- Comparison of isoelectronic 8-HO-G and 8-NH2-G derivatives in redox processes
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8-Oxo-7,8-dihydroguanine (8-oxo-G) is the major lesion of oxidatively generated DNA damage. Despite two decades of intense study, several fundamental properties remain to be defined. Its isoelectronic 8-aminoguanine (8-NH 2-G) has also received considerable attention from a biological point of view, although its chemistry involving redox processes remains to be discovered. We investigated the one-electron oxidation and one-electron reduction reactions of 8-oxo-G and 8-NH2-G derivatives. The reactions of hydrated electrons (eaq-) and azide radicals (N 3?) with both derivatives were studied by pulse radiolysis techniques, and the transient absorption spectra were assigned to specific tautomers computationally by means of time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations. The protonated electron adducts of 8-NH2-G and 8-oxo-G showed a substantial difference in their absorption spectra, the unpaired electron being mainly delocalized in the imidazolyl ring and in the six-membered ring, respectively. On the other hand, the deprotonated forms of one-electron oxidation of 8-NH2-G and 8-oxo-G showed quite similar spectral characteristics. In a parallel study, the one-electron reduction of 8-azidoguanine (8-N3-G) afforded the same transient of one-electron oxidation of 8-NH2-G, which represents another example of generation of one-electron oxidized guanine derivatives under reducing conditions. Moreover, the fate of transient species was investigated by radiolytic methods coupled with product studies and allowed self- and cross-termination rate constants associated with these reactions to be estimated.
- Kaloudis, Panagiotis,D'Angelantonio, Mila,Guerra, Maurizio,Spadafora, Marie,Cismas, Crina,Gimisis, Thanasis,Mulazzani, Quinto G.,Chatgilialoglu, Chryssostomos
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Read Online
- PROCESS AND SYSTEM TO MAKE SUBSTITUTED LACTONES
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A process for oxidizing iso-butane with oxygen to produce t-butyl hydroperoxide and t-butyl alcohol; dehydrating at least a portion of the t-butyl alcohol to produce di-tert-butyl ether and isobutylene; epoxidizing at least a portion of the isobutylene with the t-butyl hydroperoxide to produce isobutylene oxide and t-butyl alcohol; and carbonylating at least a portion of the isobutylene oxide with carbon monoxide to produce pivalolactone.
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Paragraph 0052; 0055
(2021/02/05)
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- Method for epoxidizing small-molecular olefin
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The invention relates to a micromolecular olefin epoxidation method, which is characterized by comprising the following steps: contacting micromolecular olefin, an organic peroxide and a titanium-silicon composite oxide under epoxidation reaction conditions of at least two reaction temperatures of A and B to obtain an alkylene oxide-containing product, wherein the A is 80-95 DEG C, the B is 100-120 DEG C, the titanium-silicon composite oxide is of an amorphous structure, is formed by aggregation of nano-particles and has mesopores in the range of 16-50 nm, the ratio of the volume of the mesopores to the total pore volume is larger than or equal to 80%, and the volume of the mesopores is larger than or equal to 0.5 cm/g. According to the method, the amorphous titanium-silicon-titanium-silicon composite oxide is taken as the catalyst, and at least two sections of conditions with different reaction temperatures are combined, so that compared with the prior art, the catalyst is stable in structure, low in cost, high in olefin epoxidation reaction activity and good in product selectivity.
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Paragraph 0180-0181; 0214-0215
(2021/06/06)
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- Synthesis and Structure of Tin and Germanium Complexes as Precursors Containing Alkoxyaminoalkoxide Ligands for Thin Film Transistors
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This paper describes the preparation of four novel Sn and Ge complexes containing alkoxyaminoalkoxide type ligands {L1H = 1-[methoxy(methyl)amino]-2-methylpropan-2-ol; L2H = 1-[methoxy(methyl)amino]-2-methylbutan-2-ol} for potential use as precursors for thin film transistors. All compounds were prepared at room temperature by stirring a solution containing Sn(btsa)2 [btsa = bis(trimethylsilyl)amide] or Ge(btsa)2 with two equivalents of L1H or L2H to form Sn(L1)2 (1), Sn(L2)2 (2), Ge(L1)2 (3) and Ge(L2)2 (4). All of the complexes were characterized by NMR and FTIR spectroscopy as well as elemental and thermogravimetric analyses. When the more symmetric and compact ligand L1H was applied, solid products 1 and 3 were generated and their structures were studied using X-ray diffraction. Applying the strategy of ligand design at the molecular level, the symmetric ligand was changed to an asymmetric one, replacing one of the two neighboring methyl groups of the amino alcohol group with an ethyl group, and forming liquid complexes 2 and 4 for both metals.
