- Catalytic tandem oxy-palladation and vinylation
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Intramolecular oxy-palladation of hydroxy-alkenes leads to organo-Pd(II) intermediates which can be trapped by alkenes in chain extension by vinyl substitution; catalysis is efficient using a reoxidation system but the process is limited to substrates which cannot undergo β-hydride elimination from the organo-Pd(II) intermediate.
- Semmelhack,Epa
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- A MEERWEIN-PONNDORF-VERLEY TYPE REDUCTION OF α,β UNSATURATED KETONES TO ALLYLIC ALCOHOLS CATALYZED BY MgO
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Allylic alcohols are obtained with an unprecedented simple method by chemoselective hydrogen transfer reduction of α,β unsaturated ketones catalyzed by MgO.
- Kaspar, J.,Trovarelli, A.,Lenarda, M.,Graziani, M.
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- Catalyst activation by loss of cyclopentadienyl ligands in hydrogen transfer catalysis with Cp*IrIII complexes
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The activity of the two related complexes [Cp*Ir(IMe) 2X]BF4 (X = Cl (1), H (2)) in transfer hydrogenation from isopropyl alcohol to acetophenone was investigated. The results suggest that the commonly accepted monohydride mechanism for transfer hydrogenation mediated by cyclopentadienyl iridium species does not apply to chloride 1. We have found evidence that, although the two monodentate NHC ligands are retained in the coordination sphere, the Cp* ligand is completely released under mild conditions in a precatalytic activation step. Synthesis of modified versions of the initial precatalyst 1 with different cyclopentadienyl and NHC ligands demonstrated that increasing the steric pressure around the iridium center facilitates precatalyst activation and thus enhances the catalytic performance. Study of five new iridium(III) complexes bearing mono- or diphosphines helped us monitor Cp* ligand loss under mild conditions. An unusual P-C bond cleavage was also noted in a 1,2-bis(dimethylphosphino)methane (dmpm) ligand. On the basis of these findings, a novel catalyst activation mechanism is proposed for [(η5-C5R5)Ir] transfer hydrogenation based on the lability of the cyclopentadienyl ligand.
- Campos, Jesus,Hintermair, Ulrich,Brewster, Timothy P.,Takase, Michael K.,Crabtree, Robert H.
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- The conversion of 4-oxa-5-hexenyllithiums to 4-alken-1-ols: A novel [1,4]-wittig rearrangement
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4-Oxa-5-hexenyllithiums (2), which may be prepared from the corresponding 3-iodoalkyl vinyl ethers (1) by low-temperature lithium - iodine exchange, rearrange in high yield to 4-alken-1-ols (4) when warmed to room temperature. This transformation, which constitutes a [1,4]-Wittig rearrangement, is mediated by 5-exo-trig closure of 2 to a (2-tetrahydrofuranyl)methyllithium (3) followed by spontaneous ring opening to give 4.
- Bailey, William F.,Zarcone, Lyn M. J.
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- Photopolymerization of Plasticizer in Ion-Sensitive Membranes on Solid-State Sensors
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Poyl(vinyl chloride) membranes containing the K+ ionophore valinomycin and plasticized with dihexenyl adipate (DHA) can be photopolymerized in the presence of a radical initiator.Photolysis times of 30 min result in ca. 1.5percent reaction of DHA in the presence of O2 and 8percent reaction in its absence, while 90 min is required for 7percent reaction with O2 present.Photolysis for 30 min in air results in a 3- to 5-fold increase in lifetime for membranes coated on solid-state Si sensors, despite the low extent reaction of DHA.The slope of 57.5 mV, and selectivity coefficient for K+ over Na+ of 8 X 10-5, are similar to dioctyl adipate plasiticized K+ membranes.Photolysis for 30min in the absence of O2 results in 3-fold increase in lifetime of membrane-coated Si sensors, but the success rate of electrode preparation is only 50percent.The probability that polymerization and interfacially induced stresses are a factor in membrane degradation is discussed, as is the relevance to ion-sensitive field effect transistors.
- Harrison, D. Jed,Teclemariam, Alem,Cunningham, Linda L.
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- A Nazarov-Ene Tandem Reaction for the Stereoselective Construction of Spiro Compounds
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The different reactivity of trienones under Lewis and Br?nsted acids catalysis was investigated, resulting in distinct cyclization products and carbon backbones that originated either from a conjugate Prins cyclization or an interrupted Nazarov cyclizatio
- Etling, Christoph,Tedesco, Giada,Kalesse, Markus
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supporting information
p. 9257 - 9262
(2021/06/01)
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- Methylene-Linked Bis-NHC Half-Sandwich Ruthenium Complexes: Binding of Small Molecules and Catalysis toward Ketone Transfer Hydrogenation
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The complex [Cp*RuCl(COD)] reacts with LH2Cl2 (L = bis(3-methylimidazol-2-ylidene)) and LiBun in tetrahydrofuran at 65 °C furnishing the bis-carbene derivative [Cp*RuCl(L)] (2). This compound reacts with NaBPh4 in MeOH under dinitrogen to yield the labile dinitrogen-bridged complex [{Cp*Ru(L)}2(μ-N2)][BPh4]2 (4). The dinitrogen ligand in 4 is readily replaced by a series of donor molecules leading to the corresponding cationic complexes [Cp*Ru(X)(L)][BPh4] (X = MeCN 3, H2 6, C2H4 8a, CH2CHCOOMe 8b, CHPh 9). Attempts to recrystallize 4 from MeNO2/EtOH solutions led to the isolation of the nitrosyl derivative [Cp*Ru(NO)(L)][BPh4]2 (5), which was structurally characterized. The allenylidene complex [Cp*Ru═C═C═CPh2(L)][BPh4] (10) was also obtained, and it was prepared by reaction of 2 with HCCC(OH)Ph2 and NaBPh4 in MeOH at 60 °C. Complexes 3, 4, and 6 are efficient catalyst precursors for the transfer hydrogenation of a broad range of ketones. The dihydrogen complex 6 has proven particularly effective, reaching TOF values up to 455 h-1 at catalyst loadings of 0.1% mol, with a high functional group tolerance on the reduction of a broad scope of aryl and aliphatic ketones to yield the corresponding alcohols.
