Benzyl Vinyl Ether Research Articles

Thermally cross-linkable host materials for enabling solution-processed multilayer stacks in organic light-emitting devices

A thermally cross-linkable host material, i.e., two vinylbenzyl ether groups containing a carbazole derivative (DV-CBP), was developed for solution-processed multilayer organic light-emitting devices (OLEDs). DV-CBP was thermally cross-linked at styrene end-groups through curing at approximately 180°C in the absence of a polymerization initiator. This cross-linking reaction rendered the emissive layer insoluble and enabled the subsequent solution deposition of an upper electron-transporting layer. Furthermore, photoluminescence quantum efficiencies of the emissive layer were maintained at greater than 75% throughout the cross-linking reaction. A solution-processed small-molecule electron-transporting layer on top of the cross-linked emissive layer led to lower driving voltages and higher efficiencies in the OLEDs compared to those of a device with a vacuum-deposited Ca electrode on the emissive layer.

3+2] Cycloaddition of metal-containing azomethine ylides for highly efficient synthesis of mitosene skeleton

Efficient synthesis of tricyclic indole derivatives bearing a substituent at the 3-position of the indole nucleus was achieved by the [3+2] cycloaddition reaction of transition metal-containing azomethine ylides derived from N-( o-alkynylphenyl)imines with vinyl ethers. Third-row transition metal complexes, especially PtCl 2, turned out to be highly efficient for the reaction of internal alkynes and imidate substrates with wide generality. Moreover, as strong support for the reaction mechanism, the intermediate Pt–carbene complex was found to undergo intramolecular C–H bond insertion reaction to give tetracyclic indoline derivatives when benzyl vinyl ether was employed as a dipolarophile. This protocol provided a facile synthesis of highly functionalized tricyclic indole derivatives found as the basic skeleton of the mitosene family, such as mitomycin C.

ChemInform Abstract: A Stereoselective Synthesis of 2,6-Dideoxy-6,6,6-trifluoro-arabino-hexoses via an Asymmetric Diels-Alder Strategy.

The enantioselective syntheses of each enantiomer of ethyl 2,6-dideoxy-6,6,6-trifluoro-β-arabino-hexopyranoside (3) and of 2,6-dideoxy-6,6,6-trifluoro-arabino-hexose (4) are described. The key step in the approach is the inverse electron demand Lewis acid catalysed Diels–Alder reaction of the heterodiene (E)-1,1,1-trifluoro-4-[(1R)-1- phenylethoxy]but-3-en-2-one (5) and either ethyl vinyl ether (7a) or benzyl vinyl ether (7b). The titanium(IV) chloride catalysed cycloadditions at low temperature displayed high endo-selectivity and modest diastereofacial selectivity. Hydroboration of the mixture of the cis-cycloadducts (8a) afforded the separable diastereoisomers (9a) and (10a). Hydrogenolysis of (9a) gave ethyl 2,6-dideoxy-6,6,6-trifluoro-β-L-arabino-hexopyranoside (+)-(3), and of (10a) gave the corresponding D-glycoside (−)-(3). Similarly, hydroboration of the cis-cycloadducts (8b) gave the protected benzyl glycosides (9b) and (10b). Hydrogenolysis of each gave 2,6-dideoxy-6,6,6-trifluoro-L-arabino-hexopyranose (−)-(4) and the corresponding D-sugar (+)-(4) respectively. The absolute configurations of fluorinated carbohydrates (+)- and (−)-(3) were determined by comparison of their molar rotations with those of the parent glycosides. These assignments were confirmed by an X-ray crystallographic structure determination of the glycoside (9a).

