- Mechanism and origins of enantioselectivity for [BMIM]Cl ionic liquids and ZnCl2 co-catalyzed coupling reaction of CO2 with epoxides
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Aiming at gaining more insight into the high catalytic activity of ZnCl2/[BMIM]Cl co-catalysts and elucidating the origination about the product enantioselectivity for the coupling reaction of CO2 with epoxides, a mechanistic study has been conducted by performing density functional theory calculations. The calculated results indicate a new stable complex [BMIM]ZnCl3 is probably formed via the dissociation of the in situ generated [BMIM]2ZnCl4 complex in the reaction system. This complex combined with another Cl- jointly assists the break of CO bond of propylene oxide (PO), which is the rate-determining step for the coupling reaction, and the corresponding barrier (28.0 kcal mol -1) is effectively lowered in comparison with the reaction promoted only by ZnCl2 (65.9 kcal mol-1) or [BMIM]Cl (33.1 kcal mol-1). [BMIM]+ takes part in the reaction by directly or indirectly stabilizing the intermediates and transition states via hydrogen bonding interaction with O of PO or Cl- in the reaction system. The observed product enantioselectivity probably originates from the formation of an interesting intermediate which provides nearly equal opportunities for inserted CO2 to attack the chiral carbon atom of PO on both sides and hence facilitates the formation of both R-product and S-product.
- Wang, Fang,Xu, Chuanzhi,Li, Zhen,Xia, Chungu,Chen, Jing
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Read Online
- Efficient catalytic synthesis of optically active cyclic carbonates via coupling reaction of epoxides and carbon dioxide
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Chiral Co(salen) complexes bearing the Lewis acid of group 13 can efficiently catalyze the reactions of carbon dioxide with epoxides in the presence of catalytic amounts of alkali metal salts, quaternary ammonium halide or ionic liquids. They exhibited ex
- Chen, Shu-Wei,Kawthekar, Rahul B.,Kim, Geon-Joong
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Read Online
- A chiral mixed metal-organic framework based on a Ni(saldpen) metalloligand: Synthesis, characterization and catalytic performances
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A three-dimensional (3D) chiral mixed metal-organic framework [Cd 4Cl(Ni-L)3(Ni-HL)(H2O)6(DMF)] ·4DMF (CMOF 1) based on a new enantiopure dicarboxyl-functionalized Ni(saldpen) metalloligand Ni-H2L and a novel tetranuclear cadmium cluster [Cd4Cl(CO2)7(CO2H)] has been synthesized and characterized by elemental analyses, IR and UV-vis spectra, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, powder and single-crystal X-ray diffractions. Each tetranuclear-cadmium cluster in 1 is linked by eight Ni-L ligands, and each Ni-L ligand is linked by two tetranuclear-cadmium clusters to generate a 3D framework with 1D open channels (～1.1 × 0.9 nm2) along the b-axis. Based on its good stability, permanent porosity, Lewis acid sites and moderate uptake for CO 2, 1 can be used as a self-supported heterogeneous catalyst for the synthesis of optically active propylene carbonate by asymmetric cycloaddition of CO2 with racemic propylene oxide under relatively mild conditions. The Royal Society of Chemistry 2013.
- Ren, Yanwei,Cheng, Xiaofei,Yang, Shaorong,Qi, Chaorong,Jiang, Huanfeng,Mao, Qiuping
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- Enantioselective synthesis of (R)-propylene carbonate from ethyl (S)-lactate
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We report a three-step synthesis of (R)-propylene carbonate from inexpensive, chiral ethyl (S)-lactate. The synthesis involves a borohydride ester reduction and an unusual intramolecular displacement reaction by a carbonate anion. The procedure is simple and reliable, resulting in (R)-propylene carbonate in approximately 60% overall yield with ≥98% ee. Georg Thieme Verlag Stuttgart.
- Whitaker, John M.,Ronald, Robert C.
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- Chiral (salen)CoIII catalyst for the synthesis of cyclic carbonates
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A catalyst system comprised of a CoIII(salen) complex and aLewis base is investigated for the reaction of CO2 and a variety of epoxides to form cyclic carbonates. Application of this catalyst system in the kinetic resolution of propylene oxide is also discussed.
