- MBA-cross-linked poly(N-vinyl-2-pyrrolidone)/ferric chloride macromolecular coordination complex as a novel and recyclable Lewis acid catalyst: Synthesis, characterization, and performance toward for regioselective ring-opening alcoholysis of epoxides
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A novel macromolecular-metal coordination complex, MBA-cross-linked PNVP/FeCl3 material was fabricated by immobilization of water intolerant ferric chloride onto the porous cross-linked poly(N-vinyl-2-pyrrolidone) carrier beads as a macromolecular ligand or carrier which was prepared by suspension free-radical copolymerization of N-vinyl-2-pyrrolidone (NVP) and N,N′-methylene bis-acrylamide (MBA) as a crosslinking agent in water. The obtained PNVP/FeCl3 was characterized by UV/vis and FT-IR spectroscopies, TGA, FE-SEM, EDX, and ICP techniques. This heterogenized version of ferric chloride is a convenient and safe alternative to highly water intolerant ferric chloride. The catalytic performance of (PNVP/FeCl3) as an efficient and recyclable polymeric Lewis acid catalyst was appropriately probed in the regio-and stereoselective nucleophilic ring opening of various epoxides with various alcohols in excellent yields with TOF up to 182.48 h?1 without generating any waste. The activity data indicate that this heterogeneous catalyst is very active and could be easily recovered, and reused at least six times without appreciable loss of activity indicating its stability under experimental conditions.
- Rahmatpour, Ali,Zamani, Maryam
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- Cellulose sulfate: An efficient heterogeneous catalyst for the ring-opening of epoxides with alcohols and anilines
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Cellulose sulfate was synthesized by esterification of α-cellulose with concentrated sulfuric acid at ?10°C in ethanol. Cellulose is mainly sulfated on 3-, 6- and 3, 6-positions of the cellulose. It acts as a heterogeneous catalyst for the ring-opening of epoxides with alcohols or anilines and the Friedel-Crafts reaction between N-benzylindole and crotonaldehyde at room temperature. Methanolysis of cyclic epoxides, styrene oxide, terminal aliphatic epoxides, and glycidyl ethers were carried out using the catalyst (0.4–6.8 mg/mmol of epoxide) and afforded the corresponding products in 53–97% isolated yields after 10 min–24 h. Cellulose sulfate was successfully recycled and reused up to 3 catalytic cycles for the ring-opening of styrene oxide with methanol.
- Chaudhary, Pooja,Deepa,Meena, Dhan Raj,Aalam, Mohd Jubair,Yadav, Geeta Devi,Singh, Surendra
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p. 1834 - 1846
(2021/05/10)
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- Dual activity of durable chiral hydroxyl-rich MOF for asymmetric catalytic reactions
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The quest to prepare of asymmetric heterogeneous catalysts with both effective Br?nsted acid sites (BASs) and Lewis acid sites is very significant challenge. Herein, we report the construction of a chiral metal-organic framework with two kinds of catalytic active sites (Lewis acid/Br?nsted acid). It contains coordinative unsaturation metal centers and chiral functional groups that have cooperation in the catalytic activity. In the synthesized CMOF, the chiral decoration of metal node was performed through the practical method: anions exchange hypothesis (post-synthetic exchange). For this aim, the elimination of framework fluorides happened by using the enantiopure auxiliary anions (L-(+)-tartrate anion (tart?)) that led to a chiral cationic MOF with eventual chemical formula [Cr3tart(H2O)2O(bdc)3]. XRD, BET, 1H NMR, SEM and EDX were employed to characterize of the present CMIL. Despite the chiral tartrate anions generate a chiral environment, they have main role in the activating of epoxide ring due to hydrogen-bonding interaction. Experiments show that the enantiopure tartrate-functionalized MIL-101(Cr) as a green asymmetric catalyst has the considerable performance in the enantioselective reactions due to chiral modified surface without remarkable loss in activity.