Multifunctional Crosslinkable Iridium Complexes as Hole Transporting/Electron Blocking and Emitting Materials for Solution‐Processed Multilayer Organic Light‐Emitting Diodes

AbstractHere, a new series of crosslinkable heteroleptic iridium (III) complexes for use in solution processed phosphorescent organic light emitting diodes (OLEDs) is reported. These iridium compounds have the general formula of (PPZ‐VB)2Ir(CˆN), where PPZ‐VB is phenylpyrazole (PPZ) vinyl benzyl (VB) ether; and the CˆN ligands represent a family of four different cyclometallating ligands including 1‐phenylpyrazolyl (PPZ) (1), 2‐(4,6‐difluorophenyl)pyridyl (DFPPY) (2), 2‐(p‐tolyl)pyridyl (TPY) (3), and 2‐phenylquinolyl (PQ) (4). With the incorporation of two crosslinkable VB ether groups, these compounds can be fully crosslinked after heating at 180 °C for 30 min. The crosslinked films exhibit excellent solvent resistance and film smoothness which enables fabrication of high‐performance multilayer OLEDs by sequential solution processing of multiple layers. Furthermore, the photophysical properties of these compounds can be easily controlled by simply changing the cyclometallating CˆN ligand in order to tune the triplet energy within the range of 3.0–2.2 eV. This diversity makes these materials not only suitable for use in hole transporting and electron blocking but also as emissive layers of several colors. Therefore, these compounds are applied as effective materials for all‐solution processed OLEDs with (PPZ‐VB)2IrPPZ (1) acting as hole transporting and electron blocking layer and host material, as well as three other compounds, (PPZ‐VB)2IrDFPPY (2), (PPZ‐VB)2IrTPY(3), and (PPZ‐VB)2IrPQ(4), used as crosslinkable phosphorescent emitters.

Thermally Cross-Linkable Hole-Transporting Materials for Improving Hole Injection in Multilayer Blue-Emitting Phosphorescent Polymer Light-Emitting Diodes

One of the most challenging tasks in fabricating multilayer polymer light-emitting diodes (PLEDs) is to develop robust hole-transporting materials that possess matched energy level with indium tin oxide (ITO) anode and the highest occupied molecular orbital (HOMO) of light-emitting polymers to facilitate efficient hole injection and transport. In this article, a series of thermally cross-linkable 4,4′,4′′-tris(N-carbazolyl)triphenylamine (TCTA) derivatives have been synthesized to explore their function as efficient hole-transporting materials for blue-emitting electrophorphorescent devices. In particular, their excellent solvent resistance enables them to be used in the double hole-transporting layer (HTL) device configuration to facilitate cascade hole injection. The effects of cross-linking temperature and the functional group on the compatibility between two HTLs are investigated through optical and atomic force microscopy. When vinylbenzyl ether is used as the cross-linking group for TCTA, it shows t...

Trehalose‐based thermosetting resins. I. Synthesis and thermal properties of trehalose vinylbenzyl ether

AbstractTrehalose vinylbenzyl ether was synthesized from trehalose andp‐chloromethylstyrene (CMS) in DMSO in the presence of powdered NaOH. The structure of the product was characterized by IR and1H NMR spectroscopy. Degree of substitution (DS) on a trehalose unit calculated from the1H NMR spectrum varied from 2.4 to 3.2 by changing the feed ratio ofp‐chloromethylstyrene to trehalose. Thermal properties of the resin were analyzed by differential scanning calorimetry (DSC). DSC analysis revealed that the resin DS 2.4 has one exothermal peak at 132°C, whereas the resins DS 2.8 and 3.0 have two exothermal peaks. Furthermore, the resin DS 3.2 was found to have only one exothermal peak at 191°C. Dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA) revealed that the cured resin has one transition, implying a glass transition. Biodegradability was assayed by the BOD method, and several percent of the cured resin was found to be degraded with activated sludge for 50 days. Further degradation, however, was not observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 46–51, 2004

Regioselective Stille Coupling Reactions of 3,5‐Dibromo‐2‐pyrone with Various Aryl and Vinyl Stannanes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Regioselective Stille coupling reactions of 3,5-dibromo-2-pyrone with various aryl and vinyl stannanes