- Paddock, Robert L.,Nguyen, Sonbinh T.
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Read Online
- Cooperative NHC-based Catalytic System Immobilised onto Carbon Materials for the Cycloaddition of CO2 to Epoxides
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New pyrene-tagged imidazolium salts and their corresponding carboxylates were synthesised and the latter tested as organocatalysts in the cycloaddition of CO2 with epoxides. The best performing organocatalyst was then non-covalently immobilised onto carbon materials (carbon nanotubes (CNTs), reduced graphene oxide (rGO) and carbon beads (CBs)) via π-π stacking interactions and their activity and recoverability in the cycloaddition reaction were studied. The heterogenised catalyst onto reduced graphene oxide (4 a@rGO) was recycled several times although a loss of activity was observed. This catalyst was also used for the transformation of a series of epoxides under mild conditions.
- Souleymanou, Myriam Y.,El-Ouahabi, Fatima,Masdeu-Bultó, Anna M.,Godard, Cyril
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Read Online
- Asymmetric Catalysis with CO2: Direct Synthesis of Optically Active Propylene Carbonate from Racemic Epoxides
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This communication describes a convenient route to optically active propylene carbonate by a catalytic kinetic resolution process resulting from the coupling reaction of CO2 and racemic epoxides using simple chiral SalenCo(III)/quaternary ammonium halide catalyst systems. Copyright
- Lu, Xiao-Bing,Liang, Bin,Zhang, Yin-Ju,Tian, Yu-Zeng,Wang, Yi-Ming,Bai, Chen-Xi,Wang, Hui,Zhang, Rong
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Read Online
- Highly regio- And stereoselective synthesis of cyclic carbonates from biomass-derived polyols: Via organocatalytic cascade reaction
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The cascade reaction of CO2, vicinal diols, and propargylic alcohol, was firstly achieved by dual Lewis base (LB) organocatalytic systems involving LB-CO2 adducts and commercially available organic amines. This methodology could overcome the chemical inertness of CO2, providing an alternative route to various functionalized five-membered cyclic carbonates in moderate to high yields under mild reaction conditions (25 °C, 1.0 atm of CO2). More importantly, this method could also be applied for facile and efficient synthesis of chiral polycyclic carbonates from biomass-derived polyols with complete configuration retention of chiral centers. This study provides an environment-friendly, scalable and cost effective protocol to construct value-added cyclic carbonates with multi-functional groups and chiral centers.
- Zhou, Hui,Zhang, Hui,Mu, Sen,Zhang, Wen-Zhen,Ren, Wei-Min,Lu, Xiao-Bing
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supporting information
p. 6335 - 6341
(2019/12/03)
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- Preparation method of high-purity tenofovir
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The invention provides a preparation method of high-purity tenofovir. The method at least comprises the following steps: (1) preparing R-propylene carbonate; (2) purifying a catalyst; (3) carrying outcondensation reaction on adenine with R-propylene carbonate; (4) carrying out etherification reaction on 9-(2-hydroxypropyl) adenine with diethyl p-toluenesulfonyloxymethylphosphonate; (5) carrying out hydrolysis reaction on tenofovir diester; and (6) refining crude tenofovir.
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Paragraph 0073; 0087-0089; 0134-0136; 0142-0144; 0150-0152
(2018/09/08)
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- Continuous-Flow Synthesis of (R)-Propylene Carbonate: An Important Intermediate in the Synthesis of Tenofovir
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(R)-Propylene carbonate is an important intermediate in the synthesis of tenofovir pro-drugs such as tenofovir alafenamide fumarate (TAF) and tenofovir diisoproyl fumarate (TDF). Independent of the pro-drug type, tenofovir presents a chiral secondary hydroxy derivative, which can be obtained directly from (R)-propylene carbonate. Herein, we report our chemo-enzymatic continuous-flow strategy towards (R)-propylene carbonate starting from a very cheap and renewable raw material, glycerol. We were able to synthesize (R)-propylene carbonate in seven continuous-flow steps, starting from glycerol, in good-to-excellent yields (66–93 %) and excellent selectivity (E > 200).
