Synthesis of isotactic polystyrene-block-polyethylene by the combination of sequential monomer addition and hydrogenation of 1,4-<Emphasis Type="Italic">trans</Emphasis>-polybutadiene block

Herein, we demonstrate the synthesis of a well-defined diblock copolymer consisting of isotactic polystyrene (iPS) and linear polyethylene, isotactic polystyrene-block-polyethylene (iPS-b-PE), by the combination of sequential monomer addition and hydrogenation. Isospecific living polymerization of styrene and living trans-1,4-polymerization of 1,3-butadiene were catalyzed by 1,4-dithiabutandiyl-2,2′-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by triisobutyl aluminum modified methylaluminoxane (MMAO) at room temperature to provide highly isotactic polystyrene (iPS) and 1,4-trans-polybutadiene (1,4-trans-PBD) with narrow molecular weight distribution. Furthermore, the iPS-b-1,4-trans-PBD was synthesized via sequential monomer addition in the presence of complex 1 and MMAO. The hydrogenation of the 1,4-trans-PBD block was promoted by RuCl₂(PPh₃)₃ used as a catalyst to produce iPS-b-PE.     

Cationic polymerization of butadiene using a titanium tetrachloride—<Emphasis Type="Italic">tert</Emphasis>-butyl chloride catalytic system

Cationic polymerization of butadiene using a titanium tetrachloride—tert-butyl chloride catalytic system allows one to synthesize with high rates and yield fully soluble polybutadiene with controlled molecular characteristics. It was shown that the obtained cationic polybuta diene is characterized by predominantly 1,4-trans-structure and reduced unsaturation. The macromolecules of the cationic polybutadiene contain the initial tert-butyl and end chlorine-containing units.     

Synthesis and structure of 1-(buta-1,3-dien-2-yl)pyrazoles and their behavior in Diels-Alder reactions

A convenient procedure has been developed for the synthesis of cis-and trans-isomeric 1-(buta-1,3-dien-1-yl)-1H-pyrazoles by reaction of the corresponding pyrazoles with β-methylacrolein diethyl acetal and subsequent 1,4-cleavage of the nucleophilic substitution products. The behavior of the title compounds in Diels-Alder reactions with maleic anhydride has been studied. According to the ¹H NMR data, 1-(buta-1,3-dien-1-yl)-1H-pyrazole is a mixture of cis and trans isomers. Butadienylpyrazoles having methyl groups in the pyrazole ring do not react with maleic anhydride.     

Chemistry of Acyl(imidoyl)ketenes: IX. Synthesis and Thermolysis of 3-Aroyl-8-chloro-1,2-dihydro-4<Emphasis Type="Italic">H</Emphasis>-pyrrolo[2,1-<Emphasis Type="Italic">c</Emphasis>][1,4]benzoxazine-1,2,4-triones

Reactions of 3-Z-aroylmethylene-6-chloro-3,4-dihydro-2H-1,4-benzoxazine-2-ones with oxalyl chloride afford 3-aroyl-8-chloro-1,2-dihydro-4H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones and Z-3-(2-aryl-2-chlorovinyl)-6-chloro-2H-1,4-benzoxazine-2-ones. Aroyl(imidoyl)ketenes generated by decarbonylation of pyrrolobenzoxazinetriones undergo dimerization through [4+2]-cycloaddition to form 4-aroyl-3-aroyloxy-2-(2-oxo-2H-1,4-benzoxazin-3-yl)-1H, 5H-pyrido[2,1-c][1,4]benzoxazine-1,5-diones.     

Oxidative trifluoroacetamidation of (1<Emphasis Type="Italic">E</Emphasis>,3<Emphasis Type="Italic">E</Emphasis>)-1,4-diphenylbuta-1,3-diene and 1,1,4,4-tetraphenylbuta-1,3-diene

Reactions of trifluoroacetamide with (1E,3E)-1,4-diphenylbuta-1,3-diene and 1,1,4,4-tetraphenylbuta-1,3-diene in the oxidative system t-BuOCl–NaI have been studied. The reaction with (1E,3E)-1,4-diphenylbuta-1,3-diene afforded three products, N,N′-(phenylmethylene)bis(trifluoroacetamide), 3-chloro-4-iodo- 2,5-diphenyl-1-(trifluoroacetyl)pyrrolidine, and trifluoro-N-[(3E)-2-hydroxy-1,4-diphenylbut-3-en-1-yl]acetamide, with a high overall yield. 1,1,4,4-Tetraphenylbuta-1,3-diene failed to react with trifluoroacetamide.     

