- Synthesis and structural elucidation of (pyridyl)imine Fe(II) complexes and their applications as catalysts in transfer hydrogenation of ketones
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Reactions of (pyridyl)imine ligands: 2,6-diisopropyl-N-[(pyridine-2-yl)methylene]aniline (L1), 2,6-diisopropyl-N-[(pyridine-2-yl)ethylidene]aniline (L2), 2,6-dimethyl-N-[(pyridine-2-yl)methylene]aniline (L3), 2,6-dimethyl-N-[(pyridine-2-yl)ethylidene]aniline (L4) and N-[(pyridine-2-yl)methylene]aniline (L5) with FeCl2 salt afforded the corresponding paramagnetic Fe(II) complexes [Fe(L1)2Cl][FeCl4] (Fe1), [Fe(L2)2Cl][FeCl4] (Fe2), [Fe(L3)2Cl][FeCl4] (Fe3), [Fe(L4)2Cl][FeCl4], (Fe4), [Fe(L5)2Cl2] (Fe5) in good yields. On the other hand, reactions of L1 with FeCl2 in the presence of NaPF6 afforded complex [Fe(L1)2Cl][PF6] (Fe6) in moderate yields. Molecular structures of complexes Fe1 and Fe2 reveal the formation of cationic species containing two N^N bidentate ligands and one chlorido co-ligand to give five-coordinate geometry with [FeCl4]? as counter-anion. On the other hand, complex Fe5, is an octahedral neutral species containing two bidentate L5 and two chlorido ligands. All the complexes (Fe1–Fe6) formed active catalysts in the transfer hydrogenation of ketones affording average yields of about 85%. The ligand architecture, reaction conditions and nature of substrate influenced the catalytic activities of the complexes. Mercury and subs-stoichiometric poisoning tests pointed to the existence of both Fe(0) nanoparticles and homogeneous Fe(II) species as the active intermediates.
- Tsaulwayo, Nokwanda,Kumah, Robert T.,Ojwach, Stephen O.
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- 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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- Synthesis and Applications of (Pyridyl)imine Fe(II) Complexes as Catalysts in Transfer Hydrogenation of Ketones
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Abstract: Chiral (pyridyl)imine Fe(II) complexes, [Fe(L1)3]2+[PF6?]2, (Fe1), [Fe(L2)3]2+[PF6?]2, (Fe2), [Fe(L3)3]2+[PF6?]2 (Fe3), and [Fe(L4)3]2+[PF6?]2 (Fe4) were synthesised by reactions of synthons (S-)-1-phenyl-N-(pyridine-2-yl) ethylidine)ethanamine (L1), (R-)-1-phenyl-N-(pyridine-2-yl) ethylidine) ethanamine (L2), (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3) and (S)-1-phenyl-N-(pyridine-2-yl methylene)ethanamine (L4) with the FeCl2 salt. The solid-state structure of complex Fe4 showed that the?Fe atom contains three units of bidentate bound ligand L4 to form a six-coordinate cationic compound. The Fe(II) complexes were evaluated as catalysts in asymmetric transfer hydrogenation of ketones reactions and showed moderate catalytic activities with low enantioselectivity. Catalytic activities of the respective complexes were regulated by the nature of the metal complexes, ketone substrate and reaction conditions. Mercury and sub-stoichiometric poisoning experiments implicate possible formation of both active Fe(0) nanoparticles and Fe(II) homogeneous intermediates. Graphic Abstract: [Figure not available: see fulltext.]
- Kumah, Robert T.,Vijayan, Paranthaman,Ojwach, Stephen O.
