Terminal Epoxides Research Articles

Selective Synthesis of Cyclic Carbonate by Salalen-Aluminum Complexes and Mechanistic Studies.

Salalen-aluminum complexes were synthesized and used as catalysts in the reactions of CO2 with different epoxides. The reaction of cyclohexene oxide and CO2 was thoroughly investigated. In particular, the effect of the reaction conditions (nature and equivalents of the co-catalyst, CO2 pressure, and temperature) and of the ligands (substituents on the ancillary ligand, nature of the labile ligand, and nature of the nitrogen-donor atoms) on the results of this reaction was studied. The cycloaddition reaction of CO2 with terminal epoxides bearing different functional groups was realized. Moreover, NMR mechanistic studies provided information on the catalytic cycle. Interestingly, the characterization of an intermediate species in the mechanism of the reaction of cyclohexene oxide with CO2 , catalyzed by one of the salalen-aluminum complexes, was accomplished.

Dimethyldioxirane (DMDO) as a valuable oxidant for the synthesis of polyfunctional aromatic imidazolium monomers bearing epoxides

In this work, we describe the reactivity of various oxidizing agents to develop a strong, clean and powerful methodology in order to generate epoxidized salts. These new polyfunctional imidazolium monomers incorporating aromatic rings and terminal epoxides have high purity and excellent thermal stability by DSC and TGA analyses.

Activation of (salen)CoI complex by phosphorane for carbon dioxide transformation at ambient temperature and pressure

The activation of a (salen)CoI complex by phosphorane in situ formed a bifunctional catalyst for the reaction of carbon dioxide with terminal epoxides or aziridines at ambient temperature and 1 bar carbon dioxide pressure.

Polystyrene-supported bifunctional resorcinarenes as cheap, metal-free and recyclable catalysts for epoxide/CO2 coupling reactions

A bifunctional and recyclable organocatalyst shows excellent performance in the formation of cyclic carbonates from both terminal and internal epoxides.

An in situ formed Ca2+–crown ether complex and its use in CO2-fixation reactions with terminal and internal epoxides

Calcium punched beyond its weight: An in situ formed Ca2+–crown ether complex showed unprecedented efficiency in cyclic carbonate synthesis.

Aluminum complexes derived from a hexadentate salen-type Schiff base: synthesis, structure, and catalysis for cyclic carbonate synthesis.

Different aluminum complexes were synthesized by the reaction of aluminum alkyls with a hexadentate salen-type Schiff base. The reaction of N,N'-bis(3,5-di-tert-butylsalicylidene)-2,2'-(ethylenedioxy)dianiline (LH2) with one equiv. of AlMe3 in toluene at 100 °C proceeded by methane elimination to produce the intermediate methyl complex [AlMeL] (1), and then subsequent intramolecular methyl migration to give the aluminum complex [AlL'] (2) [L' = (2-O-3,5-tBu2C6H2)CH[double bond, length as m-dash]NC6H4OCH2CH2OC6H4NCH(Me)(2'-O-3',5'-tBu2C6H2)]. The reaction of the same ligand with AlEt3 under the same experimental conditions involved ethane elimination, ethylene elimination and intramolecular hydrogen migration, and led to the complex [AlL''] (3) [L'' = (2-O-3,5-tBu2C6H2)CH[double bond, length as m-dash]NC6H4OCH2CH2OC6H4NCH2(2'-O-3',5'-tBu2C6H2)]. However, the interaction of two equivalents of AlMe3 and AlEt3 afforded the corresponding binuclear complexes [(AlMe2)2L] (4) and [(AlEt2)2L] (5), respectively, and no methyl or hydrogen migration was found. The solid-state structures of aluminum complexes 1-3 were determined by single-crystal X-ray diffraction. It was found that complexes 2-5 show a very effective catalytic activity for the cycloaddition of epoxides and CO2 in the presence of NBu4Br as a cocatalyst at atmospheric pressure.

Copper-catalyzed/mediated borylation reactions of epoxides with diboron reagents: access to β-hydroxyl boronic esters.

