- A phosphonium ylide as a visible light organophotoredox catalyst
-
A phosphonium ylide-based visible light organophotoredox catalyst has been designed and successfully applied to halohydrin synthesis using trichloroacetonitrile and epoxides. An oxidative quenching cycle by the ylide catalyst was established, which was confirmed by experimental mechanistic studies.
- Toda, Yasunori,Tanaka, Katsumi,Matsuda, Riki,Sakamoto, Tomoyuki,Katsumi, Shiho,Shimizu, Masahiro,Ito, Fuyuki,Suga, Hiroyuki
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p. 3591 - 3594
(2021/04/14)
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- Visible-light-triggered Catalytic Halohydrin Synthesis from Epoxides and Trichloroacetonitrile by Copper and Iron Salts
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Preparation of vicinal halohydrins, in which copper or iron chlorides catalyze the ring-opening reaction of epoxides with visible light effectively, is described. The use of trichloroacetonitrile as a halogen source enables catalytic HCl generation under the mild conditions. This method can also be applied to the aziridine ring-opening reaction.
- Toda, Yasunori,Tanaka, Katsumi,Matsuda, Riki,Suga, Hiroyuki
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p. 1469 - 1471
(2019/12/02)
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- Synthesis, Characterization, and Evaluation of Surface and Thermal Properties and Cytotoxicity of 2-Hydroxy-3-Phenoxypropyl Imidazolium Bola-Type Gemini Amphiphiles
-
A library of imidazolium-based gemini cationic bola amphiphiles was synthesized using a regioselective ring-opening reaction of glycidyl phenyl ether with imidazole under solvent-free conditions. The corresponding hexafluorophosphate (PF6?) and tetrafluoroborate (BF4?) counterion-containing amphiphiles were also synthesized and characterized using nuclear magnetic resonance (NMR) and mass spectroscopy. The micellar and interfacial parameters like the critical micelle concentration (CMC), surface pressure at the CMC (Пcmc), surface tension at CMC (γcmc), counterion binding (β), maximum surface excess concentration (Γmax), minimum area per molecule (Amin), standard free energy of micellization (ΔG0mic) and adsorption (ΔG0ads), and Kraft temperature were evaluated using surface tension and conductometry methods in aqueous solution as well as in buffer solution. Dynamic light scattering (DLS) was used to determine the size of the micelles formed in the aqueous solution. Cytotoxicity tests were carried out on the C6 glioma cancerous brain cell line using the MTT assay (3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide) to evaluate the IC50 value of all the synthesized amphiphiles. Thermal stability of these amphiphiles was also evaluated using a thermal gravimetric analyzer (TGA). Economic way of synthesis, moderate thermal stability, a low value of CMC, and cytotoxicity of these amphiphiles will inspire new research in the field of nanobiotechnology and pharmaceutical industries.
- Aggarwal, Rajni,Singh, Sukhprit,Saini, Vedangana,Kaur, Gurcharan
-
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- Organocatalytic Regioselective Chlorosilylation of Oxirane Derivatives: Mild and Effective Insertion of Bulky Silyl Chloride by Using 4-Methoxypyridine N-Oxide
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The highly regioselective organocatalytic chlorosilylation of oxirane derivatives using bulky silyl reagents such as (tert-butyl)diphenylsilyl chloride (TBDPSCl) or triphenylsilyl chloride (Ph3SiCl) was developed. The reaction was effectively catalyzed with 4-methoxypyridine N-oxide in the presence of sodium sulfate (Na2SO4). Several silylated halohydrins were obtained with complete regioselectivity and the reaction was applied to the synthesis of carvedilol. (Figure presented.) .
- Yoshida, Keisuke,Suzuki, Hina,Inoue, Hiroki,Matsui, Kohei,Fujino, Yuta,Kanoko, Yohei,Itatsu, Yukihiro,Takao, Ken-Ichi
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p. 1886 - 1891
(2016/07/06)
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- Trihaloisocyanuric Acid/Triphenylphosphine: An Efficient System for Regioselective Conversion of Epoxides into Vicinal Halohydrins and Vicinal Dihalides under Mild Conditions
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A new synthetic method has been developed for the regioselective conversion of epoxides to vicinal chloro-/bromohydrins and vicinal dihalides by reaction with the system trihaloisocyanuric acid/tri?phenylphosphine in acetonitrile under mild and neutral conditions. The reactions proceed smoothly in high yield at room temperature and at reflux, respectively, over a short time.
