- Synthetic studies of kinamycin antibiotics: Stereoselective synthesis of the highly oxygenated D-ring and construction of the ABD-ring system of kinamycins
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A concise and stereoselective synthesis of the highly oxygenated D-ring of the kinamycin family of antitumor antibiotics was achieved from commercially available 3-methyl-2-cyclohexen-1-one. The key steps included a regioselective isomerization of a cis-epoxy alcohol, a regioselective reductive ring opening of a benzylidene ketal, and a stereoselective α-hydroxy-directed ketone reduction. The Ullmann coupling between a bromonaphthaldehyde AB-ring fragment and an α-iodocyclohexenone, which is a versatile D-ring precursor, effected the construction of the functionalized ABD-ring system that may provide access to kinamycin F and its structural analogues. A concise and stereoselective synthesis of the highly oxygenated D-ring of the kinamycins was achieved from commercially available 3-methyl-2-cyclohexenone. Also, a metal-catalyzed coupling reaction between an AB-ring fragment and a D-ring precursor enabled the construction of the functionalized ABD-ring system that may provide entry to synthesis of the kinamycins.
- Ouzouni, Maria-Dimitra,Fokas, Demosthenes
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Read Online
- Ruthenium-p-cymene Complex Side-Wall Covalently Bonded to Carbon Nanotubes as Efficient Hybrid Transfer Hydrogenation Catalyst
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A half-sandwich ruthenium-p-cymene organometallic complex has been immobilized at Single Walled Carbon Nanotubes (SWNT) sidewalls through a stepwise covalent chemistry protocol. The introduction of amino groups by means of diazonium-chemistry protocols leads the grafting at the outer walls of the nanotubes. This hybrid material is active in the transfer hydrogenation of ketones to yield alcohols, using as hydrogen source 2-propanol. SWNT?NH2?Ru presents a broad scope, performing the reaction under aerobic conditions and can be recycled over 9 consecutive reaction runs without losing activity or leaching ruthenium out. Comparison of the activity with related homogeneous catalysts reveals an improved performance due to the covalent bond between the metal and the material, achieving turnover frequencies as high as 192774 h?1.
- Blanco, Matías,Cembellín, Sara,Agnoli, Stefano,Alemán, José
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p. 5156 - 5165
(2021/11/05)
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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- Borinic Acid Mediated Hydrosilylations: Reductions of Carbonyl Derivatives
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4-Fluoro-2-chlorophenylborinic acid acts as a precatalyst in the presence of phenylsilane for the facile reduction of ketones, aldehydes and imines. Notably, synergistic mediation of a tertiary amine was found essential to trigger silicon to boron hydride transfer to generate a key amine–diarylhydroborane Lewis complex.
- Chardon, Aurélien,Rouden, Jacques,Blanchet, Jér?me
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supporting information
p. 995 - 998
(2018/12/13)
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- Straightforward chemo- and stereoselective fluorocyclopropanation of allylic alcohols: Exploiting the electrophilic nature of the not so elusive fluoroiodomethyllithium
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An unprecedented direct fluorocyclopropanation of allylic alcohols is reported. This simple method involves the not so elusive fluoroiodomethyllithium, a carbenoidic intermediate that under the developed conditions discloses its electrophilic nature. Gratifyingly, the reaction turned out to be highly chemo- and stereoselective, and DFT calculations provided insights into the structure and nature of this new type of carbenoid.
- Colella, Marco,Tota, Arianna,Gro?johann, Angela,Carlucci, Claudia,Aramini, Andrea,Sheikh, Nadeem S.,Degennaro, Leonardo,Luisi, Renzo
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supporting information
p. 8430 - 8433
(2019/07/22)
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- Polymer-anchored mononuclear and binuclear CuII Schiff-base complexes: Impact of heterogenization on liquid phase catalytic oxidation of a series of alkenes
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Liquid phase catalytic oxidation of a number of alkenes, for example, cyclohexene, cis-cyclooctene, styrene, 1-methyl cyclohexene and 1-hexene, was performed using polymer-anchored copper (II) complexes PS-[Cu (sal-sch)Cl] (5), PS-[Cu (sal-tch)Cl] (6), PS-[CH2{Cu (sal-sch)Cl}2] (7) and PS-[CH2{Cu (sal-tch)Cl}2] (8). Neat complexes [Cu (sal-sch)Cl] (1), [Cu (sal-tch)Cl] (2), [CH2{Cu (sal-sch)Cl}2] (3) and [CH2{Cu (sal-tch)Cl}2] (4) were isolated by reacting CuCl2·2H2O with [Hsal-sch] (I), [Hsal-tch] (II), [H2bissal-sch] (III) and [H2bissal-tch] (IV), respectively, in refluxing methanol. Complexes 1–4 have been covalently anchored in Merrifield resin through the amine nitrogen of the semicarbazide or thiosemicarbazide moiety. A number of analytical, spectroscopic and thermal techniques, such as CHNS analysis, Fourier transform-infrared, UV–Vis, PMR, 13C-NMR, electron paramagnetic resonance, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, atomic force microscopy, atomic absorption spectroscopy, and electrospray ionization-mass spectrometry, were used to analyze and establish the molecular structure of the ligands (I)–(IV) and complexes (1)–(8) in solid state as well as in solution state. Grafted complexes 5–8 were employed as active catalysts for the oxidation of a series of alkenes in the presence of hydrogen peroxide. Copper hydroperoxo species ([CuIII (sal-sch)-O-O-H]), which is believed to be the active intermediate, generated during the catalytic oxidation of alkenes, are identified. It was found that supported catalysts are very economical, green and efficient in contrast to their neat complexes as well as most of the recently reported heterogeneous catalysts.
- Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Mishra, Vivek Kumar,Chaudhary, Nikita,Haldar, Chanchal
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- Aerobic oxidation of the C-H bond under ambient conditions using highly dispersed Co over highly porous N-doped carbon
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Highly dispersed Co sites in highly porous N-doped carbon (Co-NC) were synthesized by high-temperature pyrolysis of Zn/Co bimetallic zeolitic imidazolate framework-8 (CoxZn100-x-ZIF). Wide characterization indicated that the pyrolysis atmosphere and temperature play crucial roles in the metal dispersion and pore structure of the resulting materials. A hydrogen treatment at elevated temperatures is found to favour the Zn volatilization and restrict the pore shrinkage of the ZIF precursor, thus yielding efficient catalysts with highly dispersed Co, a high surface area (1090 m2 g-1) and pore volume (0.89 cm3 g-1). When used as a catalyst for aerobic oxidation of ethylbenzene (EB), Co1Zn99-ZIF-800-H2 contributes to 98.9% EB conversion and 93.1% ketone selectivity under mild conditions (60 °C, 1 atm O2), which is 41.3 times more active in comparison to the ZIF-67-derived Co catalyst. Co-NC is stable and could be reused four times without obvious deactivation. This catalyst displays good chemoselectivity to the corresponding ketones when using a broad scope of hydrocarbon compounds.
- Nie, Renfeng,Chen, Jingwen,Chen, Minda,Qi, Zhiyuan,Goh, Tian-Wei,Ma, Tao,Zhou, Lin,Pei, Yuchen,Huang, Wenyu
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p. 1461 - 1466
(2019/03/26)
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- Domino Aryne Annulation via a Nucleophilic-Ene Process
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1,2-Benzdiyne equivalents possess the unique property that they can react with two arynophiles through iteratively generated 1,2- and 2,3-aryne intermediates. Upon rational modification on the second leaving group of these aryne precursors, a domino aryne annulation approach was developed through a nucleophilic-ene reaction sequence. Various benzo-fused N-heterocyclic frameworks were achievable under transition metal-free conditions with a broad substrate scope.
- Xu, Hai,He, Jia,Shi, Jiarong,Tan, Liang,Qiu, Dachuan,Luo, Xiaohua,Li, Yang
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supporting information
p. 3555 - 3559
(2018/03/21)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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supporting information
p. 3677 - 3686
(2018/06/04)
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- Maghemite decorated with ultra-small palladium nanoparticles (γ-Fe2O3-Pd): Applications in the Heck-Mizoroki olefination, Suzuki reaction and allylic oxidation of alkenes
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A nanocatalyst comprising ultra-small Pd/PdO nanoparticles (57Fe M?ssbauer spectroscopy. The cost-effective catalyst could be easily separated from the reaction mixture by using an external magnet and reused four times without any loss of activity; chemical stability and recyclability aspects of the catalyst were investigated.
- Rathi, Anuj K.,Gawande, Manoj B.,Pechousek, Jiri,Tucek, Jiri,Aparicio, Claudia,Petr, Martin,Tomanec, Ondrej,Krikavova, Radka,Travnicek, Zdenek,Varma, Rajender S.,Zboril, Radek
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p. 2363 - 2373
(2016/05/19)
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- Eco-friendly stereoselective reduction of α,β-unsaturated carbonyl compounds by Er(OTf)3/NaBH4 in 2-MeTHF
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An operationally simple and environmentally benign catalytic procedure has been developed to selectively reduce different α,β-unsaturated ketones. The corresponding allylic alcohols are obtained with high chemo- and diastereoselectivity using Er(OTf)3 and NaBH4 in 2-MeTHF. This protocol reduces the amount of catalyst and NaBH4 needed, compared to classical procedures and the stages of extraction/purification are carried out in aqueous solutions avoiding the use of toxic solvents. Taking into account that Er(OTf)3 can be considered even less toxic than table salt and the 'greenness' of 2-MeTHF as a solvent, the system Er(OTf)3/2-MeTHF can be proposed as a cheap, efficient, and environmentally sustainable reduction system for the synthesis of allylic alcohols.
