Comparison of AlEt2Cl and ZnCl2 supported on silica gel as catalysts of Diels-Alder reactions. Influence of the nature of the dienophile

Non-modified silica gel, silica gel treated with AlEt₂Cl, and ZnCl₂ supported on silica gel are tested as catalysts in the Diels-Alder reactions of cyclopentadiene (1) with methyl acrylate (2a), (-) -menthyl acrylate (2b) and acrylonitrile (2c). In general, supported catalysts are more efficient than non-modified silica gel. Two different kinds of silica gel are tested and the amount of aluminium incorporated when they are treated with AlEt₂Cl changes from one to another, which influences the chemical yield but not the selectivity of the reactions. In general, aluminium catalysts are more efficient than ZnCl₂-supported ones in the reactions of acrylates, but the latter solid is a better catalyst in the reactions of acrylonitrile (2c). Differences in acid strength and hardness of the catalytic sites are invoked to account for these results.     

Ring-opening polymerization of various oxirane derivatives using organotin phosphate condensate; Selective synthesis of the polyether containing oxirane ring in the side chain

Ring-opening polymerization (ROP) of various oxirane derivatives of the type, 2,2-R¹,R²-CCH₂O [R¹ = H (1), CH₃ (2); R² = CH₃ (a), CH₂Cl (b), CH₂OCH₃ (c)], using organotin phosphate (Bu₂SnO-Bu₃PO₄) condensate has been explored. The ROP of monosubstituted oxiranes (1a-c) afforded ring-opened polymers in high yields (1a, 1c = 99% and 1b = 69%); the resultant polymers from monomers 1a and 1b possessed high molecular weights (M_n = 9.49 × 10⁴, 10.60 × 10⁴, respectively). In contrast, both polymer yields and molecular weights for resultant polymers in the polymerization of disubstituted oxiranes (2a-c) were considerably lower than those in the polymerization of monosubstituted monomers (1a-c). ROP of glycidyl 2-methylglycidyl ether (3) possessing two oxirane groups with different reactivity was thus conducted by organotin catalyst; the high molecular weight polyether (M_n = 9.17 × 10⁴) containing oxirane ring in the side chain has successfully been obtained in moderate yield.     

Hydroboration copolymerization

Summary Organoboron copolymers were prepared by polyaddition of diene mixture or diene/diyne mixture, respectively, with thexylborane (1). When a mixture of dienes such as 1,2-diallyloxyethane (2a) and p-diallylbenzene (2b) was polymerized with 1, the peaks in GPC using both UV and RI detectors were shifted to higher molecular weight regions with the increase of the amount of 1. The molecular weight distribution of the copolymer obtained by this method indicated clear difference from that of a mixture of two homopolymers. On the other hand, when the poymerization between 1 and 1,7-octadiene (2c) was carried out in the presence of a trace amount of 1,7-octadiyne (4), the molecular weights of organoboron polymers were found to be increased when the ratio of 4/2c was increased.     

Synthesis, Properties, and Functionalization of Poly(ferrocenylsilane)s with Chloroalkyl Side Chains

A series of poly(ferrocenylsilane)s containing chloroalkyl side chains of increasing length is reported. By reacting fcLi₂· tmeda with Cl₂SiMeR, the corresponding [1]ferrocenophanes were prepared (2a, R=CH₂Cl; 2b, R=CH₂CH₂Cl; and 2c, R=CH₂CH₂CH₂Cl). Transition metal-catalyzed or thermal ring-opening polymerization (ROP) of these monomers yielded the polyferrocenes 3a, 3b, and 3c. The chlorine substituents of polymers 3a and 3b were unreactive toward nucleophilic substitution. In contast, polymer 3c could be reacted with 4-dimethylaminopyridine in DMF to afford the water-soluble poly(ferrocenylsilane) 4. This represents a new method for the preparation of water-soluble polyferrocenes.     

Polymerization of Methacrylates Containing Cationic Cyclopentadienyliron Moieties

A novel approach to the synthesis of polymethacrylates containing cationic cyclopentadienyliron moieties pendent to their side chains was accomplished via the use of -coordinated organoiron complexes. The complexed methacrylates were polymerized in the presence of AIBN to give soluble organoiron polymethacrylates (6a and 6b, 10, 14a and 14b) in 80–90% yields. Photolytic demetallation of the organoiron polymers allowed for the isolation of their organic analogues (7a and 7b, 11, 15a and 15b) whose weight average molecular weights ranged from 48,500 to 68,300.     

