Vinylation Reaction Research Articles

New Method for Preparation of Poly(enamino-enaryloxynitriles) and Thermal Properties

A kinetic study on enaryloxynitriles via nucleophilic vinylic substitution reactions of various phenol derivatives with 1-chloro-1-phenyl-2,2-dicyanoethene was conducted in the presence of 1,4-diazabicyclo[2,2,2]octane (DABCO). The reaction was applied to solution polymerization of diphenol and diamine derivatives with p-bis(1-chloro-2,2-dicyanovinyl)benzene, which gave various poly(enamino-enaryloxynitriles) with moderate molecular weights in good yields. Thermal properties such as thermal curing and thermal stability were examined by differential scanning calorimetry and thermogravimetric analysis. The poly(enamino-enaryloxynitriles) showed similar curing to typical polyenaminonitriles and polyenaryloxynitriles.

Regiospecificity of reactions of vinyl chloride-maleic anhydride copolymer with dimethylformamide

Interaction of macromolecules of vinyl chloride-maleic anhydride copolymer with dimethylformamide molecules was studied by kinetic, thermodynamic, and spectroscopic methods.

ChemInform Abstract: Nucleophilic Vinylic Substitutions of λ3-Vinyliodanes

Abstract Because of the excellent nucleofugality of the λ3-phenyliodanyl group, which shows a leaving group ability about 106 times greater than triflate, λ3-vinyl(phenyl)iodanes serve as highly reactive species in nucleophilic substitutions. This review summarizes the nucleophilic vinylic substitutions of λ3-vinyl(phenyl)iodanes. The reaction rates and mechanism of the nucleophilic vinylic substitutions change depending on the structure of λ3-vinyliodanes; the nature of the substituents at the β-vinylic carbons is especially important. β-Monoalkyl-λ3-vinyliodanes undergo bimolecular nucleophilic vinylic substitutions (SN2) with exclusive inversion of configuration under mild conditions, which, hitherto, has been considered to be impossible on the bases of experimental results and theoretical calculations. Vinylic SN1 reactions generating vinyl cations, ligand coupling reactions on hypervalent iodine(III), and addition–elimination and elimination–addition reactions, are also discussed.

Hydrido(acylenolato)cobalt(III)-Verbindungen mit Trimethylphosphan- Liganden: Insertionsreaktionen mit Alkinen und die ersten Carbonylcobalt(III)-Komplexe / Hydrido(acylenolato)cobalt(III) Compounds Containing Trimethylphosphane Ligands: Insertion Reactions with Alkynes and the First Carbonylcobalt(III) Complexes

Abstract Formal insertion of phenylethyne into Co-H functions of mer-octahedral acyl(enolato)-cobalt(III) hydrides 1-3 proceeds under ambient conditions affording η1-vinylcobalt(III) compounds where the dianionic acyl(enolato) ligands are derived from 2-formyl-4-phenyl-cyclohexanone (4), 1-formyl-cyclohexan-2-one (5), and 3-hydroxo-2,3-diphenyl-propenal (6). Dissociation and association of trimethylphosphane results in a reversible transformation of penta-coordinate complexes 4 -6 into hexa-coordinate ones 7 -9, respectively, involving different tautomeric vinyl species. In toluene solution 9 rearranges by reductive C,C coupling into a 5,6-η2-olefin(enolato)cobalt(I) complex 10. Trimethylsilylethyne undergoes a hydrolytic desilylation reaction which is followed by reductive C,C-coupling reactions of acyl and vinyl functions selectively producing chelating η1-enolato-5,6-η2-olefin ligands in cobalt(I) com ­ pounds 13 -16 where the (ax,eq)chelating ligands are derived from 1-formyl-cyclohexan-2-one (13), 3-hydroxo-2,3-diphenyl-propenal (14), 2-formyl-α-tetralone (15), and 2-formyl-4-tert-butyl-cyclohexanone (16). An axial position of the enolato-O donor in the trigonal bipyramidal configuration of complex 15 has been confirmed by X-ray diffraction analysis. With 1,4-bis(trimethylsilyl)buta-diyne 1,2-addition in cobalt(III) hydrides 2, 3, 11 (as deriverd from 2-formyl-α-tetralone), and 12 (as derived from 2-formyl-4-tert-butyl-cyclohexanone) produces 2-metalated vinyl groups in compounds 17 -20. Dissociation of trimethylphosphane from 17 and 19 does not activate C,C coupling at the cobalt(III) centre of penta-coordinate 21 and 22. Steric congestion in compounds 17, 18, and 20 favours exchange of trimethylphosphine for carbon monoxide affording the first octahedral carbonyl complexes of cobalt (d6) (23 -25). In the crystal and in solution a meridional configuration is adopted by complex 23 with the CO group in a position opposite to the acyl function.