- Berijani, Kayhaneh,Morsali, Ali
-
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- Use of trichloroacetonitrile as a hydrogen chloride generator for ring-opening reactions of aziridines
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Regioselective ring-opening reactions of 2-aryl-N-tosylaziridines are described, in which hydrogen chloride is generated by photodegradation of trichloroacetonitrile. HCl adducts are obtained in high yields in 1,4-dioxane, whereas methanol adducts are pre
- Toda, Yasunori,Matsuda, Riki,Gomyou, Shuto,Suga, Hiroyuki
-
supporting information
p. 3825 - 3829
(2019/04/17)
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- Silylium-Catalyzed Carbon–Carbon Coupling of Alkynylsilanes with (2-Bromo-1-methoxyethyl)arenes: Alternative Approaches
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The catalytic activation of alkynylsilanes towards 2-halo-1-alkoxyalkyl arenes gives β-halo-substituted alkynes. It involves the chemoselective substitution of an alkoxide by an alkyne in the presence of a neighboring C(sp3)–Br bond in a cationic C–C bond-forming event. Two complementary protocols to accomplish this new transformation are reported. The outcome of a direct approach based on mixing the precursors with a freshly prepared solution of the active catalytic species (TMSNTf2) is compared with an alternative based on smooth release of the required silylium ions upon selective activation of the alkyne by gold(I) (JohnPhosAuNTf2). The two approaches gave satisfactory results to access this otherwise elusive alkynylation process, which furnishes 4-bromo-substituted alkynes and tolerates various functional groups.
- Rubial, Belén,Ballesteros, Alfredo,González, José M.
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p. 6194 - 6198
(2018/07/31)
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- The Synthesis of Chiral α-Aryl α-Hydroxy Carboxylic Acids via RuPHOX-Ru Catalyzed Asymmetric Hydrogenation
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A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX?Ru) catalyzed asymmetric hydrogenation of α-aryl keto acids has been successfully developed, affording the corresponding chiral α-aryl α-hydroxy carboxylic acids in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 5000 S/C) and the resulting products can be transformed to several chiral building blocks, biologically active compounds and chiral drugs. (Figure presented.).
- Guo, Huan,Li, Jing,Liu, Delong,Zhang, Wanbin
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p. 3665 - 3673
(2017/09/11)
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- Effect of Solvent Polarity on Enantioselectivity in Candida Antarctica Lipase B Catalyzed Kinetic Resolution of Primary and Secondary Alcohols
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The Candida antarctica lipase B (CAL-B) catalyzed kinetic resolution of primary and secondary alcohols via acetylation is dependent on the permittivity (ε) of the reaction solvent. For example, the enantiomeric ratio (E) vs ε plot for the acetylation of 1-(naphth-2-yl)ethanol (1) exhibits a convex shape, taking the maximum E value at a medium ε value (11.2), whereas the same plot for the acetylation of benzyl 3-hydroxybutylate (3) exhibits a concave shape, taking the minimum E value at a similar ε value (11.6). Kinetic studies reveal that the difference in shape of the E vs ε plots originates from the relative reaction rate between the enantiomers with different Michaelis constants (Km). Thus, when the enantiomer with a larger Km value in the middle ε region reacts more slowly than its antipode, the ε dependence of E exhibits a convex shape. On the other hand, when the enantiomer reacts more quickly, it exhibits a concave shape. The E vs ε plot for the acetylation of 2-methoxy-2-phenylethanol (7) exhibits a convex shape with the maximum E value (20) at ε = 14.1. The E value can be further improved to almost reach the efficiency required for industrial applications (E ≈ 30) by the addition of a nitro compound.