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p. 344 - 352
(2020/07/25)
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- Enantioselective Cyclopropanation/[1,5]-Hydrogen Shift to Access Rauhut-Currier Product
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A Michael addition initiated cyclopropanation/[1,5]-hydrogen shift has been developed for the enantioselective synthesis of Rauhut-Currier products. The reaction of α-alkyl diazoesters and in situ generated o-quinone methides proceeds in the presence of c
- Kim, Seung Tae,Pandit, Rameshwar Prasad,Yun, Jaesook,Ryu, Do Hyun
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supporting information
p. 213 - 217
(2021/01/09)
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- Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
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The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
- Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 15617 - 15631
(2021/05/19)
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- Triazole compound, preparation method and application of triazole compound in preparation of medicine for preventing and treating cancer
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The invention provides a compound shown as a formula (I) or pharmaceutically acceptable salt thereof. In the formula (I), Ar is selected from any one of a substituted aromatic ring group or a substituted aromatic heterocyclic group; R1 is selected from an
- -
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Paragraph 0116-0121
(2021/06/09)
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- New alkoxymethyl-functionalized pyridinium-based chiral ionic liquids: synthesis, characterization and properties
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Abstract: An efficient solvent-free synthesis of a new family of functionalized chiral ionic liquids based on pyridinium cation has been developed from low-cost chiral terpenoid alcohols. An exhaustive characterization was performed using state-of-the-art
- Gondal, Humaira Yasmeen,Mumtaz, Salma,Abbaskhan, Ahmed,Mumtaz, Nargis,Cano, Israel
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p. 2951 - 2963
(2020/03/23)
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- Synthesis and characterization of Pd(II) and Ru(II) complexes of tetradentate N,N,N,N-(Diphosphinomethyl)amine ligands: Catalytic properties in transfer hydrogenation and heck coupling reactions
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– Tetradentate N,N,N,N-(diphosphinomethyl)amine ligands and their Pd(II) and Ru(II) complexes were synthesized under a nitrogen atmosphere using Schlenk technique. The synthesized ligands and the complexes were characterized with 1H- and 31P-NMR, FT-IR, TG/DTA, and elemental analysis techniques. Pd(II) Complexes were used as catalysts in Heck coupling reactions and Ru(II) complexes were tried in transfer hydrogenation reactions of acetophenone derivatives. According to the results, L4-Pd(II) complex showed the best catalytic activity in the Heck coupling reaction of p-methylbromobenzene with o-chlorostyrene. It was confirmed that the reduction of bromo and chloroacetophenones in all catalysts the conversions were higher. The results showed that Ru(II) complexes as efficient catalysts and up to 99percent conversions was occurred with bromo and chloro acetophenones in K2CO3/isopropyl alcohol media at 80 °C.
- Akkaya, Seda K??ker,Kele?, Mustafa,Uru?, Serhan
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- [4 + 2]-Cycloaddition and 1,4-Addition of ortho-Quinone Methides by a Chiral Crotyl Silane
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Anhydrous FeCl3 in the presence of 2,6-lutidine promotes the substrate-controlled enantioselective [4 + 2]-cycloaddition and crotylation reaction between an enantioenriched (S,E)-crotyl silane and in situ generated ortho-quinone methides (oQMs)
- Wong, Christopher R.,Hummel, Gerald,Cai, Yongqi,Schaus, Scott E.,Panek, James S.
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supporting information
p. 32 - 35
(2019/01/04)
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- A Simple Synthesis of Densely Substituted Benzofurans by Domino Reaction of 2-Hydroxybenzyl Alcohols with 2-Substituted Furans
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The Br?nsted acid-catalyzed cascade synthesis of densely substituted benzofurans from easily available salicyl alcohols and biomass-derived furans has been developed. The disclosed sequence includes the intermediate formation of 2-(2-hydroxybenzyl)furans
- Abaev, Vladimir T.,Chalikidi, Petrakis N.,Kekhvaeva, Anna E.,Makarov, Anton S.,Trushkov, Igor V.,Uchuskin, Maxim G.
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p. 3747 - 3757
(2019/09/30)
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- Selective Room-Temperature Hydrogenation of Carbonyl Compounds under Atmospheric Pressure over Platinum Nanoparticles Supported on Ceria-Zirconia Mixed Oxide
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A Pt/CeO2-ZrO2 catalytic system was able to initiate an extremely intense hydrogen spillover providing a huge amount of activated hydrogen (12 mol/mol Pt) at temperatures –50°C - +25°C, which was not observed before. The idea was to use this activated hydrogen for reduction of carbonyl compounds under ambient conditions. Thus, the efficient and selective heterogeneous hydrogenation of carbonyl compounds of different structure, including 5-hydroxymethylfurfural and cinnamaldehyde, to the corresponding alcohols with quantitative yields was successfully performed over the Pt/CeO2-ZrO2 catalysts at room-temperature and atmospheric pressure of H2. The proposed catalysts afforded hydrogenation under significantly milder conditions with a much higher activity and selectivity compared to the commercial catalysts and reported catalytic systems. Hydrogenation of the C=O bond in the presence of a C=C bond proceeded with a high regioselectivity.
- Redina, Elena A.,Vikanova, Kseniia V.,Kapustin, Gennady I.,Mishin, Igor V.,Tkachenko, Olga P.,Kustov, Leonid M.
