- Ni-Catalyzed Formal Cross-Electrophile Coupling of Alcohols with Aryl Halides
-
Direct coupling of unactivated alcohols remains a challenge in current synthetic chemistry. We herein demonstrate a strategy building upon in situ halogenation/reductive coupling of alcohols with aryl halides to forge Csp2-Csp3 bonds. The combination of 2-chloro-3-ethylbenzo[d]oxazol-3-ium salt (CEBO) and TBAB as the mild bromination reagents enables rapid transformation of a wide range of alcohols to their bromide counterparts within one to 5 min in CH3CN and DMF, which is compatible with the Ni-catalyzed cross-electrophile coupling conditions in the presence of a chemical reductant. The present method is suitable for arylation of a myriad of structurally complex alcohols with no need for prepreparation of alkyl halides. More importantly, the mild and kinetically rapid bromination process has shown good selectivity in the bromination/arylation of symmetric diols and less sterically hindered hydroxyl groups in polyols, thus offering promise for selective functionalization of diols and polyols without laborious protecting/deprotecting operations. The practicality of this work is also evident in the arylation of a number of carbohydrates, drug compounds, and naturally occurring alcohols.
- Lin, Quan,Ma, Guobin,Gong, Hegui
-
p. 14102 - 14109
(2021/11/20)
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- Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides
-
A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) and biimidazoline (BiIm) ligands revealed that enantioselectivity correlates with electronic properties of the ligands, with more electron-donating ligands affording higher ee's. Experimental and computational mechanistic studies were conducted, lending support to the hypothesis that reductive elimination is enantiodetermining and the electronic character of the ligands influences the enantioselectivity by altering the position of the transition state structure along the reaction coordinate. This study demonstrates the benefits of utilizing statistical modeling as a platform for mechanistic understanding and provides new insight into an emerging class of chiral ligands for stereoconvergent Ni and Ni/photoredox cross-coupling.
- Lau, Sii Hong,Borden, Meredith A.,Steiman, Talia J.,Wang, Lucy S.,Parasram, Marvin,Doyle, Abigail G.
-
supporting information
p. 15873 - 15881
(2021/10/12)
-
- Use of allylzinc halide as a source of halide: Differential addition of nucleophiles to Ts-aziridines and aldehydes under similar reaction conditions
-
We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compou
- Chatterjee, Rana,Samanta, Satyajit,Mukherjee, Anindita,Santra, Sougata,Zyryanov, Grigory V.,Majee, Adinath
-
supporting information
p. 276 - 283
(2019/01/04)
-
- A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
-
A versatile iridium(III) metallacycle catalysed rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. The reactions proceeded in high yields at room temperature by hydrosilylation followed by desilylation. Although the reactions of various aldehydes and ketones resulted exclusively in alcohols, the hydrosilylation of esters led to alcohols or ethers, depending on the type of substrate. Regarding the carboxylic acids, again the nature of the reagent controlled the outcome of the hydrosilylation reaction, either alcohols or aldehydes being formed.
- Corre, Yann,Rysak, Vincent,Trivelli, Xavier,Agbossou-Niedercorn, Francine,Michon, Christophe
-
supporting information
p. 4820 - 4826
(2017/09/07)
-
- LiBr/β-CD/IBX/H2O-DMSO: A new approach for one-pot biomimetic regioselective ring opening of chalcone epoxides to bromohydrins and conversion to 1,2,3-triketones
-
Highly regioselective ring cleavage of chalcone epoxides to bromohydrins has been carried out in good yields with LiBr in the presence of β-CD using DMSO-H2O as solvent system. The ring-opened product, i.e., bromohydrin, was well adapted to IBX-mediated oxidation in such a fashion that the bromohydrins are transformed to their corresponding 1,2,3-triketones in moderate-to-good yields in one pot.
