- Oxidovanadium(IV) complexes of 3-hydroxy-4-pyrone and 3-hydroxy-4- pyridinone ligands: A new generation of homogeneous catalysts for the epoxidation of geraniol
-
A novel generation of homogeneous catalysts for the epoxidation of geraniol, in the presence of tert-butyl hydroperoxide oxidant is reported. Oxidovanadium(IV) complexes of 3-hydroxy-4-pyrone and 3-hydroxy-4-pyridinone ligands exhibit excellent activity and selectivity towards the 2,3-epoxygeraniol product, only differing in the reaction times and turnover frequencies. The pyrone based complexes are the most efficient catalysts showing performances similar to that of the well known oxidovanadium(IV) acetylacetonate catalyst. Graphical abstract: [Figure not available: see fulltext.]
- Pereira, Clara,Leite, Andreia,Nunes, Ana,Rebelo, Susana L. H.,Rangel, Maria,Freire, Cristina
-
-
Read Online
- SELECTIVE EPOXIDATION OF ALLYLIC ALCOHOLS WITH DIBUTYLTIN OXYPEROXYDE
-
Dibutyltin oxyperoxide derived from BuSnO and tBuOOH epoxidize allylic alcohols with high stereo- and regioselectivities.
- Kanemoto, Shigekazu,Nonaka, Tsuyoshi,Oshima, Koichiro,Utimoto, Kiitiro,Nozaki, Hitosi
-
-
Read Online
- Photo-Oxidation of 2-(2-Furyl)-1,3-Dicarbonyl Compounds
-
A very efficient photo-sensitized oxidation of 2-(2-furyl)-1,3-dicarbonyl compounds 1 afford directly hydroperoxides 2 in stereoselective way.Compounds 2, easily isolated, can be conveniently employed in a selective epoxidation of trisubstituted allylic alcohols by a Sharpless-type procedure.
- Antonioletti, R.,Bonadies, F.,Pesci, S.,Scettri, A.
-
-
Read Online
- STEREOSELECTIVE EPOXIDATION OF ALLYLIC ALCOHOLS AND DEHYDROGENATIVE OXIDATION OF SECONDARY ALCOHOLS BY MEANS OF t-BUTYL HYDROPEROXIDE AND ALUMINIUM REAGENTS.
-
Treatment of a solution of geraniol and (t-BuO)//3Al in benzene with t-BuOOH at 5 degree C gives (2R*, 3R*)-2,3-epoxy-3,7-dimethyl-6-octenyl acetate in 83% yield after acetylative workup. Eight allylic alcohols are converted to alpha , beta -epoxy alcohols in preparative yields. The epoxidation of secondary (E)-allylic alcohols shows opposite stereo-selectivities to t-BuOOH-VO(acac)//2 system. Asymmetric epoxidation with a chiral hydroxamic acid as a ligand gives unsatisfactory degrees of enantiomeric excess. The same system can also convert secondary alcohols into ketones in excellent yields, while primary ones react very slowly.
- Takai,Oshima,Nozaki
-
-
Read Online
- Palladium-catalyzed stereospecific epoxide-opening reaction of γ,δ-epoxy-α,β-unsaturated esters with boric acid leading to γ,δ-diol derivatives with double inversion of configuration
-
A new palladium-catalyzed epoxide-opening reaction of γ,δ- epoxy-α,β-unsaturated esters with boric acid has been developed, which proceeds stereospecifically giving rise to the corresponding γ,β-diol derivatives with double inversion of the configuration, i.e., with retention of configuration, in excellent yields. The new method provides a useful tool in organic synthesis including natural product synthesis. (Graph Presented).
- Yu, Xiao-Qiang,Hirai, Atsushi,Miyashita, Masaaki
-
-
Read Online
- Total Synthesis of Kadcoccinic Acid A Trimethyl Ester
-
The first total synthesis of the trimethyl ester of kadcoccinic acid A is described. The central structural element of our synthesis is a cyclopentenone motif that allows the assembly of the natural product skeleton. A gold(I)-catalyzed cyclization of an enynyl acetate led to efficient construction of the cyclopentenone scaffold. In this step, optimization studies revealed that the stereochemistry of the enynyl acetate dictates regioisomeric cyclopentenone formation. The synthesis further highlights an efficient copper-mediated conjugate addition, merged with a gold(I)-catalyzed Conia-ene reaction to connect the two fragments, thereby forging the D-ring of the natural product. The synthetic strategy reported herein can provide a general platform to access the skeleton of other members of this family of natural products.
- Gholami, Hadi,Trost, Barry M.,Zell, Daniel,Zhang, Guoting
-
supporting information
p. 12286 - 12293
(2021/08/20)
-
- New heptacoordinate tungsten(II) complexes with α-diimine ligands in the catalytic oxidation of multifunctional olefins
-
New tungsten(II) and molybdenum(II) heptacoordinate complexes [MX2(CO)3(LY)] (MXLy: M = W, Mo; X = Br, I; LY = C5H4NCY = N(CH2)2CH3 with Y = H (L1), Me (L2), Ph (L3)) were synthesized and characterized by spectroscopic techniques and elemental analysis. The two tungsten complexes WXL1 (X = Br, I) were also structurally characterized by single crystal X-ray diffraction. The metal coordination environment is in both a distorted capped octahedron. The complexes with L1 and L2 ligands were grafted in MCM-41, after functionalization of the ligands with a Si(OEt)3 group. The new materials were characterized by elemental analysis, N2 adsorption isotherms, 29Si MAS and 13C MAS NMR. The tungsten(II) complexes and materials were the first examples of this type reported. All complexes and materials were tested as homogeneous and heterogeneous catalysts in the oxidation of multifunctional olefins (cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, geraniol, S-limonene, and 1-octene), with tert-butyl hydroperoxide (TBHP) as oxidant. The molybdenum(II) catalyst precursors are in general very active, reaching 99% conversion and 100% selectivity in the epoxidation of trans-hex-3-en-1-ol. Their performance is comparable with that of the [Mo(η3-C3H5)X(CO)2(LY)] complexes, but it increases with immobilization. On the other hand, most of the W(II) complexes display an activity similar or inferior to that of the Mo(II) analogues and it decreases after they are supported in MCM-41. DFT calculations show that tungsten complexes and iodide ligands are more easily oxidized from M(II) to M(VI) than molybdenum ones, while the energies of relevant species in the catalytic cycle are very similar for all complexes, making the theoretical rationalization of experimental catalytic data difficult.
- Vasconcellos-Dias, Maria,Nunes, Carla D.,Félix, Vítor,Brand?o, Paula,Calhorda, Maria José
-
-
- Transition Metal-Substituted Potassium Silicotungstate Salts as Catalysts for Oxidation of Terpene Alcohols with Hydrogen Peroxide
-
Abstract: In this work, the catalytic activity of the transition metal-substituted potassium silicotungstate salts (i.e. K8-nSiMn+W11O39 (Mn+ = Cu2+, Co2+, Ni2+, Zn2+ and Fe3+) was investigated on the oxidation reactions of the terpene alcohols with H2O2 aqueous solution. The metal-substituted silicotungstate salts were easily synthesized in one-pot reactions of the precursor metal solutions (i.e. Na2WO4, Na2SiO3 and MCln) with KCl added in stoichiometric amount; after this precipitation step, the solid heteropoly salts were filtered and dried in an oven. This procedure of synthesis avoids multi-step processes that starts from the pristine heteropolyacid. The substituted metal heteropoly salts were characterized by infrared spectroscopy, measurements of the specific surface area (BET) and porosimetry by isotherms of adsorption/desorption of N2, X-rays diffraction, thermal analyses, dispersive X-rays spectroscopy, scanning electronic microscopy. The acidity strength was estimated by potentiometric titration with n-butylamine. All the salts were evaluated as catalysts in terpenic alcohols oxidation reactions with H2O2. The K5SiFeW11O39 was the most active and selective catalyst toward oxidation products. The impacts of the main reaction variables such as catalyst concentration, temperature, oxidant load, and nature of the terpene substrate were assessed. The highest activity of the K5SiFeW11O39 catalyst was assigned to the highest Lewis acidity. Graphic Abstract: [Figure not available: see fulltext.].
