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Cyclohexene Oxide (cyclohexene + oxide)
Selected AbstractsAlternating Copolymerization of Cyclohexene Oxide and CO2 Catalyzed by Zinc Complexes with New 3-Amino-2-cyanoimidoacrylate LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2005Mario Kröger Abstract New 3-amino-2-cyanoimidoacrylate ligands with varying steric demands have been synthesized. Zinc acetate complexes of these ligands catalyze the copolymerisation of CO2 and cyclohexene oxide, showing high activities (TOF up to over 200,h,1). [source] Copolymerization of Cyclohexene Oxide with CO2 by Using Intramolecular Dinuclear Zinc CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2005Youli Xiao Abstract The intramolecular dinuclear zinc complexes generated in situ from the reaction of multidentate semi-azacrown ether ligands with Et2Zn, followed by treatment with an alcohol additive, were found to promote the copolymerization of CO2 and cyclohexene oxide (CHO) with completely alternating polycarbonate selectivity and high efficiency. With this type of novel initiator, the copolymerization could be accomplished under mild conditions at 1 atm pressure of CO2, which represents a significant advantage over most catalytic systems developed for this reaction so far. The copolymerization reaction was demonstrated to be a living process as a result of the narrow polydispersities and the linear increase in the molecular weight with conversion of CHO. In addition, the solid-state structure of the dinuclear zinc complex was characterized by X-ray crystal structural analysis and can be considered as a model of the active catalyst. On the basis of the various efforts made to understand the mechanisms of the catalytic reaction, including MALDI-TOF mass analysis of the copolymers' end-groups, the effect of alcohol additives on the catalysis and CO2 pressure on the conversion of CHO, as well as the kinetic data gained from in situ IR spectroscopy, a plausible catalytic cycle for the present reaction system is outlined. The copolymerization is initiated by the insertion of CO2 into the ZnOEt bond to afford a carbonate,ester-bridged complex. The dinuclear zinc structure of the catalyst remains intact throughout the copolymerization. The bridged zinc centers may have a synergistic effect on the copolymerization reaction; one zinc center could activate the epoxide through its coordination and the second zinc atom may be responsible for carbonate propagation by nucleophilic attack by the carbonate ester on the back side of the cis -epoxide ring to afford the carbonate. The mechanistic implication of this is particularly important for future research into the design of efficient and practical catalysts for the copolymerization of epoxides with CO2. [source] First Example of a Gold(I) N -Heterocyclic-Carbene-Based Initiator for the Bulk Ring-Opening Polymerization of L -LactideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Lipika Ray Abstract Synthesis, structure, and catalysis studies of two Au- and Ag-based initiators, namely, [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AuCl (1c) and [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AgCl (1b), for the bulk ring-opening polymerization of L -lactide are reported. Specifically, gold complex 1c was obtained from silver complex 1b by the transmetalation reaction with (SMe2)AuCl. Silver complex 1b was synthesized by the treatment of 3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazolium chloride (1a) with Ag2O. Compound 1a was synthesized directly from the reaction of N - tert -butyl-2-chloroacetamide, cyclohexene oxide, and imidazole. The molecular structures of 1a, 1b, and 1c have been determined by X-ray diffraction studies. The formation of neutral monomeric complexes with linear geometries at the metal centers was observed for both 1b and 1c. The Au and Ag complexes 1c and 1b successfully catalyzed the bulk ring-opening polymerization of L -lactide at elevated temperatures under solvent-free melt conditions to produce moderate to low molecular weight polylactide polymers with narrow molecular weight distributions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Asymmetric meso -Epoxide Ring-Opening with Trimethylsilyl Cyanide Promoted by Chiral Binuclear Complexes of Titanium.