Synthesis and derivatization of angular 3-chloro-3-chlorosulfenyl naphtho[1,2-b]pyran(4H)-4-ones with evaluation of antiviral activity

Angular 2,3-dihydronaphtho[1,2-b]pyran(4H)-4-ones 1a,b react with an excess of thionyl chloride to give the α-chlorosulfenyl chlorides 2a,b, which are reduced by iodide ion to give the corresponding 1,3,4-oxadithiino derivatives 3a,b. However, the aducts 4a,b and 5a,b were obtained by reduced 2a,b with iodide ion in the presence of 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene, respectively. Direct oxidation of 2a,b afford 3,3-dichloronaphthopyran-4-ones 6a,b, whilst conversion to the sulfenamides 7a,b prior to oxidation provides 3-chloronaphthopyranones 8a,b. While α-chloro β-oxo sulfenyl chlorides 2a,b undergo straight forward substitution with 1-methylpiperazine and with potassium cyanide to give 9a,b and 10a,b, respectively. Some of the prepared products were selected and tested for their antiviral activity against herpes simplex virus type-1 (HSV-1). Plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with test compounds. Compound 5a showed moderate effect against HSV-1.     

Synthesis and characterization of poly(meth)acrylates containing tricyanocyclopropane ring for piezoelectric applications

Summary p-(2,2,3-Tricyano-3-carbomethoxycyclopropyl)phenoxyethyl acrylate (5a) and p-(2,2,3-tricyano-3-carbomethoxycyclopropyl)phynoxyethyl methacrylate (5b) were prepared by the reactions of bromomalononitrile with methyl p-(2-acryloyloxyethoxy)benzylidene-cyanoacetate (4a) and methyl p-(2-methacryloyloxyethoxy)benzylidenecyanoacetate (4b), respectively. Monomers 5a and 5b were polymerized with free-radical initiators to obtain the polymers with multicyanocyclopropane functionalities in the pendant group. The resulting polymers 6a and 6b were soluble in acetone and the inherent viscosities were in the range of 0.20–0.25 dL/g. Solution-cast films showed T _g values in the range of 130–150°C and piezoelectric coeffcients (d₃₁) of the poled films were 1.5–1.6 pC/N, which are acceptable for piezoelectric device applications. Received: 28 April 2000/Accepted: 26 June 2000     

Polymerization of cyclic monomers 9. Synthesis and radical polymerization of spirocyclic 2-vinylcyclopropanes

Summary 6,6-Diethyl- (1a) and 6-methyl-6-propyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1b) were synthesized by the acetalization of 2-vinylcyclopropane-1,1-dicarboxylic acid with 2- or 3-pentanone. The new monomers were characterized by IR, ¹H NMR and ¹³C NMR spectroscopy. The radical polymerization of the monomers 1a and 1b, in addition of 6,6-methyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1c) and (exo/endo)-7-ethoxycarbonyl-2-oxo-7-vinyl-bicyclo[4.1.0]heptane (1d), was carried out in bulk with 2,2`-azoisobutyronitrile (AIBN) as the initiator. The polymer yield with 1d was only low. The polymerization of the monomers 1a and 1c resulted in cross-linked polymers, whereas in case of the polymerization of monomer 1b soluble polymers in a high yield were obtained. Received: 17 February 1999/Revised version: 7 July 1999/Accepted: 7 July 1999     

Radical polymerization of (phenylethynyl)styrenes and characterization of poly(phenylethynyl)styrenes as a thermally curable material

Summary The radical polymerizations of 2-, 3-, and 4-(phenylethynyl)styrenes (1a–c) and the copolymerizations of 1a–c (M₁) with styrene (M₂) were carried out using AIBN as the initiator in toluene at 60°C. The number-average molecular weights (M _ns) were extremely low for poly(2-phenylethynylstyrene) (2a) and poly[(phenylethynyl)styrene-co-styrene] (3a), and increased in the order of 2a, 3a << 2b, 3b < 2c, 3c. Monomer reactivity ratios were determined as r ₁= 1.80 and r ₂= 0.51 for 1a, r ₁= 1.72 and r ₂= 0.53 for 1b, and r ₁= 3.17 and r ₂= 0.24 for 1c. Polymers 2a–c and 3a–c underwent an exothermic reaction at elevated temperature to form organic solvent-insoluble polymers. Although the decomposition of 2a was observed from 200°C, 2b and 2c exhibited a high heat-resistance property in both nitrogen and air atmospheres, in particular, 2b showed no significant weight loss below 450°C. Received: 28 January 1998/Accepted: 5 March 1998     

Synthesis and gas permeability of poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneethynylene)s having bulky alkoxy or alkyl groups