- Nardi, Monica,Sindona, Giovanni,Costanzo, Paola,Oliverio, Manuela,Procopio, Antonio
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p. 1132 - 1135
(2015/02/19)
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- Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
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The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
- Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
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p. 3336 - 3341
(2015/06/16)
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- COMPLEMENT PATHWAY MODULATORS AND USES THEREOF
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The present invention provides a compound of formula I: a method for manufacturing the compounds of the invention, and its therapeutic uses. The present invention further provides a combination of pharmacologically active agents and a pharmaceutical composition.
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(2014/01/17)
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- TRIAZOLYL DERIVATIVES AS SYK INHIBITORS
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Provided are triazole derivatives of Formula I which are potent inhibitors of spleen tyrosine kinase and pharmaceutical composition. The triazole derivatives are useful in the treatment and prevention of diseases mediated by said enzyme, such as asthma, COPD, rheumatoid arthritis, and cancer.
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Page/Page column 104
(2014/04/17)
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- Electrochemical intramolecular aminooxygenation of unactivated alkenes
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An electrochemical approach to the intramolecular aminooxygenation of unactivated alkenes has been developed. This process is based on the addition of nitrogen-centered radicals, generated through electrochemical oxidation, to alkenes followed by trapping of the cyclized radical intermediate with 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO). Difunctionalization of a variety of alkenes with easily available carbamates/amides and TEMPO affords aminooxygenation products in high yields and with excellent trans selectivity for cyclic systems (d.r. up to>20:1). The approach provides a much-needed complementary route to existing cis-selective methods.
- Xu, Fan,Zhu, Lin,Zhu, Shaobin,Yan, Xiaomei,Xu, Hai-Chao
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supporting information
p. 12740 - 12744
(2015/03/30)
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- New heterogeneous B(OEt)3-MCM-41 catalyst for preparation of α,β-unsaturated alcohols
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Grafting of boron tri-ethoxide on mesoporous MCM-41 resulted in a highly active catalyst for the Meerwein-Ponndorf-Verley (MPV) reduction and the catalyst denoted as B(OEt)3-MCM-41. Chemoselective reduction of α,β-unsaturated aldehydes and ketones to the corresponding α,β-unsaturated alcohols was achieved by MPV reduction reaction using a new B(OEt)3-MCM-41 catalyst. The prepared new heterogeneous catalyst, B(OEt)3-MCM-41, was characterized in detail by using XRD, 29Si NMR-, 11B NMR-, 13C NMR-, and TEM, N2 adsorption, and ICP-OES. The results demonstrated the successful homogenous distribution of the B(OEt)3 on the MCM-41 support. The heterogeneous B(OEt)3-MCM-41 catalyst, in comparison with the homogeneous B(O i Pr)3 and B(OEt)3 catalysts, displayed similiar catalytic activity in the MPV reduction of α,β-unsaturated aldehydes and ketones with alcohols as reductants. Reduced reaction times and very high selectivities for the unsaturated alcohols were obtained with the heterogenous catalyst compared with the homogeneous catalysts. The B(OEt)3-MCM-41 catalyst was found to be encouraging, as is is recyclable up to six cycles without any significant loss in its catalytic activity.
- Uysal, Burcu,Oksal, Birsen S.
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p. 3893 - 3911
(2015/06/08)
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- Scope and mechanistic studies of catalytic hydrosilylation with a high-valent nitridoruthenium(VI)
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Hydrosilylation catalyzed by a high-valent nitridoruthenium(VI) compound, [RuN(saldach)(CH3OH)]+[ClO4]- (1, where saldach is the dianion of racemic N,N'-cyclohexan-diyl- bis(salicylideneimine)) is described. Using phenylsilane as reductant, a variety of unsaturated organic substrates, including aldehydes, ketones, and imines, are effectively reduced to alcohols and amines, respectively, accompanied by the redistribution of PhSiH3 at silicon. Mechanistic studies indicate that the catalysis proceeds via silane activation rather than carbonyl activation, and the silane is likely activated via multiple pathways, including a radical-based pathway.
