- Microwave-assisted aminolysis of epoxides under solvent-free conditions catalyzed by montmorillonite clay
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The reaction of primary and secondary amines with epoxides in the presence of montmorillonite K10 clay, under solvent-free conditions and microwave irradiation affords high yields of β-amino alcohols.
- Mojtahedi, Mohammad M.,Saidi, Mohammad R.,Bolourtchian, Mohammad
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- Synthesis and application of Cu(II) immobilized MCM-41 based solid Lewis acid catalyst for aminolysis reaction under solvent-free condition
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In this paper, a Cu(II) immobilized periodic mesoporous organosilica (PMOs) was synthesized and used as a reusable solid Lewis acid catalyst for the aminolysis of epoxides under solvent-free conditions. An amide-based ligand, L-propylsilyl (1) having a specific binding pocket was prepared and fabricated on mesoporous MCM-41 to produce mesoporous organosilica L-propylsilyl@MCM-41 (2). Further, it has been utilized for anchoring Cu(II) ions under controlled reaction conditions to yield solid Lewis acid catalyst Cu(II)-L-propylsilyl@MCM-41 (3). The synthesized catalyst 3 exhibits significantly higher catalytic activity for aminolysis compared to hitherto known solid Lewis acid catalysts. An extensive range of β-amino alcohols with high regio and stereoselectivity were prepared by using catalyst 3. The catalyst was recovered easily and reused eight times without any loss in its catalytic activity. Furthermore, the synthesis of clinically significant propranolol (β-blocker) from α- naphthyl glycidyl ether was attained successfully using catalyst 3 in a very decent yield.
- Chaudhary, Garima,Gupta, Neha,Singh, Amit Pratap
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- M-Type SrFe12O19Ferrite: An Efficient Catalyst for the Synthesis of Amino Alcohols under Solvent-Free Conditions
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Magnetically separable strontium hexaferrite SrFe12O19 was prepared using the chemical coprecipitation method, and the nanostructured material was characterized by X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and BET analysis. The SEM images showed the homogeneity of the chemical composition of SrFe12O19 and uniform distribution of size and morphology. The pore size of the nanomaterial and its specific area were determined by BET measurements. Strontium hexaferrite SrFe12O19 exhibited a strong magnetic field, which is highly suitable in the heterogeneous catalysis as it can be efficiently separated from the reaction. The magnetic nanocatalyst showed high activity and environmentally benign heterogeneous catalysts for the epoxide ring-opening with amines affording β-amino alcohols under solvent-free conditions. When unsymmetrical epoxides were treated in the presence of aromatics amines, the regioselectivity was influenced by the electronic and steric factors. Total regioselectivity was observed for the reactions performed with aliphatic amines. The magnetically SrFe12O19 nanocatalyst showed excellent recyclability with continuously good catalytic activities after four cycles.
- Laayati, Mouhsine,Hasnaoui, Ali,Abdallah, Nayad,Oubaassine, Saadia,Fkhar, Lahcen,Mounkachi, Omar,El Houssame, Soufiane,Ait Ali, Mustapha,El Firdoussi, Larbi
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- Synthesis and structure of an air-stable bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate and its application in catalytic epoxide ring-opening reactions
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An air-stable mononuclear complex of bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate was successfully synthesized by treating C6F5SO3Ag with [(CH3)5Cp]2ZrCl2, which showed the cationic uninuclear structure of [{(CH3)5Cp}2Zr(CH3CN)2(H2O)][OSO2C6F5]2·CH3CN (1) confirmed by the X-ray analysis. Complex 1 was also characterized by other techniques and found to have the good nature of air-stability, water tolerance, thermally-stability and strong Lewis-acidity. Moreover, the complex showed high catalytic activity and recyclability in catalytic epoxide ring-opening reactions by amines or alcohols. This catalytic system affords a simple and efficient approach for synthesis of β-amino alcohols or β-alkoxy alcohols.
