Showing papers on "Epoxide published in 2015"
TL;DR: Highly active bifunctional diporphyrin and triporphyrin catalysts synthesized through Stille coupling reactions exhibited improved catalytic activities for the reaction of CO2 with epoxides to form cyclic carbonates, because of the multiple catalytic sites which cooperatively activate the epoxide.
Abstract: Highly active bifunctional diporphyrin and triporphyrin catalysts were synthesized through Stille coupling reactions. As compared with a porphyrin monomer, both exhibited improved catalytic activities for the reaction of CO2 with epoxides to form cyclic carbonates, because of the multiple catalytic sites which cooperatively activate the epoxide. Catalytic activities were carefully investigated by controlling temperature, reaction time, and catalyst loading, and very high turnover number and turnover frequency were obtained: 220 000 and 46 000 h−1, respectively, for the magnesium catalyst, and 310 000 and 40 000 h−1, respectively, for the zinc catalyst. Results obtained with a zinc/free-base hybrid diporphyrin catalyst demonstrated that the Br− ions on the adjacent porphyrin moiety also function as nucleophiles.
255 citations
TL;DR: The synthesis and properties of a heterod inuclear Zn(II)/Mg(II) complex coordinated by a symmetrical macrocyclic ligand shows high polymerization selectivity, control, and significantly greater activity compared to either of the homodinuclear analogues or any combinations of them.
Abstract: Homodinuclear catalysts have good precedent for epoxide and carbon dioxide/anhydride copolymerizations; in contrast, so far pure heterodinuclear catalysts are unknown. The synthesis and properties of a heterodinuclear Zn(II)/Mg(II) complex coordinated by a symmetrical macrocyclic ligand are reported. It shows high polymerization selectivity, control, and significantly greater activity compared to either of the homodinuclear analogues or any combinations of them. Indeed, compared to a 50:50 mixture of the homodinuclear complexes, it shows 5 times (CO2/epoxide) or 40 times (anhydride/epoxide) greater activity.
173 citations
TL;DR: A mesoporous-C4N4-based catalyst (n-butBr/mp-C3N4) was prepared by simple grafting of n-bromobutane as mentioned in this paper.
114 citations
TL;DR: The obtained poly(vinylcyclohexene carbonate) presents pending vinyl groups, which allowed post-synthetic cross-linking by reaction with 1,3-propanedithiol, thus opening new opportunities for the application of these green polymers.
Abstract: The atom-efficient reaction of CO2 with a variety of epoxides has been efficiently achieved employing iron pyridylamino-bis(phenolate) complexes as bifunctional catalysts. The addition of a Lewis base co-catalyst allowed significant reduction in the amount of iron complex needed to achieve high epoxide conversions. The possibility of controlling the selectivity of the reaction towards either cyclic carbonate or polycarbonate was evaluated. An efficient switch in selectivity could be achieved when cyclic epoxides such as cyclohexene oxide and the seldom explored 1,2-epoxy-4-vinylcyclohexane were used as substrates. The obtained poly(vinylcyclohexene carbonate) presents pending vinyl groups, which allowed post-synthetic cross-linking by reaction with 1,3-propanedithiol. The cross-linked polycarbonate displayed a substantial increase in the glass transition temperature and chemical resistance, thus opening new opportunities for the application of these green polymers.
104 citations
TL;DR: In this paper, a block copolymerization of e-caprolactone, cyclohexene oxide, and carbon dioxide monomers using a dinuclear zinc catalyst is presented.
Abstract: The preparation of ABA type block copoly(ester-b-carbonate-b-ester) from a mixture of e-caprolactone, cyclohexene oxide, and carbon dioxide monomers and using a single catalyst is presented. By using a dinuclear zinc catalyst, both the ring-opening polymerization of e-caprolactone and the ring-opening copolymerization of cyclohexene oxide and carbon dioxide are achieved. The catalyst shows high selectivity, activity, and control in the ring-opening copolymerization, yielding poly(cyclohexene carbonate) polyols, i.e., α,ω-dihydroxyl end-capped polycarbonates. It also functions efficiently under immortal conditions, and in particular, the addition of various equivalents of water enables the selective preparation of polyols and control over the polymers’ molecular weights and dispersities. The catalyst is also active for the ring-opening polymerization of e-caprolactone but only in the presence of epoxide, generating α,ω-dihydroxyl-terminated polycaprolactones. It is also possible to combine the two polymeri...
101 citations
TL;DR: In this article, a series of functional graphene oxide (F-GO) materials were prepared by silylanization of graphene oxide with chlorine-terminal silanes and subsequent nucleophilic substitution reaction with tertiary amine in a one-pot approach.