- Abbina, Srinivas,Bian, Shi,Oian, Casey,Du, Guodong
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supporting information
p. 678 - 684
(2013/05/21)
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- Iron(III) chloride-benzotriazole adducts with trigonal bipyramidal geometry: Spectroscopic, structural and catalytic studies
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The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl 3(Mebta)2] (2), [FeCl3(5,6Me 2btaH)2] (3) and [FeCl3(5ClbtaH) 2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1-4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mo?ssbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the "green" H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail.
- Anastasiadis, Nikolaos C.,Bilis, George,Plakatouras, John C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Beavers, Christine,Teat, Simon J.,Louloudi, Maria,Perlepes, Spyros P.
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p. 189 - 202
(2013/10/08)
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- Studies toward the generation of functionalized quaternary carbon centers relying on wittig and wittig-still allylic ether anionic transpositions
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Although the [2,3]-Wittig and Wittig-Still rearrangements have long been known, their application in the generation of quaternary carbon centers in carbocyclic ring systems is sparse. Model studies utilizing this strategy and possible mechanisms are discussed herein. Unprecedented examples of an α-elimination pathway from stannylmethyl allyl ethers as a major undesired product in some Wittig-Still rearrangements are reported.
- Hanessian, Stephen,Dorich, Stephane,Chattopadhyay, Amit Kumar,Bueschleb, Martin
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p. 8915 - 8921
(2013/09/24)
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- Covalent attachment of a biomimetic Ru-(terpy)(bpy) complex on silica surface: Catalytic potential
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The Ru-containing modified silica [RuII(terpy)(4′Mebpy/ 4CONH(CH2)3SiO3/2)Cl]+ m·zSiO2 has been prepared by covalent attachment on silica surface of biomimetic [RuII(terpy)(4-CO2H- 4′-Mebpy)Cl]+ complex through the formation of a pseudo-peptide bond. The catalytic ability of bio-derived silica for alkene oxidation with HOOtBu has been evaluated exhibiting significant efficiency and, in some cases, showing increased activity compared vs. the corresponding 'net' [RuII(terpy)(4-CO2H-4′-Mebpy)Cl]+ complex. The data supported that the covalently attached ruthenium complex preserves the catalytic behaviour of the 'net' ruthenium complex indicating that the presented grafting process was successful.
- Papafotiou,Karidi,Garoufis,Louloudi
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p. 634 - 638
(2013/08/14)
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- Lithium amidoborane, a highly chemoselective reagent for the reduction of α,β-unsaturated ketones to allylic alcohols
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Lithium amidoborane (LiNH2BH3, LiAB for short), is capable of chemoselectively reducing α,β-unsaturated ketones to the corresponding allylic alcohols at ambient temperature. A mechanistic study shows that the reduction is via a double hydrogen transfer process. The protic H(N) and hydridic H(B) in amidoborane add to the O and C sites of the carbonyl group, respectively.
- Xu, Weiliang,Zhou, Yonggui,Wang, Ruimin,Wu, Guotao,Chen, Ping
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experimental part
p. 367 - 371
(2012/01/13)
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- Lanthanide replacement in organic synthesis: Luche-type reduction of α,β-unsaturated ketones in the presence of calcium triflate
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Development of a calcium-mediated regioselective 1,2-reduction of challenging α,β-unsaturated ketones, such as 2-cyclopententone, is reported. The corresponding allylic alcohols are obtained in very good regioselectivities using Ca(OTf)2 and NaBH4. Furthermore, we have shown that our method can stereoselectively reduce aziridinyl ketones.
- Forkel, Nina V.,Henderson, David A.,Fuchter, Matthew J.
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supporting information; experimental part
p. 2129 - 2132
(2012/09/08)
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- Comparison of heterogeneous B(OiPr)3-MCM-41 and homogeneous B(OiPr)3, B(OEt)3 catalysts for chemoselective MPV reductions of unsaturated aldehydes and ketones
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Boron tri-isopropoxide, B(OiPr)3, was immobilized on mesoporous material, MCM-41, and denoted as "B(OiPr) 3-MCM-41". The prepared new heterogeneous catalyst, B(O iPr)3-MCM-41, was characterized in details by using PXRD, FT-IR-, 11B NMR-, 29Si NMR-, 13C NMR-, TEM, EDX, N2 adsorption and ICP-OES. The results demonstrated the successful homogenous distribution of the B(OiPr)3 on the MCM-41 support. Heterogeneous B(OiPr)3-MCM-41 catalyst in comparison with the homogeneous B(OiPr)3 and B(OEt) 3 catalysts, display similiar catalytic activity in the Meerwein-Ponndorf-Verley (MPV) reduction of unsaturated aldehydes and ketones with alcohols as reductants. Reduced reaction times, higher rate constants and very high selectivities for the unsaturated alcohols were obtained with the heterogenous catalyst than the homogeneous catalysts. In most cases, there were no side products other than the desired alcohol. The B(OiPr) 3-MCM-41 catalyst was found to be encouraging as the catalyst is recyclable up to six cycles without any significant loss in its catalytic activity. This work enriches the family of heterogeneous MPV catalysts for chemoselective reductions of unsaturated aldehydes and ketones.
