- Catalytic enantioselective addition of alkyl grignard reagents to aliphatic aldehydes
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Herein, we report an efficient catalytic system for the enantioselective addition of alkyl Grignard reagents to a broad range of aliphatic aldehydes with good yields and enantioselectivities. Remarkably, the challenging methylmagnesium bromide (MeMgBr) can also be added to a variety of aliphatic aldehydes, providing versatile chiral methyl carbinol units with unprecedented yields and enantioselectivities in a simple one-pot procedure under mild conditions. Copyright
- Fernandez-Mateos, Emilio,Macia, Beatriz,Yus, Miguel
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- Deracemization of secondary alcohols through a concurrent tandem biocatalytic oxidation and reduction
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(Chemical Equation Presented) Breaking the mirror: A purified alcohol dehydrogenase (ADH) for stereoselective reduction and whole cells of a microorganism for enantioselective oxidation operated concurrently to effect the stereoinversion of one enantiomer of a racemic secondary alcohol and provide the optically pure alcohol in >99% yield (see scheme). R,R′ = alkyl.
- Voss, Constance V.,Gruber, Christian C.,Kroutil, Wolfgang
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- Regio- And stereoselective subterminal hydroxylations of n-decane by fungi in a liquid-liquid interface bioreactor (L-L IBR)
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This article may be the first report to describe the excellent regio- and stereoselective subterminal hydroxylations of n-alkane with microorganisms. Approximately 2000 fungal strains were screened for the regioselective hydroxylation of n-decane with a s
- Oda, Shinobu,Isshiki, Kunio,Ohashi, Shinichi
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- Novel Pd/C-catalyzed redox reactions between aliphatic secondary alcohols and ketones under hydrogenation conditions: Application to H-D exchange reaction and the mechanistic study
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A liquid-phase redox system between secondary alcohols and ketones is described. Deuteration of either secondary alcohols or ketones using the Pd/C-H2-D2O system gave a mixture of deuterium-labeled secondary alcohols and ketones. The results indicated that the secondary alcohol was oxidized to the corresponding ketone without oxidants under the hydrogenation conditions and the hydrogenation of the aliphatic ketone to the corresponding secondary alcohol simultaneously proceeded. Detailed mechanistic studies on the redox system as well as the H-D exchange reaction are discussed.
- Esaki, Hiroyoshi,Ohtaki, Rumi,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
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- A biocatalytic one-pot oxidation/reduction sequence for the deracemisation of a sec-alcohol
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Biocatalytic deracemisation via inversion of rac-2-decanol was accomplished by a combined oxidation/reduction sequence using the same 'single' catalyst for both steps. Overall, the (R)-alcohol was inverted to the corresponding (S)-alcohol. Lyophilised cells of various Rhodococci spp. were tested for the unselective oxidation of the racemic sec-alcohol using acetone as the hydrogen acceptor in the first step. For the second step, the stereoselective asymmetric reduction of the corresponding ketone, 2-propanol was employed as the hydrogen donor. Employing lyophilised cells of Rhodococcus sp. CBS 717.73 racemic 2-decanol was transformed to (S)-2-decanol with excellent enantiomeric excess (92% ee) and yield (82% isolated yield) in the combined one-pot oxidation/reduction sequence.
- Voss, Constance V.,Gruber, Christian C.,Kroutil, Wolfgang
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- Borane - THF: New solutions with improved thermal properties and stability
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A new generation of borane-THF solutions stabilized with 0.005 M of 1,2,2,6,6-pentamethylpiperidine or N-isopropyl-N-methyl-tert-butylamine have been developed. These BTHF solutions show superior stability and reactivity at ambient temperatures when compared to BTHF complex unstabilized or stabilized with 0.005 M NaBH4.
- Potyen, Mark,Josyula, Kanth V. B.,Schuck, Mike,Lu, Sean,Gao, Peng,Hewitt, Chris
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- REDUCTION OF ALDEHYDES AND KETONES TO ALCOHOLS WITH HYDROUS ZIRCONIUM OXIDE AND 2-PROPANOL
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Reduction of aldehydes and ketones with 2-propanol was found to proceed efficiently in the presence of hydrous zirconium oxide.The reaction is performed simply and the products are easily isolated in the pure state by filtering off the hydrous zirconium oxide, followed by evaporation of solvents.
- Matsushita, Hajime,Ishiguro, Shigeo,Ichinose, Hiroshi,Izumi, Akira,Mizusaki, Shigenobu
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- Highly enantioselective reduction of ketones by chiral diol-modified lithium aluminum hydride reagents
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Some readily available chiral diols from indene and d-mannitol were investigated as chiral modifiers in lithium aluminum hydride reduction of ketones, and it was discovered that further modification of these reducing reagents by a simple a-amino alcohol resulted in a remarkable increase in optical yield. Among the investigated chiral modifiers, chiral diol 1 gave the highest enantioselectivities.
- Ren, Yunlai,Tian, Xinzhe,Sun, Kunpeng,Xu, Jian,Xu, Xianlun,Lu, Shijie
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- Towards the development of a selective ruthenium-catalyzed hydroformylation of olefins
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The ruthenium-catalyzed hydroformylation of 1- and 2-octene to give preferentially the corresponding linear aldehyde is reported. The catalyst system comprising of Ru3(CO)12 and an imidazole- substituted monophosphine ligand allows for high chemo- and regioselectivity. The hydroformylation proceeds with unprecedented rates for a ruthenium-based catalyst. Copyright
- Fleischer, Ivana,Wu, Lipeng,Profir, Irina,Jackstell, Ralf,Franke, Robert,Beller, Matthias
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- Molybdenum-catalyzed conversion of diols and biomass-derived polyols to alkenes using isopropyl alcohol as reductant and solvent
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Chemical processes capable of reducing the high oxygen content of biomass-derived polyols are in demand in order to produce renewable substitutes for chemicals of fossil origin. Deoxydehydration (DODH) is an attractive reaction that in a single step transforms a vicinal diol into an alkene, but the reaction requires a homogeneous catalyst, a reductant, and a solvent, which are typically expensive, unsustainable, or inefficient. Herein, we present the use of molybdenum(VI)-based compounds, in particular the cheap and commercially available (NH4)6Mo7O24·4H2O, as catalysts for the DODH of vicinal diols in isopropyl alcohol (iPrOH), which serves as both the solvent and reductant. The reaction proceeds at 240-250 °C in a pressurized autoclave, and the alkene yield from simple aliphatic diols can be as high as 77%. The major byproducts are carbonyl compounds - formed by dehydration of the diol - and the alcohols formed by transfer hydrogenation of the carbonyl compounds; the total yield of reduced species (i.e., alkene and alcohols) can be as high as 92%. The DODH of glycerol yields allyl alcohol, which undergoes subsequent Mo-catalyzed deoxygenation to propylene driven by the oxidation of iPrOH; a major byproduct is the homocoupled product 1,5-hexadiene. Further insight in this Mo-catalyzed deoxygenation is gained by an investigation of model compounds: The allylic alcohol 1-hexen-3-ol is deoxygenated to hexene isomers in a yield of 65%, while benzyl alcohol is deoxygenated to toluene in a yield of 93%. The DODH of erythritol yields 39% 2,5-dihydrofuran, while the DODH of the proposed intermediate 1,4-anhydroerythritol yields 75%. The mechanism of the DODH of 1,4-anhydroerythritol was investigated by means of density functional theory (DFT), and the rate-determining step (24.1 kcal/mol) was found to be reduction of a molybdenum(VI) diolate to a molybdenum(IV) diolate.