- Verma, Nishant,Kumar, Sumit,Ahmed, Naseem
-
p. 1110 - 1120
(2017/05/25)
-
- C-ON bond homolysis of alkoxyamines: When too high polarity is detrimental
-
Throughout the last decade, the effect of electron withdrawing groups (EWGs) has been known to play a role-minor or moderate depending on the nitroxyl fragment R1R2NO-in the change in the homolysis rate constant (kd) for C-ON bond homolysis in alkoxyamines (R1R2NOR). It has been shown that the effect of EWGs on kd is described by a linear relationship with the electrical Hammett constant σI. Since then, linear multi-parameter relationships f(σRS,ν,σI) have been developed to account for the effects involved in the changes in kd, which are the stabilization of the released radical (σRS) and the bulkiness (ν) and polarity (σI) of the alkyl fragment. Since a decade ago, new results have been published highlighting the limits of such correlations. In this article, previous multi-parameter linear relationships are amended using a parabolic model, i.e. (σI,nitroxide - σI,alkyl)2, to describe the effect of EWGs in the alkyl fragment on kd. In contrast to previous studies, these improved linear multi-parameter relationships f(σRS,ν,ΔσI2) are able to account for the presence of several EWGs on the alkyl fragment, R. An unexpectedly strong solvent effect-a ca. 1500-fold increase in kd-from tert-butylbenzene to the water/methanol mixture is also observed for 3-((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)pentane-2,4-dione 1b in comparison to a ca. 5-fold increase in kd that is generally observed.
- Nkolo, Paulin,Audran, Gérard,Bikanga, Raphael,Brémond, Paul,Marque, Sylvain R. A.,Roubaud, Valérie
-
p. 6167 - 6176
(2017/08/02)
-
- Direct halogenation of alcohols with halosilanes under catalyst- and organic solvent-free reaction conditions
-
A chemoselective method for the direct halogenation of different types of alcohols with halosilanes under catalyst- and solvent-free reaction conditions (SFRC) is reported. Various primary, secondary and tertiary benzyl alcohols and tertiary alkyl alcohols were directly transformed to the corresponding benzyl and alkyl halides, respectively, using chlorotrimethylsilane (TMSCl) and bromotrimethylsilane (TMSBr).
- Ajvazi, Njomza,Stavber, Stojan
-
supporting information
p. 2430 - 2433
(2016/05/19)
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- Trihaloisocyanuric Acid/Triphenylphosphine: An Efficient System for Regioselective Conversion of Epoxides into Vicinal Halohydrins and Vicinal Dihalides under Mild Conditions
-
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)
-
- Design, synthesis, and biological evaluation of crenatoside analogues as novel influenza neuraminidase inhibitors
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Natural products, especially derived from TCMH, have been found to exert antiviral effects against influenza virus. Crenatoside, a phenylethanoid glycoside from Pogostemon cablin Benth, which has been shown as a novel effective NA inhibitor previously, is considered as the leading compound for our further SARs studies. This work presented design, synthesis of novel crenatoside analogues from readily available d-Glucose and l-rhamnose in a convergent manner. Furthermore, their biological activities and SARs were also investigated. Especially, compound 2 h showed impressive IC50 = 27.77 μg/mL against NAs, which is 3 folds more potent than the leading compound crenatoside (IC50 = 89.81 μg/mL). These results would promise their therapeutic potential for influenza disease.
- Chen, Bao-Long,Wang, Ya-Jing,Guo, Hong,Zeng, Guang-Yao
-
p. 199 - 205
(2016/01/16)
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- Triphenylphosphine-N-bromosuccinimide mediated chemoselective cyclodehydration of diols
-
A triphenylphosphine-N-bromosuccinimide mediated chemoselective cyclodehydration of diols is presented for the synthesis of polysubstituted tetrahydrofurans. 1,4-Diols and their derivatives can be rapidly cyclized to furnish tetrahydrofurans in high yields with one equivalent of Ph3P/NBS. Higher amount of Ph3P/NBS leads to the formation of dibromobutanes.
- Zhao, Shuo,Wu, You,Sun, Qi,Cheng, Tie-Ming,Li, Run-Tao
-
p. 1154 - 1162
(2015/04/14)
-
- Synthesis of diversely functionalised 2,2-disubstituted oxetanes: Fragment motifs in new chemical space
-
Di-, tri- and tetra-substituted oxetane derivatives with combinations of ester, amide, nitrile, aryl, sulfone and phosphonate substituents are prepared as fragments or building blocks for drug discovery. The synthesis of these novel oxetane functional groups, in new chemical space, is achieved via rhodium-catalysed O-H insertion and C-C bond forming cyclisation.
