- SURFACE PHOTOCHEMISTRY: SEMICONDUCTOR PHOTOINDUCED VALENCE ISOMERIZATION OF QUADRICYCLANE TO NORBORNADIENE
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Contrary to a recent report, the valence isomerization via a radical cation, of quadricyclane to norbornadiene on the surface of illuminated CdS and ZnO is described.
- Draper, Anthony M.,Mayo, Paul de
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- Iridium-Catalyzed Asymmetric Hydroalkenylation of Norbornene Derivatives
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Transition-metal-catalyzed asymmetric hydroalkenylation of alkenes provides an atom-economical method to build molecular complexity from easily available materials. Herein we report an iridium-catalyzed asymmetric hydroalkenylation of unconjugated alkenes with acrylamides and acrylates. The catalytic hydroalkenylation of norbornene derivatives occurred to form products with allylic stereocenters with high chemo-, regio-, and stereoselectivities. DFT calculations revealed that the migratory insertion is irreversible and the enantiodetermination step.
- Sun, Xin,Bai, Xiao-Yan,Li, An-Zhen,Li, Bi-Jie
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- DIOXIRANES: DIMETHYLDIOXIRANE CATALYZED VALENCE ISOMERIZATION OF QUADRICYCLANE
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Dimethyldioxirane, 3, catalyzes the isomerization of quadricyclane to norbornadiene.Turnover numbers up to 60 have been measured.The unusual orbital occupancy in 3 may be responsible for these observations.
- Murray, Robert W.,Pillay, M. Krishna
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- Structure-Reactivity Factors for Exciplex Isomerization of Quadricyclene and Related Compounds
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The quadricyclenes (1) and (3) are equally effective in exciplex isomerization although other cage hydrocarbons do not undergo efficient reaction when sensitized by aromatic fluorophores; irradiation of charge-transfer complexes of (1) and (3) and electron-deficient alkenes results in efficient valence but not geometrical isomerization.
- Jones, Guilford,Chiang, Sheau-Hwa,Becker, William G.,Greenberg, Don P.
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- Electron transfer induced deazatization of cyclic Azo derivatives of quadricyclane and norbornadiene
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The photosensitized oxidation of two cyclic azoalkane derivatives (Azo-Q, Azo-N) of quadricyclane (Q) and norbornadiene (N) has been investigated using steady-state and laser flash photolysis techniques as well as chemically induced dynamic nuclear polarization (CIDNP). Irradiation of acetonitrile solutions of 9,10-dicyanoanthracene (DCA), 2,6,9,10-tetracyanoanthracene (TCA), or chloranil (Chl) in the presence of Azo-Q results in rapid and efficient deazatization to afford N. Similar irradiation of DCA, TCA, and Chl in the presence of Azo-N yields N and Q. CIDNP experiments reveal that polarized N is formed as a cage product in the Chl sensitized photolysis of Azo-Q while polarized N and Q are both formed as cage products from Azo-N. The results are consistent with competitive fragmentation of Azo-N?+ to N?+ and Q?+, and selective deazatization of Azo-Q?+ to N?+. Irradiation of 1-cyanonaphthalene in the presence of Azo-Q or Azo-N affords Q and/or N in chemical yields similar to those obtained from direct and naphthalene sensitized irradiations, indicative of singlet energy transfer quenching. Bimolecular rate constants for quenching by Azo-N and Azo-Q were determined by steady-state fluorescence methods for singlet sensitizers, or by laser flash photolysis (LFP) for 3Chl*.
- Sluggett, Gregory W.,Turro, Nicholas J.,Roth, Heinz D.
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- THERMAL ISOMERIZATION OF QUADRICYCLANE TO NORBORNADIENE CATALYZED BY COPPER(II) AND TIN(II) SALTS.
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Copper(II) salts and tin(II) chloride show exceptional heterogeneous catalytic behavior in converting quadricyclane to norbornadiene in benzene. The heterogeneous catalysis mechanism is described by the adsorption of quadricyclane on the salt surface by a combination of a one-site and a two-site coordination. The two-site-coordination process results in the formation of C//7H//8X//2 (X equals Cl or Br) as a side product when CuCl//2 or CuBr//2 are used as catalysts. The rate constant for the disappearance of quadricyclane is much greater when CuCl//2 or CuBr//2 are used as catalysts. The rate constant for the disappearance of quadricyclane is much greater when CuCl//2 or CuBr//2 (approximately 10** minus **2 min** minus **1 cm** minus **2) is used than when CuSO//4 (approximately 10** minus **4 min** minus **1 cm** minus **2) is used.
- Fife,Morse,Moore
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- PHOTOISOMERIZATION OF NORBORNADIENE TO QUADRICYCLANE IN THE PRESENCE OF COPPER(I)-NITROGEN LIGAND CATALYSTS
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Use of copper(I)-nitrogen ligand catalysts, such as Ph3PCuCl.bipy (1), Ph3PCuCl.phen (2), Ph3PCuCl.phtha (3), and Ph3PCuBr.py (4), enables the photochemical isomerization of norbornadiene to quadricyclane in longer wavelength than 350 nm, in which CuCl catalyst itself can not induce such an isomerization.
- Maruyama, Kazuhiro,Terada, Kazutoshi,Naruta, Yoshinori,Yamamoto, Yoshinori
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- PHOTOGENERATED CATALYSIS BY TRANSITION-METAL COMPLEXES. PHOTOACCELERATION OF THE VALENCE ISOMERIZATION OF QUADRICYCLENE TO NORBORNADIENE IN THE PRESENCE OF PdCl2( eta 4-NORBORNADIENE).
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Light accelerates the rate at which PdCl//2( eta **4-NBD) (1) catalyzes the valence isomerization of quadricyclene (Q) to norbornadiene (NBD). The observed quantum yield, defined as (mol of NBD produced/mol of photons absorbed), can exceed 10**2 and is dependent upon Q concentration, light intensity, and solvent. Several lines of evidence are consistent with the intermediacy of radical species in the isomerization process. The results are discussed in terms of a redox-chain mechanism in which the initiation step involves reductive quenching of a Pd-to-NBD charge-transfer excited state of 1 by Q.