- Chung, Taek-Mo,Han, Seong Ho,Jeon, Dong Ju,Kim, Chang Gyoun,Lee, Ga Yeon,Lee, Ji Hun,Park, Bo Keun,Son, Seung Uk
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- SYSTEMS AND METHODS FOR REGIOSELECTIVE CARBONYLATION OF 2,2-DISUBSTITUTED EPOXIDES
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Provided are methods of carbonylating cyclic substrates to produce carbonyl ated cyclic products. The cyclic substrates may be 2, 2-di substituted epoxides and the cyclic products may be β,β-di substituted lactones. The method may be carried out by forming and pressurizing a reaction mixture of the cyclic substrate, a solvent, carbon monoxide, and a [LA+][CO(CO)4-] catalyst, where [LA+] is a Lewis acid capable of coordinating to the cyclic substrate. The method may proceed with a regioselectivity of 90:10 or greater. The resulting carbonylated cyclic products may be converted to ketone aldol products that retain the stereochemistry and enantiomeric ratio of the carbonyl ated cyclic products.
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Paragraph 0146; 0151
(2020/06/05)
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- Method for synthesizing isovaleraldehyde
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The invention provides a synthetic method of 3-methylcrotonaldehyde. The method comprises the following steps that epoxy isobutane is subjected to a hydroformylation reaction, hydroxy isovaleraldehydeis obtained, hydroxy isovaleraldehyde is subjected to an intramolecular dehydration reaction, and 3-methylcrotonaldehyde is obtained. The synthetic method of 3-methylcrotonaldehyde does not need harsh reaction conditions.
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Paragraph 0033; 0035; 0038; 0040; 0043; 0045
(2020/12/05)
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- Rare earth metal compound, preparation method, composition, and method for catalyzing epoxidation of olefin
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The invention relates to a rare earth metal compound and application thereof in catalyzing epoxidation of olefin. The rare earth metal compound disclosed by the invention has a structure as shown in aformula E. The invention also relates to a preparation method of the rare earth metal compound and a composition containing the rare earth metal compound. The method is characterized in that a rare earth metal compound is added into the reaction, so that the dosage of a molybdenum catalyst can be reduced. Olefin and organic peroxide react under the action of a catalyst to generate epoxide, the organic peroxide is converted into corresponding alcohol, and the conversion rate of the organic peroxide is larger than 99%. After the reaction is finished, the rare earth metal compound can be separated and recycled. The method has the advantages of simple process, high catalytic system activity, effective reduction of the use amount of the catalyst while guaranteeing the catalytic efficiency, andcost saving.
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Paragraph 0078-0079
(2020/07/24)
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- PROCESS FOR PREPARING 3-HYDROXY-3-METHYLBUTYRATE (HMB) AND SALTS THEREOF
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The present invention pertains to a process for preparing 3-hydroxy-3-methylbutyrate (HMB) or a salt thereof, the method comprising (a) reacting isobutylene oxide with cyanide in order to obtain 3- hydroxy-3-methylbutyronitrile, and (b) hydrolyzing the 3-hydroxy-3-methylbutyronitrile obtained in step (a) in order to obtain HMB, wherein hydrolysis step (b) is performed using either at least one nitrilase enzyme or, alternatively, using a combination of enzymes, said combination comprising at least one nitrile hydratase and at least one amidase.
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Page/Page column 8
(2020/10/31)
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- Diastereoselective Desymmetrization of p-Quinamines through Regioselective Ring Opening of Epoxides and Aziridines
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A highly diastereoselective desymmetrization of p-quinamines via regioselective ring opening of epoxides and aziridines under mild conditions has been developed. A chairlike six-membered transition state with minimized 1,3-diaxial interactions explains the relative stereoselectivity of the cyclization reaction. This transition-metal free [3 + 3] annulation reaction provides rapid access to fused bicyclic morpholines and piperazines with a tetrasubstituted carbon center in high yields. In addition, it also allows the synthesis of enantioenriched products by using easily accessible chiral nonracemic epoxides and aziridines.