- da Silva, Marcio Jose,da Silva Andrade, Pedro Henrique,Sampaio, Vinicius Fernando Coelho
-
p. 2094 - 2106
(2020/11/13)
-
- Olefin epoxidation with ionic liquid catalysts formed by supramolecular interactions
-
This work demonstrated that the specific ionic liquids (ILs) have been designed via the supramolecular complexation between 18-crown-6 (CE) and ammonium peroxoniobate (NH4-Nb). The resultant ILs have been characterized by elemental analysis, FT-IR, Raman, NMR, DSC, conductivity measurement and MALDI-TOF, etc. The IL (CE-1) consisting of CE and ammonium peroxoniobate can be further coordinated with GLY to generate a new IL (CE-2), which showed both high catalytic activity in epoxidation with H2O2 and good recyclability. The characterization of 93Nb NMR spectra revealed that the peroxoniobate anions has demonstrated a structural evolution in the presence of hydrogen peroxide, in which Nb[dbnd]O species can be easily oxidized into the catalytically active niobium?peroxo species. Especially, the supramolecular complexation can provide suitable hydrophobicity, which ensured that the hydrophobic olefins and allylic alcohols were easily accessible to the catalytically active anions, and thus facilitated the epoxidation reaction. Notably, the supramolecular IL catalysts in this work exhibited a huge advantage of the easy availability, as compared with the previously reported peroxoniobate-based ILs. As far as we know, this is the first example of the highly selective epoxidation of olefins and allylic alcohols by using supramolecular ILs as catalysts.
- Ding, Bingjie,Hou, Zhenshan,Li, Difan,Ma, Wenbao,Yao, Yefeng,Zhang, Ran,Zheng, Anna,Zhou, Qingqing
-
-
- Vanadium-doped sodium phosphomolybdate salts as catalysts in the terpene alcohols oxidation with hydrogen peroxide
-
In this work, we have explored the catalytic activity of Keggin-type heteropolyanions PMo12?nVnO40(3+n)?(n= 0, 1, 2, or 3) in the form of sodium salts in green oxidation routes of terpene alcohols with hydrogen peroxide. Nerol was the model molecule selected to assess the impacts of the main reaction parameters, such as temperature, catalyst load, and stoichiometry of reactants. The impacts of the presence of vanadium at different proportions (i.e., V1, V2, and V3loads/per anion) in the structure of phosphomolybdate catalysts were assessed. All the catalysts were characterized by various techniques such as powder X-ray diffraction, attenuated diffuse reflectance infrared spectroscopy, ultraviolet-visible spectroscopy, thermogravimetric analysis, isotherms of adsorption-desorption of N2measurements of surface area, scanning electronic microscopy, energy-dispersive X-ray spectroscopy, andn-butylamine potentiometric titration. Among the catalysts assessed, Na4PMo11VO40was the most active and selective toward epoxides. The efficiency of this catalyst in the epoxidation of different terpene alcohols was investigated. Special attention was dedicated to correlating the composition and properties of the vanadium-doped phosphomolybdic catalysts with their catalytic activity.
- Ferreira, Sukarno Olavo,Rodrigues, Alana Alves,Vilanculo, Castelo Bandane,da Silva, Márcio José,da Silva, Rene Chagas
-
p. 24072 - 24085
(2021/07/29)
-
- Proton-accelerated Lewis acid catalysis for stereo- And regioselective isomerization of epoxides to allylic alcohols
-
The isomerization of epoxides to allylic alcohols was developedviaproton-accelerated Lewis acid catalysis. The addition oftBuOH as a proton source is the key to the efficient catalytic cycle. Trisubstituted epoxides, including enantioenriched derivatives, were selectively converted to secondary-allylic alcohols without loss of enantiopurity.
- Baba, Misako,Hayashi, Satoshi,Hirabe, Rina,Noji, Masahiro,Takanami, Toshikatsu
-
supporting information
p. 7104 - 7107
(2021/07/28)
-
- Can Br?nsted acids catalyze the epoxidation of allylic alcohols with H2O2? With a little help from the proton, the H3PMo12O40 acid did it and well
-
In this work, we have explored the catalytic activity of typical Br?nsted acid in epoxidation reactions of terpene alcohols with hydrogen peroxide. Keggin heteropolyacids (HPAs) (i.e., H3PW12O40, H3PMo12O40, and H4SiW12O40) were compared to the common Br?nsted acids (i.e., sulfuric, and p-toluenesulfonic acids) in epoxidation reactions of nerol, the model molecule selected. The effects of the main reaction variable, such as temperature, time, load and sort of acid catalyst were evaluated. Among the catalysts investigated, H3PMo12O40 was the most active and selective catalyst toward epoxide nerol, the goal product. The highest conversion obtained was 99%, with a selectivity of 97% towards nerol epoxide. A discussion of the reaction mechanism was performed as the basis of experimental results and acidity properties of the catalysts. A comparison with a non-protic catalyst (i.e., Na3PMo12O40) allowed demonstrate that both Molybdenum and protons present in the H3PMo12O40 are the main active sites in this epoxidation reaction.
- Vilanculo, Castelo Bandane,da Silva, Márcio José
-
-
- Dysprosium-doped zinc tungstate nanospheres as highly efficient heterogeneous catalysts in green oxidation of terpenic alcohols with hydrogen peroxide
-
A green route to oxidize terpenic alcohols (nerol and geraniol) with H2O2over a solid catalyst was developed. The Dy-doped ZnWO4catalyst was synthesized by coprecipitation and microwave-assisted hydrothermal heating, containing different dysprosium loads. All the catalysts were characterized through infrared spectroscopy, powder X-ray diffraction, surface area and porosimetry, transmission electronic microscopy image, andn-butylamine potentiometric titration analyses. The influence of main reaction parameters such as temperature, the stoichiometry of reactants, loads, and catalyst nature was assessed. ZnWO42.0 mol% Dy was the most active catalyst achieving the highest conversion (98%) and epoxide selectivity (78%) in nerol oxidation. The reaction scope was extended to other terpenic alcohols (i.e., geraniol, borneol, and α-terpineol). The highest activity of ZnWO42.0 mol% Dy was assigned to the lower crystallite size, higher surface area and pore volume, higher acidity strength and the greatest dysprosium load.
- Batalha, Daniel Carreira,Mesquita Borges, Kellen Cristina,de Fátima Gon?alves, Rosana,de Matos Rodrigues, Murillo Henrique,Godinho, Mário Júnior,Fajardo, Humberto Vieira,de Oliveira Bruziquesi, Carlos Giovani,da Silva, Márcio José
-
p. 6661 - 6670
(2021/04/22)
-
- Bridgehead Modifications of Englerin A Reduce TRPC4 Activity and Intravenous Toxicity but not Cell Growth Inhibition
-
Modifications at the bridgehead position of englerin A were made to explore the effects of variation at this site on the molecule for biological activity, as judged by the NCI 60 screen, in which englerin A is highly potent and selective for renal cancer cells. Replacement of the isopropyl group by other, larger substituents yielded compounds which displayed excellent selectivity and potency comparable to the natural product. Selected compounds were also evaluated for their effect on the ion channel TRPC4 as well as for intravenous toxicity in mice, and these had lower potency in both assays compared to englerin A.
- Wu, Zhenhua,Suppo, Jean-Simon,Tumova, Sarka,Strope, Jonathan,Bravo, Fernando,Moy, Melody,Weinstein, Ethan S.,Peer, Cody J.,Figg, William D.,Chain, William J.,Echavarren, Antonio M.,Beech, David J.,Beutler, John A.