- De Andrade, Vitor S. C.,De Mattos, Marcio C. S.
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p. 1381 - 1388
(2016/05/19)
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- Highly enantioselective CALB-catalyzed kinetic resolution of building blocks for β-blocker atenolol
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Both enantiomers of 4-(3-chloro-2-hydroxypropoxy)phenyl)acetamide has been synthesized in 98.5–99% enantiomeric excess by use of lipase B from Candida antarctica as catalyst. The R-alcohol is a building block for the cardioselective β-blocker (S)-atenolol ((S)-2-(4-(2-hydroxy-3-(isopropylamino)propoxy)phenyl)acetamide. Performing kinetic resolutions of 3-chloro-1-phenoxy-2-propanol and 3-bromo-1-phenoxy-2-propanol with vinyl butanoate as acyl donor and the same CALB enzyme, but a different preparation, showed higher E-values than previously reported.
- Lund, Ingvild T.,B?ckmann, P?l L.,Jacobsen, Elisabeth E.
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p. 7288 - 7292
(2016/10/26)
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- Continuous and convergent access to vicinyl amino alcohols
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Five active pharmaceutical ingredients (APIs) containing the vicinyl amino alcohol moiety were synthesized using a convergent chemical assembly system. The continuous system is composed of four flow reaction modules: biphasic oxidation, Corey-Chaykovsky epoxidation, phenol alkylation, and epoxide aminolysis. Judicious choice of reagents and module order allowed for two classes of β-amino alcohols, aryl and aryloxy, to be synthesized in good (27-69%) overall yields.
- Nobuta, Tomoya,Xiao, Guozhi,Ghislieri, Diego,Gilmore, Kerry,Seeberger, Peter H.
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p. 15133 - 15136
(2015/10/12)
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- Reinvestigation of a Catalytic, Enantioselective Alkene Dibromination and Chlorohydroxylation
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Attempts to reproduce eight, putative, enantioselective dibromination and chlorohydroxylation reactions from oft-cited literature studies are described. The reactions were performed with full fidelity to the original report wherever possible. Analysis of the enantiomeric composition was performed by chiral stationary phase HPLC or SFC (CSP-HPLC or CSP-SFC), as opposed to the original report, which used chiral shift reagent NMR spectroscopy. After careful study, the reported levels of enantioselectivity were found to be incorrect. Possible explanations for the false positive results are discussed.
- Denmark, Scott E.,Carson, Nessa
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supporting information
p. 5728 - 5731
(2015/12/11)
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- 1,3,2,4-diazadiphosphetidine-based phosphazane oligomers as source of P(III) atom economy reagents: Conversion of epoxides to vic -haloalcohols, vic -dihalides, and alkenes in the presence of halogen sources
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1,3,2,4-Diazadiphosphetidines (P1-P3), as easily prepared, stable, and heterogeneous P(III) compounds, were used for the efficient conversion of epoxides to vic-halohydrins, vic-dihalides, or alkenes in the presence of different halogen sources in CH3CN. Of these phosphazanes, P3 is most suitable and contains 4 phosphorous atoms with the advantage of having greater atom economy and its phosphorus oxide byproduct can be easily separated from the reaction mixture by simple filtration. The nitrogen atoms in this molecule can also act as acid scavengers in the reaction.
- Iranpoor, Nasser,Firouzabadi, Habib,Etemadidavan, Elham
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p. 1165 - 1173
(2014/10/16)
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- Tuning of the electronic properties of a cyclopentadienylruthenium catalyst to match racemization of electron-rich and electron-deficient alcohols
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The synthesis of a new series of cyclopentadienylruthenium catalysts with varying electronic properties and their application in racemization of secondary alcohols are described. These racemizations involve two key steps: 1) β-hydride elimination (dehydrogenation) and 2) re-addition of the hydride to the intermediate ketone. The results obtained confirm our previous theory that the electronic properties of the substrate determine which of these two steps is rate determining. For an electron-deficient alcohol the rate-determining step is the β-hydride elimination (dehydrogenation), whereas for an electron-rich alcohol the re-addition of the hydride becomes the rate-determining step. By matching the electronic properties of the catalyst with the electronic properties of the alcohol, we have now shown that a dramatic increase in racemization rate can be obtained. For example, electron-deficient alcohol 15 racemized 30 times faster with electron-deficient catalyst 6 than with the unmodified standard catalyst 4. The application of these protocols will extend the scope of cyclopentadienylruthenium catalysts in racemization and dynamic kinetic resolution. Copyright
- Verho, Oscar,Johnston, Eric V.,Karlsson, Erik,Baeckvall, Jan-E.