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supporting information
p. 4159 - 4170
(2019/07/12)
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- Synthesis, Stability, and (De)hydrogenation Catalysis by Normal and Abnormal Alkene- And Picolyl-Tethered NHC Ruthenium Complexes
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A series of p-cymene and cyclopentadienyl Ru(II)-aNHC complexes were synthesized from 2-methylimidazolium salts with either an N-bound alkenyl (1, 3) or picolyl tether (6, 7). The C(5)-Me substituted alkenyl-tethered analogues (2, 4) were also synthesized. Ag-mediated C(2)-dealkylation was a prominent side reaction that led to the formation of normally bound NHC Ru(II) complexes, which in selected cases were isolated (5, 8). A C(4)- over C(2)-selectivity for ruthenium binding was established by protecting the C(2)-position with an iPr group on the imidazolium precursor, for which unique p-cymene (9) and cyclopentadienyl (10) Ru(II)-aNHC derivatives were synthesized. All complexes were applied in the transfer hydrogenation of ketones and in secondary alcohol oxidation, with higher catalytic activity for the p-cymene over the cyclopentadienyl systems, as well as the alkenyl- over the picolyl-containing aNHC complexes.
- Malan, Frederick P.,Singleton, Eric,Van Rooyen, Petrus H.,Albrecht, Martin,Landman, Marilé
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p. 2624 - 2635
(2019/07/03)
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- Structural, kinetics and mechanistic studies of transfer hydrogenation of ketones catalyzed by chiral (pyridyl)imine nickel(ii) complexes
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The chiral synthons (S-)-1-phenyl-N-(pyridine-2-yl)ethylidine)ethanamine (L1), (R-)-1phenyl-N-(pyridine-2-yl)ethylidine))ethanamine (L2) (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3), and (R)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L4) were synthesized in good yields. Treatments of L1-L4 with NiBr2(DME) and NiCl2 precursor afforded dinuclear complexes [Ni2(L1)4-μ-Br2]NiBr4 (Ni1), [Ni2(L2)4-μ-Br2]NiBr4 (Ni2), [Ni2(L3)4-μBr2]Br2 (Ni3), [Ni2(L4)4-μ-Br2]NiBr4 (Ni4) and [Ni(L4)2Cl2] (Ni5). The identities of the compounds were established using NMR, FT-IR and EPR spectroscopy, mass spectrometry, magnetic moments, elemental analysis and single crystal X-ray crystallography. The dinuclear dibromide nickel complexes dissociate into mononuclear species in the presence of strongly coordinating solvents. Compounds Ni1-Ni5 displayed moderate catalytic activities in the asymmetric transfer hydrogenation (ATH) of ketones, but with low enantiomeric excess (ee%). Both mercury and substoichiometric poisoning tests pointed to the homogeneous nature of the active species with the partial formation of catalytically active Ni(0) nanoparticles. Low resolution mass spectrometry analyses of the intermediates supported a dihydride mechanistic pathway for the transfer of hydrogenation reactions.
- Kumah, Robert T.,Tsaulwayo, Nokwanda,Xulu, Bheki A.,Ojwach, Stephen O.
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supporting information
p. 13630 - 13640
(2019/09/30)
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- Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions
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We recently reported a novel hybrid batch-flow synthesis of the antipsychotic drug clozapine in which the reduction of a nitroaryl group is described under flow conditions using sodium dithionite. We now report the expansion of this method to include the reduction of aldehydes. The method developed affords yields which are comparable to those under batch conditions, has a reduced reaction time and improved space-time productivity. Furthermore, the approach allows the selective reduction of aldehydes in the presence of ketones and has been demonstrated as a continuous process.
- Neyt, Nicole C.,Riley, Darren L.
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supporting information
p. 1529 - 1536
(2018/07/05)
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- Lewis Base Catalyzed Intramolecular Reduction of Salicylaldehydes by Pinacol-Derived Chlorohydrosilane
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A newly developed stable chlorohydrosilane derived from pinacol is herein described. This was successfully used in the reduction of salicylaldehydes in reasonable to excellent yields (51–97 %). The ability of the hydrosilane to react as a reducing agent is increased upon the in situ formation of a trialkoxyhydrosilane and activation with a Lewis base, as further indicated by density functional theory studies. 1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) was identified to be a suitable catalyst for this metal-free reduction, promoting the regio- and chemoselective reduction of aldehydes in ortho-position to phenols, despite the presence of vicinal ketones. The performance of pinacol-derived chlorohydrosilane in the reduction of salicylaldehydes was further observed to be superior to that of well-established commercially available chlorohydrosilanes.
- Assoah, Benedicta,Vale, Jo?o R.,Kalenius, Elina,Veiros, Luis F.,Candeias, Nuno R.
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supporting information
p. 2910 - 2917
(2018/06/27)
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- Enantiospecific Synthesis of ortho-Substituted Benzylic Boronic Esters by a 1,2-Metalate Rearrangement/1,3-Borotropic Shift Sequence
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Coupling reactions between benzylamines and boronic esters have been investigated. ortho-Lithiated benzylamines react with boronic esters and a N-activator to afford ortho-substituted benzylic boronic esters with formal 1,1′-benzylidene insertion into the C-B bond. The reaction occurs by a SN2′ elimination and 1,2-metalate rearrangement of the N-activated boronate complex to afford a dearomatized intermediate, which undergoes a Lewis-acid catalyzed 1,3-borotropic shift to afford the boronic ester products in high yield and with excellent enantiospecificity. The use of enantioenriched α-substituted benzylamines gave the corresponding secondary boronic esters with high ee.