- Suveges, Nicolas S.,Rodriguez, Anderson A.,Diederichs, Carla C.,de Souza, Stefania P.,Le?o, Raquel A. C.,Miranda, Leandro S. M.,Horta, Bruno A. C.,Pedraza, Sérgio F.,de Carvalho, Otavio V.,Pais, Karla C.,Terra, José H. C.,de Souza, Rodrigo O. M. A.
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p. 2931 - 2938
(2018/06/27)
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- Chiral basket-handle porphyrin-Co complexes for the catalyzed asymmetric cycloaddition of CO2 to epoxides
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The catalytic synthesis of cyclic carbonates via the cycloaddition of CO2 to epoxides is a standard methodology for CO2 fixation. For this purpose, chiral basket-handle porphyrin-Co complexes were devised, prepared, and fully characterized by nuclear magnetic resonance, mass spectrometry, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and specific rotation. The proposed metalloporphyrin catalysts were synthesized with either 1,1′-bi-2-naphthol or L-phenylalanine, which have different chirality, and then applied to the coupling of propylene oxide and CO2 for generating chiral cyclic carbonates with good enantioselectivity under extremely mild conditions in the presence of tetrabutyl ammonium chloride as a co-catalyst. The good enantioselectivity in the cycloaddition reaction is attributed to a synergistic interplay between the chiral porphyrin catalysts and the substrate. The mechanism and enantioselectivity of the asymmetric cycloaddition reaction is discussed.
- Fu, Xiying,Jing, Xinyao,Jin, Lili,Zhang, Lilong,Zhang, Xiaofeng,Hu, Bin,Jing, Huanwang
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p. 997 - 1003
(2018/05/23)
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- Salen(Co(III)) imprisoned within pores of a metal-organic framework by post-synthetic modification and its asymmetric catalysis for CO2 fixation at room temperature
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Herein, a new preparation strategy of chiral metal-organic frameworks (CMOFs) has been demonstrated. By adsorption and then post-synthetically modified (PSM) procedures, chiral salen(Co(iii)) could be imprisoned within the cages of an MOF and remained in its free form. This is the first report on the successful application of CMOFs in heterogeneous asymmetric catalysis for coupling CO2 with epoxides to obtain optically active cyclic carbonates at room temperature.
- Chen, Danping,Luo, Ran,Li, Meiyan,Wen, Mengqi,Li, Yan,Chen, Chao,Zhang, Ning
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p. 10930 - 10933
(2017/10/11)
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- Poly(ethylene glycol)s as Ligands in Calcium-Catalyzed Cyclic Carbonate Synthesis
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Herein the use of CaI2 in combination with poly(ethylene glycol) dimethyl ether (PEG DME 500) as an efficient catalyst system for the addition of CO2 to epoxides is reported. This protocol is based on a nontoxic and abundant metal in conjunction with a polymeric ligand. Fifteen terminal epoxides were converted at room temperature to give the desired products in yields up to 99 %. Notably, this system was also effective for the synthesis of twelve challenging internal carbonates in yields up to 98 %.
- Steinbauer, Johannes,Werner, Thomas
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p. 3025 - 3029
(2017/08/18)
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- An in situ formed Ca2+-crown ether complex and its use in CO2-fixation reactions with terminal and internal epoxides
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Herein we report an efficient catalytic system based on readily available calcium iodide and 18-crown-6 ether for the atom economical addition of CO2 to epoxides. 1H NMR experiments revealed the selective in situ formation of a crown ether complex. This catalyst allows the conversion of various terminal epoxides under 1 atm CO2 pressure even at room temperature. Remarkably, a broad range of internal epoxides with various substitution patterns and substituents were smoothly converted which confirms the high efficiency and capability of the protocol. Notably, most of the internal carbonates were synthesized in high yields and diastereoselectivities of up to ≥99%. Furthermore, this system operates under solvent-free conditions without any co-catalysts e.g. onium salts.
