- New P-chirogenic tert.-butyl-xantphos ligands and their application in asymmetric hydrogenation and alkylation
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The synthesis of a broad library of new P-chirogenic Xantphos ligands is reported. A special feature is 2,7-di-tert.-butyl substituents in the backbone which requires the modification of the original synthetic approach. In comparison to related ligands reported formerly the substitution has a considerable influence on the results (yield and % e.e.) of metal catalyzed reactions, e.g. asymmetric rhodium catalyzed hydrogenation of isophorone and the palladium catalyzed alkylation, respectively.
- B?rner, Armin,Gandelman, Mark,Holz, Jens,Spannenberg, Anke,Wenzel, Gudrun
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- Reduction of ketones to corresponding alcohols with magnesium metal in absolute alcohols
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Various aliphatic and aromatic ketones are treated with 10 equiv of magnesium metal in absolute methanol or ethanol to afford corresponding alcohols in very high yields at room temperature within 12 h.
- Kim, Ji Young,Kim, Hak Do,Seo, Min Jung,Kim, Hyoung Rae,No, Zaesung,Ha, Deok-Chan,Lee, Ge Hyeong
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- SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF SOME ORGANOZINC HYDRIDE COMPLEXES
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The synthesis and characterization of the monopyridine complexes of ethylzinc hydride and phenylzinc hydride are described.On treatment with TMED these complexes are converted into R2Zn3H4.TMED species through a combination of ligand-exchange and disproportionation.The formation of organozinc hydrides from ω-functionally-substituted diorganozinc compounds is only successful when the intramolecular coordination in these starting materials is weak and easily broken by pyridine.The results of these investigations are used as a basis for a discussion of the factors governing the formation of stable organozinc hydrides.The RZnH.py complexes easily reduce ketones and aldehydes, but no unusual stereoselectivity was observed in the reduction of substituted cyclohexanones.EtZnH.py reacts with an excess of pyridine with formation of the bis pyridine complex of ethyl(1,4-dihydro-1-pyridyl)zinc, a soluble compound, which is monomeric in benzene.The corresponding phenylzinc complex, however, cannot be isolated; disproportionation to Ph2Zn.2py and the bis pyridine complex of bis(1,4-dihydro-1-pyridyl)zinc occurs.
- Koning, A. J. De,Boersma, J.,Kerk, G. J. M. Van Der
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- Photochemical ring opening of cyclopropyl ketones induced by electron transfer
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Irradiation of substituted bicyclo[n.1.0]alkan-2-ones at 254 nm in the presence of triethylamine and lithium perchlorate (LiClO4) can lead to cyclopropane ring opening with cleavage of the C(1)-C(n +2) (ring enlargement) or C(1)-C(n+3) bonds.
- Cossy, Janine,Furet, Nathalie
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- Cu/SiO2-catalyzed hydrogenation of cyclohexanones under very mild conditions
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Unsubstituted and alkyl-substituted cyclohexanones, including 3-oxo-steroids, can be easily hydrogenated to the corresponding alcohols at 1 atm of H2 and 60-90°C over a 8% Cu/SiO2 non-toxic, reusable catalyst with excellent selectivity.
- Ravasio, Nicoletta,Psaro, Rinaldo,Zaccheria, Federica
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- Preparation and application of surface activated Si-MCM-41 and SBA-16 as reusable supports for reduction of cyclic ketones with preferential stereoselectivity
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An efficient and benign procedure for the reduction of a few cyclic ketones adsorbed on the activated surface of calcined Si-MCM-41 and calcined SBA-16 using NaBH4 as the reducing agent with ethanol as the medium resulted in the formation of two epimeric alcohols. After synthesis, these calcined materials were treated with concentrated HCl to activate surface silanol groups. Various instrumental techniques like FTIR, XRD, N2 sorption isotherms, FESEM, TEM and XPS were carried out to examine the pre and post activated surface of the used supports. Five cyclic ketones were reduced. Reduction of 4-tert-butylcyclohexanone yielded only trans-4-tert-butylcyclohexanol. Moreover, exclusive formation of cis-3-methylcyclohexanol (equatorial -OH) was also observed. This work offers several advantages such as a simple operational procedure, short reaction time, and high yield of the product, along with maintaining the materials' diversity. This is due to the presence of the activated silanol groups of these materials, which cause nucleophilic activation of the carbonyl group of ketones leading to faster reaction rates. Beside this, these supports can be regenerated well from the reaction mixture using a calcination treatment followed by concentrated HCl, and reused several times without causing any serious malformation in the activated surfaces. Finally, this work opens up a new direction of research for the fabrication of solid reusable supports in the reduction of cyclic ketones.