We report the first copper-catalyzed/mediated borylative ring opening reaction of epoxides. This process represents a direct borylative C(sp3)-O bond cleavage of terminal epoxide substrates with commercially available diboron reagents. A wide range of epoxides with different functional groups are involved, and were subsequently converted to the corresponding β-hydroxyl boronic esters smoothly. Moreover, the ring opening product β-pinacol boronate alcohol provided a more beneficial approach for the formation of C-C and C-N bonds.

Anion exchangers with negatively charged functionalities in hyperbranched ion-exchange layers for ion chromatography

Novel pellicular poly(styrene-divinylbenzene)-based (PS-DVB) anion exchangers with covalently-bonded hyperbranched functional ion-exchange layers containing negatively charged functionalities are obtained and examined. The hyperbranched coating is created on the surface of aminated PS-DVB substrate by repeating the modification cycles including alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE), and amination of the terminal epoxide rings with methylamine (MA) or glycine (Gly). The influence of the position and the number of the layers with glycine, as well as of the total number of the layers of amine in the coating on the chromatographic properties of the obtained stationary phases is investigated. Chromatographic performance of the obtained stationary phases is evaluated using the model mixtures of inorganic and organic anions with hydroxide eluent. It is shown that the best selectivity toward weakly retained organic acids and oxyhalides is possessed by the anion exchanger obtained after 5 modification cycles, with glycine being used in the first one. Such anion exchanger packed in 25-cm long column is capable of separating 22 anions in 58min including 7 standard anions, mono-, di- and trivalent organic acids, oxyhalides, and some other double- and triple-charged anions.

Aluminum‐Catalyzed Formation of Functional 1,3,2‐Dioxathiolane 2‐Oxides from Sulfur Dioxide: An Easy Entry towards N‐Substituted Aziridines

AbstractAluminum(III) complexes derived from aminotriphenolate ligands are shown to be excellent catalysts for the formation of cyclic sulfites from a range of (functionalized) terminal and internal epoxides, and ex situ generated sulfur dioxide. The developed catalytic protocol is characterized by its operational simplicity, wide scope in epoxide reaction partners, good to excellent isolated yields and mild reaction conditions [50–70 °C, p(SO2) <1 bar]. The synthetic potential of these cyclic sulfites in organic synthesis is demonstrated in the preparation of N‐substituted aziridines through a three‐step protocol.magnified image

ChemInform Abstract: Atom Economical Synthesis of Di‐ and Trithiocarbonates by the Lithium tert‐Butoxide Catalyzed Addition of Carbon Disulfide to Epoxides and Thiiranes.

Alkali metal alkoxides were studied as catalysts for the addition of CS2 to epoxides. A screening of several commercially available alkoxides revealed lithium tert-butoxide as an active and selective catalyst for this reaction. The influence of different reaction parameters as well as the substrate scope under optimized reaction conditions has been studied. Terminal and highly substituted epoxides as well as thiiranes were converted. In total 28 products were prepared and isolated in yields up to 95%. Notably, the reactions were performed under mild conditions without additional solvents. The regio- and stereoselectivity of the reaction has been studied e.g. by converting (R)-styrene and (R)-propylene oxide. Moreover, the test reaction was monitored by (13)C NMR and a plausible mechanism for the conversion of terminal and internal epoxides is given. This proposal is in agreement with the observed regio- and stereoselectivity of the reaction.

ChemInform Abstract: Selective Synthesis of 5‐Substituted N‐Aryloxazolidinones by Cycloaddition Reaction of Epoxides with Arylcarbamates Catalyzed by the Ionic Liquid BmimOAc.

