Experimental and theoretical structural studies on 4-(2-phenylethyl)-5-(2-furyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione

The structural and conformational features of 4-(2-phenylethyl)-5-(2-furyl)-2, 4-dihydro-3H-1,2,4-triazole-3-thione (1a), which can be related to the biological activity, have been investigated by X-ray diffraction and molecular modeling techniques. Ab initio method (RHF/6-31G) and density functional theory (B3LYP/6-31G(D)) have been used to calculate structural parameters, conformations, and relative energy of two tautomeric specious (1a and 1b) of the title compound. The geometry and the conformation of the thione form, 1a, is well reproduced by the DFT (B3LYP/6-31G(D)) method as compared with X-ray structure in which this form is found. The thione form is also predicted to be 14.42 kcal/mol more stable than the thiol form in the gas-phase by the DFT method.     

Synthesis and properties of 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-5-nitroindazole

N-(2-Azido-5-nitrobenzylidene)-3,5-di-tert-butyl-4-hydroxyaniline (3a) and N-(2-azido-5-nitrobenzilidene) aniline (3b), when heated in dimethylformamide yielded 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-5-nitroindazole (4a) and 2-phenyl-5-nitroindazole (4b), respectively. The structure of4b was confirmed by X-ray analysis. A stable phenoxyl radical was shown to originate from the oxidation of4a with lead (IV) dioxide.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1095–1097, June, 1994.     

Crystal and molecular structure of organosilicon titanium(iv) derivatives: (Me3Si)3SiTi(NEt2)3 and ClTi[N(SiMe3)2]3

An X-ray structural study of two titanium-containing organosilicon compounds, (Me₃Si)₃SiTi(NEt₂)₃ (1) and ClTi[N(SiMe₃)₂]₃ (2), has been performed. The conformation of molecule1 in a crystal is staggered (approximate inherentC ₃ symmetry), the Ti-Si and Ti-N bond lengths are 2.671(2) and 1.874–1.890(5) Å, respectively. A crystal of1 consists of one type of enantiomers (the space group is P4₁2₁2; the absolute configuration has been determined). The structure of2 studied previously has been refined to the value of R=0.029 on the basis of 3442 reflections (the absolute structure has been determined), the Ti-Cl and Ti-N bond lengths are 2.260(1) and 1.926(1) Å, respectively. The strong distortions in the symmetry of the valence environment of the N atoms in the molecules of1, 2, and related structures are caused by electronic effects, in which the conformation of the relevant molecular fragments plays a determining role.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1473–1476, August, 1993.     

A chemo-enzymatic approach to optically active 3-(4-methoxycarbonyl)phenyl-2-methyl-1-propanols

With a view to obtaining both enantiomers of 3-(4-methoxycarbonyl)phenyl-2-methyl-1-propanols, (R)-1 and (S)-1, from the respective racemate, (±)-1, the hydrolysis of its acetate, (±)-2, in the presence of porcine pancreatic lipase (PPL) has been studied. The optical puriry of (R)-1 and (S)-1 thus obtained was unsatisfactory (ee 22–27%), and could not be increased beyondee 33% by repeated enzymatic hydrolysis of the unconverted fraction of the acetate. In contrast with this, the biohydrogenation of 3-(4-methoxycarbonyl)phenyl-2-methyl-2-propen-1-ol (4) with fermentingSaccharomyces cerevisiae afforded (S)-1 of considerably higher optical purity (ee 41–90 %, depending on the strain). The stereochemical correlation of the products obtained in the two biochemical processes under study shows that the PPL-catalyzed hydrolysis of (±)-2 produces preferably (R)-1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 761–766, April, 1995.The authors express their gratitude to the Russian Foundation for Basic Research for financial support (Grant No. 93-03-5893).     