- Dethlefsen, Johannes R.,Lupp, Daniel,Teshome, Ayele,Nielsen, Lasse B.,Fristrup, Peter
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- Utilising hardly-water soluble substrates as a second phase enables the straightforward synthesis of chiral alcohols
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So far, the alcohol dehydrogenase-catalysed conversion of longer chain aliphatic substrates has been challenging due to their low solubility in aqueous solution. However, by utilising the ketone directly as a second organic phase, the straightforward synthesis of long chain aliphatic chiral alcohols is enabled. The Royal Society of Chemistry.
- Kohlmann, Christina,Robertz, Nora,Leuchs, Susanne,Greiner, Lasse,Na'Amnieh, Shukralla
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- The asymmetric solvomercuration-demercuration of olefins in chiral micellar systems
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The solvomercuration-demercuration of olefins in chiral micelles were investigated. The chiral carbinols can be obtained by asymmetric oxymercuration of prochiral olefins with NaBH4. A satisfactory result was achieved. The highest e.e.% was up to 96%.
- Zhang,Bao,Dong
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- Acceleration effects of phosphine ligands in the nickel catalyzed methylation of aldehydes using trimethylaluminum
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A nickel catalyzed methylation of aldehydes was conducted successfully using trimethylaluminum as an alkylation reagent. In the presence of a phosphine or phosphite ligand, the reaction was considerably accelerated to give the methylation product in good yields.
- Ichiyanagi, Tsuyoshi,Kuniyama, Satoru,Shimizu, Makoto,Fujisawa, Tamotsu
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- Benzo[h]quinoline pincer ruthenium and osmium catalysts for hydrogenation of ketones
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Chiral orthometalated osmium complexes [OsCl(CN′N)(PP)] {PP = (S,R)-Josiphos type diphosphane} based on 2-aminomethylbenzo[h]quinoline ligands (HCN′N) were prepared by reaction of [OsCl2(PPh 3)3] with a Josiphos diphosphane and a HCN′N ligand in the presence of NEt3. Ruthenium and osmium complexes [MX(CN′N)(PP)] {M = Ru, Os; X = Cl, OCH(p-C6H 4F)2; PP = dppb, (S,R)-Josiphos}, in the presence of KOtBu, efficiently catalyze the chemoselective hydrogenation (H2 = 5 atm) of aromatic and aliphatic ketones to secondary alcohols in methanol or methanol/ethanol mixtures, when a S/C ratio of 10000-50000 is used. With use of these chiral phosphanes, alkyl aryl ketones have been reduced with ee values up to 99% and turnover frequencies (TOFs) up to 5.6 × 104 h -1.
- Baratta, Walter,Fanfoni, Lidia,Magnolia, Santo,Siega, Katia,Rigo, Pierluigi
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- Ionic liquid facilitates biocatalytic conversion of hardly water soluble ketones
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Ionic liquids represent a promising alternative to conventional cosolvents as biocompatible solubilisers for biocatalysis. This was shown using water miscible ionic liquids to facilitate the stereoselective reduction of hardly water soluble, aliphatic ketones catalysed by the alcohol dehydrogenase from Lactobacillus brevis. Ten ionic liquids were screened for activity and solubility. Improved storage stabilities besides improved enzyme activities, as well as reduced substrate surplus and product inhibitions were found, while applying the most promising AMMOENG 101 in more detailed investigations. Batch reactions with cofactor regeneration via a glucose dehydrogenase showed increased reaction rates; thus underlining the positive influence of AMMOENG 101. For (R)-3-octanol, (R)-2-nonanol, (R)-2-decanol, and (R)-2-octanol space time yields between 250 and 350 mmol L-1 d -1 were achieved.
- Kohlmann, Christina,Robertz, Nora,Leuchs, Susanne,Dogan, Zuebeyde,Luetz, Stephan,Bitzer, Katrin,Na'Amnieh, Shukrallah,Greiner, Lasse
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- Deep eutectic solvents as H2-sources for Ru(II)-catalyzed transfer hydrogenation of carbonyl compounds under mild conditions
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The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.
- Cavallo, Marzia,Arnodo, Davide,Mannu, Alberto,Blangetti, Marco,Prandi, Cristina,Baratta, Walter,Baldino, Salvatore
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supporting information
(2021/02/22)
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- Primary Alcohols via Nickel Pentacarboxycyclopentadienyl Diamide Catalyzed Hydrosilylation of Terminal Epoxides
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The efficient and regioselective hydrosilylation of epoxides co-catalyzed by a pentacarboxycyclopentadienyl (PCCP) diamide nickel complex and Lewis acid is reported. This method allows for the reductive opening of terminal, monosubstituted epoxides to form unbranched, primary alcohols. A range of substrates including both terminal and nonterminal epoxides are shown to work, and a mechanistic rationale is provided. This work represents the first use of a PCCP derivative as a ligand for transition-metal catalysis.
- Lambert, Tristan H.,Steiniger, Keri A.
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supporting information
p. 8013 - 8017
(2021/10/25)
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- Biocatalytic synthesis of non-vicinal aliphatic diols
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Biocatalysts are receiving increased attention in the field of selective oxyfunctionalization of C-H bonds, with cytochrome P450 monooxygenases (CYP450s), and the related peroxygenases, leading the field. Here we report on the substrate promiscuity of CYP505A30, previously characterized as a fatty acid hydroxylase. In addition to its regioselective oxyfunctionalization of saturated fatty acids (ω-1-ω-3 hydroxylation), primary fatty alcohols are also accepted with similar regioselectivities. Moreover, alkanes such as n-octane and n-decane are also readily accepted, allowing for the production of non-vicinal diols through sequential oxygenation. This journal is
- Ebrecht, Ana C.,Aschenbrenner, Jasmin C.,Smit, Martha S.,Opperman, Diederik J.
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supporting information
p. 439 - 445
(2021/01/29)
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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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- CYP505E3: A Novel Self-Sufficient ω-7 In-Chain Hydroxylase
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The self-sufficient cytochrome P450 monooxygenase CYP505E3 from Aspergillus terreus catalyzes the regioselective in-chain hydroxylation of alkanes, fatty alcohols, and fatty acids at the ω-7 position. It is the first reported P450 to give regioselective in-chain ω-7 hydroxylation of C10–C16 n-alkanes, thereby enabling the one step biocatalytic synthesis of rare alcohols such as 5-dodecanol and 7-tetradecanol. It shows more than 70 percent regioselectivity for the eighth carbon from one methyl terminus, and displays remarkably high activity towards decane (TTN≈8000) and dodecane (TTN≈2000). CYP505E3 can be used to synthesize the high-value flavour compound δ-dodecalactone via two routes: 1) conversion of dodecanoic acid into 5-hydroxydodecanoic acid (24 percent regioselectivity), which at low pH lactonises to δ-dodecalactone, and 2) conversion of 1-dodecanol into 1,5-dodecanediol (55 percent regioselectivity), which can be converted into δ-dodecalactone by horse liver alcohol dehydrogenase.
