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Controlling product selectivity with nanoparticle composition in tandem chemo-biocatalytic styrene oxidation
The combination of heterogeneous catalysis and biocatalysis into one-pot reaction cascades is a potential approach to integrate enzymatic transformations into existing chemical infrastructure. Peroxygenases, which can achieve clean C-H activation, are ideal candidates for incorporation into such tandem systems, however a constant supply of low-level hydrogen peroxide (H2O2) is required. The use of such enzymes at industrial scale will likely necessitate thein situgeneration of the oxidant from cheap and widely available reactants. We show that combing heterogeneous catalysts (AuxPdy/TiO2) to produce H2O2in situfrom H2and air, in the presence of an evolved unspecific peroxygenase fromAgrocybe aegerita(PaDa-I variant) yields a highly active cascade process capable of oxidizing alkyl and alkenyl substrates. In addition, the tandem process operates under mild reaction conditions and utilizes water as the only solvent. When alkenes such as styrene are subjected to this tandem oxidation process, divergent reaction pathways are observed due to the competing hydrogenation of the alkene by palladium rich nanoparticles in the presence of H2. Each pathway presents opportunities for value added products. Product selectivity was highly sensitive to the rate of reduction compared to hydrogen peroxide delivery. Here we show that some control over product selectivity may be exerted by careful selection of nanoparticle composition.
Alcalde, Miguel,Brehm, Joseph,Davies, Thomas E.,Freakley, Simon J.,Harrison, Susan T. L.,Hutchings, Graham J.,Kotsiopoulos, Athanasios,Lewis, Richard J.,Morgan, David J.,Opperman, Diederik J.,Smit, Martha S.,Wilbers, Derik,van Marwijk, Jacqueline
supporting information
p. 4170 - 4180
(2021/06/17)

Photo-Induced Dihydroxylation of Alkenes with Diacetyl, Oxygen, and Water
Herein reported is a photo-induced production of vicinal diols from alkenes under mild reaction conditions. The present dihydroxylation method using diacetyl (= butane-2,3-dione), oxygen, and water dispenses with toxic reagents and intractable waste generation.
Masuda, Yusuke,Ikeshita, Daichi,Murakami, Masahiro
(2021/02/09)

Iodine-Initiated Dioxygenation of Aryl Alkenes Using tert-Butylhydroperoxides and Water: A Route to Vicinal Diols and Bisperoxides
An environment-friendly and efficient dioxygenation of aryl alkenes for the construction of vicinal diols has been developed in water with iodine as the catalyst and tert-butylhydroperoxides (TBHPs) as the oxidant. The protocol was efficient, sustainable, and operationally simple. Detailed mechanistic studies indicated that one of the hydroxyl groups is derived from water and the other one is derived from TBHP. Additionally, the bisperoxides could be obtained in good yields with iodine as the catalyst, Na2CO3 as the additive, and propylene carbonate as the solvent, instead.
Gao, Xiaofang,Lin, Jiani,Zhang, Li,Lou, Xinyao,Guo, Guanghui,Peng, Na,Xu, Huan,Liu, Yi
p. 15469 - 15480
(2021/11/16)

Absolute stereochemical determination of 1,2-diols via complexation with dinaphthyl borinic acid
Rapid derivatization of chiral 1,2-diols with dinaphthyl borinic acid (DBA) leads to a cyclic boronate, enabling the absolute stereochemical prediction via exciton-coupled circular dichroic (ECCD) of the naphthyl groups. Aryl- and alkyl-substituted 1,2-diols derivatized with DBA yield a predictable ECCD, which is also in agreement with theoretical predictions derived from computationally minimized structures.
Torabi Kohlbouni, Saeedeh,Sarkar, Aritra,Zhang, Jun,Li, Xiaoyong,Borhan, Babak
supporting information
p. 817 - 823
(2020/03/26)

Racemic or enantioselective osmium-catalyzed dihydroxylation of olefins under near-neutral conditions
K3Fe(CN)6 and NaIO4 serve as catalytic co-oxidants for osmium-catalyzed dihydroxylations that are performed under near-neutral conditions with K2S2O8 as the stoichiometric oxidant and Na2HPO4 as the base. By using either quinuclidine or hydroquinidine 1,4-phthalazinediyl ether [(DHQD)2Phal], good yields of racemic or enantioenriched diols are obtained. This simple, biphasic procedure offers advantages over other neutral dihydroxylation protocols that use N-methylmorpholine oxide as the stoichiometric oxidant, by suppressing the secondary catalytic cycle that leads to reduced enantioselectivities. The utility of the procedure, which is nicely suited for base-labile starting materials or products, is demonstrated by performing the dihydroxylation in the presence of an aliphatic aldehyde moiety.
Blumberg, Shawn,Martin, Stephen F.
p. 7 - 14
(2020/10/08)

GaN nanowires as a reusable photoredox catalyst for radical coupling of carbonyl under blacklight irradiation
Employing photo-energy to drive the desired chemical transformation has been a long pursued subject. The development of homogeneous photoredox catalysts in radical coupling reactions has been truly phenomenal, however, with apparent disadvantages such as the difficulty in separating the catalyst and the frequent requirement of scarce noble metals. We therefore envisioned the use of a hyper-stable III-V photosensitizing semiconductor with a tunable Fermi level and energy band as a readily isolable and recyclable heterogeneous photoredox catalyst for radical coupling reactions. Using the carbonyl coupling reaction as a proof-of-concept, herein, we report a photo-pinacol coupling reaction catalyzed by GaN nanowires under ambient light at room temperature with methanol as a solvent and sacrificial reagent. By simply tuning the dopant, the GaN nanowire shows significantly enhanced electronic properties. The catalyst showed excellent stability, reusability and functional tolerance. All reactions could be accomplished with a single piece of nanowire on Si-wafer. This journal is
Botton, Gianluigi,Cen, Yunen,Cheng, Shaobo,Li, Chao-Jun,Liu, Mingxin,Mi, Zetian,Rashid, Roksana T.,Tan, Lida
p. 7864 - 7870
(2020/08/19)