Comparative reactivity of substituted 1,3-and 1,4-thiasilinane <Emphasis Type="Italic">S</Emphasis>-oxides in the sila-Pummerer rearrangement and inversion of the thiocarbonyl group

The thermal sila-Pummerer rearrangement of diastereomeric 2,3,3-trimethyl-1,3-thiasilinane S-oxides was studied. Introduction of the methyl group in the 2 position of 3,3-trimethyl-3-thiasilinane S-oxide slows down the rearrangement. When heated in CCl₄, the trans isomer (2-Me_eq, SO_eq) converts into the cis isomer (2-Me_eq, SO_ax) which rapidly rearranges into 2,2,7-trimethyl-1,6,2-oxathiasilepane. On the contrary, the isomeric 2,4,4-trimethyl-1,4-thiasilinane S-oxide is thermally stable up to 160°C in DMSO. The inversion at the sulfur atom in 2,3,3-trimethyl-1,3-thiasilinane S-oxides and 2,4,4-trimethyl-1,4-thiasilinane S-oxides under the action of triethyloxonium tetrafluoroborate was studied. The trans isomer of 2,3,3-trimethyl-1,3-thiasilinane S-oxide (2-Me_eq, SO_eq) forms with Et₃O⁺BF ₄ ^? a salt which decomposes in two ways. The first involves recovery of the starting sulfoxide due to Sn2 substitution at the carbon atom of the ethoxy group, and the second, convertion into the cis isomer (2-Me_eq, SO_ax) which rearranges into 2,2,7-trimethyl-1,6,2-oxathiasilepane. Under the same conditions, the cis isomer of 2,3,3-trimethyl-1,3-thiasilinane S-oxide (2-Me_eq, SO_eq) decomposes to form siloxanes. trans-2,4,4-Trimethyl-4-thiasilinane S-oxide (2-Me_eq, SO_eq) under the action of Et₃O⁺BF ₄ ^? convers into the cis isomer (2-Me_eq, SO_ax). The B3LYP/6-311G(d,p) theoretical analysis showed that the thermal inversion at the sulfur atom in the compounds studied has a high energy barrier.     

Thiocyanation of <Emphasis Type="Italic">N</Emphasis>-arylsulfonyl-, <Emphasis Type="Italic">N</Emphasis>-aroyl-, and <Emphasis Type="Italic">N</Emphasis>-[(<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl)benzimidoyl]-1,4-benzoquinone imines

Reactions of thiocyanate ion with N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinone imines follow the 1,4-addition pattern, and the adducts undergo intramolecular cyclization to give the corresponding N-substituted 5-amino-1,3-benzoxathiol-2-ones as final products.     

Synthesis of azamacrocyclic compounds by cyclocondensation of aliphatic α,ω-diamines with acetone

Cyclocondensation of 1,4-diaminobutane and 1,6-diaminohexane with acetone afforded the corresponding 18- and 22-membered trans-azamacrocyclic Curtis compounds in high yield, which contain two azomethine and amine nitrogen atoms. A complex mixture of the products formed containing less than 25% of 16-membered azamacrocyclic cis- and trans-isomers when reacting 1,3-diaminopropane with acetone.     

<Emphasis Type="Italic">S</Emphasis>-functional derivatives of 3,4-dihydro-2<Emphasis Type="Italic">H</Emphasis>-1,4-thiasilines

The first cyclic unsaturated S-functional derivatives of 4,4-diphenyl-3,4-dihydro-2H-1,4-thiasiline, S-oxide, S,S-dioxide, and S-sulfonimide, were prepared. Oxidation of the hydrolytically less stable 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline leads to the corresponding sulfoxide and sulfone along with the ring opening products, siloxanes containing the sulfoxide or sulfonyl group.     

Kinetic and thermodynamic parameters of hydrogen release during the heterogeneous catalytic dehydrogenation of <Emphasis Type="Italic">cis</Emphasis>- and <Emphasis Type="Italic">trans</Emphasis>-isomers of perhydro-m-terphenyl

Comparative studies on the temperature dependence of the dehydrogenation of cis- and trans-isomers of perhydro-m-terphenyl are performed in a flow catalytic reactor. Rate constants and equilibrium constants of all elementary acts of this reaction are calculated on basis of experimental data using the KINET 0.8 program for the mathematical modeling of the kinetics of complex reactions. The resulting data indicate that perhydro-m-terphenyl cis- and trans-isomers structural differences have no appreciable effect on dehydrogenation.     