- Maseme, Mpeyake Jacob,Opperman, Diederik Johannes,Pennec, Alizé,Smit, Martha Sophia,van Marwijk, Jacqueline
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supporting information
p. 10359 - 10362
(2020/04/23)
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- Ruthenium-Catalyzed Selective Hydrogenation of Epoxides to Secondary Alcohols
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A ruthenium(II)-catalyzed highly selective Markovnikov hydrogenation of terminal epoxides to secondary alcohols is reported. Diverse substitutions on the aryl ring of styrene oxides are tolerated. Benzylic, glycidyl, and aliphatic epoxides as well as diepoxides also underwent facile hydrogenation to provide secondary alcohols with exclusive selectivity. Metal-ligand cooperation-mediated ruthenium trans-dihydride formation and its reaction involving oxygen and the less substituted terminal carbon of the epoxide is envisaged for the origin of the observed selectivity.
- Thiyagarajan, Subramanian,Gunanathan, Chidambaram
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supporting information
p. 9774 - 9778
(2019/12/02)
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- Lithium triethylborohydride as catalyst for solvent-free hydroboration of aldehydes and ketones
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Commercially available and inexpensive lithium triethylborohydride (LiHBEt3) acts as efficient catalyst for the solvent-free hydroboration of a wide range of aldehydes and ketones, which were subsequently transformed to corresponding 1° and 2° alcohols in one-pot procedure at room temperature (rt).
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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supporting information
p. 1912 - 1915
(2019/04/27)
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- OsXCl(phosphine)2(diamine) and OsXCl(diphosphine)(diamine) (X = Cl, H) Complexes for Ketone Hydrogenation
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The osmium complex trans-[OsCl2(PPh3)2(en)] (2) was prepared by reaction of [OsCl2(PPh3)3] (1a) with ethylenediamine (en), whereas the diphosphine derivatives trans-[OsCl2(dppf)(NN)] (NN = en (3), bn (4; bn = 1,4-butanediamine)) and trans-[OsCl2(dpbp)(en)] (5) were obtained from 1a, dppf or dpbp, and the corresponding NN ligand in CH2Cl2 or toluene. An X-ray diffraction study has been provided for 3. The isolation of the chiral derivatives trans-[OsCl2(diphosphine)((R,R)-dpen)] (diphosphine = dppf (6), dpbp (7), (R,R)-skewphos (8)) was achieved by reacting 1a with the diphosphine and (R,R)-dpen in toluene. Treatment of the precursor [Os2Cl4(P(m-tolyl)3)5] (1b) with en afforded [OsCl2(P(m-tolyl)3)2(en)] (9), while reaction of 1b with dppb and N,N-dmen gave [OsCl2(dppb)(N,N-dmen)] (10). The chiral derivatives [OsCl2(diphosphine)(NN)] (11-21; diphosphine = (S)-MeObiphep, (R)-MeObiphep, (R)-xylMeObiphep, (R)-binap, (S)-xylbinap, (R)-xylbinap, (R,S)-Josiphos NN = en, (R,R)-dpen, (R)-daipen, (R,R)-dppn) were prepared from 1b and the corresponding diphosphine and NN ligands in toluene. The monohydride trans-[OsHCl(P(m-tolyl)3)2(en)] (22) was synthesized by reaction of 1b with H2 (1 atm) in the presence of NEt3, followed by addition of en in toluene. Similarly, trans-[OsHCl(dppf)(en)] (23) was synthesized from 1a, H2, and NEt3, followed by treatment with dppf and en. Complexes 2-5, 9, 10, 22, and 23 efficiently catalyzed the hydrogenation of acetophenone with H2 under low pressure (5 atm) at 60-70 °C in ethanol (1-2 mol % of NaOEt) with the ratio S/C = 5000-10000. The chiral derivatives 6-8 and 11-21 afforded the asymmetric hydrogenation of acetophenone with up to 90% ee by combining bulky xylyl-substituted MeObiphep or binap-type ligands with (R)-daipen or (R,R)-dpen ligands. Catalytic transfer hydrogenation of acetophenone was observed with 3, 6, and 7 (S/C = 2000) in 2-propanol and in the presence of NaOiPr (2 mol %) at 60-82 °C.
- Barbato, Cinzia,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,Magnolia, Santo,Siega, Katia,Herdtweck, Eberhardt,Strazzolini, Paolo,Chelucci, Giorgio,Baratta, Walter
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supporting information
p. 65 - 77
(2018/01/17)
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- New boron reagents for cycloboration of α-olefins into boriranes under Cp2TiCl2 catalysis
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The one-pot cycloboration of α-olefins (oct-1-ene, dec-1-ene) for a facile access to substituted boriranes has been carried out with the use of alkyl, arylalkyl, and cycloalkyl boron dichlorides (EtBCl2, n-PentBCl2, n-HexBCl2, Ph(CH2)2BCl2, cyclo-OctBCl2, 2-norbornylBCl2) under Cp2TiCl2 catalysis.
- Khusainova, Liliya I.,Khafizova, Leila O.,Tyumkina, Tatyana V.,Ryazanov, Kirill S.,Popodko, Natalya R.,Dzhemilev, Usein M.
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- An original catalytic synthesis of boriran-1-ols
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2-Alkylboriran-1-ols were obtained in a one-pot process by hydrolysis of 1-fluoro- and 1-chloroboriranes in 90–92% yield. The starting 1-haloboriranes were generated by cycloboration of α-olefins with BCl3·SMe2 or BF3·THF in the presence of Mg metal (acceptor of halogen ions) and Cp2TiCl2 catalyst.
- Khafizova, Leila O.,Khusainova, Liliya I.,Tyumkina, Tat'yana V.,Ryazanov, Kirill S.,Popod'ko, Natal'ya R.,Dzhemilev, Usein M.
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p. 577 - 578
(2018/12/13)
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- Identification of a Robust Carbonyl Reductase for Diastereoselectively Building syn-3,5-Dihydroxy Hexanoate: A Bulky Side Chain of Atorvastatin
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t-Butyl-6-cyano-(3R,5R)-dihydroxyhexanoate is an advanced chiral precursor for the synthesis of the side chain pharmacophore of cholesterol-lowering drug atorvastatin. Herein, a robust carbonyl reductase (LbCR) was newly identified from Lactobacillus brevis, which displays high activity and excellent diastereoselectivity toward bulky t-butyl 6-cyano-(5R)-hydroxy-3-oxo-hexanoate (7). The engineered Escherichia coli cells harboring LbCR and glucose dehydrogenase (for cofactor regeneration) were employed as biocatalysts for the asymmetric reduction of substrate 7. As a result, as much as 300 g L-1 of water-insoluble substrate was completely converted to the corresponding chiral diol with >99.5% de in a space-time yield of 351 g L-1 d-1, indicating a great potential of LbCR for practical synthesis of the very bulky and bi-chiral 3,5-dihydroxy carboxylate side chain of best-selling statin drugs.
