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Biocatalytic synthesis of non-vicinal aliphatic diols
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.
supporting information
p. 439 - 445
(2021/01/29)

The effects of metals and ligands on the oxidation of n-octane using iridium and rhodium “PNP” aminodiphosphine complexes
Ir and Rh “PNP” complexes with different ligands are utilized for the oxidation of n-octane. Based on the obtained conversion, selectivity, and the characterized recovered catalysts, it is found that the combination of Ir and the studied ligands does not promote the redox mechanism that is known to result in selective formation of oxo and peroxo compounds [desired species for C(1) activation]. Instead, they support a deeper oxidation mechanism, and thus higher selectivity for ketones and acids is obtained. In contrast, these ligands seem to tune the electron density around the Rh (in the Rh-PNP complexes), and thus result in a higher n-octane conversion and improved selectivity for the C(1) activated products, with minimized deeper oxidation, in comparison to Ir-PNP catalysts.
Naicker, Dunesha,Alapour, Saba,Friedrich, Holger B
p. 282 - 289
(2020/12/01)

Facile Stereoselective Reduction of Prochiral Ketones by using an F420-dependent Alcohol Dehydrogenase
Effective procedures for the synthesis of optically pure alcohols are highly valuable. A commonly employed method involves the biocatalytic reduction of prochiral ketones. This is typically achieved by using nicotinamide cofactor-dependent reductases. In this work, we demonstrate that a rather unexplored class of enzymes can also be used for this. We used an F420-dependent alcohol dehydrogenase (ADF) from Methanoculleus thermophilicus that was found to reduce various ketones to enantiopure alcohols. The respective (S) alcohols were obtained in excellent enantiopurity (>99 % ee). Furthermore, we discovered that the deazaflavoenzyme can be used as a self-sufficient system by merely using a sacrificial cosubstrate (isopropanol) and a catalytic amount of cofactor F420 or the unnatural cofactor FOP to achieve full conversion. This study reveals that deazaflavoenzymes complement the biocatalytic toolbox for enantioselective ketone reductions.
Martin, Caterina,Tjallinks, Gwen,Trajkovic, Milos,Fraaije, Marco W.
p. 156 - 159
(2020/10/26)

Flexible pincer backbone revisited: CuSNS complexes as efficient catalysts in paraffin oxidation
New Cu(II) complexes containing a set of tridentate hybrid SNS ligands were synthesised and fully characterised by IR, HRMS, elemental analysis and single-crystal X-ray diffraction. The complexes with the general formula Cu[bis(Rthioethyl)phenylamine]Cl2 (1); [R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e)] exhibited five-coordinate trigonal bipyramidal geometry around each Cu(II) centre in the solid-state with the S-donor atoms occupying the axial positions. However, complex 1b crystallised as a dimer bridged through a cuprate anion denoted as [1b(μ-CuCl4)1b]. Their application as catalysts in the oxidation of n-octane with hydrogen peroxide (H2O2) as an oxidant gave high substrate conversions to C-8 oxygenate products, mainly octanols, after reduction with PPh3. Notably, complex 1d produced the highest yield of 57% in 1 h reaction time at a catalyst concentration of 1 mol%. In general, high turnover numbers (2830–3180) were recorded for the 1/H2O2 catalytic systems with substantially high combined selectivity of 22–27% to 1-octanol and octanoic acid, which are the more desired products of n-octane oxidation resulting from its terminal carbon (C(1)) activation. The high activity of the catalysts is attributed to metal–ligand cooperative catalysis involving CuII-OOH intermediates as the active species modulated by the tridentate SNS ligands. In comparison with related complexes bearing N-donor atoms, the excellent catalytic performance of these series of CuSNS complexes highlights the critical role of the phenylamine N-donor atom.
Bala, Muhammad D.,Friedrich, Holger B.,Soobramoney, Lynette
supporting information

(2021/07/16)

Organic-inorganic nanocrystal reductase to promote green asymmetric synthesis
An acetophenone reductase from Geotrichum candidum (GcAPRD) was immobilized by the organic-inorganic nanocrystal method. The GcAPRD nanocrystal presented improved stability and recyclability compared with those of the free GcAPRD. Moreover, the GcAPRD nanocrystal reduced broad kinds of ketones with excellent enantioselectivities to produce beneficial chiral alcohols such as (S)-1-(3′,4′-dichlorophenyl)ethanol with >99% yield and >99% ee. The robust and versatile properties of the GcAPRD nanocrystal demonstrated an approach to promote green asymmetric synthesis and sustainable chemistry. This journal is
Koesoema, Afifa Ayu,Matsuda, Tomoko,Tsriwong, Kotchakorn
p. 30953 - 30960
(2020/09/11)

Application of new Ru (II) pyridine-based complexes in the partial oxidation of n-octane
Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine-based ligands: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} with the [(η6-C6H6)Ru(μ-Cl)Cl]2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH2N(R)CH2py}C6H6](PF6)2 (R = C3H7 (1), C (CH3)3 (2), C6H11 (3) and the bidentate Ru (II) complex [Ru{pyCH2N(R)}C6H6]PF6 (R = C6H5 (4)) are reported. It was found that complexes 1, 2, 3 and 4 crystallised as mono-metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n-octane using t-BuOOH and H2O2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t-BuOOH as oxidant, however, superior yields (23–32%) were achieved using H2O2 over all systems. The selectivity was predominantly towards alcohols (particularly 2-octanol) over all complexes using t-BuOOH and H2O2 after reduction of the formed alkylhydroperoxides in solution by PPh3. High TONs of up to 2400 were achieved over the Ru/H2O2 systems.
Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
(2019/12/24)

