10473-13-9Relevant articles and documents
Reactions of Microwave-Generated O(3P) Atoms with Unsaturated Hydrocarbons
Tanner,Kandanarachchi,Das,Brausen,Vo,Camaioni,Franz
, p. 4587 - 4593 (1998)
The reactions of neat olefins or solutions of olefins in acetone at low temperature with oxygen atoms were examined. O(3P) atoms were produced by microwave irradiation of He/O2 mixtures, followed by contact of the plasma with the fluid at low pressure and temperature. Addition of oxygen atoms to olefins results in skeletal rearrangements involving hydrogen and alkyl migration reactions and ring rearrangements of the intermediate oxygen adducts in competition with epoxide formation. While epoxide formation predominates for simple olefins such as 1- and 4-octene with minor yields of rearrangement products, for highly substituted or strained olefins, such as norbornadiene, skeletal rearrangement dominates following oxygen atom addition. When oxidation of norbornadiene is carried out in the presence of a radical inhibitor to suppress secondary oxidation leading to benzene, the novel ring-rearrangement product, bicyclo[3.2,31.0]hex- 3-ene-endo-6-carboxaldehyde, is produced from norbornadiene in significant yields.
Mechanism of ene reactions of singlet oxygen. A two-step no-intermediate mechanism
Singleton, Daniel A.,Hang, Chao,Szymanski, Michael J.,Meyer, Matthew P.,Leach, Andrew G.,Kuwata, Keith T.,Chen, Jenny S.,Greer, Alexander,Foote, Christopher S.,Houk
, p. 1319 - 1328 (2003)
The mechanism of the ene reaction of singlet (1Δg) oxygen with simple alkenes is investigated by a combination of experimental isotope effects and several levels of theoretical calculations. For the reaction of 2,4-dimethyl-3-isopropyl-2-pentene, the olefinic carbons exhibit small and nearly equal 13C isotope effects of 1.005-1.007, while the reacting methyl groups exhibit 13C isotope effects near unity. In a novel experiment, the 13C composition of the product is analyzed to determine the intramolecular 13C isotope effects in the ene reaction of tetramethylethylene. The new 13C and literature 2H isotope effects are then used to evaluate the accuracy of theoretical calculations. RHF, CASSCF(10e, 8o), and restricted and unrestricted B3LYP calculations are each applied to the ene reaction with tetramethylethylene. Each predicts a different mechanism, but none leads to reasonable predictions of the experimental isotope effects. It is concluded that none of these calculations accurately describe the reaction. A more successful approach was to use high-level, up to CCSD(T), single-point energy calculations on a grid of B3LYP geometries. The resulting energy surface is supported by its accurate predictions of the intermolecular 13C and 2H isotope effects and a very good prediction of the reaction barrier. This CCSD(T)//B3LYP surface features two adjacent transition states without an intervening intermediate. This is the first experimentally supported example of such a surface and the first example of a valley-ridge inflection with significant chemical consequences.
Effect of various acids at different concentrations on the pinacol rearrangement
De Lezaeta, Monica,Sattar, Wajiha,Svoronos, Paris,Karimi, Sasan,Subramaniam, Gopal
, p. 9307 - 9309 (2002)
The formation of side products in the pinacol-pinacolone rearrangement was studied as a function of concentration and strength of various aqueous acids using 1H NMR spectroscopy. In all cases, pinacolone was the principal product and in most cases, its relative yield decreased with respect to 2,3-dimethyl-1,3-butadiene, when the acid concentration was lowered or the corresponding conjugate base was added.
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Murata,S. et al.
, p. 2738 - 2739 (1979)
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Hatch,Journeay
, p. 3712 (1953)
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Lyons,Turner
, p. 2881 (1972)
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1,2-Bond Shift Isomerization of Oxiranes on Copper-Graphimet
Molnar, Arpad,Mastalir, Agnes,Bartok, Mihaly
, p. 124 - 126 (1989)
2,2,3,3-Tetramethyloxirane (1) undergoes isomerization on copper intercatated graphite (graphimet) to t-butyl methyl ketone (4) via a 1,2-methyl migration and to 2,3-dimethylbut-3-en-2-ol (5) via a 1,3-hydrogen shift, as well as deoxygenation and dehydration products.
Total synthesis and olfactory evaluation of 5β,10-dimethyl-des-A-18-/ nor-androstan-13β-ol: A potential human pheromone?