- Gong, Xu-Min,Zheng, Gao-Wei,Liu, You-Yan,Xu, Jian-He
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supporting information
p. 1349 - 1354
(2017/09/23)
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- Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2in the synthesis of 2-alkyl(aryl,benzyl)-1-phenylboriranes
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A one-pot method for the synthesis of 2-alkyl(aryl, benzyl)-1-phenylboriranes has been developed via the reaction of α-olefins with PhBCl2in the presence of Cp2TiCl2as the catalyst. The method implies the formation of boriranes as the result of transmetalation of titanacyclopropane intermediates generated in the reaction of α-olefins with Cp2TiCl2. Individual 1-phenyl-2-substituted boriranes were isolated and their structures confirmed by NMR spectral methods.
- Khusainova, Liliya I.,Khafizova, Leila O.,Tyumkina, Tatyana V.,Ryazanov, Kirill S.,Dzhemilev, Usein M.
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- H-Bonding-promoted radical addition of simple alcohols to unactivated alkenes
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H-Bonding-induced radical addition of simple alcohols to unactivated olefins was achieved. It effectively solved the long-standing problems of reactivity and selectivity in this type of reaction. The hydroxyalkylation occurred via site-specific cleavage of the α-hydroxyl-C-H bond in alcohols. This method allows a highly atom-economical, operationally simple and environmentally benign access to diverse primary, secondary and tertiary alcohols, diols, and even polyfluorinated alcohols. These useful chemicals are traditionally synthesized by using commercially unavailable organometallics via complex operations. In contrast, they can be facilely obtained through this protocol utilizing widely available starting materials.
- Tian, Yunfei,Liu, Zhong-Quan
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supporting information
p. 5230 - 5235
(2017/11/09)
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- Base-Free Transfer Hydrogenation of Ketones Using Cp?Ir(pyridinesulfonamide)Cl Precatalysts
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N-(2-(Pyridin-2-yl)ethyl)benzenesulfonamide derivatives and 1,1,1-trifluoro-N-(2-(pyridin-2-yl)ethyl)methanesulfonamide (1-4), along with three-legged piano stool Cp?IrIIICl complexes (5-11) (Cp? = pentamethylcyclopentadienyl) bearing pyridinesulfonamide ligands with varying electronic parameters, were synthesized. These ligands and air-stable complexes were characterized by 1H and 13C{1H} NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Precatalysts, 5-11, were assessed for transfer hydrogenation of aryl, diaryl, dialkyl, linear, cycloaliphatic, and α,β-unsaturated ketones, diones, β-ketoesters, and a biomass-derived substrate with 2-propanol, using 1 mol % precatalyst. Catalysis was also efficient using a 0.1 mol % loading. Remarkably, all catalysis experiments can be conducted in air without dried and degassed substrates, and basic additives and halide abstractors are not required for high activity in transfer hydrogenation. Control experiments and a mercury poisoning experiment support a homogeneous catalyzed pathway. Overall, the fastest reactions are observed using electron-poor substrates and precatalysts bearing electron-rich ligands.
- Ruff, Andrew,Kirby, Christopher,Chan, Benny C.,O'Connor, Abby R.
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p. 327 - 335
(2016/02/19)
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- Alcohol oxidation with H2O2 catalyzed by a cheap and promptly available imine based iron complex
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We previously reported that the iminopyridine iron(II) complex 1, easily and quantitatively obtainable in situ, can activate H2O2 to form a powerful oxidant, capable of aliphatic C-H bond hydroxylation. In the present study we expand the application of this catalyst to the oxidation of a series of alcohols to the corresponding carbonyl compounds. The oxidation of aliphatic alcohols proceeds smoothly, while that of benzylic alcohols is shown to be challenging. Some collected pieces of evidence suggest a preference of the oxidizing species for the aromatic ring instead for the alcoholic moiety. The decrease of the electron density in the aromatic ring shifts the oxidation from the aromatic towards the alcoholic moiety. Quite surprisingly, preferential oxidation of cyclohexanol versus benzylic alcohol was achieved, showing unprecedented selectivity.
- Olivo, Giorgio,Giosia, Simone,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
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supporting information
p. 10630 - 10635
(2016/11/21)
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- Vanadium-Catalyzed Oxidative Debenzylation of O-Benzyl Ethers at ppm Level
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An advantageous methodology for the oxidative debenzylation of ethers has been developed. Very low amounts of a catalyst system based on vanadyl acetylacetonate and a triazole type pincer ligand allow the selective oxidative cleavage of a number of O-benzyl ethers in the presence of oxygen as the sole oxidant. The methodology tolerates a number of functional groups such as halo-, alkoxy-, or trifluoromethylarenes, alkyne, alkene, ether, and acetal units. Large-scale deprotections can be also carried out by the optimized procedure, which is amenable to enantioenriched reactants as well. (Figure presented.).
- Urgoitia, Garazi,SanMartin, Raul,Herrero, María Teresa,Domínguez, Esther
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p. 3307 - 3312
(2016/10/21)
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- Chemo- and Regioselective Functionalization of Polyols through Catalytic C(sp3)-C(sp3) Kumada-Type Coupling of Cyclic Sulfate Esters
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This contribution describes a copper-catalyzed, C(sp3)-C(sp3) cross-coupling reaction of cyclic sulfate esters, a distinct class of electrophilic derivatives of polyols, with alkyl Grignard reagents to afford functionalized alcohol products in good yields. The method is operationally simple and highlights the potential of cyclic sulfate esters as highly reactive substrates in catalytic, chemoselective polyol transformations.
- Ramírez-Contreras, Rodrigo,Morandi, Bill
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supporting information
p. 3718 - 3721
(2016/08/16)
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- PROCESS FOR REDUCING THE OXYGEN CONTENT OF BIOMASS USING VANADIUM-BASED CATALYSTS
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The present invention concerns a process for converting biomass into useful organic building blocks for the chemical industry. The process involves the use of vanadium-based catalysts of the formula Aα+a(VvXxR1yR2z)α*a-, which may be readily prepared from industrial vanadium compounds, for converting a polyol in a solvent.
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Page/Page column 19
(2016/07/27)
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- Additional nucleophile-free FeCl3-catalyzed green deprotection of 2,4-dimethoxyphenylmethyl-protected alcohols and carboxylic acids
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The deprotection of the methoxyphenylmethyl (MPM) ether and ester derivatives can be generally achieved by the combinatorial use of a catalytic Lewis acid and stoichiometric nucleophile. The deprotections of 2,4-dimethoxyphenylmethyl (DMPM)-protected alcohols and carboxylic acids were found to be effectively catalyzed by iron(III) chloride without any additional nucleophile to form the deprotected mother alcohols and carboxylic acids in excellent yields. Since the present deprotection proceeds via the self-assembling mechanism of the 2,4-DMPM protective group itself to give the hardly-soluble resorcinarene derivative as a precipitate, the rigorous purification process by silica-gel column chromatography was unnecessary and the sufficiently-pure alcohols and carboxylic acids were easily obtained in satisfactory yields after simple filtration.
