- A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles
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A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.
- Rossi-Fernández, Lucía,Dorn, Viviana,Radivoy, Gabriel
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supporting information
p. 519 - 526
(2021/03/31)
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- Palladium-Promoted Neutral 1,4-Brook Rearrangement/Intramolecular Allylic Cyclization Cascade Reaction: A Strategy for the Construction of Vinyl Cyclobutanols
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A cascade reaction to build vinyl cyclobutanol rings through activation of vinyl epoxides by palladium, followed by 1,4-Brook rearrangement and intramolecular cyclization with a palladium complex of the resulting carbon anion, is described. Through this cascade reaction, several highly substituted cyclobutanol substrates were achieved in good yields with high stereoselectivities.
- Zhang, Hao,Ma, Shiqiang,Yuan, Ziyun,Chen, Peng,Xie, Xingang,Wang, Xiaolei,She, Xuegong
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supporting information
p. 3478 - 3481
(2017/07/15)
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- Enantioselective bio-hydrolysis of various racemic and meso aromatic epoxides using the recombinant epoxide hydrolase Kau2
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Abstract Epoxide hydrolase Kau2 overexpressed in Escherichia coli RE3 has been tested with ten different racemic and meso α,β-disubstituted aromatic epoxides. Some of the tested substrates were bi-functional, and most of them are very useful building blocks in synthetic chemistry applications. As a general trend Kau2 proved to be an extremely enantioselective biocatalyst, the diol products and remaining epoxides of the bioconversions being obtained - with two exceptions - in nearly enantiomerically pure form. Furthermore, the reaction times were usually very short (around 1 h, except when stilbene oxides were used), and the use of organic co-solvents was well tolerated, enabling very high substrate concentrations (up to 75 g/L) to be reached. Even extremely sterically demanding epoxides such as cis- and trans-stilbene oxides were transformed on a reasonable time scale. All reactions were successfully conducted on a 1 g preparative scale, generating diol- and epoxide-based chiral synthons with very high enantiomeric excesses and isolated yields close to the theoretical maximum. Thus we have here demonstrated the usefulness and versatility of lyophilized Escherichia coli cells expressing Kau2 epoxide hydrolase as a highly enantioselective biocatalyst for accessing very valuable optically pure aromatic epoxides and diols through kinetic resolution of racemates or desymmetrization of meso epoxides.
- Zhao, Wei,Kotik, Michael,Iacazio, Gilles,Archelas, Alain
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p. 1895 - 1908
(2015/06/02)
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- Asymmetric synthesis of dihydroindanes by convergent alkoxide-directed metallacycle-mediated bond formation
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A convergent synthesis of highly substituted and stereodefined dihydroindanes is described from alkoxide-directed Ti-mediated cross-coupling of internal alkynes with substituted 4-hydroxy-1,6-enynes (substrates that derive from 2-directional functionaliza
- Greszler, Stephen N.,Reichard, Holly A.,Micalizio, Glenn C.
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supporting information; scheme or table
p. 2766 - 2774
(2012/03/22)
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- Asymmetric aminolysis of aromatic epoxides: A facile catalytic enantioselective synthesis of anti-β-amino alcohols
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The first asymmetric aminolysis of trans-aromatic epoxides with anilines is described. The process affords enantioenriched anti-β-amino alcohols in up to 99% ee. The complete regio- and diastereoselectivity observed uses commercially available [Cr(Salen)CI] as a Lewis acid catalyst and in combination with a very simple experimental procedure renders the present reaction a facile and practical tool for the synthesis of chiral nonracemic anti-β-amino alcohols.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Massaccesi, Massimo,Melchiorre, Paolo,Sambri, Letizia
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p. 2173 - 2176
(2007/10/03)
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- Selective reductive cleavage of 2,3-epoxybromides by the InCl 3-NaBH4 reagent system
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A combination of sodium borohydride and a catalytic amount of indium(III) chloride in acetonitrile reduces 2,3-epoxybromides to the corresponding allylic alcohols in good yields involving reduction of the bromo moiety followed by selective C-O bond cleavage through a radical process. Several aromatic, cyclic and open-chain bromoepoxides successfully participated in this reaction.