- Aichhorn, Stefan,Bigler, Raphael,Myers, Eddie L.,Aggarwal, Varinder K.
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supporting information
p. 9519 - 9522
(2017/07/25)
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- Multicomponent Condensation Reactions via ortho-Quinone Methides
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Iron(III) salts promote the condensation of aldehydes or acetals with electron-rich phenols to generate ortho-quinone methides that undergo Diels - Alder condensations with alkenes. The reaction sequence occurs in a single vessel to afford benzopyrans in up to 95% yield. The reaction was discovered while investigating a two-component strategy using 2-(hydroxy(phenyl)methyl)phenols to access the desired ortho-quinone methide in a Diels - Alder condensation. The two-component condensation also afforded the corresponding benzopyran products in yields up to 97%. Taken together, the two- and three-component strategies using ortho-quinone methide intermediates provide efficient access to benzopyrans in good yields and selectivities.
- Allen, Emily E.,Zhu, Calvin,Panek, James S.,Schaus, Scott E.
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p. 1878 - 1881
(2017/04/11)
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- SBA-15-supported N-coordinate ruthenium(II) materials bearing sulfonamide-type ligands: Effect of ligand backbones on catalytic transfer hydrogenation of ketones and aldehydes
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[RuLCl(p-cymene)] (L?=?N-arylsulfonylphenylenediamine) complexes (2a–d) were synthesized from the reaction between [Ru(p-cymene)Cl2]2 and ligand. Additionally, SBA-15–[RuLCl(p-cymene)] derived catalysts (3a–d) w
- Dayan, Serkan,Kayaci, Nilgun,Kalaycioglu Ozpozan, Nilgun,Dayan, Osman
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- Syntheses, characterisation, and catalytic role of (η5-C5Me5)Rh(III) guanidinato complexes in transfer hydrogenation (TH) and TH-etherification
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A family of air stable half sandwich meal guanidinato complexes ([(η5-Cp?)MCl{κ2(N,N′)((ArN)2C-N(H)Ar)}]) (M = Rh and Ir; Cp? = C5Me5; Ar = aryl) were synthesized in good yield and characterised by elemental analyses, IR, and NMR (1H, 13C, and 19F) spectroscopy. The geometry of the metal and the conformations of the guanidinate ligands in the complexes were studied by single crystal X-ray diffraction. The solution behaviour of representative complexes was investigated by detailed NMR studies including variable temperature and variable concentration 1H NMR measurements. The new complexes were screened as catalysts for transfer hydrogenation (TH) of acetophenone under basic and base free conditions and from these experiments, ([(η5-Cp?)RhCl{κ2(N,N′)((ArN)2C-N(H)Ar)}]) (Ar = 3,5-(CF3)2C6H3; 3) was chosen as the preferred catalyst due to its slightly better catalytic activity than other complexes. The utility of 3 in TH of a variety of carbonyl compounds was explored under basic and base free conditions. Tandem catalysis involving TH of a carbonyl group and etherification of the resulting -CH2OH group in reduction products of salicylaldehyde, 2-hydroxy-1-naphthaldehyde and 5-(hydroxymethyl)furfural was achieved in the presence of 3 under base free conditions. The role of the guanidinate ligands in the complexes for basic and base free TH of carbonyl compounds and TH-etherification tandem catalysis is discussed. Plausible mechanisms for TH and TH-etherification are outlined.
- Kumar, Robin,Thirupathi, Natesan
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p. 33890 - 33904
(2017/07/17)
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- One step synthesis of 2-alkenylchromanes via inverse electron-demand Hetero-Diels–Alder reaction of o-quinone methide with unactivated dienes
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The synthetically important 2-alkenylchromane derivatives were constructed in good yields under metal-free condition via inverse electron demand Hetero-Diels–Alder reaction of o-quinone methides with unactivated dienes. This strategy features mild conditi
- Liu, Jian,Wang, Xiaoxiao,Xu, Lubin,Hao, Zhihui,Wang, Liang,Xiao, Jian
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supporting information
p. 7642 - 7649
(2016/11/11)
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- A Total Synthesis of Paeoveitol
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A four-step total synthesis of paeoveitol (1), a recently disclosed norditerpene natural product from Paeonia vetchii, is reported. This highly concise synthetic route was guided by biosynthetic considerations and enabled by an unusual intermolecular orth
- Xu, Lun,Liu, Fengyi,Xu, Li-Wen,Gao, Ziwei,Zhao, Yu-Ming
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supporting information
p. 3698 - 3701
(2016/08/16)
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- Ansa-Ruthenium(II) Complexes of R2NSO2DPEN-(CH2)n(η6-Aryl) Conjugate Ligands for Asymmetric Transfer Hydrogenation of Aryl Ketones
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New 3rd generation designer ansa-ruthenium(II) complexes featuring N,C-alkylene-tethered N,N-dialkylsulfamoyl-DPEN/η6-arene ligands, exhibited good catalytic performance in the asymmetric transfer hydrogenation (ATH) of various classes of (het)aryl ketones in formic acid/triethylamine mixture. In particular, benzo-fused cyclic ketones furnished 98 to >99.9% ee using a low catalyst loading.