- Chaudhuri, Haribandhu,Dash, Subhajit,Sarkar, Ashis
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- Study on the selective hydrogenation of isophorone
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3,3,5-Trimethylcyclohexanone (TMCH) is an important pharmaceutical intermediate and organic solvent, which has important industrial significance. The selective hydrogenation of isophorone was studied over noble metal (Pd/C, Pt/C, Ir/C, Ru/C, Pd/SiO2, Pt/SiO2, Ir/SiO2, Ru/SiO2), and non-noble metal (RANEY Ni, RANEY Co, RANEY Cu, RANEY Fe, Ni/SiO2, Co/SiO2, Cu/SiO2, Fe/SiO2) catalysts and using solvent-free and solvent based synthesis. The results show that the solvent has an important effect on the selectivity of TMCH. The selective hydrogenation of isophorone to TMCH can be influenced by the tetrahydrofuran solvent. The conversion of isophorone is 100%, and the yield of 3,3,5-trimethylcyclohexanone is 98.1% under RANEY Ni and THF. The method was applied to the selective hydrogenation of isopropylidene acetone, benzylidene acetone and 6-methyl-5-ene-2-heptanone. The structures of the hydrogenation product target (4-methylpentan-2-one, 4-benzylbutan-2-one and 6-methyl-heptane-2-one) were characterized using 1H-NMR and 13C-NMR. The yields of 4-methylpentan-2-one, 4-benzylbutan-2-one and 6-methyl-heptane-2-one were 97.2%, 98.5% and 98.2%, respectively. The production cost can be reduced by using RANEY metal instead of noble metal palladium. This method has good application prospects. This journal is
- Xu, Lei,Sun, Shaoyin,Zhang, Xing,Gao, Haofei,Wang, Wei
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p. 4465 - 4471
(2021/02/03)
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- Heterogeneous Hydroxyl-Directed Hydrogenation: Control of Diastereoselectivity through Bimetallic Surface Composition
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Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd-Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.
- Shumski, Alexander J.,Swann, William A.,Escorcia, Nicole J.,Li, Christina W.
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p. 6128 - 6134
(2021/05/29)
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- P-CHIRAL PHOSPHINE LIGANDS AND USE THEREOF FOR ASYMMETRIC SYNTHESIS
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The present invention relates to chiral compounds with two optically active phosphorus atoms, chiral transition metal catalysts which comprise these compounds as ligands, a process for preparing the P-chiral compounds and processes for asymmetric synthesis using the chiral transition metal catalysts. The present invention specifically relates to a process for preparing an optically active carbonyl compound by asymmetric hydrogenation of a prochiral α,β-unsaturated carbonyl compound with hydrogen in the presence of an optically active transition metal catalyst according to the invention. Yet more specifically, the present invention relates to a process for the asymmetric hydrogenation of citral, and also a process for preparing optically active menthol.
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Paragraph 0920-0923
(2019/07/23)
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- Pd/C-Al-water facilitated selective reduction of a broad variety of functional groups
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The chemoselective reduction of a broad variety of functional groups by a Pd/C-Al-H2O system is described. The reduction is based on the reaction of Al with the solvent water that in situ produces hydrogen that is utilized by the supported Pd catalyst toward the hydrogenation of the target functional groups. The hydrogenations are carried out under mild conditions and provided the products in high yields and selectivity. The reduction system appeared to be effective for a broad range of functional groups, including C-C, C-N, C-O and N-O multiple bonds, aromatic rings, hydrogenolysis of C-O, C-N and C-Halogen bonds. The appropriate selection of the reaction conditions allowed the selective preparation of different products from the same substrate. The simplicity, cost, tunability and the environmentally benign character of the catalytic system offer numerous advantages over the currently available methods.