Reversal of Regioselectivity in Zinc-Dependent Medium-Chain Alcohol Dehydrogenase from Rhodococcus erythropolis toward Octanone Derivatives
The zinc-dependent medium-chain alcohol dehydrogenase from Rhodococcus erythropolis (ReADH) is one of the most versatile biocatalysts for the stereoselective reduction of ketones to chiral alcohols. Despite its known broad substrate scope, ReADH only accepts carbonyl substrates with either a methyl or an ethyl group adjacent to the carbonyl moiety; this limits its use in the synthesis of the chiral alcohols that serve as a building blocks for pharmaceuticals. Protein engineering to expand the substrate scope of ReADH toward bulky substitutions next to carbonyl group (ethyl 2-oxo-4-phenylbutyrate) opens up new routes in the synthesis of ethyl-2-hydroxy-4-phenylbutanoate, an important intermediate for anti-hypertension drugs like enalaprilat and lisinopril. We have performed computer-aided engineering of ReADH toward ethyl 2-oxo-4-phenylbutyrate and octanone derivatives. W296, which is located in the small binding pocket of ReADH, sterically restricts the access of ethyl 2-oxo-4-phenylbutyrate, octan-3-one or octan-4-one toward the catalytic zinc ion and thereby limits ReADH activity. Computational analysis was used to identify position W296 and site-saturation mutagenesis (SSM) yielded an improved variant W296A with a 3.6-fold improved activity toward ethyl 2-oxo-4-phenylbutyrate when compared to WT ReADH (ReADH W296A: 17.10 U/mg and ReADH WT: 4.7 U/mg). In addition, the regioselectivity of ReADH W296A is shifted toward octanone substrates. ReADH W296A has a more than 16-fold increased activity toward octan-4-one (ReADH W296A: 0.97 U/mg and ReADH WT: 0.06 U/mg) and a more than 30-fold decreased activity toward octan-2-one (ReADH W296A: 0.23 U/mg and ReADH WT: 7.69 U/mg). Computational and experimental results revealed the role of position W296 in controlling the substrate scope and regiopreference of ReADH for a variety of carbonyl substrates.
Dhoke, Gaurao V.,Ensari, Yunus,Hacibaloglu, Dinc Yasat,G?rtner, Anna,Ruff, Anna Jo?lle,Bocola, Marco,Davari, Mehdi D.
p. 2957 - 2965
(2020/07/06)

Preparation of flavin-containing mesoporous network polymers and their catalysis
Riboflavin tetramethacrylate (RFlTMA) was prepared as a flavin monomer and copolymerized with ethylene glycol dimethacrylate (EGDMA) under polymerization-induced phase separation conditions. The resulting flavin-containing mesoporous network polymer, poly(RFlTMA-co-EGDMA), was found to be a more effective catalyst than riboflavin tetraacetate (RFlTA), a soluble analogue, for aerobic hydrogenation of olefins despite its heterogeneity, which allowed for its multiple recovery and reuse through simple filtrations and washings without loss in catalytic activity. In addition, the polymeric flavin was demonstrated to be utilized also as an effective photocatalyst in the oxidation of benzyl alcohols.
Arakawa, Yukihiro,Sato, Fumiaki,Ariki, Kenta,Minagawa, Keiji,Imada, Yasushi
supporting information

(2020/02/15)

Coordination chemistry and catalytic applications of Pd(II)–, and Ni(II)–sulfosalan complexes in aqueous media
With the aim of identifying new types of water-soluble catalyst precursors for modification of biological membranes by homogeneous hydrogenation in aqueous solution and under mild conditions, we have performed detailed equilibrium and spectroscopic charac
Lihi, Norbert,Bunda, Szilvia,Udvardy, Antal,Joó, Ferenc
(2019/11/29)

Structural basis for a highly (S)-enantioselective reductase towards aliphatic ketones with only one carbon difference between side chain
Aliphatic ketones, such as 2-butanone and 3-hexanone, with only one carbon difference among side chains adjacent to the carbonyl carbon are difficult to be reduced enantioselectively. In this study, we utilized an acetophenone reductase from Geotrichum candidum NBRC 4597 (GcAPRD) to reduce challenging aliphatic ketones such as 2-butanone (methyl ethyl ketone) and 3-hexanone (ethyl propyl ketone) to their corresponding (S)-alcohols with 94% ee and > 99% ee, respectively. Through crystallographic structure determination, it was suggested that residue Trp288 limit the size of the small binding pocket. Docking simulations imply that Trp288 plays an important role to form a C-H?π interaction for proper orientation of ketones in the pro-S binding pose in order to produce (S)-alcohols. The excellent (S)-enantioselectivity is due to a non-productive pro-R binding pose, consistent with the observation that the (R)-alcohol acts as an inhibitor of (S)-alcohol oxidation.
Koesoema, Afifa Ayu,Sugiyama, Yosuke,Xu, Zichang,Standley, Daron M.,Senda, Miki,Senda, Toshiya,Matsuda, Tomoko
p. 9543 - 9553
(2019/09/16)