- Ki?ic, Andrea,Stephan, Michel,Mohar, Barbara
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supporting information
p. 2540 - 2546
(2015/08/18)
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- Characterization of an excellent anti-Prelog short-chain dehydrogenase/reductase EbSDR8 from Empedobacter brevis ZJUY-1401
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Empedobacter brevis ZJUY-1401 is capable of producing anti-Prelog alcohols with excellent stereoselectivity. The gene encoding a short-chain dehydrogenase/reductase from E. brevis ZJUY-1401 (EbSDR8) was cloned and heterologously expressed in Escherichia coli, and the purified recombinant protein was characterized. The subunit of EbSDR8 is composed of 250 amino acids with a calculated molecular mass of 26.4 kDa. Important properties regarding the application of EbSDR8 include utilization of cheaper coenzyme, the excellent catalytic performance over a broad pH range from 7.0 to 10.5, and temperature optimum of 35 °C. The enzyme showed moderate thermostability, with half-lives of 4.4 h at 35 °C and 3.1 h at 45 °C, respectively. In the presence of isopropanol as a cosubstrate, the whole-cell of recombinant E. coli expressing EbSDR8 could efficiently catalyze the asymmetric reduction without addition of any NADH into the reaction system. EbSDR8 displayed good activity and excellent stereoselectivity toward a spectrum of acetophenone derivatives, providing anti-Prelog alcohols with >99% ee for the majority of the substrates. These results suggest that EbSDR8 is a powerful chiral tool for the production of anti-Prelog alcohols.
- Li, Aipeng,Ye, Lidan,Wu, Hongping,Yang, Xiaohong,Yu, Hongwei
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p. 179 - 187
(2015/10/12)
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- Iridium-catalyzed hydrogen transfer: Synthesis of substituted benzofurans, benzothiophenes, and indoles from benzyl alcohols
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An iridium-catalyzed hydrogen transfer has been developed in the presence of p-benzoquinone, allowing the synthesis of a diversity of substituted benzofurans, benzothiophenes, and indoles from substituted benzylic alcohols.
- Anxionnat, Bruno,Gomez Pardo, Domingo,Ricci, Gino,Rossen, Kai,Cossy, Janine
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supporting information
p. 3876 - 3879
(2013/09/02)
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- A mild method for generation of o-quinone methides under basic conditions. the facile synthesis of trans-2,3-dihydrobenzofurans
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A novel and efficient method for the generation of o-quinone methide intermediates was developed from the readily available 2-tosylalkylphenols under the mild basic conditions, and their reactions with sulfur ylides were investigated for the stereoselective synthesis of trans-2,3-dihydrobenzofurans. The Royal Society of Chemistry 2013.
- Chen, Mu-Wang,Cao, Liang-Liang,Ye, Zhi-Shi,Jiang, Guo-Fang,Zhou, Yong-Gui
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supporting information
p. 1660 - 1662
(2013/03/14)
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- Highly active mesoporous chromium silicate catalysts in side-chain oxidation of alkylaromatics
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We approach a green method in the production of alkylaromatic ketones over hexagonally ordered mesoporous CrSBA-15 catalysts, which were used, in green routes, in the liquid-phase oxidation of alkylaromatics. A promising chemical treatment method was used with ammonium acetate solution to remove the toxic nature of non-framework chromium oxides deposited on the surface of calcined CrSBA-15(8), and the obtained green mesoporous CrSBA-15(8) catalyst was used to find its catalytic activity while the recyclability of mesoporous CrSBA-15 catalysts was also studied. Particularly, the mesoporous CrSBA-15 catalysts synthesized with a variety of chromium contents were extensively used in the production of acetophenone (APO) with various reaction parameters. On the basis of all catalytic results, the mesoporous CrSBA-15(8) catalyst produced a higher selectivity of alkylaromatic ketones (76-100%) as compared to other CrSBA-15 catalysts and was found to be a highly active, recyclable and promising heterogeneous catalyst for selective synthesis of alkylaromatic ketones. The Royal Society of Chemistry 2012.