- Jadhav, Sandip B.,Chegondi, Rambabu
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supporting information
p. 10115 - 10119
(2019/12/24)
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- Mechanistic insights into light-driven graphene-induced peroxide decomposition: Radical generation and disproportionation
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Interaction between adsorbed t-butyl peroxybenzoate and photoexcited graphene rendered trapped phenyl and t-butoxy radicals. Post-irradiation thermal desorption showed benzene, t-butanol, and isobutylene oxide as the end products. The required hydrogen at
- Chu, Ya-Lan,Chen, Yen-An,Li, Wei-Chin,Chu, Jean-Ho,Chen, Chun-Hu,Chiang, Chao-Ming
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supporting information
p. 9291 - 9294
(2016/07/25)
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- Convenient synthesis of 1,3-dithiolane-2-thiones: Cyclic trithiocarbonates as conformational locks
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A series of novel 1,3-dithiolane-2-thiones, or cyclic trithiocarbonates, has been prepared by a new simple procedure: a treatment of the corresponding epoxides with the commercially available potassium ethyl xanthogenate, KSC(S)OEt. The stereochemistry of the products was determined by 1H NMR and in some cases by single-crystal X-ray data. Cyclohexane-based 1,3- dithiolane-2-thiones revealed a trans-fusion of the carbo- and hetero-cycles. The products obtained from the mono-substituted cyclohexene oxides demonstrated an axial position of the substituents. Thus the epoxide transformation into trithiocarbonate can be used as a method for locking cyclic compounds in unstable conformations.ARKAT-USA, Inc.
- Dotsenko, Irina A.,Zhao, Qinliang,Franz, Andreas H.,Batoon, Patrick,Samoshina, Nataliya M.,Samoshin, Vyacheslav V.
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- Biocatalytic and Structural Properties of a Highly Engineered Halohydrin Dehalogenase
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Two highly engineered halohydrin dehalogenase variants were characterized in terms of their performance in dehalogenation and epoxide cyanolysis reactions. Both enzyme variants outperformed the wild-type enzyme in the cyanolysis of ethyl (S)-3,4-epoxybutyrate, a conversion yielding ethyl (R)-4-cyano-3-hydroxybutyrate, an important chiral building block for statin synthesis. One of the enzyme variants, HheC2360, displayed catalytic rates for this cyanolysis reaction enhanced up to tenfold. Furthermore, the enantioselectivity of this variant was the opposite of that of the wild-type enzyme, both for dehalogenation and for cyanolysis reactions. The 37-fold mutant HheC2360 showed an increase in thermal stability of 8°C relative to the wild-type enzyme. Crystal structures of this enzyme were elucidated with chloride and ethyl (S)-3,4-epoxybutyrate or with ethyl (R)-4-cyano-3-hydroxybutyrate bound in the active site. The observed increase in temperature stability was explained in terms of a substantial increase in buried surface area relative to the wild-type HheC, together with enhanced interfacial interactions between the subunits that form the tetramer. The structures also revealed that the substrate binding pocket was modified both by substitutions and by backbone movements in loops surrounding the active site. The observed changes in the mutant structures are partly governed by coupled mutations, some of which are necessary to remove steric clashes or to allow backbone movements to occur. The importance of interactions between substitutions suggests that efficient directed evolution strategies should allow for compensating and synergistic mutations during library design.
- Schallmey, Marcus,Floor, Robert J.,Hauer, Bernhard,Breuer, Michael,Jekel, Peter A.,Wijma, Hein J.,Dijkstra, Bauke W.,Janssen, Dick B.
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p. 870 - 881
(2013/07/25)
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- VARIATIONS ON PRINS-LIKE CHEMISTRY TO PRODUCE 2,5-DIMETHYLHEXADIENE FROM ISOBUTANOL
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The method of the present invention provides a high yield pathway to 2,5-dimethylhexadiene from renewable isobutanol, which enables economic production of renewable p-xylene (and subsequently, terephthalic acid, a key monomer in the production of PET) from isobutanol. In addition, the present invention provides methods for producing 2,5-dimethylhexadiene from a variety of feed stocks that can act as “equivalents” of isobutylene and/or isobutyraldehyde including isobutanol, isobutylene oxide, and isobutyl ethers and acetals. Catalysts employed in the present methods that produce 2,5-dimethylhexadiene can also catalyze alcohol dehydration, alcohol oxidation, epoxide rearrangement, and ether and acetal cleavage.