- Kitamoto, Yuichi,Kuruma, Yosuke,Suzuki, Kazumi,Hattori, Tetsutaro
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supporting information
p. 521 - 527
(2015/08/11)
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- Sensing remote chirality: Stereochemical determination of β-, γ-, and δ-chiral carboxylic acids
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Determining the absolute stereochemisty of small molecules bearing remote nonfunctionalizable stereocenters is a challenging task. Presented is a solution in which appropriately substituted bis(porphyrin) tweezers are used. Complexation of a suitably derivatized β-, γ-, or δ-chiral carboxylic acid to the tweezer induces a predictable helicity of the bis(porphyrin), which is detected as a bisignate Cotton Effect (ECCD). The sign of the ECCD curve is correlated with the absolute stereochemistry of the substrate based on the derived working mnemonics in a predictable manner.
- Tanasova, Marina,Anyika, Mercy,Borhan, Babak
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p. 4274 - 4278
(2015/04/14)
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- A hafnium-based metal-organic framework as an efficient and multifunctional catalyst for facile CO2 fixation and regioselective and enantioretentive epoxide activation
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Porous heterogeneous catalysts play a pivotal role in the chemical industry. Herein a new Hf-based metal-organic framework (Hf-NU-1000) incorporating Hf6 clusters is reported. It demonstrates high catalytic efficiency for the activation of epoxides, facilitating the quantitative chemical fixation of CO2 into five-membered cyclic carbonates under ambient conditions, rendering this material an excellent catalyst. As a multifunctional catalyst, Hf-NU-1000 is also efficient for other epoxide activations, leading to the regioselective and enantioretentive formation of 1,2-bifuctionalized systems via solvolytic nucleophilic ring opening.
- Beyzavi, M. Hassan,Klet, Rachel C.,Tussupbayev, Samat,Borycz, Joshua,Vermeulen, Nicolaas A.,Cramer, Christopher J.,Stoddart, J. Fraser,Hupp, Joseph T.,Farha, Omar K.
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supporting information
p. 15861 - 15864
(2015/02/19)
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- Microstructure analysis of a CO2 copolymer from styrene oxide at the diad level
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A large amount of interesting information on the alternating copolymerization of CO2 with terminal epoxides has already been reported, such as the regiochemistry of epoxide ring-opening and the stereochemistry of the carbonate unit sequence in the polymer chain. Moreover, the microstructures of CO2 copolymers from propylene oxide and cyclohexene oxide have also been well-studied. However, the microstructure of the CO2 copolymer from styrene oxide (SO), an epoxide that contains an electron-withdrawing group, has not yet been investigated. Herein, we focus on the spectroscopic assignment of the CO2 copolymer from styrene oxide at the diad level by using three kinds of model dimer compounds, that is, T-T, H-T, and H-H. By comparing the signals in the carbonyl region, we concluded that the signals at δ=154.3, 153.8, and 153.3 ppm in the 13C NMR spectrum of poly(styrene carbonate) were due to tail-to-tail, head-to-tail, and head-to-head carbonate linkages, respectively. Moreover, various isotactic and syndiotactic model compounds based on T-T, H-T, and H-H (dimers (R,R)-T-T, (S,S)-T-T, and (R,S)-T-T; (R,R)-H-T, (S,S)-H-T, and (R,S)-H-T; (R,R)-H-H, (S,S)-H-H, and (R,S)-H-H) were synthesized for the further spectroscopic assignment of stereospecific poly(styrene carbonate)s. We found that the carbonate carbon signals were sensitive towards the stereocenters on adjacent styrene oxide ring-opening units. These discoveries were found to be well-matched to the microstructures of the stereoregular poly(styrene carbonate)s that were prepared by using a multichiral CoIII-based catalyst system. T-T races: The spectroscopic assignment of regio- and stereoregular poly(styrene carbonate)s at the diad level was performed by 13C NMR studies of three kinds of model compounds, as well as their syndiotactic (R,S) and isotactic (R,R or S,S) dimers. Copyright
- Wu, Guang-Peng,Zu, Yu-Ping,Xu, Peng-Xiang,Ren, Wei-Min,Lu, Xiao-Bing
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p. 1854 - 1862
(2013/09/02)
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- Enantioselective ring-opening reaction of epoxides with MeOH catalyzed by homochiral metal-organic framework
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Two new copper metal-organic frameworks containing 2,2′-dihydroxy-1, 1′-binaphthalene-5,5′-dicarboxylic acid (5,5′-H 2BDA) and 2,2′-dihydroxy-1,1′-binaphthalene-4,4′- dicarboxylic acid (4,4′-H2BDA) have been prepared. X-ray structure determination of [Cu2(5,5′-BDA)2(H 2O)2]·MeOH·2H2O (MOF-1) and [Cu2(4,4′-BDA)2(H2O)2] ·4H2O (MOF-2) revealed similar 2D sheet structures, containing square-grid coordination networks, but differences in the stacking motif. The desolvated MOF-1 and -2 were used as Lewis acid catalysts in the asymmetric ring-opening reaction of epoxides with MeOH.