- Selvaraj,Park,Kim,Kawi,Ha
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p. 14204 - 14210
(2013/01/15)
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- Selective reduction of aldehydes and ketones to alcohols with ammonia borane in neat water
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Chemoselective reduction of various carbonyl compounds to alcohols with ammonia borane (AB), a nontoxic, environmentally benign, and easily handled reagent, in neat water was achieved in quantitative conversions and high isolated yields. Interestingly, α- and β-keto esters were selectively reduced to corresponding hydroxyl esters by AB, while diols were obtained when sodium borohydride was used as a reducing agent. The procedure is also compatible with the presence of a variety of base-labile protecting groups, such as tosyl, acetyl, benzoyl, ester groups, and acid-labile protecting groups such as trityl and TBDMS groups, and others, such as the unsaturated double bond, nitro and cyano groups. Finally, a kilo scale reaction of methyl benzoylformate with AB was conducted in water and gave methyl mandelate in 94% yield.
- Shi, Lei,Liu, Yingying,Liu, Qingfeng,Wei, Bin,Zhang, Guisheng
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experimental part
p. 1372 - 1375
(2012/06/04)
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- Asymmetric reduction of acetophenone derivatives by Lens culinaris
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The enzymatic reduction of acetophenone derivatives has been evaluated using whole cells from the edible plant lentil (Lens culinaris) as biocatalyst to afford chiral (R) and (S)-alcohols in enantiomeric excess 68-99%. Acetophenone was selected as the model substrate for enantioselective bioreduction. The reaction was performed under a range of conditions in order to optimize the bioreduction procedure with respect to reaction time, media and optimal mass of lentil. With substituted (fluorine, chlorine, bromine, methyl, hydroxyl, methoxy, amino and nitro groups) acetophenones, electronic and steric influences on the course of the reaction were observed.
- Ferreira, Daniele Alves,Da Costa Assun??o, Jo?o Carlos,De Lemos, Telma Leda Gomes,Monte, Francisco José Queiroz
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p. 469 - 475
(2013/02/23)
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- Candida tenuis xylose reductase catalysed reduction of acetophenones: The effect of ring-substituents on catalytic efficiency
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The catalytic efficiencies of Candida tenuis xylose reductase catalysed reductions of mono-substituted acetophenones are in reasonable correlation with the σ-Hammett coefficients of the substituted phenyl groups. Variations of the substrate transformation rates are hence mainly caused by mesomeric and inductive effects of the substituents, while differences in substrate binding have a secondary relevance. Some substrate 1H NMR chemical shifts and carbonyl IR absorption bands are in reasonable accordance with the catalytic activities and allow the estimation of the transformation rates with good accuracy. The resulting substituted (S)-1-phenyl ethanols are generated in very high enantiomeric excess.
- Vogl, Michael,Kratzer, Regina,Nidetzky, Bernd,Brecker, Lothar
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experimental part
p. 5863 - 5870
(2011/09/30)
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- Iridium-catalyzed arene ortho -silylation by formal hydroxyl-directed C-H activation
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A strategy for the ortho-silylation of aryl ketone, benzaldehyde, and benzyl alcohol derivatives has been developed in which a hydroxyl group formally serves as the directing element for Ir-catalyzed arene C-H bond activation. One-pot generation of a (hyd
- Simmons, Eric M.,Hartwig, John F.
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p. 17092 - 17095
(2011/03/01)
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- Novel iodine reagent system for regioselective cleavage of epoxides to alcohols
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Epoxides are converted regioselectively to corresponding higher substituted alcohols with greater yields using diphosphorus tetraiodide (P 2I4) as a reducing agent and a catalytic amount of tetraethylammonium bromide at room temperature. Copyright Taylor & Francis Group, LLC.
- Telvekar, Vikas N.,Rane, Rajesh A.
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scheme or table
p. 2108 - 2112
(2010/08/19)
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- Reduction of aldehydes and ketones with NaBH4/Al 2O3 under solvent-free conditions
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Aldehydes and ketones are efficiently reduced to the corresponding alcohol using NaBH4 supported onto alumina under solvent free conditions. It was found that the presence of small amount of methanol in reaction media is essential. Chemoselective 1,2-reduction of α, β- unsaturated carbonyl compounds to the corresponding allylic alcohols are also observed.