- Steinbauer,Spannenberg,Werner
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supporting information
p. 3769 - 3779
(2017/08/26)
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- Industrialization production technology for tenofovir disoproxil fumarate
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The invention relates to an industrialization production technology for tenofovir disoproxil fumarate. The production technology comprises the following steps that firstly, R-1,2-polylene glycol, diethyl carbonate and sodium ethoxide are added into a reaction kettle; absolute ethyl alcohol and diethyl phosphite are added into the reaction kettle and stirred, paraformaldehyde and triethylamine are added after stirring is completed, after the complete reaction is achieved, anhydrous sodium sulfate is added, drying, filtering and steaming are carried out, and a steamed product is a diethyl p-toluenesulfonyloxymethylphosphonate fine product; adenine, R-propylene carbonate, DMF and NaOH are added into the reaction kettle, after the complete reaction is achieved, magnesium tert-butoxide is added, p-toluenesulfonyloxy phosphonate is dropwise added, after the complete reaction is achieved, acetic acid is added, vacuum concentration is carried out, hydrochloric acid is added, filtering is carried out, solids are filtered out and dried at the normal pressure, and a PMPA fine product is obtained. The industrialization production technology has the advantages of being high in yield and product purity, low in impurity content and capable of being completely applied to industrialization production.
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Paragraph 0011-0012
(2017/04/11)
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- A method for the synthesis of adenine derivative
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The invention discloses the technical field of medicines and particularly discloses a new prodrug, namely (R)-9-(2-(phosphonyl methoxyl)propenyl) adenine, a cyclodextrin inclusion compound of the prodrug and a non-toxic and pharmaceutically acceptable salt of the prodrug. The prodrug disclosed by the invention can be metabolized into PMPA in vivo, and has the bioavailability of about 39%, and the bioavailability of the prodrug is better than that of tenofovir disoproxil fumarate (Bis-(POC)-PMPA); and the prodrug has more excellent antiviral activity and better safety compared with the tenofovir disoproxil fumarate.
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Paragraph 0016; 0021; 0023
(2017/04/03)
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- Chiral oligomers of spiro-salencobalt(III)X for catalytic asymmetric cycloaddition of epoxides with CO2
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Several new chiral oligomers of spiro-salenCo(III)X (spiro = 1.1′-spirobiindane-7.7′-diol) complexes have been designed, synthesized, and characterized by nuclear magnetic resonance (NMR), infrared (IR), and elemental analyses, in which, the chiral spiro moieties are first introduced into a scaffold of chiral salenCo catalysts. They were used to catalyze the asymmetric cycloaddition of epoxides with carbon dioxide. Under very mild reaction conditions, a kinetic resolution of racemic epoxides with CO2 was smoothly initiated by these chiral oligomer catalysts with good enantioselectivities, which can be attributed to the match effect between chiral backbones of salen and spiro. High stability and easy recyclability are their major advantages.
- Zhu, Zhouhe,Zhang, Yuqian,Wang, Kai,Fu, Xiying,Chen, Fengjuan,Jing, Huanwang
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- Catalytic asymmetric cycloaddition of CO2 to epoxides via chiral bifunctional ionic liquids
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A series of new chiral ionic liquid catalysts composed of the N,N'-bis(salicyclidene) cyclohexene diaminatocobalt and an imidazolium salt were designed, prepared and applied for the chiral cyclic carbonate synthesis from racemic epoxides and carbon dioxide. All reactions exhibit good enantioselectivity for the chiral cyclic carbonate without polycarbonate and other by-products. The order of The order of catalytic activity toward the axial anions is OAc- > CF3CO2- > CCl3CO2- > OTs- and the order of enantioselectivity is OTs- > OAc- > CCl3CO2- > CF3CO2-.