- Tanaka, Koichi,Otani, Ken-Ichi,Murase, Takanori,Nishihote, Shyota,Urbanczyk-Lipkowska, Zofia
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experimental part
p. 709 - 714
(2012/08/08)
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- Conjugate additions to alkylidene bis(sulfoxides)
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A general study on the conjugate addition of anionic nucleophiles to alkylidene bis(sulfoxides) is presented. Alkoxides gave high yielding and diastereoselective addition reactions, which could be influenced by solvents and the counteranion. Azides provided an interesting entry into sulfinyl-substituted triazoles. Organometallics, mainly copper reagents, proved also to be valuable nucleophiles, and complete inversion of the stereoselectivity was achieved in the addition reaction with the latter. Modelizations provide a rationale for the observed diastereoselectivity. Taking the Michael: Alkylidene bis(sulfoxides) are exquisite Michael acceptors toward a broad series of nucleophiles, and in most cases the reaction affords the adducts in high yields with complete diastereoselectivity.
- Brebion, Franck,Vincent, Guillaume,Chelli, Saloua,Kwasnieski, Ophelie,Najera, Francisco,Delouvrie, Benedicte,Marek, Ilan,Derat, Etienne,Goddard, Jean-Philippe,Malacria, Max,Fensterbank, Louis
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p. 1825 - 1833
(2012/02/01)
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- Asymmetric alcoholytic kinetic resolution of styrene oxide catalysed by chiral metal-organic framework crystals
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The methanolytic kinetic resolution of styrene oxide catalyzed by chiral metal-organic framework crystals afforded both 2-methoxy-2-phenylethanol and unreacted styrene oxide in good enantiomeric excesses.
- Tanaka, Koichi,Otani, Ken-Ichi
-
scheme or table
p. 2389 - 2391
(2011/01/10)
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- Lewis acid-mediated highly regioselective SN2-type ring-opening of 2-Aryl-N-tosylazetidines and aziridines by alcohols
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(Chemical Equation Presented) Lewis acid-mediated highly regioselective SN2-type ring-opening of 2-aryl-N-tosylazetidines with alcohols to afford various 1,3-amino ethers in excellent yields with good enantiomeric excess is described. Similar S
- Ghorai, Manas K.,Das, Kalpataru,Shukla, Dipti
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p. 5859 - 5862
(2008/02/09)
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- Silica sulfuric acid; an efficient and reusable catalyst for regioselective ring opening of epoxides by alcohols and water
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The nucleophilic ring opening reactions of epoxides by aliphatic alcohols and water are achieved efficiently in the presence of catalytic amounts of silica sulfuric acid with high degree of regioselectivity. The catalyst is reusable and can be applied several times without any decrease in the yield of reactions.
- Salehi, Peyman,Dabiri, Minoo,Zolfigol, Mohammad Ali,Fard, Mohammad Ali Bodaghi
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p. 1113 - 1121
(2007/10/03)
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- Iron perchlorate on silica gel as multi-purpose reagent for catalysis of closure and rupture of carbon-oxygen bond in epoxides, alcohols, and esters
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Aliphatic alcohols and water in the presence of catalytic amounts of Fe3+ ion introduced as iron(III) perchlorate on silica gel carrier perform efficient regiospecific opening of an epoxy ring. Carbon acids esterification with various type alcohols was carried out using the system Fe(ClO4)3-silica gel in dichloromethane under conditions excluding solvolysis. Acetylation and formylation of alcohols was performed by efficient transesterification with ethyl acetate and ethyl formate.