- Shalbaf
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experimental part
p. 6761 - 6764
(2012/06/18)
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- One-pot synthesis of polyfunctionalized 4H-chromenes and dihydrocoumarins based on copper(II) bromide-catalyzed C-C coupling of benzylic alcohols with ketene dithioacetals
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The synthesis of polyfunctionalized 4Hchromenes 3 and dihydrocoumarins 4 has been developed from the same substrates. Catalyzed by copper(II) bromide (0.3 equiv.), the reactions of the easily available ketene dithioacetals 1 with 2-(hydroxymethyl)phenols 2 lead to 4/7-chromenes 3 in high to excellent yields in dichloromethane solvent, whereas, 3,4-trans-disubstituted dihydrocoumarins 4 are obtained in high yields with high diastereoselectivities by prolonging the reaction time or changing the solvent from dichloromethane to acetonitrile.
- Liang, Deqiang,Wang, Mang,Bekturhun, Bahargul,Xiong, Binbin,Liu, Qun
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supporting information; experimental part
p. 1593 - 1599
(2010/09/08)
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- Palladium catalyzed isomerization of alkenes: A pronounced influence of an o-phenol hydroxyl group
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A novel palladium catalyzed isomerization of alkenes has been found, where an ortho-phenol hydroxyl group has a pronounced influence on the isomerization.
- Fan, Jinmin,Wan, Changfeng,Wang, Qiang,Gao, Linfeng,Zheng, Xiaoqi,Wang, Zhiyong
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supporting information; experimental part
p. 3168 - 3172
(2011/02/25)
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- Facile construction of functionalized 4H-chromene via tandem benzylation and cyclization
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A series of functionalized 4H-chromenes have been constructed by using a novel FeCl3-catalyzed benzylation-cyclization tandem reaction. The Royal Society of Chemistry.
- Fan, Jinmin,Wang, Zhiyong
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supporting information; experimental part
p. 5381 - 5383
(2009/03/11)
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- Asymmetric synthesis of (-)-adaline
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(Matrix presented) (-)-adaline An enantioselective total synthesis of (-)-adaline has been achieved starting from a chiral 6,6-disubstituted piperidone derivative previously prepared by diastereoselective allylation of a chiral tricyclic N-acyl-N,O-acetal
- Itoh, Toshimasa,Yamazaki, Naoki,Kibayashi, Chihiro
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p. 2469 - 2472
(2007/10/03)
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- Synthesis of chiral organotin reagents: Synthesis of bicyclo[2.2.1]heptan-2-yl(diphenyl)tin hydrides with cis-disposed, oxygen-containing substituents
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Alkylation of the methyl 3-triphenylstannylbicyclo[2.2.1]hept-5-ene-2-carboxylate 3 using lithium diethylamide and either methyl iodide or benzyl bromide at -78°C is stereoselective in favour of the endo-alkylated products 10 and 11. Methylation of the saturated ester 12 is also endo-selective in favour of 13. If the unsaturated ester 3 is deprotonated at 0°C rather than at -78°C, the rearranged stannane 17 is obtained as a side-product. The endo-triphenylstannylbicyclo[2.2.1]heptane-2-carboxylate 22 has been prepared from the ester 12 by phenylselenylation, oxidative elimination and reduction using diimide. The triphenylstannanes 13, 17 and 20 have been converted into the alkyl(diphenyl)tin hydrides 27, 28 and 29 and the methoxyalkyltin hydride 36 has also been prepared and characterized. These tin hydrides accelerate the reduction of aryl methyl ketones to 1-arylethanols by phenylsilane, but the reduction product is racemic. Syntheses of the aminobicycloalkyl(triphenyl)stannanes 44, 45 and 48 are described.
- Pratt, Robert M.,Thomas, Eric J.
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p. 727 - 736
(2007/10/03)
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- Cadmium Chloride-Magnesium-Water: A New System For Reduction of Various Organic Functionalities
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Cadmium chloride-magnesium-THF-water efficiently reduced aldehydes and ketones to their corresponding alcohols, epoxide to mono-alcohol, benzyl halide to toluene, acid chloride to aldehyde and hydrolyzed thioketals to corresponding ketones. Key words: Cadmium chloride-magnesium-THF-H2O, reductions.
- Bordoloi, Manobjyoti
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p. 1681 - 1684
(2007/10/02)
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- An Internally Activated Tin Hydride with Enhanced Reducing Ability
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Tin hydride 1 is activated for nucleophilic hydride transfer and also for radical chain reduction, depending on solvent.The nucleophilic hydride pathway is favored in methanol, and 1 can be used as a selective reducing agent for ketones.Simple ketones are not reduced in aprotic solvents, but β-hydroxy ketones are activated internally by the hydroxyl group and can be reduced in THF with good control of stereochemistry, as in the conversion from 7 to 9 (30:1 9:8).A catalytic version of the nucleophilic hydride reductions in methanol has been developed using PhSiH3 as the stoichiometric hydride source.Radical chain dehalogenations can also be achieved with 1 at room temperature and without added radical initiators.Simple xanthates are not reduced efficiently in the absence of an initiator, but the reaction proceeds in the presence of AIBN.