- Sch?fer,Ellstrom,Cho,T?r?k
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p. 1230 - 1234
(2017/03/20)
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- New Route to Stabilize Ruthenium Nanoparticles with Non-Isolable Chiral N-Heterocyclic Carbenes
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Ru nanoparticles (RuNPs) stabilized by non-isolable chiral N-heterocyclic carbenes (NHCs), namely SIDPhNp ((4S,5S)-1,3-di(naphthalen-1-yl)-4,5-diphenylimidazolidine) and SIPhOH ((S)-3-((1S,2R)-2-hydroxy-1,2-diphenylethyl)-1-((R)-2-hydroxy-1,2-diphenylethyl)-4,5-dihydro-3H-imidazoline), have been synthesized through a new procedure that does not require isolation of the free carbenes. The obtained RuNPs have been characterized by state-of-the-art techniques and their surface chemistry has been investigated by FTIR and solid-state MAS NMR upon the coordination of CO, which indicated the presence of free and reactive Ru sites. Their catalytic activity has been tested in various hydrogenation reactions involving competition between different sites, whereby interesting differences in selectivity were observed, but no enantioselectivity.
- Martnez-Prieto, Luis Miguel,Ferry, Anglique,Lara, Patricia,Richter, Christian,Philippot, Karine,Glorius, Frank,Chaudret, Bruno
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p. 17495 - 17502
(2016/01/25)
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- Synthesis of an ionic paramagnetic ruthenium(III) complex and its application as an efficient and recyclable catalyst for the transfer hydrogenation of ketones
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A novel ionic complex, bis[1-butyl-2-(diphenylphosphanyl)-3- methylimidazolium]tetrachloridoruthenium(III) hexafluorophosphate (2), has been synthesized and fully characterized. The single-crystal X-ray diffraction analysis showed that 2 is composed of an Ru complex cation and PF 6- anion. The cation has a highly symmetrical Ru-centered octahedron geometry with four Cl atoms in the equatorial plane and two imidazolium-substituted phosphane ligands in the axial positions. It exhibits paramagnetism due to the presence of one unpaired electron in the phosphane-ligated low-spin RuIII complex. Complex 2 exhibited good catalytic performance in the transfer hydrogenation of a wide range of ketones by using alcohols as hydrogen donors. Owing to its high polarity, good thermal stability, and insensitivity to moisture and oxygen, complex 2 could be used in six catalytic cycles in the transfer hydrogenation of acetophenone without any obvious loss of activity. A novel ionic complex 2 containing an RuIII cation and PF6- anion has been synthesized. The Ru III cation possesses ideal octahedral geometry and exhibits paramagnetism due to the presence of one unpaired electron in the phosphane-ligated low-spin RuIII complex. Complex 2 proves to be an efficient and recyclable catalyst for the transfer hydrogenation of ketones with alcohols as hydrogen donors. Copyright
- Zhou, Chengliang,Zhang, Jing,Dakovic, Marijana,Popovic, Zora,Zhao, Xiaoli,Liu, Ye
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experimental part
p. 3435 - 3440
(2012/09/08)
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- Raney Ni-Al alloy-mediated reduction of alkylated phenols in water
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Raney Ni-Al alloy in a dilute aqueous alkaline solution has been shown to be a very powerful reducing agent in the hydrogenation of phenol and alkylated phenols to the corresponding cyclohexanol derivatives.
- Tan, Song-Liang,Liu, Guo-Bin,Gao, Xiang,Thiemann, Thies
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experimental part
p. 5 - 7
(2009/09/06)
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- Asymmetric hydrogenation of heteroaromatic ketones and cyclic and acyclic enones mediated by Cu(I)-chiral diphosphine catalysts
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Copper(I)-catalyzed asymmetric hydrogenation of heteroaromatic ketones, cyclic and acyclic enones is reported. The choice of the chiral diphosphine ligand highly influenced enantiose-lectivity as well as chemoselectivity. Highly enantioselective hydrogenation of ortho-substituted heteroaromatic ketones was achieved using BDPP as the ligand. In the 1,2-selective hydrogenation of acylic enone, SEGPHOS gave higher enantioselectivity than BDPP. On the other hand, the bulky ligand DTBM-SEGPHOS had a 1,4-selective nature, leading to the first highly 1,4-selective and enantioselective hydrogenation of cyclic enones.