Photostable Helical Polyfurans
This report describes the design and synthesis of a new class of polyfurans bearing ester side chains. The macromolecules can be synthesized using catalyst-transfer polycondensation, providing precise control over molecular weight and molecular weight distribution. Such obtained furan ester polymers are significantly more photostable than their alkyl analogues owing to the electron-withdrawing nature of the attached subunit. Most interestingly, they spontaneously fold into a compact π-stacked helix, yielding a complex multilayer cylindrical nanoparticle with a hollow, rigid, conjugated core composed of the polyfuran backbone and a soft, insulating outer layer formed by the ester side chains. The length of polymer side chains dictates the outer diameter of such nanoparticles, which for the hexyl ester groups used in the present study is equal to ～2.3 nm. The inner cavity of the conjugated core is lined with oxygen atoms, which set its effective diameter to 0.4 nm. Furthermore, installation of bulkier, branched chiral ester side chains on the repeat unit yields structures that, upon change of solvent, can reversibly transition between an ordered chiral helical folded and disordered unfolded state.
Varni, Anthony J.,Fortney, Andria,Baker, Matthew A.,Worch, Joshua C.,Qiu, Yunyan,Yaron, David,Bernhard, Stefan,Noonan, Kevin J. T.,Kowalewski, Tomasz
supporting information
p. 8858 - 8867
(2019/06/07)

A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
supporting information
p. 8321 - 8331
(2019/06/04)

Synthesis of Co(II) NNN-pyridine based complexes and their activity in the partial oxidation of n-octane
A series of four NNN-pyridine based ligands of the general form: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} were synthesised and characterised. Complexation of each ligand to CoCl2?6H2O afforded new Co(II) complexes [Co{pyCH2N(R)CH2py}Cl2] (R = C3H7 (1), C(CH3)3 (2), C6H11 (3) and C6H5 (4)). Single crystal X-ray diffraction data confirmed that complex 1 crystallised as a mononuclear unit and was characterised by a distorted trigonal bipyramidal arrangement of ligands around Co. As catalysts in the oxidation of n-octane using t-BuOOH as oxidant, 2 (10% product yield) was found to be most efficient and the selectivity over 1–4 was predominantly towards 2-octanol, after reduction of alkylhydroperoxides by PPh3. All catalysts were significantly more active in the activation of n-octane using hydrogen peroxide, with a yield of 45% observed over catalyst 3. Furthermore, with H2O2, all catalysts produced a high concentration of alkylhydroperoxides, with catalyst 4 giving up to 91% alcohols after workup. TONs of up to 1100 were achieved over the Co/H2O2 systems.
Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
(2019/07/12)

Efficient and Practical Transfer Hydrogenation of Ketones Catalyzed by a Simple Bidentate Mn?NHC Complex
Catalytic reductions of carbonyl-containing compounds are highly important for the safe, sustainable, and economical production of alcohols. Herein, we report on the efficient transfer hydrogenation of ketones catalyzed by a highly potent Mn(I)?NHC complex. Mn?NHC 1 is practical at metal concentrations as low as 75 ppm, thus approaching loadings more conventionally reserved for noble metal based systems. With these low Mn concentrations, catalyst deactivation is found to be highly temperature dependent and becomes especially prominent at increased reaction temperature. Ultimately, understanding of deactivation pathways could help close the activity/stability-gap with Ru and Ir catalysts towards the practical implementation of sustainable earth-abundant Mn-complexes.
van Putten, Robbert,Benschop, Joeri,de Munck, Vincent J.,Weber, Manuela,Müller, Christian,Filonenko, Georgy A.,Pidko, Evgeny A.
p. 5232 - 5235
(2019/07/18)

Hydrosilylation of carbonyl and carboxyl groups catalysed by Mn(i) complexes bearing triazole ligands
Manganese(i) complexes bearing triazole ligands are reported as catalysts for the hydrosilylation of carbonyl and carboxyl compounds. The desired reaction proceeds readily at 80 °C within 3 hours at catalyst loadings as low as 0.25 to 1 mol%. Hence, good to excellent yields of alcohols could be obtained for a wide range of substrates including ketones, esters, and carboxylic acids illustrating the versatility of the metal/ligand combination.
Martínez-Ferraté, Oriol,Chatterjee, Basujit,Werlé, Christophe,Leitner, Walter
p. 6370 - 6378
(2019/11/20)

Asymmetric Enzymatic Hydration of Unactivated, Aliphatic Alkenes
The direct enantioselective addition of water to unactivated alkenes could simplify the synthesis of chiral alcohols and solve a long-standing challenge in catalysis. Here we report that an engineered fatty acid hydratase can catalyze the asymmetric hydration of various terminal and internal alkenes. In the presence of a carboxylic acid decoy molecule for activation of the oleate hydratase from E. meningoseptica, asymmetric hydration of unactivated alkenes was achieved with up to 93 % conversion, excellent selectivity (>99 % ee, >95 % regioselectivity), and on a preparative scale.
Demming, Rebecca M.,Hammer, Stephan C.,Nestl, Bettina M.,Gergel, Sebastian,Fademrecht, Silvia,Pleiss, Jürgen,Hauer, Bernhard
supporting information
p. 173 - 177
(2018/12/11)

Symmetric triazolylidene Ni(II) complexes applied as oxidation catalysts
A set of related Ni(II) complexes of N-heterocyclic carbene ligands (NHC) [trans-X2Ni(NHC)2] (X = Cl, I) bearing linear straight chain alkyl wingtip substituents have been synthesised and fully characterised. Single crystal XRD data revealed symmetrically aligned Ni(II) centres within square planar coordination of trans halide, trans NHC ligands. The complexes were used for the catalytic oxidation of alkanes under mild conditions in conjunction with tert-butyl hydroperoxide as an oxidant. Under optimised reaction conditions, the catalytic results pointed to good activities of circa 15% and 19% for cyclohexane and n-octane respectively. Furthermore, the catalytic systems are shown to be very efficient for the oxidation of linear alcohols to corresponding ketones.
Mncube, Siyabonga G.,Bala, Muhammad D.
p. 467 - 473
(2018/11/06)