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Page/Page column 7
(2012/11/07)
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- Condensed oxaziridine-mediated [3+2] cycloaddition: Synthesis of polyhetero-bicyclo compounds
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Polyhetero-bicyclo compounds were synthesized by a regioselective [3+2]-cycloaddition reaction between stable condensed oxaziridines and alkenes, alkynes, and nitriles. These molecules showed considerable antimicrobial activity against several gram-positive bacteria.
- Videtta, Valeria,Perrone, Serena,Rosato, Francesca,Alifano, Pietro,Tredici, Salvatore M.,Troisi, Luigino
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scheme or table
p. 2781 - 2783
(2010/12/25)
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- Reaction of zirconium alkoxides with tert-butyl hydroperoxide. Oxidative ability of the Zr(OBu-t)4-t-BuOOH system
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Oxidation of the isopropoxy group in the Zr(i-PrO)4·i- PrOH complex involves both direct reaction with tert-butyl hydroperoxide and intermediate formation of zirconium peroxy compound. Zirconium tetra-tert-butoxide reacts with tert-bytyl hydroperoxide to form metal-containing peroxide and trioxide. Decomposition of the latter leads to oxygen evolution and is accompanied by radical formation. The alkoxyl and peroxyl radicals formed were identified by ESR spectroscopy. The nature of the oxidant (oxygen, zirconium-containing peroxide and-trioxide) in the Zr(OBu-t)4-t-BuOOH system is determined by the structure of the substrate molecule. Pleiades Publishing, Inc., 2006.
- Gulenova,Stepovik,Cherkasov
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p. 980 - 988
(2008/02/03)
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- Neuroprotection and cardioprotection afforded by chelators with high affinity and specificity for cations of first transition series elements
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Compounds that demonstrate chelation affinity and selectivity for first transition series elements are administered to patients suffering from such conditions as ischemia, prolonged seizures and trauma to provide neuroprotection, cardioprotection, or both. These compounds when administered form complexes with chelatable iron and copper cations and thereby mitigate the ability of these cations to catalyze Haber-Weiss reactions that form toxic hydroxy free radicals that cause tissue injury. These compounds also form complexes with chelatable zinc cations thereby inhibiting the cytotoxicity associated with excess chelatable zinc.
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- Rearrangement pathways of 2-hydroxy-2-methylpropylidene: An experimental and computational study
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Photolysis of exo-2-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)propan-2-ol in benzene-d6 afforded phenanthrene and the β-hydroxycarbene intermediate 2-hydroxy-2-methylpropylidene. The carbene showed an overwhelming preference for 1,2-methyl migration as evident from the formation of 2-butanone as the major product via the enol 2-hydroxy-2-butene. Also produced, albeit in smaller amounts, were 1-methylcyclopropanol and 2,2-dimethyloxirane from intramolecular insertion into the C-H and O-H bonds, respectively. These results stand in sharp contrast to the intramolecular reactions of simple alkylcarbenes which usually prefer insertion into C-H bonds over 1,2-alkyl migrations. Calculations at the B3LYP/6-311+G**//B3LYP/6-31G* level of theory give a lower activation barrier for 1,2-methyl migration leading to the eventual formation of 2-butanone than for the other two pathways. The lower activation energy for methyl migration, relative to C-H and O-H insertions, strongly supports the observed experimental product distribution of the carbene. The parent carbene exists in three distinct conformations, each with stabilizing interactions between the adjacent bonds and the empty p orbital and the filled sp2 orbital of the carbene center. The most stable conformer is perfectly poised for a 1,2-methyl migration as the C-CH3 group is involved in a hyperconjugative interaction with the empty p orbital and the O-H bond is simultaneously interacting with the sp2 lone pair of the carbene.
- Farlow, Robin A.,Thamattoor, Dasan M.,Sunoj,Hadad, Christopher M.
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p. 3257 - 3265
(2007/10/03)
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- Compounds with chelation affinity and selectivity for first transition elements and their use in cosmetics and personal care products, inhibition of metalloenzymes, and inhibition of reperfusion injury
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This invention involves the use of a class of compounds with chelation affinity and selectivity for first transition series elements. Application or administration of the free or conjugated compound, or physiological salts of the free or conjugated compound, results in decrease of the bioavailability and/or chemical action of first transition series elements. These characteristics make such compounds useful in cosmetics and personal care products to decrease odor arising from microbial growth on body surfaces and in body cavities, decrease microbial growth on teeth, plaque, and gums that cause tooth decay and gum disease, inhibition of oxidative damage to the skin, inhibition of enzymatic action of metalloenzymes dependent on first transition series elements, and inhibition of reperfusion injury.