α-Substitution of β-Thienylcarbamates: Alkylation, Vinylation and Pd-Catalyzed Coupling Reactions

Reaction of the trilithio derivative of di- t-butyl thiophene-3,4-diyldicarbamate 4 with alkyl halides has led to 2-alkylthiophenedicarbamates 9 and 11 and 4-alkylthieno[3,4–d]imidazolones 12. Acid catalyzed α-alkylation of 4, using α-branched or functionalized aldehydes, has allowed the synthesis of divinylthiophenes 13 and thieno[3,2–b]pyridines 14– 16, respectively. Pd-catalyzed coupling reactions involving halo- or dihalothienylcarbamates 10, 17, 18 were studied. One or two alkenyl, alkynyl, aryl groups were introduced on the thiophene nucleus.

An investigation of vinyl-ester?styrene bulk copolymerization cure kinetics using Fourier transform infrared spectroscopy

A Fourier transform infrared (FTIR) spectroscopy technique was developed to investigate the effects of reaction temperature and reactant composition on the isothermal curing kinetics of commercial vinyl nester resins comprised of vinyl–ester monomer (dimethacrylate of diglycidyl ether of bisphenol A DGEBA) and styrene. This technique enables a more complete evaluation of the bulk copolymerization reaction of vinyl–esterstyrene systems by monitoring the depletion of vinyl–ester and styrene double bonds independently. The results indicate that the rate of fractional conversion of styrene double bonds is initially less than that of vinyl–ester vinyl groups. However, styrene monomer continues to react after conversion of vinyl–ester double bonds has ceased. In addition, the overall extent of conversion was found to increase with increasing isothermal cure temperature, and it was observed that higher styrene concentration enhances final conversion of vinyl–ester double bonds and not styrene double bonds. Increasing styrene monomer concentration also resulted in lowering the apparent activation energy for the reaction of vinyl groups from both monomers as characterized by an empirical autocatalytic model used to fit the conversion results for styrene and vinyl–ester double bonds independently. The results of this work demonstrate that reaction temperature and resin composition significantly affect the cure behavior of vinyl–ester resins and provide insight into the development of the resulting network structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1572–1582, 2000

Electronic Structure Calculations on the Reaction of Vinyl Radical with Nitric Oxide

The potential energy surface of the [C2,H3,N,O] system in its electronic singlet ground state has been investigated using second-order Möller Plesset perturbation theory (MP2) and coupled-cluster theory CCSD(T) with the 6-311++G(d,p) basis set. Twenty-six (26) reactive intermediates relevant to the C2H3 + NO reaction channel have been identified. Methyl isocyanate 19 is calculated to be the most stable isomer. Two mechanisms (mechanisms A and B) are found to operate competitively toward CH2O formation, and they include reactive intermediates such as trans-nitrosoethylene 1, cis-nitrosoethylene 2, cyanomethanol 13, isocyanomethanol 14, and the cyclic oxazete 3. While the rate-limiting step in mechanism A is the decomposition of the cyclic oxazete 3, in mechanism B it corresponds to a 1,3-H shift in the trans-nitrosoethylene 1. The potential energies of both these critical transition structures are somewhat higher than the energy of the reactants C2H3 + NO, which explains the nonobservation of CH2O in the low-temperature pyrolysis of acetylene in the presence of NO. At low temperatures, the stabilized nitrosoethylenes 1 and 2 will be the dominant products, together with the cyclic compounds 3 and to a lesser extent, also 11. H2CO + HCN is predicted to be the predominant product at high temperatures. Conversion of NO to CO is kinetically unfavorable due to the high barrier involved in the isomerization of fulminate 15 to isofulminate 16. The most favorable mode of [2+2] cycloaddition between CH2O and HCN is the one wherein the carbon of the carbonyl group adds on to the nitrogen end of the cyanide.

Montmorillonite–palladium–copper catalyzed cross-coupling of methyl acrylate with aryl amines

Heck vinylation reactions of different anilines were performed with vinylacetate by using palladium chloride and copper nitrate intercalated montmorillonite K10 clay as catalyst. The substituted methylcinnamates were obtained in good yields without simultaneous side reaction to stilbenes.