- Botubol-Ares, José Manuel,Cordón-Ouahhabi, Safa,Moutaoukil, Zakaria,Collado, Isidro G.,Jiménez-Tenorio, Manuel,Puerta, M. Carmen,Valerga, Pedro
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supporting information
p. 792 - 803
(2021/04/06)
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- Enantiopure 2,9-Dideuterodecane – Preparation and Proof of Enantiopurity
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(R,R)- and (S,S)-(2,9-2H2)-n-Decane were prepared regio- and stereospecifically in 25–26 % yield over five steps from commercially available enantiopure (R)- and (S)-propylene oxide, respectively. The synthetic procedure involved nucleophilic displacement of (R)- and (S)-4-toluenesulfonic acid 1-methyl-4-pentenyl ester with LiAlD4 to furnish the respective (5-2H)-1-hexenes. Subsequent olefin metathesis and reduction of the double bond furnished the title compounds. The optical purity of (R,R)- and (S,S)-(2,9-2H2)-n-decane could not be determined by chromatography or polarimetry. Therefore, (R,R)- and (R,S)-(5-2H)-3-hydroxy-2-hexanone were prepared from their respective hexenes by Wacker oxidation, followed by enantioselective α-hydroxylation. The enantiopurity could then be determined by NMR spectroscopy because the stereospecifically deuterated hydroxyketones showed separated signals for the subterminal carbon atom (C-5) in the 13C NMR spectrum.
- Christoffers, Jens,Eru?ar, Gülsera,Fsadni, Miriam H.,Golding, Bernard T.,Mitschke, Nico,Roberts, Amy R.,Sadeghi, Majid M.,Wilkes, Heinz
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p. 3854 - 3863
(2021/08/24)
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- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Photoinduced Palladium-Catalyzed Dicarbofunctionalization of Terminal Alkynes
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Herein, a conceptually distinct approach was developed that allowed for the dicarbofunctionalization of alkynes at room temperature using simple, bench-stable alkyl iodides and a second molecule of alkyne as coupling partner. Specifically, the photochemical activation of palladium complexes enabled this strategic dicarbofunctionalization via addition of alkyl radicals from secondary and tertiary alkyl iodides and formation of an intermediate palladium vinyl complex that could undergo subsequent Sonogashira reaction with a second alkyne molecule. This alkylation–alkynylation sequence allowed the one-step synthesis of 1,3-enynes including heteroarenes and biologically active compounds with high efficiency without exogenous photosensitizers or oxidants and now opens up pathways towards cascade reactions via photochemical palladium catalysis.
- Yang, Zhen,Koenigs, Rene M.
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supporting information
p. 3694 - 3699
(2021/02/01)
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- Complex Carbocyclic Skeletons from Aryl Ketones through a Three-Photon Cascade Reaction
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Starting from readily available 7-substituted 1-indanones, products with a tetracyclo[5.3.1.01,704,11]undec-2-ene skeleton were obtained upon irradiation at λ=350 nm (eight examples, 49–67 % yield). The assembly of the structurally complex carbon framework proceeds in a three-photon process comprising an ortho photocycloaddition, a disrotatory [4π] photocyclization, and a di-π-methane rearrangement. The flat aromatic core of the starting material is converted into a functionalized polycyclic hydrocarbon with exit vectors in three dimensions. Ring opening reactions at the central cyclopropane ring were explored, which enable the preparation of tricyclo[5.3.1.04,11]undec-2-enes and of tricyclo[6.2.1.01,5]undecanes.
- Bach, Thorsten,Jandl, Christian,N?sborg, Line,Zech, Andreas
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supporting information
p. 5656 - 5659
(2020/02/11)
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- Acetate Acetylacetonate Ampy Ruthenium(II) Complexes as Efficient Catalysts for Ketone Transfer Hydrogenation
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The mixed acetate acetylacetonate (acac) ruthenium(II) phosphine complexes Ru(OAc)(acac)P2 [P2=(PPh3)2, Ph2P(CH2)4PPh2 (dppb)] were prepared by protonation of Ru(OAc)2(PPh3)2 with acetylacetone in dichloromethane. Reaction of the dppb derivative with 2-(aminomethyl)pyridine (ampy) affords the complex Ru(OAc)(acac)(ampy)(dppb), which converts to [Ru(acac)(ampy)(dppb)](OAc) in toluene at 90 °C. In the former derivative the ampy ligand is monodentate and coordinates through the NH2-moiety. The isolated acac complexes are active catalysts for the transfer hydrogenation of ketones with loadings as low as 0.01 mol%, the ampy having a strong accelerating effect. Several aromatic and aliphatic ketone substrates are converted to their corresponding alcohols, and different electronic influences through substituents on acetophenone are tolerated.
- Hey, Daniela A.,Sauer, Michael J.,Fischer, Pauline J.,Esslinger, Eva-Maria H. J.,Kühn, Fritz E.,Baratta, Walter
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p. 3537 - 3544
(2020/06/01)
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- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
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A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 14286 - 14294
(2020/09/15)
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- Base-free transfer hydrogenation of aryl-ketones, alkyl-ketones and alkenones catalyzed by an IrIIICp* complex bearing a triazenide ligand functionalized with pyrazole
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An IrIIICp* complex (2) bearing a triazenide ligand functionalized with pyrazole was synthesized and fully characterized by spectroscopic methods and the structure confirmed by X-ray diffraction studies. The catalytic activity of 2 and the control complex 3, which lacks of pyrazole in its structure, was evaluated in the reduction of aryl-ketones, alkyl-ketones, α,β-unsaturated and γ,δ-unsaturated ketones. The catalytic system, using either 2 or 3, exhibited good to excellent selectivity when tested with ketones and alkenones at 90 °C in 2-propanol as hydrogen source under base-free conditions. Reactivity of 2 in 2-propanol and NaH gave a neutral metal hydride (4) while in the absence of base gave two major cationic hydrides species (5 and 6).
- Medrano-Castillo, Layla J.,Collazo-Flores, Miguel á.,Camarena-Díaz, Juan P.,Correa-Ayala, Erick,Chávez, Daniel,Grotjahn, Douglas B.,Rheingold, Arnold L.,Miranda-Soto, Valentín,Parra-Hake, Miguel
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- Silica-Supported MnII Sites as Efficient Catalysts for Carbonyl Hydroboration, Hydrosilylation, and Transesterification
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Manganese, the third most abundant transition-metal element after iron and titanium, has recently been demonstrated to be an effective homogeneous catalyst in numerous reactions. Herein, the preparation of silica-supported MnII sites is reported using Surface Organometallic Chemistry (SOMC), combined with tailored thermolytic molecular precursors approach based on Mn2[OSi(OtBu)3]4 and Mn{N(SiMe3)2}2?THF. These supported MnII sites, free of organic ligands, efficiently catalyze numerous reactions: hydroboration and hydrosilylation of ketones and aldehydes as well as the transesterification of industrially relevant substrates.