Dipropynylbenzene with branched alkoxy and alkyl groups [CH₃C≡CRC₆H₂RC≡CCH₃, R = 2-methylpropoxy (1a), 3-methylbutoxy (1b), 4-methylpentoxy (1c), cyclohexylmethoxy (1d), 2-ethylhexoxy (1e), 2-octoxy (1f), 2-ethylhexyl (1g), and 2-octyl (1h)] were polymerized with Mo(CO)₆ in the presence of 4-(trifluoromethyl)phenyl to afford poly(2,5-di(alkoxy or alkyl)-p-phenyleneethynylene)s (2a–h). Polymer 2a was insoluble in any solvents, but the other polymers (2b–h) were soluble in common organic solvents. The polymers with relatively long side chains (2e–h) had high molecular weight over 1.6 × 10⁴ and gave free-standing membranes by solution-casting method. The densities of membranes of 2e–h were 0.914–0.998, and their fractional-free volume values were relatively large (0.094–0.158). The oxygen permeability coefficients of membranes of 2e–h were 18.4, 12.7, 4.85, and 19.3 barrers, respectively. It was found that poly(p-phenyleneethynylene) with 2-octyl side groups, which have the branch at the nearest position from main chain, exhibited the highest gas permeability.     

Synthesis and Polymerization of Novel Quinone Methide Ketals

Summary Novel quinone methide ketals, 8-[ 1'-cyano-1'-(ethoxycarbonyl)methylene]-l,4-dioxaspiro[4.5]deca-6,9-diene (1a) and 8-(1',l'-dicyanomethy1ene)-1,4-dioxaspiro[4.5]deca-6,9-diene (1b), were synthesized, and their polymerization behavior was investigated. Polymerizations of 1a and 1b initiated with BPO and BF₃·Et₂O gave corresponding novel ring-opening polymers, but no polymerization with BuLi. Copolymerization of 1a with St in the presence of AIBN at 60 °C gave the monomer reactivity ratios r₁(1a) = 0.50 ± 0.1 and r₂(St) = 0.1 ± 0.02, and Q and e values of 1a were 2.46 and +0.93, indicating that 1a is a highly conjugative, electron-accepting monomer. Homopolymers of 1a and 1b had better thermal stability than that of 7-cyano-7-(ethoxycarbonyl)- 1,4-benzoquinone methide. Received 23 January 2003/Revised version 28 February 2003/ Accepted 1 March 2003 Correspondence to Takahito Itoh     

Synthesis and properties of new AB-type semi-crystalline poly(ether imide)s

Summary Two AB-type poly(ether imide)s were prepared by one-pot polyimidization in N-methyl-2-pyrrolidone(NMP)/pyridine or N,N-dimethylacetamide(DMAc)/Et₃N solution in the presence of triphenylphosphite(TPP) activator. The polymers were obtained with inherent viscosities of 1.16(5a) and 0.54(5b) dL/g and were highly thermostable up to at least 552°C with 5% weight loss. The polymers showed chemical resistance against chloroform even at higher temperature but could readily be dissolved in m-cresol and concentrated sulfuric acid. Wide-angle X-ray diffractograms revealed that the polymers were semi-crystalline. Received: 15 July 1999/Revised version: 30 July 1999/Accepted: 2 August 1999     

Cationic polymerization of selected α- and β-substituted vinyl ethers

Summary The cationic polymerization of various α- and β-substituted vinyl ethers, initiated by 1-iodo-1-(2-methylpropyloxy)ethane 1 and tetrabuty lammonium perchlorate (TBAP) was investigated. The polymerization of 2,3-dihydrofuran (DHF, 3a) in CH₂Cl₂ at -40°C proceeds via opening of the ethylenic double bond and yields polymers with narrow molar mass distributions and high glass transitions. The number average of molar mass increased linearly with conversion. Under these conditions, a controlled polymerization of two propenyl ethers (1-ethoxypropene 2a and 2-methoxypropene 2b) and two other cyclic unsaturated ethers (3,4-dihydro-2H-pyran 3b and 5-methyl-2,3-dihydrofuran 3c) could not be achieved. Either transfer reactions or the decomposition of 1 prevented the formation of high molar mass polymers of these vinyl ethers.     