ChemInform Abstract: Condensation Reactions of Vinyl and Ethyl Derivatives of 2‐Amino‐ and 2‐Formylimidazoles

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ruthenium-Catalyzed Regioselective Codimerization of Enol Acylates with 2-Substituted-1,3-butadienes

We have found a new ruthenium-catalyzed cooligomerization reaction of vinyl acylates with 2-substituted-1,3-butadienes, where very high yields as well as high regioselectivities were attained.

Pressure Effect on CH3 and C2H3 Cross-Radical Reactions

The effect of pressure on the cross-radical reactions of vinyl and methyl radicals has been investigated. These radicals were produced by excimer laser photolysis of methyl vinyl ketone (CH3COC2H3) at 193 nm. The reaction products were detected and analyzed using a sensitive gas chromatograph and mass spectrometer. The study covered a pressure range from about 0.28 kPa (2.1 Torr) to 27 kPa (200 Torr) at 298 K. The yield of propylene (C3H6), the cross-combination product of methyl and vinyl radicals, was compared to the yield of ethane (C2H6), the methyl radical combination product. At 27 kPa [C3H6]/[C2H6] = 1.28 was derived. This ratio was reduced to about 0.75 when the pressure was reduced to about 0.28 kPa. Kinetic modeling results indicated that the contribution of the combination reaction C2H3 + CH3 + M → C3H6 + M to the total cross-radical reactions is reduced from 78% at high pressures (27 kPa) to about 39% at low pressures (0.28 kPa). At low pressures an additional reaction channel, C2H3 + CH3 → C3H5 + H, becomes available, producing a host of allyl radical reaction products including 1,5-hexadiene, the allyl radical combination product. The observed 1,5-hexadiene is strong evidence for allyl radical formation at low pressures, presumably from the decomposition of the chemically activated C3H6. Macroscopic and microscopic modeling of product yields and their pressure dependencies were used to interpret the experimental observations. Results of master equation calculations using weak colliders and RRKM theory are in agreement with the observed pressure dependence of the combination reactions. It has been shown that the chemically activated species can undergo unimolecular processes that are competitive with collisional stabilization. The pressure dependence for the unimolecular steps appears as a pressure dependence of the combination/disproportionation ratio. The apparent pathological behavior in this unsaturated system is attributed to the formation of a stronger C−C bond as contrasted to the weaker C−C bond formed from combination of saturated hydrocarbon radicals. This C−C bond strength is sufficiently high for the chemically activated propylene, produced from the methyl and vinyl cross-combination reaction to cleave the allyl C−H bond or isomerize to cyclopropane.

Transformation of the carboxyl group adjacent to the (η 4-diene)Fe(CO) 3 moiety: a convenient route to (η 4-diene)Fe(CO) 3 complexes containing α,β- and β,γ-unsaturated carbonyl groups, and 1,3-dicarbonyl groups

Acyl halides adjacent to an (η 4-diene)Fe(CO) 3 moiety react with allylsilanes, vinylsilanes and enamines to give the corresponding allyl ketones, vinyl ketones and 1,3-diketones in high yields, respectively. The allylation reaction proceeds smoothly under neutral conditions without a Lewis acid as an activating agent, while the vinylation reaction takes place in the presence of a Lewis acid.

Heck reactions using water-soluble metal complexes in supercritical carbon dioxide

Heck vinylation reaction was studied using Pd(OAc) 2/ TPPTS catalyst system in supercritical carbon dioxide. The addition of co-solvents such as water and ethylene glycol significantly enhances the rate of reaction without leaching of Pd into the product phase. The reactants/ products can be easily separated from the catalyst by simple phase separation and the catalyst can be recycled.

A New Radical Vinylation Reaction of Iodides and Dithiocarbonates.

Heavy metals can be avoided with a new radical equivalent of the Heck reaction for aliphatic derivatives in which iodide and dithiocarbonate substituents are replaced by substituted vinyl groups [Eq. (1)]. The reaction enables the introduction of vinyl fragments into a variety of functionalized substrates.