-
supporting information
p. 1711 - 1716
(2020/10/19)
-
- Three- and two-site heteropolyoxotungstate anions as catalysts for the epoxidation of allylic alcohols by H2O2 under biphasic conditions: Reactivity and kinetic studies of the [Ni3(OH2)3(B-PW9O34){WO5(H2O)}]7?, [Co3(OH2)6(A-PW9O34)2]12?, and [M4(OH2)2(B-PW9O34)2]10? anions, where M?=?Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)
-
The trimetallic phosphopolyoxotungstate anions [Ni3(OH2)3(B-PW9O34){WO5(H2O)}]7? and [Co3(OH2)6(A-PW9O34)2]12? have been studied as epoxidation catalysts for oxygen transfer from 30% H2O2 to a range of allylic alcohols under biphasic conditions (1,2-dichloroethane/H2O) at 15 °C. The reaction mechanism involves coordination of an allylic alcohol at an M(II) site in each case, prior to transfer of a peroxy oxygen from an adjacent W(O2) site. The latter is formed from a terminal W = O unit by reaction with H2O2. Evidence of W(O2) formation was obtained through IR studies. The W(O2) group forms the epoxide by transfer of an oxygen atom to the C[dbnd]C bond of the coordinated allylic alcohol. Kinetic studies using 3-methyl-2-buten-1-ol as the allylic alcohol substrate have been modelled with all three metal sites catalytically active. The reaction involves an autocatalysis mechanism involving an induction period, which can be rationalised by proposing not only coordination of the allylic alcohol to M(II), but also the product hydroxy epoxide, both through their –OH groups. The autocatalysis is generated by formation of the W(O2) group adjacent to a coordinated hydroxy epoxide, which competes with coordination of allylic alcohol. The mechanism requires some twenty-one steps involving just the generic steps listed above, with all three metal sites catalytically active. Temperature-dependent kinetic studies and subsequent Eyring analyses have shown that the Co(II)-containing catalyst is the most active of the two. Analogous studies of the epoxidation of 3-methyl-2-buten-1-ol by the two-site [M4(OH2)2(B-PW9O34)2]10? ions as catalysts, where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), at 15 °C gave an order of reactivity of Cu(II) > Ni(II) > Zn(II), Co(II), Mn(II), which mostly mimics the natural order of stability constants (the Irving-Williams series), suggesting that the formation of the allylic alcohol complexes play a dominant role in this series of related complex anions, with greater replacement of water by allylic alcohol leading to greater reactivity.
- Abram, Paulus Hengky,Burns, Robert C.,Li, Lichun
-
-
- One-pot synthesis at room temperature of epoxides and linalool derivative pyrans in monolacunary Na7PW11O39-catalyzed oxidation reactions by hydrogen peroxide
-
In this work, we describe a new one-pot synthesis route of valuable linalool oxidation derivatives (i.e., 2-(5-methyl-5-vinyltetrahydrofuran-2-yl propan-2-ol) (1a)), 2,2,6-trimethyl-6-vinyltetrahydro-2H-pyran-3-ol (1b) and diepoxide (1c), using a green oxidant (i.e., hydrogen peroxide) under mild conditions (i.e., room temperature). Lacunar Keggin heteropolyacid salts were the catalysts investigated in this reaction. Among them, Na7PW11O39 was the most active and selective toward oxidation products. All the catalysts were characterized by FT-IR, TG/DSC, BET, XRD analyses and potentiometric titration. The main reaction parameters were assessed. Special attention was dedicated to correlating the composition and properties of the catalysts and their activity.
- Da Silva, Márcio J.,Teixeira, Milena Galdino,Vilanculo, Castelo B.,Villarreal, Jesus Avendano
-
p. 7691 - 7697
(2020/03/10)
-
- Enantiocomplementary Epoxidation Reactions Catalyzed by an Engineered Cofactor-Independent Non-natural Peroxygenase
-
Peroxygenases are heme-dependent enzymes that use peroxide-borne oxygen to catalyze a wide range of oxyfunctionalization reactions. Herein, we report the engineering of an unusual cofactor-independent peroxygenase based on a promiscuous tautomerase that accepts different hydroperoxides (t-BuOOH and H2O2) to accomplish enantiocomplementary epoxidations of various α,β-unsaturated aldehydes (citral and substituted cinnamaldehydes), providing access to both enantiomers of the corresponding α,β-epoxy-aldehydes. High conversions (up to 98 %), high enantioselectivity (up to 98 % ee), and good product yields (50–80 %) were achieved. The reactions likely proceed via a reactive enzyme-bound iminium ion intermediate, allowing tweaking of the enzyme's activity and selectivity by protein engineering. Our results underscore the potential of catalytic promiscuity for the engineering of new cofactor-independent oxidative enzymes.
- Crotti, Michele,Kataja, Kim M.,Poelarends, Gerrit J.,Saravanan, Thangavelu,Xu, Guangcai
-
supporting information
p. 10374 - 10378
(2020/04/23)
-
- Enantioselective Total Synthesis of Cotylenin A
-
A convergent enantioselective total synthesis of cotylenin A is described. The A-ring fragment, prepared via the catalytic asymmetric intramolecular cyclopropanation developed in our laboratory, and the C-ring fragment, prepared from a known chiral compound via a modified acyl radical cyclization, were successfully assembled by the Utimoto coupling reaction. The formidable carbocyclic eight-membered ring of cotylenin A was efficiently constructed by a palladium-mediated cyclization. All the hydroxy groups in the scaffold were stereoselectively introduced, and a modified reducing reagent, Me4NBH(O2CiPr)3, has been developed. The sugar moiety fragment was prepared via three consecutive carbon-oxygen bond-forming reactions, and the glycosylation was accomplished using Wan's protocol.
- Nagatani, Kotaro,Nakada, Masahisa,Osada, Ryunosuke,Sugiyama, Ryoji,Uwamori, Masahiro
-
supporting information
p. 5556 - 5561
(2020/04/10)
-
- Oxidation of terpenic alcohols with hydrogen peroxide promoted by Nb2O5 obtained by microwave-assisted hydrothermal method
-
The present work describes the synthesis of niobium oxides by microwave-assisted hydrothermal method and their evaluation as a solid catalyst in oxidation reactions of terpenic alcohols with hydrogen peroxide. Effects of main parameters of synthesis were assessed and all the prepared catalysts were characterized by physical adsorption/ desorption analyses of nitrogen, infrared and Raman spectroscopies, scanning electron microscopy and powder X-rays diffraction analyses. The strength and number of acidic sites of the catalysts were determined by potentiometric titration. Morphological and structural characterization corroborate with the activity and selectivity achieved by the niobium oxides. The reusability of the catalyst was evaluated. The impacts of main reaction variables such as temperature, catalyst, and oxidant load were assessed. Niobium oxide demonstrated to be an effective catalyst, selectively converting the nerol (model molecule) to epoxide and aldehyde. Oxidation of various terpenic alcohols was investigated. Only geraniol and nerol were selectively epoxidized, suggesting a hydroxyl group assisted reaction. Although being also allylic alcohol, linalool was unreactive toward epoxidation due to the presence of a methyl group at the same carbon atom than the hydroxy group. The use of an environmentally cheap friendly oxidant (H2O2) and efficient solid catalyst (Nb2O5) are positive aspects of this process.
- Carreira Batalha, Daniel,Hadler Marins, Natália,Lenin Villarreal Carre?o, Neftalí,Marques e Silva, Ricardo,Vieira Fajardo, Humberto,da Silva, Márcio José
-
-
- Unraveling the role of the lacunar Na7PW11O39 catalyst in the oxidation of terpene alcohols with hydrogen peroxide at room temperature
-
In this work, we have assessed the activity of various Keggin heteropolyacid (HPA) salts in a new one-pot synthesis route of valuable products, which were obtained from the oxidation of terpenic alcohols (i.e., aldehyde, epoxide, and diepoxide), using a green oxidant (i.e., hydrogen peroxide) at mild conditions (i.e., room temperature). Lacunar Keggin HPA sodium salts were the goal catalysts investigated in this reaction. Starting from the HPAs (H3PW12O40, H3PMo12O40, and H4SiW12O40), we synthesized lacunar sodium salts (Na7PW11O39, Na7PW11O39 and Na8SiW11O39) and a saturated salt (Na3PW12O40). All of them were investigated in oxidation reactions in a homogeneous phase with nerol as a model molecule. Na7PW11O39 was the most active and selective towards the oxidation products. All the catalysts were characterized by FT-IR, TG/DSC, BET, XRD, and SEM-EDS analyses and potentiometric titration. The main reaction parameters were assessed. Geraniol, α-terpineol, β-citronellol and borneol were also successfully oxidized. Special attention was dedicated to correlating the composition and properties of the catalysts with their activity.
- Vilanculo, Castelo B.,Da Silva, Márcio J.