- Uysal, Burcu,Oksal, Birsen S.
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experimental part
p. 204 - 216
(2012/10/18)
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- Domino reactions consisting of heterocyclization and 1,2-migration-redox- neutral and oxidative transition-metal catalysis
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Two cats, two paths: Two novel domino reactions starting from 6-hydroxy-2-alkyl-2-alkynylcyclohexanones have been discovered. While redox-neutral platinum catalysis gives rise to furans through a sequence of cyclization, 1,2-shift, and Grob fragmentation, oxidative copper catalysis provides an entry to bicyclic 2,3-dihydrofurans. Upon cyclization and oxidation, an unusual benzilic acid rearrangement can take place in this case. Copyright
- Umland, Klaus-Daniel,Palisse, Adeline,Haug, Timm T.,Kirsch, Stefan F.
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supporting information; experimental part
p. 9965 - 9968
(2011/11/29)
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- Metal-free, aerobic dioxygenation of alkenes using hydroxamic acids
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(Chemical equation presented) One dioxygenation please, hold the metal: In the presence of either oxygen or air as the sole oxidant and external oxygen atom source, a variety of unsaturated hydroxamic acids afford cyclic hydroxamates that are readily converted into 1,2-diols, with the potential for high levels of reaction stereocontrol.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; scheme or table
p. 4491 - 4494
(2010/08/21)
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- Tetrathiomolybdate mediated rearrangement of aziridinemethanol tosylates: A thia-aza-payne rearrangement
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Aziridinemethanol sulfonate esters react with tetrathiomolybdate 1 to give thiirane derivatives as the major product and cyclic disulfides as minor product under mild reaction conditions via an unprecedented thia-aza-Payne-type rearrangement. Interestingly, when the reaction of 1 was carried out with 2-aziridino-cyclohexanol derivatives it resulted in the formation of thia-bicyclo[3.1.1]heptane or dithia-bicyclo[3.2.1]octane derivatives.
- Sureshkumar, Devarajulu,Koutha, Srinivasamurthy,Ganesh, Venkataraman,Chandrasekaran, Srinivasan
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scheme or table
p. 5533 - 5541
(2010/11/04)
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- Hydrocarbon oxidation by homogeneous and heterogeneous non-heme iron (III) catalysts with H2O2
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Homogeneous (LFeIII) and heterogeneous (LFe III·SiO2) [L = 3-{2-[2-(3-hydroxy-1,3-diphenyl- allylideneamino)-ethylamino]-ethylimino}-1,3-diphenyl-propen-1-ol] catalysts have been synthesized and evaluated catalytically. In CH3CN, both the homogeneous and heterogeneous catalysts were efficient in alkene oxidations. Cyclohexane oxidation provides total yield of 12.1% and 7.3% with an alcohol/ketone (A/K) ratio of 1.75 and 1.60 by the LFeIII and the LFeIII·SiO2 catalysts respectively. UV-vis kinetic data suggest formation of LFeIII-OOH species. EPR data show that in the presence of CH3CN, low-spin FeIII (S = 1/2) centers are formed, which are responsible for the catalytic activity. The heterogeneous LFe·SiO2 catalyst, tested up to 5 re-uses, shows a total yield loss ~4% per use, providing the same distribution of oxidation products.
- Bilis,Christoforidis,Deligiannakis,Louloudi
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scheme or table
p. 101 - 106
(2011/01/12)
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- Photoinduced isomerization of allyl alcohols to carbonyl compounds using dendrimer disulfide as catalyst
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Allyl alcohols were isomerized to car- bonyl compounds using diphenyl disulfide derivatives upon photoirradiation. Especially, dendrimer disulfide catalyzed the isomerization of allyl alcohols. Photoinduced isomerization in water was also succeeded by the use of water-soluble dendrimer disulfide.
- Tsuboi, Takaaki,Takaguchi, Yutaka,Tsuboi, Sadao
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experimental part
p. 1 - 11
(2009/05/31)
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- Asymmetric Catalytic Hydrogenation of Prochiral Ketones and Aldehydes
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Process for stereoselective hydrogenation by reacting racemic aldehydes or ketones having a stereogenic carbon atom in the position relative to the C(O) group and containing the structural element —(O)C—C—CH— by means of hydrogen in the presence of a base and a ruthenium complex containing a bidentate ligand having coordinating P and N atoms, a monophosphine ligand and anionic and/or uncharged ligands as homogeneous catalyst, with the charge being balanced by one or two monovalent acid anions or a divalent acid anion when uncharged ligands are present.