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supporting information; experimental part
p. 11216 - 11222
(2011/11/05)
-
- Protective opening of epoxide using pivaloyl halides under catalyst-free conditions
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An efficient and environmentally benign protocol for protective opening of epoxide (POE) with pivaloyl halides in solvent-free conditions and in aqueous media under catalyst-free conditions has been developed. The green reaction conditions, simple work-up procedures, high yields and broad scope of the reaction illustrate the good synthetic utility of this method. The key advantages of the reaction are regioselectivity and reconvertability of products into their prior epoxides in the presence of mild reaction conditions.
- Rao, Chitturi Bhujanga,Rao, Dasireddi Chandra,Venkateswara, Mallem,Venkateswarlu, Yenamandra
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supporting information; experimental part
p. 2704 - 2707
(2011/12/05)
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- Solvent-free, efficient, and high regioselective conversion of epoxides to symmetrical and unsymmetrical vic-dihalides using chlorodiphenylphosphine and n-halosuccinimides
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A new method is described for the efficient and high regioselective conversion of epoxides to symmetrical and unsymmetrical vic-dihalides in high yields using chlorodiphenylphosphine and N-halosuccinimides under solvent-free and neutral conditions and at room temperature. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Aghapour, Ghasem,Afzali, Asieh
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scheme or table
p. 598 - 605
(2011/05/15)
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- Facile, high regio- And chemoselective conversion of epoxides to β-chlorohydrins using chlorodiphenylphosphine under solvent-free conditions
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A new method is described for the mild and high regioselective conversion of epoxides to β-chlcrohydrins in high yields even in the presence of alcohols, carboxylic acids, oximes, amides, thiols and tetrahydropyranyl ethers using chlorodiphenylphosphine (ClPPh2) under solvent-free and neutral conditions at room temperature and in short reaction times. In addition, some other functional groups such as carbon-carbon double bonds, ester groups and also phenyl ring that are present in the epoxide molecules remain intact in this method.
- Aghapour, Ghasem,Afzali, Asieh,Salek, Fahimeh
-
body text
p. 231 - 236
(2009/12/03)
-
- Convenient synthesis of chlorohydrins from epoxides using zinc oxide: Application to 5,6-epoxysitosterol
-
Efficient synthesis of protected and unprotected chlorohydrins has been achieved by ring opening of epoxides with acetyl/benzoyl chloride and TMSCl using a catalytic amount of ZnO as a reusable catalyst. The applicability of ZnO is further extended by performing the cleavage of the natural product 5,6-epoxysitosterol with acetyl chloride.
- Moghaddam, Firouz Matloubi,Saeidian, Hamdollah,Mirjafary, Zohreh,Javan, Marjan Jebeli,Farimani, Mehdi Moridi,Seirafi, Marjan
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experimental part
p. 157 - 163
(2009/09/30)
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- Biocatalytic cascade for the synthesis of enantiopure β-azidoalcohols and β-hydroxynitriles
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A three-step, two-enzyme, one-pot reaction sequence starting from prochiral a-chloroketones leading to enantiopure (3- azidoalcohols and (3-hydroxynitriles is described. Asymmetric bioreduction of a-chloroketones by hydrogen transfer catalysed by an alcohol dehydrogenase (ADH) established the stereogenic centre in the first step to furnish enantiopure chlorohydrin intermediates. Subsequent biocatalysed ring closure to the epoxide and nucleophilic ring opening with azide, N3-, or cyanide, CN-, both catalysed by a nonselective halohydrin dehalogenase (Hhe) proceeded with full retention of configuration to give enantiopure (-azidoalcohols and (3-hydroxynitriles, respectively. Both enantiomers of various optically pure (-azidoalcohols and (-hydroxynitriles were synthesised.