- Duan, Shuhui,Jing, Xinyao,Li, Dandan,Jing, Huanwang
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- Lewis acid-base bifunctional aluminum-salen catalysts: synthesis of cyclic carbonates from carbon dioxide and epoxides
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Two Lewis acid-base bifunctional monometallic aluminum-salen complexes were prepared based on a new type of salen ligand with two N-methylhomopiperazine moieties at the 3,3′-position. The Al(salen) complexes proved to be efficient and recyclable homogeneous catalysts towards the organic solvent-free synthesis of cyclic carbonates from epoxides and CO2 in the absence of a co-catalyst, in which >90% yield of cyclic carbonate could be obtained under relatively mild conditions. The catalysts can be easily recovered and reused five times without significant loss of activity and selectivity. Furthermore, the Lewis acid-base cooperative activation mechanism by the bifunctional Al(salen) complexes was proposed according to experimental data.
- Ren, Yanwei,Jiang, Ou,Zeng, Hang,Mao, Qiuping,Jiang, Huanfeng
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p. 3243 - 3249
(2016/01/16)
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- NUCLEOTIDE ANALOGS
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PROBLEM TO BE SOLVED: To provide, e.g., intermediates for phosphonomethoxy nucleotide analogs, in particular, intermediates suitable for use in efficient oral delivery of such analogs. SOLUTION: Novel compounds are provided that comprise esters of antiviral phosphonomethoxy nucleotide analogs with carbonates and/or carbamates having the structure -OC(R2)2OC(O)X(R)a, The compounds are useful as intermediates for the preparation of antiviral compounds or oligonucleotides, or are useful for administration directly to patients for antiviral therapy or prophylaxis (R2 is as described in the specifications ). COPYRIGHT: (C)2015,JPOandINPIT
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Paragraph 0166; 0167; 0173
(2018/11/22)
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- CO2 Adducts of Phosphorus Ylides: Highly Active Organocatalysts for Carbon Dioxide Transformation
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A series of phosphorus ylide (P-ylide) CO2 adducts were synthesized and first used as organocatalysts for CO2 transformation. Detailed studies on the cycloaddition reaction of CO2 with terminal epoxides show that P-ylide CO2 adducts are efficient metal-free and halogen-free organocatalysts to mediate this reaction under ambient conditions (25 °C, 1 atm of CO2). More importantly, the reactions proceeded with a broad scope, high efficiency, and good functional group tolerance and the corresponding cyclic carbonate products were obtained in good to excellent yields (46-99%). Meanwhile, the kinetic study by in situ FTIR methods suggested an intermolecular cooperation effect for effectively accelerating the ring opening of terminal epoxides. Furthermore, from an investigation of the catalytic diversity of P-ylide CO2 adducts, CO2 also could be converted to functionalized cyclic α-alkylidene carbonates, oxazolidinone, and N-methylated and N-formylated amines by organocatalytic reactions.
- Zhou, Hui,Wang, Guo-Xu,Zhang, Wen-Zhen,Lu, Xiao-Bing
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p. 6773 - 6779
(2015/11/18)
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- Bifunctional porphyrin catalysts for the synthesis of cyclic carbonates from epoxides and CO2: Structural optimization and mechanistic study
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We prepared bifunctional MgII porphyrin catalysts 1 for the solvent-free synthesis of cyclic carbonates from epoxides and CO2. The activities of 1d, 1h, and 1i, which have Br-, Cl-, and I- counteranions, respectively, increased in the order 1i II porphyrin 1o with eight tetraalkylammonium bromide groups, which showed even higher catalytic activity (turnover number, 138,000; turnover frequency, 19,000 h-1). The catalytic mechanism was studied by using 1d. The yields were nearly constant at initial CO2 pressures in the 1-6 MPa range, suggesting that CO2 was not involved in the rate-determining step in this pressure range. No reaction proceeded in supercritical CO2, probably because the epoxide (into which the catalyst dissolved) dissolved in and was diluted by the supercritical CO2. Experiments with 18O-labeled CO2 and D-labeled epoxide suggested that the catalytic cycle involved initial nucleophilic attack of Br- on the less hindered side of the epoxide to generate an oxyanion, which underwent CO2 insertion to afford a CO2 adduct; subsequent intramolecular ring closure formed the cyclic carbonate and regenerated the catalyst. Density functional theory calculations gave results consistent with the experimental results, revealing that the quaternary ammonium cation underwent conformational changes that stabilized various anionic species generated during the catalytic cycle. The high activity of 1d and 1o was due to the cooperative action of the MgII and Br- and a conformational change (induced-fit) of the quaternary ammonium cation.