Why N-methyleneformamide, CH2N–CHO, prefers gauche-conformation? A DFT/NBO study

Three possible stable conformations of N-methyleneformamide were studied using Weinhold's Natural bond orbital method. Wavefunctions for the NBO analysis were obtained using B3LYP hybrid functional with 6-311+G(d,p) extended basis set. gauche conformation was predicted to be more stable than trans conformation by ≈2.3 kcal/mol in agreement with earlier studies. At the same time it was found that this preference is due to the strong π_C1–N2↔π_C3–O4 and σ_C3–H5↔n_σN2 repulsive interactions in the planar conformations, and additional conjugative stabilization of the gauche conformation.     

Heterobimetallische Vanadium- und Thallium-2-(dimethylaminomethyl)ferrocenyl-Verbindungen

Zusammenfassung Synthesen und Eigenschaften von 2-(Dimethylaminomethyl)ferrocenyl-Derivaten der Formel (FcN) _n VCl_3–n (FcN=2-(Dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), die aus VCl₃·3THF und (FcN) Li (I) entstehen, werden mitgeteilt. WährendCp ₂VCl₂ (Cp=C₅H₅) mitI unter Bildung vonCp ₂ V(FcN) (4) reagiert, läßt sich VO (acac)₂ (acac=Anion des Acetylacetonates, C₅H₇O₂) in die 2-(Dimethylaminomethyl)ferrocenyl-Verbindung des vierwertigen Vanadiums (FcN)VO(acac),5) überführen. Dagegen entsteht bei Umsetzungen von VOCl₂·2THF mitI das Organovanadium (III)-Derivat Li [(FcN)₂V(O)Cl] (6).Reaktionen von VCl₄·2THF,Cp ₂VCl₂, VOCl₃ undCpVOCl₂ mit (FcN)₃Tl (II) führen unter Bildung von (FcN)₂TlCl (7) zu thermisch instabilen vanadiumorganischen Verbindungen. Eine eingehende Charakterisierung von1–7 erfolgte durch Elementaranalysen, Ermittlung der effektiven magnetischen Momente, IR-, Massen- und NMR-Spektroskopie sowie, insbesondere hinsichtlich der Ausbildung möglicher Chelatstrukturen, durch UV/Vis und Mößbauer-Spektroskopie.

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Heterobimetallic 2-(dimethylaminomethyl)ferrocenyl compounds of vanadium and thallium

Summary Syntheses and properties of 2-(dimethylaminomethyl)ferrocenylderivatives of the composition (FcN) _n VCl_3–n (FcN=2-(dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), which are formed from VCl₃·3THF and (FcN) Li (I), are reported. WhereasCp ₂VCl₂ (Cp=C₅H₅) reacts withI under formation ofCp ₂V(FcN) (4), VO(acac)₂ (acac=anion of acetylacetonate, C₅H₇O₂) can be transformed into the 2-(dimethylaminomethyl)-ferrocenyl compound of tetravalent vanadium (FcN)VO(acac),5). However, when VOCl₂·2THF reacts withI, the organovanadium(III)-derivative Li[(FcN)₂V(O)Cl] (6) is formed.Reactions of VCl₄·2THF,Cp ₂VCl₂, VOCl₃, andCpVOCl₂ with (FcN)₃Tl (II) lead to thermally instable vanadiumorganic compounds under formation of (FcN)₂TlCl (7). A detailed characterization of1–7 was carried out by elementary analysis, determination of effective magnetic moments, IR, mass and¹H NMR spectroscopy as well as — especially referring to the formation of possible chelate structures — by UV/Vis andMöbauer spectroscopy.

     

Synthese und Reaktionsverhalten von 3-(Bis(alkylthio)methylen)-3H-isobenzofuran-1-on-und 2-(Bis(alkylthio)methylen)-3(2H)-benzofuranon-Derivaten

Summary 3(Bis(alkylthio)methylene)-3H-isobenzofuran-1-ones2a–e and 2-(bis(alkylthio)methylene)-3(2H)-benzofuranone derivatives4a–c are obtained by reaction of phthalides1a–d or 3(2H)-benzofuranone (coumaranone3), respectively, with carbon disulfide under basic conditions followed by alkylation. The reaction behaviour of the new compounds2 and4 is investigated. 2-((2-Dimethylthio-1-oxo)ethyl)benzoic acid N,N-dimethylamide (7a) and 2-((2-dimethylthio-1-oxo)ethyl)-benzoic acid 2-methylpiperidide (7b) are surprisingly formed instead of the methylthio substitution products by treatment of2a with the corresponding amine in the presence of aluminum chloride.