- Borsub,Kutal
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- Organic Photochemistry with 6.7 eV Photons: Tetracyclo2,7.04,6>heptane (Quadricyclene)
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Irradiation of quadricyclene in solution leads to isomeric products in addition to bicyclohepta-2,5-diene, which reduces its usefulness in solar energy storage.
- Srinivasan, Ra.,Baum, Thomas,Epling, Gary
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- Chemistry of Weakly Solvated Lanthanide-Metal Cations. Synthesis, Characterization, and Catalytic Chemistry of x
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The title compound, x, 1, was synthesized by the NOBF4 oxidation of metallic Eu in CH3CN.The interaction of the BF4- ions with the Eu(III) center was established by molecular weight, conductivity, and 11B and 19F NMR spectral measurements. 1 was found to exist as a dimer in CH3CN.In addition, it behaved as a 1:2 electrolyte, indicating the coordination of two of the BF4- ions per Eu(III) ion.However, the conductivity increased when chelating amines were added due to the partial displacement of the coordinated BF4- ions.The 11B and 19F NMR spectra of 1 in CH3CN indicated the presence of two different types of BF4- anions, one of which was isotropically shifted due to interaction with the paramagnetic Eu(III) center.The coordinated BF4- anions could be displaced quantitatively by the addition of 2 equiv of NO3- ions per Eu(III) ion.A degenerate metathesis of the fluorine between the BF3 and the coordinated BF4- ions was observed when BF3 was added to a CH3CN solution of 1. 1 formed a charge-transfer complex with tetra-p-anisylethylene in CH3NO2 but not in CH3CN.In addition, 1 initiated the oligomerization and the polymerization of styrene, α-methylstyrene, and 1,3-cyclohexadiene in CH3NO2.The molecular weights of the polymers obtained increased markedly on lowering the reaction temperature.At room temperature, indan derivatives were obtained from α-methyl- and α-phenylstyrene.The rate of polymerization of styrene was markedly attenuated when CH3CN was used instead of CH3NO2. 1 also initiated the isomerization of quadricyclane and the ring-opening polymerization of 2(10)-pinene and cyclopropylbenzene in CH3NO2.
- Thomas, Richard R.,Chebolu, Venkatasuryanarayana,Sen, Ayusman
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- Synthesis of tricyclononenes and tricyclononadienes containing MX 3-groups (M=C, Si, Ge; X=Cl, Me)
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A series of new organoelement-substituted (Si-, Ge-) tricyclononenes and tricyclononadienes was obtained via the [2σ+2σ+2π]-cycloaddition reaction of the corresponding substituted ethylenes and acetylenes with quadricyclane. The chemical behavior of Si-, Ge-, Sn-containing olefins and acetylenes under the cycloaddition conditions was studied.
- Bulgakov,Bermeshev,Demchuk,Lakhtin,Kazmin,Finkelshtein, E.Sh.
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- Fourier transform near-infrared absorption spectroscopic study of catalytic isomerization of quadricyclane to norbornadiene by copper(II) and tin(II) salts
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By using Fourier transform near-infrared (NIR) absorption spectroscopy, we have investigated the catalytic conversion of quadricyclane to norbornadiene. Either CuSO4 in chloroform or SnCl2 in benzene is used as catalyst. To avoid the effect of sample heterogeneity, the reaction mixture is kept still without stirring. The NIR light beam is guided to propagate through the solution right above the surface of metal salt. The NIR absorption spectra are acquired at 5-min intervals for a reaction period of 6 h. The related concentrations of quadricyclane and norbornadiene in the temporal evolution are determined with the method of partial least squares. A kinetic model for the pseudo-first-order reaction is derived considering the diffusion motion. Accordingly, the second-order rate constant for the isomerization catalyzed by CuSO4 and SnCl2, respectively, are determined to be (1.38 ?± 0.04) ?? 10-3 and (4.62 ?± 0.09) ?? 10-3 min-1 g-1. The norbornadiene is produced via a one-site coordination between the reactant and the catalyst. The product contribution from the intermediate of a two-site coordination is negligible in our system. The obtained result for CuSO4 is comparable with that detected by using Raman spectroscopy.
- Chuang, Eric Chau-Chin,Lin, King-Chuen
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- Valence Isomerization of Quadricyclene Mediated by Illuminated Semiconductor Powders
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Quadricyclene undergoes valence isomerization to norbornadiene in the presence of photoexcited n-type semiconductor powders.For samples irradiated under comparable conditions of time and intensity, the yield of the diene product varies with (i) the semiconductor in the order CdS > TiO2 > ZnO and (ii) the solvent in the order dichloromethane > acetonitrile > tetrahydrofuran.The presence of oxygen in a sample diminishes the product yield, whereas both methylviologen dication and diphenylamine enhance the yield.The quantum efficiency of norbornadiene production appearsto be rather low (ca. 10-2 for CdS) in these heterogeneous systems.These observations are interpreted in terms of the redox chemistry that results upon interaction of the photogenerated electron-hole pairs in the semiconductor with the surrounding organic medium.
- Ikezawa, Hideo,Kutal, Charles
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- LiCB11Me12: A catalyst for pericyclic rearrangements
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(matrix presented) Benzene and 1,2-dichloroethane solutions of the Li+ salt of the weakly coordinating anion CB11Me12- catalyze the rearrangement of cubane to cuneane, quadricyclane to norbornadiene, basketene to Nenitzescu's hydrocarbon, and diademane to triquinacene. The Claisen rearrangement of phenyl allyl ether is also strongly accelerated.