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- Synthesis of 1,1,6,6-tetramethylphosphajulolidine
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The synthesis of fused tricyclic dialkyl(phenyl)phosphine was studied to verify the ligand influence upon the catalytic alkoxycarbonylation of propyne. The quantum mechanical calculations were performed to determine the ligand-derived influences upon catalytic activity. The results showed that the ellipticity of the bond was maximized by tethering the alkyl substituents to the ortho carbons of the aromatic ring.
- Edwards, Peter G.,Paisey, Stephen J.,Tooze, Robert P.
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p. 3122 - 3128
(2007/10/03)
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- Hydrolysis of genotoxic methyl-substituted oxiranes: Experimental kinetic and semiempirical studies
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The kinetics of acid-catalyzed hydrolysis of seven methylated aliphatic epoxides - R1R2C(O)CR3R4 (A: R1=R2=R3=R4=H; B: R1=R2=R3=H, R4=Me; C: R1=R2=H, R3=R4=Me; D: R1=R3=H, R2=R4=Me(trans); E: R1=R3=H, R2=R4=Me(cis); F: R1=R3=R4=Me, R2=H; G: R1=R2=R3=R4=Me) - has been studied at 36 ± 1.5°C. Compounds with two methyl groups at the same carbon atom of the oxirane ring exhibit highest rate constants (k(eff) in reciprocal molar concentration per second: 11.0 ± 1.3 for C, 10.7 ± 2.1 for F, and 8.7 ± 0.7 for G as opposed to 0.124 ± 0.003 for B, 0.305 ± 0.003 for D, and 0.635 ± 0.036 for E). Ethylene oxide (A) displays the lowest rate of hydrolysis (0.027 M-1 s-1). The results are consistent with literature data available for compounds A, B, and C. To model the reactivities we have employed quantum chemical calculations (MNDO, AM1, PM3, and MINDO/3) of the main reaction species. There is a correlation of the logarithm k(eff) with the total energy of epoxide ring opening. The best correlation coefficients (r) were obtained using the AM1 and MNDO methods (0.966 and 0.957, respectively). However, unlike MNDO, AM1 predicts approximately zero energy barriers for the oxirane ring opening of compounds B, C, E and G, which is not consistent with published kinetic data. Thus, the MNDO method provides a preferential means of modeling the acidic hydrolysis of the series of methylated oxiranes. The general ranking of mutagenicity in vitro, A > B > C, is in line with the concept that this sequence also gradually leaves the expoxide reactivity optimal for genotoxicity toward reactivities leading to higher biological detoxifications.
- Kirkovsky, Leonid I.,Lermontov, Sergei A.,Zavorin, Sergei I.,Sukhozhenko, Ivan I.,Zavelsky, Vladimir I.,Thier, Ricarda,Bolt, Hermann M.
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p. 2141 - 2147
(2007/10/03)
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- Oxirane Formation in the Reaction of NO3 Radicals with Alkenes
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Chemical Kinetics / Mass Spectrometry / Radicals.Mass spectra of products formed in the reaction between NO3 and cis-2-butene, isobutene, 2-methyl-2-butene and 2,3-dimethyl-2-butene at 298 K and p = 3-10 mbar were obtained, using a fast flow system with molecular beam sampling.The spectra indicate formation of an oxirane in each reaction.Within experimental error the oxirane yields in the reaction of cis-2 butene and of 2,3-dimethyl-2-butene were identical (90+/-10)percent.The rate of oxirane formation was found to obey the rate equation for the reaction: NO3 + alkene oxirane + NO2. (1) Good agreement was obtained for the rate constants of reaction (1) determined from the rate of oxirane formation and those determined in earlier works from the consumption of reactants.
- Wille, U.,Rahman, M. M.,Schindler, R. N.
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p. 833 - 835
(2007/10/02)
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- Thermal Decomposition of Nitrate Esters
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Rates of thermal decomposition and solvent rate effects have been measured for a series of nitrate esters.The alkoxy radicals formed by homolysis together with some of their further degradation products have been stabilized by hydrogen donation.Internal and external return of nitrogen dioxide have been demonstrated by solvent cage effects and isotope exchange.Radical-stabilizing substituents favor β-scission.Dinitrates in a 1,5 relationship behave as isolated mononitrates.Dinitrates in a 1,3 or 1,4 relationship exhibit intramolecular reactions.Tertiary nitrate esters in diethyl ether undergo elimination rather than homolysis.