- Li, Ningbo,Wang, Lingxiao,Wang, Haojiang,Qiao, Jie,Zhao, Wenjie,Xu, Xinhua,Liang, Zhiwu
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p. 1033 - 1039
(2018/02/06)
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- Tetragonal versus hexagonal: Structure-dependent catalytic activity of Co/Zn bimetallic metal-organic frameworks
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Tetragonal and hexagonal phases of monometallic Zn and bimetallic Co/Zn metal-organic frameworks (MOFs), with secondary building units (SBUs) containing a M3O (M = metal) cluster, were synthesized from identical constituents using a benzenetricarboxylate (BTC3-) linker that forms decorated 3,6- and 3,5-connected networks, respectively. There exist subtle differences between the SBUs; one of the metal atoms in the M3O cluster in the tetragonal phase has one dissociable DMF solvent molecule while that in the hexagonal phase has three. Connectivities between the SBUs form one-dimensional channels in both MOFs. These MOFs catalyze the chemoselective addition of amines to epoxides, giving exclusively β-hydroxyamine under heterogeneous conditions. A ring-opening reaction of a symmetrical epoxide showed that the hexagonal phase diastereoselectively yields trans-alcohol, exhibiting an exquisite model for structure-dependent activity.
- Pariyar, Anand,Asl, Hooman Yaghoobnejad,Choudhury, Amitava
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p. 9250 - 9257
(2016/09/28)
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- Mild regiospecific alcoholysis and aminolysis of epoxides catalyzed by zirconium(IV) oxynitrate
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A regiospecific method for the ring-opening reaction of epoxides by the primary, secondary, tertiary alcohols, and aryl, aliphatic amines has been developed using non-toxic metal nitrate salt as a catalyst. The best results were obtained using zirconium(IV) oxynitrate among the various screened metal nitrate salts. The reported protocol works efficiently for styrene epoxide and aliphatic as well.
- Shinde, Sandip S.,Said, Madhukar S.,Surwase, Trupti B.,Kumar, Pradeep
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supporting information
p. 5916 - 5919
(2015/11/02)
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- Mesoporous Titania-Iron(III) Oxide with Nanoscale Porosity and High Catalytic Activity for the Synthesis of β-Amino Alcohols and Benzimidazole Derivatives
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A mesoporous TiO2-Fe2O3 mixed oxide material (MTF-1E) with nanoscale porosity and a high BET surface area was synthesized using sodium dodecyl sulfate (SDS) as a structure-directing agent. The material was characterized by
- Roy, Susmita,Banerjee, Biplab,Salam, Noor,Bhaumik, Asim,Islam, Sk. Manirul
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p. 2689 - 2697
(2015/09/15)
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- N-Fluorobenzenaminium tetrafluoroborate generated in situ by aniline and Selectfluor as a reusable catalyst for the ring opening of epoxides with amines under microwave irradiation
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The ring opening of epoxides with aromatic and aliphatic amines was carried out under solvent free conditions using N-fluorobenzenaminium tetrafluoroborate (2 mol%) generated in situ by the reaction of aniline and Selectfluor as a catalyst with microwave irradiation. Excellent yields of β-amino alcohols were obtained. The catalyst also results in the retention of the stereochemistry for the ring opening of enantiopure epoxide with amine. The catalyst was recovered and reused up to 4 cycles for the ring opening of cyclohexene oxide with aniline. This journal is
- Chauhan, Manmohan Singh,Yadav, Geeta Devi,Hussain, Firasat,Singh, Surendra
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p. 3945 - 3952
(2015/02/19)
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- An efficient protocol for regioselective ring opening of epoxides using sulfated tungstate: Application in synthesis of active pharmaceutical ingredients atenolol, propranolol and ranolazine
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Sulfated tungstate was found to be a new and highly efficient catalyst for opening of epoxide rings by amines to give β-amino alcohols with high regioselectivity. Various advantages associated with this novel and environmental friendly protocol include solvent-free conditions, short reaction times, high product yields, simple workup procedure and easy recovery and reusability of the catalyst. This protocol has been applied for the synthesis of active pharmaceutical ingredients atenolol, propranolol and ranolazine.
- Pathare, Sagar P.,Akamanchi, Krishnacharya G.
