- Reactions of Sodium Diisopropylamide: Liquid-Phase and Solid-Liquid Phase-Transfer Catalysis by N, N, N′, N″, N″-Pentamethyldiethylenetriamine
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Sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) and DMEA-hydrocarbon mixtures with added N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDTA) reacts with alkyl halides, epoxides, hydrazones, arenes, alkenes, and allyl ethers. Comparisons of PMDTA with N,N,N′,N′-tetramethylethylenediamine (TMEDA) accompanied by detailed rate and computational studies reveal the importance of the trifunctionality and κ2-κ3 hemilability. Rate studies show exclusively monomer-based reactions of 2-bromooctane, cyclooctene oxide, and dimethylresorcinol. Catalysis with 10 mol % PMDTA shows up to >30-fold accelerations (kcat > 300) with no evidence of inhibition over 10 turnovers. Solid-liquid phase-transfer catalysis (SLPTC) is explored as a means to optimize the catalysis as well as explore the merits of heterogeneous reaction conditions.
- Algera, Russell F.,Collum, David B.,Ma, Yun,Woltornist, Ryan A.
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supporting information
p. 13370 - 13381
(2021/09/03)
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- Selectively oxidized carbon nanocatalysts for the oxidation of: Cis -cyclooctene
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In this work, selectively oxidized carbon nanotubes and graphene flakes were used as carbocatalysts in the mild oxidation of cis-cyclooctene. Firstly, the multi-walled carbon nanotubes and graphene flakes were oxidized using three different oxidation procedures: (i) nitric acid treatment; (ii) nitric acid followed by thermal treatment at 400 °C; (iii) gas phase oxidation with O2, and subsequently characterized by several techniques. Both oxidized nanomaterials showed an overall increase in the oxygen content and revealed that the different oxidation procedures promoted different superficial chemical compositions: nitric acid treated carbon nanotubes and graphene flakes (respectively, MWCNTh and GFh) presented increased amounts of carboxylic acids, anhydrides and phenols up to 552, 84, and 648 μmol g-1, respectively, for material MWCNTh, and 612, 120, and 1392 μmol g-1, respectively, for material GFh; the nanomaterials treated with nitric acid followed by thermal treatment at 400 °C (MWCNTht and GFht) presented a loss of carboxylic acids and an increase in carboxylic anhydride content (36 and 132 μmol g-1, respectively, for material MWCNTht, and 36 and 156 μmol g-1, respectively, for material MWCNTht), when compared to the nitric acid treated materials MWCNTh and GFh; and finally the gas phase treated nanomaterials, MWCNTo and GFo, presented an increase in the amounts of phenols, carbonyls/quinones, and lactones up to 720, 216, and 144 μmol g-1, respectively, for material MWCNTo, and 804, 420, and 144 μmol g-1, respectively, for material GFo. The carbon nanocatalysts showed activity in the selective oxidation of cis-cyclooctene to epoxycyclooctane using mild conditions: hydrogen peroxide was used as oxidant at 80 °C. The modifications introduced in the pristine materials through nitric acid followed by thermal treatment at 400 °C originated the nanocatalysts with the best activity and selectivity: MWCNTht presented 47% of substrate conversion and 79% epoxycyclooctane selectivity whereas GFht showed 57% conversion and 85% epoxycyclooctane selectivity. Reusability experiments revealed no loss of catalytic activity up to three catalytic cycles. The results indicate that the fine tuning of the carbon nanomaterials through appropriate oxidation procedures is crucial in achieving metal-free carbocatalysts with enhanced performance and selectivity in selective oxidation reactions.
- Jarrais, Bruno,Guedes, Alexandra,Freire, Cristina
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p. 2306 - 2319
(2018/02/07)
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- Sodium Diisopropylamide in N,N-Dimethylethylamine: Reactivity, Selectivity, and Synthetic Utility
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The reactivities and chemoselectivities of sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) are compared with those of lithium diisopropylamide (LDA) in tetrahydrofuran (THF). Metalations of arenes, epoxides, ketones, hydrazones, dienes, and alkyl and vinyl halides are represented. The positive attributes of NaDA-DMEA include high solubility, stability, resistance to solvent decomposition, and ease of preparation. The high reactivities and chemoselectivities often complement those of LDA-THF.
- Ma, Yun,Algera, Russell F.,Collum, David B.