- Hiskey , Michael A.,Brower, Kay R.,Oxley, Jimmie C.
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p. 3955 - 3960
(2007/10/02)
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- Simultaneous epoxide and carboxylic acid manufacture by co-oxidation in the presence of a cobalt catalyst
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A process for the preparation of isobutylene oxide and isobutyric acid from isobutylene and isobutyraldehyde, respectively, by a co-oxidation process conducted in the presence of oxygen and a cobalt salt catalyst at a temperature of about 20° to about 180° C. is disclosed.
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- Photochemical decomposition of t-butylperoxyacetals
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The decomposition of peroxides in the solid phase by UV radiation was investigated.It was shown that the decomposition of peroxides results in the formation of unstable alkoxy radicals, which decompose at C-C or C-H bonds, giving rise to alkyl radicals.An appreciable similarity between the final products of the decomposition of solid peroxides by UV radiation and the products of the thermolysis of the same peroxides was established, which led to the hypothesis that there is some similarity between the mechanism of the decomposition of the peroxides.
- Turovskii, A. A.,Luk'yanenko, L. V.,Kucher, R. V.,Petrenko, V. V.
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p. 1157 - 1160
(2007/10/02)
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- Radiolysis of Tertiary Butyl Hydroperoxide in Aqueous Solution. Reductive Cleavage by the Solvated Electron, the Hydrogen Atom, and, in Particular, the Superoxide Radical Anion
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The reactions of the solvated electron, the H atom, the OH radical and the superoxide radical anion with t-butylhydroperoxide (t-BuOOH) have been studied in aqueous solutions using γ-radiolysis and pulse radiolysis to generate these radicals.The solvated electron reacts rapidly with t-BuOOH (k=5*1E9 dm3 mol-1 s-1) yielding t-BuO* and *OH in a ratio of 4:1.The yield of t-BuO* has been determined by measuring its fragmentation product, acetone.The H atom reacts more slowly with t-BuOOH (k=5*1E7 dm3 mol-1 s-1).There is very little H-abstraction from the methyl and the hydroxyperoxyl function with a branching ratio t-BuO*/*OH of about unity.The OH radical reacts with t-BuOOH considerably more slowly (k=9*1E7 dm3 mol-1 s-1) than with t-butanol (k=5*1E8 dm3 mol-1 s-1) with an approximate preference of 8:1 of abstracting a methyl hydrogen over a hydroperoxyl hydrogen atom.The caron-centered radical undergoes γ-cleavage (k ca. 1E2 s-1) thereby reforming an OH radical.The resulting chain reaction is rather shor (maximum yield G (2-methyl-1,2-epoxypropane), 26*1E-7 mol J-1 at low dose rate) due to H-abstraction at the hydroperoxyl function of t-BuOOH by the OH radical.The superoxide radical anion also reacts with t-BuOOH by cleaving the hydroperoxyl function.Its reactivity is, however, rather low (k=5 dm3 mol-1 s-1).
- Phulkar, Shailesh,Rao, Balijepalli Sethu Madhava,Schuchmann, Heinz-Peter,Sonntag, Clemens von
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p. 1425 - 1432
(2007/10/02)
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- Oxidation of tert-butyl alcohol to isobutylene oxide on a Ag(110) surface: The role of unactivated C-H bonds in product selectivity
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Tert-Butyl alcohol reacts with oxygen-covered Ag(110) surfaces below 200 K yielding t-BuO(a) and adsorbed water and hydroxyl groups. Temperature-programmed reaction spectroscopy demonstrates that t-BuO(a) reacts at 440 and 510 K by processes that involve rate-limiting C-H bond cleavage yielding isobutylene oxide, isobutylene, tert-butyl alcohol, H2O, and CO2. The reaction path at 440 K predominates when the initial coverage of O(a) is high; that at 510 K predominates when the coverage of O(a) is low. A third process occurs at 590 K, producing acetone. It is concluded from this work that the unactivated methyl C-H bonds in t-BuO(a) are significantly more stable toward cleavage by this surface than are the activated C-H bonds in MeO(a) or EtO(a).