- Ghaffari, Behnaz,Mendes-Burak, Jorge,Chan, Ka Wing,Copéret, Christophe
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supporting information
p. 13869 - 13873
(2019/11/11)
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- Synthesis of Tetrahydroisoquinolines through an Iron-Catalyzed Cascade: Tandem Alcohol Substitution and Hydroamination
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Rapid assembly of saturated nitrogen heterocycles - the synthetically more challenging variants of their aromatic relatives - can expedite the synthesis of biologically relevant molecules. Starting from a benzylic alcohol tethered to an unactivated alkene, an iron-catalyzed tandem alcohol substitution and hydroamination provides access to tetrahydroisoquinolines in a single synthetic step. Using a mild iron-based catalyst, the combination of these operations forms two carbon-nitrogen bonds and provides a unique annulation strategy to access this valuable core.
- Marcyk, Paul T.,Cook, Silas P.
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supporting information
p. 6741 - 6744
(2019/09/07)
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- Transfer hydrogenation of ketones catalyzed by a trinuclear Ni(II) complex of a Schiff base functionalized N-heterocyclic carbene ligand
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A new Schiff base-functionalized N-heterocyclic carbene ligand precursor 3-benzyl-1-[2-((2-hydroxy-benzylidene)-amino]-ethyl-3H-imidazol-1-ium bromide (3), and its trinuclear Ni(II) complex [LNiL-Ni-LNiL].2Br (4) where L = 2-[2-(3-benzylimidazol-1-yl) ethyliminomethyl]phenol, were synthesized via the solventless and free carbene routes respectively. Both compounds were characterized by spectroscopic and X-ray diffraction techniques. Single crystal XRD analysis of 4 showed that it is composed of a central square planar Ni(II) ion symmetrically linked to two distorted square planar Ni(II) ions via two bridging ligands. The central Ni(II) ion is only bound to the Schiff base moieties of the bridging ligands via the phenolate oxygen donor (O1) and imine nitrogen donor (N1) atoms in a trans [N^O^(Ni2+)^N^O] mode, whilst the carbene moieties of each bridging ligand and a tridentate L are coordinated in a distorted square planar CNHC-(Ni2+)^N^O^CNHC mode to stabilise each of the terminal Ni(II) ions. Complex 4 showed significant activity as a catalyst in the transfer hydrogenation of a range of aliphatic and aromatic ketones, at a catalyst concentration of 0.1 mol%. An excellent conversion up to 100% was achieved for aromatic ketones after 4 h.
- Abubakar, Samaila,Ibrahim, Halliru,Bala, Muhammad D.
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p. 276 - 282
(2018/10/02)
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- Rh(III)Cp? and Ir(III)Cp? Complexes of 1-[(4-Methyl)phenyl]-3-[(2-methyl-4′-R)imidazol-1-yl]triazenide (R = t-Bu or H): Synthesis, Structure, and Catalytic Activity
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A series of iridium and rhodium complexes have been synthesized using as ligand a triazenide monofunctionalized with an imidazole substituent. Steric hindrance at the imidazole moiety induced differences in the coordination modes as well in the catalytic behavior of complexes 4-7. Complexes 4-7 were tested in the transfer hydrogenation of acetophenone and 5-alken-2-ones. The hydrogenation of either the double bond or the carbonyl group in 5-alken-2-ones, showed to be selective in the presence of 6, 7, and 10 and has a dependence on the presence or absence of base. Control experiments point out that the imidazole moiety in the structure of complexes 4-7 speeds-up the catalysis.
- Camarena-Diáz, Juan P.,Iglesias, Ana L.,Chávez, Daniel,Aguirre, Gerardo,Grotjahn, Douglas B.,Rheingold, Arnold L.,Parra-Hake, Miguel,Miranda-Soto, Valentín
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p. 844 - 851
(2019/02/19)
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- Flat and Efficient H CNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction
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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1-3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2]n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1-3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5-7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9-11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf4] (12). The dicarbonyl derivatives 1-4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5-12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000-100000 and TOF up to 100000 h-1). Compounds 1-3, with PCy3, and 6 and 8-10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h-1, respectively). The derivatives 1-3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000-10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,P?thig, Alexander,Zhang, Shuanming,Zuccaccia, Daniele,Baratta, Walter
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p. 1127 - 1142
(2019/03/14)
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- Ring closing metathesis and metal-catalyzed cyclopropanation for the preparation of sultone derivatives
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Ring closing metathesis (RCM) using Grubbs catalyst 2nd generation as a catalyst was applied to prepare series of novel unsaturated sultones with high yields. Many attempts, were applied for the cyclopropanation of the allylic sultones by Simmon-smith cyclopropanation using diethyl zinc/diiodomethane or Zn-Cu/diiodomethane but in each case the corresponding cyclic adduct was not formed. A novel palladium or preferably rhodium-catalyzed cyclopropanation of unsaturated sultones with ethyl diazoacetate was achieved by the transition metal-catalyzed transfer of a CH-CO2Et unit. The reaction was applied by a portion-wise addition of ethyl diazoacetate over 6h to a mixture of the sultones and palladium(II) acetate or rhodium(II) acetate dimer under low temperature (0-20 o C). The desired products of the cyclopropanation were achieved in each case, as a single diastereomer with 33- 37% yield in the allylic sultones and 10% for vinylic sultone.
- Ali, Korany A.,Metz, Peter
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- Cobalt(II) and (I) Complexes of Diphosphine-Ketone Ligands: Catalytic Activity in Hydrosilylation Reactions
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The hydrosilylation of unsaturated compounds homogeneously catalyzed by cobalt complexes has gained considerable attention in the last years, aiming at substituting precious metal-based catalysts. In this study, the catalytic activity of well-characterized CoII and CoI complexes of the pToldpbp ligand is demonstrated in the hydrosilylation of 1-octene with phenylsilane. The CoI complex is the better precatalyst for the mentioned reaction under mild conditions, at 1 mol-% catalyst, 1 h, room temperature, and without solvent, yielding 84 % of octylphenylsilane. Investigation of the substrate scope shows lower performance of the catalyst in styrene hydrosilylation, but excellent results with allylbenzene (84 %) and acetophenone (> 99 %). This catalytic study contributes to the field of cobalt-catalyzed hydrosilylation reactions and shows the first example of catalysis employing the dpbp ligand in combination with a base metal.