-
p. 2813 - 2820
(2020/03/03)
-
- Total Syntheses and Determination of Absolute Configurations of Cep-212 and Cep-210, Predicted Biosynthetic Intermediates of Tetrodotoxin Isolated from Toxic Newt
-
Total syntheses of Cep-212 and Cep-210, predicted biosynthetic intermediates of tetrodotoxin isolated from the Japanese toxic newt, have been accomplished from geraniol by an intramolecular hetero Diels-Alder reaction as a key step in a highly stereoselective manner. The success of these syntheses enabled us to determine their absolute configurations by using a chiral normal-phase HPLC/MS analysis of the bis-dinitrobenzene derivative of natural Cep-212 and reference derivatives prepared from chemically synthesized enantiomers.
- Adachi, Masaatsu,Miyasaka, Tadachika,Kudo, Yuta,Sugimoto, Keita,Yotsu-Yamashita, Mari,Nishikawa, Toshio
-
supporting information
p. 780 - 784
(2019/01/21)
-
- ENGLERIN DERIVATIVES FOR TREATMENT OF CANCER
-
Disclosed is a compound of formula (I) in which a, R1- R5 and X1 are as described herein. Also disclosed are a pharmaceutical composition containing the compound and a method of using the compound for treating cancer, such as renal cancer.
- -
-
Paragraph 0095-0097
(2019/01/21)
-
- Stereochemical Determination of Tuscolid/Tuscorons and Total Synthesis of Tuscoron D and E: Insights into the Tuscolid/Tuscoron Rearrangement
-
The stereochemistry of the structurally unique myxobacterial polyketides tuscolid/tuscorons was determined by a combination of high-field NMR studies, molecular modeling, and chemical derivatization and confirmed by a modular total synthesis of tuscorons D and E. Together with the discovery of three novel tuscorons, this study provides detailed insight into the chemically unprecedented tuscolid/tuscoron rearrangement cascade.
- G?ricke, Bj?rn,Bieber, Michelle Fernandez,Mohr, Kathrin E.,Menche, Dirk
-
supporting information
p. 13019 - 13023
(2019/08/30)
-
- Ionic Liquid Stabilized Niobium Oxoclusters Catalyzing Oxidation of Sulfides with Exceptional Activity
-
We present here a new class of niobium oxoclusters that are stabilized effectively by carboxylate ionic liquids. These functionalized ILs are designated as [TBA][LA], [TBA][PA], and [TBA][HPA] in this work, in which TBA represents tetrabutylammonium and LA, PA, and HPA refer to lactate, propionate, 3-hydroxypropionate anions, respectively. The as-synthesized Nb oxoclusters have been characterized by use of elemental analysis, NMR, IR, XRD, TGA, HRTEM. It was found that [TBA][LA]-stabilized Nb oxoclusters (Nb?OC@[TBA][LA]) are uniformly dispersed with an average particle size of 2–3 nm and afforded exceptionally high catalytic activity for the selective oxidation of various thioethers. The turnover number with Nb?OC@[TBA][LA] catalyst was over 56 000 at catalyst loading as low as 0.0033 mol % (1 ppm). Meantime, the catalyst also showed the high activity for the epoxidation of olefins and allylic alcohols by using only 0.065 mol % of catalyst (50 ppm). The characterization of 93Nb NMR spectra revealed that the Nb oxoclusters underwent structural transformation in the presence of H2O2 but regenerated to their initial state at the end of the reaction. In particular, the highly dispersed Nb oxoclusters can absorb a large amount of polar organic solvents and thus were swollen greatly, which exhibited “pseudo” liquid phase behavior, and enabled the substrate molecules to be highly accessible to the catalytic center of Nb oxocluster units.
- Zhou, Qingqing,Ye, Man,Ma, Wenbao,Li, Difan,Ding, Bingjie,Chen, Manyu,Yao, Yefeng,Gong, Xueqing,Hou, Zhenshan
-
p. 4206 - 4217
(2019/03/26)
-
- A mononuclear tantalum catalyst with a peroxocarbonate ligand for olefin epoxidation in compressed CO2
-
A new class of tantalum-based peroxocarbonate ionic liquid ([P4,4,4,4]3[Ta(η2-O2)3(CO4)]) has been generated through the reaction of pressurized CO2 with [P4,4,4,4]3[Ta(O)3(η2-O2)] in the presence of H2O2 during the reaction process. The newly formed species has been verified by NMR, FT-IR, HRMS and density functional theory (DFT) calculations. The CO2-induced monomeric peroxocarbonate anion-based ionic liquid is more advantageous than the monomeric peroxotantalate analogue for the epoxidation of olefins under very mild conditions. Interestingly, the transformation between peroxotantalate and peroxocarbonate species is completely reversible, and CO2 can actually act as a trigger agent for epoxidation reaction. The further mechanism studies by DFT calculation reveal that peroxo η2-O2 (site a) affords higher reactivity towards the CC bond than that of peroxocarbonate-CO4 (site b). These quantitative illustrations of the relationship between structural properties and kinetic consequences enable rational design for an efficient and environmental IL catalyst for the epoxidation of olefins.
- Ma, Wenbao,Qiao, Yunxiang,Theyssen, Nils,Zhou, Qingqing,Li, Difan,Ding, Bingjie,Wang, Dongqi,Hou, Zhenshan
-
p. 1621 - 1630
(2019/04/10)
-
- Synthesis of a new schiff base oxovanadium complex with melamine and 2-hydroxynaphtaldehyde on modified magnetic nanoparticles as catalyst for allyl alcohols and olefins epoxidation
-
A new magnetically recoverable nanocatalyst designated as Fe3O4@SiO2@PTMS@Mel-Naph-VOcomplex was synthesize by covalent binding of a Schiff base ligand derived from melamine and 2-hydroxy1naphtaldehyde on the surface of silica coated iron oxide magnetic nanoparticles followed by complexation with VO (acac)2. Characterization of the prepared nanocatalyst was accomplished with FT-IR, XRD, SEM, HRTEM, VSM and atomic absorption techniques. It was found that the epoxidation of geraniol, trans-2-hexen-1-ol, 1-octen-3-ol, norbornene, and cyclooctene is highly selective, affording quantitative yields of the corresponding epoxides with tert-butyl hydroperoxide (TBHP) using Fe3O4@SiO2@Mel-Naph-VOcomplex as catalyst. High reaction yields, short reaction times, simple experimental and work up procedure, catalyst stability and excellent reusability even after five-cycles of usage in the case of geraniol are some advantages of this research.
- Farzaneh, Faezeh,Asgharpour, Zeinab
-
-
- Metalation and DFT studies of metal organic frameworks UiO-66(Zr) with vanadium chloride as allyl alcohol epoxidation catalyst
-
UiO-66(Zr)-V as metal organic framework was prepared by metalation of the UiO-66(Zr) nodes with VCl3. The characterization of the prepared catalyst was carried out using XRD, EDX, FT IR, BET, ICP, Raman, DRS, SEM and XPS techniques. The density functional theory (DFT) was used in order to find the most stable position of the vanadium of metallated UiO-66(Zr). It was found that UiO-66(Zr)-V has been generated via metalation of V(V) ions with two OH groups of Zr-based nodes. The XPS results confirmed DFT studies. The catalytic activity of UiO-66(Zr)-V for epoxidation of some allyl alcohols such as trans-2-hexene-1-ol, geraniol, 1-octene-3-ol and 3-methyl-2-buten-1-ol with 46–97% conversions and 100% selectivity is considerable.
- Geravand, Elham,Farzaneh, Faezeh,Ghiasi, Mina
-
-
- A useful propionate cofactor enhancing activity for organic solvent-tolerant recombinant metal-free bromoperoxidase (perhydrolase) from Streptomyces aureofaciens
-
The oxidative brominating activity of an organic solvent-tolerant recombinant metal-free bromoperoxidase BPO-A1 with C-terminal His-tag (rBPO-A1), from Streptomyces aureofaciens found to depend on various additives. These included carboxylic acids, used as cofactors and alcohols, used as water-miscible organic solvents. Enzyme activity was significantly enhanced by using propanoic acid (PA) as a cofactor, which had a high Log D at pH 5.0 and ethylene glycol with a low Log P. The positional specificity of oxidative hydroxybromination for olefins, using rBPO-A1 and PA in the presence of methanol, was higher compared to a non-enzymatic reaction using peracetic acid. The oxidative bromination step, occurring after enzymatic peroxidation step, is suggested to be pseudoenzymatic.
- China, Hideyasu,Ogino, Hiroyasu
-
p. 327 - 332
(2019/07/12)
-
- New molybdenum(II) complexes with α-diimine ligands: Synthesis, structure, and catalytic activity in olefin epoxidation
-
Three new complexes [Mo(η3-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR,13C- and29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.