- Davis, Owen A.,Croft, Rosemary A.,Bull, James A.
-
supporting information
p. 15446 - 15449
(2015/10/20)
-
- Bifunctional aluminum catalyst for CO2 fixation: Regioselective ring opening of three-membered heterocyclic compounds
-
Regioselective ring opening of three-membered heterocyclic compounds (epoxides or N-substituted aziridines) at various temperatures was observed in coupling reactions with CO2 by the use of an aluminum - salen catalyst in conjunction with intramolecular quaternary ammonium salts as cocatalysts, affording the corresponding five-membered cyclic products with complete configuration retention at the methine carbon. Notably, this bifunctional aluminum-based catalyst exhibited nearly 100% regioselectivity for the ring opening at the methylene C-O bond for various terminal epoxides. This was true for those bearing an electron-withdrawing group, such as styrene oxide or epichlorohydrin, thereby affording the synthesis of various enantiopure cyclic carbonates that have previously been obtained only rarely by other methods. An intramolecular cooperative catalysis is suggested to contribute to the high activity and excellent stereochemistry control observed. Surprisingly, the highly selective ring opening at the methine carbon of N-substituted aziridines was found in the coupling with CO2, predominantly giving 5-substituted oxazolininones with retention of configuration as a result of double inversion at the methine carbon. (Chemical Equation Presented).
- Ren, Wei-Min,Liu, Ye,Lu, Xiao-Bing
-
p. 9771 - 9777
(2015/02/19)
-
- Synthesis, characterization and catalytic activity of dioxidomolybdenum(VI) complexes of tribasic pentadentate ligands
-
[MoVIO2(acac)2] (Hacac = acetylacetone) reacts with the tribasic pentadentate Schiff bases H3sal-dahp (I), H3clsal-dahp (II) and H3brsal-dahp (III) (sal = salicylaldehyde, clsal = 5-chlorosalicylaldehyde, brsal = 5- bromosalicylaldehyde, dahp = 1,3-diamino-2-hydroxypropane) in methanol under refluxing conditions to yield the dioxidomolybdenum(VI) complexes [Mo VIO2(Hsal-dahp)(H2O)] (1), [Mo VIO2(Hclsal-dahp)(H2O)] (2) and [Mo VIO2(Hbrsal-dahp)(H2O)] (3), respectively. In these complexes, only one set of phenolic oxygen and azomethine nitrogen atoms, along with the alcoholic oxygen atom of the ligands coordinate to the molybdenum. The reactions of these complexes with pyridine result in the formation of [MoVIO2(Hsal-dahp)(py)] (4), [Mo VIO2(Hclsal-dahp)(py)] (5) and [MoVIO 2(Hbrsal-dahp)(py)] (6). A single crystal X-ray study of [Mo VIO2(Hbrsal-dahp)(DMSO)] (3a), grown by slow evaporation of a DMSO solution of 3, confirms the non-participation of one set of phenolic oxygen and azomethine nitrogen atoms of the ligand. The reaction of a methanolic solution of the in situ generated H3clsal-dahp with [Mo VIO2(acac)2] in DMSO gave [Mo VIO2(Hclsal-hdap)(DMSO)]4[Mo8O 26]·6DMSO (7) (H2clsal-hdap = Schiff base obtained by the 1:1 condensation of 5-chlorosalicylaldehyde and 1,3-diamino-2- hydroxypropane), where the non-coordinated azomethine nitrogen hydrolyzes giving a free protonated amine group, as confirmed by a single crystal X-ray study. Complexes 1, 2 and 3 catalyze the oxidative bromination of styrene to yield 1,2-dibromo-1-phenylethane, 1-phenylethane-1,2-diol and 2-bromo-1-phenylethane- 1-ol; therefore they act as functional models of vanadium dependent haloperoxidases. It has also been demonstrated that complexes 1, 2 and 3 are catalyst precursors for the oxidation of methyl phenyl sulfide and benzoin.