- Moss, Stefan,King, Benjamin T.,De Meijere, Armin,Kozhushkov, Sergei I.,Eaton, Philip E.,Michl, Josef
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- Overtone Vibrational Photochemistry of Quadricyclane
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The photochemistry of quadricyclane (Q) was explored by single-photon excitation to high vibrational levels.Spectra of the ν = 4-7 carbon-hydrogen overtones were recorded by using intracavity absorption and photoacoustic detection.These spectra were compared to the infrared fundamental spectrum and assigned.Excitation of the ν = 5 and ν = 6 bands of cyclopropanoid and methylenic hydrogens leads to reaction.At least one intermediate, probably a vibrationally excited form of norbornadiene (N), must be involved because partitioning among various reaction channels is pressure dependent.Apparent rate constants were measured and correlated with variations in pressure according to the Stern-Volmer relationship.Experimental values were compared with rate constants calculated by RRKM theory.Although there is a modest amount of "excess" reaction observed for the lowest excitation energies above threshold, overall evaluation provides no significant evidence for concentration of energy in localized modes for times that are long compared with reaction times.
- Lishan, David G.,Reddy, K. V.,Hammond, George S.,Leonard, Jack E.
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- Kinetics of the Isomerization of Quadricyclane to Norbornadiene Promoted by Tin(II) Chloride and Palladium(II) Chloride
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The conversion of quadricyclane to norbornadiene is promoted by both SnCl2 and PdCl2.The SnCl2 reaction occurs by a second-order process with activation parameters of ΔG(excit.), ΔH(excit.), and ΔS(excit.) of 22.5 kcal/mol, 13.9 kcal/mol, and -28.7 eu, respectively.The PdCl2-promoted reaction occurs by formation of an equilibrium species and follows Michaelis-Menton kinetics.A theoretical interpretation based on the Dewar-Duncanson model of bonding of metal ions with olefins is used to describe possible mechanistic differences in the reactions.
- Patrick, Timothy B.,Bechtold, Dana S.
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- Kinetics of catalytic isomerization of quadricyclane to norbornadiene using near infrared absorption spectroscopy: Conversion rate and diffusion motion in heterogeneous reaction
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By use of Fourier transform near-infrared (NIR) absorption spectroscopy and the aid of a kinetic model, we have investigated the conversion of quadricyclane to norbornadiene catalyzed by anhydrous CuSO4 and SnCl2 in chloroform. The reaction mixture is not agitated so as to avoid the effect of sample heterogeneity. The NIR absorption spectra are acquired, at a position a??2 mm above the catalyst surface, at 30-s intervals during 4 h. The concentrations of quadricyclane and norbornadiene are determined with the analysis of partial least squares. The isomerization of quadricyclane, as numerically solved from the model, is expected to describe its behavior more accurately in the catalytic system than that obtained previously. In addition to the isomerization rate, the kinetic model takes into account the contribution of diffusion. The diffusion coefficients of quadricyclane can be determined to be 3.8 ?? 10-5 cm2 s-1 in chloroform and 1.14 ?? 10-5 and 2.85 ?? 10-6 cm2 s-1 inside the CuSO4 and SnCl2 stacks, respectively. Diffusion is slowed inside the solid stacks, and thus the molecular mechanism cannot be suitable for this system. Given the diffusion coefficients, the pseudo-first-order depletion rate constants are evaluated to be (3.7 ?± 0.1) ?? 10-3 and (3.8 ?± 0.1) ?? 10-3 s-1 for CuSO4 and SnCl2, respectively. The corresponding second-order rate constants are determined to be (1.3 ?± 0.2) ?? 10-5 and (2.0 ?± 0.1) ?? 10-6 s-1 A-1 by considering the density and the size of the catalyst particles; A denotes the total catalyst surface area per unit effective volume of solvent. The rate constant with the CuSO4 catalyst is consistent with others obtained in a continuously stirred mixture. In the surface-mediated reaction, the catalytic isomerization is subject to one-site coordination (1:1 complex) between the reactant and the catalyst. Nevertheless, a two-site coordinated reaction cannot be excluded unless the interstitial size dependence of the depletion rate is known.
- Fan, Hsiu-Fang,Chin, Thou-Long,Lin, King-Chuen
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- Triplex Promoted Intersystem Crossing of Ion-Radical pairs in the Photosensitized Valence Isomerization of Quadricyclane: Chemically Induced Dynamic Nuclear Polarization (CIDNP) Evidence
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Photosensitized valence isomerization of quadricyclane to norbornadiene by dibenzoylmethanatoboron difluoride in the presence of durene shows a CIDNP effect which is opposite in direction to that occurring in the absence of durene, demonstrating possible participation of triplexes in the durene co-sensitized reaction.
- Yang, Li,Zhang, Mao-Xi,Liu, You-Cheng,Liu, Zhong-Li,Chow, Yuan L.
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- Reactions of Quadricyclane with Sulphur Dioxide: Formation of a Stable β-Sultine and Catalysed Isomerization to Norbornadiene
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Sulphur dioxide, as solvent or in chloroform, catalyses the isomerization of quadricyclane (1) to norbornadiene and cycloadds to (1) to afford exo-3-oxa-4-thiatricyclo2,5>non-7-ene 4-oxide (3); in the presence of a deficiency of sulphur dioxide, (3) is remarkably stable in solution, but decomposes rapidly as pure product.
- Lucchi, Ottorino De,Lucchini, Vittorio
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- The Radical Cations of Bicyclohepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and Bicycloocta-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR Study
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The radical cation of bicyclohepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1) in CF2ClCFCl2 and CF3CCl3 matrices and that of bicycloocta-2,5-diene (2,3-dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy.For 1+., the coupling constants of the olefinic, methano-bridge, and bridgehead protons are -0.780 +/- 0.005, +0.304 +/- 0.002, and -0.049 +/- 0.002 mT, respectively.The hyperfine tensor for the methano-bridge protons is axial.A = +0.263 +/- 0.002 and A = +0.386 +/- 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = -0.594 +/- 0.005, Ay = -0.913 +/-0.005, and Az = -0.834 +/- 0.005 mT (x parallel to C-H bond, z parallel to 2p? axis).For 2+., the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are -0.68 +/- 0.01, +0.162 +/- 0.005, and -0.108 +/- 0.005 mT, respectively.The hyperfine data for 1+. and 2+. fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(?), of the two bonding ethene ?-MO's.