- Vasconcellos-Dias, Maria,Marreiros, Jo?o,Sales, Rita,Félix, Vitor,Brand?o, Paula,Nunes, Carla D.,José Calhorda, Maria
-
-
- Borinic Acid/Halide Co-catalyzed Semipinacol Rearrangements of 2,3-Epoxy Alcohols
-
A new mode of catalysis of the semipinacol rearrangement of 2,3-epoxy alcohols is described. In combination with a halide salt additive, diarylborinic acids promote a Type II rearrangement that occurs with net retention of configuration. This unusual stereochemical outcome is consistent with a mechanism involving regioselective ring opening of the epoxy alcohol by halide, followed by rearrangement of the resulting halohydrin-derived borinic ester. The protocol is applicable to a range of substrates, enabling ring contractions and expansions as well as stereospecific syntheses of acyclic β-hydroxycarbonyl compounds.
- Tanveer, Kashif,Kim, Seung-Joon,Taylor, Mark S.
-
supporting information
p. 5327 - 5331
(2018/09/13)
-
- Synthesis, characterization and immobilization of a novel mononuclear vanadium (V) complex on modified magnetic nanoparticles as catalyst for epoxidation of allyl alcohols
-
The 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) undergoes hydrolysis in the presence of VO(SO4) in an alkaline solution, affording mainly the bis(2-pyridyl carbonyl)amid) VO2 complex, designated as [VO2(bpca)]. Single-crystal X-ray crystallography revealed that the coordination of V in complex is a distorted square-pyramid coordinated with three nitrogen of bis(2-pyridyl carbonyl)amid) ligand and two binding oxygen atoms. The prepared complex which successfully supported on modified Fe3O4 nanoparticles using tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane(APTMS)was designated as Fe3O4@SiO2@APTMS@[VO2(bpca)] complex (nanocatalyst). The complex and nanocatalyst were characterized by means of FT-IR, XRD, VSM, SEM and TEM. The catalytic activity of [VO2(bpca)] complex and Fe3O4@SiO2@APTMS@complex as catalysts 1 and 2 were evaluated by the epoxidation of geraniol, 3-methyl-2-buten-1-ol, trans-2-hexen-1-ol and 1-octen-3-ol with 70–98% conversions and 95–100% selectivities. Based on the obtained results, the heterogeneity and reusability of the catalyst seems promising. In addition, the in vitro antibacterial activity of [VO2 (bpca)] complex have also been evaluated and compared to the activities of other vanadium complexes, tptz ligand and two standard antibacterial drugs, Nalidixic acid and Vancomycin.
- Azarkamanzad, Zahra,Farzaneh, Faezeh,Maghami, Mahboobeh,Simpson, Jim,Azarkish, Mohammad
-
-
- Unveiling the Active Surface Sites in Heterogeneous Titanium-Based Silicalite Epoxidation Catalysts: Input of Silanol-Functionalized Polyoxotungstates as Soluble Analogues
-
We report on a site-isolated model for Ti(IV) by reacting [Ti(iPrO)4] with the silanol-functionalized polyoxotungstates [XW9O34-x(tBuSiOH)3]3- (X = P, x = 0, 1; X = Sb, x = 1, 2) in tetrahydrofuran. The resulting titanium(IV) complexes [XW9O34-x(tBuSiO)3Ti(OiPr)]3- (X = P, 3; X = Sb, 4) were obtained in monomeric forms both in solution and in the solid state, as proved by diffusion NMR experiments and by X-ray crystallographic analysis. Anions 3 and 4 represent relevant soluble models for heterogeneous titanium silicalite epoxidation catalysts. The POM scaffolds feature slight conformational differences that influence the chemical behavior of 3 and 4 as demonstrated by their reaction with H2O. In the case of 3, the hydrolysis reaction of the isopropoxide ligand is only little shifted toward the formation of a monomeric [PW9O34(tBuSiO)3Ti(OH)]3- (5) species [log K = -1.96], whereas 4 reacted readily with H2O to form a μ-oxo bridged dimer {[SbW9O33(tBuSiO)3Ti]2O}6- (6). The more confined was the coordination site, the more hydrophobic was the metal complex. By studying the reaction of 3 and 4 with hydrogen peroxide using NMR and Raman spectroscopies, we concluded that the reaction leads to the formation of a titanium-hydroperoxide Ti-(η1-OOH) moiety, which is directly involved in the epoxidation of the allylic alcohol 3-methyl-2-buten-1-ol. The combined use of both spectroscopies also led to understanding that a shift of the acid-base equilibrium toward the formation of Ti(η2-O2) and H3O+ correlates with the partial hydrolysis of the phosphotungstate scaffold in 3. In that case, the release of protons also catalyzed the oxirane opening of the in situ formed epoxide, leading to an increased selectivity for 1,2,3-butane-triol. In the case of the more stable [SbW9O33(tBuSiO)3Ti(OiPr)]3- (4), the evolution to Ti(η2-O2) peroxide was not detected by Raman spectroscopy, and we performed reaction progress kinetic analysis by NMR monitoring the 3-methyl-2-buten-1-ol epoxidation to assess the efficiency and integrity of 4 as precatalyst.
- Zhang, Teng,Mazaud, Louis,Chamoreau, Lise-Marie,Paris, Céline,Proust, Anna,Guillemot, Geoffroy
-
p. 2330 - 2342
(2018/03/13)
-
- Identifying catalytically active mononuclear peroxoniobate anion of ionic liquids in the epoxidation of olefins
-
The organic carboxylic acid coordinated monomeric peroxoniobate-based ionic liquids (ILs) [TBA][NbO(OH)2(R)] (TBA = tetrabutylammonium; R = lactic acid (LA), glycolic acid (GLY), malic acid (MA)) were prepared and fully characterized by elemental analysis, NMR, IR, Raman, TGA, 93Nb NMR, and HRMS. These IL catalysts exhibited not only high catalytic activity for the epoxidation of olefins under very mild reaction conditions, as the turnover frequency of [TBA][NbO(OH)2(LA)] reached up to 110 h-1, but also satisfactory recyclability in the epoxidation by using only 1 equiv of hydrogen peroxide as an oxidant. Meanwhile, this work revealed that the ILs underwent structural transformation from [NbO(OH)2(R)]- to [Nb(O-O)2(R)]- (R = LA, GLY, MA) in the presence of H2O2 by a subsequent activity evaluation, characterization, and first-principles calculations. Moreover, the organic carboxylic acid coordinated monomeric peroxoniobate-based ILs were investigated using density functional theory (DFT) calculations, which identified that [Nb(O-O)2LA]- was more advantageous than [Nb(O-O)2(OOH)2]- for the epoxidation of olefins. Due to the coordination between the α-hydroxy acids and the monomeric peroxoniobate anions, the functionalized ILs can efficiently catalyze the epoxidation of a wide range of olefins and allylic alcohols under very mild conditions. Additionally, the effect of solvents on the reaction is illustrated. It was found that methanol can lower the epoxidation barriers by forming a hydrogen bond with a peroxo ligand attached to the niobium center.
- Ma, Wenbao,Yuan, Haiyang,Wang, Haifeng,Zhou, Qingqing,Kong, Kang,Li, Difan,Yao, Yefeng,Hou, Zhenshan
-
p. 4645 - 4659
(2018/05/08)
-
- Monolacunary K8SiW11O39-Catalyzed Terpenic Alcohols Oxidation with Hydrogen Peroxide
-
Abstract: Lacunar potassium undecasilicotungstate salt catalyst was highly efficient in oxidation reactions of terpenic alcohols with hydrogen peroxide. Carbonylic products were selectively obtained from alcohols such as borneol, nerol, geraniol and β-citronellol. The K8SiW11O39 catalyst was synthesized in one pot reaction starting from precursor salts (KCl, Na2WO4, and Na2SiO3). The catalyst salt was characterized by FT-IR, TG/DSC, BET, XRD analyses and potentiometric titration. The main reaction parameters were assessed. Based on experimental data, a reaction pathway was proposed. In borneol oxidation, TON of 2720 was achieved, indicating the high catalytic activity. As far we know, it is the first time where the monolacunar catalyst is used without an additional introduction of metal transition into Keggin anion. A comparison of the catalytic performance of different lacunar silicotungstic acid salts exchanged with different cations was performed. The K8SiW11O39 catalyst was used without loss activity.