Flexible SNS pincer complexes of copper: Synthesis, structural characterisation and application in n-octane oxidation
Two new tridentate SNS ligands based on a flexible, straight chain amine backbone were prepared and in combination with three related but previously reported ligands were reacted with CuCl2 to yield new tridentate pincer-type copper(II) complexes. The molecular structures of the new ligands bis(cyclohexylthioethyl)methylamine (L1d), bis(t-butylthioethyl)methylamine (L1e), and all the complexes Cu[bis(Rthioethyl)methylamine]Cl2 (1) where R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e); were confirmed by a range of spectroscopic and analytical techniques. Single crystal X-ray diffraction analysis determined the solid-state structures of the salt of L1e and the complexes. Complexes 1a-e all exhibited five-coordinate ligand geometry around each Cu(II) centre defined by the tridentate SNS and two chlorido donors. The complexes were applied as catalysts in the oxidation of n-octane using t-butyl hydroperoxide and hydrogen peroxide (H2O2) as oxidants. The H2O2 based systems yielded up to 36% conversion of n-octane to C-8 oxygenates with very high alcohol selectivity of up to 78%.
Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.,Pillay, Michael N.
p. 63 - 70
(2019/03/04)

Additive-Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base increases the speed of the reaction drastically. Although some evidence was obtained supporting a dehydrogenation–hydrogenation mechanism, it was proven that this is not the major mechanism. Instead, the cobalt hydride complex formed by dehydrogenation of ethanol is capable of double-bond isomerization through alkene insertion–elimination.
Spiegelberg, Brian,Dell'Acqua, Andrea,Xia, Tian,Spannenberg, Anke,Tin, Sergey,Hinze, Sandra,de Vries, Johannes G.
supporting information
p. 7820 - 7825
(2019/05/22)

Manganese PNP-pincer catalyzed isomerization of allylic/homo-allylic alcohols to ketones-activity, selectivity, efficiency
We report the first manganese catalyzed isomerization of allylic alcohols to produce the corresponding carbonyl compounds. The ligand plays a decisive role in the efficiency of this reaction. Very high conversions could be obtained using a solvent-free reaction system. A detailed DFT study reveals a self-dehydrogenation/hydrogenation reaction mechanism which was verified by the isolation of the α,β-unsaturated ketone as intermediate and a deuterium labeling experiment. It also provided a rationale for the observed selectivity and the higher efficiency of phenyl over isopropyl substitution.
Xia, Tian,Spiegelberg, Brian,Wei, Zhihong,Jiao, Haijun,Tin, Sergey,Hinze, Sandra,De Vries, Johannes G.
p. 6327 - 6334
(2019/11/20)

Phosphine-free cobalt catalyst precursors for the selective hydrogenation of olefins
Cobalt(ii) complexes bearing phosphine-free tridentate NNS ligands were prepared. Depending on the ligand, dimeric or monomeric complexes were isolated. Monomeric Co(NNMeS)Cl2 selectively catalysed the hydrogenation of olefins in the presence of reducible moieties such as ketones. Further investigation showed that this complex functions as a nanoparticle precursor under the reaction conditions.
Puylaert, Pim,Dell'Acqua, Andrea,El Ouahabi, Fatima,Spannenberg, Anke,Roisnel, Thierry,Lefort, Laurent,Hinze, Sandra,Tin, Sergey,De Vries, Johannes Gerardus
p. 61 - 64
(2019/01/14)

Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates
Anionic α-diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4-cod)}] (1; Dipp=2,6-diisopropylphenyl, cod=1,5-cyclooctadiene), catalyze the dehydrogenation of several amine-boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N-heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine-borane.
Maier, Thomas M.,Sandl, Sebastian,Shenderovich, Ilya G.,Jacobi von Wangelin, Axel,Weigand, Jan J.,Wolf, Robert
supporting information
p. 238 - 245
(2019/01/04)

Biocatalytic Racemization Employing TeSADH: Substrate Scope and Organic Solvent Compatibility for Dynamic Kinetic Resolution
Racemization in combination with a kinetic resolution is the base for a dynamic kinetic resolution (DKR). Biocatalytic racemization was successfully performed for a broad scope of sec-alcohols by employing a single alcohol dehydrogenase (ADH) variant from Thermoanaerobacter pseudoethanolicus (formerly T. ethanolicus; TeSADH W110A I86A C295A). The catalyst employed as a lyophilized whole cell preparation or cell free extract, which tolerated various non-water miscible organic solvents under micro-aqueous or two-phase conditions, whereby cyclohexane and n-hexane suited best. Various concepts for combining the enzymatic racemization with an enzymatic kinetic resolution to achieve overall a bis-enzymatic DKR were evaluated. A proof of concept showed a successful DKR with racemization in aqueous phase combined with acylation in the organic phase.
Pop?oński, Jaros?aw,Reiter, Tamara,Kroutil, Wolfgang
p. 763 - 768
(2018/02/27)