- Gerson, Fabian,Qin, Xue-Zhi
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- Carbenes and the O-H Bond: Norbornenylidenes
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Bicyclohept-2-en-7-ylidene 10 and bicyclohept-5-en-2-ylidene 21 are shown to react with methanol by way of proton transfer, with formation of norbornenyl cations.
- Kirmse, Wolfgang,Meinert, Thomas
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- Rhodium(I) complexes of the conformationally rigid IBioxMe4 ligand: Preparation of mono-, bis-, and tris-ligated NHC complexes
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The preparation and characterization of a series of mono-, bis-, and tris-ligated rhodium(I) complexes of Glorius' conformationally rigid bioxazoline-derived N-heterocyclic carbene ligand IBioxMe4 are described. Through reaction of [Rh(COE)2Cl]2 (COE = cis-cyclooctene) with isolated IBioxMe4, [Rh(IBioxMe 4)(COE)Cl]2 (1), trans-[Rh(IBioxMe4) 2(COE)Cl] (2), and [Rh(IBioxMe4)3Cl] (3) were each isolated by careful choice of the reaction conditions. Further substitution and salt metathesis reactions of 1-3 were investigated, and derivatives containing CO, norbornadiene, and cyclopentadienyl ancillary ligands were readily isolated. Notably, halide abstraction from 2 and 3 using Na[BAr F4] (ArF = 3,5-C6H 3(CF3)2) resulted in the formation of low-coordinate T-shaped cis-[Rh(IBioxMe4)2(COE)][BAr F4] (9) and [Rh(IBioxMe4)3][BAr F4] (11). The solid-state structures of 2, 9, and 11 each feature IBioxMe4 ligands that bind unusually with tilted coordination geometries.
- Chaplin, Adrian B.
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- COBALT(II)TETRAPORPHYRIN-CATALYZED ISOMERISATION OF ELECTRONEGATIVE SUBSTITUTED QADRICYCLANES
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Co(II)TPP-catalyzed isomerisation of a series of electronegative substituted quadricyclanes(1) to the corresponding norbornadiene(2) was found to proceed via radicophilic attack of the metal to 1.
- Miki, Sadao,Ohno, Toshinobu,Iwasaki, Hideaki,Yoshida, Zen-ichi
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- Alumina-Anchored Cobalt Porphine Catalysts for the Conversion of Quadricyclane to Norbornadiene
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Methods are described for the preparation of cobalt(II) deuteroporphyrin and cobalt(II) tetrakis(p-sulfonatophenyl)porphine anchored on alumina beads coated with polyaminesulfone-A.Wavelength dispersive X-ray microanalysis showed that the cobalt(II) porphine distributes within the catalyst outer surface layer of ca. 100 μm depth.The catalysts are highly active for the cycloreversion of quadricyclane to norbornadiene.A detailed kinetics of the isomerization using an isothermal recycle reactor gave a rate expression of Langmuir-Hinshelwood type.The catalysts gradually lose their activity, which can be regenerated completely by heating the catalysts at 200 deg C in vacuo.
- Miki, Sadao,Asako, Yoshinobu,Morimoto, Masayoshi,Ohno, Toshinobu,Yoshida, Zen-ichi,et al.
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- ELECTROCHEMICAL CATALYSIS OF THE VALENCE ISOMERIZATION OF QUADRICYCLENE
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Electrochemical oxidation of quadricyclene results in its isomerization to norbornadiene by a redox chain mechanism.
- Yasofuku, Katsutoshi,Takahashi, Katsuo,Kutal, Charles
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- Thermal Decomposition of a Series of 1,2-Diazetines
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A homologous series of tricyclic diazetines (6a-c), differing by the number of methylene groups in the saturated bridges of the fused carbon bicycles, was synthesized. The ΔH? of decomposition for each of the diazetines to afford N2 and the corresponding alkene was determined experimentally: 6a, 31.7; 6b, 39.3; 6c, 38.8 kcal/mol. The ground-state strain energy of each diazetine was estimated utilizing computationally obtained ΔHf's for each of the experimentally investigated diazetines as well as several other diazetines whose ΔH?'s had been previously reported in the literature. The sum of the ground-state strain energies and ΔH?'s of decomposition for all of the diazetines was nearly constant, with an average value of 59 kcal/mol, suggesting that all of the diazetines decompose via the same mechanism. Generally, the higher the ground-state strain energy of the diazetine, the less the ΔH? for decomposition. The decomposition transition states for 6a-c and 7 were modeled computationally at the RB3LYP/6-311+G(3df,2p)//UB3LYP/6-31+G(d,p) level. The agreement of the experimentally determined ΔH? values with transition-state energies obtained computationally supports the reaction mechanism originally proposed by Yamabe that the elimination process occurs by an unsymmetrical, yet concerted, transition state with strong biradical character.
- Breton, Gary W.,Shugart, John H.
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- Endo entry to the nortricyclyl-norbornenyl cation system: Stereochemistry in the fragmentation of endo-5-norbornenyl-2-oxychlorocarbene
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Fragmentation of (S)-endo-5-norbornenyl-2-oxychlorocarbene [(S)-8] in cyclohexane-d12 gives ～20% (S)-endo-2-chloro-5-norbornene [(S)-7] with ～50% ee, 65-70% (R)-exo-2-chloro-5-norbornene [(R)-4] with >95% ee, and ～12% (R)-3-nortricyclyl chloride [(R)-5] with ～22% ee. (Analogous stereochemical results were also obtained starting with the enantiomeric carbene (R)-8.) The (S)-8 to (S)-7 and (S)-8 to (R)-4 conversions are ascribed mainly to retention and inversion SNi transition states, respectively. These have been located by computational methods and are nearly isoenergetic. In more polar solvents (CDCl3 and CD3CN), the fragmentation of (S)-8 increasingly occurs via competitive ion pair pathways in which steroselectivity is diminished, and escape to the norbornenyl-nortricyclyl cation directs the products away from endo-2-chloro-5-norbornene toward exo-chloride 4 and nortricyclyl chloride 5.