- da Silva, Márcio José,da Silva Andrade, Pedro Henrique,Ferreira, Sukarno Olavo,Vilanculo, Castelo Bandane,Oliveira, Cesar Macedo
-
p. 2516 - 2527
(2018/06/07)
-
- Total synthesis of lycopene-5,6-diol and γ-carotene-5′,6′-diol stereoisomers and their HPLC separation
-
Lycopene-5,6-diol stereoisomers (1a,b) and (2a,b) and γ-carotene-5′,6′-diol stereoisomers (3a,b) and (4a,b) were synthesized by a stepwise C15?+?C10?+?C15 double Wittig reaction strategy. The key compounds erythro(anti)-C15-dihydroxy aldehydes 17a,b and their threo(syn)-stereoisomers 23a,b were prepared via Sharpless asymmetric epoxidation of geraniol and nerol followed by acidic hydrolysis of the epoxides in a stereospecific manner. The enantiomerically enriched anti-isomers were obtained by way of recrystallization of 2,3-epoxygeranyl 3,5-dinitrobenzoates 9a,b, whereas syn-isomers were obtained as enantiomerically pure forms via recrystallization of dihydroxyneryl 3,5-dinitrobenzoates 21a,b. In order to determine the absolute stereochemistry of natural products, HPLC separation methods for each enantiomers 1a,b–4a,b were established by using a column carrying a chiral stationary phase.
- Yamano, Yumiko,Nishiyama, Yuya,Aoki, Atsushi,Maoka, Takashi,Wada, Akimori
-
p. 2043 - 2052
(2017/03/17)
-
- Asymmetric Synthesis of the Antiviral Diterpene Wickerol A
-
Wickerol A (1) is an unusual diterpene with remarkable activity against the H1N1 influenza virus. Its tetracyclic skeleton contains three quaternary carbons and is marked by several syn-pentane interactions which force a six-membered ring into a twist-boat conformation. We present an asymmetric synthesis of wickerol A (1) that is based on a Jung Diels-Alder reaction, an intramolecular alkylation to complete the 6-5-6-6 ring system, and a conjugate addition, all of which overcome considerable steric strain. During the synthesis, we isolated an unexpected cyclopropane that presumably stems from a carbonium ion intermediate.
- Liu, Shu-An,Trauner, Dirk
-
supporting information
p. 9491 - 9494
(2017/07/24)
-
- Peroxotantalate-Based Ionic Liquid Catalyzed Epoxidation of Allylic Alcohols with Hydrogen Peroxide
-
The efficient and environmentally benign epoxidation of allylic alcohols has been attained by using new kinds of monomeric peroxotantalate anion-functionalized ionic liquids (ILs=[P4,4,4,n]3[Ta(O)3(η-O2)], P4,4,4,n=quaternary phosphonium cation, n=4, 8, and 14), which have been developed and their structures determined accordingly. This work revealed the parent anions of the ILs underwent structural transformation in the presence of H2O2. The formed active species exhibited excellent catalytic activity, with a turnover frequency for [P4,4,4,4]3[Ta(O)3(η-O2)] of up to 285 h?1, and satisfactory recyclability in the epoxidation of various allylic alcohols under very mild conditions by using only one equivalent of hydrogen peroxide as an oxidant. NMR studies showed the reaction was facilitated through a hydrogen-bonding mechanism, in which the peroxo group (O–O) of the peroxotantalate anion served as the hydrogen-bond acceptor and hydroxyl group in the allylic alcohols served as the hydrogen-bond donor. This work demonstrates that simple monomeric peroxotantalates can catalyze epoxidation of allylic alcohols efficiently.
- Ma, Wenbao,Chen, Chen,Kong, Kang,Dong, Qifeng,Li, Kun,Yuan, Mingming,Li, Difan,Hou, Zhenshan
-
p. 7287 - 7296
(2017/05/31)
-
- Facile fabrication of magnetic MoO2–Salen-modified graphene-based catalyst for epoxidation of alkenes
-
A facile, green and efficient method for the immobilization of MoO2–Salen onto graphene hybridized with glucose-coated magnetic Fe3O4 nanoparticles is proposed to fabricate a magnetic organic–inorganic hybrid heterogeneous RGO/Fe3O4@C-Salen-MoO2 catalyst for the epoxidation of cyclooctene and geraniol using tert-butyl hydroperoxide or H2O2 as oxidant. Carbon-coated Fe3O4 can improve the stability and add functional ─OH groups on the surface of Fe3O4. The fabricated composite exhibited good performance due to good dispersion of MoO2–Salen active sites. The catalyst can be easily separated from the reaction system using a permanent magnet and used three times without significantly losing its catalytic activity and selectivity.
- Li, Zhifang,Yang, Changlong,Ma, Yuanyuan,Li, Peng,Guan, Jingqi,Kan, Qiubin
-
-
- Structure-Function Studies of Artemisia tridentata Farnesyl Diphosphate Synthase and Chrysanthemyl Diphosphate Synthase by Site-Directed Mutagenesis and Morphogenesis
-
The amino acid sequences of farnesyl diphosphate synthase (FPPase) and chrysanthemyl diphosphate synthase (CPPase) from Artemisia tridentata ssp. Spiciformis, minus their chloroplast targeting regions, are 71% identical and 90% similar. FPPase efficiently and selectively synthesizes the "regular" sesquiterpenoid farnesyl diphosphate (FPP) by coupling isopentenyl diphosphate (IPP) to dimethylallyl diphosphate (DMAPP) and then to geranyl diphosphate (GPP). In contrast, CPPase is an inefficient promiscuous enzyme, which synthesizes the "irregular" monoterpenes chrysanthemyl diphosphate (CPP), lavandulyl diphosphate (LPP), and trace quantities of maconelliyl diphosphate (MPP) from two molecules of DMAPP, and couples IPP to DMAPP to give GPP. A. tridentata FPPase and CPPase belong to the chain elongation protein family (PF00348), a subgroup of the terpenoid synthase superfamily (CL0613) whose members have a characteristic α terpene synthase α-helical fold. The active sites of A. tridentata FPPase and CPPase are located within a six-helix bundle containing amino acids 53 to 241. The two enzymes were metamorphosed into one another by sequentially replacing the loops and helices of the six-helix bundle from enzyme with those from the other. Chain elongation was the dominant activity during the N-terminal to C-terminal metamorphosis of FPPase to CPPase, with product selectivity gradually switching from FPP to GPP, until replacement of the final α-helix, whereupon cyclopropanation and branching activity competed with chain elongation. During the corresponding metamorphosis of CPPase to FPPase, cyclopropanation and branching activities were lost upon replacement of the first helix in the six-helix bundle. Mutations of active site residues in CPPase to the corresponding amino acids in FPPase enhanced chain-elongation activity, while similar mutations in the active site of FPPase failed to significantly promote formation of significant amounts of irregular monoterpenes. Our results indicate that CPPase, a promiscuous enzyme, is more plastic toward acquiring new activities, whereas FPPase is more resistant. Mutations of residues outside of the α terpene synthase fold are important for acquisition of FPPase activity for synthesis of CPP, LPP, and MPP.
- Lee, J. Scott,Pan, Jian-Jung,Ramamoorthy, Gurusankar,Poulter, C. Dale
-
supporting information
p. 14556 - 14567
(2017/10/24)
-
- Catalytic homogeneous oxidation of monoterpenes and cyclooctene with hydrogen peroxide in the presence of sandwich-type tungstophosphates [M4(H2O)2(PW9O34)2]n?, M = CoII, MnII and FeIII
-
Catalytic efficiency of tetrabutylammonium salts of sandwich tungstophosphates B‐α‐[M4(H2O)2(PW9O34)2]n?, M = CoII, MnII, FeIII, was studied in the oxidation of (R)-(+)-limonene, geraniol, linalool, linalyl acetate, carveol, and cis-cyclooctene with hydrogen peroxide, in acetonitrile. Oxidation of (R)-(+)-limonene gave limonene-1,2-diol as main product. Epoxidation of linalool takes place preferentially at the more substituted 6,7-double bond, the corresponding 6,7-epoxide reacting further, yielding furano- and pyrano-oxides, via intramolecular cyclization. Oxidation of linalyl acetate occurred preferentially at the more substituted 6,7-double bond for Mn4(PW9)2, affording 6,7-epoxide at 82% selectivity. Linalyl acetate 1,2-epoxide was the major product with 51% and 77% selectivity for Co4(PW9)2 and Fe4(PW9)2, respectively. Oxidation of carveol occurred with very good conversions in the presence of Mn4(PW9)2, Co4(PW9)2 and Fe4(PW9)2, yielding carvone and carveol 1,2-epoxide in similar amounts. Oxidation of cis-cyclooctene gave only the epoxide, while oxidation of geraniol at room temperature afforded 2,3-epoxygeraniol as the major product.