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Dichotomy of CC versus CN Bond Formation Abstract In the presence of chiral catalysts derived from the same chiral hexadentate ligand and aluminium, zinc or titanium ions, the reaction between cyclohexene oxide and trimethylsilyl cyanide can be controlled to give predominantly either the nitrile (up to 99% ee) or the isonitrile product (up to 94% ee). The metal ion, ligand stereochemistry and base concentration all play a role in determining the product ratio. [source] Alternating Copolymerization of Cyclohexene Oxide and CO2 Catalyzed by Zinc Complexes with New 3-Amino-2-cyanoimidoacrylate LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2005Mario Kröger Abstract New 3-amino-2-cyanoimidoacrylate ligands with varying steric demands have been synthesized. Zinc acetate complexes of these ligands catalyze the copolymerisation of CO2 and cyclohexene oxide, showing high activities (TOF up to over 200,h,1). [source] Synthesis of liquid crystalline,amorphous block copolymers by the combination of atom transfer and promoted cationic polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007S. Demirhan Abstract Block copolymers of liquid crystalline 6-(4-cyanobiphenyl-4,-oxy) hexyl acrylate (LC6) and cyclohexene oxide (CHO) were obtained by the combination of atom transfer radical polymerization (ATRP) and promoted cationic polymerization (PCP). In the first part, a bifunctional initiator containing benzoin and halide groups in the same structure was used as an initiator in ATRP of LC6, in diphenyl ether in conjunction with CuBr/N,N,N,,N,,N,-pentamethyldiethylenetriamine as a catalyst. The obtained photoactive liquid crystalline polymers poly[6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate] (PLC6), were used to induce polymerization of CHO through formation of electron donor polymeric radicals upon photolysis and subsequent oxidation to corresponding carbocations in the presence of onium salt. The spectral, thermal and optical measurements confirmed a full combination of ATRP and PCP, which resulted in the formation of AB-type block copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Alternating copolymerization of carbon dioxide and epoxide catalyzed by an aluminum Schiff base,ammonium salt systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2005Hiroshi Sugimoto Abstract The alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe (1a),tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a,Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain-transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172,4186, 2005 [source] Synthesis and Cyclohexene Oxide/Carbon Dioxide Copolymerizations of Zinc Acetate Complexes Bearing Bidentate Pyridine-Alkoxide LigandsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2004Il Kim Abstract Summary: The reaction of 2-lithio-6-methylpyridine or 2-lithiopyridine and the appropriate diaryl ketone followed by hydrolysis yields 6-Me-pyCAr2OH pyridine alcohols or pyCAr2OH pyridine alcohols. The reactions of zinc acetate with 1 equiv. of the lithiated products of the ligands proceed rapidly to afford LiOAc salt and mono-ligand complexes (6-Me-pyCAr2O)Zn(OAc) and (pyCAr2O)Zn(OAc), respectively, in high yield. The copolymerizations of carbon dioxide with cyclohexene oxide were investigated. The (6-Me-pyCAr2O)Zn(OAc) showed moderate yield and CO2 incorporation. The [6-Me-pyC(4-Cl-C6H4)2O]Zn(OAc) complex gave large polymers with high proportions of carbonate linkage (>60%) and narrow polydispersity, indicating single active sites. The monoligated Zn complexes synthesized and used here as catalysts for the copolymerization of cyclohexene oxide and carbon dioxide. [source] Synthesis of poly(cyclohexene oxide)- block -polystyrene by combination of radical-promoted cationic polymerization, atom transfer radical polymerization and click chemistryPOLYMER INTERNATIONAL, Issue 6 2010Mustafa Degirmenci Abstract The combination of radical-promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)- block -polystyrene (PCHO- b -PSt). Alkyne end-functionalized poly(cyclohexene oxide) (PCHO-alkyne) was prepared by radical-promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2-diphenyl-2-(2-propynyloxy)-1-ethanone (B-alkyne) and an onium salt, namely 1-ethoxy-2-methylpyridinium hexafluorophosphate, as the initiating