- Brainard,Madix
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p. 3826 - 3835
(2007/10/02)
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- Enolic Ortho Esters. I. Preparation and Birch Reduction of Some Coumarinoid Ortho Esters
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Phenolic ortho esters such as 4',4'-dimethylspirodioxolan> (7b) and 4',4'-dimethyl-3,4-dihydrospirodioxolan> (9c) were prepared in low yields by reaction of 2H-1-benzopyran-2-one (5) or 3,4-dihydro-2H-1-benzopyran-2-one (8a) with 2,2-dimethyloxiran in carbon tetrachloride in the presence of boron trifluoride etherate. 3,4-Dihydrospirodioxolan> (9a) and the corresponding 7-methoxy compound (9e) were obtained in high yield by reaction of (8a) or its 7-methoxy analogue (8b) with 1,2-bis(trimethylsilyloxy)ethane (10) in the presence of trimethylsilyl trifluoromethanesulfonate.Birch reduction of phenolic ortho esters such as (9c) and (9e) afforded the enolic ortho esters 4',4'-dimethyl-3,4,5,8-tetrahydrospirodioxolan> (11a) and 7-methoxy-3,4,5,8-tetrahydrospirodioxolan> (11c) in high yields.Birch reduction of 4',4',5',5'-tetramethylspirodioxolan> (7c) gave a 1:3 mixture of 4',4',5',5',-tetramethyl-3,4-dihydrospirodioxolan> (9d) and the corresponding 3,4,5,8-tetrahydro compound (11b).Acid hydrolysis of the enolic ortho ester (11a) gave 67percent of 2-hydroxy-2-methylpropyl 3-(2-oxocyclohex-3-enyl)propanoate (20).
- Collins, David J.,Downes, Leanne M.,Jhingran, Akhil G.,Rutschmann, Suzanne B.,Sharp, Gerard J.
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p. 1235 - 1248
(2007/10/02)
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- USING THE COMPARISON OF STERIC VERSUS ELECTRONIC EFFECTS TO INFER MECHANISTIC INFORMATION IN STEPWISE ELECTROPHILIC ADDITION REACTIONS INVOLVING THREE-MEMBERED CYCLIC INTERMEDIATES
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Correlations of IP's versus relative reactivities or formation constants of reactions of alkenes with ArSCl, MeCO3H, Ag(1+), or HgCl2 reveal that complexation reactions show steric dependence, that additions with the first step rate-determining are sterically independent, and that those with the second step rate-determining are sterically dependent.
- Nelson, Donna J.,Soundararajan, Raman
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p. 6207 - 6210
(2007/10/02)
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- NOVEL OXIRANE FORMATION VIA 1-METALLA-2-OXACYCLOBUTANES
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1-Metalla-2-oxacyclobutane complex, which was formed by intramolecular γ-hydrogen elimination of alkoxy(alkyl)metal complex of Ni or Pd, yields mainly oxirane, while its Ti complex affords olefins resulting from C-O bond cleavage.
- Miyashita, Akira,Ishida, Jun-ya,Nohira, Hiroyuki
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p. 2127 - 2130
(2007/10/02)
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- RATE CONSTANTS FOR THE FORMATION OF OXIRANES BY γ-SCISSION IN SECONDARY β-t-BUTYLPEROXYALKYL RADICALS
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Rate constants for the title reactions have been determined from the ratios of oxirane to peroxide obtained in the reductons of β-bromoalkyl t-butyl peroxides with tributyltin hydride.At ca. 298 K the rate constants are 0.32, 1.12, 1.96, 2.0 and 6.2E6 s-1 for β-t-butylperoxy derivatives of trinorbornan-2-yl (exo) cyclohexyl, 1-methylpropyl , cyclopentyl and 1-ethylbutyl, respectively.The results are discussed in terms of steric and electronic effects in the transition state leading to ring closure of the radicals.
- Bloodworth A. J.,Courtneidge, J. L.,Davies, Alwyn G.
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p. 523 - 528
(2007/10/02)
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- A new approach to the air oxidation of alkenes employing metal nitro complexes as catalysts
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Alkenes are stoichiometrically and, in the presence of air, catalytically oxidized by cis-bis(acetonitrile)chloronitropalladium(II) (1). Oxidation of monosubstituted terminal alkenes and trans-cyclooctene yields the corresponding ketone, oxidation of cyclopentene and cyclohexene the corresponding allyl alcohol, and oxidation of bicyclic alkenes the corresponding epoxide, each with good selectivity for the respective product. Other alkenes give varying mixtures of the above products together with, in some cases, the α,β-unsaturated ketone. Vinyl ethers yield the corresponding ester while (trimethylsilyl)ethylene yields (trimethylsilyl)acetaldehyde. The selectivities are rationalized on the basis of ease of β-hydrogen elimination in observed intermediate heterometallacyclopentane complexes 3 formed by nucleophilic attack of the nitro oxygen atom on the coordinated alkene in alkene nitro complexes 2. The general role of metallacycles in metal-mediated alkene oxidations and the advantages and disadvantages of intra- vs. intermolecular metal nitro catalyzed alkene oxidations are discussed.