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supporting information
p. 6455 - 6459
(2013/11/19)
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- In vivo antifilarial activity of some cyclic and acylic alcohols
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The filarial nematodes, Wuchereria bancrofti, Brugia malayi, and Brugia timori are the causative agents of lymphatic filariasis. 2-Substituted propanol, cyclohexanol, and cyclooctanol compounds were evaluated for microfilaricidal and macrofilaricidal activity in vivo against Acanthocheilonema viteae and Litomosoides carinii in rodents. In the cyclohexanol series, 2-(piperidin-1-yl) cyclohexanol (2b) showed 88.9% macrofilaricidal activity against A. viteae in vivo, while cyclooctanol series, 2-(4- benzyl piperdin-1-yl) cyclooctanol (2f) showed 100% macrofilaricidal activity against A. viteae. Further, compounds 1-(furan-2-ylamino) ethanol (4a) and 1-(4-benzylpiperidin- 1-yl)-ethyl acetate (5b) showed 81.3% and 83.4% macrofilaricidal activity, respectively, against the same parasite. Interestingly, compounds 2f and 4a showed significant sterilization of female worms in A. viteae. However, these compounds were found inactive against L. carinii. Therefore, the new class of compounds appeared to have promising antifilarial activity.
- Agarwal, Alka,Awasthi, Satish K.,Murthy
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experimental part
p. 430 - 434
(2012/04/18)
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- Zinc tetrafluoroborate hydrate as a mild catalyst for epoxide ring opening with amines: Scope and limitations of metal tetrafluoroborates and applications in the synthesis of antihypertensive drugs (RS)/(R)/(S)-metoprolols
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The scope and limitations of metal tetrafluoroborates have been studied for epoxide ring-opening reaction with amines, and Zn(BF4) 2?xH2O has been found to be a mild and efficient catalyst affording high yields under solvent-free conditions at rt with excellent chemo-, regio-, and stereoselectivities. The catalytic efficiency followed the order Zn(BF4)2?xH2O ? Cu(BF4)2?xH2O > Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > LiBF4 for reactions with cyclohexene oxide and Zn(BF4)2?xH2O ? Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > Cu(BF4)2?xH2O for stilbene oxide, but AgBF4 was ineffective. For reaction of styrene oxide with aniline, the metal tetrafluoroborates exhibited comparable regioselectivity (1:99-7:93) with preferential reaction at the benzylic carbon of the epoxide ring. A reversal of regioselectivity (91:1-69:31) in favor of the reaction at the terminal carbon of the epoxide ring was observed for reaction with morpholine. The regioselectivity was dependent on the electronic and steric factors of the epoxide and the pKa of the amine and independent of amine nucleophilicity. The role of the metal tetrafluoroborates is envisaged as "electrophile nucleophile dual activation" through cooperativity of coordination, charge-charge interaction, and hydrogen-bond formation that rationalizes the catalytic efficiency, substrate reactivity, and regioselectivity. The methodology was used for synthesis of cardiovascular drug metoprolol as racemic and enriched enantiomeric forms.
- Pujala, Brahmam,Rana, Shivani,Chakraborti, Asit K.
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scheme or table
p. 8768 - 8780
(2011/12/04)
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- Optimisation of the Anti-Trypanosoma brucei Activity of the Opioid Agonist U50488
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Screening of the Sigma-Aldrich Library of Pharmacologically Active Compounds (LOPAC) against cultured Trypanosoma brucei, the causative agent of African sleeping sickness, resulted in the identification of a number of compounds with selective antiproliferative activity over mammalian cells. These included (+)-(1R,2R)-U50488, a weak opioid agonist with an EC50 value of 59nM as determined in our T.brucei invitro assay reported previously. This paper describes the modification of key structural elements of U50488 to investigate structure-activity relationships (SAR) and to optimise the antiproliferative activity and pharmacokinetic properties of this compound.
- Smith, Victoria C.,Cleghorn, Laura A. T.,Woodland, Andrew,Spinks, Daniel,Hallyburton, Irene,Collie, Iain T.,YiMok,Norval, Suzanne,Brenk, Ruth,Fairlamb, Alan H.,Frearson, Julie A.,Read, Kevin D.,Gilbert, Ian H.,Wyatt, Paul G.