3,5-Dibromo-2-pyrone underwent facile regioselective Stille coupling reactions with aryl, heteroaryl and vinyl stannanes to produce various 3-substituted, 5-bromo-2-pyrones. Addition of a catalytic amount of CuI greatly increased the selectivity and chemical yield of the desired 3-aryl-5-bromo-2-pyrone. Second Stille coupling reactions on the resulting 3-aryl-2-pyrones gave rise to a series of potentially useful 2-pyrones with two different functionalities at C3 and C5 position in good to excellent isolated yields. 2-Pyrones with pyridyl groups at C3 position can undergo Lewis acid catalyzed Diels–Alder cycloaddition reactions with benzyl vinyl ether.

Complete pi-facial diastereoselectivity in Diels-Alder reactions of dissymmetric 2,4-cyclohexadienones.

[reaction: see text] The studies in the Diels-Alder reactions of 5-methoxy-masked o-benzoquinone (1a, R = OMe) and simple dissymmetric 2,4-cyclohexadienones 1b-e with methyl vinyl ketone, styrene, and benzyl vinyl ether are described. The dienones 1b-e reacted with dienophiles to form syn adducts (dienophile approach is syn to allylic methoxy group) exclusively.

Highly isotactic poly(vinyl alcohol). III: Heterogeneous cationic polymerization of tert-butyl vinyl ether

We studied the polymerization of tert-butyl vinyl ether (tBVE) and benzyl vinyl ether with heterogeneous catalysts, that is, modified Ziegler type (Vandenberg type) catalysts and metal sulfate–sulfuric acid complexes.Vandenberg type catalysts gave high molecular weight and highly isotactic poly(tBVE)s with relatively narrow molecular weight distribution at high temperature, and then the resultant poly(tBVE)s were converted into the stereoregular poly(vinyl alcohol)s (PVAs). With titanium based Vandenberg type catalyst, a relative high isotactic PVA, which has 52% triad isotacticity, was obtained from the poly(tBVE) polymerized at 30°C. It was found from NMR study that the content of the triad tacticity of PVAs derived from poly(tBVE) catalyzed by titanium based catalysts agreed with the value calculated from the chain-end control model (Bovey's model). This fact suggests that the steric structure of the adding monomer in this system is determined by same mechanism to homogeneous BF3 complexes catalysts system. On contrast to that, the metal sulfate–sulfuric acid complexes show significantly low activity to tBVE polymerization.

Inverse-electron-demand Diels–Alder reactions of masked o-benzoquinones with enol ethers and styrene

Regio- and stereoslective inverse-electron-demand Diels–Alder reactions of masked o-benzoquinones (MOBs) 1a– 1h derived from the corresponding 2-methoxyphenols 2a– 2h with benzyl vinyl ether, dihydrofuran and styrene to afford the highly functionalized bicyclo[2.2.2]octenone derivatives are described. The MOBs having electron-deficient substituents were found to undergo more facile Diels–Alder cycloadditions with these dienophiles. The electron-rich dienophile dihydropyran is not a suitable 2π-partner for MOBs. Attempts are made to explain the observed regiochemistry of these Diels–Alder cycloadditions in terms of frontier molecular orbital theory.

A Facile Synthesis of 2,6-Dideoxy 6,6,6-Trifluorinated Carbohydrate Analogues

The syntheses of 2,6-dideoxy-6,6,6-trifluoro-DL-arabino-hexose (4) and the corresponding glycoside, ethyl 2,6-dideoxy-6,6,6-trifluoro-DL-arabino-hexopyranoside (11), are described. The key step in the synthesis of (4) involved the Lewis acid catalysed hetero-Diels–Alder reactions of (E)-4-benzyloxy-1,1,1-trifluorobut-3-en-2-one and benzyl vinyl ether. Hydroboration of the resulting cycloadduct, and hydrogenylitic debenzylation gave (4) in a 59% overall yield. The ethyl glycoside (11) was prepared in a similar manner from ethyl vinyl ether. A single-crystal X-ray diffraction study confirmed the structural assignment of (11). The O-glycosides (17) and (18) were formed from the boron trifluoride etherate promoted reaction of the per-acetate of (4), i.e. (16), and 2-naphthol. However, a similar reaction between 5-hydroxy-1,4-dimethoxynaphthalene and (16) gave the disubstituted C-glycoside (19) in 52% yield.