- Shimizu, Hideo,Nagano, Takuto,Sayo, Noboru,Saito, Takao,Ohshima, Takashi,Mashima, Kazushi
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scheme or table
p. 3143 - 3146
(2010/03/24)
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- Hydrogen-transfer reduction of carbonyl compounds promoted by nickel nanoparticles
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Nickel(0) nanoparticles, generated from nickel(II) chloride, lithium powder and a catalytic amount of 4,4-di-tert-butylbiphenyl (DTBB) in THF at room temperature, have been found to promote the reduction of a variety of ketones and aldehydes by transfer hydrogenation using isopropanol as the hydrogen donor. The nickel nanoparticles were characterised and could be re-utilised with a good performance in the absence of a base. A mechanistic study demonstrates that the reaction proceeds through a dihydride-type mechanism.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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p. 1847 - 1852
(2008/09/18)
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Reductions of α,β-unsaturated ketones by NaBH4 or NaBH4 + CoCl2: Selectivity control by water or by aqueous micellar solutions
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Operationally simple and environmentally benign procedures have been developed to selectively reduce different α,β-unsaturated ketones, 4,4- dimethylcyclohex-2-ene-1-one (1), isophorone (2), benzylideneacetone (3), chalcone (4) by NaBH4 or by the system NaBH4 + COCl2. Alternative reaction media to the extensively used MeOH have been explored, and new procedures take advantage of the acceleration and chemoselectivity induced by water or by aqueous micellar solutions. It was possible to selectively and quantitatively afford pure products of 1,2 and of 1,4 reduction as well as the totally reduced compounds (yield and selectivity > 90%) by simple changes in the experimental conditions.
- Aramini, Andrea,Brinchi, Lucia,Germani, Raimondo,Savelli, Gianfranco
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p. 1793 - 1797
(2007/10/03)
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- Selective catalytic hydrogenation of organic compounds in supercritical fluids as a continuous process
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We report a new method for continuous hydrogenation in supercritical fluids (CO2 or propane) using heterogeneous noble metal catalysts on Deloxan aminopolysiloxane supports. The method has considerable promise both for laboratory-scale hydrogenation and for the industrial production of fine chemicals. It can be applied to a wide range of organic compounds including alkenes, alkynes, aliphatic and aromatic ketones and aldehydes, epoxides, phenols, oximes, nitrobenzenes, Schiff bases, and nitriles. Conversion of starting materials, product selectivity, and space-time yields of the catalyst are all high, and the reactors themselves are very small (5- and 10-mL volume). Supercritical hydrogenation enables the reaction parameters to be controlled very precisely. Results are presented for a series of different reactions showing product distributions, which are dependent on temperature, pressure, H2 concentration, and the loading and nature of the catalyst. The hydrogenation of cyclohexene has been studied in some detail, and our results are related to the phase diagrams of the ternary system cyclohexane + CO2 + H2, which we present in a novel way, more suited to continuous reactors. Finally, we report that the supercritical hydrogenation of isophorone has advantages over conventional methods.
- Hitzler, Martin G.
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p. 137 - 146
(2013/09/08)
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- Reaction of diisopropoxytitanium (III) tetrahydroborate with selected organic compounds containing representative functional groups
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Diisopropoxytitanium(III) tetrahydroborate, (1PrO)2TiBH4), generated in situ in dichloromethane from diisopropoxytitanium dichloride and benzyltriethylammonium borohydride in a 1:2 ratio selectively reduces aldehydes, ketones, acid chlorides, carboxylic acids, and N-Boc-protected amino acids to the corresponding alcohols in excellent yield under very mild reaction conditions (-78 to 25°C).
- Ravikumar,Chandrasekaran, Srinivasan
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p. 826 - 830
(2007/10/03)
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- Ring Opening of Cyclopropylketones Induced by Photochemical Electron Transfer
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Depending on the substitution pattern of cyclopropylketones, the photochemically induced electron transfer of tertiary amines to cyclopropylketones leads either to the formation of 3-substituted cycloalkanones or to ring expanded products.