- Schrittwieser, Joerg H.,Lavandera, Ivan,Seisser, Birgit,Mautner, Barbara,Kroutil, Wolfgang
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supporting information; experimental part
p. 2293 - 2298
(2009/08/17)
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- Highly efficient route for enantioselective preparation of chlorohydrins via dynamic kinetic resolution
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(Equation Presented) Dynamic kinetic resolution (DKR) of various aromatic chlorohydrins with the use of Pseudomonas cepacia lipase (PS-C "Amano" II) and ruthenium catalyst 1 afforded chlorohydrin acetates in high yields and high enantiomeric excesses. These optically pure chlorohydrin acetates are useful synthetic intermediates and can be transformed to a range of important chiral compounds.
- Traeft, Annika,Bogar, Krisztian,Warner, Madeleine,Baeckvall, Jan-E.
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supporting information; experimental part
p. 4807 - 4810
(2009/05/31)
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- Reaction of phenyl glycidyl ether with some heterocycles
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The respective hydroxypropyl phenyl ethers were obtained by the reaction of 5,5-dimethylhydantoin, morpholine, benzotriazole, benzimidazole, pyrrolidone, and phthalimide with phenyl glycidyl ether. 8-(2-Hydroxy-3-phenoxy) quinoline was synthesized by O-alkylation.
- Mesropyan,Ambartsumyan,Avetisyan,Galstyan
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experimental part
p. 650 - 653
(2009/04/06)
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- Zirconium-promoted epoxide rearrangement-alkynylation sequence
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(Chemical Equation Presented) Additions of terminal alkynes to electrophiles are important transformations in organic chemistry. Generally, activated terminal alkynes react with epoxides in an SN2 fashion to form homopropargylic alcohols. We have developed a new synthetic method to form propargylic alcohols from epoxides and terminal alkynes via 1,2-shifts. This method involves cationic zirconium acetylides as both the activator of epoxides and nucleophiles. Due to the mild conditions to pre-activate alkynes with silver nitrate, this synthetic method is useful for both electron-rich and electron-deficient alkynes with other acid- and base-sensitive functional groups.
- Albert, Brian J.,Koide, Kazunori
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p. 1093 - 1098
(2008/09/18)
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- Asymmetric reduction of α-thiocyanatoketones by Saccharomyces cerevisiae and Mortierella isabellina-a new route to optically active thiiranes
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A simple method for the preparation of optically active 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-oles from racemic 1-chloro-3-aryloxy- and 1-chloro-3-arylsulphanyl-2-propanols via 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-ones has been developed. The enantiomerically enriched β-hydroxythiocyanates were obtained by a microbiological reduction of the thiocyanatoketones with Saccharomyces cerevisiae or Mortierella isabellina and subsequently converted into optically active thiiranes on treatment with a lithium hydroxide solution.
- Lukowska, Edyta,Plenkiewicz, Jan
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p. 1202 - 1209
(2008/02/05)
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- Synthesis of β-chlorohydrins in water
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2,4,6-Trichloro-1,3,5-triazine (TCT, cyanuric chloride) was found to mediate the regio- and stereoselective ring opening of epoxides in H 2O in the presence of morpholine at room temperature to afford the corresponding β-chlorohydrins in excellent yields (Table). The transformation is very simple, fast, efficient, and ecologically beneficial.
- Das, Biswanath,Venkateswarlu, Katta,Krishnaiah, Maddeboina
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p. 149 - 152
(2007/10/03)
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- Regio- and stereoselective ring opening of epoxides and aziridines using zirconyl chloride: An efficient approach for the synthesis of β-chlorohydrins and β-chloroamines
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Zirconyl chloride mediated regio- and stereoselective ring opening of epoxides and aziridines at room temperature affords the corresponding β-chlorohydrins and β-chloroamines, respectively in high yields. Copyright
- Das, Biswanath,Krishnaiah, Maddeboina,Venkateswarlu, Katta
-
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- Improvement and simplification of synthesis of 3-aryloxy-1,2-epoxypropanes using solvent-free conditions and microwave irradiations. Relation with medium effects and reaction mechanism
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Some 3-aryloxy-1,2-epoxypropanes, interesting as potential synthons in β-adrenergic receptor antagonists preparation, were obtained in excellent yields (65-96% within 2-17 min) by microwave activation (monomode system) using solid-liquid solvent-free phase transfer catalysis (PTC). The best results for the O-alkylation of some phenols with epichlorohydrin were obtained using TBAB and NaOH/K2CO3 (1:4 mol/mol) as phase transfer catalyst and more acceptable basic system, respectively. These new procedure is compared with classical methods. Significant specific microwave effect (non-purely thermal) was evidenced in all cases. They were discussed in terms of reaction medium and mechanism, taking into account the variations in polarity of the systems.
