Cationic polymerization of dimethyl-1,3-butadienes

The cationic polymerizations of dimethyl-1,3-butadienes with various catalysts in methylene chloride and toluene have been investigated. The activity of catalysts decreased in the order WCl₆ > AcClO₄ > SnCl₄·TCA > BF₃OEt₂. The homopolymerization rate of dimethyl-1,3-butadienes with WCl₆, AcClO₄, and SnCl₄·TCA decreased in the order 1,3-dimethyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > 1,2-dimethyl-1,3-butadiene > 2,4-hexadiene. The polymers prepared with WCl₆, SnCl₄.TCA, and BF₃OEt₂ were rubberlike polymers or white powders, whereas those prepared with AcClO₄ were oily oligomers. The 1,4-propagation increased in the order 1,2-dimethyl-1,3-butadiene < 1,3-dimethyl-1,3-butadiene < 2,3-dimethyl-1,3-butadiene < 2,4-hexadiene. This order may indicate that the steric effect of methyl group determine primarily the microstructure of the polymer. The relative reactivity of dimethyl-1,3-butadienes toward a styryl cation decreased in the order 1,3-dimethyl-1,3-butadiene > 1,2-dimethyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > 2,4-hexadiene. This order may be explained in terms of the stability of the resulting allylic cation.     

Relationships between chemical structures and solubility,diffusivity, and permselectivity of 1,3-butadiene and n-butane in 6FDA-based polyimides

The solubility, diffusivity, and permselectivity of 1,3-butadiene and n-butane in seven different polyimides synthesized from 2,2-bis (3,4-carboxyphenyl) hexafluoropropane dianhydride (6FDA) were determined at 298 K. The influence of chemical structures on physical and gas permeation properties of 6FDA-based polyimides was studied. Solubility of 1,3-butadiene in 6FDA-based polyimides can be described by a dual-mode sorption model. 1,3-Butadiene-induced plasticization is considered to be associated with the increasing permeabilities of 1,3-butadiene and n-butane and the decreasing permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system containing a high concentration of 1,3-butadiene. It was found that controlling the solubility of 1,3-butadiene in an unrelaxed volume in 6FDA-based polyimides is very important to maintain the high permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system. Changing the  C(CF₃)₂ linkage to a  CH₂ ,  O linkage, removing methyl substituents at the ortho position of the imide linkage, and changing the p-phenylene linkage to an m-phenylene linkage in the main chains in some 6FDA-based polyimides are effective to decrease fractional free volume and restrict the solubility of 1,3-butadiene in the unrelaxed volume of a polymer matrix. The 6FDA-based polyimides restricting the solubility of 1,3-butadiene in an unrelaxed volume exhibit high separation performance in the 1,3-butadiene/n-butane mixed gas system compared with conventional glassy polymers and, therefore, are potentially useful membrane materials for the separation of 1,3-butadiene and n-butane in the petrochemical industry. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2941–2949, 1999     

Grafting of Lanthanum Complexes on a Functionalized Graphene Surface: Theoretical Investigation on Ethylene and 1,3-Butadiene Homo- and Co-Polymerization

In this contribution, we describe the use of graphene as an efficient catalyst support and the role it plays in increasing the Lewis acidity of the supported metal complexes. By a density functional theory study, we show that the [La(N(SiMe₃)₂)₃] complex can be easily grafted on graphene-OH and -COOH functionalized surfaces. Two stable mono-grafted compounds, (gO)-[La(N(SiMe₃)₂)₂] and (gOO)-[La(N(SiMe₃)₂)₂], are formed, behaving as stronger Lewis acids than the previously reported silica grafted analogues. To study the role of the graphene support in catalysis, we also computed the catalytic activity of the alkylated (gO)-[La(CH₃)₂] and (gOO)-[La(CH₃)₂] complexes in the ethylene and 1,3-butadiene homo- and co-polymerization reactions. Both compounds are efficient catalysts for the homo-polymerization of the ethylene and 1,3-butadiene. For the 1,3-butadiene homo-polymerization, the stereoselectivity outcome of the reaction differs according to the grafting site. The results computed for the co-polymerization reaction, finally, show that the high stability of the allylic products leads to the formation of block copolymers.     

rac-[CH2(3-tert-butyl-1-indenyl)2]ZrCl2/MAO in the Copolymerization of Olefins and Dienes

Olefin-diene copolymerizations in the presence of C₂ symmetric zirconocene rac-[CH₂(3-tert-butyl-1-indenyl)₂]ZrCl₂/MAO catalytic system have been reported and rationalized by experimental and molecular modeling studies. Ethene gives 1,2-cyclopropane and 1,2-cyclopentane, 1,3-cyclobutane, and 1,3-cyclopentane units in copolymerization with 1,3-butadiene, 1,4-pentadiene, and 1,5-hexadiene, respectively. Propene-1,3-butadiene copolymerizations lead to 1,2 and 1,4 butadiene units and to a low amount of 1,2-cyclopropane units.     