- Ema, Tadashi,Miyazaki, Yuki,Shimonishi, Junta,Maeda, Chihiro,Hasegawa, Jun-Ya
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p. 15270 - 15279
(2015/01/09)
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- Bifunctional aluminum catalyst for CO2 fixation: Regioselective ring opening of three-membered heterocyclic compounds
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Regioselective ring opening of three-membered heterocyclic compounds (epoxides or N-substituted aziridines) at various temperatures was observed in coupling reactions with CO2 by the use of an aluminum - salen catalyst in conjunction with intramolecular quaternary ammonium salts as cocatalysts, affording the corresponding five-membered cyclic products with complete configuration retention at the methine carbon. Notably, this bifunctional aluminum-based catalyst exhibited nearly 100% regioselectivity for the ring opening at the methylene C-O bond for various terminal epoxides. This was true for those bearing an electron-withdrawing group, such as styrene oxide or epichlorohydrin, thereby affording the synthesis of various enantiopure cyclic carbonates that have previously been obtained only rarely by other methods. An intramolecular cooperative catalysis is suggested to contribute to the high activity and excellent stereochemistry control observed. Surprisingly, the highly selective ring opening at the methine carbon of N-substituted aziridines was found in the coupling with CO2, predominantly giving 5-substituted oxazolininones with retention of configuration as a result of double inversion at the methine carbon. (Chemical Equation Presented).
- Ren, Wei-Min,Liu, Ye,Lu, Xiao-Bing
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p. 9771 - 9777
(2015/02/19)
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- Asymmetric cycloaddition of CO2 and an epoxide using recyclable bifunctional polymeric Co(iii) salen complexes under mild conditions
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Bifunctional polymeric Co(iii) salen complexes 1a-g derived from (1R,2R)-(-)-1,2-diaminocyclohexane and a triazine-piperazine core were synthesized and screened for the asymmetric cycloaddition reaction of CO 2 and an epoxide under mild conditions. A moderate Krel value of 11.2 for the product propylene carbonate (ee = 74%) was obtained with catalyst 1e which does not require any external base as the co-catalyst. The polymeric Co(iii)-CCl3COO (1e) was efficiently recycled 10 times without any significant loss in activity under the present reaction conditions.
- Roy, Tamal,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
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p. 2661 - 2667
(2013/09/24)
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- Chiral metal-containing ionic liquid: Synthesis and applications in the enantioselective cycloaddition of carbon dioxide to epoxides
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A series of novel chiral metal-containing ionic liquids (CMILs) consisting of the cation of crown ether-chelated potassium/sodium and the anion of chiral amino acids were designed and synthesized. These new CMILs were used to catalyze the enantioselective cycloaddition of epoxides and carbon dioxide incorporating with the salenCo(OOCCCl3) to generate corresponding chiral cyclic carbonates under mild conditions. These new catalysts can be recycled at least five times without significant loss of activity and enantioselectivity.
- Song, Yingying,Jin, Qianru,Zhang, Suling,Jing, Huanwang,Zhu, Qianqian
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scheme or table
p. 1044 - 1050
(2012/04/04)
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- N-Heterocyclic carbene functionalized MCM-41 as an efficient catalyst for chemical fixation of carbon dioxide
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N-Heterocyclic carbene (NHC) functionalized MCM-41 was synthesized by reacting 1,3-bis-(4-allyl-2,6-diisopropylphenyl) imidazolium chloride with MCM-41 using 3-mercaptopropyltrimethoxysilane as silane coupling agent, and its CO2 adduct (designated as MCM-41-IPr-CO2) was further synthesized by the reaction with CO2. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the reversible CO2 capture-release ability of MCM-41-NHC. MCM-41-IPr-CO2 adduct proved to be an efficient heterogeneous catalyst for the cycloaddition of CO2 to epoxides or aziridines with excellent regioselectivity under mild conditions. Moreover, the catalyst could be recovered easily through a simple filtration process and reused multiple times without obvious loss in activity, owing to CO2 as protective group for effectively stabilizing the NHC anchored on MCM-41. The Royal Society of Chemistry.