Isothiourea-Catalyzed Acylative Kinetic Resolution of Tertiary α-Hydroxy Esters
A highly enantioselective isothiourea-catalyzed acylative kinetic resolution (KR) of acyclic tertiary alcohols has been developed. Selectivity factors of up to 200 were achieved for the KR of tertiary alcohols bearing an adjacent ester substituent, with both reaction conversion and enantioselectivity found to be sensitive to the steric and electronic environment at the stereogenic tertiary carbinol centre. For more sterically congested alcohols, the use of a recently-developed isoselenourea catalyst was optimal, with equivalent enantioselectivity but higher conversion achieved in comparison to the isothiourea HyperBTM. Diastereomeric acylation transition state models are proposed to rationalize the origins of enantiodiscrimination in this process. This KR procedure was also translated to a continuous-flow process using a polymer-supported variant of the catalyst.
Greenhalgh, Mark D.,Laina-Martín, Víctor,Neyyappadath, Rifahath M.,Qu, Shen,Smith, Andrew D.,Smith, Samuel M.
supporting information
p. 16572 - 16578
(2020/09/09)

HFIP-promoted synthesis of substituted tetrahydrofurans by reaction of epoxides with electron-rich alkenes
In the present work, the employment of fluorinated alcohols, specifically 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), as solvent and promoter of the catalyst-free synthesis of substituted tetrahydrofuranes through the addition of electron-rich alkenes to epoxydes is described. The unique properties of this fluorinated alcohol, which is very different from their non-fluorinated analogs, allows carrying out this new straightforward protocol under smooth reaction conditions affording the corresponding adducts in moderate yields in the majority of cases. Remarkably, this methodology has allowed the synthesis of new tetrahydrofuran-based spiro compounds as well as tetrahydrofurobenzofuran derivatives. The scope and limitations of the process are also discussed. Mechanistic studies were also performed pointing towards a purely ionic or a SN2-type process depending on the nucleophilicity of the alkene employed.
Baeza, Alejandro,Llopis, Natalia
(2020/08/17)

Oxidative Cleavage of Alkene C=C Bonds Using a Manganese Catalyzed Oxidation with H2O2 Combined with Periodate Oxidation
A one-pot multi-step method for the oxidative cleavage of alkenes to aldehydes/ketones under ambient conditions is described as an alternative to ozonolysis. The first step is a highly efficient manganese catalyzed epoxidation/cis-dihydroxylation of alkenes. This step is followed by an Fe(III) assisted ring opening of the epoxide (where necessary) to a 1,2-diol. Carbon–carbon bond cleavage is achieved by treatment of the diol with sodium periodate. The conditions used in each step are not only compatible with the subsequent step(s), but also provide for increased conversion compared to the equivalent reactions carried out on the isolated intermediate compounds. The described procedure allows for carbon–carbon bond cleavage in the presence of other alkenes, oxidation sensitive moieties and other functional groups; the mild conditions (r.t.) used in all three steps make this a viable general alternative to ozonolysis and especially for use under flow or continuous batch conditions.
Mecozzi, Francesco,Dong, Jia Jia,Angelone, Davide,Browne, Wesley R.,Eisink, Niek N. H. M.
supporting information
p. 7151 - 7158
(2019/11/16)

Ligand-Controlled Regiodivergent Enantioselective Rhodium-Catalyzed Alkene Hydroboration
Regiocontrol in the rhodium-catalyzed boration of vinyl arenes is typically dominated by the presence of the conjugated aryl substituent. However, small differences in TADDOL-derived chiral monophosphite ligands can override this effect and direct rhodium-catalyzed hydroboration of β-aryl and β-heteroaryl methylidenes by pinacolborane to selectively produce either chiral primary or tertiary borated products. The regiodivergent behavior is coupled with enantiodivergent addition of the borane. The nature of the TADDOL backbone substituents and that of the phosphite moiety function synergistically to direct the sense and extent of regioselectivity and enantioinduction. Twenty substrates are shown to undergo each reaction mode with regioselectivity values reaching greater than 20:1 and enantiomer ratios reaching up to 98:2. A variety of subsequent transformations illustrate the potential utility of each product.
Bochat, Andrew J.,Shoba, Veronika M.,Takacs, James M.
p. 9434 - 9438
(2019/06/27)

Selective catalytic oxidation of aromatic substrates employing mononuclear copper(II) catalyst with H2O2
A novel mononuclear complex [LCuCl2(H2O)]CH2Cl2 (L = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) was synthesized and characterized by elemental analysis, ultraviolet visible (UV–Vis) spectrum, and fourier transform infrared spectroscopy (FTIR). The single-crystal X-ray diffraction structure analysis of the complex revealed that the copper atom was octahedrally coordinated. The catalytic potential of this complex was examined by the oxidation reaction of various aromatic substrates, such as styrene, ethyl benzene, α-methyl styrene, and benzyl alcohol. The oxidation reactions were carried out in acetonitrile with H2O2 and catalytic amounts of [LCuCl2(H2O)] at 70 °C. The catalyst exhibited good catalytic activity in the oxidation of benzyl alcohol (97.50% conv. in 1 h; TONs = 341.25), α-methyl styrene (97.72% conv. in 4 h; TONs = 342.02) and methyl styrene (99.00% conv. in 8 h; TONs = 346.50). The major products were 96.07% benzoic acid from benzyl alcohol, 93.54% acetophenone from α-methyl styrene and 86.38% benzaldehyde from styrene, respectively. A plausible catalytic mechanism involving an active cation [LCu2+] and an epoxy intermediate was proposed based the results of time-dependent electrospray ionization mass spectrometry (ESI-MS) of the reaction mixture.
Wu, Chengcheng,Liu, Bin,Geng, Xin,Zhang, Zhenyu,Liu, Shenghua,Hu, Quanyuan
p. 334 - 341
(2018/11/30)