- Moss, Robert A.,Fu, Xiaolin,Sauers, Ronald R.,Wipf, Peter
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- Cycloreversion of Quadricyclane to Norbornadiene Catalyzed by Tin (II) Complexes
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The conversion of quadricyclane (1) to norbornadiene (2) is catalyzed by stannous chloride and stannous chloride-phosphine complexes.A newly synthesized polymer-bound phosphine-stannous chloride complex also proved effective in the catalytic conversion 1 to 2.
- Landis, M.E.,Gremaud, D.,Patrick, T.B.
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- Pyrolysis of Bicycloheptane-2-thiols: Evidence for a Carbene Intermediate in a Thermal Hydrogen Sulphide Elimination
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Pyrolysis of endo- and exo-bicycloheptane-2-thiols yields tricyclo2,6>heptane and bicyclohept-2-ene via competing carbene and radical mechanisms.
- Johnson, Douglas E.,Dimian, Adel F.
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- Rh(III)-photosensitized interconversion of norbornadiene and quadricyclane
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The utility of two Rh(III) diimine complexes, Rh(phen)33+ and Rh(phi)2(phen)3+ (phen = 1,10-phenanthroline, phi = 9,10-phenanthrenequinone diimine), as sensitizers for the interconversion of norbornadiene (N) and quadricyclane (Q) has been investigated using steady-state photochemical and laser flash photolysis (LFP) techniques. Irradiation of acetonitrile solutions of Rh(phen)33+ and N causes slow conversion to Q. The reaction is reversible; irradiation of Rh(phen)33+ in the presence of Q leads to N. Irradiation of acetonitrile solutions of Rh(phi)2(phen)3+ and Q yields N. However, this reaction is irreversible; irradiation of the Rh-(III) complex in the presence of N fails to afford Q. Irradiation of methanol solutions of either Rh(III) complex in the presence of N or Q affords minor amounts of two methanol-C7 adducts but fails to quench the N-Q interconversion reaction. The results are consistent with N-Q interconversion via an exciplex intermediate. The Rh(III)-sensitized deazatization of two cyclic azoalkane derivatives (Azo-N, Azo-Q) of N and Q was also investigated. Deazatization was achieved by Rh(phen)33+ but not Rh(phi)2(phen)3+ sensitization. The results are consistent with a mechanism involving triplet energy transfer, but the involvement of exciplex intermediates cannot be ruled out. Bimolecular rate constants for quenching of the Rh(III) excited states by N, Q, Azo-N, and Azo-Q were determined by LFP.
- Sluggett, Gregory W.,Turro, Nicholas J.,Roth, Heinz D.
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- Photosensitization of Quadricyclene Isomerization by Electron Acceptors. A Short-Circuit Nonradiative Decay Mechanism for Electron Donor-Acceptor Quenching in Polar Media
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Quantum efficiences are reported for valence isomerization of quadricyclene to norbornadiene induced on quenching the excited singlet state of electron acceptor sensitizers.The notable feature is the large reduction in yield of isomerization in a polar solvent (acetonitrile) compared with reported data for similar photolysis in nonpolar media.A comparison of isomerization yields and flash photolysis results based on the mode of sensitization (i.e., singlet quenching vs. triplet quenching vs. excitation of ground-state charge-transfer complexes) leads to a distinction among exciplex, contact ion pair, and solvent-separated ion-pair intermediates which are potentially involved in electron donor-acceptor quenching.
- Jones, Guilford,Chiang, Sheau-Hwa,Becker, William G.,Welch, Jeanne A.
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- PHOTOINDUCED ADDITION OF NUCLEOPHILES TO BICYCLOHEPTA-2,5-DIENE
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The 1-cyanonaphthalene photosensitized addition of water and methanol to the cation-radical of bicyclohepta-2,5-diene is described.
- Gassman, Paul G.,Olson, Kurt D.
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- Catalytic carbonylative rearrangement of norbornadiene via dinuclear carbon-carbon oxidative addition
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Single bonds between carbon atoms are inherently challenging to activate using transition metals; however, ring-strain release can provide the necessary thermodynamic driving force to make such processes favorable. In this report, we describe a strain-induced C-C oxidative addition of norbornadiene. The reaction is mediated by a dinuclear Ni complex, which also serves as a catalyst for the carbonylative rearrangement of norbornadiene to form a bicyclo[3.3.0] product.
- Hartline, Douglas R.,Zeller, Matthias,Uyeda, Christopher
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supporting information
p. 13672 - 13675
(2017/11/07)
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- REDOX-AUXILIARY CATALYSIS
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Disclosed herein is a method of activating a compound for a chemical reaction comprising functionalizing a compound with a redox auxiliary group and oxidizing the redox auxiliary group that is bonded to the compound, thereby activating the compound, wherein the activated compound undergoes a chemical reaction to form a product and the oxidation of the redox auxiliary group is reversible. Methods of making and using these materials are also disclosed.
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Paragraph 0007; 0101
(2015/05/26)
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- Solar driven uphill conversion of dicyclopentadiene to cyclopentadiene: An important synthon for energy systems and fine chemicals
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The retro Diels-Alder conversion of endo-dicyclopentadiene to cyclopentadiene (Cp)-which is thermodynamically uphill under ambient conditions (ΔG = +9.7 kcal mol-1; values based on computation at 273 K following CBS-QB3 methodology)-was carried out at 175-190 °C in neat state using solar energy. The reaction is thermodynamically favorable at elevated temperature. Considering heat release from the reverse reaction (ΔH = -23.4 kcal mol-1), the energy storage efficiency was computed to be ca. 5.5% with respect to the IR component in concentrated solar radiation. Solar energy was further utilized for preparation of a model 2,5-norbornadiene derivative (75% isolated yield) through the cycloaddition reaction of Cp with 4-phenylbut-3-yn-2-one at 150-185 °C. The norbornadiene-quadricyclane system has been proposed for solar energy storage, and its solar assisted synthesis would help reduce its carbon footprint over its life cycle. Norbornadiene synthesis using solar energy may also be of interest for greener processing of fuels derived from this compound. Cookson's cage ketone, which too has been proposed as an energy storage medium, was additionally synthesized from the Diels-Alder adduct of Cp and p-benzoquinone employing concentrated solar photo-thermochemical conditions. The reaction proceeded rapidly (15 min) and gave the desired product in 96% isolated yield. Besides the above applications, Cp is an important synthon in the preparation of fine chemicals.
