Alkyl Vinyl Ethers Research Articles

Searching for zwitterionic intermediates in Hetero Diels–Alder reactions between methyl α,p-dinitrocinnamate and vinyl-alkyl ethers

DFT calculations indicate that reactions of methyl α,p-dinitrocinnamate with vinyl-alkyl ethers are of a polar nature, and zwitterionic structures may arise during their course. However, these zwitterions are beyond of cycloadditions paths. On the other hand, HDA reactions of addents carried out according to “two-stage one-step” cycloaddition mechanism. It should be also remarked, that the M062x functional overestimates activation energies.

Design of Benign Initiator for Living Cationic Polymerization of Vinyl Ethers: Facile in Situ Generation of Vinyl Ether–Hydrogen Halide Adducts and Subsequent Controlled Polymerization without a Lewis Acid Catalyst

A Lewis acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis acid catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...

Five-membered 2,3-dioxo heterocycles: XCVIII. [4 + 2]-cycloaddition of alkyl vinyl ethers to 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones. A new synthetic approach to heteroanalogs of 13(14→8)-abeo steroids

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones reacted with alkyl vinyl ethers according to the [4 + 2]-cycloaddition pattern with formation of substituted (1S*,16R*)- and (1R*,16R*)-16-alkoxy-14-aryl-3,15-dioxa-10-azatetracyclo[8.7.0.01,13.04,9]heptadeca-4,6,8,13-tetraene-2,11,12-triones. The structure of (1S*,16R*)-7-chloro-16-ethoxy-14-phenyl-3,15-dioxa-10-azatetracyclo[8.7.0.01,13.04,9]heptadeca-4,6,8,13-tetraene-2,11,12-trione was determined by X-ray analysis. A new synthetic approach was developed to heteroanalogs of 13(14→8)-abeo steroids, substituted 3,15-dioxa-10-azatetracyclo[8.7.0.01,13.04,9]heptadecanes.

Reactions of P(III) chlorides with aldehydes: I. Synthesis of primary intermediates of the reactions of aliphatic aldehydes with P(III) chlorides possessing electrophilic properties

An approach to investigation of reactions of electrophilic P(III) chlorides with aliphatic aldehydes is developed. Its essence is the removal of HCl impurity from chloride and catalytic blocking of electrophilic center of the carbonyl group. For these purposes nitrogen-containing organic bases and alkyl vinyl ethers are used. Three types of primary intermediates with the nearest P(III) environment POCl2, O2PCl, and O3P are synthesized. It is established that the stability of intermediates increases with the growing acceptor properties of substituents at P(III) and donor properties of the aldehyde fragment.

Selectively degradable alternating copolymers of isobutyl vinyl ether and plant-derived aldehydes with acyclic side chains: Effects of side group structures on copolymerization behaviors

Side group structures of aldehydes were demonstrated to have decisive effects on cationic copolymerizations with alkyl vinyl ether (VE). Alternating copolymerizations of isobutyl VE (IBVE) and plant-derived aldehydes with acyclic side chains such as trans-2,cis-6-nonadienal, trans-2-nonenal, and citral proceeded under appropriate reaction conditions with the EtSO3H/GaCl3 initiating system. In addition, some aldehydes copolymerized in a well-controlled fashion to yield alternating copolymers with controlled molecular weights and narrow molecular weight distributions. Quantitative and selective acid hydrolysis of the resulting alternating copolymers, based on the acetal structures in the main chains, was also achieved to give other conjugated aldehydes as nearly sole degradation products. Copolymerization results of IBVE and various plant-derived aldehydes with acyclic or cyclic side groups suggested that electron-donating ability and bulkiness of the side groups were most likely responsible for the alternating and/or controlled copolymerization behaviors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4684–4693

Concurrent Cationic Vinyl-Addition and Ring-Opening Copolymerization Using B(C6F5)3 as a Catalyst: Copolymerization of Vinyl Ethers and Isobutylene Oxide via Crossover Propagation Reactions

Alkyl vinyl ethers and isobutylene oxide were concurrently copolymerized through cationic vinyl addition and ring opening using B(C6F5)3 as a catalyst. NMR analyses and acid hydrolysis of the products demonstrated that the copolymerization successfully proceeded through crossover reactions between vinyl and cyclic monomers to yield multiblock-like copolymers. Appropriate catalyst and monomer combinations with suitable reactivities were key for copolymerization.