Synthesis and Aqueous Solution Properties of Amphiphilic Diblock Copolymers Based on Methyl Triethylene Glycol Vinyl Ether and Benzyl Vinyl Ether

Water-soluble diblock copolymers of methyl triethylene glycol vinyl ether and benzyl vinyl ether were synthesized by living cationic polymerization, giving molecular weights in the range 13 400−17 300 and narrow molecular weight distributions (Mw/Mn = 1.18−1.28). The MTEGVE block length was fixed at 56 monomer units and the BzVE block length varied from 6 to 56 units. Aqueous solutions were studied by using dynamic light scattering and turbidimetry to determine the effect of block ratio on micellization and precipitation. Dynamic light scattering at room temperature in water revealed two intensity-average populations for all the copolymers, assigned as well-defined micelles and large aggregates. The hydrodynamic radii of the micelles ranged from 10.2 to 26.2 nm. Turbidimetry showed a cloud point of 83.5 °C for the MTEGVE homopolymer. The cloud points of the block copolymers decreased with increasing BzVE content and leveled off at higher BzVE contents. Selective removal of the benzyl group was achieved by catalytic hydrogenolysis, as a route to block copolymers with poly(vinyl alcohol) sequences. The maximum extent of deprotection was only 88%. Incomplete deprotection was attributed to the adsorption of the MTEGVE block onto the carbon support, thus blocking the catalyst sites.

Different Pathways in the Base-Promoted Isomerization of Benzyl Oxiranyl Ethers.

The base-promoted isomerization of benzyl oxiranyl ethers was investigated. In particular it was shown that the reaction may proceed toward two main regioisomeric products: a benzyl vinyl ether or a 2-aryl-3-(hydroxyalkyl)oxetane, depending on subtle variations in the substitution on the phenyl ring. Disubstituted oxetanes were obtained in a stereoselective manner, thus providing a good entry to this class of synthetically useful compounds.

Lewis Acid-Promoted, Stereocontrolled, Gram Scale, Diels-Alder Cycloadditions of Electronically Matched 2-Pyrones and Vinyl Ethers: The Critical Importance of Molecular Sieves and the Temperature of Titanium Coordination with the Pyrone.

(R)-(+)-Binol-titanium coordinates with commercial methyl 2-pyrone-3-carboxylate and promotes mild, highly enantiocontrolled Diels-Alder cycloadditions with electron-rich vinyl ether CH(2)=CHOCH(2)-1-naphthyl and vinyl silyl ether CH(2)=CHOSiMe(2)Bu-t leading to valuable 1alpha,25-dihydroxyvitamin D(3) (calcitriol) intermediate (-)-2. Unexpectedly, two subtle variables were found to be critical for obtaining reproducibly over 90% enantioselectivities in gram scale cycloadditions: (1) the moisture content (15-17% is best) of the molecular sieves used to prepare the binol-titanium complex according to the Mikami protocol and (2) the temperature (50 degrees C is best) at which the pyrone ester is mixed with the binol-titanium complex. Unsubstituted 2-pyrone undergoes ytterbium-promoted, high-pressure, regioselective, and stereoselective Diels-Alder cycloaddition with benzyl vinyl ether to form versatile bicyclic lactone (+/-)-4 on gram scale.

Formal [1,3] rearrangement of 2-furylmethyl and 2-thienylmethyl vinyl ethers

Benzyl and naphthylmethyl vinyl ethers are inert in LPDE medium, whereas hetcroaromntic methyl vinyl ethers, viz., 2-furyl and 2-thicnylmelhyl vinyl ethers undergo formal [1,3] rearrangement in LPDE medium.