Herrn Professor Dr. Dr. h. c.Waldemar Adam zum 60. Geburtstag gewidmet     

The synthesis of 4-(2,6,10-trimethyl-1,3,5,9-undecatetraenyl)benzoic acid based on alkoxy alkene-acetal condensation

4-(2,6,10-Trimethyl-1,3,5,9-undecatetraenyl)benzoic acid (1) was synthesized starting from ethyl 4-formylbenzoate (2) and linalool. The key intermediate, ethyl 4-(2-methyl-3-oxo-1-propenyl)benzoate (5), was obtained by the addition of diethyl acetal (3), prepared from2, to ethyl 1-propenyl ether (EPE) followed by the hydrolysis of the resulting adduct.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–915, May, 1993.     

Design, synthesis, structure and properties of an α-helix cap template derived from N-[(2S)-2-chloropropionyl]-(2S)-Pro-(2R)-Ala-(2S,4S)-4-thioPro-OMe which initiates α-helical structures

A strategy based upon removing the requirement for all of the carbonyl dipoles to align at the same time in the transition state leading to the cyclisation of N-[(2S)-2-chloropropionyl]-(2S)-Pro-(2R)-Ala-(2S,4S)-4-thioPro-OMe to a Zimm-Bragg type α-helix peptide intitator template was successful. Each amide bond of the 12-membered macrocyclic template existed in the trans-rotomeric form. Derivatives of the template were prepared by extending the C-terminus and these were characterised by NMR spectroscopy and restrained simulated annealing. In deuterochloroform solution at low temperature, separate sets of NMR signals were observed for two rapidly interconverting helical conformational isomers of the thioether macrocycle which possessed an appended trialkylammonium ion. A similar time-averaged conformation was also observed in aqueous solution. At −80 °C in d₂-dichloromethane the rate of conformational exchange was slowed sufficiently to obtain resonance assignments and NOE data separately for each isomer. In the minor isomer (40%), the four carbonyl oxygen hydrogen-bond acceptors of the template are aligned in an α-helical conformation and in the major conformer the Pro² carbonyl dipole was anti-aligned with the other three dipoles. Thus, the conformers differ in the orientation of one carbonyl group. Molecular modelling calculations showed that the minor isomer was stabilised by coulombic interactions between the trialkylammonium salt and the carbonyl group dipole moments.     

Saure Hydrolyse von 2-(4-Chlorphenylazo)-2-(N-carbamidino-ureido)-propan

Zusammenfassung Die saure Hydrolyse der Arylazo-Verbindung1 wird beschrieben und interpretiert: Als Zwischenprodukte werden ungeladenes Aryldiazen (Ar–N=N–H) sowie zwitterionisches Aryldiazen (Ar–NH⁺=N:^–)und im weiteren Verlauf des Reaktionsgeschehens 1,4-Diaryltetrazenimionen postuliert.

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Acid hydrolysis of 2-(4-Chlorophenylazo)-2-(N-carbamidinoureido)-propane

Acid hydrolysis of the arylazo compound1 is described and discussed. As reaction intermediates uncharged aryldiazene (Ar–N=N–H) as well as zwitterionic aryldiazene (Ar–NH⁺=N:^–) and subsequently 1.4-diaryltetrazenium ions are postulated.