Syn-dihydroxylation of alkenes using a sterically demanding cyclic diacyl peroxide
The syn-dihydroxylation of alkenes is a highly valuable reaction in organic synthesis. Cyclic acyl peroxides (CAPs) have emerged recently as promising candidates to replace the commonly employed toxic metals for this purpose. Here, we demonstrate that the structurally demanding cyclic peroxide spiro[bicyclo[2.2.1]heptane-2,4′-[1,2]dioxolane]-3′,5′-dione (P4) can be effectively used for the syn-dihydroxylation of alkenes. Reagent P4 also shows an improved selectivity for dihydroxylation of alkenes bearing β-hydrogens as compared to other CAPs, where both diol and allyl alcohol products compete with each other. Furthermore, the use of enantiopure P4 (labeled P4′) demonstrates the potential of P4′ for a metal-free asymmetric syn-dihydroxylation of alkenes.
Pilevar, Afsaneh,Hosseini, Abolfazl,Becker, Jonathan,Schreiner, Peter R.
p. 12377 - 12386
(2019/10/11)

Semirational Engineering of the Naphthalene Dioxygenase from Pseudomonas sp. NCIB 9816-4 towards Selective Asymmetric Dihydroxylation
Enzyme-catalyzed asymmetric dihydroxylation is a powerful tool for the selective oxyfunctionalization of various organic compounds. By applying Rieske non-heme dioxygenases (ROs), molecular oxygen and a reduction equivalent are needed for the generation of vicinal cis-diols. We report a comprehensive mutagenesis study of the active site of the naphthalene dioxygenase from Pseudomonas sp. NCIB 9816-4 comprising 62 variants. We aimed to understand the important structure–function relationships by investigating different substituted arene substrates and the geometry of the active site. Introducing single-point mutations at positions F202, A206, V260, H295, F352, and L307 resulted in drastic shifts in the reaction specificity, regioselectivity, and stereoselectivity (≥90 %) while maintaining the residual activity towards the natural substrate naphthalene.
Halder, Julia M.,Nestl, Bettina M.,Hauer, Bernhard
p. 178 - 182
(2017/12/26)

Thiyl radical promoted chemo- and regioselective oxidation of CC bonds using molecular oxygen: Via iron catalysis
The first example of the thiyl radical promoted ligand-free iron-catalyzed oxidative cleavage of alkenes using molecular oxygen (1 atm) has been developed. The reaction proceeds under mild reaction conditions with high efficiency and high chemo- and regioselectivity. It features a broad substrate scope and excellent functional group compatibility, enabling facile access to valuable molecules for application in medicinal chemistry. Preliminary mechanistic studies reveal that a vital intermediate dioxetane might be involved in the reaction and a thiyl radical plays a synergistic role in facilitating the selective oxidation of the CC bond.
Xiong, Baojian,Zeng, Xiaoqin,Geng, Shasha,Chen, Shuo,He, Yun,Feng, Zhang
supporting information
p. 4521 - 4527
(2018/10/17)

Synthesis and stereoselective evaluation of a (1R)-(–)-myrtenal-derived pseudo C2-symmetric dodecaheterocycle as a potential heterofunctional chiral auxiliary
The synthesis and diastereoselective performance of the pseudo C2-symmetric dodecaheterocycle 3 in nucleophilic and electrophilic reactions are reported. Compound 3 proved to be a highly diastereoselective template to generate a pair of enantiomeric moieties within its structure in a programmed manner. Hence, this study describes the synthesis of a novel potential heterobifunctional chiral auxiliary.
Sánchez-Chávez, Anahí C.,Elena Vargas-Díaz, Ma.,Ontiveros-Rodríguez, Julio C.,Pérez-Estrada, Salvador,Flores-Bernal, Gustavo G.,Mendoza-Espinosa, Daniel,álvarez-Hernández, Alejandro,Delgado, Francisco,Tamariz, Joaquín,Gerardo Zepeda-Vallejo
supporting information
p. 4437 - 4441
(2018/11/23)

Green Organocatalytic Dihydroxylation of Alkenes
An inexpensive, green, metal-free one-pot procedure for the dihydroxylation of alkenes is described. H2O2 and 2,2,2-trifluoroacetophenone were employed as the oxidant and organocatalyst, respectively, in this highly sustainable protocol in which a variety of homoallylic alcohols, aminoalkenes, and simple alkenes were converted into the corresponding polyalcohols in good to excellent yields. This process takes advantage of an epoxidation reaction followed by an acidic treatment in which water participates in the ring opening of the in situ prepared epoxide to lead to the desired product.
Theodorou, Alexis,Triandafillidi, Ierasia,Kokotos, Christoforos G.
p. 1502 - 1509
(2017/04/01)

Disulfide-Catalyzed Visible-Light-Mediated Oxidative Cleavage of C=C Bonds and Evidence of an Olefin–Disulfide Charge-Transfer Complex
A photocatalytic method for the aerobic oxidative cleavage of C=C bonds has been developed. Electron-rich aromatic disulfides were employed as photocatalyst. Upon visible-light irradiation, typical mono- and multi-substituted aromatic olefins could be converted into ketones and aldehydes at ambient temperature. Experimental and computational studies suggest that a disulfide–olefin charge-transfer complex is possibly responsible for the unconventional dissociation of S?S bond under visible light.
Deng, Yuchao,Wei, Xiao-Jing,Wang, Hui,Sun, Yuhan,No?l, Timothy,Wang, Xiao
supporting information
p. 832 - 836
(2017/01/14)