- Pchelka, Beata K.,Loupy, Andre,Petit, Alain
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p. 10968 - 10979
(2007/10/03)
-
- Regioselective conversion of unsymmetrical terminal epoxides into vicinal chlorohydrins using dimethoxyboron chloride
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A highly regioselective synthesis of chlorohydrins by chlorinative cleavage of unsymmetrical epoxides utilizing dimethoxyboron chloride is described. Except for styrene oxide, all the terminal epoxides were regioselectively cleaved following a predominantly SN2-type reaction pathway favouring the formation of primary chlorides. In the case of styrene oxide, a benzylic epoxide, (MeO)2BCl transfers the chlorine at the benzylic position, by following an apparent SN1-type mechanism. CSIRO 2006.
- Roy, Chandra D.
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p. 834 - 836
(2007/10/03)
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- Regioselective synthesis of vic-halo alcohols and symmetrical or unsymmetrical vic-dihalides from epoxides using triphenylphosphine -N-halo imides
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A simple, novel, and highly regioselective cleavage of epoxides into vicinal halo alcohols and symmetrical or unsymmetrical dihalides is described using different stoichiometries of triphenylphosphine (PPh3) and N-halo succinimide (NXS) or N-halo saccharine (NXSac).
- Iranpoor, Nasser,Firouzabadi, Habib,Azadi, Roya,Ebrahimzadeh, Farzaneh
-
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- Silphos [PCl3-n (SiO2)n]: A heterogeneous phosphine reagent for the regioselective synthesis of vic-haloalcohols
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Silphos as a silica-based phosphine [PCl3-n (SiO 2)n] provides a practical method for the conversion of epoxides to vic-haloalcohols in the presence of molecular bromine, iodine, or N-halosuccinimides (NXS, X = Cl, Br, I) in CH3CN or under solvent-free conditions at r.t. The simple filtration of heterogeneous Silphos oxide from the reaction mixture affords the pure vic-haloalcohols with excellent yields. Copyright Taylor & Francis Group, LLC.
- Iranpoor, Nasser,Firouzabadi, Habib,Jamalian, Arezu
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p. 2615 - 2621
(2007/10/03)
-
- "Metal ion electrophilic catalysis" in ring-opening reactions of 1,2-epoxides by metal halides in ionic liquids
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Metal ion electrophilic catalysis (Li+ > Na+ ? K+) has been found in ring-opening reactions of 1,2-epoxides 1-5 by metal halides MHa1 in ionic liquids. The results have been rationalized on the basis of a transition state where the cation M+ stabilizes the negative charge developing on the oxygen atom of the oxirane ring while favoring the nucleophilic attack at the adjacent carbon by the ion-paired anion Hal -. Georg Thieme Verlag Stuttgart.
- Betti, Cecilia,Landini, Dario,Maia, Angelamaria
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p. 1335 - 1338
(2007/10/03)
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- Conversion of epoxides to β-chlorohydrins with thionyl chloride and β-cyclodextrin in water
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Several epoxides are efficiently converted to the corresponding β-chlorohydrins in impressive yields with thionyl chloride in the presence of β-cyclodextrin using water as solvent at room temperature. Copyright Taylor & Francis, Inc.
- Surendra,Srilakshmi Krishnaveni,Nageswar,Rama Rao
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p. 2195 - 2201
(2007/10/03)
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- Ionic liquid as reagent. A green procedure for the regioselective conversion of epoxides to vicinal-halohydrins using [AcMIm]X under catalyst- and solvent-free conditions
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A variety of structurally diverse epoxides undergo facile cleavages by ionic liquid, [AcMIm]X without any catalyst and solvent to produce the corresponding vicinal halohydrins in high yields. The cleavages are considerably fast and highly regioselective.