- Cossy, Janine,Furet, Nathalie,BouzBouz, Samir
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p. 11751 - 11764
(2007/10/02)
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- A Reinvestigation of the Meerwein-Ponndorf-Verley Reduction: A Highly Efficient Variation Using Zirconium Catalysts
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A new variation of the Meerwein-Ponndorf-Verley reduction based on mechanistic considerations is presented.Under optimized conditions 1-(4-dimethylaminophenyl)ethanol was used as the reducing alcohol (2-4 equiv.), Zr(O-tBu)4 as the catalyst (0.2 equiv.), and toluene or cyclohexane as the solvent.Aldehydes and ketones (if not extremely sterically hindered) were reduced to the corresponding alcohols at room temperature mostly within 2-4 h in essentially quantitative yield. α,β-Unsaturated carbonyl compounds cleanly react in a 1,2-mode to afford the corresponding allylic alcohols. - Key Words: Reductions / Meerwein-Ponndorf-Verley reaction / Catalysis / Zirconium tetra-tert-butoxide / β-Hydride shift / Kinetics
- Knauer, Birgit,Krohn, Karsten
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p. 677 - 684
(2007/10/02)
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- Amino acid of cycloaliphatic alcohols, process for their preparation and use as drugs
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Amino acid esters of cycloaliphatic alcohols of the formula: STR1 wherein A is cyclohexyl, cyclohexenyl, cyclopentyl and cyclopentenyl, substituted with from one to three radicals which are methyl, ethyl, and/or ethenyl. These amino acid esters have hypolipemic properties.
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- SELECTIVE REDUCTION OF α,β-UNSATURATED KETONES WITH POTASSIUM TRIPHENYLBOROHYDRIDE
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Potassium triphenylborohydride is an excellent 1,4-reducing agent for acyclic enones and β-unsubstituted cyclohexenones, and shows a greater tendency for 1,4-reduction than K-Selectride for β-substituted cyclohexenones and aromatic enones.
- Kim, Kwan Eung,Park, Soo Bong,Yoon, Nung Min
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- ACTIVATION OF REDUCING AGENTS. SODIUM HYDRIDE CONTAINING COMPLEX REDUCING AGENTS 24. BENEFICIAL EFFECT OF Me3SiCl ON THE REDUCING PROPERTIES OF NiCRA
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Reduction of carbon-carbon double bonds can be achieved with either NiCRA or NiCRASi (nickel containing Complex Reducing Agent activated by Me3SiCl).Selective reduction of polyunsaturated hydrocarbons or unsaturated ketones are easily performed with both reagents.
- Fort, Y,Vanderesse, R,Caubere, P
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p. 5487 - 5490
(2007/10/02)
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- Transmission of Substituent Effects through Unsaturated Systems. Part 6. Kinetics of Reduction of β-Substituted α, β-Unsaturated Ketones with Sodium Borohydride
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The rate constants for addition of sodium borohydride to 3-substituted 5,5-dimethylcyclohex-2-enones (1), para-substituted 3-phenylcyclohexenones (2), and para-substituted acetophenones (3) have been determined in an alkaline solution (NaOH, 0.025 mol l-1) of water-dioxane (1:1 v/v) at 298 K.The conjugated cyclohexenone systems (1) and (2) undergo exclusive 1,2-reduction in these conditions to produce the corresponding allylic alcohols.The regioselectivity of reduction is discussed.The linear free energy relationships obtained between the rate constants and ?p or ?p+ confirm that these 3-substituted cyclohexenone structures are good models for the investigation of the substituent effects on the reactivity of ethylenic systems.Comparison of reaction constants for the three series leads to the conclusion that, as for borohydride reductions of acetophenone, the cyclohexenone reduction must have a late transition state in the final quarter of the reaction co-ordinate.
- Geribaldi, Serge,Decouzon, Michele,Boyer, Bernard,Moreau, Claude
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p. 1327 - 1330
(2007/10/02)
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- Zinc-Modified Cyanoborohydride as a Selective Reducing Agent
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Zinc-modified cyanoborohydride generated from sodium cyanoborohydride and zinc chloride in a 2:1 molar ratio is found to be a selective and versatile reducing agent.The reagent in diethyl ether reduces aldehydes, ketones and acid chlorides to the corresponding alcohols but does not reduce acid anhydrides, acids, esters and tertiary amides.The reagent in methanol is very useful for reduction of enamines, reductive amination of aldehydes and ketones, reductive methylation of amines, and deoxygenation of aldehydes and ketones.