95 citations
TL;DR: In this paper, a D-labeled epoxide and an optically active epoxide were used to study the reaction mechanism, which invoked three plausible pathways, among which path A seemed to be the predominant; the bicarbonate ion of TBABC attacks the less hindered C atom of the epoxide to generate a ring-opened alkoxide intermediate, which adds to CO2 to give a carbonate ion, and the subsequent cyclization yields a cyclic carbonate.
95 citations
TL;DR: In this paper, a review examines the latest reports, including homogeneous and heterogeneous applications, showing that unsophisticated complexes of group III-V transition metals are excellent molecular catalysts.
Abstract: Complexes of group III–V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (CC versus CO) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (CO bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of group III–V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (CC bond cleavage).
82 citations
TL;DR: It is demonstrated that a tetrahydrofuranyl polyene is the first stable intermediate in the transformation, which can undergo epoxidation and anti-Baldwin 6-endo-tet ring opening to yield the cyclic ether product.
Abstract: Aurovertins are fungal polyketides that exhibit potent inhibition of adenosine triphosphate synthase Aurovertins contain a 2,6-dioxabicyclo[321]octane ring that is proposed to be derived from a polyene precursor through regioselective oxidations and epoxide openings In this study, we identified only four enzymes required to produce aurovertin E The core polyketide synthase produces a polyene α-pyrone Following pyrone O-methylation by a methyltransferase, a flavin-dependent mono-oxygenase and an epoxide hydrolase can iteratively transform the terminal triene portion of the precursor into the dioxabicyclo[321]octane scaffold We demonstrate that a tetrahydrofuranyl polyene is the first stable intermediate in the transformation, which can undergo epoxidation and anti-Baldwin 6-endo-tet ring opening to yield the cyclic ether product Our results further demonstrate the highly concise and efficient ways in which fungal biosynthetic pathways can generate complex natural product scaffolds
76 citations
TL;DR: In this article, the substituent effect of epoxides on CO2/epoxide copolymerization catalyzed by a nanosized zinc-cobalt-III double metal cyanide complex [Zn-Co(III) DMCC] was described.
Abstract: In this study, we describe the substituent effect of epoxides on CO2/epoxide copolymerization catalyzed by a nanosized zinc–cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC]. The Zn–Co(III) DMCC catalyzed the copolymerization of CO2 with 11 epoxides with alkyl or aryl groups at 50–60 °C within 15 h. The reaction afforded various CO2/epoxide copolymers with high epoxide conversion efficiencies up to 100%. The alternating degree (FCO2) of the resulting copolymer was solely decided by the steric hindrance of the substituents of the epoxides regardless of their electron-donating or withdrawing properties. Substituents with large steric hindrances (2, 2-dimethyl, tert-butyl, cyclohexyl, decyl, and benzyl) led to highly alternating degrees (up to 100%). The regioselective CO2/epoxide copolymerization was dominated by the electron induction effect of the substituent. The electron-withdrawing substituent such as phenyl and benzyl induced regioselective ring-opening at the methine site of the epoxide. For...
71 citations
TL;DR: In this article, reversible epoxide opening/closing reactions in graphene oxide (GO) were discovered upon alkaline and acid treatments, respectively, under ambient conditions, and the epoxide formation was observed in base-treated GO under flux conditions, which is due to the decomposition of the vic-diol groups formed by epoxy ring opening.
TL;DR: A tandem chemoenzymatic transformation that combines alkene metathesis with enzymatic epoxidation to provide aryl epoxides is reported, which converts a mixture of alkenes into a single epoxide product in high enantioselectivity and moderate yields.
Abstract: We report the development of a tandem chemoenzymatic transformation that combines alkene metathesis with enzymatic epoxidation to provide aryl epoxides. The development of this one-pot reaction required substantial protein and reaction engineering to improve both selectivity and catalytic activity. Ultimately, this reaction converts a mixture of alkenes into a single epoxide product in high enantioselectivity and moderate yields and illustrates both the challenges and benefits of tandem catalysis combining organometallic and enzymatic systems.
TL;DR: A new type of cascade biocatalysis was developed for one-pot enantioselective conversion of a meso- or racemic epoxide to an α-hydroxy ketone in high ee via an epoxide hydrolase-catalyzed hydrolysis of the epoxide, an alcohol dehydrogenase-Catalyzed oxidation of the diol intermediate, and an enzyme-catalystzed cofactor regeneration.