- Santos, Isabel C.M.S.,Gamelas, José A.F.,Duarte, Tiago A.G.,Sim?es, Mário M.Q.,Neves, M. Gra?a P.M.S.,Cavaleiro, José A.S.,Cavaleiro, Ana M.V.
-
p. 593 - 599
(2016/12/16)
-
- Effect of citral and citral related compounds on viability of pancreatic and human B-lymphoma cell lines
-
Citral, 3,7-dimethyl-2,6-octadienal, is a key component of the essential oils extracted from several lemon-scented herbal plants. It has been demonstrated to be an effective antifungal agent and in recent years, to have antiproliferative effect in certain tumor cell lines: thus citral could be a potential anticancer drug. In this study, we investigated the effect of citral on the proliferation of pancreatic cell tumor lines (MIA PaCa-2 cells) and human B-lymphoma (DeFew cells). To analyze which part of the molecule is pivotal for the activity, we also studied the effect of several citral related compounds, in particular focusing on some chemical aspects of the terpenic scaffold. The in vitro studies revealed the significant cytotoxic activity of some of the tested compounds.
- Di Mola, Antonia,Massa, Antonio,De Feo, Vincenzo,Basile, Anna,Pascale, Maria,Aquino, Rita Patrizia,De Caprariis, Paolo
-
p. 631 - 639
(2017/02/15)
-
- α,β-Unsaturated Gold(I) Carbenes by Tandem Cyclization and 1,5-Alkoxy Migration of 1,6-Enynes: Mechanisms and Applications
-
1,6-Enynes bearing OR groups at the propargyl position generate α,β-unsaturated gold(I)-carbenes/ gold(I) stabilized allyl cations that can be trapped by alkenes to form cyclopropanes or 1,3-diketones to give products of α-alkylation. The best migrating group is p-nitrophenyl ether, which leads to the corresponding products without racemization. Thus, an improved formal synthesis of (+)-schisanwilsonene A has been accomplished. The different competitive reaction pathways have been delineated computationally.
- Calleja, Pilar,Pablo, óscar,Ranieri, Beatrice,Gaydou, Morgane,Pitaval, Anthony,Moreno, María,Raducan, Mihai,Echavarren, Antonio M.
-
supporting information
p. 13613 - 13618
(2016/09/13)
-
- Synthesis and Biological Evaluation of New (-)-Englerin Analogues
-
We report the synthesis and biological evaluation of a series of (-)-englerin A analogues obtained along our previously reported synthetic route based on a stereoselective gold(I) cycloaddition process. This synthetic route is a convenient platform to access analogues with broad structural diversity and has led us to the discovery of unprecedented and easier-to-synthesize derivatives with an unsaturation in the cyclopentyl ring between C4 and C5. We also introduce novel analogues in which the original isopropyl motif has been substituted with cyclohexyl, phenyl, and cyclopropyl moieties. The high selectivity and growth-inhibitory activity shown by these new derivatives in renal cancer cell lines opens new ways toward the final goal of finding effective drugs for the treatment of renal cell carcinoma (RCC).
- López-Suárez, Laura,Riesgo, Lorena,Bravo, Fernando,Ransom, Tanya T.,Beutler, John A.,Echavarren, Antonio M.
-
supporting information
p. 1003 - 1007
(2016/05/24)
-
- Highly Efficient Epoxidation of Allylic Alcohols with Hydrogen Peroxide Catalyzed by Peroxoniobate-Based Ionic Liquids
-
This work reports new kinds of monomeric peroxoniobate anion functionalized ionic liquids (ILs) designated as [A+][Nb=O(O-O)(OH)2] (A+ = tetrapropylammonium, tetrabutylammonium, or tetrahexylammonium cation), which have been prepared and characterized by elemental analysis, HRMS, NMR, IR, TGA, etc. With hydrogen peroxide as an oxidant, these ILs exhibited excellent catalytic activity and recyclability in the epoxidation of various allylic alcohols under solvent-free and ice bath conditions. Interestingly, subsequent activity tests and catalyst characterization together with first-principles calculations indicated that the parent [Nb=O(O-O)(OH)2]- anion has been oxidized into the anion [Nb(O-O)2(OOH)2]- in the presence of H2O2, which constitutes the real catalytically active species during the reaction; this anion has higher activity in comparison to the analogous peroxotungstate anion. Moreover, the epoxidation process of the substrate (allylic alcohol) catalyzed by [Nb(O-O)2(OOH)2]- was explored at the atomic level by virtue of DFT (density functional theory) calculations, identifying that it is more favorable to occur through a hydrogen bond mechanism, in which the peroxo group of [Nb(O-O)2(OOH)2]- serves as the adsorption site to anchor the substrate OH group by forming a hydrogen bond, while OOH as the active oxygen species attacks the C=C bond in substrates to produce the corresponding epoxide. This is the first example of the highly efficient epoxidation of allylic alcohols using a peroxoniobate anion as a catalyst.
- Chen, Chen,Yuan, Haiyang,Wang, Haifeng,Yao, Yefeng,Ma, Wenbao,Chen, Jizhong,Hou, Zhenshan
-
p. 3354 - 3364
(2016/07/06)
-
- Calcium tungstate: A convenient recoverable catalyst for hydrogen peroxide oxidation
-
Calcium tungstate was found to be an excellent catalyst for large scale "green" oxidations of organic substrates (amines, alkenes, alcohols, sulfides) with hydrogen peroxide. It displays the unusual dual characteristics of producing a soluble pertungstate species, allowing for homogeneous reaction conditions, but then precipitating, unchanged, at the end of the oxidation. These qualities allow for easy catalyst recovery and minimal waste stream generation for large scale application.
- Tressler, Caitlin M.,Stonehouse, Peter,Kyler, Keith S.
-
p. 4875 - 4878
(2016/10/06)
-
- Substrate-Controlled Product Divergence: Conversion of CO2 into Heterocyclic Products
-
Substituted epoxy alcohols and amines allow substrate-controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach results in an unusual scope of CO2-derived products by initial activation of CO2 through either the amine or alcohol unit, thus providing nucleophiles for intramolecular epoxy ring opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile-assisted ring-opening step following an SNi pathway, and a 5-exo-tet cyclization, thus leading to heterocyclic scaffolds.
- Rintjema, Jeroen,Epping, Roel,Fiorani, Giulia,Martín, Eddy,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
-
supporting information
p. 3972 - 3976
(2016/03/19)
-
- Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic acid complex
-
A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.
- Noji, Masahiro,Kobayashi, Toshihiro,Uechi, Yuria,Kikuchi, Asami,Kondo, Hisako,Sugiyama, Shigeo,Ishii, Keitaro
-
supporting information
p. 3203 - 3210
(2015/03/30)
-
- Oxidative cyclization of tertiary pentenol derivatives forming 2,5,5-trisubstituted THF rings and the total synthesis of cyclocapitelline
-
The synthesis of 2,5,5-trisubstituted tetrahydrofuran rings was accomplished via the Mukaiyama aerobic oxidative cyclization of tertiary 5-pentenols employing the Co(nmp)2 catalyst. A variety of THFs were formed in moderate to good yield and diastereoselectivity. The method developed herein was successfully applied to an enantioselective total synthesis of cyclocapitelline.
- Phillips, Geoffrey A.,Palmer, Cory,Stevens, Andrew C.,Piotrowski, Mathew L.,Dekruyf, Daryl S.R.,Pagenkopf, Brian L.