Copper(II) Schiff Base Complex Immobilized on Superparamagnetic Fe3O4@SiO2 as a Magnetically Separable Nanocatalyst for Oxidation of Alkenes and Alcohols
A new heterogeneous catalyst containing a copper(II) Schiff base complex covalently immobilized on the surface of silica-coated Fe3O4 nanoparticles (Fe3O4@SiO2-Schiff base-Cu(II)) was synthesized. Characterization of this catalyst was performed using various techniques. The catalytic potential of the catalyst was investigated for the oxidation of various alkenes (styrene, α-methylstyrene, cyclooctene, cyclohexene and norbornene) and alcohols (benzyl alcohol, 3-methoxybenzyl alcohol, 3-chlorobenzyl alcohol, benzhydrol and n-butanol) using tert-butyl hydroperoxide as oxidant. The catalytic investigations revealed that Fe3O4@SiO2-Schiff base-Cu(II) was especially efficient for the oxidation of norbornene and benzyl alcohol. The results showed that norbornene epoxide and benzoic acid were obtained with 100 and 87% selectivity, respectively. Moreover, simple magnetic recovery from the reaction mixture and reuse for several times with no significant loss in catalytic activity were other advantages of this catalyst.
Sarkheil, Marzieh,Lashanizadegan, Maryam
(2017/09/26)

Developing a Bench-Scale Green Diboration Reaction toward Industrial Application
We report a new methodology for the organocatalytic diboration reaction using inexpensive, sustainable, nontoxic, commercially available halogen salts. This is an educative manuscript for the transformation of laboratory scale reactions into a sustainable approach of appeal to industry.
Farre, Albert,Briggs, Rachel,Pubill-Ulldemolins, Cristina,Bonet, Amadeu
p. 4775 - 4782
(2017/10/27)

Visible light-promoted dihydroxylation of styrenes with water and dioxygen
An efficient visible light promoted metal-free dihydroxylation of styrenes with water and dioxygen has been developed for the construction of vicinal alcohols. The protocol was operationally simple with a broad substrate scope. The mechanistic studies demonstrated that one of the hydroxyl groups came from water and the other one came from molecular oxygen. Additionally, the β-alkyoxy alcohols could also be obtained using a similar strategy.
Yang, Bo,Lu, Zhan
p. 12634 - 12637
(2017/12/02)

A Well-Defined Osmium-Cupin Complex: Hyperstable Artificial Osmium Peroxygenase
Thermally stable TM1459 cupin superfamily protein from Thermotoga maritima was repurposed as an osmium (Os) peroxygenase by metal-substitution strategy employing the metal-binding promiscuity. This novel artificial metalloenzyme bears a datively bound Os ion supported by the 4-histidine motif. The well-defined Os center is responsible for not only the catalytic activity but also the thermodynamic stability of the protein folding, leading to the robust biocatalyst (Tm ≈ 120 °C). The spectroscopic analysis and atomic resolution X-ray crystal structures of Os-bound TM1459 revealed two types of donor sets to Os center with octahedral coordination geometry. One includes trans-dioxide, OH, and mer-three histidine imidazoles (O3N3 donor set), whereas another one has four histidine imidazoles plus OH and water molecule in a cis position (O2N4 donor set). The Os-bound TM1459 having the latter donor set (O2N4 donor set) was evaluated as a peroxygenase, which was able to catalyze cis-dihydroxylation of several alkenes efficiently. With the low catalyst loading (0.01% mol), up to 9100 turnover number was achieved for the dihydroxylation of 2-methoxy-6-vinyl-naphthalene (50 mM) using an equivalent of H2O2 as oxidant at 70 °C for 12 h. When octene isomers were dihydroxylated in a preparative scale for 5 h (2% mol cat.), the terminal alkene octene isomers was converted to the corresponding diols in a higher yield as compared with the internal alkenes. The result indicates that the protein scaffold can control the regioselectivity by the steric hindrance. This protein scaffold enhances the efficiency of the reaction by suppressing disproportionation of H2O2 on Os reaction center. Moreover, upon a simple site-directed mutagenesis, the catalytic activity was enhanced by about 3-fold, indicating that Os-TM1459 is evolvable nascent osmium peroxygenase.
Fujieda, Nobutaka,Nakano, Takumi,Taniguchi, Yuki,Ichihashi, Haruna,Sugimoto, Hideki,Morimoto, Yuma,Nishikawa, Yosuke,Kurisu, Genji,Itoh, Shinobu
supporting information
p. 5149 - 5155
(2017/05/04)

Mechanistically Driven Development of an Iron Catalyst for Selective Syn-Dihydroxylation of Alkenes with Aqueous Hydrogen Peroxide
Product release is the rate-determining step in the arene syn-dihydroxylation reaction taking place at Rieske oxygenase enzymes and is regarded as a difficult problem to be resolved in the design of iron catalysts for olefin syn-dihydroxylation with potential utility in organic synthesis. Toward this end, in this work a novel catalyst bearing a sterically encumbered tetradentate ligand based in the tpa (tpa = tris(2-methylpyridyl)amine) scaffold, [FeII(CF3SO3)2(5-tips3tpa)], 1 has been designed. The steric demand of the ligand was envisioned as a key element to support a high catalytic activity by isolating the metal center, preventing bimolecular decomposition paths and facilitating product release. In synergistic combination with a Lewis acid that helps sequestering the product, 1 provides good to excellent yields of diol products (up to 97% isolated yield), in short reaction times under mild experimental conditions using a slight excess (1.5 equiv) of aqueous hydrogen peroxide, from the oxidation of a broad range of olefins. Predictable site selective syn-dihydroxylation of diolefins is shown. The encumbered nature of the ligand also provides a unique tool that has been used in combination with isotopic analysis to define the nature of the active species and the mechanism of activation of H2O2. Furthermore, 1 is shown to be a competent synthetic tool for preparing O-labeled diols using water as oxygen source.
Borrell, Margarida,Costas, Miquel
supporting information
p. 12821 - 12829
(2017/09/25)

Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactions
Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon-carbon double bonds. First, reductive O2 activation induces selective oxidative cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of "omic" technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.
Lopez, Sarah,Rondot, Laurianne,Leprêtre, Chloé,Marchi-Delapierre, Caroline,Ménage, Stéphane,Cavazza, Christine
supporting information
p. 17994 - 18002
(2017/12/26)