- Verhoeven, Dide G. A.,Kwakernaak, Joost,van Wiggen, Maxime A. C.,Lutz, Martin,Moret, Marc-Etienne
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supporting information
p. 660 - 667
(2019/02/05)
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- CREATINE PRODRUGS, COMPOSITIONS AND METHODS OF USE THEREOF
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The present disclosure provides creatine prodrug analogs and their compositions useful for the treatment of creatine deficiencies.
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Paragraph 00581-00582
(2019/06/17)
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- Constructing reactive Fe and Co complexes from isolated picolyl-functionalized N-heterocyclic carbenes
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We report the isolation of free picolyl-functionalized N-heterocyclic carbenes (NHCs), which serve as versatile precursors to access low coordinate iron and cobalt complexes. The reactivities of these new iron and cobalt complexes towards catalytic hydrosilylation of ketones have also been explored. For example, low loadings (0.05-1 mol%) of a four-coordinate iron complex bearing two deprotonated picolyl-NHC ligands can effect the fast catalytic reduction of ketones using the inexpensive industrial byproduct polymethylhydrosiloxane (PMHS) as the reductant at ambient temperature.
- Liang, Qiuming,Liu, Nina Jiabao,Song, Datong
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supporting information
p. 9889 - 9896
(2018/08/06)
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- Switchable Chemoselective Transfer Hydrogenations of Unsaturated Carbonyls Using Copper(I) N-Donor Thiolate Clusters
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Unsaturated alcohols and saturated carbonyls are important chemical, pharmaceutical, and biochemical intermediates. We herein report an efficient transfer hydrogenation protocol in which conversion of unsaturated carbonyl compounds to either unsaturated alcohols or saturated carbonyls was catalyzed by Cu(I) N-donor thiolate clusters along with changing hydrogen source (isopropanol or butanol) and base (NaOH or K2CO3). Mechanistic studies supported by DFT transition state modeling indicate that such a chemoselectivity can be explained by the relative concentrations of Cu(I) monohydride and protonated Cu(I) hydride complexes in each catalytic system.
- Zhang, Meng-Juan,Tan, Da-Wei,Li, Hong-Xi,Young, David James,Wang, Hui-Fang,Li, Hai-Yan,Lang, Jian-Ping
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p. 1204 - 1215
(2018/02/09)
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- Selective Isomerization of Terminal Alkenes to (Z)-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex
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Positional and stereochemical selectivity in the isomerization of terminal alkenes to internal alkenes is observed using the cis-Mo(CO)4(PPh3)2 precatalyst. A p-toluenesulfonic acid (TsOH) cocatalyst is essential for catalyst activity. Various functionalized terminal alkenes have been converted to the corresponding 2-alkenes, generally favoring the Z isomer with selectivity as high as 8:1 Z:E at high conversion. Interrogation of the catalyst initiation mechanism by 31P NMR reveals that cis-Mo(CO)4(PPh3)2 reacts with TsOH at elevated temperatures to yield a phosphine-ligated Mo hydride (MoH) species. Catalysis may proceed via 2,1-insertion of a terminal alkene into a MoH group and stereoselective β-hydride elimination to yield the (Z)-2-alkene.
- Becica, Joseph,Glaze, Owen D.,Wozniak, Derek I.,Dobereiner, Graham E.
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p. 482 - 490
(2018/02/17)
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- Application of Ni(II) complexes of air stable Schiff base functionalized N-heterocyclic carbene ligands as catalysts for the transfer hydrogenation of aliphatic ketones
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New air stable N-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (2), 2-pyridylmethyl (3)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (2, C^N^O) and tetradentate (3, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested.
- Abubakar, Samaila,Bala, Muhammad D.
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p. 2913 - 2923
(2018/09/27)
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- Cobalt-Catalyzed Stereoselective Synthesis of 2,5- trans-THF Nitrile Derivatives as a Platform for Diversification: Development and Mechanistic Studies
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A straightforward protocol integrating a sustainable approach for the synthesis of new 2,5-trans-THF nitrile derivatives enabling an easy diversification of its side chain scaffolds is described. The reaction tolerated different aromatic and alkyl substit
- Ali, Sajjad,Milanezi, Henrique,Alves, Tania M. F.,Tormena, Cláudio Francisco,Ferreira, Marco A. B.
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p. 7694 - 7713
(2018/06/18)
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- Ruthenium NNN complexes with a 2-hydroxypyridylmethylene fragment for transfer hydrogenation of ketones
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Four NNN tridentate ligands L1–L4 containing 2-methoxypyridylmethene or 2-hydroxypyridylmethene fragment were synthesized and introduced to ruthenium centers. When (HOC5H3NCH2C5H3NC5H7N2) (L2) and (HOC5H3NCH2C5H3NC6H6N3) (L4) reacted with RuCl2(PPh3)3, two ruthenium chloride products Ru(L2)(PPh3)Cl2 (1) and Ru(L4)(PPh3)Cl2 (2) were isolated, respectively. Reactions of (MeOC5H3NCH2C5H3NC5H7N2) (L1) and (MeOC5H3NCH2C5H3NC6H6N3) (L3) with RuCl2(PPh3)3 in the presence of NH4PF6 generated two dicationic complexes [Ru(L1)2][PF6]2 (3) and [Ru(L3)2][PF6]2 (4), respectively. Complex 1 reacted with CO to afford product [Ru(L2)(PPh3)(CO)Cl][Cl]. The catalytic activity for transfer hydrogenation of ketones was investigated. Complex 1 showed the highest activity, with a turnover frequency value of 1.44?×?103?h?1 for acetophenone, while complexes 3 and 4 were not active.