- Salechi,Khodaei,Ghareghani,Motlagh
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p. 794 - 796
(2007/10/03)
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- Enantioselective synthesis of arylmethoxyacetic acid derivatives
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The preparation of several arylmethoxyacetic acids by a sequence of asymmetric dihydroxylation and further oxidation of the resulting glycol with TEMPO/NaClO/NaClO2 is described. The scope and limitations of the reaction are discussed.
- Moreno-Dorado, F. Javier,Guerra, Francisco M.,Ortega, Maria J.,Zubia, Eva,Massanet, Guillermo M.
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p. 503 - 510
(2007/10/03)
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- Enzymatic resolution of the chiral auxiliary 2-methoxy-2-phenylethanol
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Several lipase-catalyzed processes are evaluated for the resolution of 2-methoxy-2-phenylethanol, a chiral auxiliary in the synthesis of optically active 1,4-dihydropyridines. Candida antarctica lipase B (CAL B) catalyzes the enzymatic acylation of the pr
- Monterde, Maria I.,Brieva, Rosario,Sanchez, Victor M.,Bayod, Miguel,Gotor, Vicente
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p. 1091 - 1096
(2007/10/03)
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- Iron(III) trifluoroacetate as an efficient catalyst for solvolytic and nonsolvolytic nucleophilic ring opening of epoxides
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Iron(III) trifluoroacetate was used as an efficient and nonhygroscopic catalyst for the alcoholysis, hydrolysis, and acetolysis of epoxides. The addition of chloride, bromide, iodide, and nitrate ions to epoxides to produce the corresponding 2-halo and 2-nitratoalkanols and also the conversion of epoxides to acetonides and thiiranes were also performed efficiently in the presence of this catalyst.
- Iranpoor, Nasser,Adibi, Hadi
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p. 675 - 680
(2007/10/03)
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- Ferric perchlorate: An efficient reagent for regio- and stereoselective alcoholysis and hydrolysis of epoxides
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Regio- and stereoselective ring opening reaction of epoxides is achieved efficiently by aliphatic alcohols and water in the presence of catalytic amounts of ferric perchlorate.
- Salehi, Peyman,Seddighi, Behnam,Irandoost, Mohsen,Kargar Behbahani, Farahnaz
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p. 2967 - 2973
(2007/10/03)
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- Covalent modification of subtilisin Bacillus lentus Cysteine mutants with enantiomerically pure chiral auxiliaries causes remarkable changes in activity
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Methanethiosulfonate reagents may be used to introduce virtually unlimited structural modifications in enzymes via reaction with the thiol group of cysteine. The covalent coupling of enantiomerically pure (R) and (S) chiral auxiliary methanethiosulfonate ligands to cysteine mutants of subtilisin Bacillus lentus induces spectacular changes in catalytic activity between diastereomeric enzymes. Amidase and esterase kinetic assays using a low substrate approximation were used to establish k(cat)/K(M) values for the chemically modified mutants, and up to 3-fold differences in activity were found between diastereomeric enzymes. Changing the length of the carbon chain linking the phenyl or benzyl oxazolidinone ligand to the mutant N62C by a methylene unit reverses which diastereomeric enzyme is more active. Similarly, changing from a phenyl to benzyl oxazolidinone ligand at S166C reverses which diastereomeric enzyme is more active. Chiral modifications at S166C and L217C give CMMs having both high esterase k(cat)/K(M)'s and high esterase to amidase ratios with large differences between diastereomeric enzymes. Copyright (C) 2000 Elsevier Science Ltd.