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experimental part
p. 1832 - 1840
(2012/06/18)
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- A facile and general synthesis of 2β-aminosteroids
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A facile and general synthesis of 2β-aminosteroids in high yields from 2,3α-epoxy-5α-androstan-17-one by regioselective aminolysis is developed using a zinc chloride/water catalytic system. The reaction is successful with both aliphatic and aromatic amine
- Ke, Xianbing,Hu, Hao,Zhou, Dingshan,Xu, Wenjin,Zhu, Qifeng,Reddy, Nimmanapalli Pulla,Hu, Xianming
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scheme or table
p. 1255 - 1260
(2009/12/07)
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- Aminolysis of epoxides using iridium trichloride as an efficient catalyst
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Iridium trichloride catalyzes the ring opening of epoxides by aryl, heterocyclic, or aliphatic amines under mild conditions. The reactions proceed at room temperature to afford the corresponding b-amino alcohols in excellent yields. In general, the aminolysis of cyclopentene oxide is faster than that of cyclohexene oxide in the presence of iridium trichloride as a catalyst. Georg Thieme Verlag Stuttgart.
- Agarwal, Jyoti,Duley, Anju,Rani, Rashmi,Peddinti, Rama Krishna
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experimental part
p. 2790 - 2796
(2010/01/21)
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- Highly efficient and versatile chemoselective addition of amines to epoxides in water catalyzed by erbium(III) triflate
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Er(OTf)3 is proposed as a highly efficient and reusable catalyst for the opening of epoxides in water with aliphatic as well as aromatic amines leading to the synthesis of β-amino alcohols. The aqueous conditions employed in the present method will make it 'environmentally friendly' and potentially useful for industrial applications.
- Procopio, Antonio,Gaspari, Marco,Nardi, Monica,Oliverio, Manuela,Rosati, Ornelio
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p. 2289 - 2293
(2008/09/18)
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- Synthesis of β-amino alcohols using MgO as a new catalyst under solvent-free conditions
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MgO catalyzed efficiently the ring opening of epoxides with a range of aromatic and aliphatic amines to produce β-substituted alcohols in high yields under solvent-free conditions. Exclusive trans stereoselectivity is observed for cyclic epoxide.
- Hosseini-Sarvari, Mona
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- Amino alcohols in organocatalysed acylation and deacylation: The effect of dialkylamino substituents on the rate
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In alcohols and esters, a neighbouring dialkylamino group can enhance the reactivity towards acylation and deacylation, respectively, that is, such amino alcohols can act as transacylation catalysts like DMAP. This effect is dependent on the number of (carbon) spacer atoms, flexibility of the molecule and the presence and position of further heteroatoms. Based on this effect, the site selective acylation and deacylation of desmycosin, a macrocycle antibiotic possessing an amino sugar moiety, is described.
- Wessjohann, Ludger A.,Zhu, Mingzhao
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supporting information; experimental part
p. 107 - 112
(2009/04/08)
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- Microwave-enhanced bismuth triflate-catalyzed epoxide opening with aliphatic amines
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In the presence of a catalytic amount of Bi(OTf)3·4H2O and under microwave irradiation, neat mixtures of epoxides and amines afforded smoothly the corresponding 2-amino alcohols. A wide variety of aliphatic amines were reacted with cycloalkene oxide, styrene oxide, and stilbene oxide. The reaction proceeded rapidly and afforded the 2-amino alcohols in high up to quantitative yields. All products could be obtained without aqueous work-up by simple filtration.
- Ollevier, Thierry,Nadeau, Etienne
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p. 1546 - 1550
(2008/09/19)
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- Dynamic kinetic resolution allows a highly enantioselective synthesis of cis-α-aminocycloalkanols by ruthenium-catalyzed asymmetric hydrogenation
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(Chemical Equation Presented) Resolutely dynamic hydrogenation: A highly efficient asymmetric hydrogenation of racemic N,N-disubstituted α-aminocycloalkanones involving dynamic kinetic resolution in the presence of a ruthenium catalyst gives chiral α-aminocycloalkanols with excellent enantioselectivities and cis diastereoselectivities (see scheme). A synthesis of optically pure U-(-)-50488 based on this reaction is reported.