- Shi, Jing,Shang, Shu,Hu, Bowen,Chen, Dafa
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- Bis(silylenyl)-substituted ferrocene-stabilized η6-arene iron(0) complexes: Synthesis, structure and catalytic application
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Reaction of FeX2(thf)n (X = Cl n = 1.5, Br n = 2) with the chelating 1,1′-bis(silylenyl)-substituted ferrocene ligand SiFcSiA (Fc = ferrocendiyl, Si = PhC(NtBu)2Si:) furnishes the corresponding dihalido Fe(ii) complexes [(SiFcSi)FeX2] (X = Cl, 1 and X = Br, 2) in high yields. Reduction of the latter with an excess of KC8 in the presence of benzene and toluene leads to the unprecedented bis(silylene) stabilized Fe0 complexes [(SiFcSi)Fe-η6(C6H6)] 3 and [(SiFcSi)Fe-η6(C7H8)] 4, respectively. The 57Fe M?ssbauer spectrum of 3 at 13 K exhibits parameters (σ = 0.3676 mm s-1; ΔEQ = 1.334 mm s-1) which are consistent with the presence of a pentacoordinated Fe0 atom in a pseudo trigonal-bipyramidal coordination environment, with two dative Si→Fe bonds and three coordination sites occupied by the η6-coordinated arene ligand. Results from DFT calculations, 57Fe M?ssbauer parameters and the diamagnetic NMR spectra confirm the redox-innocent nature of these ligands and the zero oxidation state of the iron center. The catalytic ability of 3 was investigated with respect to ketone hydrogenation. In all cases, good to excellent yields to the corresponding alcohols were obtained at 50 °C and 50 bar H2 pressure. Electron-donating as well as -withdrawing substituents were tolerated with excellent to good yields. Conversions of bulkier ketones and unactivated aliphatic ketones lead merely to moderate yields. This represents the first example of a silylene-iron metal complex which has been utilized as a highly active precatalyst in the hydrogenation of ketones. The results underline the powerful ability of chelating bis(N-heterocyclic silylene) ligands acting as strong σ-donor ligands in stabilizing a new generation of low-valent, electron-rich transition metal complexes for catalytic transformations.
- Luecke, Marcel-Philip,Porwal, Digvijay,Kostenko, Arseni,Zhou, Yu-Peng,Yao, Shenglai,Keck, Matthias,Limberg, Christian,Oestreich, Martin,Driess, Matthias
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supporting information
p. 16412 - 16418
(2017/12/15)
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- Hepatitis C virus inhibitors
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Hepatitis C virus inhibitors having the general formula (I) are disclosed. Compositions comprising the compounds and methods for using the compounds to inhibit HCV are also disclosed.
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Page/Page column 61; 62
(2017/05/31)
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- A Manganese Pre-Catalyst: Mild Reduction of Amides, Ketones, Aldehydes, and Esters
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A new (N-phosphinoamidinate)manganese complex is shown to be a useful pre-catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn-catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.
- Kelly, Colin M.,McDonald, Robert,Sydora, Orson L.,Stradiotto, Mark,Turculet, Laura
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supporting information
p. 15901 - 15904
(2017/12/13)
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- Synthesis and reactivity of bis(protic N-heterocyclic carbene)iridium(III) complexes
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A nonfunctionalized bis(imidazole) ligand precursor has been directly metalated using IrCp?(OAc)2, leading to a mixture of bis(protic N-heterocyclic carbene) (bisPNHC) complexes (2a,b). Treatment of 2a,b with HCl gas in CH2Cl2 gave a bisPNHC complex (3a), which has been transformed into a hydride bisPNHC complex. Complex 3a underwent ligand and counterion exchange reactions to afford acetonitrile and ethylamine bisPNHC complexes (5 and 6). Furthermore, these bisPNHC complexes have been tested as catalysts in transfer hydrogenation reactions of ketones and unsaturated ketones.
- Gomez-Lopez, Jessica L.,Chávez, Daniel,Parra-Hake, Miguel,Royappa, Arun T.,Rheingold, Arnold L.,Grotjahn, Douglas B.,Miranda-Soto, Valentín
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p. 3148 - 3153
(2016/10/09)
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- Highly Active and Selective Manganese C=O Bond Hydrogenation Catalysts: The Importance of the Multidentate Ligand, the Ancillary Ligands, and the Oxidation State
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The replacement of expensive noble metals by earth-abundant transition metals is a central topic in catalysis. Herein, we introduce a highly active and selective homogeneous manganese-based C=O bond hydrogenation catalyst. Our catalyst has a broad substrate scope, it is able to hydrogenate aryl–alkyl, diaryl, dialkyl, and cycloalkyl ketones as well as aldehydes. A very good functional group tolerance including the quantitative and selective hydrogenation of a ketone in the presence of a non-shielded olefin is observed. In Mn hydrogenation catalysis, the combination of the multidentate ligand, the oxidation state of the metal, and the choice of the right ancillary ligand is crucial for high activity. This observation emphasizes an advantage and the importance of homogeneous catalysts in 3d-metal catalysis. For coordination compounds, fine-tuning of a complex coordination environment is easily accomplished in comparison to enzyme and/or heterogeneous catalysts.
- Kallmeier, Fabian,Irrgang, Torsten,Dietel, Thomas,Kempe, Rhett
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supporting information
p. 11806 - 11809
(2016/11/16)
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- Vapour phase transfer hydrogenation of α,β-unsaturated carbonyl compounds. Thermodynamic and experimental studies
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This paper presents the first systematic thermodynamic study of the vapour phase transfer hydrogenation of α,β-unsaturated carbonyl compounds at temperatures: 423.15-723.15 K. Calculations were made for four compounds, namely: acrolein, α-methylacrolein, β-methylacrolein and methyl vinyl ketone. The Gibbs free energies and equilibrium mole fractions (EMFs) were calculated for transfer hydrogenation with ethanol and 2-propanol as hydrogen donors. It was noted that for transfer hydrogenation and hydrogenation with hydrogen the formation of the unsaturated alcohol (UOL) is the least thermodynamically favoured reaction and that saturated alcohol (SOL) and saturated aldehyde or ketone (SAL or SON) are the main products. A set of eight carbonyl compounds have been transfer hydrogenated with ethanol and 2-propanol in the presence of MgO as the catalyst. The main conclusions are that: (a) the reduction of a carbonyl group into a carbinol group occurs with a very high selectivity, (b) for almost all carbonyl compounds, except acrolein, the reactivity of 2-propanol highly exceeded that shown by ethanol and (c) the high chemoselectivity of transfer hydrogenation of acrolein with alcohols resulted from the kinetic control caused by the presence of magnesium oxide.