Abstract: A new type of cascade biocatalysis was developed for one-pot enantioselective conversion of a meso- or racemic epoxide to an α-hydroxy ketone in high ee via an epoxide hydrolase-catalyzed hydrolysis of the epoxide, an alcohol dehydrogenase-catalyzed oxidation of the diol intermediate, and an enzyme-catalyzed cofactor regeneration. In vitro cascade biotransformation of meso-epoxides (cyclopentene oxide 1a, cyclohexene oxide 1b, and cycloheptene oxide 1c) was achieved with cell-free extracts containing recombinant SpEH (epoxide hydrolase from Sphingomonas sp. HXN-200), BDHA (butanediol dehydrogenase from Bacillus subtilis BGSC1A1), and LDH (lactate dehydrogenase form Bacillus subtilis) or NOX (NADH oxidase from Lactobacillus brevis DSM 20054), respectively, giving the corresponding (R)-α-hydroxycyclopentanone 3a, (R)-α-hydroxycyclohexanone 3b, and (R)-α-hydroxycycloheptanone 3c in 98–99% ee and 70–50% conversion with TTN of NAD+-recycling of 5500–26 000. Cascade catalysis with mixed cells of Escherichia col...
TL;DR: In this paper, a new preparation method for solid-supported crown ethers (CE) as lithium ion (Li+) adsorbents is presented, which can be used for precious metal ions recovery.
TL;DR: Epoxide alkylations allow the reactions to be conducted in wet protic media and give sulfonium products that are stable against dealkylation and allow facile incorporation of an unprecedented range of functional groups onto simple polypeptides using stable linkages.
TL;DR: Enantioselective 3-exo iodo iodo-cycloetherification of allyl alcohols was realized by employing a novel ion-pair organocatalyst.
Abstract: By designing a novel chiral ion-pair organocatalyst composed of chiral phosphate and DABCO-derived quaternary ammonium, highly enantioselective 3-exo iodo-cycloetherification of allyl alcohols was achieved using NIS as a halogen source. Based on this reaction, one-pot asymmetric 3-exo iodo-cycloetherification/Wagner–Meerwein rearrangement of allyl alcohols en route to enantioenriched 2-iodomethyl-2-aryl cycloalkanones was subsequently developed. Due to the participation of adjacent iodine, the Wagner–Meerwein rearrangement of 2-iodomethyl-2-aryl epoxide proceeds with unusual retention of stereoconfiguration.
TL;DR: In this paper, a tetradentate cross-linker was used to obtain a 50% increase in rubbery modulus between 50% and 100% CC bond conversion.
TL;DR: In this paper, the catalysts were characterized using infrared (IR) and Raman spectroscopies, thermogravimetric analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy (SEM) and TEM.
Abstract: Cobalt(II), iron(III) or oxovanadium(II) Schiff base metal complexes have been covalently grafted onto graphene oxide (GO) previously functionalized with 3-aminopropyltriethoxysilane. Potential catalytic behaviors were tested in the epoxidation of styrene, using air as the oxidant. The catalysts were characterized using infrared (IR) and Raman spectroscopies, thermogravimetric analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction, nitrogen adsorption–desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). IR spectroscopy, thermogravimetric analyses and ICP-AES confirmed the successful incorporation of the metal Schiff base complexes onto GO. X-ray diffraction, nitrogen adsorption–desorption, Raman spectroscopy, SEM and TEM showed the intact structure of the GO. Co-GO and Fe-GO showed high styrene conversion (90.8 versus 86.7%) and epoxide selectivity (63.7 versus 51.4%). Nevertheless, VO-GO showed poorer catalytic performance compared with Co-GO and Fe-GO. The recycling results of these heterogeneous catalysts showed good recoverability without significant loss of activity and selectivity within four successive runs. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: The synthesis and characterization of a degradable version of poly(acrylic acid), poly(glyceric acid carbonate), are reported, which exhibits an improved cell cytotoxicity profile and degrade remarkably fast.
Abstract: The synthesis and characterization of a degradable version of poly(acrylic acid), poly(glyceric acid carbonate), are reported. Specifically, atactic and isotactic poly(benzyl glycidate carbonate)s are obtained via the ring-opening copolymerization of rac-/(R)-benzyl glycidate with CO2 using a bifunctional rac-/(S,S)-cobalt salen catalyst in high carbonate linkage selectivity (>99%) and polymer/cyclic carbonate selectivity (∼90%). Atactic poly(benzyl glycidate carbonate) is an amorphous material with a T(g) (glass transition temperature) of 44 °C, while its isotactic counterpart synthesized from enantiopure epoxide and catalyst is semicrystalline with a T(m) (melting temperature) = 87 °C. Hydrogenolysis of the resultant polymers affords the poly(glyceric acid carbonate). Poly(glyceric acid carbonate) exhibits an improved cell cytotoxicity profile compared to poly(acrylic acid). Poly(glyceric acid carbonate)s also degrade remarkably fast (t(1/2) ≈ 2 weeks) compared to poly(acrylic acid). Cross-linked hydrogels prepared from poly(glyceric acid carbonate) and poly(ethylene glycol) diaziridine show significant degradation in pH 8.4 aqueous buffer solution compared to similarly prepared hydrogels from poly(acrylic acid) and poly(ethylene glycol) diaziridine.