Fluorine detected 2D NMR experiments for the practical determination of size and sign of homonuclear F–F and heteronuclear C–F multiple bond J-coupling constants in multiple fluorinated compounds

The use of fluorine in molecules obtained from chemical synthesis has become increasingly important within the pharmaceutical and agricultural industry. NMR characterization of these compounds is of great value with respect to their structure elucidation, their screening in metabolomics investigations and binding studies. The favorable NMR properties of the fluorine nucleus make NMR with fluorine detection of great value in this respect. A suite of NMR 2D F–F- and F–C-correlation experiments with fluorine detection was applied to the assignment of resonances, nJCF- and nJFF-couplings as well as the determination of their size and sign. The utilization of this experiment suite was exemplarily demonstrated for a highly fluorinated vinyl alkyl ether. Especially F–C HSQC and J-scaled F–C HMBC experiments allowed determining the size of the J-couplings of this compound. The relative sign of its homo- and heteronuclear couplings was achieved by different combinations of 2D NMR experiments, including non-selective and F2-selective F–C XLOC, F2-selective F–C HMQC, and F–F COSY. The F2-one/two-site selective F–C XLOC versions were found highly useful, as they led to simplifications of the common E.COSY patterns and resulted in a higher confidence level of the assignment by using selective excitation. The combination of F2-one/two-site selective F–C XLOC experiments with a F2-one-site selective F–C HMQC experiment provided the signs of all nJCF- and nJFF-couplings in the vinyl moiety of the test compound. Other combinations of experiments were found useful as well for special purposes when focusing for example on homonuclear couplings a combination of F–F COSY-10 with a F2-one-site selective F–C HMQC could be used. The E.COSY patterns in the spectra demonstrated were analyzed by use of the spin-selective displacement vectors, and in case of the XLOC also by use of the DQ- and ZQ-displacement vectors. The variety of experiments presented shall contribute to facilitate the interpretation of F–C correlations as well as to open alternative pathways for the determination of size and signs of homo- and heteronuclear couplings of multiply fluorinated small molecules.

ChemInform Abstract: Five‐Membered 2,3‐Dioxoheterocycles. Part 87. [4 + 2]‐Cycloaddition of Alkyl Vinyl Ethers and 3,4‐Dihydro‐2H‐pyran to 4,5‐Diaroyl‐1H‐pyrrole‐2,3‐diones.

AbstractThe reactions of pyrrolediones (I) and (IV) with alkyl vinyl ethers (II) and dihydropyran (V) are studied, aiming at the investigation of the effect of the aroyl fragment in 1H‐pyrrole‐2,3‐diones.

ChemInform Abstract: Synthesis of Fused Uracils: Pyrano[2,3‐d]pyrimidines and 1,4‐Bis(pyrano[2,3‐d]pyrimidinyl)benzenes by Domino Knoevenagel/Diels—Alder Reactions.

AbstractNovel fused uracils (IV/V) and (VIII) are synthesized by domino Knoevenagel/Diels—Alder reaction between barbituric acids, aromatic aldehydes and alkyl vinyl ethers.

Kinetic Study of Gas-Phase Reactions of OH and NO3Radicals and O3with iso-Butyl andtert-Butyl Vinyl Ethers

Using a relative rate technique, kinetic studies on the gas-phase reactions of OH radicals, ozone, and NO(3) radicals with iso-butyl vinyl ether (iBVE) and tert-butyl vinyl ether (tBVE) have been performed in a 405 L Duran glass chamber at (298 ± 3) K and atmospheric pressure (750 ± 10 Torr) in synthetic air using in situ FTIR spectroscopy to monitor the reactants. The following rate coefficients (in units of cm(3) molecule(-1) s(-1)) have been obtained: (1.08 ± 0.23) × 10(-10) and (1.25 ± 0.32) × 10(-10) for the reactions of OH with iBVE and tBVE, respectively; (2.85 ± 0.62) × 10(-16) and (5.30 ± 1.07) × 10(-16) for the ozonolysis of iBVE and tBVE, respectively; and (1.99 ± 0.56) × 10(-12) and (4.81 ± 1.01) × 10(-12) for the reactions of NO(3) with iBVE and tBVE, respectively. The rate coefficients for the NO(3) reactions are first-time determinations. The measured rate coefficients are compared with estimates using current structure activity relationship (SAR) methods and the effects of the alkoxy group on the gas-phase reactivity of the alkyl vinyl ethers toward the oxidants are compared and discussed. In addition, estimates of the tropospheric lifetimes of iBVE and tBVE with respect to their reactions with OH, ozone, and NO(3) for typical OH radical, ozone, and NO(3) radical concentrations are made, and their relevance for the environmental fate of compounds is considered.

