Novel cationically polymerizable propenyl and vinyl ethers derived from renewable sources

The preparation of several novel mono- and dipropenyl and divinyl ethers derived from renewable starting materials is described using simple, straightforward synthetic methods. Utilizing real-time infrared spectroscopy, the reactivity of the monomers in photoinitiated cationic polymerization was studied employing diaryliodonium and triarylsulfonium salts as photoinitiators. The monomers were shown to undergo very rapid cationic photopolymerization. © 1994 John Wiley & Sons, Inc.     

Relative thermodynamic stabilities of isomeric 1,2-dialkoxyethenes

The relative thermodynamic stabilities of the geometrical isomers of a number of 1,2-dialkoxyethenes have been determined by chemical equilibration in the neat liquid and in 1,4-dioxane solution with mercuric acetate as catalyst. From the variation of the value of the equilibrium constant with temperature, the thermodynamic parameters G , H , and S of theE Z isomerization were evaluated. In all cases theZ isomer proved to be thermodynamically the more stable species, its favor increasing with the bulkiness of the alkoxy groups. The thermodynamic data obtained for theEZ isomerization of 1,2-dimethoxyethene differ significantly from those reported in the literature. An attempt to correlate the experimental thermodynamic data with MM2 calculations for the title compounds as well as for 1,2-dimethoxypropenes is presented.     

Propenyl ethers. I. The synthesis of propenyl ether monomers

A variety of mono-, di-, and multifunctional propenyl ethers were readily prepared in high yields by the condensation of alcohols with allyl halides followed by the base or transition metal-catalyzed rearrangement of the corresponding allyl ethers. Their straightforward synthesis and high reactivity in cationic UV curing make these monomers highly attractive for a variety of applications. The successful photopolymerization of these monomers has required the synthesis of specially tailored onium salt photoinitiators. © 1993 John Wiley & Sons, Inc.     

Relative thermodynamic stabilities of 2-substituted 4-methylene-1,3-dioxolanes and 4-methyl-1,3-dioxoles

The relative thermodynamic stabilities of 24 pairs of carbon-carbon double-bondexo-endo isomeric 2-substituted 4-methylene-1,3-dioxolanes (a) and 4-methyl-1,3-dioxoles (b) have been determined by base-catalyzed chemical equilibration in DMSO solution. In all cases, theendo isomer (b) is the favored species at thermodynamic equilibrium. A single alkyl substitutent on C-2 gives only a negligible contribution to the relative stability of the isomeric forms, but the presence of two alkyl groups on C-2 increases the relative stability of theendo isomer by 2–3 kL mol^–1. A still higher effect in favor of theendo isomer is produced by introduction of a single alkoxy group on C-2; this effect is further slightly accentuated by 2,2-dialkoxy substitution at C-2. The origin of the favorable effect of 2-alkoxy substitution on the relative stability of theendo isomer is not clear, but it seems to arise from an unexpected stability of theendo isomer rather than from an enhanced destabilization of theexo form.     

Stereoselective synthesis of functionalized vinyl ethers from allyl bromides activated by triethylamine

An efficient coupling reaction of allyl bromides with various alcohols as nucleophiles activated by triethylamine, leading to functionalized vinyl ethers in good yields and with full stereoselectivity.     

Anionic polymerization of propylene oxide: Isomerization of allyl ether to propenyl ether end groups

The isomerization of allyl ether to propenyl ether end group in anionically-polymerized poly (propylene oxide) was monitored by ¹H NMR spectroscopy. It was confirmed that the reaction followed a simple second-order rate law: ?d[allyl]dt = k₂[allyl] [O^?]. Values of k₂ determined over the 90–130°C temperature range, indicated an activation energy of 116 kJ mol^?1. © 1994 John Wiley & Sons, Inc.     

Propenyl ethers. III. Study of the photoinitiated cationic polymerization of propenyl ether monomers

The effects of photoinitiator structure and variations in the experimental parameters on the rate and extent of the photoinitiated cationic polymerization of propenyl ether monomers were studied. It was found that the photoinitiators can be divided into two classes: those which exhibit an induction period and those which do not. It was demonstrated that in those propenyl ether polymerizations using iodonium salts and certain sulfonium salts which do not have an induction period, a free radical chain-induced decomposition of the onium salt takes place. The reactivity of a particular onium salt photoinitiator was shown to be related to its reduction potential. It was also shown that the structure of the monomer plays a major role in the free radical induced decomposition reaction. © 1993 John Wiley & Sons, Inc.     