- Zhou, Hui,Wang, Yi-Ming,Zhang, Wen-Zhen,Qu, Jing-Ping,Lu, Xiao-Bing
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experimental part
p. 644 - 650
(2011/05/02)
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- Nucleotide Analogue Prodrug and the Preparation Thereof
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(R)-9-[2-bis[pivaloyloxymeihoxy]phosphinoylmethoxypropyl]adenine (being abbreviated bis-POMPMPA, TD), the derivative and the use thereof. Also including the synthetic process of TD and the procedure for manufacturing solid TD, as well as the composition containing TD and the procedure for manufacturing the composition.
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Page/Page column 13
(2010/09/05)
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- Catalytic Asymmetric Cycloaddition of Carbon Dioxide and Propylene Oxide Using Novel Chiral Polymers of BINOL-SalenCobalt(III) Salts
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Four new chiral polymers of BINOLSalen-cobalt(III) salt complexes have been designed, synthesized and applied to the direct fabrication of chiral propylene carbonate from racemic propylene oxide. The (R/S)-polymer catalyst 2 and (S/R)-polymer catalyst 4 exhibit better enantioselectivity than the (R/R)-polymer catalyst 1 and the (S/S)-polymer catalyst 3 and have been recovered and reused more than ten times without loss of activity and enantioselectivity.
- Yan, Peng,Jing, Huanwang
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experimental part
p. 1325 - 1332
(2009/12/24)
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- Chiral ionic liquids improved the asymmetric cycloaddition of CO 2 to epoxides
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The new catalyst system of chiral SalenCo(OAc)/chiral ionic liquid was developed to catalyze the asymmetric cycloaddition reaction of CO2 and epoxides yielding the chiral cyclic carbonates. The synergistic effect between them is discussed.
- Zhang, Suling,Huang, Yongzhong,Jing, Huanwang,Yao, Weixuan,Yan, Peng
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supporting information; experimental part
p. 935 - 938
(2010/04/23)
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- METHOD OF PRODUCTION OF ENANTIOMER-ENRICHED ALKYLENE CARBONATES
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The invention relates to a method of production of enantiomer-enriched alkylene carbonates (I), in particular (R)-propylene carbonate (I), by enantioselective enzymatic reduction of an O- substituted hydroxyacetone of type (II) and subsequent cyclization of the alcohol formed of type (III) and compounds of formula (III) and their regioisomers (IV).
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Page/Page column 28
(2008/06/13)
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- Chiral catalysts for the asymmetric cycloaddition of carbon dioxide with epoxides
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Several chiral BINADCo(III)X (BINAD = Bis(1,1′-2-hydroxy-2′-alkoxy-3-naphthylidene)-1,2-cyclohexanediamine, X = OAc, CF3CO2, CCl3CO2, OTs, p-NO2PhCO2) complexes were synthesized and used to
- Jin, Lili,Huang, Yongzhong,Jing, Huanwang,Chang, Tao,Yan, Peng
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p. 1947 - 1953
(2008/12/22)
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- Intramolecularly two-centered cooperation catalysis for the synthesis of cyclic carbonates from CO2 and epoxides
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A catalyst system containing an electrophilic center and a sterically hindered nucleophilic center in one molecule was applied to the cycloaddition reaction of CO2 and epoxides. This intramolecularly two-centered cooperation catalyst showed activity even at a high [epoxide]/[catalyst] ratio up to 50 000 under mild conditions such as solvent-free, ambient temperature, and low CO2 pressure. The reaction of CO2 with (S)-propylene oxide at 80 °C in the presence of the bifunctional catalyst gives (S)-propylene carbonate in 96% ee with retention of stereochemistry.