     

Cyclodextrin Complexation of the Stilbene 4-(2-(4-Tert-butylphenyl)ethen-1-yl)- benzoate and the Self-assembly of Molecular Devices

E-4-(2-(4- tert - butylphenyl) ethen-1- yl)benzoate, E-1^–, photoisomerizes to the Z-1^– isomer and vice versa in the free state and in the binary complexes 2·E-1^–, 2·Z-1^–, 3·E-1^– and 3·Z-1^– where 2 is the urea-linked cyclodextrin N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)-N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea and 3 is N,N- bis(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea. In 2·E-1^–and 3·E-1^– the stilbene occupies both cyclodextrin (CD) components of 2 and 3, whereas in 2·Z-1^– and 3·Z-1^– it only occupies one CD component while the other CD component is unoccupied. 4- tert - Butylphenolate, 4^–, and its carboxylate, 5^–, and sulfonate, 6^–, analogues form the ternary complex 2·Z-1^–·4^– and its analogues and also 3·Z-1^–·4^– and its analogues. These photoisomerize to 2·E-1^–and 3·E-1^– and either free 4^–, 57^– or 6^– and thereby function as molecular devices.     

Computation of conformations of 2-(2-hydroxyethoxy)-3,4-dihydropyran with intramolecular hydrogen bonds

The conformations of 2-(2-hydroxyethoxy)-3,4-dihydropyran were calculated by the methods of molecular mechanics and MNDO/H with and without allowance for the formation of intramolecular hydrogen bonds. Two possible centers of the formation of the intramolecular hydrogen bond,viz., the oxygen atoms of the alkoxy radical and of the dihydropyran cycle, have been considered. The results obtained show that 2-(2-hydroxyethoxy)-3,4-dihydropyran does not exist in any preferable conformation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1202–1203, July, 1994.     

Reaktion von 2-(N-Alkyl-p-hydroxyanilino)-1,4-benzochinonen Diazomethan. N-(Alkyl-p-hydroxyanilino)-4,7-indazolchinone und ihre isomeren N-Methylderivate

The reaction of N-alkyl-p-hydroxyanilinobenzoquinones1 a–d, its acetylderivatives1 ₁–c₁ and the methoxyderivative1 a₂ with diazomethan yields in dependence on the reaction-conditions the indazolquinones2 a–d, 2 a₁–c₁ or2a ₂, the1-methylindazolquinones3 a–d and3 ₁–c₁, and finally the methoxy-1-methylindazolquinones5 a–d. The 2-methyl-isomeres6 a–d are formed only in small amounts. Methylation of2 a with dimethylsulfate gives5 a and6 a in the ratio of appr 2 to 1. Acetylation of2 a–d with acetanhydride leads to the N–O-acetylderivatives, which are easily hydrolyzed to2 a₁–d₁ during work up;3 a d yields3 a₁–d₁. The structures are established by the described crossexperiments and by spectroscopy (UV/VIS, IR, NMR).

Herrn Prof. Dr.G. Zigeuner zum 60. Geburtstag gewidmet.     

The (E)/(Z)-ratio in the reaction of 5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines with bromine

Summary 3-Aryl-, 3-benzyl-, and 3H-5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines3a–h react with bromine in acetic acid solution to give mixtures of the respective 5-aroylmethylene (E) and (Z) diastereomeric derivatives5 and6. They contain more than 85% of the (E)-diastereomers along with some pure isomers. The intermediacy of the 5-bromo derivatives4 is proven and a plausible route of the reaction is presented. Structures of compounds3–6 are evidenced by analytical and spectral data.

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Das Verhältnis von (E)- und (Z)-Isomeren bei der Reaktion von 5-(2-Aryl-2-oxomethyl)-2-thioxo-4-oxo-1,3-thiazolidinen mit Brom

Zusammenfassung 3-Aryl-, 3-Benzyl- und 3H-5-(2-Aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidine3a–h reagieren mit Brom in essigsaurer Lösung zu Gemischen der entsprechenden diastereomeren 5-Arylmethylen-Derivate ((E) und (Z))5 und6. Sie enthalten mehr als 85% des (E)-Diastereomeren. Die intermediäre Natur der 5-Brom-Derivate4 wird bewiesen; ein Reaktionsweg wird vorgeschlagen. Die Strukturen der Verbindungen3–6 werden durch analytische und spektroskopische Daten abgesichert.