A Straightforward Deracemization of sec-Alcohols Combining Organocatalytic Oxidation and Biocatalytic Reduction
An efficient organocatalytic oxidation of racemic secondary alcohols, mediated by sodium hypochlorite (NaOCl) and 2-azaadamantane N-oxyl (AZADO), has been conveniently coupled with a highly stereoselective bioreduction of the intermediate ketone, catalyzed by ketoreductases, in aqueous medium. The potential of this one-pot two-step deracemization process has been proven by a large set of structurally different secondary alcohols. Reactions were carried out up to 100 mm final concentration enabling the preparation of enantiopure alcohols with very high isolated yields (up to 98 %). When the protocol was applied to the stereoisomeric rac/meso mixture of diols, these were obtained with very high enantiomeric excesses and diastereomeric ratios (95 % yield, >99 % ee, >99: 1 dr).
Liardo, Elisa,Ríos-Lombardía, Nicolás,Morís, Francisco,González-Sabín, Javier,Rebolledo, Francisca
p. 3031 - 3035
(2018/06/27)

Interplay between H-bonding and interpenetration in an aqueous copper(ii)-aminoalcohol-pyromellitic acid system: self-assembly synthesis, structural features and catalysis
Two new copper(ii) coordination compounds, [Cu(H1.5mdea)2]2(H2pma) (1a) and [{Cu2(μ-Hmdea)2}2(μ4-pma)]n·2nH2O (1b), were self-assembled at different temperatures from the same multicomponent reaction system, comprising copper(ii) nitrate, N-methyldiethanolamine (H2mdea), pyromellitic acid (H4pma), and potassium hydroxide. Products 1a and 1b were isolated as microcrystalline solids and fully characterized and their structures were established by single-crystal X-ray diffraction. Compound 1a features the bis-aminoalcohol(ate) monocopper(ii) units and H2pma2? anions that are multiply interconnected by strong H-bonds into a firm 2D H-bonded layer. Compound 1b reveals the bis-aminoalcoholate dicopper(ii) motifs that are interlinked by the μ4-pma4? spacers into a 3D + 3D interpenetrated metal-organic framework. From a topological perspective, both networks of 1a and 1b are uninodal and driven by similar 4-connected H2pma2? or pma4? nodes, but result in distinct sql and dia topologies, respectively. Compound 1a was applied as an efficient catalyst for two model cycloalkane functionalization reactions: (1) oxidation by H2O2 to form cyclic alcohols and ketones and (2) hydrocarboxylation by CO/H2O and S2O82? to form cycloalkanecarboxylic acids. The substrate scope, effects of various reaction parameters, selectivity and mechanistic features were also investigated.
Fernandes, Tiago A.,Kirillova, Marina V.,André, Vania,Kirillov, Alexander M.
p. 16674 - 16683
(2018/12/05)

Utilisation of new NiSNS pincer complexes in paraffin oxidation
Two series of closely related SNS pincer ligands (L) were synthesised with the major structural variation on the nitrogen backbone containing either the methyl [L = (RSCH2CH2)2NMe: where R = Me (1), Et (2), Bu (3)] or the phenyl [L = (RSCH2CH2)2NPh: where R = Me (4), Et (5), Cy (6)] functional group. When ligands 1–3 were complexed to Ni by reaction with Ni(DME)Cl2 (DME = dimethoxyethane), they respectively yielded three new cationic dimeric [LNi(μ-Cl)3NiL]+ complexes (7–9), whilst ligands 4–6 on reaction with Ni(PPh3)2Br2 respectively yielded neutral mononuclear (LNiBr2) complexes 10–12. All the new compounds were characterised by IR, HRMS, elemental analysis and in addition, single crystal X-ray diffraction for complexes 9–12. X-ray structural data of 9 revealed an unusual three chlorido-bridged Ni dimer with the SNS ligand coordinated in a facial binding mode to the two pseudo-octahedral Ni centres. Molecular structures of complexes 10, 11 and 12 each displayed five-coordinate distorted trigonal bipyramidal geometry around the nickel(II) metal centres. When utilised as catalysts in the tert-butyl hydroperoxide oxidation of n-octane, all the complexes showed activity to mainly products of internal carbon activation (octanones and secondary octanols) with 11 as the most active (10% total substrate to oxygenates yield), whereas 10 was the least active, but most selective towards alcohols (alcohol/ketone = 2.13).
Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.
p. 97 - 105
(2018/05/09)

Selective Base-free Transfer Hydrogenation of α,β-Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source
Commercially available Ru-MACHOTM-BH is an active catalyst for the hydrogenation of several functional groups and for the dehydrogenation of alcohols. Herein, we report on the new application of this catalyst to the base-free transfer hydrogenation of carbonyl compounds. Ru-MACHOTM-BH proved to be highly active and selective in this transformation, even with α,β-unsaturated carbonyl compounds as substrates. The corresponding aliphatic, aromatic and allylic alcohols were obtained in excellent yields with catalyst loadings as low as 0.1–0.5 mol % at mild temperatures after very short reaction times. This protocol tolerates iPrOH and EtOH as hydrogen sources. Additionally, scale up to multi-gram amounts was performed without any loss of activity or selectivity. An outer-sphere mechanism has been proposed and the computed kinetics and thermodynamics of crotonaldehyde and 1-phenyl-but-2-en-one are in perfect agreement with the experiment.
Farrar-Tobar, Ronald A.,Wei, Zhihong,Jiao, Haijun,Hinze, Sandra,de Vries, Johannes G.
supporting information
p. 2725 - 2734
(2018/02/28)