- Liu, Sheng,Xie, Jian-Hua,Wang, Li-Xin,Zhou, Qi-Lin
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p. 7506 - 7508
(2008/09/17)
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- Zinc(II) perchlorate hexahydrate catalyzed opening of epoxide ring by amines: Applications to synthesis of (RS)/(R)-propranolols and (RS)/(R)/(S)-naftopidils
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(Figure Presented) Commercially available zinc(II) Perchlorate hexahydrate [Zn(ClO4)2·6H2O] was found to be a new and highly efficient catalyst for opening of epoxide rings by amines affording 2-amino alcohols in high yields under solvent-free conditions and with excellent chemo-, regio-, and stereoselectivities. For unsymmetrical epoxides, the regioselectivity was influenced by the electronic and steric factors associated with the epoxides and the amines. A complementarity in the regioselectivity was observed during the reaction of styrene oxide with aromatic and aliphatic amines: aromatic amines provided amino alcohols from nucleophilic attack at the benzylic carbon as major products whereas aliphatic amines resulted in formation of the amino alcohols through reaction at the terminal carbon atom of the epoxide ring as the major/sole products. Reaction of aniline with various glycidic ethers gave the amino alcohols by regioselective nucleophilic attack at the terminal carbon atom of the epoxide ring as the only/major product. Zinc(II) Perchlorate hexahydrate was found to be the best catalyst compared to other metal Perchlorates. The counteranion modulated the catalytic property of the various Zn(II) compounds that followed the order Zn(ClO4) 2·6H2O Zn(BF4)2 ~ Zn(OTf)2 ZnI2 > ZnBr2 > ZnCl2 > Zn(OAc)2 > Zn(CO3)2 in parallelism with the acidic strength of the corresponding protic acids (except for TfOH). The applicability of the methodology was demonstrated by the synthesis of cardiovascular drugs propranolol and naftopidil as racemates and optically active enantiomers.
- Shivani,Pujala, Brahmam,Chakraborti, Asit K.
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p. 3713 - 3722
(2008/02/05)
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- Synthesis and biological studies of novel 2-aminoalkylethers as potential antiarrhythmic agents for the conversion of atrial fibrillation
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A series of 2-aminoalkylethers prepared as potential antiarrhythmic agents is described. The present compounds are mixed sodium and potassium ion channel blockers and exhibit antiarrhythmic activity in a rat model of ischemia-induced arrhythmias. Structure-activity studies led to the identification of three compounds 5, 18, and 26, which were selected based on their particular in vivo electrophysiological properties, for studies in two canine atrial fibrillation (AF) models. The three compounds converted AF in both models, but only compound 26 was shown to be orally bioavailable. Resolution of the racemate 26 into its corresponding enantiomers 40 and 41 and subsequent biological testing of these enantiomers led to the selection of (1S,2S)-1-(1-naphthalenethoxy)-2-(3- ketopyrrolidinyl)cyclohexane monohydrochloride (41) as a potential atrial selective antiarrhythmic candidate for further development.
- Plouvier, Bertrand,Beatch, Gregory N.,Jung, Grace L.,Zolotoy, Alexander,Sheng, Tao,Clohs, Lilian,Barrett, Terrance D.,Fedida, David,Wang, Wei Q.,Zhu, Jeff J.,Liu, Yuzhong,Abraham, Shlomo,Lynn, Leah,Dong, Ying,Wall, Richard A.,Walker, Michael J. A.
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p. 2818 - 2841
(2008/02/09)
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- Hydrophobic amplification of noncovalent organocatalysis
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The effects of hydrogen-bonding organocatalysts and water for the acceleration of epoxide openings with a variety of nucleophiles are additive and lead to excellent yields of the catalyzed reactions in water. The Royal Society of Chemistry 2006.
- Kleiner, Christian M.,Schreiner, Peter R.
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p. 4315 - 4317
(2007/10/03)
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- Copper(II) tetrafluoroborate-catalyzed ring-opening of epoxides by amines
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Copper(II) tetrafluoroborate catalyzes efficiently the selective opening of epoxides by amines leading to the synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in high yields under solvent-free conditions.
- Kamal, Ahmed,Ramu,Azhar, Mohd. Ameruddin,Khanna, G.B. Ramesh
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p. 2675 - 2677
(2007/10/03)
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- Solid lithium perchlorate as a powerful catalyst for the synthesis of β-aminoalcohols under solvent-free conditions
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Lithium perchlorate catalyzed the ring opening of epoxides with amines to provide the corresponding β-aminoalcohols in excellent yields with high regioselectivity. The reaction proceeds rapidly under mild and neutral conditions and worked well with primary, secondary, aliphatic, aromatic, and hindered amines in short times at room temperature, in the absence of solvent.
- Azizi, Najmodin,Saidi, Mohammad R.