Styrene hydration and stilbene isomerization in strong acid media. An excess acidity analysis

Rate constants obtained for the hydration of some ring-substituted styrenes, YC6H4CR=CH2 (R = H, CH3, CF3) (1-3), and for the isomerization of some cis-stilbenes substituted in both rings, YC6H4CH=CHC6H4Z (4), in aqueous H2SO4, D2SO4, and HClO4 media at 25°C and, in some cases, at other temperatures, have been subjected to an excess acidity analysis. Data obtained by different groups and in different media for the same substrates agree very well. The m‡ values obtained show that all the substrates react via the A-SE2 mechanism, rate-determining proton transfer to carbon; the transition state is late, with the proton transfer being about three-quarters complete. The reactivities of 1-3 in the aqueous standard state are obtained by extrapolation; they are 1:103:10-7, respectively. The stilbenes are relatively unreactive; log k0 values for compounds with substituents in the ring adjacent to the developing positive charge show a good correlation with σ+ with a large negative ρ+ value, but those for compounds with substituents in the other ring correlate with σ with a small negative ρ. Extrapolated log k0 values for 1 and 3 show a good correlation with σ+, but those for 2 correlate with neither σ+ nor σ, because the α-CH3 group twists the molecule and reduces the resonance interaction of ring substituents with the developing positive charge. On the other hand, this effect is not seen in 3, when the strongly deactivating α-CF3 group is present, meaning that the transition state is forced to be planar in this case. The activation parameters, solvent isotope effects, and excess acidity slope parameters m‡m* obtained in the analysis are tabulated and discussed. The parameters obtained for the parent styrenes 1 are very similar to those previously obtained for the phenylacetylenes YC6H4Ctriple bondCH, meaning that reactions with vinyl cation intermediates and reactions with benzyl cation intermediates can be quite similar. Key words: styrenes, stilbenes, hydration, excess acidity, LFER, mechanism.

Condensation reactions of vinyl and ethyl derivatives of 2-amino-and 2-formylimidazoles

New Schiff bases of 1-vinyl- and 1-ethyl-substituted imidazoles and benzimidazoles were synthesized. The condensation reactions of 2-amino- and 2-formylimidazoles with 2-aminobenzimidazoles are virtually independent of the nature of the substituent (CH=CH2 or Et) at position 1 of the heterocycle. The structures of the azomethines synthesized were established by1H NMR and IR spectroscopy.

The photochemical reaction of Si-substituted vinyl(ethynyl)- and diethynylsilanes with ethanethiol and its C-functional derivatives

The photoinitiated addition of ethanethiol and its derivatives XCH 2CH 2SH (X=HS, HO, (C 2H 5) 2N) to vinyl(ethynyl)- and diethynyl(diorganyl)silanes has been studied. The photochemical reaction of diethynyl (diorganyl)silanes with thiylation agents proceeds with participation of only one ethynyl group. In contrast to this, the double band of vinyl(ethynyl)diorganylsilanes takes part in photoinitiated thiylation.

ChemInform Abstract: Synthesis of β,β‐Bis(trimethylstannyl)styrenes by Organometal Trapping of Intermediates in the Aromatic Vinylation Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effects of temperature on cure kinetics and mechanical properties of vinyl-ester resins

The relationships among cure temperature, chemical kinetics, microstructure, and mechanical performance have been investigated for vinyl–ester resins. Fourier transform infrared spectroscopy was used to follow the reactions of vinyl–ester and styrene during isothermal curing of Dow Derakane 411-C-50 at 30 and 90°C. Reactivity ratios of vinyl–ester and styrene vinyl groups were evaluated using the copolymer composition equation. The results indicate that the ratio of vinyl–ester to styrene double bonds incorporated into the network is greater for 30 than for 90°C cure. Mechanical properties were obtained for systems subjected to isothermal cures at 30 and 90°C and postcured above ultimate Tg. The results show that the initial cure temperature significantly affects the mechanical behavior of vinyl–ester resin systems. In particular, values of strength and fracture toughness for postcured samples initially cured isothermally at 30°C are significantly higher than those obtained for samples cured isothermally at 90°C. Examination of fracture surfaces using atomic force microscopy revealed the existence of a nodular microstructure possessing characteristic nodule dimensions that are affected by the temperature of cure. Such features suggest the existence of phase separation during cure. A binary interaction model in conjunction with chemical kinetic data and estimated solubility parameters was used to evaluate enthalpic interactions between the growing polymer network and monomers of the vinyl–ester system. The results indicate that the interaction energy becomes increasingly endothermic as cure progresses and that this energy is affected by the temperature of cure through differences in copolymerization behavior. Hence, in addition to entropic factors, the changes in enthalpic contribution to the Gibbs free energy suggest that the probability of phase separation increases with extent of cure and that its onset is potentially affected by cure temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 725–744, 1999

Synthesis of β,β-Bis(trimethylstannyl)styrenes by Organometal Trapping of Intermediates in the Aromatic Vinylation Reactions

Synthesis of <i>β</i>,<i>β</i>-Bis(trimethylstannyl)styrenes by Organometal Trapping of Intermediates in the Aromatic Vinylation Reactions