The stereospecific preparation of two perfluoro-1,3-butadiene synthons; (E)-1-trimethylsilyl-1,2,3,4,4-pentafluoro-1,3-butadiene and (E)-1-tributylstannyl-1,2,3,4,4-pentafluoro-1,3-butadiene

(E)-1-Trimethylsilyl-1,2,3,4,4-pentafluoro-1,3-butadiene (1) can be stereospecifically prepared by Pd(0)/CuI catalyzed cross-coupling of (Z)-1-tributylstannyl-1,2-difluoro-2-trimethylsilylethene with iodotrifluoroethene. The corresponding (E)-1-tributylstannyl-1,2,3,4,4-pentafluoro-1,3-butadiene can be prepared via the stereospecific conversion of 1 with Bu₃SnOSnBu₃/KF (catalysis) to the corresponding vinylstannane.     

Thermal isomerization and decomposition of 1,2-butadiene in shock waves

1,2-Butadiene diluted with Ar was heated behind reflected shock waves over the temperature and the total density range of 1100–1600 K and 1.36 × 10^?5 ? 1.75 × 10^?5 mol/cm³. The major products were 1,3-butadiene, 1-butyne, 2-butyne, vinylacetylene, diacetylene, allene, propyne, C₂H₆, C₂H₄, CH₄, and benzene, which were analyzed by gas chromatography. The UV kinetic absorption spectroscopy at 230 nm showed that 1,2-butadiene rapidly isomerizes to 1,3-butadiene from the initial stage of the reaction above 1200 K. In order to interpret the formation of 1,3-butadiene, 1-butyne, and 2-butyne, it was necessary to include the parallel isomerizations of 1,2-butadiene to these isomers. The present data were successfuly modeled with a 82 reaction mechanism. From the modeling, rate constant expressions were derived for the isomerization 1,2-butadiene = 1,3-butadiene to be k₃ = 2.5 × 10¹³ exp(?63 kcal/RT) s^?1 and for the decomposition 1,2-butadiene = C₃H₃ + CH₃ to be k₆ = 2.0 × 10¹⁵ exp(?75 kcal/RT) s^?1, where the activation energies, 63 kcal/mol and 75 kcal/mol, were assumed. These rate constants are only applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc.     

CO2 laser-induced photolysis of spirohexane: Time resolved observation of vibrationally excited 1,3-butadiene

Vibrationally excited spirohexane (SHX) generated in CO₂ laser irradiation undergoes photolysis producing ethylene, 1,3-butadiene and a C₄ compound as major products. Collisional energy pooling plays a major role in the multiphoton excitation process. Time-resolved formation of 1,3-butadiene is monitored by UV absorption from which the unimolecular rate constant for SHX dissociation is found to be 5.6 × 10⁵ s⁻¹. A red shift of 4O nm observed in the transient UV absorption spectrum has been assigned to nascent 1,3-butadiene, which suggests that vibrationally hot 1,3-butadiene molecules are formed. The effects of laser energy fluence and pressure of SF₆ as a sensitizer on dissociation yield are also investigated.     

New synthesis of steroidal tetrahydrooxazin-2-ones

In the DMSO/NaHCO₃ system, 16α-aminomethyl-, 16α-benzylaminomethyl- and substituted benzylaminomethyl-3-methoxy-17β-tosyloxyestra-1,3, 5(10)-triene (3, 5a-k) do not undergo oxidation, but form a tetrahydrooxa-zin-2-one ring (7, 8a-k) via neighboring group participation. Under similar conditions, 16β-aminomethyl-3-methoxy-17β-tosylestra-1,3,5(10)-triene (4) decomposes into 16-methylene-3-methoxyestra-l,3,5(10)-trien-17-one (12).     

Regioselectivity of 1,3-Butadiene Diels-Alder Cycloaddition to C59XH (X=N, B)

The regioselectivity of Diels-Alder cycloaddition of 1,3-butadiene to C₅₉XH (X=N, B) has been studied theoretically by means of the semiempirical AM1 and DFT (B3LYP/6-31G^*) methods. The mechanisms of the cycloaddition on some selected 6.6 bonds of C₅₉XH (X=N, B) have been analyzed. For C₅₉NH, the activation energies become lower with the addition site increasingly farther from the N atom; however, they are all higher than that of the reaction of 1,3-butadiene with C₆₀. In contrast to C59NH, for the cycloaddition to C₅₉BH, the activation energies corresponding to 2,12/r- and 2,12/f-transition states, in which the addition sites are the nearest ones to the B atom, are the lowest ones, and are lower than that of the reaction of 1,3-butadiene with C₆₀ by over 18 kJ·mol⁻¹, and the products corresponding to these two transition states are the most stable ones. The different electronic natures of N and B atoms results in different effects on the Diels-Alder reactions of 1,3-butadiene with C₅₉NH and C₅₉BH; the former makes the reactivity of C₅₉NH reduced and the latter makes the reactivity of C₅₉BH enhanced, relative to that of C₆₀.     