- Gliński, Marek,Ulkowska, Urszula
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p. 131 - 140
(2015/12/18)
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- Dinuclear Di(N-heterocyclic carbene) iridium(III) complexes as catalysts in transfer hydrogenation
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Two novel di(N-heterocyclic carbene) complexes of formula (μ-PyrIm-CH2-ImPyr)[IrCp?Cl]2(PF6)2 (1) and μ-MeIm-CH2(p-C6H2)CH2-ImMe[IrCp? Cl]2 (2) (Im = imidazol-2-ylidene) have been synthesised by transmetallation of the dicarbene ligand from the corresponding dicarbene silver complex, using [IrCp?(μ-Cl)Cl]2 as an iridium precursor. The structure of complex 2 has been determined by X-ray diffraction and is characterized by a double ortho-metallation of the p-xylylene bridge between the carbene units. Both complexes show good activity in the transfer hydrogenation of ketones to alcohols in 2-propanol. Dinuclear iridium(III) complexes bearing a bridging di(NHC) ligand have been synthesised and tested as catalysts in transfer hydrogenation reactions.
- Volpe, Andrea,Baldino, Salvatore,Tubaro, Cristina,Baratta, Walter,Basato, Marino,Graiff, Claudia
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p. 247 - 251
(2016/01/20)
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- Preparation of Pincer 4-Functionalized 2-Aminomethylbenzo[h]quinoline Ruthenium Catalysts for Ketone Reduction
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Reaction of 1-naphthylamine with ethyl benzoylacetate gives the corresponding benzoyl acetamide derivative 1, which undergoes cyclization to 4-phenylbenzo[h]quinolin-2(1H)-one (2) in the presence of H2SO4. Bromination with POBr3, followed by reaction with n-BuLi and DMF, gives 4-phenylbenzo[h]quinoline-2-carbaldehyde (4), which is converted to the corresponding oxime hydrochloride 5 with NH2OH·HCl. Hydrogenation of 5 catalyzed by 10% Pd/C (type 338) leads to 4-phenyl-2-aminomethylbenzo[h]quinoline hydrochloride (HCNNPh·HCl, 6) isolated in high yield. Similarly, the 4-methyl-2-aminomethylbenzo[h]quinoline derivative (HCNNMe·HCl, 12) is prepared starting from 1-naphthylamine and 2,2,6-trimethyl-4H-1,3-dioxin-4-one, following the route for 6. Reaction of RuCl2(PPh3)3 with a diphosphine (PP), the HCl salt 6, and NEt3 in 2-propanol leads to the pincer complexes RuCl(CNNPh)(PP) (PP = Ph2P(CH2)3PPh2, 13; Ph2P(CH2)4PPh2, 14; 1,1′-bis(diphenylphosphino)ferrocene, 15). The methyl derivatives RuCl(CNNMe)(PP) (PP = Ph2P(CH2)3PPh2, 16; Ph2P(CH2)4PPh2, 17; 1,1′-bis(diphenylphosphino)ferrocene, 18) are obtained in a similar way using 12 in place of 6. Treatment of [RuCl2(p-cymene)]2 with rac-BINAP, 6, and NEt3 affords RuCl(CNNPh)(BINAP) (19), isolated as a mixture of two diastereoisomers (3:4 molar ratio). The chiral RuCl(CNNPh)[(S,R)-JOSIPHOS] (20) is obtained as a single isomer from [RuCl2(p-cymene)]2, (S,R)-JOSIPHOS, and 6. Complexes 13-20 efficiently catalyze the transfer hydrogenation of acetophenone in 2-propanol at reflux in the presence of NaOiPr (2 mol%) with S/C = 5000-20-000 and at high rate (TOF up to 6.7 × 103 min-1). With complexes 13, 15, 17, and 18 several ketones of commercial-grade purity have been reduced to alcohols, including the bulky RCO(tBu) (R = Me, Ph) substrates. With 20 acetophenone is reduced to (S)-1-phenylethanol with 85% ee. The pincer complexes 13-15 and 18 are also found highly active in the hydrogenation of ketones at 40 °C with an S/C = 10-000, under 5 bar of dihydrogen in methanol and in the presence of 2 mol % of a base (NaOH, KOH, NaOMe).
- Facchetti, Sarah,Jurcik, Vaclav,Baldino, Salvatore,Giboulot, Steven,Nedden, Hans Günter,Zanotti-Gerosa, Antonio,Blackaby, Andrew,Bryan, Richard,Boogaard, Adrian,McLaren, David B.,Moya, Eduardo,Reynolds, Steven,Sandham, Karl S.,Martinuzzi, Paolo,Baratta, Walter
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p. 277 - 287
(2016/02/05)
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- Simple Ligand Modifications with Pendent OH Groups Dramatically Impact the Activity and Selectivity of Ruthenium Catalysts for Transfer Hydrogenation: The Importance of Alkali Metals
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Remarkable differences in selectivity and activity for ruthenium-catalyzed transfer hydrogenation are described that are imparted by pendent OH groups. Kinetic experiments, as well as the study of control complexes devoid of OH groups, reveal that the pendent OH groups serve to orient the ketone substrate through ion pairing with an alkali metal under basic conditions. The deprotonation of the OH groups was found to modulate the electronics at the metal center, providing a more electron rich ruthenium center. The effects of the ion pairing between alkali metals and the pendent alkoxide groups were highlighted by demonstrating chemoselective transfer hydrogenation of ketones in the presence of olefins. The results illustrate that a simple ligand modification (installation of OH groups) imparts dramatic changes to catalysis. Pendent OH groups turn on catalysis through electronic perturbations at the metal site under basic conditions and can also change the mechanism of catalysis, the latter of which can be used to promote chemoselective reductions.
- Moore, Cameron M.,Bark, Byongjoo,Szymczak, Nathaniel K.
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p. 1981 - 1990
(2016/03/15)
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- Optimum bifunctionality in a 2-(2-pyridyl-2-ol)-1,10-phenanthroline based ruthenium complex for transfer hydrogenation of ketones and nitriles: Impact of the number of 2-hydroxypyridine fragments
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Considerable differences in reactivity and selectivity for 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation are described. Bifunctional Ru(ii)-(phenpy-OH) [phenpy-OH: 2-(2-pyridyl-2-ol)-1,10-phenanthroline] complex (2) exhibited excellent catalytic activity in transfer hydrogenation (TH) of ketones and nitriles. Notably, in comparison with all the reported 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation, complex 2 displayed significantly higher activity. Additionally, exploiting the metal-ligand cooperativity in complex 2, chemoselective TH of ketones was achieved and sterically demanding ketones were readily reduced. An outer-sphere mechanism is proposed for this system as exogenous PPh3 has no significant effect on the rate of this reaction. This is a rare example of a highly active bifunctional Ru(ii) catalyst bearing only one 2-HP unit.