- Ranu, Brindaban C.,Banerjee, Subhash
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p. 4517 - 4519
(2007/10/03)
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- Efficient synthesis of chlorohydrins: Ionic liquid promoted ring-opening reaction of epoxides and TMSCl
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The environmentally benign, highly efficient synthesis of chlorohydrins by cleavage of epoxides using TMSCl in ionic liquid, bmimPF6, has been studied.
- Xu, Li-Wen,Li, Lyi,Xia, Chun-Gu,Zhao, Pei-Qing
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p. 2435 - 2438
(2007/10/03)
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- Facile and regioselective conversion of epoxides into β-chlorohydrins using ZrCl4
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Epoxides were efficiently converted into the corresponding β-chlorohydrins in good yields by treatment with ZrCl4 in acetonitrile.
- Smitha,Reddy, Ch. Sanjeeva
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p. 300 - 301
(2007/10/03)
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- Green protocol for the synthesis of vicinal-halohydrins from oxiranes using the [Bmim]PF6/LiX reagent system
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Epoxides undergo rapid ring-opening with lithium halides in [bmim]PF 6 or [bmim]BF4 ionic liquids under mild and neutral conditions to afford the corresponding vic-halohydrins in high to quantitative yields. The epoxides show enhanced reactivity in ionic liquids thereby reducing reaction times and improving the yields significantly. The recovered ionic liquid can be reused in three to four subsequent runs with consistent activity.
- Yadav,Reddy,Reddy, Ch. Srinivas,Rajasekhar
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p. 476 - 477
(2007/10/03)
-
- Difluorocarbene induced of facile synthesis of chlorohydrins from glycidyl ethers
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A novel and unusual approach based on a ClCF2COONa-DMF system has been developed for the synthesis of chlorohydrins via an unexpected mechanism. In a first ever report for the synthesis of chlorohydrins from glycidyl ethers, e.g., CH2=CH-CH2-O-Z, CH 3CH2-O-Z, C6H5-O-Z, C 6H4(o-CH3)-O-Z, CH2=C(CH 3)C(=O)-O-Z, etc., (where Z = glycidyl), difluorocarbene-induced facile regioselective ring opening of epoxides has generated the compound in high yield (70%-83%).
- Singh, Sapna,Bhadury, Pinaki S.,Sharma, Mamta,Palit, Meehir,Jaiswal, Devendra K.
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p. 1249 - 1253
(2007/10/03)
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- Selective conversion of epoxides to vic-halo alcohols and symmetrical or unsymmetrical dihalides by triphenylphosphine/2,3-dichloro-5,6-dicyano-1,4- benzoquinone (DDQ) in the presence of quaternary ammonium halides
-
A new method is described for the efficient and selective conversion of epoxides to vic-halo alcohols or symmetrical and unsymmetrical dihalides using PPh3/DDQ/R4NX (X = Cl, Br, I) as a mixed-reagent system.
- Iranpoor, Nasser,Firouzabadi, Habib,Aghapour, Ghasem,Nahid, Azarmidokht
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p. 1885 - 1891
(2007/10/03)
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- Process for manufacturing an alpha-dihydroxy derivative and epoxy resins prepared therefrom
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A process for manufacturing an α-dihydroxy derivative from an aryl allyl ether wherein such α-dihydroxy derivative can be used to prepare an α-halohydrin intermediate and an epoxy resin prepared therefrom including epoxidizing an α-halohydrin intermediate produced from a halide substitution of an α-dihydroxy derivative which has been obtained by a dihydroxylation reaction of an aryl allyl ether in the presence of an oxidant or in the presence of an oxidant and a catalyst.
- -
-
Page/Page column 44-45
(2008/06/13)
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- Demonstration of a phosphazirconocene as a catalyst for the ring opening of epoxides with TMSCI
-
(Matrix presented) In this study, it was demonstrated for the first time that a phosphazirconocene catalyzes the ring opening of epoxides with TMSCI. This reactivity leads to a facile preparation of chlorohydrins. The late transition metal Fe analogue was found to catalyze the reaction at rates and stereoselectivity comparable to those of the Zr complex.