- Ranu, Brindaban C.,Banerjee, Subhash,Das, Arijit
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p. 8579 - 8581
(2007/10/03)
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- Stereospecific isomerization of 3-substituted-3-bromo-1,2-epoxypropanes using magnesium bromide
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A novel stereospecific isomerization reaction of 3-substituted-3-bromo-1,2-epoxypropane derivatives into 1-substituted-3-bromo-1,2-epoxypropane derivatives is described. The choice of the solvent crucially influences the isomerization. The tendency of this isomerization could be predicted by comparison of the free energies calculation using ab initio and DFT methods.
- Karikomi, Michinori,Takayama, Takeshi,Haga, Kazuo
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p. 4487 - 4490
(2007/10/03)
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- Irreversible inhibition of the HIV-1 protease: Targeting alkylating agents to the catalytic aspartate groups
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Irreversible inhibition of the HIV-1 protease by agents that specifically alkylate its catalytic aspartate residues is a potentially useful approach for circumventing the evolution of HIV strains that are resistant to protease inhibitors. Five haloperidol- and two FMOC-based epoxides of differing reactivities have been synthesized and tested as irreversible inhibitors of the HIV-1 protease (HIV-1 PR). Of these, two trisubstituted epoxides, a cis-1,2-disubstituted epoxide, a 1,1-disubstituted epoxide, and a monosubstituted epoxide function as irreversible inhibitors, but two trans-1,2-disubstituted epoxides do not. The most effective of the epoxides (6) inactivates HIV-1 PR with K(inact) = 65 μM and V(inact) = 0.009 min-1. 1,2-Epoxy-3-(p-nitrophenoxy)propane (EPNP), a nonspecific inactivating agent for aspartyl proteases, has been used to validate a protocol for establishing the stoichiometry and site of protein alkylation. Mass spectrometric analysis of the inactivated enzyme shows that one molecule of either EPNP or the cyclic 1,2-disubstituted epoxide 6 is covalently bound per HIV-1 PR dimer. Mass spectrometric sequencing of labeled proteolytic peptides shows that both inhibitors are covalently bound to a catalytic aspartate residue. The covalent binding of three α,β-unsaturated ketone derivatives of haloperidol has been similarly examined. Analysis of HIV-1 PR inactivated by these agents establishes that they bind covalently to the two cysteines and the N-terminal amino group but not detectably to the catalytic aspartate residues. The results indicate that aspartate-targeted inactivation of HIV-1 PR depends on (a) matching the reactivity of the alkylating functionality to that of the aspartates, preferably by exploiting the two-aspartate catalytic motif of the protease to activate the alkylating agent, and (b) appropriate positioning of the alkylating functionality within the active site. These requirements are readily met by a monosubstituted, 1,1-disubstituted, or cyclic cis-1,2-disubstituted epoxide but not by trans-1,2-disubstituted epoxides or α,β-unsaturated ketones.
- Yu,Caldera,McPhee,De Voss,Jones,Burlingame,Kuntz,Craik,Ortiz De Montellano
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p. 5846 - 5856
(2007/10/03)
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- Rearrangement Reactions of Epoxides in the Presence of 2-Mercaptopyridine N-Oxide Sodium Salt.
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Reaction of glycidyl bromides and tosylates with sodium salt of mercaptopyridine N-oxide led to the formation of episulphides.
- Lampard, Christopher,Murphy, John A.,Lewis, Norman
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p. 3841 - 3848
(2007/10/02)
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- Cleavage of 2,3-Epoxyalkylhalides by the Sonochemical Zinc-Copper Couple
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2,3-Epoxyalkylhalides are readily transformed into allylic alcohols when sonicated in the presence of a zinc-copper couple in aqueous ethanol.
- Sarandeses, Luis A.,Mourino, Antonio,Luche, Jean-Louis
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p. 818 - 820
(2007/10/02)
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- A Novel Probe for Free Radicals featuring Epoxide Cleavage
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This paper describes the identification of carbon-carbon bond cleavage within a defined range of epoxides as being a reaction type which is specifically diagnostic of free radicals adjacent to the epoxide.The speed of the epoxide cleavage is greater than
- Dickinson, Julia M.,Murphy, John A.,Patterson, Christopher W.,Wooster, Nicholas F.
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p. 1179 - 1184
(2007/10/02)
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