- Dinda, Milan,Chakraborty, Supratim,Kanti Si, Mrinal,Samanta, Supravat,Ganguly, Bishwajit,Maiti, Subarna,Ghosh, Pushpito K.
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p. 54558 - 54564
(2015/02/05)
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- Microwave-assisted ring opening reaction
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The present invention is directed to a ring opening reaction of heteronorbomenes and other α,β-unsaturated compounds of formula (Ia) and (Ib): with a nucleophile in the presence of a transition metal complex, characterized in that it is microwave assisted.
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Page/Page column 14
(2009/07/10)
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- Rhodium-phosphorus complexes and their use in ring opening reactions
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The present invention is directed to novel rhodium-phosphorus complexes of formula: ???????? [Rh(PP')(solv)2]X the process for their preparation and their use as catalysts in the ring opening reaction of heteronorbomenes and other α,β-unsaturated compounds.
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Page/Page column 17
(2009/07/10)
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- The synthesis and the spectral characterization of new bicyclo[2.2.1] heptadiene derivatives
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The synthesis of 3, 7-dihydroxymethyl-exo-eco-tetracyclo[2.2.1.1.1.0 2,406,8] nonane(lα,2β,3β,4β,5α, 6β,7β,8β) (7), 3, 7-diformyl-exo-exo-te1racyclo[2.2.1.1.1.0 2,406,8)-nonane(lα,2β,3β,4β,5α, 6β,7β,8β) (8) and bistosylhydrazone of 3, 7-diformyl-exo-exo- tetracyc1o[2.2.1.1.1.02,406,8] nonane (lα,2β, 3β,4β,5α,6β,7β,8β) (2) are presented. High- resolution 1H- and 13C-NMR spectra of the above compounds are discussed underling the stereochemistry of 3,7-disubstituted - exo-exo-tetracyclo[2.2.1.1.1.02,406,8] nonane. The Bamford-Stevens reaction of bistosylhydrazones 2 (corresponding to 8) affords as main product the alkene l(BCH).
- Olteanu, Emilia,Draghici, Constantin,Caproiu, Miron T.
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experimental part
p. 837 - 840
(2009/12/25)
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- Influence of carbocation stability in the gas phase on solvolytic reactivity: Beyond bridgehead derivatives
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The intrinsic gas-phase stability of bicyclic secondary carbocations has been determined by Dissociative Proton Attachment of chlorides and alcohols, respectively. From these data, Gibbs free energies for hydride transfer relative to 1-adamantyl (ΔrG°(8,exp)) are derived after application of appropriate leaving group corrections, and good agreement with theoretical values, (ΔrG°(8,comp)), calculated at the G2(MP2) or MP2/6-311G(d,p) level, is reached (Table 1). The relative rate constants for solvolysis (log(k/k0)) of the bicyclic secondary derivatives correlate with the stabilities of the respective carbocations in the same manner as tertiary bridgehead derivatives, but simple monoderivatives and acyclic derivatives solvolyze faster than predicted on the grounds of the ion stabilities. The corresponding stabilities of cyclopropyl- and benzyl-substituted carbocations have been obtained by a combination of experimental and computational data available in the literature with computational methods. Correlation of the rate constants for solvolysis vs ion stabilities for these compounds reveals a trend similar to that observed for bridgehead derivatives, but with much more scatter, which is attributed to nucleophilic solvent participation and/or nucleophilic solvation.
- Abboud, Jose-Luis M.,Alkorta, Ibon,Davalos, Juan Z.,Mueller, Paul,Quintanilla, Esther,Rossier, Jean-Claude
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p. 3786 - 3796
(2007/10/03)
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- The cause of the rate acceleration by diethyl ether solutions of lithium perchlorate (LPDE) in organic reactions. Application to high pressure synthesis
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Kinetic studies of isoprene cyclodimerization show that the accelerating effect caused by LPDE (solution of lithium perchlorate in diethyl ether) in some organic reactions cannot be ascribed to internal pressure of LPDE. The kinetic effect is essentially due to catalysis through Li+. Additional arguments are provided by comparison of yields obtained in LPDE (0.1 MPa) and in organic solvents (under pressure) for Diels-Alder reactions of various electronic types. Combination of high pressure and LPDE catalysis is revealed as an excellent multiactivation process to achieve difficult syntheses, but only for [4 + 2] cycloadditions.
- Jenner, Gerard,Salem, Ridha Ben
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p. 4637 - 4648
(2007/10/03)
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- Rearrangement and Cycloreversion of Diels-Alder Adducts of Cyclic 1,3-Dienes to Norbornadienes. A Novel homo-Cope Rearrangement. Evidence for Competitive Pericyclic and Diradical Processes
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On thermolysis of endo,endo-5, endo,endo-17, and endo,exo-17 ( the endo,endo and endo,exo Diels-Alder adducts of cyclopentadiene 7 or dimethylfulvene 15 to norbornadiene 8 or 7-isopropylidenenorbornadiene 20), a novel type of homo-Cope rearrangement leading to 6, 21, and 23a, respectively, competes with the retro-Diels-Alder reactions.According to a force-field analysis of the kinetic parameters, the competitive reactions (rearrangement and retro-Diels-Alder reaction) of endo,endo-5 occur in a pericyclic fashion whereas in the isopropylidene-substituted systems stepwise processes compete with the corresponding pericyclic reactions.Indirect experimental evidence for this assumption comes from a stereochemical analysis of the retro-Diels-Alder reaction in the cis-5,6-dideuterionorbornene derivatives exo-36-d2, endo-36-d2 and exo-39-d2, endo-39-d2 occuring stereospecifically in the case of exo-36-d2, endo-36-d2 and non-stereospecifically in the case of exo-39-d2, endo-39-d2.The change in mechanism rationalized by a different (allyl vs. pentadienyl) stabilization of the potential diradical intermediates in the stepwise reactions. - Key Words: Kinetic parameters / Stepwise and pericyclic reactions / Calculations, force field / Calculations of transition-state resonance energy (energy of concert)
- Hochstrate, Dirk,Klaerner, Frank-Gerrit
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p. 745 - 754
(2007/10/02)
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- 1-Benzenesulfonyl-2-trimethylsilylacetylene: a New Acetylene Equivalent for the Diels-Alder Reaction
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1-Benzenesulfonyl-2-trimethylsilylacetylene has been shown to be an effective acetylene equivalent for the Diels-Alder reaction.