Combined Photoredox and Lewis Acid Catalyzed α-Hydroxyalkylation of Cyclic Ethers with Aromatic Ketones
The photochemically induced coupling of aromatic ketones with cyclic ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane was studied. Direct photolysis of the substrates with UV-A light centered at 350 nm does not lead to photoinduced hydrogen transfer whereas the addition of a mixture of the Lewis acid catalysts Ti(OiPr)4 and BF3 enables the formation of the hydroxyalkylation products.
Reckenth?ler, Melissa,Neud?rfl, J?rg-M.,Zorlu, Elif,Griesbeck, Axel G.
p. 7211 - 7216
(2016/09/04)

Production Of Enantiopure alpha-Hydroxy Carboxylic Acids From Alkenes By Cascade Biocatalysis
The invention provides compositions comprising an alkene epoxidase and a selective epoxide hydrolase, such as a recombinant microorganism comprising a first heterologous nucleic acid encoding an alkene epoxidase and a second heterologous nucleic acid encoding a selective epoxide hydrolase. Exemplary alkene epoxidases include StyAB, while exemplary selective epoxide hydrolases include epoxide hydrolases from Sphingomonas, Solanum tuberosum, or Aspergillus. The invention also provides non-toxic methods of making enantiomerically pure vicinal diols or enantiomerically pure alpha-hydroxy carboxylic acids using these compositions and microorganisms.
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Paragraph 0097-0099

(2016/05/02)

Photocatalytic Oxygenation of Sulfide and Alkenes by Trinuclear Ruthenium Clusters
Trinuclear Ru cluster photocatalysts that contain two Ru(II) photosensitizers and a Ru(II) reaction center are prepared, and their activity in the photocatalytic oxygenation of a sufide and alkenes is investigated. Photoirradiation (visible light) and the use of a Co salt ([Co(NH3)5Cl]Cl2, as an electron acceptor) are found to be essential for these catalytic reactions. The O atom of the water solvent (pH 6.8) is transferred to the substrate by a stepwise electron transfer and deprotonation of an aqua ligand at the reaction center. Through these processes, the aqua ligand coordinated at the reaction center is converted to a RuV=O species, which is the active intermediate in the sulfide and alkene oxygenation.
Phungsripheng, Siwas,Kozawa, Kazuyuki,Akita, Munetaka,Inagaki, Akiko
p. 3750 - 3758
(2016/05/19)

Amine Catalysis for the Organocatalytic Diboration of Challenging Alkenes
The generation of in situ sp2–sp3diboron adducts has revolutionised the synthesis of organoboranes. Organocatalytic diboration reactions have represented a milestone in terms of unpredictable reactivity of these adducts. However, current methodologies have limitations in terms of substrate scope, selectivity and functional group tolerance. Here a new methodology based on the use of simple amines as catalyst is reported. This methodology provides a completely selective transformation overcoming current substrate scope and functional/protecting group limitations. Mechanistic studies have been included in this report.
Farre, Albert,Soares, Kaline,Briggs, Rachel A.,Balanta, Angelica,Benoit, David M.,Bonet, Amadeu
supporting information
p. 17552 - 17556
(2016/11/28)

Selective oxidation of styrene catalyzed by cerium-doped cobalt ferrite nanocrystals with greatly enhanced catalytic performance
The rare earth metal Ce-doped cobalt ferrite samples CexCo1?xFe2O4 (x?=?0.1, 0.3, 0.5) were prepared by the sol–gel autocombustion route. The as-prepared samples were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, ICP–atomic emission spectroscopy, and N2 physisorption. Their catalytic performance was evaluated in oxidation of styrene using hydrogen peroxide (30%) as oxidant. Compared with pristine CoFe2O4, the Ce-doped samples were found to be more efficient catalysts for the oxidation of styrene to benzaldehyde, with greatly enhanced catalytic performance. Especially, when Ce0.3Co0.7Fe2O4 was used as catalyst, 90.3% styrene conversion and 91.5% selectivity for benzaldehyde were obtained at 90?°C for 9?h reaction. The catalyst can be magnetically separated easily for reuse, and no obvious loss of activity was observed when it was reused in five consecutive runs.
Tong, Jinhui,Li, Wenyan,Bo, Lili,Wang, Huan,Hu, Yusen,Zhang, Zhixia,Mahboob, Abdulla
p. 474 - 481
(2016/11/18)

Epoxy compound (by machine translation)
[Problem] safe, efficient and economical, and high purity of the objective compound, epoxy compound production. (1) represented by the general formula [a], and, more a 300 molecular weight styrene compound, tungsten compound in the presence of the onium salts, hydrogen peroxide is reacted with, of the general formula (1) carbon - carbon double bond contained in the compound represented by the epoxy compound can be oxidized. (A is an electron withdrawing group having a benzene ring. R1 The, 1 - 20 carbon atoms of alkyl group which may have a substituent. )[Drawing] no (by machine translation)
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(2017/07/31)

Cooperative catalysis of cyclic carbonate ring opening: Application towards non-isocyanate polyurethane materials
The reaction between cyclic carbonates and amines to produce hydroxyurethanes is an important alternative to current urethane chemistry. In order to address the issue of slow reaction rates, an efficient ring opening of cyclic carbonates with amines has been achieved utilizing cooperative catalysis. A new Lewis acid/Lewis base combination substantially decreases the reaction times for small molecule systems to reach complete conversion. Although triazabicyclodecene (TBD) has a substantial impact on the reaction rate, the addition of lithium triflate (LiOTf) as a co-catalyst allows for the fastest ring opening reported in the current literature. Cooperative catalysis is also applied to the synthesis of polymers containing hydroxyurethane linkages and is able to achieve rapid conversion of the bis-cyclic carbonate and diamine precursors when compared with the uncatalyzed reaction.
Lombardo, Vince M.,Dhulst, Elizabeth A.,Leitsch, Emily K.,Wilmot, Nathan,Heath, William H.,Gies, Anthony P.,Miller, Matthew D.,Torkelson, John M.,Scheidt, Karl A.
supporting information
p. 2791 - 2795
(2015/05/05)