TL;DR: An alternative pathway to the Wacker oxidation of internal olefins involving epoxidation of trans-alkenes followed by a mild and highly regioselective isomerization to give the major ketone isomers in 66-98% yield is reported.
Abstract: We report an alternative pathway to the Wacker oxidation of internal olefins involving epoxidation of trans-alkenes followed by a mild and highly regioselective isomerization to give the major ketone isomers in 66–98% yield. Preliminary kinetics and isotope labeling studies suggest epoxide ring opening as the turnover limiting step in our proposed mechanism. A similar catalytic system was applied to the kinetic resolution of select trans-epoxides to give synthetically useful selectivity factors of 17–23 for benzyl-substituted substrates.
TL;DR: For the first time, the mechanism of O-atom transfer to alkenes is studied using the Fe(V)(O) complex of biuret-modified Fe-TAML at room temperature and the second-order rate constant (k2) was determined under single-turnover conditions.
Abstract: In biological oxidations, the intermediate Fe(V)(O)(OH) has been proposed to be the active species for catalyzing the epoxidation of alkenes by nonheme iron complexes. However, no study has been reported yet that elucidates the mechanism of direct O-atom transfer during the reaction of Fe(V)(O) with alkenes to form the corresponding epoxide. For the first time, we study the mechanism of O-atom transfer to alkenes using the Fe(V)(O) complex of biuret-modified Fe-TAML at room temperature. The second-order rate constant (k2) for the reaction of different alkenes with Fe(V)(O) was determined under single-turnover conditions. An 8000-fold rate difference was found between electron-rich (4-methoxystyrene; k2 = 216 M(-1) s(-1)) and electron-deficient (methyl trans-cinnamate; k2 = 0.03 M(-1) s(-1)) substrates. This rate difference indicates the electrophilic character of Fe(V)(O). The use of cis-stilbene as a mechanistic probe leads to the formation of both cis- and trans-stilbene epoxides (73:27). This suggests the formation of a radical intermediate, which would allow C-C bond rotation to yield both stereoisomers of stilbene-epoxide. Additionally, a Hammett ρ value of -0.56 was obtained for the para-substituted styrene derivatives. Detailed DFT calculations show that the reaction proceeds via a two-step process through a doublet spin surface. Finally, using biuret-modified Fe-TAML as the catalyst and NaOCl as the oxidant under catalytic conditions epoxide was formed with modest yields and turnover numbers.
TL;DR: In this paper, three asymmetric FeIII complexes, namely, FeL1Cl (1), FeL2Cl (2) and FeL3Cl (3), have been prepared from their corresponding ligands.
Abstract: Three chiral Schiff base ligands H2L1, H2L2, H2L3 have been synthesized by treating (R)-1,2-diaminopropane separately with 3,5-dichlorosalicylaldehyde, 3,5-dibromosalicylaldehyde and 3,5-diiodosalicylaldehyde, respectively. Three new asymmetric FeIII complexes, namely, FeL1Cl (1), FeL2Cl (2), FeL3Cl (3) have been prepared from their corresponding ligands. The crystal structure of 2 reveals that the complexes are mononuclear in nature. Circular dichroism (CD) studies suggest that the ligands and their corresponding complexes contain an asymmetric center. The catalytic activity of these complexes toward the epoxidation of alkenes has been investigated in the presence of iodosylbenzene (PhIO), in two solvents CH3CN and CH2Cl2. The epoxide yield suggests that the order of their catalytic efficiency is 3 > 2 > 1. This trend as well as the role of substitution on the ligand backbone on alkene epoxidation has also been confirmed by density functional theory (DFT) calculations. For further adaptation, we attached our most efficient homogeneous catalyst, 3, with surface modified magnetic nanoparticles (Fe3O4@dopa) and thereby obtained the new magnetically separable nanocatalyst Fe3O4@dopa@FeL3Cl. This catalyst has been characterized and its olefin epoxidation ability investigated in similar conditions to those used for homogeneous catalysts. The enantiomeric excess of the epoxide yield reveals the retention of chirality of the active site of Fe3O4@dopa@FeL3Cl. The catalyst can be easily recovered by magnetic separation and recycled several times without significant loss of its catalytic activity.