- Wang, Li-Sheng,Hollis, T. Keith
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p. 2543 - 2545
(2007/10/03)
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- Water content influences the selectivity of CALB-catalyzed kinetic resolution of phenoxymethyl-substituted secondary alcohols
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Derivatives of 1-phenoxy-2-alkanols were kinetically resolved by esterification with irreversible and reversible acyl donors using lipase B from Candida antarctica (Novozyme 435) as a catalyst. To optimize the relative rate of reaction (the E-value), esterifications in eight different solvents with different water activities were performed. For 3-bromo-1-phenoxy-2-propanol (1), the E-values in all the solvents were higher when the water activity was increased, while the E-values for 1-phenoxy-2-pentanol (2) and 3-chloro-1-phenoxy-2-propanol (3) decreased by increasing water activity. The water content of the various reaction media with the same water activity was determined. Solvents such as 1,4-dioxane, acetonitrile, and tetrahydrofuran contained much more water than hexane, carbon tetrachloride, cyclohexane, toluene, and benzene. At high-water activity, the high-water content of the former group of solvents resulted in termination of the reaction at low conversion. The reason seemed to be that the acyl donor and possibly also the produced esters were hydrolyzed. This was not the case when the esterification was performed in water-immiscible solvents with the same water activity.
- Jacobsen, Elisabeth Egholm,Anthonsen, Thorleif
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p. 577 - 581
(2007/10/03)
-
- Highly facile biomimetic regioselective ring opening of epoxides to halohydrins in the presence of β-cyclodextrin
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Highly regioselective ring opening of epoxides to halohydrins has been carried out in impressive yields with hydrogen and lithium halides in presence of β-cyclodextrin using water as solvent.
- Reddy, M.Arjun,Surendra,Bhanumathi,Rao, K.Rama
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p. 6003 - 6008
(2007/10/03)
-
- Polyvinylpyrrolidone/thionyl chloride as a new polymeric reagent for facile conversion of epoxides to β-chlorohydrins
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Epoxides undergo rapid ring opening with cross-linked polyvinylpyrrolidone/thionyl chloride complex, under mild reaction condition to afford chlorohydrins in high yields.
- Tamami, Bahman,Ghazi, Iraj,Mahdavi, Hossein
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p. 3725 - 3731
(2007/10/03)
-
- Enantioselective ring-opening of epoxides by HF-reagents: Asymmetric synthesis of fluoro lactones
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The asymmetric ring opening of meso- and racemic-epoxides with different HF-reagents mediated by enantiopure (salen)chromium chloride provides optically active fluorohydrins with maximum 90% e.e. This reaction as well as lipase-catalyzed deracemization of
- Haufe, Günter,Bruns, Stefan,Runge, Martina
-
-
- Highly regioselective ring opening of epoxides and aziridines using cerium(III) chloride
-
A wide variety of epoxides and aziridines were converted to the corresponding β-halohydrins and β-haloamines using cerium(III) chloride and the cerium(III) chloride/NaI system in acetonitrile. The reactions were highly regioselective and efficient with excellent yields under mild and neutral reaction conditions.
- Sabitha, Gowravaram,Satheesh Babu,Rajkumar,Reddy,Yadav
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p. 3955 - 3958
(2007/10/03)
-
- Bis-chlorodibutyltin oxide as a new reagent for a mild, versatile and regioselective ring-opening of epoxides
-
A convenient and efficient procedure for the ring-opening of epoxides by means of alcohols and bis-chlorodibutyltin oxide is described. The cleavage of the oxiranes is found to proceed regioselectively under mild reaction conditions. Thus, several haloalkanols, useful intermediates toward biological active molecules, are easily obtained in very good yields.
- Salomon
-
-
- Preparation of halohydrin β-blocker precursors using yeast-catalysed reduction
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The preparation of halohydrin β-blocker precursors using yeast-catalysed reduction of α-haloketones was performed. The influence in the yield and e.e. of several process variables was analysed. The (S)-enantioselectivity observed with Saccharomyces cerevisiae can be changed to (R)-enantioselectivity using methyl vinyl ketone as selective inhibitor (25 mM). Using resting fresh cells better yields and e.e.s are observed than using growing cells. Yarrowia lipolytica 1240 resting cells gave 87% yield of (S)-1-chloro-3(1-naphthyloxy)propan-2-ol (99% e.e.). Pichia mexicana 11105 resting cells gave 85% yield of (R)-1-chloro-3(1-naphthyloxy)propan-2-ol (precursor of propranolol) (95% e.e). The reduction process is applied to other α-haloketones, a lower e.e. being obtained the closer the size of the ketone substituents.
