10473-13-9Relevant academic research and scientific papers
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.
The acidity and catalytic activity of supported acidic cesium dodecatungstophosphates studied by MAS NMR, FTIR, and catalytic test reactions
Molnar,Beregszaszi,Fudala,Lentz,Nagy,Konya,Kiricsi
, p. 379 - 386 (2001)
Acidic cesium salts of dodecatungstophosphoric acid (H3PW) supported on silica and MCM-41 were characterized by multinuclear MAS NMR, FTIR, and catalytic test reactions. 31P-NMR data indicate that the supported samples contain salts of various stoichiometries (Cs3PW and Cs2HPW) and even H3PO4. According to 29Si-NMR data, deposition of the Cs salt does not change the relative amount of various SiOH groups in the case of the silica support. In contrast, when the support is MCM-41, the relative amount of the SiOH groups increases significantly, indicating the breaking of the siloxane bonds resulting from their interaction with H3PW. The 133Cs MAS-NMR spectra also suggest that the CsPW salt interacts more strongly with the MCM-41 support than with SiO2. The results of catalytic studies show that cesium salts of dodecatungstophosphoric acid with low Cs content supported on silica or MCM-41 (Cs1.7H1.3[PW12O40]-on-SiO 2 and Cs1.8H1.2[PW12O40]-on-MCM41) are active, selective, and recyclable catalysts in Friedel-Crafts alkylations (isopropylation, transalkylation), the aromatic ortho-Claisen rearrangement, and the dehydration of pinacol. The specific activity of these catalyst preparations are comparable with that of neat Cs2.6H0.4[PW12O40]. This indicates that the active species are in a well-dispersed form.
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.
Transient formation of hydrogen tetraoxide from hydrogen peroxide with bis(trifluoroacetoxyiodo)benzene: A chemical generator of singlet oxygen for organic synthesis
Catir, Mustafa,Kilic, Hamdullah
, p. 1180 - 1182 (2003)
Decomposition of hydrogen tetraoxide, produced by the reaction of hydrogen peroxide with bis(trifluoroacetoxyiodo) benzene, generates singlet molecular oxygen. Oxidation of typical organic substrates in an organic solvent through [4+2] cycloaddition and ene reactions have been camed out on a preparative scale.
Singlet oxygen generation from poly[4-diacetoxyiodo]styrene and hydrogen peroxide
?atir, Mustafa
, p. 467 - 475 (2017)
Treatment of hydrogen peroxide with a polymer-supported hypervalent iodine compound, poly[4-diacetoxyiodo] styrene (PDAIS), generates singlet molecular oxygen (1O2). Singlet oxygen generation was proved by trapping with typical organic compounds such as conjugated dienes, aromatic dienes, and electron-rich alkene. When compared to monomer analogue, the use of PDAIS in peroxidation of substrates gave slightly better yields (45%–96%). Regeneration and reuse of PDAIS showed similar activity. The mechanism underlying generation of singlet oxygen and reaction scope was examined.
CATALYZED OXIDATION OF ANTHRACENE WITH OXYGEN AND tert-BUTYLHYDROPEROXIDE
Mueller, Paul,Bobillier, Christiane
, p. 5157 - 5160 (1981)
Oxidation of anthracene to anthraquinone by oxygen/RhCl(PPh3)3 proceeds via solvent derived hydroperoxydes. tert-Butylhydroperoxide/RhCl(PPh3)3 effects the same transformation in up to 96percent yield.Possible mechanisms for the TBHP-catalyzed reaction are discussed.
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.
Lithium 2,2,6,6-Tetramethylpiperidide-Mediated α- and β-Lithiations of Epoxides: Solvent-Dependent Mechanisms
Wiedemann, Sean H.,Ramirez, Antonio,Collum, David B.
, p. 15893 - 15901 (2003)
Lithium 2,2,6,6-tetramethylpiperidide (LiTMP)-mediated α- and β-lithiations of epoxides are described. LiTMP displays a markedly higher reactivity than does lithium diisopropylamide, consistent with literature reports. Detailed rate studies of LiTMP/THF and LiTMP/Me2NEt mixtures reveal similar rates but significant mechanistic differences. LiTMP-mediated α-lithiation of cis-cyclooctene oxide with subsequent oxacarbenoid formation and transannular C-H insertion proceeds via monosolvated dimers in both THF and Me2NEt. LiTMP-mediated β-lithiation of 2,3-dimethyl-2-butene oxide affords the corresponding allylic alcohol via a monosolvated monomer in THF and a monosolvated dimer in Me2NEt. We discuss how the solvent-dependent aggregation of LiTMP markedly influences the rate profile. The reaction transition structures are examined with density functional computations.
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.