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

This paper reviews a new family of olefin polymerization catalysts. The catalysts, named FI catalysts, are based on non‐symmetrical phenoxyimine chelate ligands combined with group 4 transition metals and were developed using “ligand‐oriented catalyst design”. FI catalysts display very high ethylene polymerization activities under mild conditions. The highest activity exhibited by a zirconium FI catalyst reached an astonishing catalyst turnover frequency (TOF) of 64,900 s ^–1 atm ^–1, which is two orders of magnitude greater than that seen with Cp₂ZrCl₂ under the same conditions. In addition, titanium FI catalysts with fluorinated ligands promote exceptionally high‐speed, living ethylene polymerization and can produce monodisperse high molecular weight polyethylenes (M_w/M_n<1.2, max. M_n>400,000) at 50 °C. The maximum TOF, 24,500 min ^–1 atm ^–1, is three orders of magnitude greater than those for known living ethylene polymerization catalysts. Moreover, the fluorinated FI catalysts promote stereospecific room‐temperature living polymerization of propylene to provide highly syndiotactic monodisperse polypropylene (max. [rr] 98%). The versatility of the FI catalysts allows for the creation of new polymers which are difficult or impossible to prepare using group 4 metallocene catalysts. For example, it is possible to prepare low molecular weight (M_v∼10³) polyethylene or poly(ethylene‐co‐propylene) with olefinic end groups, ultra‐high molecular weight polyethylene or poly(ethylene‐co‐propylene), high molecular weight poly(1‐hexene) with atactic structures including frequent regioerrors, monodisperse poly(ethylene‐co‐propylene) with various propylene contents, and a number of polyolefin block copolymers [e.g., polyethylene‐b‐poly(ethylene‐co‐propylene), syndiotactic polypropylene‐b‐poly(ethylene‐co‐propylene), polyethylene‐b‐poly(ethylene‐co‐propylene)‐b‐syndiotactic polypropylene]. These unique polymers are anticipated to possess novel material properties and uses.     

Synthesis of new fluorine containing ring-opened polynorbornene dicarboximides using ruthenium alkylidene catalysts

Summary  The synthesis of new N-4-trifluoromethylphenyl-exo-endo-norbornene-5,6-dicarboximide (TFmNDI, 2a) and N-3,5-difluorophenyl-exo-endo-norbornene-5,6-dicarboximide (DFNDI, 2b) was carried out. Polynorbornene dicarboximides, 3a and 3b, were obtained via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine) benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (II), respectively. T_g’s for polymers 3a and 3b were observed at 155 C and 142 C, respectively. Compared to polymer 3b, polymer 3a with the bulky trifluoromethyl group showed the highest glass transition temperature and improved mechanical properties.     

Synthesis and photoluminescence properties of heterocycle-containing poly(disubstituted acetylene)s

The metathesis polymerizations of disubstituted acetylenes containing heterocycles such as thiophene, furan, benzo[b]thiophene, and benzothiazole were examined using NbCl₅, TaCl₅, and WCl₆. Thiophene-containing monomers polymerized to afford relatively high-molecular-weight polymers in moderate yields. Benzo[b]thiophene-containing monomers also polymerized to give polymers with relatively high molecular weights. On the other hand, furan- and benzothiazole-containing monomers exhibited low metathesis polymerizability, and the polymerizations did not provide high-molecular-weight polymers. Poly(1-hexyl-2-arylacetylene)s having heterocycles [poly(1a) and poly(3a), Scheme 1] emitted blue-colored lights, and the emission maxima were around 480 nm. Heterocycle-containing poly(1-phenyl-2-arylacetylene) [poly(1b)] and poly(1-fluorenyl-2-arylacetylene) [poly(3d)] showed green-colored and yellow-colored emissions, and the emission maxima were 520 and 540 nm, respectively. The emission wavelengths of poly(disubstituted acetylene)s having heterocycles were almost the same as those of the corresponding poly(disubstituted acetylene)s without heterocycles. However, heterocycle-containing polymers showed high fluorescence quantum yields compared to the corresponding polymers without heterocycles. Diarylacetylene polymers showed emission red-shifts between the solution and cast film, while the emission maximum of poly(1-hexyl-2-phenylacetylene) [poly(1a)] in the cast film was almost the same as that in the solution. Benzo[b]thiophene-containing poly(1-(4-trimethylsilylphenyl)-2-phenylacetylene) [poly(3b)] and poly(1-(9,9-dimethyl-2-fluorenyl)-2-phenylacetylene) [poly(3d)] afforded the free-standing membranes because of their high molecular weights. The oxygen permeability coefficient (PO₂) of poly(3b) was as large as 1400 barrers. Poly(3d) showed higher gas permeability, and its PO₂ was 5300 barrers.     