- Vedejs, E.,Duncan, S. M.,Haight, A. R.
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p. 3046 - 3050
(2007/10/02)
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- Intramolecular acylation during acid chloride formation of some o-styryl phenoxyacetic acids
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o-Isopropenyl phenoxyacetic acids 1 and 8 on treatment with thionyl chloride followed by aqueous workup furnished the acylated products 4 and 9 in moderate yields. The corresponding acid chlorides could also be cyclised with stannic chloride. The acid chl
- Biswas,Ghosh,Venkateswaran
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p. 1865 - 1874
(2007/10/02)
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- Convenient synthesis of 3-acyl- and 3-alkyl-1,2-naphthoquinones
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3-Acyl-1,2-naphthalenediols prepared by the photoinduced addition reaction of 1,2-naphthoquinone with alkanals were oxidized with Fremy's salt to give 3-acyl-1,2-naphthoquinones in good yields. The diols were reduced with amalgamated zinc, followed by oxidation to afford 3-alkyl-1,2-naphthoquinones in moderate yields.
- Takuwa,Kai
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p. 623 - 625
(2007/10/02)
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- Synthesis of Highly Pure Enantiomers of the Insecticide Salithion
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Optically active salithion (>98percent e.e.) was obtained via an L-proline methyl ester derivative (PS), whose diastereomers were easily separated, with subsequent sulfuric acid-catalyzed methanolysis.The configuration of each diastereomeric PS was determ
- Wu, Shao-Yong,Hirashima, Akinori,Eto, Morifusa,Yanagi, Kazunori,Nishioka, Eriko,Moriguchi, Koichi
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p. 157 - 164
(2007/10/02)
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- Metabolic Formation of 4-Methyl-4H-1,3,2-benzodioxaphosphorins from Bis(o-ethylphenyl) Phenylphosphonates in House Flies
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Bis(4-chloro-2-ethylphenyl) phenylphosphonate was metabolically transformed into the corresponding cyclic ester, i.e., 6-chloro-4-methyl-2-phenyl-4H-1,3,2-benzodioxaphosphorin 2-oxide, in houseflies in vivo.In a p-unsubstituted analog, hydroxylation at the para-position of an ester linkage occurred preferably to alpha-hydroxylation with subsequent cyclization.The cyclization was diastereomerically selective, giving predominantly the cis ester.The biological activities of synthesized and related cyclic esters were similar to but weaker than saligenin cyclic phosphorus esters lacking a methyl group at the 4-position.
- Wu, Shao-Yong,Ito, Shigekazu,Eto, Morifusa
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p. 2935 - 2942
(2007/10/02)
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- SELECTIVE REDUCTION OF KETONES WITH SODIUMBOROHYDRIDE-ACETIC ACID
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Aliphatic ketones, and aromatic ketones having o-hydroxy or o-amino substituents are reduced rapidly to the alcohols by NaBH4 and acetic acid; other types of ketones react much more slowly.
- Nieminen, Tuula, E. A.,Hase, Tapio A.
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p. 4725 - 4728
(2007/10/02)
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- FACILE ALKYLATION OF o-HYDROXYARYLALDEHYDES AND α-FORMYLKETONES WITH TRIALKYLBORANES
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Trialkylboranes readily undergo alkylation reactions with o-hydroxyarylaldehydes and α-formylketones via the dialkylboryl complexes.
- Okada, Keiji,Hosoda, Yasushi,Oda, Masaji
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p. 6213 - 6216
(2007/10/02)
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- Intramolecular Proton Transfer in Photohydration Reactions
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The photohydration by intramolecular proton transfer of compounds 1-12 has been studied.The non-nitro-substituted o-hydroxystyrenes photohydrate cleanly via the Markovnikov addition of water to afford the 1-arylethanols.The nitro-substituted o-hydroxystyrenes showed no dependence of product quantum yield with change in pH.The products isolated and identified in this case were the corresponding 2-(2-hydroxyphenyl)ethanols.Compounds with α substituents showed evidence of an increased interaction between the hydroxyl group and the ? orbitals of the vinyl moiety.The absolute quantum yields for 1 and 9 were estimated and used to calculate the effective molarities, EM = 1E-2 and 2.6, respectively.
- Kalanderopoulos, Peter,Yates, Keith
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p. 6290 - 6295
(2007/10/02)
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- DEOXYGENATION OF ALDEHYDES AND KETONES WITH SODIUM CYANOBOROHYDRIDE
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Treatment of hydroxy-substituted aromatic aldehydes and ketones with sodium cyanoborohydride yields the corresponding methylene compounds under conditions which favor intermediate carbonium ion formation.
- Elliger, Carl A.
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p. 1315 - 1324
(2007/10/02)
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