A selective procedure for the synthesis of 5-substituted N-aryloxazolidinones by the coupling of epoxides with arylcarbamates catalyzed by ionic liquids has been developed. The effects of reaction time, reactant molar ratio, amount of catalyst, and temperature were investigated. Under the optimal reaction conditions, BmimOAc exhibited efficient catalytic activity compared with other ionic liquids leading to the formation of 5-substituted N-aryloxazolidinones in excellent yields. In addition, chiral 5-substituted oxazolidinones were synthesized by this procedure in good-to-excellent yields with enantiomeric excesses in excess of 99.9 % starting from chiral terminal epoxides. A possible reaction mechanism is discussed in accord with the results obtained by 1H NMR spectroscopy and DFT calculations, which indicate the cooperative activation by BmimOAc through the formation of hydrogen bonds with the substrates.

A Bimetallic Aluminium(Salphen) Complex for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide.

A bimetallic aluminium(salphen) complex is reported as a sustainable, efficient and inexpensive catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide. In the presence of this complex and tetrabutylammonium bromide, terminal and internal epoxides reacted at 50 °C and 10 bar carbon dioxide pressure to afford their corresponding cyclic carbonates in yields of 50-94 % and 30-71 % for terminal and internal cyclic carbonates, respectively. Mechanistic studies using deuterated epoxides and an analogous monometallic aluminium(salphen) chloride complex support a mechanism for catalysis by the bimetallic complex, which involves intramolecular cooperative catalysis between the two aluminium centres.

속도론적 분할법을 통한 말단 에폭사이드로부터 고광학순도의 아렌술폰산 2-하이드록시 에스터의 합성

속도론적 분할법을 통한 말단 에폭사이드로부터 고광학순도의 아렌술폰산 2-하이드록시 에스터의 합성

“Fiddler crab-type” imidazolium salt as remote substituents tuning organocatalyst for the cycloaddition of epoxides with carbon dioxide

A series of unsymmetrical pyridine-bridged pincer-type imidazolium salts are synthesized and demonstrated as highly active catalyst. This catalyst is for the cycloaddition of carbon dioxide with a broad range of terminal epoxides without organic solvent, and co-catalyst. The performance of catalyst considerably depends on the remote structural feature bearing pyridine ring. In addition, bulky internal epoxide is efficiently converted to the desired product. The robustness of the catalytic system is shown by recycling the catalyst over seven consecutive times without significant loss of activity.

Covalently-bonded hyperbranched poly(styrene-divinylbenzene)-based anion exchangers for ion chromatography

A number of covalently-bonded hyperbranched poly(styrene-divinylbenzene)-based (PS-DVB) anion exchangers having functional ion exchange layers of different branching degrees are prepared and investigated. The attachment of the hyperbranched functional layers to the substrate surface is realized via anchor secondary amino groups inserted into the polymeric backbone by means of acylation with acetic anhydride followed by reductive amination with methylamine. Further modification of the obtained secondary amino groups is provided by repeating the steps of alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE) and amination of the terminal epoxide rings with methylamine (MA). The variation of the number of cycles including modification with 1,4-BDDGE and MA results in selectivity alterations for the obtained anion exchangers. Chromatographic parameters of the obtained stationary phases are evaluated using the model mixtures of anions (F−, HCOO−, Cl−, EtCOO−, BrO3−, NO2−, Br−, NO3−, SO42−, PO43−) with hydroxide and carbonate/bicarbonate eluents. The anion exchangers show the increase of NO2−/EtCOO− and NO2−/BrO3− selectivity and the decrease of EtCOO−/Cl− selectivity with increasing the number of modification cycles. In case of anion exchanger obtained after three modification cycles, the calculated values of column efficiencies for polarizable NO2− and Br− are up to 18,000 and 16,000N/m, respectively.

ChemInform Abstract: Highly Active and Robust Metalloporphyrin Catalysts for the Synthesis of Cyclic Carbonates from a Broad Range of Epoxides and Carbon Dioxide.

AbstractThe title reaction is successfully applied to mono‐ and 1,1‐ as well as 1,2‐disubstituted terminal and internal epoxides as well as diepoxides.