- Sawama, Yoshinari,Masuda, Masahiro,Honda, Akie,Yokoyama, Hiroki,Park, Kwihwan,Yasukawa, Naoki,Monguchi, Yasunari,Sajiki, Hironao
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p. 778 - 784
(2016/07/16)
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- Selective oxidation of hydrocarbons under air using recoverable silver ferrite-graphene (AgFeO2-G) nanocomposite: A good catalyst for green chemistry
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The selective oxidation of hydrocarbons is a main academic and industrial research challenge. A lot of researches have been done about this issue, but till now relatively little attention has been paid to graphene-complex oxide nanocomposites. Herein, we report our studies on a new catalyst. Silver ferrite-graphene (AgFeO2-G) as a separable nanocomposite from the reaction solution, was used as an effective oxidizing agent for the oxidation of various hydrocarbons (1- decene, cyclohexene, cis-cycloctene, cyclohexane, cyclooctane etc.) under mild conditions (55 °C, 8 h) with high conversion and selectivity using air, that is proper for 'green' chemistry. Metal or metal oxide nanoparticles assembled on graphene sheets revealed high electrocatalytic activity. Indeed, AgFeO2 with graphene due to low band gap and graphene oxide with large amounts of oxygen-containing groups, provide facility catalytic activity of catalyst-supported system. We also found that, with this catalyst, selective oxidation could be achieved without the need for the addition of solvent, which is appropriate in particular for 'green' chemistry. The catalysts showed little deactivation and maintained their conversion and selectivity levels duration of the measurements.
- Hosseini, Seyed Majid,Hosseini-Monfared, Hassan,Abbasi, Vahideh,Khoshroo, Mohammad Reza
-
-
- ALKANE OXIDATION BY MODIFIED HYDROXYLASES
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This invention relates to modified hydroxylases. The invention further relates to cells expressing such modified hydroxylases and methods of producing hydroxylated alkanes by contacting a suitable substrate with such cells.
- -
-
Paragraph 0341
(2016/02/16)
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- Mild Deoxygenation of Aromatic Ketones and Aldehydes over Pd/C Using Polymethylhydrosiloxane as the Reducing Agent
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Herein, a practical and mild method for the deoxygenation of a wide range of benzylic aldehydes and ketones is described, which utilizes heterogeneous Pd/C as the catalyst together with the green hydride source, polymethylhydrosiloxane. The developed catalytic protocol is scalable and robust, as exemplified by the deoxygenation of ethyl vanillin, which was performed on a 30 mmol scale in an open-to-air setup using only 0.085 mol% Pd/C catalyst to furnish the corresponding deoxygenated product in 93% yield within 3 hours at room temperature. Furthermore, the Pd/C catalyst was shown to be recyclable up to 6 times without any observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions.
- Volkov, Alexey,Gustafson, Karl P. J.,Tai, Cheuk-Wai,Verho, Oscar,B?ckvall, Jan-E.,Adolfsson, Hans
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supporting information
p. 5122 - 5126
(2015/04/27)
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- Porous Zirconium-Phytic Acid Hybrid: A Highly Efficient Catalyst for Meerwein-Ponndorf-Verley Reductions
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The utilization of compounds from natural sources to prepare functional materials is of great importance. Herein, we describe for the first time the preparation of organic-inorganic hybrid catalysts by using natural phytic acid as building block. Zirconium phosphonate (Zr-PhyA) was synthesized by reaction of phytic acid and ZrCl4 and was obtained as a mesoporous material with pore sizes centered around 8.5 nm. Zr-PhyA was used to catalyze the mild and selective Meerwein-Ponndorf-Verley (MPV) reduction of various carbonyl compounds, e.g., of levulinic acid and its esters into γ-valerolactone. Further studies indicated that both Zr and phosphate groups contribute significantly to the excellent performance of Zr-PhyA. All natural: Porous zirconium phosphonate (Zr-PhyA) was synthesized simply by reaction of natural phytic acid (PhyA) and ZrCl4 and applied as a very efficient catalyst for the Meerwein-Ponndorf-Verley reduction of various carbonyl compounds. Both the Zr element and phosphate groups contributed significantly to the excellent catalytic performance of Zr-PhyA.
- Song, Jinliang,Zhou, Baowen,Zhou, Huacong,Wu, Lingqiao,Meng, Qinglei,Liu, Zhimin,Han, Buxing
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supporting information
p. 9399 - 9403
(2015/08/06)
-
- First example of borirane synthesis by α-olefins reaction with BCl3·SMe2 Catalyzed with (η5-C5H5)2TiCl2
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New method was developed of the synthesis of 2-phenyl(alkyl, benzyl, phenoxy)-1-chloroboriranes via reaction of α-olefins with BCl3·SMe2 catalyzed by Cp2TiCl2. The method is based on the boracyclopropanes (boriranes) formation resulting from transmetallation of titanacyclopropanes arising from the reaction of α-olefins with Cp2TiCl2. The calculations were fulfilled of thermodynamic and activation parameters of possible reaction routes.
- Khusainova,Khafizova,Tyumkina,Dzhemilev
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p. 1517 - 1523
(2015/12/30)
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- Boron-Catalyzed Regioselective Deoxygenation of Terminal 1,2-Diols to 2-Alkanols Enabled by the Strategic Formation of a Cyclic Siloxane Intermediate
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The selective deoxygenation of polyols is a frontier in our ability to harness the stereochemical and structural complexity of natural and synthetic feedstocks. Herein, we describe a highly active and selective boron-based catalytic system for the selective deoxygenation of terminal 1,2-diols at the primary position, a process that is enabled by the transient formation of a cyclic siloxane. The method provides an ideal complement to well-known catalytic asymmetric reactions to prepare synthetically challenging chiral 2-alkanols in nearly perfect enantiomeric excess, as illustrated in a short synthesis of the anti-inflammatory drug (R)-lisofylline. Pick the right one! A highly active and selective boron-based catalytic system enables the selective deoxygenation of terminal 1,2-diols at the primary position via the transient formation of a cyclic siloxane. The utility of this method for the preparation of synthetically challenging chiral 2-alkanols was illustrated by a short synthesis of the anti-inflammatory drug (R)-lisofylline.
- Drosos, Nikolaos,Morandi, Bill
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p. 8814 - 8818
(2015/11/27)
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- Development of chelate resin-supported palladium catalysts for chemoselective hydrogenation
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Abstract Two kinds of palladium catalysts immobilized on a chelate resin bearing diiminoacetate or polyamine moieties on the polystyrene-divinylbenzene polymer were newly prepared by the adsorption of palladium (II) ions on these resins followed by the reduction to palladium (0) with hydrazine monohydrate. Both catalysts showed a similar activity for hydrogenation. A variety of reducible functionalities, except for benzylic alcohol, alkyl benzyl ether, silyl ether, and epoxide, could be reduced under the hydrogenation conditions using either catalyst. Since the palladium metal elution from the immobilized catalysts was never observed, the catalysts could be reused without any decrease in the catalyst activity for at least 5 runs.