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p. 505 - 507
(2007/10/03)
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- Highly chemoselective addition of amines to epoxides in water
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(Chemical Equation Presented) Aminolysis of a variety of epoxides by aliphatic and aromatic amines in water, in the absence of any catalyst with high yields, is reported. β-Amino alcohols were formed under mild conditions with high selectivity and in excellent yields.
- Azizi, Najmodin,Saidi, Mohammad R.
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p. 3649 - 3651
(2007/10/03)
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- AMINOCYCLOHEXYL ETHER COMPOUNDS AND USES THEREOF
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Aminocyclohexyl ether compounds of formula (I), or a solvate or pharmaceutically acceptable salt thereof: are disclosed. In said formula, A, X and R, -R5 have the meanings given in the description. The compounds of the present invention may be inco
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- Chemoenzymatic preparation of optically active trans-cyclohexane-1,2- diamine derivatives: An efficient synthesis of the analgesic U-(-)-50,488
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Stereoespecific syntheses of (±)-trans-N,N-cyclohexane-1,2-diamines ((±)-4a-g) were carried out from the corresponding (±)-trans-N,N- dialkylaminocyclohexanols by successive treatment with mesyl chloride and aqueous ammonia. The stereochemical outcome indicates the formation of a meso-aziridinium ion intermediate, Kinetic resolutions of diamines (±)-4 were efficiently accomplished in aminolysis reactions catalyzed by lipase B from Candida antarctica with ethyl acetate as the solvent and acyl donor. Acetamides and the remaining diamines, isolated as the benzyloxycarbonyl derivatives, were obtained with very high ee values (92-99%), One of the carbamates was used as a precursor of the analgesic U-(-)-50,488.
- Gonzalez-Sabin, Javier,Gotor, Vicente,Rebolledo, Francisca
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p. 5788 - 5794
(2007/10/03)
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- ZrCl4 as a new and efficient catalyst for the opening of epoxide rings by amines
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Zirconium(IV) chloride catalyses the nucleophilic opening of epoxide rings by amines leading to the efficient synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in short times at room temperature in the absence of solvent. Exclusive trans stereoselectivity is observed for cyclic epoxides. Aromatic amines exhibit excellent regioselectivity for preferential nucleophilic attack at the sterically less hindered position during the reaction with unsymmetrical epoxides. However, in case of styrene oxide, selective formation of the benzylic amine was observed during the reactions with aromatic amines.
- Chakraborti, Asit K.,Kondaskar, Atul
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p. 8315 - 8319
(2007/10/03)
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- Diisopropoxyaluminium trifluoroacetate: A new promoter for aminolysis of epoxides
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Aminolysis of symmetrical as well as unsymmetrical epoxides using various amines in the presence of diisopropoxyaluminium trifluoroacetate (DIPAT) as a new promoter gave 1,2-amino alcohols in excellent yields at room temperature with good to excellent selectivities.
- Rampalli, Sriram,Chaudhari, Sachin S.,Akamanchi, Krishnacharya G.
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- Dibasic benzo[b]thiophene derivatives as a novel class of active site directed thrombin inhibitors: 4. SAR studies on the conformationally restricted C3-side chain of hydroxybenzo[b]thiophenes
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A novel series of benzo[b]thiophene diamine thrombin inhibitors with a conformationally restricted C3-side chain 3 was investigated. The constrained C3-side chain by a cyclohexyl ring contributed to not only an additive but also a synergistic effect on the thrombin inhibitory activity. The SAR studies resulted in the discovery of a potent thrombin inhibitor 27 that was over 750-fold more potent than the initial lead compound 1.
- Takeuchi, Kumiko,Kohn, Todd J.,Sall, Daniel J.,Denney, Michael L.,McCowan, Jefferson R.,Smith, Gerry F.,Gifford-Moore, Donetta S.
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p. 759 - 764
(2007/10/03)
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- Lithium trifluoromethanesulfonate-catalysed aminolysis of oxiranes
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The aminolysis of oxiranes was found to be catalysed by lithium trifluoromethanesulfonate in acetonitrile solutions. This salt turned out to be an excellent substitute for the unsafe lithium perchlorate.
