- Bu4NHSO4-Catalyzed Direct N-Allylation of Pyrazole and its Derivatives with Allylic Alcohols in Water: A Metal-Free, Recyclable and Sustainable System
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Allylic amines are valuable and functional building blocks. Direct N-allylation of pyrazole and its derivatives as an atom economic strategy to provide allylic amines has been achieved only using commercial Bu4NHSO4 as the metal-free catalyst and water as the solvent without any additives. 11–93% isolated yields were obtained for the N-allylation of pyrazole and its derivatives with allylic alcohols. Bu4NHSO4 could be reused for six times by simple extraction nearly without loss of catalytic activity and was also suitable for a gram-scale production. The reaction of allylic ether and pyrazole did not occur to give the desired product indicated that allylic ether was not the active intermediate in the pathway. Density functional theory (DFT) calculations reveal that there are hydrogen bonding effects among substrates, solvent and catalyst, especially the one formed between allylic alcohol and H2O. Control experiments in different protic solvents further demonstrate the intermolecular hydrogen bonding of allylic alcohol and water. (Figure presented.).
- Zhuang, Hongfeng,Lu, Nan,Ji, Na,Han, Feng,Miao, Chengxia
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p. 5461 - 5472
(2021/09/29)
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- Chlorination of benzylic and allylic alcohols with trimethylsilyl chloride enhanced by natural sodium montmorillonite
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A new and practical method for the efficient chlorination of tertiary, secondary, and primary benzylic and allylic alcohols is described. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion. During the process, sodium ion-exchanged montmorillonite plays a crucial role in capturing the generated hydrogen chloride, stabilizing the carbenium intermediate as well as promoting the chlorination.
- Tandiary, Michael Andreas,Masui, Yoichi,Onaka, Makoto
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supporting information
p. 2639 - 2643
(2015/01/09)
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- Chemoselective reduction of the carbonyl functionality through hydrosilylation: Integrating click catalysis with hydrosilylation in one pot
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Herein we report the chemoselective reduction of the carbonyl functionality via hydrosilylation using a copper(I) catalyst bearing the abnormal N-heterocyclic carbene 1 with low (0.25 mol %) catalyst loading at ambient temperature in excellent yield within a very short reaction time. The hydrosilylation reaction of α,β-unsaturated carbonyl compounds takes place selectively toward 1,2-addition (C=O) to yield the corresponding allyl alcohols in good yields. Moreover, when two reducible functional groups such as imine and ketone groups are present in the same molecule, this catalyst selectively reduces the ketone functionality. Further, 1 was used in a consecutive fashion by combining the Huisgen cycloaddition and hydrosilylation reactions in one pot, yielding a range of functionalized triazole substituted alcohols in excellent yields.
- Roy, Sudipta Raha,Sau, Samaresh Chandra,Mandal, Swadhin K.
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p. 9150 - 9160
(2014/12/11)
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- Electrophilic addition of allylic carbocations to 2-cyclopropylidene-2- arylethanols: A strategy to 3-oxabicyclo[3.2.0]heptanes
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We have developed an electrophilic addition of allylic carbocations to 2-cyclopropylidene-2-arylethanols constructing carbon-carbon bonds with excellent regio- and stereoselectivities. The reaction affords 3-oxabicyclo[3.2.0]heptanes in moderate to good y
- Meng, Bo,Huang, Xian,Wu, Luling
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p. 2637 - 2650
(2013/10/21)
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- Zirconium borohydride piperazine complex, an efficient, air and thermally stable reducing agent
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A zirconium borohydride piperazine complex (Ppyz)Zr(BH4) 2Cl2, obtained by the reaction of an ethereal solution of ZrCl4 and LiBH4 with piperazine is a stable, selective and efficient reducing agent. (Ppyz)Zr(BH4)2Cl 2 reduces aldehydes, ketones, silylethers, α, β-unsaturated carbonyl compounds and esters. The reactions were performed in diethyl ether at room temperature or under reflux, and the yields of the corresponding alcohols were excellent. The selective reduction of aldehydes in the presence of ketones and complete regioselectivity in the reduction of α,β-unsaturated carbonyl groups were observed.
- Tajbakhsh,Lakouraj,Shirini,Habibzadeh,Nikdoost
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p. 3295 - 3299
(2007/10/03)
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- Substrate binding in the asymmetric dihydroxylation reaction - Investigation of the stereoselectivity in the dihydroxylation of Cs-symmetric divinylcarbinol derivatives
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The mechanism of the asymmetric dihydroxylation (AD) reaction has been hotly disputed. We have studied the stereochemical outcome of the AD reaction on a series of Cs-symmetric divinylcarbinol derivatives in order to shed light on the binding mode of the substrate to the osmium tetroxide-ligand complex. The product distribution is dependent on the size of the allylic substituent, and on the type and class of ligand. It is postulated that the diastereospecificity of the reactions originates from attractive forces between the substrate and the ligand. These interactions are independent of the interactions responsible for the enantioselectivity in the AD reaction.
- Bayer, Annette,Svendsen, John S.
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p. 1769 - 1780
(2007/10/03)
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- Equilibrium acidities of some α,ω-diphenylpolyenes
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Cesium ion pair acidities were measured in THF for a series of diphenylmethane vinylogues that form α,ω-diphenylpolyenyl anions with linearly conjugated chains of 3-9 carbon atoms. The dissociation constants of the diphenylpolyenyls in THF were determined by UV-vis spectroscopy and are rationalized with an electrostatic model. Acidity and dissociation data were combined with measurements of stereoisomer equilibria to estimate the differences in delocalization energy among the diphenylpolyenyl ions. The experimental differences in acidity correlate well with AMI and molecular mechanics (MMPI) calculations.
- Thiele, Georg,Streitwieser, Andrew
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p. 446 - 454
(2007/10/02)
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- Fluorescence of α,ω-diphenylpolyenyl carbocations
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The fluorescence lifetimes of the α,ω-diphenylpolyenyl carbocations in CH2Cl2 solution increase with decreasing temperature toward limiting values. This behavior is very similar to that of the corresponding α,ω-diphenylpolyenyl carba
- Young,Brocklehurst,Booth
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p. 7885 - 7888
(2007/10/02)
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- BOROHYDRIDE REDUCING AGENT DERIVED FROM ANION EXCHANGE RESIN : SELECTIVE REDUCTION OF α, β-UNSATURATED CARBONYL COMPOUNDS.
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Borohydride exchange resin (BER) exhibited selectivity in the reduction of α, β-unsaturated carbonyl compounds to the corresponding unsaturated alcohols.
- Sande, A. R.,Jagadale, M. H.,Mane, R. B.,Salunkhe, M. M.
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p. 3501 - 3504
(2007/10/02)
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- Organotin Nucleophiles. 5. Palladium-Catalyzed Allylic Propargylation with Allenylstannane
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Allenyltrialkylstannanes were found to react with various allylic acetates in the presence of catalytic amounts of Pd(PPh3)4 under mild neutral conditions, providing a novel approach for obtaining the 1,5-enyne carbon skeleton.The regioselectivity of propargylation depends largely on the electron-withdrawing properties of the substituents at the two ends of the allylic system: substitution occurs at the end of closer proximity to the more electronegative group.Allylic cyanohydrin acetates are substituted at a position α to the cyano group along with formation of a reduced side product.Several mechanistic aspects of these reactions are discussed.
- Keinan, Ehud,Peretz, Moshe
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p. 5302 - 5309
(2007/10/02)
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