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(2009/05/29)
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- SUBSTITUTED FLUOROETHYL UREAS AS ALPHA 2 ADRENERGIC AGENTS
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Therapeutic compounds, and methods, compositions, and medicaments related thereto are disclosed herein.
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(2008/12/04)
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- Stereoselective aziridination of cyclic allylic alcohols using chloramine-T
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The stereoselective aziridination of a range of cyclic allylic alcohols using two different chloramine salts (4-MeC6H4SO 2NClNa, TsNClNa and t-BuSO2NClNa, BusNClNa) has been explored. The stereoselectivity of these reactions was highly dependent on the structure of the allylic alcohol and the chloramine salt. Generally, mixtures of cis- and trans-hydroxy aziridines were obtained, in which the major diastereomer was the cis-hydroxy aziridine, whilst complete cis- diastereoselectivity was observed in the aziridination of 1,3-disubstituted allylic alcohols. In each case studied, aziridination using BusNClNa gave higher cis-stereoselectivity than that observed for the same reaction using TsNClNa. Unexpectedly, application of the aziridination conditions to 1-substituted cyclopen-2-en-1-ols did not generate the aziridines. Instead, epoxy sulfonamides were obtained.
- Coote, Susannah C.,O'Brien, Peter,Whitwood, Adrian C.
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supporting information; experimental part
p. 4299 - 4314
(2009/02/07)
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- Diastereoselective, three-component cascade synthesis of tetrahydrofurans and tetrahydropyrans employing the tandem Mukaiyama aldol-lactonization process
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(Chemical Equation Presented) A full account of studies leading to the development of a cascade sequence that generates as many as two C-C bonds, one C-O bond, and three new stereocenters providing substituted tetrahydrofurans (THFs) from simple γ-ketoaldehydes and thiopyridyl ketene acetals is described. The process involves a tandem Mukaiyama aldol-lactonization (TMAL) and accumulated evidence suggests the intermediacy of a silylated β-lactone that is intercepted by the pendant ketone. Formation of a cyclic oxocarbenium is followed by reduction with silicon-based nucleophiles leading to a highly diastereoselective synthesis of tetrahydrofurans. This cascade process has now been extended to the synthesis of tetrahydropyrans from simple δ-ketoaldehydes. The stereochemical outcome of the cascade processes described was determined by NOE correlations, coupling constant analysis, and X-ray crystallography of the derived oxygen heterocycles and is in accord with established and recently proposed models for nucleophilic additions to cyclic 5- and 6-membered oxocarbenium ions. The utility of this process was demonstrated by the synthesis of the tetrahydrofuran fragment of colopsinol B.
- Mitchell, T. Andrew,Zhao, Cunxiang,Romo, Daniel
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supporting information; experimental part
p. 9544 - 9551
(2009/04/07)
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- Reduction of α,β-unsaturated ketones with diphenylsilanes bearing several substituents on their phenyl moiety catalyzed by rhodium-phosphine complexes
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1,4-Addition product was afforded exclusively by rhodiumphosphine complex-catalyzed hydrosilylation by using 2-cyclohexen-1-one and a dihydrosilane bearing an ether substituent in spite of the fact that dihydrosilanes were believed to give 1,2-addition product selectively. Copyright
- Imao, Daisuke,Hayama, Miyuki,Ishikawa, Kohta,Ohta, Tetsuo,Ito, Yoshihiko
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p. 366 - 367
(2007/10/03)
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- Rhodium(I) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks
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Novel rhodium(i) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks were synthesized and the complexes were used as catalysts in rhodium-catalyzed hydrosilylation of α,β-unsaturated ketones to show high 1,4-adduct selectivity. The Royal Society of Chemistry.
- Sato, Hiromichi,Fujihara, Tetsuaki,Obora, Yasushi,Tokunaga, Makoto,Kiyosu, Junya,Tsuji, Yasushi
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p. 269 - 271
(2007/10/03)
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- Chemoselective hydrogenation of α,β-unsaturated ketones to allylic alcohols, catalyzed by a mononuclear ruthenium complex containing trans PnBu3 and PPh3 ligands
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The ruthenium(II) bis(acetate) complex Ru(CO)2(OAc)2(PnBu3) (PPh3) (OAc = acetate) containing two different trans phosphine ligands, has been employed as pre-catalyst for the chemoselective hydrogenation of α,β-unsaturated ketones to allylic alcohols. Analogous catalytic reactions with the homodiphosphine pre-catalysts Ru(CO)2(OAc)2(PnBu3) 2 and Ru(CO)2(OAc)2(PPh3)2 gave lower conversions and selectivities. Batch catalytic reactions and operando high-pressure NMR experiments have contributed to establish that the hydrogenation of the C{double bond, long}O group is performed by the heterodiphosphine monohydride RuH(CO)2(OAc)(PnBu3)(PPh3) generated in situ by hydrogenation of the bis(OAc) precursor. PPh3 unfastening from this monohydride complex is an essential condition for the occurrence of catalytic activity.