- Paul, Bhaskar,Chakrabarti, Kaushik,Kundu, Sabuj
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supporting information
p. 11162 - 11171
(2016/07/16)
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- BENZO[H]QUINOLINE LIGANDS AND COMPLEXES THEREOF
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The present invention provides substituted tridentate benzo[h]quinoline ligands and complexes thereof. The invention also provides the preparation of the ligands and the respective complexes, as well as to processes for using the complexes in catalytic reactions.
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Page/Page column 72-73
(2016/12/22)
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- Hepatitis C virus inhibitors
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Hepatitis C virus inhibitors having the general formula (I) are disclosed. Compositions comprising the compounds and methods for using the compounds to inhibit HCV are also disclosed.
- -
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Page/Page column 506
(2017/01/23)
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- Highly Selective Hydroboration of Alkenes, Ketones and Aldehydes Catalyzed by a Well-Defined Manganese Complex
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Well-defined manganese complexes based on inexpensive, readily available ligands, 2,2′:6′,2′′-terpyridine and its derivatives have been prepared and employed for the selective hydroboration of alkenes, ketones and aldehydes. Highly Markovnikov regioselective hydroboration of styrenes as well as excellent chemoselective hydroboration of ketones over alkenes were achieved, for the first time, by an earth-abundant manganese catalyst.
- Zhang, Guoqi,Zeng, Haisu,Wu, Jing,Yin, Zhiwei,Zheng, Shengping,Fettinger, James C.
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supporting information
p. 14369 - 14372
(2016/11/11)
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- Stereoselective Synthesis of cis-2,5-Disubstituted Pyrrolidines via Copper-Catalyzed Cyclization of Alkenes
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An efficient methodology for the stereoselective synthesis of cis-2,5-disubstituted pyrrolidines using copper catalyst was developed. The corresponding cis-2,5-disubstituted pyrrolidines could be obtained in reasonable yields and with good stereoselectivities in the presence of 4,4′-di-tert-butyl-2,2′-bipyridine as ligand and 1-methyl-2-pyrrolidinone as solvent.
- Cai, Sai-Hu,Da, Bing-Chao,Zhou, Jia-Hui,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 1076 - 1080
(2016/11/25)
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- Ruthenium complexes bearing an unsymmetrical pincer ligand with a 2-hydroxypyridylmethylene fragment: Active catalysts for transfer hydrogenation of ketones
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Five ruthenium(ii) complexes were synthesized, including (HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)Cl2 (3), [(HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)2Cl][PF6] (4) and [(HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)2OH][PF6] (5) bearing an unsymmetrical pincer NNN ligand with a 2-hydroxypyridylmethylene fragment, and [(CH3O-C5H3N-CH2-C5H3N-C5H4N)2Ru][Cl]2 (6) and [(CH3O-C5H3N-CH2-C5H3N-C5H4N)2Ru][PF6]2 (7) containing 2-methoxypyridylmethylene moieties. 4 reacts with H2O at room temperature to give 5 whose crystal structure reveals the existence of intramolecular hydrogen-bonding between its two -OH groups. 3 exhibits high catalytic activity for transfer hydrogenation of ketones.
- Shi, Jing,Hu, Bowen,Gong, Dawei,Shang, Shu,Hou, Guangfeng,Chen, Dafa
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p. 4828 - 4834
(2016/03/19)
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- Total synthesis of two potent anti-inflammatory macrolactones of the oxacyclododecindione type
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An esterification/Friedel-Crafts-cyclization approach permitted the first successful synthetic entry into the oxacyclododecindione subclass of the dihydroxyphenylacetic acid lactone-type natural products. This route allowed the preparation of two highly a
- Tauber, Johannes,Rohr, Markus,Walter, Thorsten,Erkel, Gerhard,Opatz, Till
-
supporting information
p. 7813 - 7821
(2015/07/15)
-
- Synthetic approaches to anti-inflammatory macrolactones of the oxacyclododecindione type
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Abstract Various synthetic approaches to the oxacyclododecindione-type macrolactones, known for their potent anti-inflammatory activity, are presented. These include an attempted carbonylative ring closure, a hydroacylation route, and an approach by ring-
- Tauber, Johannes,Rudolph, Kristina,Rohr, Markus,Erkel, Gerhard,Opatz, Till
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p. 3587 - 3608
(2015/06/08)
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- HEPATITIS C VIRUS INHIBITORS
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Hepatitis C virus inhibitors having the general formula (I) are disclosed. Compositions comprising the compounds and methods for using the compounds to inhibit HCV are also disclosed.
- -
-
-
- HEPATITIS C VIRUS INHIBITORS
-
Hepatitis C virus inhibitors having the general formula (I) are disclosed. Compositions comprising the compounds and methods for using the compounds to inhibit HCV are also disclosed.
- -
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- Well-defined iron catalysts for the acceptorless reversible dehydrogenation-hydrogenation of alcohols and ketones
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Acceptorless dehydrogenation of alcohols, an important organic transformation, was accomplished with well-defined and inexpensive iron-based catalysts supported by a cooperating PNP pincer ligand. Benzylic and aliphatic secondary alcohols were dehydrogenated to the corresponding ketones in good isolated yields upon release of dihydrogen. Primary alcohols were dehydrogenated to esters and lactones, respectively. Mixed primary/secondary diols were oxidized at the secondary alcohol moiety with good chemoselectivity. The mechanism of the reaction was investigated using both experiment and DFT calculations, and the crucial role of metal-ligand cooperativity in the reaction was elucidated. The iron complexes are also excellent catalysts for the hydrogenation of challenging ketone substrates at ambient temperature under mild H2 pressure, the reverse of secondary alcohol dehydrogenation.
- Chakraborty, Sumit,Lagaditis, Paraskevi O.,F?rster, Moritz,Bielinski, Elizabeth A.,Hazari, Nilay,Holthausen, Max C.,Jones, William D.,Schneider, Sven
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p. 3994 - 4003
(2015/01/16)
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- Selective transfer hydrogenation and hydrogenation of ketones using a defined monofunctional (P^N(Bn)^N(Bn)^P)-RuII complex
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A defined (P^N^N^P)-Ru complex possessing tertiary amines within the ligand backbone proved to be highly active both in transfer hydrogenations and hydrogenations of a variety of ketones. As compared to the existing catalytic systems, no bifunctional activation of H2 or of the substrate by the metal center and a secondary amine within the ligand backbone is required to obtain high activities at catalyst loadings of down to 10 ppm. Monofunctional but good: A defined (P N N P)-Ru complex possessing tertiary amines within the ligand backbone proved to be highly active both in transfer hydrogenations and hydrogenations of a variety of ketones (see scheme).