- Dickman, Michael,Jones, J. Bryan
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p. 1957 - 1968
(2007/10/03)
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- TiCl3(OTf) and TiO(TFA)2 efficient catalysts for ring opening of epoxides with alcohols, acetic acid and water
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TiCl3 (OTf) and TiO(TFA)2 can efficiently catalyze nucleophilic ring opening of epoxides in primary, secondary and tertiary alcohols, acetic acid and water to give the corresponding β-alkoxy alcohols, β-acetoxy alcohols and vicinal diols with high stereo- and regioselectivity in excellent yields. The reaction of optically active styrene oxide in MeOH with two titanium reagents was found to be highly stereospecific and afforded the corresponding S-(+)-2-methoxy-2-phenyl ethanol in 89-95% ee.
- Iranpoor, Nasser,Zeynizadeh, Behzad
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p. 1017 - 1024
(2007/10/03)
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- Enantioselective reactions of α-methoxybenzyllithium generated by t-BuLi/chiral bis(oxazoline) complex with aldehydes
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The title reaction is shown to afford the corresponding 1,2-diol monomethyl ethers in moderate-to-high levels of % ee (up to 98%) and % de (up to 90% anti), depending markedly on the aldehyde reactivity. The origin of the enantioselectivity is discussed i
- Tomooka, Katsuhiko,Wang, Lan-Fang,Komine, Nobuyuki,Nakai, Takeshi
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p. 6813 - 6816
(2007/10/03)
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- Highly efficient, regio- and stereoselective ring opening of epoxides and thiiranes with Ce(OTf)4
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Ceric triflate, Ce(OTf)4 is used as an efficient catalyst for ring opening of epoxides in the presence of alcohols, water, and acetic acid. The reactions proceed with high regio and stereoselectivity and in excellent yields. The reaction of R(+) styrene oxide with methanol occurs with excellent optical purity. Ring opening of thiiranes in alcohols, water and acetic acid followed by dimerisation to the corresponding disulfides occur efficiently in the presence of this reagent. A mild method for the preparation of dithianes from thiiranes and Ce(OTf)4 is also described.
- Iranpoor,Shekarriz,Shiriny
-
p. 347 - 366
(2007/10/03)
-
- Solid-state and solution structures of several new [LnCp′2(OR)]2 complexes (Ln=Pr, Yb) with chiral, oxygen-functionalized μ-alkoxide ligands
-
Nine novel organolanthanoid (Ln=Pr and Yb) complexes of the general type [LnCp′2(μ-OCHR(1)Z)]2 (Cp′=C5H5 or CH3C5H4, R(1)=H or Me) containing exclusively ch
- Steudel, Annette,Stehr, Jens,Siebel, Eric,Fischer, R. Dieter
-
-
- Iodine and iodine supported on polyvinylpyrrolidone as catalysts and reagents for alcoholysis, hydrolysis, and acetolysis of epoxides and thiiranes
-
Iodine and iodine supported on polyvinylpyrrolidone (betadine) have been used as catalysts for ring opening of epoxides and as reagent for ring-opening dimerization of thiiranes in alcohols, water, and acetic acid. The reactions occur with high regio-, chemo-, and stereoselectivity. The reaction of R-(+)-styrene oxide with I2 supported on PVP in methanol was found to be very stereospecific and the product was isolated in 93% ee.
- Iranpoor, Nasser,Tamami, Bahman,Niknam, Khodabakhsh
-
p. 1913 - 1919
(2007/10/03)
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- FeCl3·6H2O supported on SiO2 catalysed ring opening of epoxides with alcohols, acetic acid, water, chloride, bromide and nitrate ions
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FeCl3·6H2O absorbed on chromatographic silica gel can act as an efficient catalyst for alcoholysis, hydrolysis and acetolysis of epoxides. Methanolysis of (R)-styrene oxide proceeds with high stereospecificity and in excellent yield. This catalyst can also convert epoxides to their corresponding β-halohydrins and β-nitrato alcohols in the presence of chloride, bromide and nitrate ions respectively.