A simple primary amine catalyst for enantioselective α-hydroxylations and α-fluorinations of branched aldehydes
A new primary amine catalyst for the asymmetric α-hydroxylation and α-fluorination of α-branched aldehydes is described. The products of the title transformations are generated in excellent yields with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for α-functionalizations. Promising initial results in α-amination and α-chlorination reactions support this hypothesis.
Witten, Michael R.,Jacobsen, Eric N.
supporting information
p. 2772 - 2775
(2015/06/16)

Homogeneous catalytic oxidation of styrene and styrene derivatives with hydrogen peroxide in the presence of transition metal-substituted polyoxotungstates
The tetrabutylammonium (TBA) salts of the Keggin-type polyoxotungstates with general formula [XW11M(H2O)O39](n-m)-, where X = P, B or Si and M = Mn, Fe or Co, were evaluated as catalysts in the oxidation of styrene, α-methylstyrene, p-methylstyrene, α,p-dimethylstyrene, p-chlorostyrene, p-nitrostyrene, and p-methoxystyrene under mild conditions, using aqueous H2O2 as an eco-sustainable oxidant. In this study, the influence of the catalysts and of the different styrene substituents on the oxidation reaction profile was evaluated in terms of conversion and selectivity. For all the performed catalytic studies, the main product results from the oxidative cleavage of the vinyl double bond, except in the case of the oxidation of p-methoxystyrene catalysed by BW11Mn, for which p-methoxyphenol is the main product. The catalysts BW11Mn and SiW11Co give rise to 100% conversion for almost all of the substrates, excluding p-methoxystyrene and p-nitrostyrene for both catalysts and α,p-dimethylstyrene only in the case of BW11Mn. The selectivity for C=C cleavage products resulting from the oxidative cleavage of the vinyl double bond can be as high as 98%, reaching 98% conversion for p-nitrostyrene when SiW11Co was used as a catalyst. Possible pathways are discussed and the oxidation of a few presumed intermediates was carried out. The systematic study of several substituted styrene derivatives suggests a possible reactivity order for these compounds in the catalytic system considered.
Duarte, Tiago A. G.,Estrada, Ana C.,Simes, Mrio M. Q.,Santos, Isabel C. M. S.,Cavaleiro, Ana M. V.,Neves, M. Graca P. M. S.,Cavaleiro, Jos A. S.
p. 351 - 363
(2015/02/18)

Vanadyl species-catalyzed complementary β-oxidative carbonylation of styrene derivatives with aldehydes
A series of oxometallic species and metal acetylacetonates (acac) was examined as catalysts for oxidative carbonylation of styrene with benzaldehyde using t-butylhydroperoxide as the co-oxidant in warm acetonitrile. Among them, VO((acac)2 and vanadyl(iv) chloride were found to be the only catalyst class to achieve cross-coupling processes by judiciously tuning the ligand electronic attributes, leading to β-hydroxylation- and β-peroxidation-carbonylation of styrene, respectively, in a complementary manner. Mechanistic studies indicated that vanadyl-associated acyl radicals generated by t-butoxy radical-assisted, homolytic cleavage of the aldehyde C-H bond were involved in tandem processes with an exclusive syn diastereoselectivity in the case of β-methylstyrene. This journal is
Yang, Wen-Chieh,Weng, Shiue-Shien,Ramasamy, Anandhan,Rajeshwaren, Gobi,Liao, Yi-Ya,Chen, Chien-Tien
supporting information
p. 2385 - 2392
(2015/03/04)

Mechanistic Insights into Enantioselective C-H Photooxygenation of Aldehydes via Enamine Catalysis
Organocatalytic photooxygenation of aldehydes at the α-position proceeds via enamine catalysis, though enamines should be easily oxidized by singlet oxygen respectively to amides and carbonyl compounds. Moreover, the formation of a zwitterionic enamine peroxide intermediate was postulated based on experimental and theoretical data. The reaction affords desired diols (after in situ reduction) in a decent yield and (S)- or (R)-enantioselectivity depending on a catalyst used. The (S)-enantiomer predominated in imidazolidinone-catalyzed reactions, while prolineamides assured the formation of the (R)-stereoisomer. DFT calculation suggests that the enamine-oxygen complex with the lowest energy has the E,s-cis conformation for the prolineamide derivative and E,s-trans for the imidazolidinone catalyst, explaining the opposite stereoselectivity in the photooxygenation reaction.
Walaszek, Dominika J.,Rybicka-Jasińska, Katarzyna,Smoleń, Sabina,Karczewski, Maksymilian,Gryko, Dorota
supporting information
p. 2061 - 2070
(2015/06/23)

Resolution of diols via catalytic asymmetric acetalization
A highly enantioselective kinetic resolution of diols via asymmetric acetalization has been achieved using a chiral confined imidodiphosphoric acid catalyst. The reaction is highly efficient for the resolution of tertiary alcohols, giving selectivity factors of up to >300. Remarkably, even in cases where the selectivity factors are only moderate, highly enantioenriched diols are obtained via a stereodivergent resolution to diastereomeric acetals.
Kim, Ji Hye,ori, Ilija,Palumbo, Chiara,List, Benjamin
supporting information
p. 1778 - 1781
(2015/03/04)

Homogeneous and heterogeneous photoredoxcatalyzed hydroxymethylation of ketones and keto esters: Catalyst screening, chemoselectivity and dilution effects
The homogeneous titanium- and dye-catalyzed as well as the heterogeneous semiconductor particle-catalyzed photohydroxymethylation of ketones by methanol were investigated in order to evaluate the most active photocatalyst system. Dialkoxytitanium dichlorides are the most efficient species for chemoselective hydroxymethylation of acetophenone as well as other aromatic and aliphatic ketones. Pinacol coupling is the dominant process for semiconductor catalysis and ketone reduction dominates the Ti(OiPr)4/methanol or isopropanol systems. Application of dilution effects on the TiO2 catalysis leads to an increase in hydroxymethylation at the expense of the pinacol coupling.
Griesbeck, Axel G.,Reckenthaeler, Melissa
supporting information
p. 1143 - 1150
(2014/06/09)