Synthesis of tertiary amines containing <Emphasis Type="Italic">gem</Emphasis>-dichlorocyclopropane and cycloacetal fragments

Reactions of secondary amines containing gem-dichlorocyclopropane and cycloacetal fragments with allyl chloride, trans-1,3-dichloropropene, benzyl chloride, and chloromethyl-gem-dichlorocyclopropane were studied. The corresponding tertiary amines were obtained in 20–85% yield. Microwave radiation stimulates N-alkylation of the secondary amine containing the heterocyclic moiety. The structures of the tertiary amines prepared were studied. The configuration of the double bond in the trans-1,3-dichloropropene derivative is retained.     

Oxidation of aromatic compounds: XV. Oxidation of arylacetylenes in a system HF-PbO<Subscript>2</Subscript>

The oxidation of symmetrically substituted diarylacetylenes ArC≡CAr (Ar=C₆H₄R) containing strong electron-withdrawing groups R = 4-COMe, 4-CO₂Me, 3-CO₂Et, and 4-NO₂ in a system HF-PbO₂ at ?10÷?20°C led within 0.5–3 h to the formation of Z,Z-1,2,3,4-tetrakis(aryl)-1,4-difluorobuta-1,3-dienes ArFC=C(Ar)?(Ar)C=CFAr. The butadiene structures obtained exist in solutions as s-cis-and s-trans-conformers and in the crystalline state are present in the stable s-cis-form.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-dichlorobis(ethylendiamine) rhodium(III) with univalent anions

The crystal structures of the compounds trans-[Rh(en)₂Cl₂]Cl₂ · H₅O₂ (I), trans-[Rh(en)₂Cl₂]ClO₄ (II), and trans-[Rh(en)₂Cl₂]ReO₄ (III) are determined. The crystal data are: I, a = 10.860(3) Å, b = 7.795(2) Å, c = 9.023(3) Å; β = 111.56(10)°, P2₁/c space group, Z = 4, d _x = 1.875 g/cm³; II, a = 6.593(2) Å, b = 8.309(3) Å, c = 11.922(4) Å, α = 83.55(10)°, β = 79.80(10)°, γ = 75.38(10)°, P \(\bar 1\) space group, Z = 2, d _x = 2.106 g/cm³; III, a = 6.533(2) Å, b = 16.391(4) Å, c = 12.411(3) Å; β = 98.30(10)°, P2₁/c space group, Z = 4, d _x = 2.749 g/cm³. The compounds are examined by IR spectroscopy and powder XRD. The solubility of the isolated crystalline phases in water decreases in the following order: trans-[Rh(en)₂Cl₂]Cl₂·H₅O₂ > trans-[Rh(en)₂Cl₂]ClO₄ > trans-[Rh(en)₂Cl₂]ReO₄.     

Enantioselective microbial synthesis of (<Emphasis Type="Italic">S</Emphasis>)-7,8-difluoro-3,4-dihydro-3-methyl-2<Emphasis Type="Italic">H</Emphasis>-[1,4]benzoxazine

New strains of Rhodococcus erythropolis 25 and Microbacterium paraoxydans 20-11c actinobacteria were used to obtain (S)-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine (99.6% ee) by enantioselective microbial hydrolysis of the corresponding racemic N-acetyl derivative.     

Determination of astaxanthin and astaxanthin esters in the microalgae <Emphasis Type="Italic">Haematococcus pluvialis</Emphasis> by LC-(APCI)MS and characterization of predominant carotenoid isomers by NMR spectroscopy

The oily product ZANTHIN® consists of natural astaxanthin, which is manufactured from the microalgae Haematococcus pluvialis by supercritical CO₂ extraction. An HPLC method was developed to separate all of the components of the complex astaxanthin extract using a C₃₀ column. The separation resulted in different isomers of astaxanthin accompanied by two other carotenoids. The main component consisted of astaxanthin singly esterified with several different fatty acids. C18:3, C18:2, C18:1 and C16:0 were identified as the most commonly occurring fatty acids. Doubly esterified astaxanthin was also found, although in lower concentrations compared to singly esterified astaxanthin. After performing a detailed fatty acid analysis by GC-MS, the peaks from the extract were assigned via HPLC-MS. A trans to cis transmutation of the all-trans compound was performed by thermal treatment in order to obtain an enrichment of cis isomers as the basis for unambiguous identification via NMR experiments. The all-trans as well as the 9- and 13-cis isomers of astaxanthin were characterized in detail by UV/Vis, ¹H, and ¹H,¹H COSY NMR spectroscopy.     