- Andrews, Mark A.,Chang, Tony C.-T.,Cheng, Chi-Wen F.,Kelly, Kevin P.
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p. 1777 - 1785
(2008/10/08)
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- EPOXIDATION OF ISOBUTENE WITH ORGANIC HYDROPEROXIDES, AND CERTAIN SYNTHESES ON THIS BASIS.
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The authors describe the preparation of isobutene oxide in presence of these hydroperoxides, and certain syntheses on this basis. It is shown that the epoxidation of isobutene by ethylbenzene and isopropylbenzene hydroperoxides is a worthwhile process. Conditions under which the oxide yield calculated on the hydroperoxide converted exceeds 80% were found. Reactions leading to production of isobutyl and methallyl alcohols and isobutyraldehyde from isobutene oxide obtained by this process were studied. The conditions for obtaining high yields of these products (over 90%) are specified.
- Farberov,Bondarenko,Tsilyurik,Srednev,Shutova
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p. 1915 - 1919
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 15. Reactions of t-Butylperoxyl Radicals with Alkenes
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The photo-oxidation of mixtures of trans-2,2'-azoisobutane and some aliphatic alkenes has been studied between 313 and 393 K.Rate constants for the reaction between t-butylperoxyl radicals with ethene, 2-methylpropene, 2-methylbut-1-ene, 2-methylbut-2-ene, and 2,3-dimethylbut-2-ene have been determined at 393 K.Arrhenius parameters for the reaction (22) have been determined for 2-methylbut-2-ene and 2,3-dimethylbut-2-ene.They are log (A22/dm3mol-1s-1) of 8.16+/-0.38 and 8.58+/-0.61, and E22/kJ mol-1 of 56.6+/-2.4 and 48.7+/-4.1, respectively.The data obtained in this work are compared with that obtained for the series hydroperoxyl, and isopropylperoxyl radicals, and with rate data obtained for the addition reaction between alkenes and peracetyl radicals.
- Morgan, Morag E.,Osborne, David A.,Waddington, David J.
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p. 1869 - 1873
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 12. The Reactions of Isopropylperoxyl Radicals and Alkenes
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The co-oxidation of trans-2,2'-azopropane and some aliphatic alkenes has been studied between 303 and 408 K.From the yields of molecular products, rate data have been obtained for the reaction of isopropylperoxyl radicals and the following alkenes, 2-methylbut-2-ene, 2-methylbut-1-ene, 2-methyl-propene, propene, and 3-fluoropropene (reaction (22)).It is shown that the isopropylperoxyl radical is less reactive than methylperoxyl but still shows distinct electrophilic character in these reactions.
- Sway, Mohammed I.,Waddington, David J.
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p. 139 - 144
(2007/10/02)
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- The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
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The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
- Martinez, Richard I.,Herron, John T.,Huie, Robert E.
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p. 3807 - 3820
(2007/10/02)
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- FEATURES OF THE REACTION OF 1,1-DIPHENYL-2-PICRYLHYDRAZINE WITH PEROXIDES CONTAINING A tert-BUTYL GROUP
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The reaction of 1,1-diphenyl-2-picrylhydrazine with unsymmetrical peroxides containing a tert-butyl group gives rise to decomposition of the latter at the O-O bond.The reaction occurs with the formation of 1,1-diphenyl-2-picrylhydrazyl, which can in turn enter into reaction with the peroxides.The kinetic parameters of the accumulation of 1,1-diphenyl-2-picrylhydrazyl in various solvents were obtained.A mechanism for the reaction is proposed.
- Kucher, R. V.,Luk'yanenko, L. V.,Turovskii, A. A.
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p. 734 - 739
(2007/10/02)
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2-Halogenoalkoxytributyltin compounds have been prepared from tributylethoxytin and 1,2-halohydrins. The thermal degradation and its mechanism are investigated. These reactions offer a convenient way to prepare epoxides.
- Delmond, Bernard,Pommier, Jean-Claude,Valade, Jacques
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