Kraft, Philip,Popaj, Kasim
, p. 4995 - 5002 (2004)
5β,10-Dimethyl-des-A-18-nor-androstan-13β-ol (Limdrostanol, 11) was suspected to be the underlying parent steroid responsible for the interesting urinous-animalic, woody olfactory properties of the commercial odorant Timberol (6-9), and the captives Norlimbanol (7) and Limbanol (10), and so could constitute a potential human pheromone. We report the first synthesis of 11, starting with treatment of the bis-Grignard reagent of 1,4-dibromobutane (15) with γ-butyrolactone (16), Appel-Lee bromination of the resulting diol 17 with elimination of the tertiary hydroxy group, and transformation of the obtained bromo alkene 18 into the corresponding triphenylphosphonium salt 13. This was subjected to a Schlosser-Wittig reaction with the γ,δ-unsaturated aldehyde 14, prepared in turn by Grignard treatment of ethyl methacrylate (19) and subsequent Saucy-Marbet reaction of the resulting dimethyl carbinol 20 with ethyl vinyl ether (21). Cascade cyclization of the Schlosser-Wittig product 23 with methanesulfonic acid in dichloromethane at 0 °C afforded the tricyclic alkene 24, which was transformed into the target structure 11 by epoxidation with 3-chloroperbenzoic acid and subsequent reduction with lithium triethylborohydride. In addition to 11, the corresponding 14α-isomer 26 was obtained, and the olfactory properties of both are discussed. The high odor thresholds of 11 and 26, as well as the distinct differences in odor with 6-10, make it very unlikely that these des-A-18-nor-androstanols are the underlying odorous principle of 6-10, or that they function as human pheromones. An alternative synthesis of 11 by cyclization of 23 at 0 °C with 0.8 equivalents of methanesulfonic acid in formic acid as terminating nucleophile is also discussed, but gave only unsatisfactory yields. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
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Wasserman et al.
, p. 4991,4995 (1972)
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Hemi-labile ligands in organolithium chemistry: Rate studies of the LDA-mediated α- and β-metalations of epoxides
Ramirez, Antonio,Collum, David B.
, p. 11114 - 11121 (1999)
Lithium diisopropylamide (LDA)-mediated α- and β-eliminations of epoxides are described. A comparison between LDA/n-BuOMe mixtures and LDA/MeOCH2CH2NMe2 (LDA/3) mixtures reveals that the LDA dimer solvated by the "hemi-labile" amino ether 3 imparts dramatic rate accelerations, alters relative efficacies of monomer- and dimer-based metalations, and influences the partitioning between α- and β-metalation. The α-elimination of exo-norbornene oxide by LDA/n-BuOMe and LDA/3 proceeds exclusively via a dimer-based pathway with a transition structure, [(R2NLi)2(epoxide)(ligand)] ?. The β-elimination of tetramethylethylene oxide by LDA/n-BuOMe and LDA/3 proceeds exclusively via a monomer-based pathway with a transition structure, [(R2NLi)(epoxide)(ligand)]?. cis-Cyclooctene epoxide reacts with LDA/3 to give two products: (1) a bicyclooctanol derived from an α-metalation and a dimer-based transition structure, [(R2NLi)2(epoxide)(ligand)]?, and (2) 2-cycloocten-l-ol derived from both a monomer-based transition structure, [(R2NLi)(epoxide)(ligand)]?, and a dimer-based transition structure, [(R2NLi)2(epoxide)(ligand)]?. Possible geometries of the transition structures are discussed. Hemi-labile ligands that chelate lithium only at the rate-limiting transition structures maximize both the reaction rates and the mechanistic transparency.
The Region of Mechanistic Transition in Acid-Catalyzed Epoxide Ring Opening. A Mechanistic Switch Mediated by Salt in Aqueous Media
Pocker, Y.,Ronald, B. P.
, p. 5311 - 5316 (1980)
The mechanism of the acid-catalyzed ring opening of tetramethylethylene oxide has been explored through 1H NMR and UV spectrophotometric product analysis in aqueous media.In dilute aqueous media below pH 4 the hydrolysis proceeds to the extent of 99.92percent forming pinacol; no detectable amount of pinacolone is formed from a possible rearrangement pathway.With increasing amounts of NaClO4 at constant acid concentration there is a dramatic change in the products; rearrangement products appear even at 2.0 M aqueous NaClO4, and rise to the extent of 10percent at 6.0 M NaClO4.Formate buffers in these salt solutions lead to the formation of pinacol monoformate ester concurrent with pinacolone and pinacol; however, limitations in the solubility of the epoxide substrate prohibited rate measurements.The dramatic product change arising from a novel salt effect in aqueous media reveals a mechanistic pathway switch for this acid-catalyzed epoxide ring opening.The initiating step in the mechanism with or without salt is the same, the formation of the protonated epoxide as an intermediate.Nucleophile-assisted opening of the intermediate by water or formate buffer uniquely excludes products derived from skeletal rearrangement.However, high salt concentrations can provide the necessary electrostatic stabilization required for charged intermediates as well as reduce the probability of nucleophilic attack by water.The switch to a carbonium ion intermediate (a species isomeric with the protonated epoxide) is signaled by pinacolone formation.