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p. 11312 - 11315
(2016/11/29)
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- Novel transition-metal-free heterogeneous epoxidation catalysts discovered by means of high-throughput experimentation
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Various transition-metal-free oxides have been studied as catalysts for the epoxidation of cyclooctene with hydrogen peroxide by means of high-throughput experimentation. Different boron, aluminium, and gallium oxides were prepared according to various synthesis methods. A number of pure aluminium and gallium oxides showed very good catalytic performances, while the results obtained with boron oxides or mixed oxides were less positive. The best results were obtained with a gallium oxide catalyst, which gave an epoxide yield of 71 % and a selectivity of 99% after reaction for 4 h at 80°C. Gallium oxides had not been reported previously as active epoxidation catalysts. The use of high-throughput experimentation proved useful both for discovering new active catalysts and for identifying a number of relationships between the synthesis conditions and the catalytic properties of the transition-metal-free oxides.
- Pescarmona, Paolo P.,Janssen, Kris P. F.,Jacobs, Pierre A.
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p. 6562 - 6572
(2008/03/15)
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- Efficient photocatalytic oxidation of cycloalkenes by dihydroxo(tetraphenylporphyrinato)-antimony supported on silica gel under visible light irradiation
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In order to develop a photocatalyst operating under visible light irradiation, silica gel-supported dihydroxo(tetraphenylporphyrinato)antimony (V) complex, [SbTPP(OH)2]+/SiO2, was prepared. The photocatalytic oxidation of cycloalkenes with oxygen molecule was performed on [SbTPP(OH)2]+/SiO2 particles under irradiation of fluorescent light. The photocatalytic oxidation of cycloalkenes gave the corresponding cis-1,2-epoxycycloalkane, 2-cycloalkene-1-ol, and trans-1,2-cycloalkanediol.
- Shiragami, Tsutomu,Makise, Ryu-Ichi,Inokuchi, Yousuke,Matsumoto, Jin,Inoue, Haruo,Yasuda, Masahide
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p. 736 - 737
(2007/10/03)
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- Photoinitiated olefin epoxidation with molecular oxygen, sensitized by free base porphyrins and promoted by hexacarbonylmolybdenum in homogeneous solution
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The photooxidation of various olefins in homogeneous solution under an oxygen atmosphere, by use of visible light, a dye sensitizer, and an oxygen-transfer catalyst, has been investigated. The oxygen transfer from molecular oxygen to olefin involves the following steps: i) photoinduced singlet-oxygen formation, ii) alkyl hydroperoxide formation through the ene reaction, iii) the intermediacy of a reactive molybdenum peroxide, and iv) olefin epoxidation of the remaining substrate or of a second olefin. Among the various sensitizers and catalysts tested, the electron- deficient free base porphyrin 5,10,15,20-tetrakis(2′,6′-dichlorophenyl) -β-octabromoporphyrin and hexacarbonylmolybdenum showed the best performances in terms of robustness and activity. Under suitable conditions, complete olefin conversion may be obtained by adoption of molar ratios of sensitizer/catalyst/substrate of 1:50:2000, with the formation of the corresponding epoxide in up to 38% yield, which corresponds to 77% of the theoretical maximum. Quite interestingly, olefins reluctant to undergo ene reactions may be epoxidized in the presence of a second sacrificial olefin, yielding the corresponding epoxides with up to 80% total selectivity. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Campestrini, Sandro,Tonellato, Umberto
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p. 3827 - 3832
(2007/10/03)
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- High turnover numbers for the catalytic selective epoxidation of alkenes with 1 atm of molecular oxygen
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The diiron-substituted silicotungstate γ-SiW10{Fe3+(OH2}2O 386- (schematically shown) is an effective catalyst for the oxygenation of alkenes in homogeneous reaction media with 1 atm of molecular oxygen. For example, a selectivity for cyclooctene oxide of 98% and a turnover number of 10000 were achieved in the epoxidation of cyclooctene. The catalyst is stable under the reaction conditions, and its ability to use molecular oxygen raises the prospect of using it in industrial epoxidation processes.