- Hsu, Shih-Fan,Plietker, Bernd
-
supporting information
p. 4242 - 4245
(2014/05/06)
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- Iron(II) complexes containing unsymmetrical P-N-P′ pincer ligands for the catalytic asymmetric hydrogenation of ketones and imines
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After their treatment with LiAlH4 and then alcohol, new iron dicarbonyl complexes mer-trans-[Fe(Br)(CO)2(P-CH=N-P′)][BF 4] (where P-CH=N-P′ = R2PCH2CH=NCH 2CH2PPh2 and R = Cy or iPr or P-CH=N-P′ = (S,S)- Cy2PCH2CH=NCH(Me)CH(Ph)PPh2) are catalysts for the hydrogenation of ketones in THF solvent with added KOtBu at 50 C and 5 atm H2. Complexes with R = Ph are not active. With the enantiopure complex, alcohols are produced with an enantiomeric excess of up to 85% (S) at TOF up to 2000 h-1, TON of up to 5000, for a range of ketones. An activated imine is hydrogenated to the amine in 90% ee at a TOF 20 h-1and TON 99. This is a significant advance in asymmetric pressure hydrogenation using iron. The complexes are prepared in two steps: (1) a one-pot reaction of phosphonium dimers ([cyclo-(PR2CH2CH(OH) -)2][Br]2), KOtBu, FeBr2, and Ph2PCH2CH2NH2 (or (S,S)-Ph 2PCH(Ph)CH(Me)NH2 for the enantiopure complex) in THF under a CO atmosphere to produce the complexes cis- and trans-[Fe(Br) 2(CO)(P-CH=N-P′)]; (2) the reaction of these with AgBF 4 under CO(g) to afford the dicarbonyl complexes in high yield (50-90%). NMR and DFT studies of the process of precatalyst activation show that the dicarbonyl complexes are converted first to hydride-aluminum hydride complexes where the imine of the P-CH=N-P′ ligand is reduced to an amide [P-CH2N-P′]- with aluminum hydrides still bound to the nitrogen. These hydride species react with alcohol to give monohydride amine iron compounds FeH(OR′)(CO)(P-CH2NH-P′), R′ = Me, CMe2Et as well as the iron(0) complex Fe(CO)2(P-CH 2NH-P′) under certain conditions.
- Lagaditis, Paraskevi O.,Sues, Peter E.,Sonnenberg, Jessica F.,Wan, Kai Yang,Lough, Alan J.,Morris, Robert H.
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supporting information
p. 1367 - 1380
(2014/02/14)
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- Hepatitis C Virus Inhibitors
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Hepatitis C virus inhibitors having the general formula (I) are disclosed. Compositions comprising the compounds and methods for using the compounds to inhibit HCV are also disclosed.
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Page/Page column
(2014/05/20)
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- COMPLEX CATALYSTS BASED ON AMINO-PHOSPHINE LIGANDS FOR HYDROGENATION AND DEHYDROGENATION PROCESSES
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The present application discloses novel PWNN and PWNWP metal catalysts for organic chemical syntheses including hydrogenation (reduction) of unsaturated compounds or dehydrogenation of substrates. The range of hydrogenation substrate compounds includes esters, lactones, enals, enones, enolates, oils and fats, resulting in alcohols, enols, diols, and triols as reaction products. The catalysts of current application can be used to catalyze a hydrogenation reaction under solvent free conditions. The present catalysts also allow the hydrogenation to proceed without added base, and it can be used in place of the conventional reduction methods employing hydrides of the main-group elements. Furthermore, the catalysts of the present application can catalyze a dehydrogenation reaction under homogenous and/or acceptorless conditions. As such, the catalysts provided herein can be useful in substantially reducing cost and improving the environmental profile of manufacturing processes for a variety of chemicals.
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Page/Page column 39; 40; 41; 42
(2014/09/29)
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- Alkene isomerisation catalysed by a ruthenium PNN pincer complex
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The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. The catalyst tested positive! A dearomatised ruthenium PNN (2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) pincer complex, [Ru(CO)H(PNN)], was evaluated as an alkene isomerisation catalyst. The isomerisation reaction was greatly accelerated by the addition of alcohols, in particular isopropanol. Isomerisation of terminal to internal alkenes took place at room temperature. A mechanism was proposed based on variable-temperature NMR spectroscopy.
- Perdriau, Sébastien,Chang, Mu-Chieh,Otten, Edwin,Heeres, Hero J.,De Vries, Johannes G.
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supporting information
p. 15434 - 15442
(2016/02/18)
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- (N -Phosphinoamidinate)Iron pre-catalysts for the room temperature hydrosilylation of carbonyl compounds with broad substrate scope at low loadings
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The synthesis and structural characterization of three-coordinate iron(II) and cobalt(II) complexes supported by new N-phosphinoamidinate ligands is reported, along with the successful application of these complexes as precatalysts for the challenging room-temperature hydrosilylation of carbonyl compounds to afford alcohols upon workup. Under the rigorous screening conditions employed (0.015 mol % Fe) for the reduction of acetophenone, the well-defined iron(II) amido precatalyst 2b, featuring bulky N-2,6- diisopropylphenyl and di-tert-butylphosphino moieties within the N-phosphinoamidinate ligand, exhibited exceptional catalytic performance. Further experimentation revealed that the yield achieved in the hydrosilylation of acetophenone employing 2b was unaltered when conducting reactions in the absence of light, in the presence of excess mercury, or under solvent-free conditions. Notably, precatalyst 2b was found to exhibit the broadest substrate scope reported to date for such room-temperature iron-catalyzed carbonyl hydrosilylations en route to alcohols, enabling the chemoselective reduction of structurally diverse aldehydes and ketones, as well as for the first time esters, at remarkably low loadings (0.01-1.0 mol % Fe) and using only 1 equiv of phenylsilane reductant.
- Ruddy, Adam J.,Kelly, Colin M.,Crawford, Sarah M.,Wheaton, Craig A.,Sydora, Orson L.,Small, Brooke L.,Stradiotto, Mark,Turculet, Laura
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supporting information
p. 5581 - 5588
(2013/11/06)
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