- Maurya, Mannar R.,Dhaka, Sarita,Avecilla, Fernando
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p. 145 - 159
(2013/10/22)
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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
-
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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- H2TPP organocatalysis in mild and highly regioselective ring opening of epoxides to halo alcohols by means of halogen elements
-
We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H2TPP). Therefore a highly regioselective method for the synthesis of β-haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H2TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present.
- Torabi, Parviz,Azizian, Javad,Zomorodbakhsh, Shahab
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scheme or table
p. 5508 - 5519
(2012/08/28)
-
- Synthesis of silica bromide as heterogeneous reagent and its application to conversion of alcohols to alkyl bromides
-
Silica bromide as heterogeneous reagent is prepared from the reaction of silica gel with PBr3 as a nonhydroscopic, filterable, cheap, and stable yellowish powder that can be stored for months. The results show that the silica bromide is a suitable and efficient reagent for conversion of alcohols to alkyl bromides under mild conditions at room temperature. The easy availability of this reagent makes this simple procedure attractive and a practical alternative to the existing methods.
- Mohanazadeh, Farajollah,Sedrpoushan, Alireza,Zolfigol, Mohammad A.,Veisi, Hojat
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p. 598 - 603,6
(2012/12/11)
-
- Mild organic ammonium tribromide-mediated regioselective ring opening of epoxides with alcohols, water, acetic anhydride, and amines under solvent-free reaction conditions
-
Organic ammonium tribromide (OATB), N-methylpyrrolidine-2-one hydrotribromide (MPHT) was found to be an efficient catalyst for the regioselective ring opening of epoxides with various nucleophiles under solvent free conditions. This procedure occurs under neutral and mild reaction conditions with out adding any additive and afforded high yields of products.
- Singhal, Sweety,Jain, Suman L.,Sain, Bir
-
experimental part
p. 1829 - 1837
(2011/06/19)
-
- Synthesis, characterization and structure of DBU-hydrobromide-perbromide: A novel oxidizing agent for selective oxidation of alcohols to carbonyl compounds
-
A new and efficient reagent for the conversion of primary and secondary alcohols into their corresponding aldehydes and ketones is introduced. The reagent was easily prepared from the reaction of DBU with molecular bromine in CHCl3. The structure of the reagent as DBUH+Br 3- was determined by single crystal X-ray diffraction analysis.
- Bakavoli, Mehdi,Rahimizadeh, Mohammad,Eshghi, Hossein,Shiri, Ali,Ebrahimpour, Zahra,Takjoo, Reza
-
scheme or table
p. 949 - 952
(2010/10/18)
-
- Allyltin tribromide: A versatile reagent involved in the ring-opening of epoxides
-
This paper presents a versatile reagent for epoxide cleavage. The allyltin tribromide could act as a novel and easily prepared allylation reagent and halide atom donor to convert epoxides to the corresponding homoallyl alcohols and halohydrins in high yields with excellent regioselectivities under mild reaction conditions, respectively. It could also act as a Lewis acid to catalyze the ring opening reactions of epoxides with alcohols.
- Chen, Guohong,Wang, Xin,Jin, Xiaoqian,Liu, Lingyan,Chang, Weixing,Li, Jing
-
experimental part
p. 1294 - 1301
(2010/11/05)
-
- An efficient and convenient protocol for highly regioselective cleavage of terminal epoxides to β-Halohydrins
-
An efficient and facile strategy for the cleavage of terminal epoxides to β-halohydrins using active magnesium halides is described. The conversion proceeds smoothly at room temperature with high regioselectivity and good yields even when sensitive functional groups are present. Georg Thieme Verlag Stuttgart.
- Wang, Tao,Ji, Wen-Hao,Xu, Zhong-Yu,Zeng, Bu-Bing
-
experimental part
p. 1511 - 1513
(2009/10/23)
-
- Monobromoborane-dimethyl sulfide - A highly promising reagent for the regio- and chemoselective brominative cleavage of terminal epoxides into vicinal bromohydrins
-
Monobromoborane?dimethyl sulfide (BH2Br?SMe2) is a highly regio- and chemoselective reagent useful for the brominative cleavage of the epoxy moiety into bromohydrins in the presence of alkenes, alkynes, ethers, acetals, ketals, and acetonides at 0°C, besides being an excellent hydroborating reagent. Several reactive functional groups, such as chloride, ketones, esters, nitriles, nitros, and thioethers, have been accommodated during such transformations. Although the reduction of acetophenone was completely suppressed at ?25°C, 4-chlorobenzaldehyde still underwent 12?13% reduction of an aldehydic group. CSIRO 2007.