Enantioselective trans-dihydroxylation of aryl olefins by cascade biocatalysis with recombinant escherichia coli coexpressing monooxygenase and epoxide hydrolase
Cascade biocatalysis via intracellular epoxidation and hydrolysis was developed as a green and efficient method for enantioselective dihydroxylation of aryl olefins to prepare chiral vicinal diols in high ee and high yield. Escherichia coli (SSP1) coexpressing styrene monooxygenase (SMO) and epoxide hydrolase SpEH was developed as a simple and efficient biocatalyst for S-enantioselective dihydroxylation of terminal aryl olefins 1a-15a to give (S)-vicinal diols 1c-15c in high ee (97.5-98.6% for 10 diols; 92.2-93.9% for 3 diols) and high yield (91-99% for 6 diols; 86-88% for 2 diols; 67% for 3 diols). Combining SMO and epoxide hydrolase StEH showing complementary regioselectivity to SpEH as a biocatalyst for the cascade biocatalysis gave rise to R-enantioselective dihydroxylation of aryl olefins, being the first example of this kind of reversing the overall enantioselectivity of cascade biocatalysis. E. coli (SST1) coexpressing SMO and StEH was also engineered as a green and efficient biocatalyst for R-dihydroxylation of terminal aryl olefins 1a-15a to give (R)-vicinal diols 1c-15c in high ee (94.2-98.2% for 7 diols; 84.2-89.9% for 6 diols) and high yield (90-99% for 6 diols; 85-89% for 5 diols; 65% for 1 diol). E. coli (SSP1) and E. coli (SST1) catalyzed the trans-dihydroxylation of trans-aryl olefin 16a and cis-aryl olefin 17a with excellent and complementary stereoselectivity, giving each of the four stereoisomers of 1-phenyl-1,2- propanediol 16c in high ee and de, respectively. Both strains catalyzed the trans-dihydroxylation of aryl cyclic olefins 18a and 19a to afford the same trans-cyclic diols (1R,2R)-18c and (1R,2R)-19c, respectively, in excellent ee and de. This type of cascade biocatalysis provides a tool that is complementary to Sharpless dihydroxylation, accepting cis-alkene and offering enantioselective trans-dihydroxylation.
Wu, Shuke,Chen, Yongzheng,Xu, Yi,Li, Aitao,Xu, Qisong,Glieder, Anton,Li, Zhi
p. 409 - 420
(2014/03/21)

A chiral benzyl group as a chiral auxiliary and protecting group for the synthesis of optically active 1,2-Diols and (+)-Frontalin
Chelation-controlled asymmetric nucleophilic addition of a Grignard reagent to chiral α-benzyloxy ketones gives the corresponding alcohols with high diastereoselectivities (up to 96% de) by 1,4-asymmetric induction. A chiral benzyl group is used as a chiral auxiliary as well as a protecting group for the synthesis of optically active 1,2-diols and (+)-frontalin. Georg Thieme Verlag Stuttgart, New York.
Kim, Tae Hyun,Kim, Young-Kyo,Yang, Zunhua,Jung, Jung Wha,Jeong, Lak Shin,Kim, Hee-Doo
supporting information
p. 251 - 254
(2014/02/14)

Metal-free reductive cleavage of benzylic esters and ethers: Fragmentations result from single and double electron transfers
The mechanisms for the reductive cleavage of benzylic esters and ethers by neutral organic electron donor 1 are different (see scheme). Products isolated from the cleavage of benzylic ethers result from the transfer of two electrons, without the intermediacy of benzyl radicals, which are believed to be intermediates in the reductive cleavage of benzylic esters. Copyright
Doni, Eswararao,O'Sullivan, Steven,Murphy, John A.
supporting information
p. 2239 - 2242
(2013/03/28)

Asymmetric diboration of terminal alkenes with a rhodium catalyst and subsequent oxidation: Enantioselective synthesis of optically active 1,2-diols
Pin it down: A highly enantioselective diboration of terminal alkenes with chiral 1 and bis(pinacolato)diboron (B2pin2) was realized. Subsequent oxidation of the diboron adducts with sodium peroxoborate readily gave the corresponding optically active 1,2-diols in high yields and high enantioselectivities. Copyright
Toribatake, Kenji,Nishiyama, Hisao
supporting information
p. 11011 - 11015
(2013/10/22)

Safe use of a toxic compound: Heterogeneous OsO4 catalysis in a nanobrush polymer microreactor
Putting osmium in its place: The immobilization of hazardous OsO 4 on polymer nanobrushes in a microreactor is a safe, effective, and green concept. The method allows reactions to be performed in a time- and chemical-saving manner, with little environmental impact, as compared to spill-over bulk processes. Copyright
Basavaraju,Sharma, Siddharth,Maurya, Ram Awatar,Kim, Dong-Pyo
p. 6735 - 6738
(2013/07/26)

Magnetically recoverable osmium catalysts with osmium-diolate esters for dihydroxylation of olefins
We prepared magnetically recoverable osmium catalysts with stable osmium-diolate esters and applied them to the dihydroxylation of olefins. By employing 2 mol% of the magnetic osmium catalyst, the dihydroxylation reaction proceeded smoothly to provide the corresponding vicinal diol with a low level of osmium leaching. After completion of the dihydroxylation, the osmium catalyst was readily recovered by use of an external magnet and was recycled up to five times. Georg Thieme Verlag Stuttgart . New York.
Fujita, Ken-Ichi,Umeki, Satoshi,Yasuda, Hiroyuki
p. 947 - 950
(2013/07/19)

OXAZOLIDINONE COMPOUNDS AND DERIVATIVES THEREOF
Compounds of Formula (I) and Formula (II) are useful inhibitors of tankyrase. Compounds of Formula (I) and Formula (II) have the following structure: where the definitions of the variables are provided herein.
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Paragraph 0363-0364

(2013/09/26)