-
supporting information
p. 6052 - 6055
(2015/10/28)
-
- Catalytic activity of molybdenum(II) complexes in homogeneous and heterogeneous conditions
-
The new complexes [MoBr(η3-C3H5)(CO)2(L)2] (C1) and [MX2(CO)3(L)2] (M = Mo(II), X = I (C2); M = Mo(II), X = Br (C3); M = W(II), X = I (C4); M = W(II), X = Br (C5)) were synthesized by reaction of 2-amino-1,3,4-thiadiazole (L) with [MoBr(η3-C3H5)(CO)2(NCCH3)2] (1), [MoI2(CO)3(CH3CN)2](M = Mo (2); M = W (4)), or [MoBr2(CO)3(CH3CN)2](M = Mo (3); M = W (5)) in 2:1 ratio. The five complexes were immobilized in MCM-41, yielding the materials MCM-Cn (n = 1-5), and C1 was also immobilized in silica gel (Silica-C1) and in a polyhedral oligomeric silsesquioxane (Cube-C1). Complexes and materials were fully characterized by spectroscopic techniques and elemental analysis. DFT calculations showed that several C1 isomers should coexist. The as synthesized and supported complexes were tested as catalysts on the oxidation of geraniol, cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, (S)-limonene, and 1-octene. The conversions and TOF significantly depend on the complex and the nature of the substrate. The general conclusions are (i) complex C1 has the highest activity; (ii) tungsten complexes C4 and C5 are more active than the molybdenum analogues; (iii) the immobilization of the catalysts improves the performance; and (iv) silica gel and the polyhedral oligomeric silsesquioxane supports modify the selectivity, leading to products different from the one obtained with MCM for specific substrates.
- Vasconcellos Dias, Maria,Saraiva, Marta S.,Ferreira, Paula,Calhorda, Maria José
-
p. 1465 - 1478
(2015/05/13)
-
- An immobilized imidazolyl manganese porphyrin for the oxidation of olefins
-
A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the oxidation of olefins is presented. Merrifield resin (MR) and functionalized silica gel (SG) were chosen as supports. The results indicate that the MR system shows high reaction rates, high efficiency with hydrogen peroxide as oxidant and good recyclability up to four times, without a dramatic loss in the catalytic efficiency. The catalytic behavior seems to be strongly influenced by the immobilization reaction conditions. The oxidation reactions performed for cis-cyclooctene, styrene, cyclohexene and geraniol give the corresponding epoxides, with very high selectivity, when the MR system is used. Some considerations concerning the high efficiency of the MR system are put forward.
- De Paula, Rodrigo,Santos, Isabel C.M.S.,Sim?es, Mário M.Q.,Neves, M. Gra?a P.M.S.,Cavaleiro, José A.S.
-
p. 156 - 166
(2015/05/13)
-
- Pore size matters! Helical heterogeneous catalysts in olefin oxidation
-
Helical mesoporous materials of the MCM-41 type with different pore sizes were prepared, choosing as templates myristyl (C14) or cetyl (C16) trimethyl ammonium salts, and functionalized with Mo(II) active sites based on MoI2(CO)3 (1) and MoBr(η3-C3H5)(CO)2 (2) fragments, respectively, using a pyridine-2-carbaldehyde ligand as anchor. The new materials were tested as the catalytic precursors in the epoxidation of cis-cyclooctene, styrene, R-(+)-limonene, trans-hex-2-en-1-ol, cis-3-hex-1-ol, and geraniol using tert-butylhydroperoxide (tbhp) as oxidant. All catalysts were moderately to highly selective toward the epoxide products. The materials with larger pores (C16 template) displayed a better catalytic activity, leading in general to higher conversions and selectivities, as well as faster kinetics. For instance, geraniol is epoxidized (more than 90%) with conversions above 90%. The major achievement of these catalysts, however, is the excellent product selectivity control, which is boosted when the allyl complex 1 is used, reaching 100% of the 2S, 3R species in the epoxidation of trans-hex-2-en-1-ol. The catalysts were also found to be stable through recycling experiments and truly heterogeneous with little or no leaching.
- Saraiva, Marta S.,Fernandes, Cristina I.,Nunes, Teresa G.,Calhorda, Maria José,Nunes, Carla D.
-
p. 328 - 337
(2015/10/05)
-
- Intramolecular hydroalkoxylation catalyzed inside a self-assembled cavity of an enzyme-like host structure
-
Self-assembled resorcin[4]arene hexamer catalyzes the intramolecular hydroalkoxylation of unsaturated alcohols to the corresponding cyclic ethers under mild conditions. The mode of catalysis and encapsulation-based substrate selectivity of the host efficiently mimic the basic principle of operation observed in enzymes.
- Catti,Tiefenbacher
-
supporting information
p. 892 - 894
(2015/02/05)
-
- Selective allylic hydroxylation of acyclic terpenoids by CYP154E1 from Thermobifida fusca YX
-
Allylic alcohols are valuable precursors in the synthesis of pharmaceutical intermediates, agrochemicals and natural products. Regioselective oxidation of parental alkenes is a challenging task for chemical catalysts and requires several steps including protection and deprotection. Many cytochrome P450 enzymes are known to catalyse selective allylic hydroxylation under mild conditions. Here, we describe CYP154E1 from Thermobifida fusca YX that enables this type of oxidation. Several acyclic terpenoids were tested as possible substrates for CYP154E1, and the regio- and chemoselectivity of their oxidation was investigated. Using a previously established bioinformatics approach we identified position 286 in the active site of CYP154E1 which is putatively involved in substrate binding and thereby might have an effect on enzyme selectivity. To tune regio- and chemoselectivity of the enzyme three mutants at position 286 were constructed and used for substrate oxidation. All formed products were analysed with GC-MS and identified using chemically synthesised authentic samples and known compounds as references. Best regioselectivity towards geraniol and nerol was observed with the wild type enzyme mainly leading to 8-hydroxy derivatives (8-hydroxygeraniol or 8-hydroxynerol) with high selectivity (100% and 96% respectively). Highest selectivities during the oxidation of geranylacetone and nerylacetone were observed with the following variants: V286F led mainly to 7-hydroxygeranylacetone (60% of the total product) and V286A produced predominantly 12-hydroxynerylacetone (75% of total product). Thus, CYP154E1 and its mutants expand the tool-box for allylic hydroxylation in synthetic chemistry.
- Bogazkaya, Anna M.,Von Buehler, Clemens J.,Kriening, Sebastian,Busch, Alexandrine,Seifert, Alexander,Pleiss, Juergen,Laschat, Sabine,Urlacher, Vlada B.
-
supporting information
p. 1347 - 1353
(2014/07/22)
-
- Geranyl and neryl triazole bisphosphonates as inhibitors of geranylgeranyl diphosphate synthase
-
When inhibitors of enzymes that utilize isoprenoid pyrophosphates are based on the natural substrates, a significant challenge can be to achieve selective inhibition of a specific enzyme. One element in the design process is the stereochemistry of the isoprenoid olefins. We recently reported preparation of a series of isoprenoid triazoles as potential inhibitors of geranylgeranyl transferase II but these compounds were obtained as a mixture of olefin isomers. We now have accomplished the stereoselective synthesis of these triazoles through the use of epoxy azides for the cycloaddition reaction followed by regeneration of the desired olefin. Both geranyl and neryl derivatives have been prepared as single olefin isomers through parallel reaction sequences. The products were assayed against multiple enzymes as well as in cell culture studies and surprisingly a Z-olefin isomer was found to be a potent and selective inhibitor of geranylgeranyl diphosphate synthase.
- Zhou, Xiang,Ferree, Sarah D.,Wills, Veronica S.,Born, Ella J.,Tong, Huaxiang,Wiemer, David F.,Holstein, Sarah A.
-
p. 2791 - 2798
(2014/05/06)
-
- Total synthesis of heronapyrrole C
-
A flexible total synthesis of the 2-nitropyrrole-derived marine natural product, (+)-heronapyrrole C, is reported. The approach is based on regioselective access to key building blocks containing the rare 4-substituted 2-nitropyrrole motif. Sharpless asymmetric epoxidation and dihydroxylation and a Shi epoxidation were used to introduce the five stereogenic centers of the bis-THF-diol side chain. The N-benzoyloxymethyl (Boz) protecting group was crucial for functionalization of the 2-nitropyrrole moiety and enabling final deprotection under mild conditions.
- Ding, Xiao-Bo,Furkert, Daniel P.,Capon, Robert J.,Brimble, Margaret A.
-
supporting information
p. 378 - 381
(2014/04/03)
-