- Roy, Chandra D.,Brown, Herbert C.
-
p. 139 - 145
(2008/02/11)
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- A highly regio- and chemoselective synthesis of vicinal bromohydrins by ring opening of terminal epoxides with dibromoborane-dimethyl sulfide
-
Dibromoborane-dimethyl sulfide (BHBr2-SMe2) displays high degrees of chemo- and regioselectivity during the brominative cleavage of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydroborating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have been successfully accommodated during the epoxide opening process.
- Roy, Chandra D.,Brown, Herbert C.
-
p. 1608 - 1613
(2007/10/03)
-
- 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
-
-
- Silphos [PCl3-n (SiO2)n]: A heterogeneous phosphine reagent for the regioselective synthesis of vic-haloalcohols
-
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
-
p. 2615 - 2621
(2007/10/03)
-
- Dimethoxyboron bromide - A new, efficient, regio- and chemoselective reagent for the conversion of terminal epoxides into bromohydrins
-
Dimethoxyboron bromide, (MeO)2BBr, easily prepared in excellent yield from boron tribromide and trimethyl borate, is a new, efficient, regio- and chemoselective reagent useful for the halogenative cleavage of compounds containing epoxy groups into vicinal bromohydrins in the presence of ether, acetal, ketal, N-oxide, and sulfoxide groups, at low temperatures (-78°C).
- Roy, Chandra D.,Brown, Herbert C.
-
p. 639 - 641
(2007/10/03)
-
- Chemoselective conversion of aromatic epoxide and 1,2-diol to 1,3-dioxane derivatives with phenyltrimethylammonium tribromide in the presence of a catalytic amount of antimony(III) bromide
-
trans-Stilbene oxide was oxidatively converted to 2-phenyl-1,3-dioxanes with phenyltrimethylammonium tribromide in the presence of various 1,3-diols and a catalytic amount of SbBr3 in DMSO at room temperature. Aromatic 1,2-diol, such as hydrobenzoin, was similarly converted to 2-aryl-1,3-dioxane derivatives under the same reaction conditions.
- Sayama, Shinsei
-
p. 4001 - 4005
(2007/10/03)
-
- Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide
-
Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time.
- Das, Biswanath,Krishnaiah, Maddeboina,Venkateswarlu, Katta
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p. 4457 - 4460
(2007/10/03)
-
- A mild and efficient procedure for the oxidation of epoxides and aziridines using cerium(IV) ammonium nitrate and NBS
-
The CAN and NBS combination has been used for the first time for the synthesis of versatile α-hydroxy ketones and α-amino ketones from oxiranes/aziridines, respectively, in excellent yields. This method is a direct, one-pot, synthesis under mild conditions using acetonitrile-water (9:1) as solvent.
- Surendra,Srilakshmi Krishnaveni,Rama Rao
-
p. 4111 - 4113
(2007/10/03)
-
- Green protocol for the synthesis of vicinal-halohydrins from oxiranes using the [Bmim]PF6/LiX reagent system
-
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
-
p. 476 - 477
(2007/10/03)
-
- 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
-
p. 1885 - 1891
(2007/10/03)
-
- A New Regioselective Synthesis of Vicinal Bromohydrins via Free Radical Decarboxylative Bromination of β-Hydroxycarboxylic Acids
-
Diisopropylcarbodiimide-mediated condensations between N-hydroxypyridine- 2(1H)-thione and β-hydroxycarboxylic acids afforded mixed anhydrides which were regioselectively converted into vicinal bromohydrins under neutral conditions.