Transition metal-catalyzed tandem isomerization and cationic polymerization of allyl ethers. II. Structural and mechanistic studies

In the presence of organosilanes, dicobalt octacarbonyl catalyzes the polymerization of alkyl allyl ethers to give high molecular weight polymers. This article reports the results of a detailed mechanistic study of this new polymerization reaction. The evidence obtained in this study supports a stepwise process involving first, the reaction of dicobalt octacarbonyl with an organosilane to form HCo(CO)₄ and R₃SiCo(CO)₄. In subsequent steps, HCo(CO)₄ isomerizes the allyl ether to a 1-propenyl ether and then this compound is polymerized by the formal transfer of a silyl cation from R₃SiCo(CO)₄. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1985–1997, 1997     

A facile cleavage of allyl ethers on solid phase

A simple and efficient protocol for the cleavage of allyl ethers on solid phase using a palladium(0)-catalyzed allyl transfer reaction is reported.     

Relative thermodynamic stabilities of isomeric alkyl allyl and alkyl (Z)-propenyl ethers

The relative thermodynamic stabilities of ten allyl ethers (ROCH₂CH=CH₂) and the corresponding isomeric (Z)-propenyl ethers (where R is an alkyl group, or a methoxysubstituted alkyl group) have been determined by chemical equilibration in DMSO solution with t-BuOK as catalyst. From the variation of the equilibrium constant with temperature, the values of the thermodynamic parameters ΔGΘ, ΔHΘ and ΔSΘ of isomerization at 298.15 K were evaluated. The propenyl ethers are highly favored at equilibrium, the values of both ΔGΘ and ΔHΘ for the allyl → propenyl reaction being ca. −18 to −25 kJ mol⁻¹. The favor of the propenyl ethers is increased by bulky alkyl substituents, and decreased by methoxy-substituted alkyl groups. In most cases the entropy contribution is negligible; however, for R = (MeO)₂CH and R = (MeO)₃C the values of ΔSΘ are ca. −5 J K⁻¹ mol⁻¹.     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

Radical alternating copolymerization of vinyl ethers

New alternating equimolar copolymers of electrophilic trisubstituted ethylenes, methyl 3-phenyl-2-cyanopropenoate and 2-phenyl-1,1-dicyanoethene, with ethyl, n-butyl, i-butyl, t-butyl, 2-chloroethyl, and phenyl vinyl ethers were prepared by free radical initiation. Chemical compositions of the copolymers are 1 : 1 in broad ranges of monomer ratios. The copolymerization rate of both electrophilic monomers with the vinyl ethers increase in the series 2-chloroethyl > ethyl > phenyl > n-butyl > i-butyl > t-butyl. These variations in the reactivity of the vinyl ethers are discussed in terms of their preferred conformations in donor-acceptor complexes with electrophilic trisubstituted ethylenes. © 1993 John Wiley & Sons, Inc.     

F-alkylation of bis(allyl) polyoxyethylene ethers

Bis(3-F-alkylallyl) polyoxyethylene ethers were obtained via radical addition of F-alkyl iodides on bis(allyl) ethers CH₂CH(CH₂OCH₂)_nCHCH₂ followed by 1,8-diazabicyclo[5.4.0]undec-7-ne (DBU) dehydrohalogenation.     