system. The B-alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well-defined bromine-terminated polystyrene (PSt-Br) was prepared by ATRP using 2-oxo-1,2-diphenylethyl-2-bromopropanoate as initiator. Subsequently, the bromine chain end of PSt-Br was converted to an azide group to obtain PSt-N3 by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt-N3 and PCHO-alkyne was performed with Cu(I) catalysis in order to obtain the PCHO- b -PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry [source] Copolymerization of Cyclohexene Oxide with CO2 by Using Intramolecular Dinuclear Zinc CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2005Youli Xiao Abstract The intramolecular dinuclear zinc complexes generated in situ from the reaction of multidentate semi-azacrown ether ligands with Et2Zn, followed by treatment with an alcohol additive, were found to promote the copolymerization of CO2 and cyclohexene oxide (CHO) with completely alternating polycarbonate selectivity and high efficiency. With this type of novel initiator, the copolymerization could be accomplished under mild conditions at 1 atm pressure of CO2, which represents a significant advantage over most catalytic systems developed for this reaction so far. The copolymerization reaction was demonstrated to be a living process as a result of the narrow polydispersities and the linear increase in the molecular weight with conversion of CHO. In addition, the solid-state structure of the dinuclear zinc complex was characterized by X-ray crystal structural analysis and can be considered as a model of the active catalyst. On the basis of the various efforts made to understand the mechanisms of the catalytic reaction, including MALDI-TOF mass analysis of the copolymers' end-groups, the effect of alcohol additives on the catalysis and CO2 pressure on the conversion of CHO, as well as the kinetic data gained from in situ IR spectroscopy, a plausible catalytic cycle for the present reaction system is outlined. The copolymerization is initiated by the insertion of CO2 into the ZnOEt bond to afford a carbonate,ester-bridged complex. The dinuclear zinc structure of the catalyst remains intact throughout the copolymerization. The bridged zinc centers may have a synergistic effect on the copolymerization reaction; one zinc center could activate the epoxide through its coordination and the second zinc atom may be responsible for carbonate propagation by nucleophilic attack by the carbonate ester on the back side of the cis -epoxide ring to afford the carbonate. The mechanistic implication of this is particularly important for future research into the design of efficient and practical catalysts for the copolymerization of epoxides with CO2. [source] Enantiomerically Pure Titanium Complexes Containing an [OSSO]-Type Bis(phenolate) Ligand: Synthesis, Structure, and Formation of Optically Active OligostyrenesCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Geert-Jan M. Meppelder Abstract Chiral 1,2- trans -dithiocyclohexanediyl-bridged bis(phenols) of the type [2,2,-{HOC6H2 -6-R1 -4-R2}2S2C6H10] ([OSSO]H2, R1=tBu, iPr, H; R2=tBu, iPr, Me) could be conveniently and selectively synthesized in three steps, starting from cyclohexene oxide and arene thiolate. The racemic bis(phenols) could be resolved using an enantiopure (S)-camphorsulfonic ester auxiliary or by (chiral) HPLC. Complexation of the racemic bis(phenols) to TiX4 (X=Cl, OiPr) proceeds in a diastereoselective fashion to give only the ,,R,R and ,,S,S enantiomers. Racemic [Ti{(OC6H2 -6- tBu-4-Me)2S2C6H10}Cl2] reacts with benzyl magnesium bromide to afford the crystallographically characterized dibenzyl complex. The benzyl cation formed using B(C6F5)3 in C6D5Br slowly decomposes at temperatures above +10,°C. When treated with methylaluminoxane, the dichloro complexes [Ti{OSSO}Cl2] polymerize styrene with activities up to 146,kg,(mol,catalyst),1,[styrene,(mol,L,1)],1,h,1; diisopropoxy complexes [Ti{OSSO}(OiPr)2] show mere trace activity. With 1-hexene as a chain-transfer agent, activated enantiopure titanium complexes give low-molecular-weight homochiral isotactic oligostyrenes, terminated by one to five 1-hexene units with Mn values as low as 750,g,mol,1 for R=tBu and 1290,g,mol,1 for R=Me. Below Mn,5000 these oligostyrenes show optical activity. [source] | |||||||||||||