- Williams, Richard Vaughan,Chauhan, Kamlesh,Gadgil, Vijay R.
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p. 1739 - 1740
(2007/10/02)
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- Rose-Bengal-Sensitized Photooxidation of Quadricyclane. A Cycloaddition of Singlet Oxygen
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Quadricyclane was photooxygenated with singlet oxygen generated under Rose-Bengal-sensitized conditions to a dioxetane, which in turn gave 2-cyclopentene-1,4-dicarbaldehyde and 5-norbornene-cis-2,3-exo-diol.For the mechanism to form the dioxetane, an involvement of a electrocyclic process is proposed.
- Hatsui, Toshihide,Takeshita, Hitoshi
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p. 129 - 132
(2007/10/02)
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- Structural variants of tetranuclear L4Cu4X4. Influence of L on the coordination mode of copper(I)
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Three π complexes between nonconjugated dienes and copper(I) chloride and/or bromide have been prepared and characterized by means of crystal structure determination. The complex between 1,4-pentadiene and copper(I) chloride (1) was prepared in ethyl vinyl ketone (1-penten-3-one), utilizing the complex between copper(I) chloride and the solvent as an in situ precursor. [Cu2Cl2(C5H8)] (1) crystallizes in the orthorhombic space group Pccn with a = 7.292 (4) A?, b = 14.146 (3) A?, c = 15.727 (4) A?, and Z = 8, and the structure was refined to a final R = 0.065 (Rw = 0.080) for 82 parameters and 890 observed reflections. The compound contains a distorted cubane Cu4Cl4 core, bridged by π-coordinated 1,4-pentadiene ligands, to form an infinite ribbon. The copper(I) centers exhibit distorted tetrahedral (trigonal pyramidal) coordination geometry. Compounds 2 and 3, [Cu4Br2Cl2(C7H8) 4] and [Cu4Br4(C7H8)4], respectively, prepared by direct reaction between copper(I) halide and norbornadiene, are isostructural, crystallizing in the tetragonal space group P421c, with Z = 2. Cell constants are a = 12.187 (3) and c = 9.668 (2) A? (2) and a = 12.245 (2) and c = 9.759 (2) A? (3). The structures were refined to final R = 0.038 (Rw = 0.043) (2) and R = 0.029 (Rw = 0.033) (3). Both 2 and 3 are discrete tetramers with distorted Cu4X4 cores, each norbornadiene ligand being π-coordinated to copper(I) through one olefinic linkage. The factors which favor a regular or a distorted cubic cage in tetranuclear L4Cu4X4 are discussed by means of extended Hu?ckel calculations (EHT). It is shown that a regular cubane-type structure is preferred when L is a pure σ-donor ligand. In contrast, when L is a π-acceptor ligand, two types of distortion in which four of the cube edges are elongated are possible. These two structures, which differ in the geometrical arrangement of the four long bonds, are shown to be the only possible isomers. It is demonstrated that these distortions are due to the presence of a moderately active d block and low-lying s and p blocks on the Cu(I) center. This specific orbital pattern makes the coordination of copper(I) highly variable.
- Hakansson, Mikael,Jagner, Susan,Clot, Eric,Eisenstein, Odile
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p. 5389 - 5394
(2008/10/08)
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- 1,3-Diketonatoboron difluoride sensitized cation radical reactions
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Dibenzoylmethanatoboron difluoride (DBMBF2) and allied BF2 complexes interact from their singlet excited state with trans-anethole (t-A), quadricyclene (QC) and norbornadiene (NBD) by electron transfer to generate the corresponding cation radicals, which undergo the reported reactions.By sensitization, t-A undergoes dimerization to form the anti head-to-head and syn head-to-head dimers with retention of stereochemistry.The formation is reversible under sensitization conditions, leading to accumulation of the more stable anti isomer.However, irradiation of the absorption band of the DBMBF2 - t-A ground state complex did not lead to dimerization of t-A.By DBMBF2 sensitization, QC is cleanly converted to NBD while NBD is not affected.The calculation shows QC+* possesses higher energy than NBD+* by 7.5 kcal/mol, hence an irreversible rearrangenment.Other sensitizers (e.g., cyanoaromatics and tetrachlorobenzoquinone) also promote these cation radical reactions but not as cleanly as DBMBF2. Key words: photosensitization by boron complexes, cation radical rearrangement, cation radical cycloaddition, electron transfer sensitization, photoreaction of ground state complexes.
- Chow, Y. L.,Cheng, Xianen
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p. 1331 - 1336
(2007/10/02)
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- SYNTHESIS OF NEW TYPES STRAINED HYDROCARBONS BY CYCLOCODIMERIZATION OF QUADRICYCLE WITH NORBORNENES AND THEIR DERIVATIVES, CATALYZED BY PALLADIUM COMPLEXES
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The codimerization of quadricyclane (QC), the valence isomer of norbornadiene (NBD), with norbornene compounds was studied in the presence of Pd(O) complexes.Codimerization of QC with norbornene, 5-methyl- and 5-methylenenorbornene, exo-tricyclo2,4>octene-6, tetracyclo2,4.03,7>nonene-8, and penta- and hexacyclic NBD dimers was carried out in the presence of PPh3-activated Pd2(DBA)3*CHCl3 to afford a new class of hexa- to nonacyclic strained hydrocarbons with exo- and endo-tetracyclo2,4.03,7>nonane fragments.
- Dzhemilev, U.M.,Khusnutdinov, R.I.,Dokichev, V.A.,Galeev, D.K.,Malikov, A.I.,et al.