     

Reactions of cyclic 1,3-dicarbonyl compounds with 1,2(1,4)-dihydro-1-methyl-2(4)-methylene-N-heterocycles. A new access to 6,12-methano-dibenz[d,g]-[1,3]oxazocinones

Summary The enamine-type methylene-N-heterocycles1–5 react with cyclic 2-ethoxymethylene-1,3-dicarbonyl compounds6 to give 2-[2-(hetarylidene)ethylidene]-1,3-dicarbonyl compounds7–14. The result of the reactions between 1,2-dihydro-1-methyl-2-methylene-quinoline (1a) and cyclic 1,3-dicarbonyl compounds depends on the nature of the dihydro intermediatesA/B. Dehydrogenation of keton intermediatesA results in 2-(1,2-dimethyl-4(1H)-quinolylidene)-1,3-dicarbonyl compounds17–21. Enol intermediatesB with 6-membered dicarbonyl ring form 6,12-methano-dibenz-[d,g][1,3]oxazocinones22–25.¹H NMR spectra and X-ray structure analysis prove the structure of23.

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Reaktionen cyclischer 1,3-Dicarbonylverbindungen mit 1,2(1,4)-Dihydro-1-methyl-2(4)-methylen-N-heterocyclen. Ein neuer Zugang zu 6,12-Methano- dibenz[d,g][1,3]oxazocinonen

Zusammenfassung Aufgrund ihres Enamincharakters reagieren die Methylen-N-heterocyclen1–5 mit cyclischen 2-Ethoxymethylen-1,3-dicarbonylverbindungen6 zu den 2-[2-(Hetaryliden)ethyliden]-1,3-dicarbonylverbindungen7–14. Das Ergebnis der Reaktionen zwischen 1,2-Dihydro-1-methyl-2-methylen-chinolin (1a) und cyclischen 1,3-Dicarbonylverbindungen hängt von der Natur der zwischenzeitlich entstehenden DihydroverbindungenA/B ab. Die Intermediat-KetoneA gehen durch Dehydrierung während der Reaktion in die 2-(1,2-Dimethyl-4(1H)chinolyliden)-1,3-dicarbonylverbindungen17–21 über. Die Intermediat-EnoleB mit sechsgliedrigem Dicarbonylring bilden in intramolekularer Reaktion die 6,12-Methano-dibenz[d,g][1,3]oxazocinone22–25, deren Struktur am Beispiel der Verbindung23 durch¹H-NMR sowie durch Röntgenkristallstrukturanalyse bewiesen wird.

     

Synthesis of N-1-(Indanyloxymethyl) and N-1-(4-Hydroxybut-2-enyloxymethyl) Analogues of the HIV Drugs Emivirine and GCA-186

A series of Emivirine and GCA-186 analogues substituted at N-1 with indan-1-yloxymethyl (6a–6c) and indan-2-yloxymethyl (6d–6f) were synthesized by reaction of the corresponding bis(indanyloxy)methans with uracils having 5-ethyl or 5-isopropyl and 6-benzyl or 6-(3,5-dimethylbenzyl) substituents. A route to the corresponding N-1 substituted 4-hydroxybut-2-enyloxymethyl analogue was also devised. All newly synthesized compounds showed potent activity against wild-type HIV-1, the most active compound being 5-ethyl-1-(indan-1-yloxymethyl)-6-(3,5-dimethylbenzyl)uracil (6b), which was 50-fold more active than Emivirine.     