- Kim, Sunggak,Oh, Chang Ho,Ko, Jae Suk,Ahn, Kyo Han,Kim, Yong Jin
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p. 1927 - 1932
(2014/12/12)
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- Ate Complex from Diisobutylaluminum Hydride and n-Butyllithium as a Powerful and Selective Reducing Agent for the Reduction of Selected Organic Compounds Containing Various Functional Groups
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The "ate" complex generated from diisobutylaluminum hydride and n-butyllithium in an equimolar ratio either in tetrahydrofuran-hexane or in toluene-hexane was reacted with a series of selected organic compounds containing various functional groups in order to explore the reducing properties and to determine the synthetic utility of the reagent.The reagent is very effective for selective 1,2-reduction of both acyclic and cyclic enones.The reagent in tetrahydrofuran-hexane gives slightly better 1,2-selectivity than in toluene-hexane in the reduction of some acyclic enones, whereas the reagent in toluene-hexane gives better 1,2-selectivity in the reduction of conjugated cyclohexenones.Esters and lactones are completely reduced to the corresponding alcohols at room temperature, whereas they are reduced to the corresponding alcohols and aldehydes at -78 deg C even with an excess amount of the reagent.Partial reduction of the esters and the lactones to the corresponding aldehydes has not been observed.Acid chlorides are rapidly reduced to the corresponding alcohols with an excess amount of the reagent at -78 deg C, whereas they are reduced to a mixture of the alcohol, the aldehyde, and the unreacted acid chloride with a stoichiometric amount of the reagent at -78 deg C.Acid anhydrides are rapidly and quantitatively reduced to an equimolar mixture of the acid and the alcohol at -78 deg C.Carboxylic acids and primary and secondary amides are inert to the reagent at room temperature and are recovered unchanged..Tertiary amides are cleanly reduced to the aldehydes with a stoichiometric amount of the reagent either at 0 deg C or at room temperature, whereas they are inert to the reagent at -78 deg C, which permits the selective reduction of other reducible functional groups in the presence of the tertiary amide group at the latter temperature.The reagent rapidly reduces simple primary alkyl, benzyl, and allyl bromides but slowly primary alkyl chlorides and secondary alkyl bromides.Tertiary alkyl and aryl halides are essentially inert to the reagent, whereas trityl bromide and vinyl bromide are reduced at a reasonable rate.Epoxides are cleanly reduced to the corresponding alcohols.The opening of the epoxide ring with this reagent proceeds with excellent isomeric purity, yielding the more highly substituted alcohol almost exclusively.Nitriles are resistant to reduction and are only slowly converted to the corresponding aldehydes at room temperature.Disulfides are rapidly and quantitatively reduced to the corresponding thiols.Sulfoxides and sulfones are inert to the reagent and are recovered unchanged.Selective reductions of an ester in the presence of other reducible groups such as a bromide, a tertiary amide, and a nitrile are achieved with the reagent at -78 deg C by using a modified procedure.Furthermore, the reagent is capable of reducing selectively a ketone in the presence of an ester.
- Kim, Sunggak,Ahn, Kyo Han
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p. 1717 - 1724
(2007/10/02)
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- Aminoborohydrides as Reducing Agents. 1. Sodium (Dimethylamino)- and (tert-Butylamino)borohydrides as Selective Reducing Agents
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Replacement of a hydride in borohydride by an electron-donating alkylamino group greatly enhances the reducing ability of the resulting reagents.Thus, sodium (dimethylamino)- and (tert-butylamino)borohydrides (1, NaDMAB, and 2, NaTBAB, respectively) not only reduce aldehydes and ketones to alcohols but also are effective for the conversion of esters to alcohols and primary amides to amines in good to excellent yields.Tertiary amides are reduced to alcohols (i.e., N,N-dimethylamides) or amines (i.e.N,N-diisopropylamides) depending on the steric bulk of the alkyl substituents on nitrogen.However, secondary amides are not reduced by the reagents allowing selective conversion of primary and tertiary amides in the presence of secondary amides.Nitriles are attacked by the reagents but do not afford synthetically useful amounts of amine products.Aryl halides are slowly converted to arenes, but alkyl halides and epoxides undergo unusual reactions with the amino portion of the reagents.
- Hutchins, Robert O.,Learn, Keith,El-Telbany, Farag,Stercho, Yuriy P.
