl)‐1,1′‐biphenyl‐4‐yl]cubane‐1,4‐dicarboxylate. The shorter homologues of the alkoxyphenyl ester series exhibited a nematic (N) phase. No mesophase was observed for the pentyl derivative, while the higher homologues showed a smectic A (SmA) phase according to X‐ray investigations. The 4‐alkylphenyl and chiral derivatives showed only a melting point. The double swallow tailed bis[4‐(2,2‐alkoxycarbonylvinyl)phenyl)]cubane‐1,4‐dicarboxylates also exhibited no mesophase behaviour. On increasing the number of aromatic rings on both sides of the central cubane moiety, N and SmA phases appeared at higher temperatures. In binary mixtures of homologues of alkoxyphenylcubane esters, the temperature range of the SmA phase of the individual compounds became wider and enantiotropic in nature.

Molecular structure of tetrahydrothiophene-1-oxide and cis-2-methyltetrahydrothiophene-1-oxide from electron diffraction

The molecular structures of tetrahydrothiophene-1-oxide (I) and cis-2-methyltetrahydrothiophene-1-oxide (II) have been studied by gas-phase electron diffraction. Both molecules have an asymmetric ring conformation. They can be regarded as frozen forms along the pseudorotational pathway with phase angles and amplitudes 145.2 ± 1.6° and 48.5 ± 0.4° for I(3T2) and 154.9 ± 2.5° and 43.2 ± 0.8° for II(between 3T2 and 3E); 0° phase angle corresponds to a half-chair ring with C2 symmetry (4T3). The SO bond takes a pseudoaxial orientation in both molecules, and the 2-methyl group is in a nearly equatorial position in II. The following bond distances (rg/A) and bond angles (°) were obtained (with estimated total errors): molecule I: S—C, 1.8277 ± 0.0037; (S)C—C, 1.5398 ± 0.0034; (C)C—C(C), 1.5408 ± 0.0034; SO, 1.4843 ± 0.0032; C—H, 1.1342 ± 0.0025; S—C—C, 105.3 ± 0.3 and 106.9 ± 0.3; (S)C—C—C, 102.2 ± 0.3 and 111.5 ± 0.3; C—S—C, 92.0 ± 0.3; C—S—O, 110.0 ± 0.4; molecule II: S—C, 1.8344 ± 0.0038; (S)C—C, 1.5432 ± 0.0032; (CH)C—C(CH2), 1.5442 ± 0.0032; SO, 1.4852 ± 0.0031; C—C(H3), 1.5438 ± 0.0032; C—H, 1.1243 ± 0.0026; S—C(CH3)—C, 107.2 ± 0.1; C(CH3)—C—C, 105.6 ± 0.6; (S)C(H2)—C—C,108.1 ± 0.7; S—C(H2)—C, 110.3 ± 0.7; C—S—C, 91.7 ±0.4; C—S—O, 105.3 ± 0.3; C—C(S)—C(H3), 110.9 ± 1.0; S—C—C(H3), 111.6 ± 0.3.