Aminotriazole Mn(I) Complexes as Effective Catalysts for Transfer Hydrogenation of Ketones
A catalytic system based on complexes comprising abundant and cheap manganese together with readily available aminotriazole ligands is reported. The new Mn(I) complexes are catalytically competent in transfer hydrogenation of ketones with 2-propanol as hydrogen source. The reaction proceeds under mild conditions at 80 °C for 20 h with 3 % of catalyst loading using either KOtBu or NaOH as base. Good to excellent yields were obtained for a wide substrate scope with broad functional group tolerance. The obtained results by varying the substitution pattern of the ligand are consistent with an out-sphere mechanism for the H-transfer.
Martínez-Ferraté, Oriol,Werlé, Christophe,Franciò, Giancarlo,Leitner, Walter
p. 4514 - 4518
(2018/10/20)

Isomerization of Allylic Alcohols to Ketones Catalyzed by Well-Defined Iron PNP Pincer Catalysts
[Fe(PNP)(CO)HCl] (PNP=di-(2-diisopropylphosphanyl-ethyl)amine), activated in situ with KOtBu, is a highly active catalyst for the isomerization of allylic alcohols to ketones without an external hydrogen supply. High reaction rates were obtained at 80 °C, but the catalyst is also sufficiently active at room temperature with most substrates. The reaction follows a self-hydrogen-borrowing mechanism, as verified by DFT calculations. An alternative isomerization through alkene insertion and β-hydride elimination could be excluded on the basis of a much higher barrier. In alcoholic solvents, the ketone product is further reduced to the saturated alcohol.
Xia, Tian,Wei, Zhihong,Spiegelberg, Brian,Jiao, Haijun,Hinze, Sandra,de Vries, Johannes G.
supporting information
p. 4043 - 4049
(2018/01/27)

Olefin-Stabilized Cobalt Nanoparticles for C=C, C=O, and C=N Hydrogenations
The development of cobalt catalysts that combine easy accessibility and high selectivity constitutes a promising approach to the replacement of noble-metal catalysts in hydrogenation reactions. This report introduces a user-friendly protocol that avoids complex ligands, hazardous reductants, special reaction conditions, and the formation of highly unstable pre-catalysts. Reduction of CoBr2 with LiEt3BH in the presence of alkenes led to the formation of hydrogenation catalysts that effected clean conversions of alkenes, carbonyls, imines, and heteroarenes at mild conditions (3 mol % cat., 2–10 bar H2, 20–80 °C). Poisoning studies and nanoparticle characterization by TEM, EDX, and DLS supported the notion of a heterotopic catalysis mechanism.
Sandl, Sebastian,Schwarzhuber, Felix,P?llath, Simon,Zweck, Josef,Jacobi von Wangelin, Axel
supporting information
p. 3403 - 3407
(2018/02/13)

Asymmetric Reduction of Prochiral Ketones by Using Self-Sufficient Heterogeneous Biocatalysts Based on NADPH-Dependent Ketoreductases
The development of cell-free and self-sufficient biocatalytic systems represents an emerging approach to address more complex synthetic schemes under nonphysiological conditions. Herein, we report the development of a self-sufficient heterogeneous biocatalyst for the synthesis of chiral alcohols without the need to add an exogenous cofactor. In this work, an NADPH-dependent ketoreductase was primarily stabilized and further co-immobilized with NADPH to catalyze asymmetric reductions without the addition of an exogenous cofactor. As a result, the immobilized cofactor is accessible, and thus, it is recycled inside the porous structure without diffusing out into the bulk, as demonstrated by single-particle in operando studies. This self-sufficient heterogeneous biocatalyst was used and recycled for the asymmetric reduction of eleven carbonyl compounds in a batch reactor without the addition of exogenous NADPH to achieve the corresponding alcohols in 100 % yield and >99 % ee; this high performance was maintained over five consecutive reaction cycles. Likewise, the self-sufficient heterogeneous biocatalyst was integrated into a plug flow reactor for the continuous synthesis of one model secondary alcohol, which gave rise to a space-time yield of 97–112 g L?1 day?1; additionally, the immobilized cofactor accumulated a total turnover number of 1076 for 120 h. This is one of the few examples of the successful implementation of continuous reactions in aqueous media catalyzed by cell-free and immobilized systems that integrate both enzymes and cofactors into the solid phase.
Benítez-Mateos, Ana I.,San Sebastian, Eneko,Ríos-Lombardía, Nicolás,Morís, Francisco,González-Sabín, Javier,López-Gallego, Fernando
p. 16843 - 16852
(2017/11/16)

Methods to produce fuels
The present disclosure generally relates to the catalytic conversion of alcohols into hydrocarbon ketones suitable for use as fuels. More specifically, the present disclosure relates to the catalytic conversion of a mixture of isopropanol-butanol-ethanol (IBE) or acetone-butanol-ethanol (ABE), into ketones suitable for use as fuels. The ABE or IBE mixtures may be obtained from the fermentation of biomass or sugars.
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Page/Page column 43; 44

(2018/02/28)