Five-membered 2,3-dioxoheterocycles: LXXXVII. [4+2]-cycloaddition of alkyl vinyl ethers and 3,4-dihydro-2H-pyran to 4,5-diaroyl-1 H-pyrrole-2,3-diones

1-Aryl-4,5-diaroyl-1H-pyrrole-2,3-diones react with alkyl vinyl ethers and 3,4-dihydro-2H-pyran affording 1,4-diaryl-7a-aroyl-6-ethoxy-7,7a-dihydropyrano[4,3-b]pyrrole-2,3(1H,6H)-diones and 1,4-diaryl-9baroyl-1,7,8,9,9a-hexahydro-5aH-pyrano[3′,2′:5,6]pyrano[4,3-b]-pyrrole-2,3-diones respectively.

Efficient syntheses of C20-carotene and crocetin (descrocetin) esters promoted by an acidic ionic liquid

Efficient syntheses of C20-carotene and crocetin or descrocetin esters from fumaraldehyde bis-dimethylacetal are described. The key steps of these syntheses are the reactions of fumaraldehyde and (2E,4E,6E)-octa-2,4,6-trienedial bis-dimethylacetals with alkyl vinyl or alkyl propenyl ethers promoted by the acidic ionic liquid, [emim][HSO4].

Rheology and Processing of Tetrafluoroethylene/Hexafluoropropylene Copolymers

Abstract The rheology and processing of tetrafluoroethylene/hexafluoropropylene (TFE/HFP) copolymers and TFE/HFP/per-fluoro(alkyl vinyl ether) (TFE/HFP/PAVE) terpolymers, also known as FEP polymers, are reviewed in this paper. Dynamic linear viscoelasticity and other fundamental rheological properties such as the critical molecular weight for the onset of entanglements, Mc, the zero-shear viscosity versus molecular weight relationship, dependence of rheology on thermal history and aspects of shear-induced crystallization are presented. The melt fracture and wall slip behavior of FEP resins is also discussed. Finally, possible processing aids that can be used in the extrusion of FEP resins in order to postpone melt fracture phenomena to higher flow rates are also discussed thoroughly.

ChemInform Abstract: Construction of Substituted Benzene Rings by Palladium‐Catalyzed Direct Cross‐Coupling of Olefins: A Rapid Synthetic Route to 1,4‐Naphthoquinone and Its Derivatives.

Ring the changes: the direct cross-coupling of electron-deficient 1,4-benzoquinone or its derivatives with electron-rich alkyl vinyl ethers proceeds in a tandem manner to produce substituted benzene rings with good selectivity and in good to excellent yields. The reaction has the potential for the rapid synthesis of diverse substituted benzene rings as it is not limited by substituent effects.

Simultaneous removal of CO2 and H2S from pressurized CO2–H2S–CH4 gas mixture using hollow fiber membrane contactors