Syntheses and Structures of 5-Membered Heterocycles Featuring 1,2-Diphospha-1,3-Butadiene and Its Radical Anion

LGa(P₂OC)cAAC 2 features a 1,2-diphospha-1,3-butadiene unit with a delocalized π-type HOMO and a π*-type LUMO according to DFT calculations. [LGa(P₂OC)cAAC][K(DB-18-c-6)] 3 [K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene radical anion 3 ⋅ ⁻ was isolated from the reaction of 2 with KC₈ and dibenzo-18-crown-6. 3 reacted with [Fc][B(C₆F₅)₄] (Fc=ferrocenium) to 2 and with TEMPO to [L^−HGa(P₂OC)cAAC][K(DB-18-c-6)] 4 [K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene anion 4⁻ . The solid state structures of 2 , 3 K(DB-18-c-6], and 4 [K(DB-18-c-6] were determined by single crystal X-ray diffraction (sc-XRD).     

Tris(acetonitrile)tricarbonylchromium(0) catalyzed 1,4-addition of hydrogen to 1,3-dienes

The Cr(CO)₃(CH₃CN)₃ complex is found to catalyze the 1,4-addition of hydrogen to 1,3-dienes such as 2-methyl-1,3-butadiene, trans-1,3-pentadiene, and trans, trans-2,4-hexadiene at low temperature (40°) and low H₂ pressure (20 psi). For trans, trans-2,4-hexadiene the only product obtained when D₂ is used is 2,5-dideuterio-cis-3-hexene. The catalytic 1,4-hydrogenation can be carried out in neat dienes, and turnover numbers for the catalyst of greater than 3000 have been observed.     

Polymerization and copolymerization of 2-phthalimidomethyll 1,3-butadiene. II. Kinetic study of the polymerization of 1,3-butadiene and of the copolymerization of 1,3-butadiene with 2-phthalimidomethyl 1,3-butadiene initiated by bis-(η3-allyl nickel trifluoroacetate)

The kinetics of the polymerization of 1,3-butadiene initiated by bis(η³-allyl nickel trifluoroacetate) prepared in benzene was studied in methylene chloride at 40°C. The reaction is first order with respect to the monomer, second order with respect to the catalyst in contrast to the case in which solvent is benzene. We have shown that the presence of a polar molecule (fe, N-methyl phthalimide) decreases the overall rate of polymerization. The apparent reactivity ratios for the system 2-phthalimidomethyl 1,3-butadiene (1)-1,3-butadiene (2) are r₁ = 0.65 ± 0.006 and r₂ = 0.48 ± 0.015.     

The reaction of trichlorosilyltetracarbonyliron hydride (HFe(CO)4SiCl3) with conjugated dienes

Isoprene, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene react with HFe(CO)₄SiCl₃ by addition of the Fe---H function to the diene. Isoprene appears to add predominantly 1,4 and 2,3-dimethyl-1,3-butadiene appears to add 1,2, while 1,3-butadiene may add both ways. In the case of isoprene and 1,3-butadiene loss of CO from the addition compound gives a stable π-allyl- Fe(Co)₃SiCl₃ product. Either cis- or trans-1,3-pentadiene is reduced to pentene by HFe(CO)₄SiCl₃.     

Gehinderte ligandbewegungen in übergangsmetallkomplexen: XXX. Synthese und dynamisches verhalten von tricarbonyl-η4-dien-trimethylphosphit-wolfram(0)-komplexen

UV irradiation of [W(CO)₅P(OCH₃)₃] (I) in the presence of 1,3-butadiene (II), (E)-1,3-pentadiene (III), 2-methyl-1,3-butadiene (IV), (E,E)-2,4-hexadiene (V), 2- methyl-1,3-pentadiene (VI) and 1,3-cyclohexadiene (VII) yields the [W(CO)₃- P(OCH₃)₃(η⁴-diene)] complexes (VIII–XIII). While VIII–XII form predominantly facial isomers in the a-form, the 1,3-cyclohexadiene complex XIII exists in both possible facial a- and f-forms, which have different relative positions of the P(OCH₃)₃ ligand towards the η⁴-diene moiety. XIII shows therefore two different hindered ligand mobilities, an a–f-isomerization (ΔG₂₀₀³ 36.2 ± 0.2 kJ/mol) and a carbonyl scrambling (ΔG₂₅₀³ 50.6 ± 0.2 kJ/mol) such as the other complexes VIII–XII. These ligand movements were studied by temperature dependent ¹³C and ³¹P NMR spectra. VIII–XIII were further characterized by IR and ¹H NMR spectroscopy and C, H elemental analyses.     