Synthesis and properties of various poly(diphenylacetylenes) containing tert-amine moieties

The polymerization of diphenylacetylene derivatives possessing tert-amine moieties, such as triphenylamine, N-substituted carbazole and indole, was examined in the presence of TaCl₅-n-Bu₄Sn (1:2) catalyst. A polymer with high molecular weight (M_w = 570 × 10³) was obtained in good yield by the polymerization of diphenylamine-containing monomer 1b, whereas the isopropylphenylamine derivative (1c) gave a polymer with relatively low molecular weight (M_w = 2.4 × 10³). The polymerization of monomer 1d containing cyclohexylphenylamine group did not proceed; however, carbazolyl- and indolyl-containing monomers also produced polymers. Poly(1b), poly(2f) and poly(4b) could be fabricated into free-standing membranes by casting toluene solutions of these polymers. The gas permeability of poly(1b) was too low to be evaluated accurately whereas poly(4b) possessing two chlorine atoms in the repeating unit showed higher gas permeability than that of poly(1b); furthermore, poly(2f) having trimethylsilyl and 3-methylindolyl groups exhibited relatively high gas permeability (). In the cyclic voltammograms of diphenylamino group-containing polymers, poly(1b) and poly(2b), the intensities of oxidation and reduction peaks decreased more than those of carbazolyl-containing poly(2a). The molar absorptivity (?) of poly(1b) at ∼700 nm increased with increasing applied voltage in the UV-vis spectrum.     

Preparation of fatty epoxy alcohols using oat seed peroxygenase in nonaqueous media

Peroxygenase is an enzyme of higher plants that is capable of using hydroperoxide and hydrogen peroxide for oxidation of a double bond to an epoxide. A microsomal fraction was prepared from dry oat (Avena sativa) seeds. The peroxygenase activity of this fraction was tested using fatty acid hydroperoxide 2a [13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid] and its methyl ester 2b as sources of peroxygen. These were prepared by the action of soybean lipoxygenase on linoleic acid. A high-performance liquid chromatographic assay was used to differentiate between peroxygen cleavage and peroxygen cleavage with accompanying double-bond oxidation Higher activity was obtained with 2b compared to 2a, and peroxygen cleavage activity was observed in both aqueous and organic solvent media. Double-bond oxidation activity was high only in aqueous media and nonpolar organic solvents. Structural elucidation of the epoxidized product showed it to be the oxylipid, methyl cis-9,10-epoxy-13(S)-hydroxy-11(E)-octade-cenoate 4b, demonstrating specificity for epoxidation of the cis double bond. Trihydroxy product was not detected, demonstrating that the epoxide was not hydrolyzed.     

Synthesis of 9Z,11E-octadecadienoic and 10E,12Z-octadecadienoic acids, the major components of conjugated linoleic acid

Linoleic acid was efficiently converted into the two major components of conjugated linoleic acid, 9Z,11E-octadecadienoic (1a) and 10E,12Z-octadecadienoic acid (1b) using either the superbase (n-butyllithium/potassium tert-butoxide) or by simply refluxing with KOH in 1-butanol. In turn, 1a and 1b were separated from each other using the lipase from Aspergillus niger via stereoselective esterification in 1-butanol. This enzyme has a preference for the 9Z,11E isomer, 1a, and has excellent selectivity. This method has allowed the ready preparation of gram quantities of 1a and 1b in their highly purified forms, which are not readily accessible by current methods.     

Carbosilane Metallodendrimers with Cyclopentadienyldichlorotitanium(IV) End Groups

Dendritic polyols of the second and third generation 2G-OH₈ (1), 2G-OH₁₆ (2), and 3G-OH₁₆ (3) were prepared by hydroboration/oxidation of allyl-terminated carbosilane dendrimers and used as supports for the immobilization of cyclopentadienyltrichlorotitanium(IV) complexes via alcoholysis. The reaction of 1–3 with CpTiCl₃ gave metallodendrimers 2G-(OTiCpCl₂)₈ (4a), 2G-(OTiCpCl₂)₁₆ (5a), and 3G-(OTiCpCl₂)₁₆ (6a), respectively, whereas the reaction of 1 and 3 with CpSi^FTiCl₃ (CpSi^F = C₅H₄SiMe₂CH₂CH₂C₈F₁₇) yielded peripherally fluorinated metallodendrimers 2G-(OTiCpSi^FCl₂)₈ (4b) and 3G-(OTiCpSi^FCl₂)₁₆ (6b). All metallodendrimers were characterized by multinuclear NMR spectroscopy. The suggested structures were supported by comparison with model 1-propoxycomplexes 10a,b. To identify side products of the alcoholysis reaction, hydrolytic behavior of the starting trichloro complexes was studied both in solid state and in solution. The main products of hydrolysis in solution were identified as μ-oxocomplexes 8a,b whereas hydrolysis in solid state yielded mainly hydroxycomplexes 7a,b.