- Greb, Marco,Hartung, Jens
-
-
- Micellar media for the efficient ring opening of epoxides with CN-, N3-, NO3-, NO2-, SCN-, Cl- and Br- catalyzed with Ce(OTf)4
-
Micellar media are introduced for the efficient ring opening of epoxides with sodium salts of nucleophiles such as CN, N3-, NO3-, NO2, SCN, Br and Cl-, catalyzed with Ce(OTf)4. This method is an efficient procedure for the synthesis of different β-substituted alcohols under mild reaction conditions. The reaction with SCN- is an easy procedure for the high yielding preparation of epoxy sulfides.
- Iranpoor, Nasser,Firouzabadi, Habib,Shekarize, Marzieh
-
p. 724 - 727
(2007/10/03)
-
- Conversion of epoxides into halohydrins with elemental halogen catalyzed by thiourea
-
A highly regioselective method for the synthesis of β-iodohydrins and β-bromohydrins by the direct ring opening of epoxides with elemental halogen in the presence of thiourea is described. This method occurs under neutral and mild conditions with high yields in various solvents even when sensitive functional groups are present.
- Sharghi, Hashem,Eskandari, Mohammad Mehdi
-
p. 8509 - 8514
(2007/10/03)
-
- Reactions of epoxides and episulfides with electrophilic halogens
-
A novel method is described for the conversion of epoxides into β-bromoformates using Ph3PBr2, Ph3P/N-bromosuccinimdes (NBS) and or Ph3P/2,4,4,6-tetrabromo-2,5-cyclohexadiene-1-one (TABCO) in DMF. Epoxides in the presence of Ph3P/I2 were converted into olefins immediately in excellent yields. The application of NBS, NCS, and TABCO as compounds carrying electrophilic halogens for the highly selective alcoholysis of epoxides and dimerization or alcoholysis dimerization of episulfides are also described.
- Iranpoor, Nasser,Firouzabadi, Habib,Chitsazi, Maryam,Ali Jafari, Abbas
-
p. 7037 - 7042
(2007/10/03)
-
- Conversion of epoxides to halohydrins with elemental halogen catalyzed by phenylhydrazine
-
The highly regioselective method for the synthesis of β-iodohydrins and β-bromohydrins by the direct ring opening of 1,2-epoxides with elemental halogen in the presence of phenylhydrazine is described. This method occurs under neutral and mild conditions with high yields in various aprotic solvents even when sensitive functional groups are present.
- Sharghi, Hashem,Eskandari, Mohammad Mehdi
-
p. 1519 - 1522
(2007/10/03)
-
- Observations on the use of triphenylphosphonium bromide as a mild and quantifiable source of hydrogen bromide for chemoselective ring opening of epoxides to bromohydrins
-
The chemoselective ring opening of epoxides to bromohydrins in the presence of ketal, benzyloxymethoxy and trimethylsilyl ether functionality using triphenylphosphonium bromide is described. The preparation of a polymer supported variant is also reported.
- Afonso, Carlos A.M.,Vieira, Nuno M.L.,Motherwell, William B.
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p. 382 - 384
(2007/10/03)
-
- Iron(III) trifluoroacetate as an efficient catalyst for solvolytic and nonsolvolytic nucleophilic ring opening of epoxides
-
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
-
p. 675 - 680
(2007/10/03)
-
- 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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- A general approach towards 2-substituted 3-hydroxy propanoates; application to the synthesis of methyl tropinate
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Enantiomerically pure R or S 2-substituted 3-hydroxy propanoates may be prepared by regioselective BF3 promoted opening of homochiral styrene oxide by lithium cyanocuprates followed by oxidative cleavage of the aromatic moiety with catalytic ru
- Imogai, Hassan,Larcheveque, Marc
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p. 965 - 972
(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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- A facile conversion of epoxides to β-halohydrins with silica gel-supported lithium halides
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A variety of epoxides are efficiently converted to the corresponding β-halohydrins with lithium halides supported on silica gel in dry media.