Ionic liquids-functionalized porphyrins as bifunctional catalysts for cycloaddition of carbon dioxide to epoxides

Six ionic liquids-functionalized metallophorphyrins have been designed, prepared and characterized by NMR, MS and elemental analysis. They were applied as efficient bifunctional catalysts to the cycloaddition of epoxides and carbon dioxide without additive and organic solvent yielding cyclic carbonates. 5,15-Di[4-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide (JBp) and 5,15-di[3-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide (JBm) have been demonstrated excellent activities under optimized conditions. It has been found that both the structure of porphyrin complex cations and the anion moieties would strongly affect their catalytic performance. The catalysts were versatile for the cycloaddition of CO2 to various terminal epoxides in satisfying yields with excellent selectivities. Moreover, phenoxypropylene carbonate was able to be obtained under atmosphere pressure of CO2 and in large-scale. Furthermore, a plausible mechanism involving Lewis acid-base synergistic catalysis has been proposed according to our experimental results.

Cr(salophen) Complex Catalyzed Cyclic Carbonate Synthesis at Ambient Temperature And Pressure

The combination of a chromium(III) salophen bromide complex and tetrabutylammonium bromide is shown to catalyze the reaction between terminal epoxides and carbon dioxide at ambient temperature and 1 bar carbon dioxide pressure and between internal epoxides and carbon dioxide at 80 °C and 10 bar carbon dioxide pressure to form cyclic carbonates. The optimal conditions involve the use of 1.5–2.5 mol % of both the chromium(III) salophen bromide complex and tetrabutylammonium bromide and result in the formation of cyclic carbonates in 57–92% isolated yields after a reaction time of 24 h. Under these conditions, no polycarbonate formation is observed except when cyclohexene oxide is used as substrate. The reactions were found to proceed with retention of epoxide stereochemistry. A study of the reaction kinetics revealed that the chromium(III) complex and tetrabutylammonium bromide react together to form a six-coordinate anionic chromium complex which is the actual catalyst, and a catalytic cycle is proposed wh...

Selective Synthesis of 5‐Substituted N‐Aryloxazolidinones by Cycloaddition Reaction of Epoxides with Arylcarbamates Catalyzed by the Ionic Liquid BmimOAc

A selective procedure for the synthesis of 5‐substituted N‐aryloxazolidinones by the coupling of epoxides with arylcarbamates catalyzed by ionic liquids has been developed. The effects of reaction time, reactant molar ratio, amount of catalyst, and temperature were investigated. Under the optimal reaction conditions, BmimOAc exhibited efficient catalytic activity compared with other ionic liquids leading to the formation of 5‐substituted N‐aryloxazolidinones in excellent yields. In addition, chiral 5‐substituted oxazolidinones were synthesized by this procedure in good‐to‐excellent yields with enantiomeric excesses in excess of 99.9 % starting from chiral terminal epoxides. A possible reaction mechanism is discussed in accord with the results obtained by 1H NMR spectroscopy and DFT calculations, which indicate the cooperative activation by BmimOAc through the formation of hydrogen bonds with the substrates.

Halogenated meso-phenyl Mn(III) porphyrins as highly efficient catalysts for the synthesis of polycarbonates and cyclic carbonates using carbon dioxide and epoxides

Introduction of halogen electron withdrawing atoms (chloro and fluoro) in the ortho position of the aryl groups of meso-tetraphenylporphyrin manganese(III) complexes increased their activity as catalysts in the reaction of carbon dioxide with epoxides, when compared with the meso-tetraphenylporphyrin manganese(III) counterpart, even in the absence of co-catalysts. In the polymerization reaction of carbon dioxide and cyclohexene oxide, almost ten-fold increase of the TOF was observed when 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrinatomanganese(III) acetate or 5,10,15,20-tetra(2,6-difluorophenyl)porphyrinatomanganese(III) acetate complexes were used as catalysts.Under similar conditions, when terminal epoxides were used as substrates, the selective cycloaddition of CO2 with styrene oxide, epichlorohydrin, propylene oxide, and 1,2-epoxytetradecane yielded exclusively the corresponding cyclic carbonates (conversion 6–98%).