Novel photocurable monomers: The synthesis of difunctional vinyl ethers with a phosphonate group and difunctional 1‐propenyl ethers with a phosphonate group and their photoinitiated cationic polymerization

Phosphorus‐containing vinyl ether monomers and 1‐propenyl ether monomers were prepared by the regioselective addition reaction of glycidyl vinyl ether (GVE) or 1‐propenyl glycidyl ether with diaryl phosphonates with quaternary onium salts as catalysts. The reaction of GVE with bis(4‐chlorophenyl) phenylphosphonate gave bis[1‐(4‐chlorophenoxy methyl)‐2‐(vinyloxy)ethyl]phenylphosphonate in a 68% yield. The structures of the resulting phosphorus‐containing vinyl ether monomers and 1‐propenyl ether monomers were confirmed by IR and ¹H NMR spectra and elemental analysis. Photoinitiated cationic polymerizations of the resulting phosphorus‐containing vinyl ether monomers and 1‐propenyl ether monomers were investigated with photoacid generators. The polymerization of vinyl ether groups and 1‐propenyl ether groups of the obtained monomers proceeded very smoothly with a sulfonium‐type cationic photoinitiator, bis[4‐(diphenylsulfonio)phenyl]sulfide‐bis(hexafluorophosphate), upon UV irradiation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3105–3115, 2005     

Synthesis and Lewis acid catalyzed Claisen rearrangement of 2-(1,3-oxazolin-2-yl)-substituted allyl vinyl ethers

Allyl vinyl ethers containing an acceptor function in the 2-position are useful substrates for the Lewis acid-catalyzed Claisen rearrangement. The first synthesis of acyclic 2-(1,3-oxazolin-2-yl)-substituted allyl vinyl ethers is reported. The Lewis acid catalyzed Claisen rearrangement of these allyl vinyl ethers afforded the rearrangement products with low to moderate diastereo- and enantioselectivity. The catalyzed rearrangement of chiral allyl vinyl ethers was investigated. The combination of substrate- and catalyst-induced diastereoselectivity led to unexpected and unprecedented results.     

Dicobalt octacarbonyl-catalyzed cationic polymerization of allylic and enolic ethers

In the presence of silanes bearing Si H groups, dicobalt octacarbonyl [Co₂(CO)₈] efficiently catalyzes the cationic polymerization of a wide variety of enol ether and other related monomers including vinyl ethers, 1-propenyl ethers, 1-butenyl ethers, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, ketene acetals, and allene ethers. In addition, this catalyst system is also effective for the polymerization of complimentary allylic and propargylic ethers by a process involving tandem isomerization and cationic polymerization. This latter process occurs by a stepwise mechanism in which the allylic or propargylic ether is first isomerized, respectively, to the corresponding enol ether or allenic ether and then this latter compound is rapidly cationically polymerized in the presence of the catalyst. In accord with this mechanism, it has been shown that the structure of the polymers prepared from related enol and allyl ethers using the above catalyst system are identical. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1579–1591, 1997     

Interaction of epoxy and vinyl ethers during photoinitiated cationic polymerization

A kinetic study of the independent and simultaneous photoinitiated cationic polymerization of a number of epoxide and vinyl (enol) ether monomer pairs was conducted. The results show that, although no appreciable copolymerization takes place, these monomers undergo complex interactions with one another. These interactions are highly dependent on the epoxide monomer employed. In all cases, the rate of epoxide ring-opening polymerization is accelerated, whereas that of the vinyl ether is depressed. When highly reactive cycloaliphatic epoxides are subjected to photoinitiated cationic polymerization in the presence of vinyl ethers, the two polymerizations proceed in a sequential fashion, with the vinyl ether polymerization taking place after the epoxide polymerization is essentially complete. A mechanism involving an equilibration between alkoxy-carbenium and oxonium ions has been proposed to explain the results. In addition, the free-radical-induced decomposition of the diaryliodonium salt photoinitiator also takes place, leading to a decrease in the induction period. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4007–4018, 1999     

Vibrational spectra and thermodynamic functions of allyl acetate

Raman spectrum of allyl acetate molecule has been photographed in liquid phase using 4358 ? line of mercury arc as the exciting line. Infrared absorption spectrum of the molecule has been recorded in liquid phase in the frequency range 200–4000 cm⁻¹. Both the spectra have been analysed to identify the fundamental frequencies. AssumingC _s symmetry, the observed fundamental frequencies have been assigned to various modes of vibration and compared with the frequencies of allyl halides and acetic acid. On the basis of present assignments of fundamental vibrational frequencies and assumed approximate structural parameters of the molecule, thermodynamic functions have been computed.