- Kotsuki, Hiyoshizo,Shimanouchi, Tomoyasu
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p. 1845 - 1848
(2007/10/03)
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- Design, synthesis, and evaluation of latent alkylating agents activated by glutathione S-transferase
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In search of compounds with improved specificity for targeting the important cancer-associated P1-1 glutathione S-transferase (GST) isozyme, new analogs 4 and 5 of the previously reported glutathione S-transferase (GST)- activated latent alkylating agent γ-glutamyl-α-amino-β-[[[2[[bis[bis(2- chloroethyl)amino]phosphoryl]oxy]ethyl]sulfonyl]propionyl]-(R)-(-)- phenylglycine (3) have been designed, synthesized, and evaluated. One of the diastereomers of 4 exhibited good selectivity for GST P1-1. The tetrabromo analog 5 of the tetrachloro compound 3 maintained its specificity and was found to be more readily activated by GSTs than 3. The GST activation concept was further broadened through design, synthesis, and evaluation of a novel latent urethane mustard 8 and its diethyl ester 9. Interestingly, 8 showed very good specificity for P1-1 GST. Cell culture studies were carried out on 4, 5, 8, and 9 using cell lines engineered to have varying levels of GST P1- 1 isozyme. New analogs 4 and 5 exhibited increased toxicity to cell lines with overexpressed GST P1-1 isozyme. The urethane mustard 8 and its diethyl ester 9 were found to be not as toxic. However, they too exhibited more toxicity to a cell line engineered to have elevated P1-1 levels, which was in agreement with the observed in vitro specificity of 8 for P1-1 GST isozyme. Mechanistic studies on alkaline as well as enzyme-catalyzed decomposition of latent mustard 3 provided experimental proof for the hypothesis that 3 breaks down into an active phosphoramidate mustard and a reactive vinyl sulfone. The alkylating nature of the decomposition products was further demonstrated by trapping those transient species as relatively stable diethyldithiocarbamic acid adducts. These results substantially extend previous efforts to develop drugs targeting GST and provide a paradigm for development of other latent drugs.
- Satyam, Apparao,Hocker, Michael D.,Kane-Maguire, Kim A.,Morgan, Amy S.,Villar, Hugo O.,Lyttle, Matthew H.
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p. 1736 - 1747
(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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- A Facile and Highly Regioselective Conversion of Epoxides to Bromohydrins Using Tetrabutylammonium Bromide and Magnesium Nitrate
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Reaction of epoxides with nBu4NBr in the presence of Mg(NO3)2 as a catalyst affords vicinal bromohydrins in excellent yields via regioselective ring opening of the unsymmetrical epoxides.
- Suh, Young-Ger,Koo, Bon-Am,Ko, Jung-Ae,Cho, Youn-Sang
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p. 1907 - 1910
(2007/10/02)
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- An easy procedure for the highly regioselective conversion of epoxides to halohydrins
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Several epoxides and epoxy alcohols have been opened to the corresponding halohydrins by lithium halides with Amberlyst in CH3CN at room temperature: the reaction proceeds in quantitative yields with high degree of regioselectivity.
- Bonini,Giuliano,Righi,Rossi
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p. 1863 - 1870
(2007/10/02)
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- SULFUR INHIBITORS OF PHOSPHOLIPASE A-Z
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Phospholipase A2 inhibitors having the formula wherein R" is a C2-C20 alkyl group, R1" is a C1-C4 alkyl group, y is an integer from 2 to 10, and J- is a pharmaceutically acceptable anion, are described
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- Regio- and Stereoselective Synthesis of β-Halohydrins from 1,2-Epoxides with Ammonium Halides in the Presence of Metal Salts
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A simple efficient, stereoselective, and regioselective method for the synthesis of β-chlorohydrins, β-bromohydrins, and β-iodohydrins by the direct opening of 1,2-epoxides with the corresponding ammonium halide in acetonitrile, in the presence of metal salts, is described.This new method appears to be of general use and competitive with the other methods previously reported.
- Chini, Marco,Crotti, Paolo,Gardelli, Cristina,Macchia, Franco
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p. 3805 - 3812
(2007/10/02)
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- REACTION OF PHENYLOXIRANE WITH GRIGNARD REAGENTS IN THE PRESENCE OF TETRAISOPROPOXYTITANIUM
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It was shown that the direction of the reaction of phenyloxirane with Grignard reagents in the presence of tetraisopropoxytitanium can be controlled, depending on the nature of the halogen and the length of the reaction.
- Sosnovskii, G. M.,Astapovich, I. V.
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p. 1082 - 1084
(2007/10/02)
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