- Micoli, Francesca,Oberhauser, Werner,Salvini, Antonella,Bianchini, Claudio
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p. 2334 - 2341
(2008/01/27)
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- Chemoselective reduction of aldehydes in the presence of ketones with NaBH4 in polyethylene glycol dimethyl ethers
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Aldehydes and ketones were treated with NaBH4 in polyethylene glycol dimethyl ethers (PEGDME) to give the corresponding alcohols in good yields. Chemoselective reduction of aldehydes in the presence of ketones was described.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Nishida, Yoko,Satsumabayashi, Koko,Horaguchi, Takaaki
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p. 867 - 872
(2007/10/03)
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- Reductive alkylation of β-alkoxy aziridines: New route to substituted allylic amines
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(Chemical Equation Presented) A new route to substituted cyclic allylic amines via the reductive alkylation of β-alkoxy aziridines using excess alkyllithium reagents is described.
- Rosser, Clare M.,Coole, Susannah C.,Kirby, Jonathan P.,O'Brien, Peter,Caine, Darren
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p. 4817 - 4819
(2007/10/03)
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- Chemoselective Hydrogen Transfer Reduction of Unsaturated Ketones to Allylic Alcohols with Solid Zr and Hf Catalysts
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α,β-Unsaturated ketones were reduced to allylic alcohols with high chemo- and diastereoselectivity, using Zr and Hf compounds heterogenised on mesoporous molecular sieves.
- De Bruyn, Mario,De Vos, Dirk E.,Jacobs, Pierre A.
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p. 1120 - 1125
(2007/10/03)
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- Chemo-enzymatic preparation of optically active endo- bicyclo[4.1.0]heptan-2-ols
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Resolutions of endo-bicyclo[4.1.O]heptan-2-ols were achieved by acylation in the presence of lipase from Candida antarctica (Novozym). The (1S,2R,6R) enantiomers reacted faster and the enantiomeric ratios were between 60 and 800 for the 6-substituted bicycloalkanols.
- Barnier, Jean-Pierre,Morisson, Veronique,Volle, Isabelle,Blanco, Luis
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p. 1107 - 1117
(2007/10/03)
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- Regioselective reduction of epoxides and conjugated carbonyl compounds using zeolite supported zinc borohydride
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Zeolite supported zinc borohydride is a versatile catalyst for the regeoselective reduction of epoxides, conjugated ketones, and aldehydes to the corresponding alcohols in good yields.
- Sreekumar,Padmakumar,Rugmini
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p. 5151 - 5154
(2007/10/03)
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- Modified borohydride agents, bis(triphenylphosphine) (tetra-hydroborato)zinc complex [Zn(BH4)2(PPh3)2] and (triphenylphosphine) (tetrahydroborato)zinc complex [Zn(BH4)2(PPh3)]. New ligand metal borohydrides as stable, efficient, and versatile reducing agents
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Bis(triphenylphosphine)(tetrahydroborato)zinc and (triphenylphosphine)(tetrahydroborato) zinc complexes have been used for the efficient reductions of varieties of organic compounds in THF or under solvent free conditions. Selective reduction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, and acyl chlorides to their corresponding alcohols and aryl, alkyl, aroyl, and sulfonyl azides to their corresponding amines and amides are described. Bis(triphenylphosphine)(tetrahydroboratro)zinc complex shows promising shelf stability and is much more stable than its mono triphenylphosphine analogue. The reducing ability of the two complexes is more or less the same.
- Firouzabadi, Habib,Adibi, Mina,Ghadami, Mahboobeh
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p. 191 - 220
(2007/10/03)
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- Asymmetric hydrogenation of cyclic α,β-unsaturated ketones to chiral allylic alcohols
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The Ru(II)-BINAP-1,2-diphenylethylenediamine combined catalyst system effects asymmetric hydrogenation of certain cyclic enones in 2-propanol containing KOH with a substrate/catalyst molar ratio of 250 to 2500. The hydrogenation occurs selectively at the C=O function with excellent enantio- or diastereoselectivity.