- Monguchi, Yasunari,Ichikawa, Tomohiro,Nozaki, Kei,Kihara, Kensuke,Yamada, Yuuko,Miyake, Yutaka,Sawama, Yoshinari,Sajiki, Hironao
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supporting information
p. 6499 - 6505
(2015/08/18)
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- FeCl3-catalyzed self-cleaving deprotection of methoxyphenylmethyl-protected alcohols
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4-Methoxyphenylmethyl ethers are widely utilized as alcohol protecting groups. FeCl3 effectively catalyzes the deprotection of methoxyphenylmethyl-type ethers in a self-cleaving manner to produce oligomeric derivatives and alcohols. Remarkably, the highly pure mother alcohols can be obtained without silica gel column chromatography by using the 2,4-dimethoxyphenylmethyl group as a protective group.
- Sawama, Yoshinari,Masuda, Masahiro,Asai, Shota,Goto, Ryota,Nagata, Saori,Nishimura, Shumma,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 434 - 437
(2015/03/03)
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- Revisiting cytochrome P450-mediated oxyfunctionalization of linear and cyclic alkanes
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Cytochrome P450 monooxygenases (CYPs) of the CYP153 family catalyse terminal hydroxylation of n-alkanes. Alkane hydroxylating mutants of self-sufficient CYP102A1 have also been described. We evaluated two CYP153s (a three-component system and a fused self-sufficient CYP), wildtype CYP102A1 and nine CYP102A1 mutants, for the conversion of three cycloalkanes (C6, C7 and C8) and three n-alkanes (C6, C8 and C10) using whole cells (WCs) and crude cell-free extracts (CFEs). The aim was to identify substrate-enzyme combinations that give high product titres and space-time yields (STYs). Comparisons were made using total turnover numbers (TTNs) and turnover frequencies (TOFs) to normalize for CYP expression. Reactions were carried out using high enzyme and substrate concentrations compatible with high STYs. Under these conditions CYP102A1 and the double R47L,Y51F mutant, although not regioselective, performed better on all substrates in terms of product titres over 8 h, and thus STYs and TTNs, than heavily mutated variants that have been reported to give very high TOFs. CYP153A6, with its ferredoxin (Fdx) and ferredoxin reductase (FdR), emerged as the superior catalyst for conversion of n-alkanes. In addition to its excellent regioselectivity it also gave the highest final product titres and STYs in WC conversions of hexane and octane. Interaction with FdR and Fdx initially limited performance in CFEs, but with additional FdR and Fdx gave 1-octanol titres of 50 mmol·LBRM-1 and TTNs exceeding 12,000 over 18 h, rivalling results reported with self-sufficient CYPs. Selecting biocatalysts for application requires caution, since experimental conditions such as amount of substrate added and solubility as well as cofactor dependence and regeneration can have a profound effect on catalyst performance, while stability and efficiency with regard to cofactor usage (coupling efficiency) are at least as important as TOFs when high product titres and STYs are the target.
- Pennec, Aliz,Jacobs, Cheri L.,Opperman, Diederik J.,Smit, Martha S.
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supporting information
p. 118 - 130
(2015/01/30)
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- Efficient and versatile transfer hydrogenation catalysts: Iridium (III) and ruthenium (II) complexes with 4-acetylbenzyl-N-heterocyclic carbenes
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New 4-acetylbenzyl-N-heterocyclic carbene ligands (1-4) have been used to synthesize iridium complexes 6-9 and ruthenium complex 10. All complexes were characterized by FT-IR, 1H and 13C NMR spectroscopy, elemental analysis, and in the case of 6, by X-ray diffraction studies. The catalytic performance of these iridium and ruthenium complexes for transfer hydrogenation of ketones and imines and N-alkylation of amines with primary alcohols were tested in a range of substrates, and showed high catalytic activity with 1 mol% catalytic loading. The neutral complex 8 with two acetyl groups also showed good catalytic efficiency under lower catalyst loading (0.01 mol%), with the maximum TON of 8000, while on the other hand, the cationic complex 9 with PF6- as counteranion showed good to excellent catalytic activity toward the N-alkylation of amines in a wide scope of substrates. We also found out that the Ir complex 6′ was formed through the intramolecular CH activition of 6 under the transfer hydrogenation conditions.
- Zhu, Xiao-Han,Cai, Li-Hua,Wang, Chen-Xi,Wang, Ya-Nong,Guo, Xu-Qing,Hou, Xiu-Feng
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p. 134 - 141
(2014/07/21)
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- A novel P450-based biocatalyst for the selective production of chiral 2-alkanols
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A P450 monooxygenase from Nocardia farcinica (CYP154A8) catalyses the stereo- and regioselective hydroxylation of n-alkanes, still a challenging task in chemical catalysis. In a biphasic reaction system, the regioselectivity for the C2-position of C7-C9 alkanes was over 90%. The enzyme showed strict S-selectivity for all tested substrates, with enantiomeric excess (ee) of up to 91%. This journal is the Partner Organisations 2014.
- Von Bühler, Clemens J.,Urlacher, Vlada B.
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supporting information
p. 4089 - 4091
(2014/04/03)
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- Tandem isomerization/hydroformylation/hydrogenation of internal alkenes to n-alcohols using Rh/Ru dual-or ternary-catalyst systems
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A one-pot three-step reaction, isomerization/hydroformylation/hydrogenation of internal alkenes to n-alcohols, was accomplished by employing a Rh/Ru dual-catalyst system. By using a combination of Rh(acac)(CO)2/ bisphosphite and Shvo's catalyst, (Z)-2-tridecene was converted to 1-tetradecanol in 83% yield with high normal/iso selectivity (n/i = 12). The method was applicable to other internal alkenes, including functionalized alkenes, such as an alkenol and an alkenoate. Furthermore, addition of a third component, Ru3(CO)12, effectively improved the n/i ratio in the tandem isomerization/hydroformylation/hydrogenation of methyl oleate (from n/i = 1.9 to 4.4). Control experiments revealed that the isomerization was mediated by both Rh and Ru and that the coexistence of Rh and Ru was essential for hydrogenation of aldehyde under H2/CO.
- Yuki, Yamato,Takahashi, Kohei,Tanaka, Yoshiyuki,Nozaki, Kyoko
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p. 17393 - 17400
(2014/01/06)
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- Hydration of alkenes and cycloalkenes in the presence of chromium and copper complexes
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Chromium and copper complexes catalyzed hydration of acyclic and cyclic olefins in the presence of carbon tetrachloride at 110-160 C (4-12 h) with formation of the corresponding alcohols.
- Khusnutdinov,Oshnyakova,Shchadneva
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p. 1428 - 1432
(2014/01/06)
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- Tandem application of C-C bond-forming reactions with reductive ozonolysis
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Several variants of reductive ozonolysis, defined here as the in situ generation of aldehydes or ketones during ozonolytic cleavage of alkenes, are demonstrated to work effectively in tandem with a number of C-C bond-forming reactions. For reactions involving basic nucleophiles (1,2- addition of Grignard reagents, Wittig or Horner-Emmons olefinations, and directed aldol reactions of lithium enolates), the one-pot process offers a rapid and high-yielding alternative to traditional two-step protocols.