- Martinez, Fernando,Del Campo, Carmen,Sinisterra,Llama, Emilio F.
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p. 4651 - 4660
(2007/10/03)
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- Enantioselective introduction of fluoride into organic compounds: First asymmetric ring opening of epoxides by hydrofluorinating reagents
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The first enantioselective epoxide ring opening with hydrofluorinating agents mediated by chiral non-racemic Lewis acids is reported. The reaction of cyclohexene oxide (1) with KHF2/18-crown-6 is trans-diastereoselective and proceeds with 55% ee to form (R,R)-(-)-2-fluorocyclohexanol (2) in the presence of Jacobsen's (S,S)-(+)-(salen)chromium chloride complex A. From racemic epoxides such as styrene oxide (9) or phenyl glycidether (13), mainly or exclusively the products with fluorine in primary position are formed with 90 or 62% ee, respectively. In all cases minor amounts of corresponding chlorohydrins are formed.
- Bruns, Stefan,Haufe, Günter
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p. 247 - 254
(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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- Synthesis of tetrahydrofurans by the reaction of α,β-epoxy alcohol derivatives with allylsilanes
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In the presence of SnCl4, α,β-epoxy alcohol derivatives easily reacted with allylsilanes to give the corresponding tetrahydrofurans in moderate yields.
- Sugita, Yoshiaki,Kimura, Yoko,Yokoe, Ichiro
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p. 5877 - 5880
(2007/10/03)
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- Solvent-free organic reactions on silica gel supports. Facile transformation of epoxides to β-halohydrins with lithium halides
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The reaction of epoxides with lithium halides was efficiently promoted on the surface of silica gel in the absence of any solvent to give the corresponding β-halohydrins. The reactivity of lithium halides was shown to follow the order LiI > LiBr >> LiCl, and the reactivity of LiCl was dramatically increased by adding an equivalent amount of water to this system. On the other hand a similar reaction with α,β-epoxyketones produces the α-haloenone derivatives, presumably via halohydrin intermediates. The epoxide-opening reaction of (R)-(+)-styrene oxide was also investigated to clarify the stereochemical features of this reaction.
- Kotsuki, Hiyoshizo,Shimanouchi, Tomoyasu,Ohshima, Reiji,Fujiwara, Shunsuke
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p. 2709 - 2722
(2007/10/03)
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- Methyltriphenylphosphonium tetrahydroborate (MePh3PBH4). A stable, selective and versatile reducing agent
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Methyltriphenylphosphonium tetrahydroborate as a stable quaternary phosphonium borohydride is introduced. This compound is able to reduce aldehydes, ketones, acyl chlorides, and azides efficiently in CH2Cl2. α,β-Unsaturated carbonyl compounds are reduced selectively via 1,2-reduction. The effect of Lewis acids upon the mode and the rate of the reaction of epoxides and acetophenone are also described. This reagent is also able to bring about reductions effectively in the absence of solvent.
- Firouzabadi, Habib,Adibi, Mina
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p. 125 - 147
(2007/10/03)
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- Highly regio- and stereoselective synthesis of β-halohydrins from epoxides catalyzed with ceric ammonium nitrate
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Ce(IV) as ceric ammonium nitrate can effectively catalyze ring opening of epoxides with halides under very mild conditions and easy procedure to give the corresponding β-chloro- and β-bromohydrins in excellent yields. The reactions occur with both substituted and unsubstituted quaternary ammonium halides and with high regio- and stereoselectivity. The reaction of optically active styrene oxide with chloride ion was found to be highly stereospecific and afforded the corresponding β-halohydrin in 96% ee.
- Iranpoor,Kazemi,Salehi
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p. 1247 - 1258
(2007/10/03)
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- Efficient Nucleophilic Cleavage of Oxiranes to Chlorohydrins
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SnCl2*2H2O-Mg and THF-H2O is an efficient system for the conversion of oxiranes into chlorhydrins.
- Sarangi, Chintamani,Das, Nalin B.,Nanda, Bhagabat,Nayak, Amaendu,Sharma, Ram P.
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