Dithiophosphorylation of nerol and geraniol trimethylsilyl derivatives

Reaction of tetraphosphorus decasulfide with О-(cis- and trans-3,7-dimethylocta-2,6-dien-1-yl)-trimethylsilanes affords О,О-bis(cis- and trans-3,7-dimethylocta-2,6-dien-1-yl) S-(trimethylsilyl)dithiophosphates.     

Solvothermal synthesis and crystal structure of a 1d coordination polymer: [Ni(1,4-BDC)(N-MIM)<Subscript>2</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (1,4-BDC = 1,4-benzenedicarboxylic acid,N-MIM = <Emphasis Type="Italic">N</Emphasis>-methylimidazole)

A new metal-organic coordination polymer, namely [Ni(1,4-BDC)(N-MIM)₂] _n (I) (1,4-BDC = 1,4-benzenedicarboxylic acid and N-MIM = N-methylimidazole), has been synthesized under solvothermal conditions by using N-MIM as solvent and characterized by elemental analysis, IR, and X-ray single-crystal diffraction. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic system, space group C2/c. The 1,4-BDC ligand adopts a bis(bidentate) chelating mode to connect two adjacent Ni(II) centers to form a one-dimensional (1D) zigzag chain. The adjacent chains are further linked through hydrogen bonds and π-π stacking interactions, forming a three-dimensional (3D) supramolecular framework. The unit cell parameters for I: a = 17.250(10), b = 7.214(4), c = 16.506(7)Å, β = 125.53(4)°, V = 1671.6(15)ų, Z = 4.     

Potential function of the internal rotation of a methacrolein molecule in the ground (<Emphasis Type="Italic">S</Emphasis> <Subscript>0</Subscript>) electronic state

The structural parameters of s-trans- and s-cis-isomers of a methacrolein molecule in the ground (S₀) electronic state are determined by means of MP2 method with the cc-pVTZ basis set. Kinematic factor F(φ) is expanded in a Fourier series. The potential function of internal rotation (PFIR) of methacrolein in this state is built using experimental frequencies of transitions of the torsional vibration of both isomers, obtained from an analysis of the vibrational structure of the high-resolution UV spectrum with allowance for the geometry and difference between the energy (ΔH) of the isomers. It is shown that the V_n parameters of the potential function of internal rotation of the molecule, built using the frequencies of the transition of the torsional vibrations of s-trans- and s-cis-isomers of the methacrolein molecule, determined from vibrational structure of the high-resolution UV spectrum and the FTIR spectrum, are close.     

Reactions of arylsulfinyl chlorides and <Emphasis Type="Italic">N</Emphasis>-(arylsulfonyl)arylsulfinimidoyl chlorides with <Emphasis Type="Italic">p</Emphasis>-aminophenols

In reactions of arylsulfinyl chlorides and N-(arylsulfonyl)arylsulfinimidoyl chlorides with p-aminophenols formed N-arylthio-1,4-benzoquinone imines, evidently through a stage of N-arylsulfinyl-4-aminophenols and N-(N-arylsulfonyl)arylsulfinylimidoyl-4-aminophenols that under the reaction conditions eliminate respectively H₂O and ArSO₂NH₂.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-sulfonyl-1,4-benzoquinone imines with sodium azide

Depending on the conditions and the order of addition of the reactants, reactions of N-sulfonyl-1,4-benzoquinone imines with sodium azide afforded N-(3-azido-4-hydroxyphenyl)alkane(arene)sulfonamides, N-(3-azido-4-oxocyclohexa-2,5-dienylidene)alkane(arene)sulfonamides, and N-(3,5-diazido-4-hydroxyphenyl)-alkanesulfonamides. Quantum chemical calculations showed that the reactions begin with addition of azide ion to the quinone imine.