- Willand-Charnley, Rachel,Dussault, Patrick H.
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- Continuous biphasic enzymatic reduction of aliphatic ketones
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Biphasic reactions offer an attractive alternative for the utilisation of enzymes for conversion of hardly water soluble substrates. Especially, the alcohol dehydrogenase from Lactobacillus brevis was successfully used for the reductive synthesis of enantiopure secondary aliphatic alcohols. With the enzymatic catalyst and the cofactor effectively retained in the reactive aqueous phase, the continuous operation was demonstrated by continuous addition and withdrawal of the non-reactive phase. The four tested substrates 2-heptanone, 2-octanone, 2-nonanone, and 2-decanone showed that the space time yield and turnover numbers (TON) of the enzyme decrease as the availability of the substrate decreases with increasing partition coefficients. Nevertheless, a TONLbADH of up to 478 × 103 could be achieved. Remarkably, the cofactor utilisation turned out to be very high and a TON NADP+ of more than 20 × 103 was easily achievable for both 2-heptanone and 2-octanone by substrate coupled cofactor regeneration with excess of 2-propanol.
- Leuchs, Susanne,Nonnen, Thomas,Dechambre, Dominique,Na'Amnieh, Shukralla,Greiner, Lasse
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- Palladium, iridium and ruthenium complexes with acyclic imino-N-heterocyclic carbenes and their application in aqua-phase Suzuki-Miyaura cross-coupling reaction and transfer hydrogenation
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Palladium (4a-4c), iridium (5a-5c) and ruthenium (6a-6c) complexes have been prepared by in situ transmetalation from the corresponding silver complexes of acyclic imino-functionalized imidazolium chlorides [1-(Me)-imidazolium-3- {C(p-CH3-Ph)N(Ar)}]Cl (3) (Ar = 2,4,6-trimethylphenyl (3a), 2,6-diisopropylphenyl (3b) and phenyl (3c)) with [Pd(COD)Cl2], [Cp*IrCl2]2 or [Ru(p-cymene)Cl2] 2, respectively. Iridium and ruthenium complexes, 5a[PF 6]-5c[PF6], 6a[PF6]-6c[PF6], 6c[BF4], 6c[BPh4] and 6c[NTf2], were obtained directly from 5a-5c and 6a-6c through an anion-exchange process with KPF 6, NaBF4, NaBPh4 and LiNTf2 (bis(trifluoromethylsulfonyl)imide lithium), respectively. All complexes were characterized by FT-IR, 1H and 13C NMR spectroscopy and elemental analysis. Crystal structures of 4a, 5a and 6c[NTf2] show that five-membered chelate ring is formed in these complexes by the coordination of the carbene carbon and the imino nitrogen atom, and the latter two are cationic compounds with Cl- and NTf2- as counteranion respectively. The catalytic performance of Pd complexes for Suzuki-Miyaura cross-coupling reactions in pure water and Ir and Ru complexes for transfer hydrogenation of ketones and imines was tested in a wide scope of substrates. Pd complex 4b with the largest steric hinder exhibited the best performance to gain moderate to excellent yields on catalyzing Suzuki-Miyaura cross-coupling of aryl chlorides and arylboronic acids in water. While in transfer hydrogenation of various ketones, all the Ir and Ru complexes were effective with good to excellent yields. Among all these complexes, 6c[PF 6] was found most effective, and moderate yields could be obtained even in the transfer hydrogenation of imines. Moreover, different counteranions of Ru complexes are influential on catalyzing the transfer hydrogenation, with the sequence of PF6- ≈ BF4- > BPh4- > Cl- > NTf2 -.
- Guo, Xu-Qing,Wang, Ya-Nong,Wang, Dong,Cai, Li-Hua,Chen, Zhen-Xia,Hou, Xiu-Feng
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p. 14557 - 14567
(2013/01/16)
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- Stereospecific inversion of secondary tosylates to yield chiral methyl-branched building blocks, applied to the asymmetric synthesis of leafminer sex pheromones
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All four of the possible stereoisomers of 5,9-dimethylheptadecane, the major sex pheromone component secreted by female moths of the mountain-ash bentwing (Leucoptera scitella), were synthesized by the coupling of two chiral blocks with a methyl branch at the 2- or 3-position. The blocks were prepared by applying the stereospecific inversion of secondary tosylates, which were derived from (R)- and (S)-propylene oxide, and their enantiopurities were confirmed by chiral HPLC analysis.
- Taguri, Tomonori,Yamakawa, Rei,Fujii, Toru,Muraki, Yuta,Ando, Tetsu
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experimental part
p. 852 - 858
(2012/09/22)
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- Pyridine is an organocatalyst for the reductive ozonolysis of alkenes
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Whereas the cleavage of alkenes by ozone typically generates peroxide intermediates that must be decomposed in an accompanying step, ozonolysis in the presence of pyridine directly generates ketones or aldehydes through a process that neither consumes pyridine nor generates any detectable peroxides. The reaction is hypothesized to involve nucleophile-promoted fragmentation of carbonyl oxides via formation of zwitterionic peroxyacetals.
- Willand-Charnley, Rachel,Fisher, Thomas J.,Johnson, Bradley M.,Dussault, Patrick H.
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supporting information; experimental part
p. 2242 - 2245
(2012/06/30)
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- Low-temperature aerobic oxidation of decane using an oxygen-free radical initiator
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The direct selective oxidation of long chain alkanes by O2 is a highly demanding reaction. We have shown that it is possible to oxidise n-decane in the presence of the oxygen-free radical initiator azobisisobutyronitrile. Formation of a range of oxygenated products has been observed under relatively mild conditions (70 °C in air). Although the presence of a catalyst is not essential when the initiator is used, ceria-based catalysts have been found to increase the selectivity to alcohols by modifying the oxyfunctionalisation of decane.
- Lloyd, Rhys,Jenkins, Robert L.,Piccinini, Marco,He, Qian,Kiely, Christopher J.,Carley, Albert F.,Golunski, Stanislaw E.,Bethell, Donald,Bartley, Jonathan K.,Hutchings, Graham J.
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scheme or table
p. 161 - 167
(2011/11/30)
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- Regioselective ω-hydroxylation of medium-chain n-alkanes and primary alcohols by CYP153 enzymes from Mycobacterium marinum and Polaromonas sp. strain JS666
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The oxofunctionalization of saturated hydrocarbons is an important goal in basic and applied chemistry. Biocatalysts like cytochrome P450 enzymes can introduce oxygen into a wide variety of molecules in a very selective manner, which can be used for the synthesis of fine and bulk chemicals. Cytochrome P450 enzymes from the CYP153A subfamily have been described as alkane hydroxylases with high terminal regioselectivity. Here we report the product yields resulting from C5-C12 alkane and alcohol oxidation catalyzed by CYP153A enzymes from Mycobacterium marinum (CYP153A16) and Polaromonas sp. (CYP153A P. sp.). For all reactions, byproduct formation is described in detail. Following cloning and expression in Escherichia coli, the activity of the purified monooxygenases was reconstituted with putidaredoxin (CamA) and putidaredoxin reductase (CamB). Although both enzyme systems yielded primary alcohols and α,ω-alkanediols, each one displayed a different oxidation pattern towards alkanes. For CYP153A P. sp. a predominant ω-hydroxylation activity was observed, while CYP153A16 possessed the ability to catalyze both ω-hydroxylation and α,ω- dihydroxylation reactions.