Alkyl 2-(2-benzothiazolylsulfinyl)acetates as useful synthetic reagents for alkyl 4-hydroxyalk-2-enoates by sulfinyl-Knoevenagel reaction
Isopropyl, ethyl, and methyl 2-(2-benzothiazolylsulfinyl)acetates have been found to be useful synthetic reagents for sulfinyl-Knoevenagel reaction with various aldehydes to give directly the corresponding 4-hydroxyalk-2-enoates [R′CH(OH)CHCHCO2R], which are ubiquitous structures in biologically active natural products and useful building blocks for organic synthesis of chiral compounds. From the optically pure (R)-2-(2- benzothiazolylsulfinyl)acetates (>99% ee) prepared by the enzymatic kinetic resolution of (±)-2-(2-benzothiazolylsulfinyl)acetates, optically active 4-hydroxyalk-2-enoates (up to 91% ee) have been obtained in good yields.
Du, Zhenjun,Kawatani, Toshihiro,Kataoka, Kazuhide,Omatsu, Rikiya,Nokami, Junzo
experimental part
p. 2471 - 2480
(2012/04/10)

Stereoselective selenium catalyzed dihydroxylation and hydroxymethoxylation of alkenes
The selenium atom of the selenocysteine plays a crucial role in the reduction of peroxides. Herein we showed that, in the absence of a thiol cofactor, the same aminoacid efficiently catalyzed the dihydroxylation of carbon-carbon double bonds leading to the stereoselective formation of 1,2-diols at room temperature and in on water conditions. Alternatively, in the presence of methanol, the corresponding β-methoxyalcohol can be prepared. The stereoselectivity of the reaction will be discussed and NMR evidences of the actual catalyst are here reported.
Santi, Claudio,Di Lorenzo, Rosalia,Tidei, Caterina,Bagnoli, Luana,Wirth, Thomas
p. 10530 - 10535,6
(2012/12/12)

Organocatalytic asymmetric α-benzoyloxylation of α-branched aldehydes and enals: A useful approach to oxygenated quaternary stereocenters
Direct asymmetric α-benzoyloxylation of α-branched aldehydes and α-branched enals via enamine and dienamine catalysis was used to construct quaternary oxygenated stereocenters with good yields and moderate to good enantioselectivity. This method uses an inexpensive and readily available cinchona alkaloid-derived primary amine as the catalyst, benzoyl peroxide as the oxygen source, and stoichiometric amounts of the aldehyde substrates, providing simple metal-free access to valuable protected 2-hydroxyaldehyde derivatives.
Demoulin, Nicolas,Lifchits, Olga,List, Benjamin
supporting information; scheme or table
p. 7568 - 7574
(2012/09/21)

Metal-free dihydroxylation of alkenes using cyclobutane malonoyl peroxide
Cyclobutane malonoyl peroxide (7), prepared in a single step from the commercially available diacid 6, is an effective reagent for the dihydroxylation of alkenes. Reaction of a chloroform solution of 7 with an alkene in the presence of 1 equiv of water at 40 °C followed by alkaline hydrolysis leads to the corresponding diol (30-84%). With 1,2-disubstituted alkenes, the reaction proceeds with syn-selectivity (3:1 → 50:1). A mechanism consistent with experimental findings is proposed, which is supported by deuterium and oxygen labeling studies and explains the stereoselectivity observed. Alternative reaction pathways that are dependent on the structure of the starting alkene are also described leading to the synthesis of allylic alcohols and γ-lactones.
Jones, Kevin M.,Tomkinson, Nicholas C. O.
experimental part
p. 921 - 928
(2012/02/16)

An osmium(III)/osmium(V) redox couple generating OsV(O)(OH) center for cis -1,2-dihydroxylation of alkenes with H2O2: Os complex with a nitrogen-based tetradentate ligand
For the synthesis of the 1,2-diols, cis-1,2-dihydroxylation of alkenes catalyzed by osmium(VIII) tetroxide (OsO4) is a powerful method. However, OsO4 is quite toxic due to its highly volatile and sublimable nature. Thus, the development of alternative catalysts for cis-1,2-dihydroxylation of alkenes is highly challenging. Our approach involves the use of a nitrogen-based tetradentate ligand, tris(2-pyridylmethyl)amine (tpa), for an osmium center to develop a new osmium catalyst and hydrogen peroxide (H2O2) as a cheap and environmentally benign oxidant. The new Os-tpa complex acts as a very efficient turnover catalyst for syn-selective dihydroxylation of various alkenes (turnover number ～1000) in aqueous media, and H2O2 oxidant is formally incorporated into the products quantitatively (100% atom efficiency). The reaction intermediates involved in the catalytic cycle have been isolated and characterized crystallographically as [OsIII(OH)(H 2O)(tpa)]2+ and [OsV(O)(OH)(tpa)]2+ complexes. The observed syn-selectivity, structural characteristics of the intermediates, and kinetic studies have suggested a concerted [3 + 2]-cycloaddition mechanism between [OsV(O)(OH)(tpa)]2+ and alkenes, which is strongly supported by DFT calculations.
Sugimoto, Hideki,Kitayama, Kazuhiro,Mori, Seiji,Itoh, Shinobu
p. 19270 - 19280
(2013/01/15)

Homogeneous dihydroxylation of olefins catalyzed by OsO4 2- immobilized on a dendritic backbone with a tertiary nitrogen at its core position
OsO42- immobilized on a poly(benzyl ether) dendrimer with a tertiary nitrogen at its core position efficiently catalyzed the homogeneous dihydroxylation of olefins with a low level of osmium leaching. The dendritic osmium catalyst could be applied to the wide range of olefins. Furthermore, the dendritic osmium catalyst was recovered by reprecipitation and then reused up to five times.
Fujita, Ken-Ichi,Inoue, Kensuke,Tsuchimoto, Teruhisa,Yasuda, Hiroyuki
p. 1594 - 1598
(2013/02/23)

Erratum: Synthesis of enantioenriched tertiary boronic esters from secondary allylic carbamates. Application to the synthesis of C30 botryococcene (Journal of the American Chemical Society (2012) 134 (7570-7575) DOI: 10.1021/ja303022d)
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Pulis, Alexander P.,Aggarwal, Varinder K.
p. 11298 - 11298
(2012/08/28)