Synthesis and structures of silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)2Mo(CH2EMe3)2 (E = Si, Ge, Sn)

New silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)₂Mo(CH₂EMe₃)₂ (Ar is 2,6-diisopropylphenyl; E = Si (1), Ge (2), Sn (3)) were prepared in the crystalline state in 58–66% yields by the reactions of the (ArN)₂MoCl₂(DME) complex with alkyllithium derivatives Me₃ECH₂Li (E = Si or Ge) or the Grignard reagents Me₃ECH₂MgCl (E = Ge or Sn). The structures of complexes 1–3 and the known analog (ArN)₂Mo(CH₂Bu^t)₂ (4) were established by X-ray diffraction analysis. Complexes 1–3 were found to be isostructural. The coordination environment about the Mo atom can be described as a distorted tetrahedron. Complex 4 has a similar structure. The Mo-C distance tends to decrease with increasing electron donating ability of the EMe₃ group.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 597–600, March, 2005.     

Synthesis, reactions and X-ray crystal structures of metallacrown ethers with unsymmetrical bis(phosphinite) and bis(phosphite) ligands derived from 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂ (1) and 2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈) (2). These ligands react with Mo(CO)₄(nbd) to form the monomeric metallacrown ethers, cis-Mo(CO)₄{2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂} (cis-3) and cis-Mo(CO)₄{2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different ¹³C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis–trans isomerization in the presence of HgCl₂. Although the cis–trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis–trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4.     

Synthesis of elastomeric polypropylene in bulk using C 1-symmetric ansa-metallocenes. New aspects of the synthesis of 1-(fluoren-9-yl)-2-(2-methyl-5,6-dihydrocyclopenta [f]-1H-inden-1-yl)ethane and complexes of zirconium and hafnium with this ligand

Isomeric 1-(fluoren-9-yl)-2-(2-methyl-5, 6-dihydrocyclopenta [f]-1 H-indenyl) ethanes 1a,b and C ₁-symmetric metallocenes, viz., rac-1-(η⁵-fluoren-9-yl)-2-(2-methyl-5, 6-dihydrocyclopenta [f]-η⁵-inden-1-yl) ethanezirconium dichloride (9) and rac-1-(η⁵-fluoren-9-yl)- 2-(2-methyl-5, 6-dihydrocyclopenta [f]η⁵-inden-1-yl)ethanehafnium dichloride (10), with these ligands were synthesized by modified procedures. The structures of compounds 1b (two crystalline modifications) and 10 were established by X-ray diffraction analysis. The synthesis of polypropylene (PP) in bulk was studied in the presence of polymethylalumoxane-activated metallocenes 9 and 10 in the temperature range of 30–70°C. It was demonstrated that triisobutylaluminum can be used as a cocatalyst. In this case, the molecular weight of PP increases by a factor of ∼2. An increase in the reaction temperature leads to an increase in stereoregularity and crystallinity of PP. The polymer synthesized at high temperatures crystallizes in the γ form. The resulting PP is characterized by a wide range of properties from rigid crystalline thermoplastic to amorphous elastomeric. Samples, which have a high molecular weight and moderate isotacticity, exhibit high elastomeric and durability properties.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 400–413, February, 2005.     

Molecular structure and conformational analysis of chirai (−)-3-(4-bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene

(–)-3-(4-Bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene, capable of inducing spiral supramolecular ordering when introduced to nematic and some smectic mesophases, has been studied by an X-ray structural analysis. The crystals are orthorhombic; at 20 °Ca = 6.055(1),b = 13.282(3),c=20.734(4) Å,V=1668(1) ų,d _calc = 1.380 g cm^–3, space groupP2 ₁2₁2₁ Z=4. The cyclohexene ring has a conformation intermediate between a sofa and a half-chair. The methyl and methoxyl groups are in asyn orientation with respect to the mean plane of the cycle. The angle between the plane of the aryl substituent and the exocyclic double bond is 33°. The observed distortions of bond angles at unsaturated carbon atoms are typical of derivatives of benzylidenecyclohexene. Molecular mechanics calculations demonstrated that the conformation observed in the crystalline state is not the most favorable, and this conformation is stabilized through intermolecular interactions upon stacking in crystals. It was shown that the relative orientation of the methyl and methoxyl groups as well as the orientation of the aryl substituent substantially affect the conformation of the cyclohexene ring.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2437–2442, December, 1995.