- Scheps, Daniel,Honda Malca, Sumire,Hoffmann, Helen,Nestl, Bettina M.,Hauer, Bernhard
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scheme or table
p. 6727 - 6733
(2011/11/30)
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- The reaction of acetal-type protective groups in combination with TMSOTf and 2,2′-bipyridyl; Mild and chemoselective deprotection and direct conversion to other protective groups
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A mild and chemoselective deprotection method of various acetal-type protective groups, such as MOM, MEM, BOM, and SEM ethers, has been developed. The combination of TMSOTf and 2,2′-bipyridyl was very effective for the deprotection, and the reaction proceeded via the formation of pyridinium intermediates, which were hydrolyzed to the corresponding alcohols in good to high yields. The features of this method are mild (almost neutral) reaction conditions and the tolerability of acid-sensitive functional groups. This method is also applicable for the direct conversion of MOM ether to BOM or SEM ether using the appropriate alcohols instead of H2O.
- Fujioka, Hiromichi,Minamitsuji, Yutaka,Kubo, Ozora,Senami, Kento,Maegawa, Tomohiro
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experimental part
p. 2949 - 2960
(2011/05/12)
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- Chiral and nonchiral [OsX2(diphosphane)(diamine)] (X: Cl, OCH2CF3) complexes for fast hydrogenation of carbonyl compounds
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The osmium complexes trans-[OsCl2(dppf)(diamine)] (dppf: 1,1′-bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3, propylenediamine in 4) were prepared by the reaction of [OsCl 2(PPh3)3] (1) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH2CF3 in toluene afforded the alkoxide cis-[Os(OCH2CF3)2(dppf) (ethylenediamine)] (5). The novel precursor [Os2Cl 4(P(m-tolyl)3)5] (2) allows the synthesis of the chiral complexes trans-[OsCl2(diphosphane)(1,2-diamine)] (6-9; diphosphane: (R)-[6,6′dimethoxy(1,1′-biphenyl)-2,2′-diyl] bis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylMeObiphep) or (R)-(1,1′- binaphthalene)-2,2′-diylbis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylbinap); diamine = (R,R)-1,2-diphenylethylenediamine (dpen) or (R,R)-l,2-diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2-diamine in toluene at reflux temperature. Compounds 3-5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H2 at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10000-200000 and achieving turnover frequencies (TOFs) of up to 3.0x 105 h-1 at 70°C. By employment of the chiral compounds 6-9, different ketones, including alkyl aryl, bulky tertbutyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99% and with S/C ratios of 5000-100000 and TOFs of up to4.1xl04h-1at 60°C.
- Baratta, Walter,Barbato, Cinzia,Magnolia, Santo,Siega, Katia,Rigo, Pierluigi
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experimental part
p. 3201 - 3206
(2010/07/02)
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- Chiral pincer ruthenium and osmium complexes for the fast and efficient hydrogen transfer reduction of ketones
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A series of chiral HCNN ligands ((S)-1b-g) (S)-2-(1-aminoethyl)-6-(aryl) pyridine (aryl = 4-MeO-phenyl, 1b; 4-CF3-phenyl, 1c; 3,5-di-Me-phenyl, 1d; 3,5-di-CF3-phenyl, 1e; 1-naphthyl, 1f; 2-naphthyl, 1g) were synthesized starting from commercial 2-acetyl-6- bromopyridine (2), by a chemoenzymatic method involving the dynamic kinetic resolution of the corresponding secondary alcohol (rac-3). The conversion of the resulting (R)-3, obtained in 98% ee, into the homochiral amine ((S)-6), followed by Suzuki coupling with the appropriate arylboronic acids 7b-g, gave access to (S)-1b-g, isolated in 97% ee, with an overall yield up to 50%. The in situ generated pincer complexes [MCl(CNN)(PP)] (M = Ru, Os; PP = Josiphos diphosphine), prepared from [MCl2(PPh3)3], (R,S)-Josiphos diphosphines, and the ligands (S)-1b-g, were found to efficiently catalyze the asymmetric transfer hydrogenation of acetophenone in 2-propanol at 60 °C and in the presence of NaOiPr. On the basis of these data, the 2-naphthyl ruthenium and osmium derivatives [RuCl(CNN)((R,S)-Josiphos*] (8) (HCNN = (S)-1g) and [OsCl(CNN)(PP)] (PP = (R,S)-Josiphos, 9, and (R,S)-Josiphos*, 10) were isolated from [MCl2(PPh 3)3], (R,S)-Josiphos diphosphines, and the ligand (S)-1g. Complexes 8 and 10, displaying the correctly matched chiral PP and CNN - ligands, are highly active and productive catalysts for the transfer hydrogenation of alkyl aryl ketones and methyl pyridyl ketones with TOF = 105-106 h-1, using 0.005 mol % of catalysts and achieving up to 99% ee. The comparison of the catalytic activity of these pincer complexes shows that Ru and Os derivatives display similar rate and enantioselectivity.
- Baratta, Walter,Benedetti, Fabio,Del Zotto, Alessandro,Fanfoni, Lidia,Felluga, Fulvia,Magnolia, Santo,Putignano, Elisabetta,Rigo, Pierluigi
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experimental part
p. 3563 - 3570
(2010/10/03)
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- One-pot system for reduction of epoxides using NaBH4, PdCl 2 catalyst, and moist alumina
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Reduction of epoxides with sodium borohydride, a catalytic amount of palladium(II) chloride, and chromatographic neutral alumina preloaded with a small amount of water (moist alumina) in hexane gave alcohols in good to excellent yields and good selectivity of the desired products under mild conditions. The reaction system was operationally simple and environmentally friendly. The alumina can be recovered simply and reused a number of times without any treatment and with good activity.
- Yakabe, Shigetaka
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experimental part
p. 1339 - 1344
(2010/06/21)
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- Remarkable effect of 2,2′-bipyridyl: Mild and highly chemoselective deprotection of methoxymethyl (MOM) ethers in combination with TMSOTf (TESOTf)-2,2′-bipyridyl
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The remarkable effect of 2,2′-bipyridyl led to the successful development of the mild and highly chemoselective deprotection method of methoxymethyl (MOM) ethers using the combination of TMSOTf (or TESOTf) and 2,2′-bipyridyl; this method can be applied to the direct conversion of the MOM group to other ethereal protective groups (e.g. benzyloxymethyl) with the corresponding alcohols. The Royal Society of Chemistry 2009.
- Fujioka, Hiromichi,Kubo, Ozora,Senami, Kento,Minamitsuji, Yutaka,Maegawa, Tomohiro
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supporting information; experimental part
p. 4429 - 4431
(2009/12/29)
-