In the present paper, the simultaneous removal of CO2 and H2S from their pressurized mixture with CH4 (5% CO2–2% H2S–93% CH4) using custom made membrane contactors equipped with micro-porous polymeric hollow fibers is described. Two types of commercial hollow fibers were employed and compared, i.e., expanded poly(tetrafluoroethylene) (ePTFE) and poly(tetrafluoroethylene-co-perfluorinated alkyl vinyl ether) (PFA). The feed gas mixture composition was 2% H2S, 5% CO2 in balance of CH4 to mimic the typical natural gas composition. Distilled water, aqueous sodium hydroxide and amine solutions of different concentrations were tested as absorption liquids to achieve the selective removal of the acid gases from the pressurized gas streams. The effect of pressure on the simultaneous CO2 and H2S absorption rates was investigated by the simultaneous pressurization of the absorption liquid and the feed gas (up to 50bar) and monitoring the residual acid gases in the exit stream. The obtained experimental results indicated that the simultaneous CO2 and H2S fluxes were enhanced by increasing the inlet gas pressure for both physical and chemical absorption solvents. Up to the authors’ best knowledge, this is the first report on (i) the experimental simultaneous removal of CO2 and H2S from pressurized gas streams using HFM contactors and absorption solvents up to 50bar and (ii) the utilization of PFA fibers in custom made high pressure-membrane modules. PFA fibers exhibited impressive higher fluxes (9–10 times) for CO2 and H2S than those obtained with the common ePTFE fibers which could be attributed in part to the associated higher mass transfer coefficient. The anticipated CO2/H2S flux ratio of 2.5 (which matches the ratio of their inlet concentrations in the feed gas) was obtained whenever the co-absorption was unhindered into absorption solvent of sufficient capacity, e.g., 2.0 M NaOH solution. Analysis of the mass transfer coefficients showed that while the overall mass transfer coefficients are determined by the liquid phase mass transfer coefficients at low pressures, gas phase mass transfer resistance contributes considerably to the overall resistance at high pressures.

ChemInform Abstract: An Expedient Synthesis of cis/trans‐1,3‐Disubstituted Cyclobutanols.

Abstract3‐Alkoxycyclobutanones such as (IV) are obtained from [2 + 2] cycloaddition of alkyl vinyl ether and chloroketene followed by hydrogenolytic dechlorination.

Construction of Substituted Benzene Rings by Palladium‐Catalyzed Direct Cross‐Coupling of Olefins: A Rapid Synthetic Route to 1,4‐Naphthoquinone and Its Derivatives

Ring the changes: the direct cross-coupling of electron-deficient 1,4-benzoquinone or its derivatives with electron-rich alkyl vinyl ethers proceeds in a tandem manner to produce substituted benzene rings with good selectivity and in good to excellent yields. The reaction has the potential for the rapid synthesis of diverse substituted benzene rings as it is not limited by substituent effects.

Competition between reaction and intramolecular energy redistribution in solution: observation and nature of nonstatistical dynamics in the ozonolysis of vinyl ethers.

Experimental product ratios in ozonolyses of alkyl vinyl ethers in solution do not fit with expectations based on statistical rate theories. The selectivity among cleavage pathways increases with the size of the alkyl group but to an extent that is far less than RRKM theory would predict. Trajectory studies account for the observed selectivities and support a mechanism involving a competition between cleavage of the primary ozonide and intramolecular vibrational energy redistribution. A statistical model is presented that assumes that RRKM theory holds for a molecular subset of the primary ozonides, allowing the rates of energy loss from the ozonides to be estimated from the observed product ratios.

DFT study of the gas‐phase thermal decomposition kinetics of 2‐ethoxypyridine into 2‐pyridone

AbstractThe mechanism of the gas‐phase elimination kinetics of 2‐ethoxypyridine has been studied through the electronic structure calculations using density functional methods: B3LYP/6‐31G(d,p), B3LYP/6‐31++G(d,p), B3PW91/6‐31G(d,p), B3PW91/6‐31++G(d,p), MPW1PW91/6‐31G(d,p), MPW1PW91/6‐31++G(d,p), PBEPBE/6‐31G(d,p), PBEPBE/6‐31++G(d,p), PBE1PBE1/6‐31G(d,p), and PBE1PBE1/6‐31++G(d,p). The elimination reaction of 2‐ethoxypyridine occurs through a six‐centered transition state geometry involving the pyridine nitrogen, the substituted carbon of the aromatic ring, the ethoxy oxygen, two carbons of the ethoxy group, and a hydrogen atom, which migrates from the ethoxy group to the nitrogen to give 2‐pyridone and ethylene. The reaction mechanism appears to occur with the participation of π‐electrons, similar to alkyl vinyl ether elimination reaction, with simultaneous ethylene formation and hydrogen migration to the pyridine nitrogen producing 2‐pyridone. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

ChemInform Abstract: Palladium‐Catalyzed Dimerization of Vinyl Ethers to Acetals.

AbstractThe dinuclear dicationic complex (I) catalyzes the dimerization of alkyl or silyl vinyl ethers to acetals as well as the cyclization of divinyl ethers to cyclic acetals.