- Iranpoor, Nasser,Tarrian, Tahere,Movahedi, Zarangiz
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p. 1473 - 1476
(2007/10/03)
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- Ameliorant of cerebral circulation and optical isomer of NB-818, processes for its use
-
An ameliorant of cerebral circulation which contains 2-carbamoyloxymethyl-4-(2,3-dichlorophenyl )-6-methyl-1,4-dihydropyridine-3,5-dicarboxylic acid 3-isopropyl ester 5-methyl ester as an active ingredient.
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- Stereospecific lewis acid catalyzed methanolysis of styrene oxide
-
The methanolysis of (R)-styrene oxide catalyzed by SnCl4 has been found to proceed with complete regioselectivity with nucleophilic attack at the benzylic position, and with inversion of configuration at the benzylic carbon as the predominant stereochemical course, affording (S)-2-methoxy-2-phenylethanol (95% ee) in high yield.
- Moberg, Christina,Rakos, Laszlo,Tottie, Louise
-
p. 2191 - 2194
(2007/10/02)
-
- Synthesis, Configuration, and Calcium Modulatory Properties of Enantiomerically Pure 5-Oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylates
-
Enantiomerically pure hexahydroquinolinones of the structural type 9 were prepared by a variation of the Hantzsch synthesis in which an optically active acetoacetate served as a chiral auxiliary reagent.Determination of the de and ee values are described.The absolute configurations of the optically pure products were characterized by single-crystal X-ray analysis.The antipodes 9a and 9b exhibited calcium antagonistic activities on smooth musculature; the (S)-(-)-enantiomer 9b was the more potent compound with regard to the EC50 values which differed by a factor of 100; the intrinsic axctivity of 9b was 1.2, compared with a value of 0.54 for 9a.On the other hand, R-(+)-9a exerted positive inotropic effects on electrically stimulated atria.The cause of these effects is discussed.
- Rose, Ulrich,Draeger, Martin
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p. 2238 - 2243
(2007/10/02)
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- Oxirane Ring-Opening with Alcohol Catalyzed by Organotin Phosphate Condensates. Complete Inversion at Tertiary and Benzylic Centers
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Regio- and stereospecific ring-opening of chiral oxiranes has been effected by organotin phosphate condensates catalyst.Alcohols attack on the tertiary and benzylic positions exclusively.Despite seemingly acidic character of the catalyst in terms of regioselectivity the chiral centers are completely inverted.The new methodology is applied to synthesis of enantiomerically pure linalool and to conversion of commercially available (R)-styrene oxide into the (S)-counterpart.
- Otera, Junzo,Niibo, Yoshihisa,Nozaki, Hitosi
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p. 7625 - 7634
(2007/10/02)
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- Applications of Optically Active Aryl Cyanohydrins in the Synthesis of α-Hydroxy Aldehydes, α-Hydroxy Ketones and β-Hydroxy Amines
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Cyanohydrins, prepared in high optical purity from aryl aldehydes, have been converted into α-hydroxy aldehydes, α-hydroxy ketones and β-hydroxy amines without any racemization and frequently with good stereoselectivity for the erythro-diastereoisomer (>90percent) at the newly introduced stereogenic centre.
- Jackson, W. Roy,Jacobs, Howard A.,Jayatilake, Gamini S.,Matthews, Barry R.,Watson, Keith G.
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p. 2045 - 2062
(2007/10/02)
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- Chiral Acyl Anion and Enolonium Ion Equivalents. Asymmetric Synthesis of α-Methoxy-aldehydes
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The reaction of the lithium derivative of (+)-(S)-p-tolyl p-tolylthiomethyl sulphoxide with benzaldehyde and phenylacetaldehyde in tetrahydrofuran at -78 deg C gives, after methylation of the hydroxy-group, reduction of the sulphoxide, and h
- Colombo, Lino,Gennari, Cesare,Scolastico, Carlo,Guanti, Giuseppe,Narisano, Enrica
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p. 1278 - 1283
(2007/10/02)
-