A New Efficient and Stereoselective Synthesis of 1,3E,5Z-Undecatriene

1,3E,5Z-Undecatriene is synthesized by coupling of Z-heptenyl copper reagent, obtained through carbocupration of acetylene, with 1-chloro-1E,3-butadiene, in the presence of 5% NiCl₂(PPh₃)₂     

Recent advances in the neodymium catalysed polymerisation of 1,3-dienes

The benefits of using a homogeneous neodymium-based catalyst for the industrial “high cis” polymerisation of 1,3-butadiene are underlined. Preformed homogeneous catalysts for the “high cis” polymerisation of 1,3-butadiene based on Nd(carboxylate)₃/diisobutylaluminium hydride/^tbutyl chloride have been examined. The effects of changing (a) the order of catalyst component addition, (b) the carboxylate component and (c) the halogen component, on catalyst homogeneity, activity and polymer characteristics have been examined.     

2,3-Bis(diphenylphosphino)-1,3-butadien

2,3-Bis(diphenylphosphino)-1,3-butadiene A method for synthesis of the title compound is described, using the readily available 2,3-bis(diphenylphosphinoyl)-1,3-butadiene ( 1 ) as the starting material. For the protection of the diene system, 1 is first converted into the 1,4-dibromo- and 1,4-dichloro derivatives 2a and b , respectively, by addition of Br₂ or Cl₂, respectively. The structure of 2b has been determined by single-crystal X-ray diffraction. The molecule has a centrosymmetrical (E)-configuration. Reduction of the phosphinoyl groups by HSiCl₃(to give the bis(diphenylphosphino)compound 3), followed by removal of the Cl-atoms using Zn powder, affords the bis(diphenylphosphino)butadiene 4 . Compounds 3 and 4 give quaternary phosphonium salts 5 and 6 , respectively, on addition of CH₃OSO₂F or CH₃I. The sulfur analogue of 1 is formed on treatment of 4 with elemental sulfur.     

Reactions of ozone with olefins: Ethylene,allene, 1,3-butadiene,and trans- 1,3-pentadiene

The reactions of O₃ with ethylene, allene, 1,3-butadiene, and trans-1,3-pentadiene have been studied in the presence of excess O₂ over the temperature range 232 to 298 K. The initial O₃ pressure was varied from 4–18 mtorr, and the olefin pressure was varied from 0.1 to 4.5 torr (ethylene), 2.8 to 39.6 torr (allene), 52.7 to 600 mtorr (1,3-butadiene) or 26.2 to 106 mtorr (trans-1,3-pentadiene). The O₃ decay was monitored by ultraviolet absorption. The reactions are first order in both O₃ and olefin, and the rate coefficients are independent of the O₂ pressure. For the O₃-ethylene system, various diluent gases (O₂, N₂, air) were used and the rate coefficients were found to be independent of the nature of the diluent gas. The various rate coefficients fit the Arrhenius expressions (k in cm³ s^?1): where the reported uncertainties are one standard deviation and R is in cal/mol K.     

Features of deposit formation from 1,3-butadiene over Pd catalysts

Formation of carbonaceous deposits from 1,3-butadiene has been investigated over a group of Pd catalysts. Hydrogen generated in decomposition of diene at 473–523 K participates in diene hydrogenation, resulting in the formation ofn-butenes. XRD measurements have confirmed formation of dissolved carbon (PdC_x) phase. DRIFT measurements over 0.06 wt.%Pd/γ-Al₂O₃ have revealed bands at 1575 and 1464 cm⁻¹, suggesting formation of carboxylate structures. Selectivity of the competitive hydrogenation in 1,3-butadiene and propene mixture R(BD)/R(Pr) has been measured on “fresh” and poisoned samples. Accumulation of deposits has decreased the R(BD)/R(Pr) ratio. The results have been interpreted by transport hindrance and a greater prevalence of non-selective low coordination sites on the poisoned surface. Measurements over Pd, Cu, Pt and Rh catalysts have shown that the highn-butane selectivity over Pt and Rh is also accompanied with low R(BD)/R(Pr) values, suggesting that thermodynamic and mechanistic factors are not entirely separable. Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday     

CYCLOADDITION-ELIMINATION REACTIONS OF 4-ALKYL-5-ARYLIMINO-1,2,3,4-THIATRIAZOLINES

Abstract

In previous work, we have shown that 4-alkyl-5-arylsulfonylimino-1,2,3,4-thiatriazolines (1, R = ArSO₂) react with unsaturated compounds (a=b) at the decomposition temperature of 1 via the intermediacy of a thiaziridinimine or its open-chain 1,3-dipole.