- Auge, Jacques,Leroy, Frederic
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p. 7715 - 7716
(2007/10/03)
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- Boranes in Synthesis. 5. The Hydroboration of Enamines with Mono- and Dialkylboranes. Asymmetric Synthesis of β-Amino Alcohols of Moderate Enantiomeric Purity from Aldehyde Enamines
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The hydroboration of both acyclic and cyclic aldehyde and ketone enamines with such representative mono- and dialkylboranes as thexylborane and dicyclohexylborane, followed by an oxidative workup, yields the corresponding β-amino alcohols in good to excellent isolated yields.The hydroboration of ketone and aldehyde enamines with the asymmetric hydroboration reagents monoisopinocampheylborane (dIpeBH2) and diisopinocampheylborane (dIpc2BH) was also investigated. dIpc2BH is highly effective for the asymmetric hydroboration of acyclic aldehyde enamines, such as 1-(4-morpholino)-3-phenyl-1-propene and 1-(1-pyrrolidino)-1-octene.Oxidation of the intermediate trialkylborane furnishes the corresponding β-amino alcohols in 50-86percent ee.The stereogenic center of the carbinol carbon is consistently enriched in the R-enantiomer when dIpc2BH prepared from (+)-α-pinene is used as the hydroboration reagent.The enantiomeric excesses of the β-amino alcohols synthesized in this study were determined by HPLC using a chiral stationary phase.The absolute configuration of some of the β-amino alcohols synthesized in this study were determined by chiral HPLC comparison with authentic β-amino alcohols prepared from chiral epoxides of known absolute configuration.
- Fisher, Gary B.,Goralski, Christian T.,Nicholson, Lawrence W.,Hasha, Dennis L.,Zakett, Donald,Singaram, Bakthan
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p. 2026 - 2034
(2007/10/02)
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- Boranes in Synthesis. 6. A New Synthesis of β-Amino Alcohols from Epoxides. Use of Lithium Amides and Aminoborane Catalysts To Synthesize β-Amino Alcohols from Terminal and Internal Epoxides in High Yield
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A study of the conversion of terminal and internal epoxides to the corresponding β-amino alcohols using simple primary and secondary lithium amides has been carried out.Thus, styrene oxide and 1,2-epoxydodecane react directly with primary and secondary lithium amides in THF at 25 deg C to give a single regioisomer of the corresponding β-amino alcohols in 80-100percent isolated yields.Since internal epoxides are known to yield predominantly allylic alcohols when reacted with lithium amides, we employed a series of aminoborane Lewis-acid catalists, generated in situ, to suppress formation of the allylic alcohols.Thus, the reaction of cyclohexene oxide with a variety of primary and secondary lithium amides at 34 deg C in diethyl ether in the presence of a catalytic amount of B-bromo-9-BBN afforded the corresponding β-amino alcohols in 70-95percent isolated yield.
- Harris, Clifford E.,Fisher, Gary B.,Beardsley, David,Lee, Lawrence,Goralski, Christian T.,et al.
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p. 7746 - 7751
(2007/10/02)
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- Hydroboration. 81. Synthesis of 2-(Dialkylamino)boronic Esters and Acids via Hydroboration of Enamines. A Convenient Preparation of β-Dialkylamino Alcohols
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Hydroboration of representative enamines with 1 equiv of borane-dimethyl sulfide (BMS) in tetrahydrofuran affords as the major product the corresponding boranes, which are charakterized by B NMR spectroscopy.These intermediates on methanolysis give the corresponding boronic acids in essentially quantitative yields.The boronic acids thus obtained can be reestrified with 1,3-propanediol to give the corresponding 2--1,3,2-dioxaborinanes.Consequently, it is now possible to prepare dialkyloamino-substituted organoborane compounds with the potential to be elaborated to a wide variety of functionalized tiralkylamines.Alkaline hydrogen peroxide oxidation of these organoborane intermediates affords the corresponding β-dialkyloamino alcohols.The hydroboration of enamines, methanolysis of the intermediate borane derivatives, and oxidation of the boronate esters is accompanied by side reactions such as elimination and protonolysis.The magnitude of these side reactions varies considerably with the structures of the anamines.However, moderate to excellent yields of the desired organoboron compounds can frequently be achieved.The use of trimethylamine N-oxide dihydrate for the oxidation of the 2-(dialkylamino)boronate esters greatly suppresses the side reactions and vastly improves the yields of the β-dialkylamino alcohols.
- Goralski, Christian T.,Singaram, Bakthan,Brown, Herbert C.
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p. 4014 - 4019
(2007/10/02)
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