Method for recycling isooctanol from isooctyl thioglycolate rectifying residual liquid
The invention discloses a method for recycling isooctanol from an isooctyl thioglycolate rectifying residual liquid, wherein the method comprises the following steps: (1) saponification: adding the isooctyl thioglycolate rectifying residual liquid into a reaction kettle, slowly dropping a sodium hydroxide solution, increasing the temperature slowly, finally keeping the dropping temperature at 50-65 DEG C, after sodium hydroxide solution dropping is finished, carrying out heat preservation for 2 h or more at the temperature of 55-60 DEG C, and separating to remove a lower-layer aqueous layer, to obtain an upper-layer isooctanol crude product; (2) water washing and neutralization: adding dilute hydrochloric acid into a saponification kettle, neutralizing, adjusting the pH value to 7-8, separating to remove a lower-layer aqueous layer, and washing with water; and (3) drying and fine steaming: drying the isooctanol crude product with a dryer, then putting into a rectifying kettle, under reduced pressure, rectifying the product, and collecting a fraction, to obtain an isooctanol fine product. Compared with the prior art, the method has the advantage of low cost, has a certain economic benefit and reduces environmental pollution.
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Paragraph 0008; 0009; 0010

(2017/08/27)

Base metal Schiff base complexes applied as catalysts for the oxidation of n-octane
The catalytic oxidation of n-octane to value-added oxygenates has been studied with a series of salen-type complexes of iron. The four iron Schiff base complexes N,N′-bis(salicylidene)-L-iron(III) chloride [L?=?1,2-phenylenediamine (5); ethylenediamine (6); propylenediamine (7) and butylenediamine (8)] were synthesised by variation of the bridging diamine backbone. All the complexes are fully characterised and the crystal structure of 7 is for the first time reported as a centrosymmetric dimer observed to crystallise in the triclinic P1￣ system. The application of 5–8 in this oxidation reaction represents a rare example of the systematic use of iron-salen complexes for the liquid-phase functionalisation of Csp3–H bonds of straight chain alkanes. All catalysts displayed activity with H2O2 and TBHP as oxidants that resulted in a mixture of oxygenated products dominated by the ketones (2-, 3- and 4-octanones). Observed trends and variations in catalytic activities of the complexes is related to differences in chemical/structural features and changes in reaction conditions. A detailed analysis of selectivity parameters of the complexes to the variety of oxygenates is also presented and rationalised.
Kadwa, Ebrahim,Friedrich, Holger B.,Bala, Muhammad D.
p. 112 - 117
(2017/04/27)

Efficient Catalytic Greenhouse Gas-Free Hydrogen and Aldehyde Formation from Alcohols
Catalytic preparation of hydrogen and aldehyde(s) from alcohols, including bioalcohols, without production of carbon monoxide or carbon dioxide.
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Paragraph 0053; 0054; 0148

(2017/11/07)

Facile synthesis of [Ru(η2-O2CO)(pta)(η6-p-cymene)], an outstandingly active Ru(II) half-sandwich complex for redox isomerization of allylic alcohols
The water-soluble [RuCl2(pta)(η6-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-1-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of “in situ” catalyst ([RuCl2(pta)(η6-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(η2-O2CO)(pta)(η6-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction).
Bolyog-Nagy, Evelin,Udvardy, Antal,Barczáné-Bertók, ágnes,Joó, Ferenc,Kathó, ágnes
p. 514 - 520
(2016/12/02)

Base free transfer hydrogenation using a covalent triazine framework based catalyst
Isomerisation of allylic alcohols to saturated ketones can be efficiently catalysed by a heterogeneous molecular system resulting from IrIIICp? anchoring to a covalent triazine framework. The obtained catalysts are active, selective, and fully recyclable.
Bavykina,Mautscke,Makkee,Kapteijn,Gascon,Llabrési Xamena
p. 4166 - 4170
(2017/08/04)

From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction
The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning.
Ríos-Lombardía, Nicolás,Vidal, Cristian,Liardo, Elisa,Morís, Francisco,García-álvarez, Joaquín,González-Sabín, Javier
supporting information
p. 8691 - 8695
(2016/07/21)

ALKANE OXIDATION BY MODIFIED HYDROXYLASES
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.
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Paragraph 0303

(2016/02/16)

Oxidation of Alkanes by Periodate Using a MnV Nitrido Complex as Catalyst
The design of catalytic systems that can selectively oxidize unactivated C?H bonds under mild conditions is a challenge to chemists. We report here that the manganese(V) nitrido complex [MnV(N)(CN)4]2? is a highly efficient catalyst for the oxidation of alkanes by periodate (IO4 ?) at ambient conditions. Excellent yields of alcohols and ketones (>95 %) are obtained with a maximum turnover number (TON) of 3000.
Ma, Li,Chen, Lingjing,Lau, Tai-Chu
p. 2846 - 2848
(2016/10/25)

Reactivity of a Carbon-Supported Single-Site Molybdenum Dioxo Catalyst for Biodiesel Synthesis
A single-site molybdenum dioxo catalyst, (Oc)2Mo(=O)2@C, was prepared via direct grafting of MoO2Cl2(dme) (dme = 1,2-dimethoxyethane) on high-surface-area activated carbon. The physicochemical and chemical properties of this catalyst were fully characterized by N2 physisorption, ICP-AES/OES, PXRD, STEM, XPS, XAS, temperature-programmed reduction with H2 (TPR-H2), and temperature-programmed NH3 desorption (TPD-NH3). The single-site nature of the Mo species is corroborated by XPS and TPR-H2 data, and it exhibits the lowest reported MoOx Tmax of reduction reported to date, suggesting a highly reactive MoVI center. (Oc)2Mo(=O)2@C catalyzes the transesterification of a variety of esters and triglycerides with ethanol, exhibiting high activity at moderate temperatures (60-90 °C) and with negligible deactivation. (Oc)2Mo(=O)2@C is resistant to water and can be recycled at least three times with no loss of activity. The transesterification reaction is determined experimentally to be first order in [ethanol] and first order in [Mo] with Δ;H? = 10.5(8) kcal mol-1 and Δ;S? = -32(2) eu. The low energy of activation is consistent with the moderate conditions needed to achieve rapid turnover. This highly active carbon-supported single-site molybdenum dioxo species is thus an efficient, robust, and low-cost catalyst with significant potential for transesterification processes.
Mouat, Aidan R.,Lohr, Tracy L.,Wegener, Evan C.,Miller, Jeffrey T.,Delferro, Massimiliano,Stair, Peter C.,Marks, Tobin J.
p. 6762 - 6769
(2016/10/18)