Kinetics of the Termal Gas-phase Decomposition of 2-(1-methylethoxy)propene and of 2,3-dimethyl-2,3-epoxybutane
Flowers, Michael C.,Honeyman, Malcolm R.
, p. 1923 - 1933 (1981)
In the temperature range 554-610 K 2-(1-methylethoxy)propene undergoes a homogenous, unimolecular elimination reaction to give propene and propanone as the only products and with rate constans (kd) given by the equation kd/s-1 = 1E11.98-/+0.46 exp(-168.1-/+5.1 kJ mol-1/RT).A polar transition state for the reaction is supported.The decomposition of 2,3-dimethyl-2,3-epoxybutane has been reinvestigated over the temperature range 642-733 K. 3,3-dimethylbutan-2-one (kk), 2-3-dimethylbut-1-en-3-ol (ka), and propene+propanone (kp) are the major reaction products and are formed as the consequence of homogenous, unimolecular processes with the rate constans given by the equations kk/s-1 = 1E13.57-/+0.46 exp(-233.4-/+6.2 kJ mol-1/RT) ka/s-1 = 1E11.81-/+0.94 exp(-209.8-/+12.5 kJ mol-1/RT) kp/s-1 = 1E13.55-/+0.34 exp(-235.0-/+4.5 kJ mol-1/RT).A silanised glass surface is shown to be effective in eliminating surface reactions in the decomposition of oxirans.Data on all alkyl oxiran studies are summarised and conclusions are drawn regarding the transition states for the reactions.In contrast to previous conclusions support is given to the involvement of polar trasition states.
Rate constant for the generation of 1O2 from commonly used triplet sensitizers: A systematic study of the wavelength effect using the ene reaction of 2,3-dimethyl-2-butene
Hayakawa, Mamiko,Aoyama, Tadashi,Ouchi, Akihiko
, p. 81 - 93 (2021/01/20)
Singlet oxygen (1O2) has been widely used in organic synthesis to introduce oxygen-containing functional groups. It is usually generated from ground state oxygen via photochemical triplet sensitization using various organic dyes. To clarify the factors for increasing the efficiency of the reaction, we report a systematic determination of the rate constants observed for the generation of 1O2 from commonly used triplet sensitizers, i.e., methylene blue, rose bengal, eosin Y, tetraphenylporphyrin, and C60, using the ene reaction of 2,3-dimethyl-2-butene as a probe reaction utilizing 395 and 525 nm LEDs. A faster reaction was accomplished by the larger quantum yield for the generation of 1O2, longer irradiation wavelength (λ), higher intensity of incident light (E), and larger ελ (the product of the irradiation wavelength λ and molar extinction coefficient at (λ).
Highly selective markovnikov addition of hypervalent H-spirophosphoranes to alkynes mediated by palladium acetate: Generality and mechanism
Han, Li-Biao,Ono, Yutaka,Xu, Qing,Shimada, Shigeru
supporting information; experimental part, p. 1086 - 1099 (2010/11/05)
Palladium acetate efficiently catalyzes the addition of an H-spirophosphorane (pinacolato)2PH to alkynes to give Markovnikov addition products highlyselectively. The addition products can be easily converted to the corresponding alkenylphosphonates and phosphonicacids viasimple hydrolysis or thermal decomposition. This new reaction isa general method for the introduction of phosphorus functionality to the internal carbons of terminal alkynes, resolving the problem of the regioselectivity associated with hydrophosphorylation reactions so far reported. Mechanistic studies confirmed that (a) palladium acetate was reduced to metallic palladium by H-spirophosphorane, (b) the P-H bond of H-spirophosphorane could be activated by zero-valent platinum complexes to give the corresponding hydridoplatinum complexes, and (c) an alkenylpalladium species was identified from the reaction of palladium acetate with H- spirophosphorane and diphenylacetylene. These results support a reaction mechanism that palladium acetate was first reduced by H-spirophosphorane to give zero-valent palladium. This zero-valent palladium might insert into the P-H bond of the H-spirophosphorane to give a hydridopalladium species which then added to alkyne via the addition of H-Pd bond to form an alkenylpalladium species with the hydrogen atom added to the terminal carbon of alkynes. Reductive elimination of the alkenylpalladium affords the addition product.