TL;DR: In this paper, the authors used diphenyl phosphate (DPP) to catalyze ring-opening polymerization reactions of three renewable 5-alkyl δ-lactones.
TL;DR: In this article, a CO2-based oligo(carbonate-ether) tetraol was synthesized in a controlled manner by immortal copolymerization of carbon dioxide and propylene oxide (PO) in the presence of 1,2,4,5-benzenetetracarboxylic acid (btcH4) catalyzed by using a zinc-cobalt double metal cyanide (Zn-Co-DMC) catalyst.
TL;DR: An in situ formed porphyrin-inspired iron complex that catalyzes asymmetric epoxidation of di- and trisubstituted enones is described and the practical utility of the new catalyst system is demonstrated by the gram-scale synthesis of optically pure epoxide.
TL;DR: In this paper, it was shown that soluble Bi salts exhibit catalytic activity toward the oxidation of olefins with H2O2 and showed that the most plausible mechanism of epoxidation includes substitution of a water ligand in the initial Bi aqua complex, hydrolysis of the coordinated H 2O2, one-step oxygen transfer through a direct olefin attack at the unprotonated O atom of the OOH- ligand, and liberation of the epoxide from the coordination sphere of Bi.
Abstract: Theoretical (DFT) calculations predict that soluble Bi salts exhibit catalytic activity toward oxidation of olefins with H2O2. Reaction occurs via two competitive channels: (i) nonradical epoxidation of the C═C double bond and (ii) radical hydroperoxidation of the allylic C atom(s) with involvement of the HO• radicals, realized concurrently and leading to epoxide/diol and alkenylhydroperoxide products, respectively. The most plausible mechanism of epoxidation includes the substitution of a water ligand in the initial Bi aqua complex, hydrolysis of the coordinated H2O2, one-step oxygen transfer through a direct olefin attack at the unprotonated O atom of the OOH– ligand in [Bi(H2O)5(OOH)]2+, and liberation of the epoxide from the coordination sphere of Bi. The main conclusions of the theoretical calculations were confirmed by preliminary experiments on oxidation of cyclohexene, cyclooctene, and 1-octene with the systems Bi(NO3)3/H2O2/CH3CN + H2O and BiCl3/H2O2/CH3CN + H2O.
TL;DR: Stereochemically inert and positively charged chiral complexes of Co(III) were shown to catalyze the asymmetric epoxidation of chalcones with H2O2 under phase transfer conditions as discussed by the authors.
Abstract: Stereochemically inert and positively charged chiral complexes of Co(III) were shown to catalyze the asymmetric epoxidation of chalcones with H2O2 under phase transfer conditions. The reaction products had enantiomeric purities of up to 55%. It was also shown that complex 1a I− catalyzed the coupling reaction of a resulting epoxide with CO2 (conversion 72%).
Patent•
21 Jul 2015TL;DR: In this article, a method for preparing high purity epoxide compounds and compositions derived from the epoxide compound are described. But the methods for preparing the high purity compounds are not described.
Abstract: High purity epoxide compounds, methods for preparing the high purity epoxide compounds, and compositions derived from the epoxide compounds are provided. Also provided are materials and articles derived from the epoxide compounds.
TL;DR: In this article, an imidazolium-and pyrrolidinium-based bis(epoxide)-functionalized ionic liquid (IL) monomers were synthesized and reacted with multifunctional amine monomers to produce cross-linked, epoxy-amine poly(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes.
Abstract: New imidazolium- and pyrrolidinium-based bis(epoxide)-functionalized ionic liquid (IL) monomers were synthesized and reacted with multifunctional amine monomers to produce cross-linked, epoxy–amine poly(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and chemical nature (i.e., alkyl versus ether) between the imidazolium group and epoxide groups were studied to determine their effects on CO2 affinity. The CO2 uptake (millimoles per gram) of the epoxy–amine resins (between 0.1 and 1 mmol/g) was found to depend predominately on the epoxide-to-amine ratio and the bis(epoxide) IL molecular weight. The effect of using a primary versus a secondary amine-containing multifunctional monomer was also assessed for the resin synthesis. Secondary amines can increase CO2 permeability but also increase the time required for bis(epoxide) conversion. When either the epoxide or amine monomer structure is changed, the CO2 solubility and permeability of the resulting PIL resins and ion-gel membranes can be...
Journal Article•