- Ohkuma, Takeshi,Ikehira, Hideyuki,Ikariya, Takao,Noyori, Ryoji
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p. 467 - 468
(2007/10/03)
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- Highly regio- and stereoselective reductions of carbonyl compounds in aqueous glycosidic media
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Highly regioselective reductions of α,β-unsaturated ketones to the corresponding allylic alcohols were performed in essentially quantitative yields in aqueous media containing either glycosidic surfactants or amphiphilic carbohydrates. Reductions of cyclohexanones and cyclohexenones lead under the same conditions, stereoselectively to reduced compounds bearing an equatorial alcohol function. Hydrophobic interactions between amphiphilic carbohydrates and lipophilic substrates were modelized and should account for the observed stereodifferentiation.
- Denis, Cecile,Laignel, Benoit,Plusquellec, Daniel,Le Marouille, Jean-Yves,Botrel, Alain
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- Diastereoselectivity in the epoxidation of substituted cyclohexenes by dimethyldioxirane
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Three series of compounds based on the cyclohexene framework have been epoxidized by dimetbyldioxirane. A pronounced dependence of epoxide diastereoselectivity on substituent has been observed. In addition there is a solvent influence on this stereoselectivity. The results have been explained by invoking steric, H-bonding, and dipole - dipole influences on the epoxide stereochemistry.
- Murray, Robert W.,Singh, Megh,Williams, Brian L.,Moncrieff, Hazel M.
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p. 1830 - 1841
(2007/10/03)
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- The Roles of 2- and 3-Axial Methoxy Groups in Determining the Stereochemistry of the Complex Metal Hydride Reduction of Cyclohexanones: Examination of the Cieplak Model
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The 2- and 3-axially substituted methoxy groups in cyclohexanones exhibit steric hindrance similar to that of the methyl group in LiAlH4 and NaBH4 reductions. The chelate complex formation between the zinc ion and the two oxygens in the molecule was suggested in the zinc borohydride reduction. The relative reactivities of cyclohexanones in which the 2-axial position is substituted by the methyl or the methoxy group in the LiAlH4 reduction strongly support Cieplak's proposal, which focuses on the importance of the stabilization of the transition state by anti-periplanar allylic bonds.
- Senda, Yasuhisa,Sakurai, Hiroshi,Nakano, Shigeru,Itoh, Hiroki
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p. 3297 - 3303
(2007/10/03)
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- Aminoborohydrides. 4. The Synthesis and Characterization of Lithium Aminoborohydrides: A New Class of Powerful, Selective, Air-Stable Reducing Agents
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Lithium aminoborohydrides (LiABH3) are a new class of powerful yet selective reducing agents that reproduce, in air, virtually all of the transformations for which lithium aluminum hydrides is now used.LiABH3's can be readily prepared as solids or generated in situ, are nonpyrophoric, and liberate hydrogen only slowly with protic solvents above pH 4.LiABH3's can be handled in dry air as easily as sodium borohydride and retain their chemical activity for at least 6 month when stored under nitrogen or dry air at 25 deg C.LiABH3's can be synthesized from any primary or secondary amine, thus allowing control of the steric and electronic environment of these reagents.
- Fisher, Gary B.,Fuller, Joseph C.,Harrison, John,Alvarez, Salvador G.,Burkhardt, Elizabeth R.,et al.
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p. 6378 - 6385
(2007/10/02)
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- A Radical Cyclisation Strategy to α-Spiro-β-methylene-γ-butyrolactones. Total Synthesis of (+/-)-Norbakkenolide-A
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The 5-exo-dig radical cyclisation reaction of the bromoacetals 9, obtained from the enol ethers 8, and treatment of the resulting hemiacetal 10 with Jones' reagent transforms the cyclic ketones 7 and 12 into α-spiro-β-methylene-γ-butyrolactones 11 and norbakkenolide-A 2.
- Srikrishna, Adusumilli,Nagaraju, Sankuratri,Sharma, G. Veera Raghava
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p. 285 - 288
(2007/10/02)
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- Aminoborohydrides. 2. Regiospecific reductions of α,β-unsaturated carbonyl compounds with lithium pyrrolidinoborohydride. A facile conversion of α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols in high purity
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Lithium aminoborohydrides (LiABH3), obtained by the reaction of n-BuLi with amine-boranes, are powerful reducing agents for the reduction α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols. Thus, lithium pyrrolidinoborohydride (LiPyrrBH3) and reduces cinnamaldehyde and cyclohexenone to give exclusively cinnamyl alcohol and 2-cyclohexen-1-ol respectively. This 1,2-reduction appears to be general and ester groups are tolerated. The yield of allylic alcohols from this procedure is essentially quantitative.
- Fuller, Joseph C.,Stangeland, Eric L.,Goralski, Christian T.,Singaram, Bakthan
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p. 257 - 260
(2007/10/02)
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