Monodisperse polymer beads as packing material for high‐performance liquid chromatography. Preparation of macroporous poly(2,3‐epoxypropyl vinylbenzyl ether‐co‐divinylbenzene) beads, their properties, and application to HPLC separations

AbstractIn search for HPLC separation media with new surface chemistries, a styrene‐based monomer, 2,3‐epoxypropyl vinylbenzyl ether, containing reactive epoxide groups has been syn‐thesized and copolymerized with divinylbenzene in a suspension polymerization. The process involves the use of size monodisperse particles that are swollen with monomer and then polymerized in the presence of a porogenic diluent consisting of a mixture of 4‐methyl‐2‐pentanol and octane. The effect of concentration of divinylbenzene on the pore size dis‐tribution and the specific surface area of the resulting uniformly sized porous poly(2,3‐epoxypropyl vinylbenzyl ether‐co‐divinylbenzene) beads has been studied. The epoxide groups of the copolymer have been hydrolyzed and the beads used for reversed‐phase chro‐matography of both small molecules and proteins to show the effect of hydrophobicity of the matrix on the separation properties. Reversed‐phase chromatography of alkylbenzenes follows the expected pattern while for proteins the hydrolyzed beads with the highest content of the crosslinking monomer exhibit a remarkable deviation from the predicted retention characteristics. © 1995 John Wiley & Sons, Inc.

Synthesis of poly(vinyl alcohol)s with narrow molecular weight distribution from poly(benzyl vinyl ether) precursors

A series of poly(benzyl vinyl ether)s of low molecular weight (5000 to 15000 g mol-1) and narrow molecular distribution (\(\overline M _w /\overline M _n< 1.20\)) have been synthesisedvia the cationic polymerisation of benzyl vinyl ether. Acetylation with acetic anhydride/tin (IV) chloride leads to poly(vinyl acetate), which can be hydrolysed to near-monodisperse water-soluble poly(vinyl alcohol) with an isotacticity of approximately 47%. This polymer was re-acetylated and its molecular weight distribution assessed to confirm that hydrolysis gives minimal chain scission.

Living Cationic Polymerization of Benzyl Vinyl Ether and Its Block Copolymers with Narrow Molecular Weight Distribution

The living cationic polymerization of benzyl vinyl ether (BnVE) was achieved by the CH3CH(OiBu)OCOCH3(1)/EtAlCl2 initiating system in the presence of added bases. The effects of polymerization temperature and solvent were investigated in detail. Polymerizations in the presence of ethyl acetate at below 0°C in a non-polar solvent (toluene or CCl4) gave living polymers with a narrow molecular weight distribution (MWD) (M̅w/M̅n∼1.1). The M̅n of the polymers increased in proportion to monomer conversion. The obtained living polymer was rich in isotacticity (∼80%) by 1H NMR analysis. Fast living polymerization also occurred in the presence of methyl chloroacetate to synthesize higher molecular weight poly(BnVE) than >M̅n=105. Block copolymers were prepared by the sequential living polymerization of BnVE and isobutyl vinyl ether. Debenzylation of poly(BnVE) and its block copolymers was achieved by two methods [(A) HBr in toluene and (B) Na in liq. NH3] to give PVA and its block copolymers with a narrow MWD.

Synthèse de polymères hautement fluorés amorphes et à Tg élevées: copolymérisation de maléimides fluorés avec des éthers vinyliques

We have prepared and characterized (by 1H NMR and MS methods) N-4-(2'- F-hexylethoxy)phenylmaleimide and N-4-(2'- F-hexylethylthio)phenylmaleimide. The behaviour of these fluorinated maleimides (FM) towards various vinyl ethers (2-chloroethylvinyl ether, benzylvinyl ether) in radical copolymerization has been studied. Generally, maleimides and vinyl ethers lead to alternated copolymers but, in this case, the copolymer was not alternated. The thermal behaviour of the copolymers has been evaluated and their thermal decomposition explained.