- Zhang, Xiang,Jia, Yin-Bao,Lu, Xiao-Bing,Li, Bo,Wang, Hui,Sun, Li-Cheng
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body text
p. 6589 - 6592
(2009/04/06)
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- CO2 adducts of N-heterocyclic carbenes: Thermal stability and catalytic activity toward the coupling of CO2 with epoxides
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(Chemical Equation Presented) Thermal stability of CO2 adducts of N-heterocyclic carbenes (NHCs) was studied by means of in situ FTIR method with monitoring of the ν(CO2) region of the infrared spectra under various conditions. 1,3-Bis(2,6-diisopropylphenyl)imidazolinium-2-carboxylate (SIPr-CO2) shows higher thermal stability compared with 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate (IPr-CO2). The presence of free CO2 can significantly inhibit the decomposition of NHC-CO2 adducts, while the addition of an epoxide such as propylene oxide has a negative effect on stabilizing these adducts. As zwitterionic compounds, NHC-CO2 adducts were also proved to be effective organic catalysts for the coupling reaction of CO2 and epoxides to afford cyclic carbonates, for which a possible mechanism was proposed. Among these NHC-CO2 adducts, the relatively unstable IPr-CO2 exhibits the highest catalytic activity. The presence of an electrophile such as SalenAlEt could greatly improve the catalytic activity of IPr-CO2 due to intermolecular cooperative catalysis of the binary components.
- Zhou, Hui,Zhang, Wen-Zhen,Liu, Cui-Hua,Qu, Jing-Ping,Lu, Xiao-Bing
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p. 8039 - 8044
(2008/12/22)
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- Catalytic asymmetric addition of carbon dioxide to propylene oxide with unprecedented enantioselectivity
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New chiral catalyst systems were developed for the reaction of carbon dioxide with propylene oxide (PO) at atmospheric pressure to generate enantiomerically enriched propylene carbonate (PC). The best selectivity was achieved with a CoIII(salen)-trifluoroacetyl complex and bis-(triphenylphosphoranylidene)ammonium fluoride (PPN+F-) as catalysts, affording PC in 40% yield and 83% ee (selectivity factor = 19). In addition, PC was prepared for the first time by kinetic resolution of PO with tetrabutylammonium methyl carbonate (TBAMC, nBu4N +-OOCOMe). With TBAMC as "activated CO2", up to 71% ee was obtained.
- Berkessel, Albrecht,Brandenburg, Marc
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p. 4401 - 4404
(2007/10/03)
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- Nucleotide analog composition and synthesis method
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The invention relates to a composition comprising a solution of 9-[2-(phosphono-methoxy)propyl]adenine (PMPA) at a pH of about 2.7 ― 3.5 wherein the solution has less than about 0.1 g/ml (R, S)-PMPA and wherein about 90 ― 94 % of the PMPA is in the (R) configuration.
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- Process for producing cyclic carbonic esters
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Reacting a diol (1) with a carbonic ester (2) to produce a cyclic carbonic ester (3) using a salt of a weak acid with an alkaline metal or alkaline earth metal as a catalyst. The diol (1) contains diols having an asymmetric carbon atom. The reaction mixture is neutralized and distilled to obtain a cyclic carbonic ester. Cyclic carbonic esters are produced using an easily accessible and easy to handle reactant, with good yield and under mild and moderate conditions.
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- Practical synthesis of the anti-HIV drug, PMPA
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The anti-HIV nucleotide analogue PMPA can be prepared on a kilogram-scale by a three step sequence: i) condensation of adenine with (R)-propylene carbonate, ii) alkylation of the resulting (R)-9- (2-hydroxypropyl)adenine with diethyl p- toluenesulfonyloxymethanephosphonate using lithium tert-butoxide and iii) cleavage of the phosphonate ester functionalities with bromotrimethylsilane.
- Schultze, Lisa M.,Chapman, Harlan H.,Dubree, Nathan J. P.,Jones, Robert J.,Kent, Kenneth M.,Lee, Thomas T.,Louie, Michael S.,Postich, Michael J.,Prisbe, Ernest J.,Rohloff, John C.,Yu, Richard H.
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p. 1853 - 1856
(2007/10/03)
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