- Nishiyama, Yoshiyuki,Nakagawa, Yoshinao,Mizuno, Noritaka
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p. 3639 - 3641
(2007/10/03)
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- Reaction of cyclooctenes with singlet oxygen. Trapping of a perepoxide intermediate
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The products and rate constants for total physical and chemical quenching (kq + kr) of singlet oxygen (1O2) by cis- and trans-cyclooctene were determined in two solvents of different polarity. Small amounts of cis-cyclooctene are produced during the reaction of the trans-isomer. In CDCl3 and acetone-d6, kq + kr for cis-cyclooctene was 1.3 × 104 M-1 s-1 while the rate constants (kr) for the reaction of trans-cyclooctene were 2.3 × 104 and 3.4 × 104 M-1 s-1, respectively. Competition experiments with 2-methyl-2-pentene (2M2P) suggest a substantial contribution of physical quenching for the trans-alkene while the cis-alkene removes 1O2 mostly by chemical reaction. The physical quenching of 1O2 by trans-cyclooctene is explained by a perepoxide intermediate which can open to a zwitterion that can abstract an allylic hydrogen to give the 3-hydroperoxycyclooctene ene product or isomerize and lose O2 to form cis-cyclooctene. A perepoxide intermediate can be trapped using triphenyl phosphite with trans-but not cis-cyclooctene. trans-Cyclooctene quenches 3C70 with a rate constant of 3.4 × 105 M-1 s-1.
- Poon, Thomas H. W.,Pringle, Kenneth,Foote, Christopher S.
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p. 7611 - 7618
(2007/10/02)
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- Dioxygen ligand transfer from platinum to molybdenum. Isolation of a highly reactive molybdenum(VI) oxoperoxo dimer
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The reaction of Pt(O2)(PPh3)2 with Mo(O)2(mesityl)2 (mesityl = 2,4,6-Me3C6H2) in pyridine results in the transfer of the dioxygen ligand from platinum to molybdenum giving, in the presence of PPh4Cl, a molybdenum peroxo compound 1 in which all the organic moieties have been lost.This compound epoxidizes tetracyanoethylene at a rate estimated at 104 greater than the known oxodiperoxomolybdenum complex 2.Furthermore, 1 exhibits a high selectivity for electron-poor olefins (TCNE/cyclooctene = 103).Elemental analysis, IR and 17O NMR indicate that 1 is the tetraphenylphosphonium salt of an oxoperoxomolybdenum(VI) dimer. - Keywords: dioxygen transfer; platinum peroxo; molybdenum oxoperoxo; epoxidation
- Arzoumanian, Henri,Sanchez, Jose,Strukul, Giorgio,Zennaro, Roberto
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p. 1119 - 1122
(2007/10/03)
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- Isomerization of Cyclooctene and Cyclododecene Oxides Catalyzed by Solid Acids and Bases
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The title reactions were carried out over seven catalysts.From cyclooctene oxide a large amount of 7-octenal was formed together with 3-cycloocten-1-ol over SiO2-Al2O3 and SiO2-TiO2, 3-cycloocten-1-ol over solid H3PO4, and cyclooctanone over FeSO4.Most catalysts except for NiSO4, Al2O3, and Tio2-ZrO2 produced 1,3-cyclododecadiene, cyclododecanone, and 2-cyclododecen-1-ol uniformly from cyclododecene oxide.Allylic alcohols were preferentially given by Al2O3 and TiO2-ZrO2.
- Arata, Kazushi,Nakamura, Hideo,Nakamura, Yuki
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p. 2351 - 2353
(2007/10/02)
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- Direct Epoxy Alcohol Synthesis from Cyclic Olefins Using O2 and VO(acac)2-AIBN Catalyst System
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The vanadium-catalyzed oxidation of cyclic olefins with molecular oxygen is examined.The VO(acac)2-AIBN system is an efficient catalyst for epoxy alcohol synthesis.Chloro hydrocarbons such as 1,2-dichloroethane and 1,1,2-trichloroethane are suitable solvents for the epoxidation reaction.Cyclohexene (1), methylcyclohexene (2), and cyclododecene (5) give the corresponding epoxy alcohols in good yields; in the case of 2 with VO(acac)2-AIBN system, the selectivity to epoxy alcohol reaches over 70percent. 1,4-Cyclooctadiene (7) is oxidized to give 9-oxabicyclonon-3-en-exo-2-ol (6a) via the rearrangement of cis-2,3-epoxycyclooct-4-en-1-ol.Exceptional is cyclooctene (4), which gives exclusively cyclooctene oxide (4b).
- Kaneda, Kiyotomi,Jitsukawa, Koichiro,Itoh, Takashi,Teranishi, Shiichiro
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p. 3004 - 3009
(2007/10/02)
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