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p. 2438 - 2443
(2007/10/02)
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- MECHANISM OF THE γ-RADIOLYSIS OF 2-PROPANOL SOLUTIONS OF CYCLOHEXANONES
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The γ-radiolysis of 2-propanol solutions of cyclohexanone gives mainly hydrogen, acetone, pinacol, methane derived from 2-propanol, and cyclohexanol, 2-(2-cyclohexanonyl)-cyclohexanone, and 3-(2-hydroxy-2-propyl)cyclohexanone derived from cyclohexanone.The radiolytic yields of all these products were highly dependent on the initial cyclohexanone concentration.The formation of cyclic alcohols by radioreduction has been extended to various substituted cyclohexanones.Radiolytically generated solvated electrons are scavenged by cyclohexanone, leading to the corresponding radical anions.The protonation of these radical anions gives rise to cyclohexanol via the dismutation of the hydroxycyclohexyl radicals.Steady state radiolysis measurements were complemented by pulse radiolysis in dilute solution.It was established that radical-anions and hydroxylated radicals decayed according to a second order rate law.When ketone concentration was lower than 0.1M, radiolytic yields were in agreement with the mechanism mentioned above.However, in concentrated media the large increase in G(cyclohexanol) cannot be only accounted for by the involvement of radiolytically generated solvated electrons; probably it is due to an electron transfer from the cyclohexanone enolate to cyclohexanone itself, thus generating extra amounts of cyclohexanone radical anions.
- Alipour, E.,Vidril, D.,Micheau, J. C.,Paillous, N.,Lattes, A.,et al.
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p. 2807 - 2814
(2007/10/02)
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- ORGANOMETALLIC CHEMISTRY UNDER HIGH PRESSURE: TRIALKYLTIN HYDRIDE ADDITION TO UNSATURATED SYSTEMS
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The influence of high pressure (10-14 kbars) on the reaction of tin hydrides with alkenes and ketones has been investigated and a marked increase of yields generally was observed.For cyclopropyl- and cyclobutyl-alkenes, adducts were formed with retention of the rings.The stereochemical outcomes of the reaction were modified.
- Rahm, A.,Castaing-Degueil, M.,Pereyre, M.
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p. C29 - C32
(2007/10/02)
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- Polycyclic phenols, alcohols and ketones from phenols, cyclic alcohols and cyclic ketones using a nickel oxide/manganese oxide/magnesium oxide catalyst in presence of at least one of hydrogen and nitrogen
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At least one of a polycyclic phenol, a polycyclic alcohol and a polycyclic ketone is produced under hydrogenation conditions using a nickel oxide/manganese oxide/magnesium oxide catalyst by subjecting at least one of a monocyclic ketone, a monocyclic alcohol and a monocyclic phenol to said conditions and said catalyst.
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- SELECTIVITY IN THE ACID CATALYSED REDUCTION OF CARBONYL COMPOUNDS TO ALCOHOLS BY BIS(TRIPHENYLPHOSPHINE)COPPER(I) TETRAHYDROBORATE: REDUCTION OF ALDEHYDES IN THE PRESENCE OF KETONES
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Bis(triphenylphosphine)copper(I) tetrahydroborate reduces carbonyl compounds to alcohols in the presence of acid catalysts in excellent yields with high stereoselectivity; α,β-unsaturated aldehydes are reduced regioselectively.In a mixture of an aldehyde and a ketone, an aldehyde may be reduced preferentially.
- Fleet, G.W.J.,Harding, P.J.C.
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p. 675 - 678
(2007/10/02)
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- THE INFLUENCE OF LITHIUM COMPLEXING AGENTS ON THE REGIOSELECTIVITY OF REDUCTIONS OF SUBSTITUTED 2-CYCLOHEXENONES BY LiAlH4 and LiBH4
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A reversal of regioselectivity of LiAlH4 or LiBH4 reduction of 2-cyclohexenone induced by addition of -cryptand to the reaction medium is accompanied by a rate decrease.In the absence of the cryptand, carbonyl attack predominates (C1:C3=86:14 with LiAlH4 in THF).In the presence of the cryptand, double bond attack is favoured (C1:C3=14:86).This effect is larger with LiAlH4 than with LiBH4.This trend is general in the case of five substituted 2-cyclohexenones.Using 12-crown-4 as a Li+ coordinator, a change in regioselectivity occurs but it is less pronunced than with the cryptand.
- Loupy, Andre,Seyden-Penne, Jacqueline
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p. 1937 - 1942
(2007/10/02)
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