A convenient synthesis of a porphyrin cross-linked polymer, its application as a size selective heterogeneous catalyst and a comparison with a porphyrin-cored hyperbranched polymer
This paper describes how the polymeric structure and environment surrounding supported catalysts can be used to affect the product outcome from a reaction. As well as reporting a size/shape selectivity, we also describe a significant effect on product distribution. Specifically, how the polymeric environment can favour or disfavour particular products. As such, these results illustrate how it may be possible to target more or less of a specific compound (from a possible mix) by careful choice of the polymer architecture surrounding a catalyst.
Twyman, Lance J.,Zheng, Xinwei
p. 617 - 623
(2016/06/09)

Cytochrome P450 oxygenases
Nucleic acids encoding cytochrome P450 variants are provided. The cytochrome P450 variants of have a higher alkane-oxidation capability, alkene-oxidation capability, and/or a higher organic-solvent resistance than the corresponding wild-type or parent cytochrome P450 enzyme. A preferred wild-type cytochrome P450 is cytochrome P450 BM-3. Preferred cytochrome P450 variants include those having an improved capability to hydroxylate alkanes and epoxidate alkenes comprising less than 8 carbons, and have amino acid substitutions corresponding to V78A, H236Q, and E252G of cytochrome P450 BM-3. Preferred cytochrome P450 variants also include those having an improved hydroxylation activity in solutions comprising co-solvents such as DMSO and THF, and have amino acid substitutions corresponding to T235A, R471A, E494K, and S1024E of cytochrome P450 BM-3.
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Page/Page column 25; 26

(2016/05/24)

Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides
Nickel(ii) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and reused for subsequent experiments with consistent catalytic activity.
Escorihuela, Jorge,Altava, Beln,Burguete, M. Isabel,Luis, Santiago V.
p. 14653 - 14662
(2015/02/19)

1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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(2015/03/03)

Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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(2015/03/03)

Revisiting cytochrome P450-mediated oxyfunctionalization of linear and cyclic alkanes
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.
supporting information
p. 118 - 130
(2015/01/30)

Transfer hydrogenation employing ethylene diamine bisborane in water and Pd- and ru-nanoparticles in ionic liquids
Herein we demonstrate the use of ethylenediamine bisborane (EDAB) as a suitable hydrogen source for transfer hydrogenation reactions on C-C double bonds mediated by metal nanoparticles. Moreover, EDAB also acts as a reducing agent for carbonyl functionalities in water under metal-free conditions.
Sahler, Sebastian,Scott, Martin,Gedig, Christian,Prechtl, Martin H.G.
p. 17058 - 17069
(2015/12/01)

Co-oxidation of octane and benzaldehyde using molecular oxygen with Au-Pd/carbon prepared by sol-immobilisation
The selective oxidation of linear alkanes with molecular oxygen under mild conditions remains a challenging topic in the field of catalysis. In this study we investigate the co-oxidation of C-H bonds in substrates with different relative reactivities, the aim being to couple the oxidised products in situ to form the corresponding esters. Initial attempts were made to co-oxidise octane with toluene to form octyl benzoate using Au-Pd catalysts. During the study the oxidation of octane in the presence of benzaldehyde, an oxidation product of toluene, was also investigated in order to demonstrate the potential feasibility of the reaction. This work summarises our attempts to show whether a co-oxidation system could be an effective way to oxidise linear alkanes.
Peneau, Virginie,Shaw, Greg,Freakley, Simon J.,Forde, Michael M.,Dimitratos, Nikolaos,Jenkins, Robert L.,Taylor, Stuart H.,Hutchings, Graham J.
p. 3953 - 3959
(2015/08/03)

Cobalt aminodiphosphine complexes as catalysts in the oxidation of n-octane
Two types of cobalt aminodiphosphine complexes have been synthesized and characterized by IR spectroscopy, elemental analyses and single crystal X-ray diffraction. These are [Ph2PN(R)PPh2]CoCl2, 1 and [Ph2P(CH2)2N(R)(CH2)2PPh2]CoCl2, 2 where R = C6H11 (a); C5H11 (b); C3H7 (c). The functional groups on the nitrogen atom (R) were varied from a cyclohexyl ring, to n-pentyl alkyl chain, to an iso-propyl branched substituent. Complexes 2a and 2c were analyzed using single crystal X-ray diffraction. The geometry around the metal centers in 2a and 2c were distorted tetrahedral. All the complexes showed good activity as catalysts for the oxidation of n-octane using tert-butyl hydroperoxide (TBHP) as the oxidant. The complex bearing the flexible ligand backbone with the cyclohexyl substituent on the nitrogen atom was the most active and showed high selectivity towards ketones with 2-octanone being the dominant product.
Naicker, Dunesha,Friedrich, Holger B.,Omondi, Bernard
p. 63123 - 63129
(2015/08/06)