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p. 2247 - 2251
(2007/10/02)
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- Adduct between (η-Cyclopentadienyl)(1,2-diphenyl-1,2-ethylenedithiolato)rhodium(III) and Quadricyclane
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(η-Cyclopentadienyl)(1,2-diphenyl-1,2-ethylenedithiolato)rhodium(III) complex (1) reacts with quadricyclane (Q) to give a 1:1 adduct in which Rh and S of the complex are bridged by 5-norbornene-2,3-diyl group.The adduct dissociates to give 1 and norbornadiene upon irradiation with a medium pressure mercury lamp.
- Kajitani, Masatsugu,Eguchi, Yukata,Abe, Ryuko,Akiyama, Takeo,Sugimori, Akira
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p. 359 - 362
(2007/10/02)
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- Photochemistry of "salted" quadricyclane and norbornadiene: Alkali halide color centers as catalysts
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Quadrtcyclane "salted" in CsI or KBr or in with is rapidly into norbornadiene under condition that induce color centre formation in the haide: rapid-growth vapor or UV or X-ray irradiation. The reaction proceeds at where the H centers are mobile. At lower temperatures, UV irradiation of norbornadiene converts it into quadricyclane in the fashion.
- Kirkor, Ewa S.,Maloney, Vincent M.,Michl, Josef
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p. 148 - 151
(2007/10/02)
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- The Methylene Blue-Sensitized Photooxidation of Quadricyclane, Reinvestigated
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Photooxygenation of quadricyclane (1) was shown to proceed via the electron transfer mechanism on the basis of the structure revision of a methoxy alcohol.Photoisomerization of 1 to norbornadiene occurred during the irradiation.
- Hatsui, Toshihide,Takeshita, Hitoshi
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p. 1253 - 1254
(2007/10/02)
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- Protolytic Cleavage of Tricyclo2,7>hept-3-ene
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Acidolyses of the title compound 9 were performed in aqueous dioxane and in acetic acid to give eight alcohols (5-8, 10-13) among which bicyclohept-2-en-exo-6-ol (13) was novel.Comparison with independent routes to the various cationic intermediates reveals that the double bond and the cyclopropane ring of 9 react at similar rates and with high regioselectivity.Protonation occurs preferentially, if not exclusively, at C-4 and C-7.
- Kirmse, Wolfgang,Streu, Joachim
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p. 551 - 554
(2007/10/02)
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- Surface photochemistry: Semiconductor mediated reactions of some saturated strained hydrocarbons
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Quadricyclane (1) and 1,8-bishomocubane (2) have been found to undergo valence isomerization to norbornadiene and tricyclo2,5>deca-3,7-diene, respectively, on illuminated CdS and ZnO.An electron transfer mechanism is proposed.Quantum yield, solvent effects, the role of oxygen, and the quenching of the reaction were investigated, and were consistent with this interpretation.The thermal reaction of 1 on CdS was also suggested to be an electron transfer process involving, in this case, defects or trapped holes on the surface of the semiconductor.An examination of a series of strained hydrocarbons structurally related to 1 (tetracyclo2,8.04,6>octane 3, pentacyclo2,4.03.8.05.7>nonane 4 and pentacyclo2,4.03,8.05,7>decane 5) resulted, largely, in a demonstration of the resistance of their respective radical cations to rearrangement prior to back electron transfer.Calculations by MNDO, in combination with a modified version of MM2, were used to explore the differences in the reactivity of the radical cations of 1, 3, 4, 5, and an interpretation is presented.
- Baird, N. Colin,Draper, Anthony M.,Mayo, Paul De
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p. 1579 - 1588
(2007/10/02)
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- Heat of reaction of (norbornadiene)molybdenum tetracarbonyl with monodentate and bidentate ligands. Solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4
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The enthalpy of reaction of (NBD)Mo(CO)4 (NBD = norbornadiene) with a number of monodentate and bidentate ligands forming cis-L2Mo(CO)4 has been measured at 30°C in THF solution. The heats of reaction span a range of 33 kcal/mol. The order of stability for monodentate ligands is PCl3 6H5)3 6H5)3 3 6H5)3 6H5)2(CH3) 6H5)(CH3)2 3)3 3 6H11)NC 3 3. The series of chelating bidentate phosphines R2P-(CH2)nPR2 (n = 1-4, R = C6H5; n = 1, 2, R = CH3) and several related ligands were investigated. The chelating ring systems in the metallacycles show strain energies of about 8 kcal/mol for four-membered rings. The mixed ligand (C6H5)2PCH2CH2-As(C 6H5)2 shows a heat of binding midway between the heats of binding of (C6H5)2PCH2CH2P(C 6H5)2 and (C6H5)2AsCH2C-H2As(C 6H5)2, implying group additivity in this system. The complex (phen)Mo(CO)4 is some 5 kcal/mol more stable than (bpy)Mo(CO)4, presumably due to conformational effects in the free ligand. The ligand 1,5-cyclooctadiene forms a complex 2 kcal/mol less stable than that of norbornadiene. The influences of steric and electronic factors in determining the Mo-L bond strength are discussed.
- Mukerjee, Shakti L.,Nolan, Steven P.,Hoff, Carl D.,Lopez De La Vega, Ramon
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- Forbidden Reactions.- Cycloreversion of Rigid Cyclobutanes
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Cyclobutane derivatives, severely restrained from generating noninteractive 1,4-diradicals, are examined thermochemically to provide quantitative evidence to support a forbidden-concerted, antiaromatic mechanism for their cyclorevision.
- Doering, William v. E.,Roth, Wolfgang R.,Breuckmann, Rolf,Figge, Lutz,Lennartz, Hans-Werner,et al.
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- Cyclic Olefins by Anodic Oxidation of β-(Trimethylsilyl)carboxylic Acids. - β-(Trimethylsilyl)acrylic Acid Derivatives as Acetylene Equivalents in Diels-Alder Reactions
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Trimethylsilyl-substituted dienophiles 1, 2, and 4 react with dienes 6-14 in 66-100percent yields to give β-trimethylsilyl-substituted carboxylic acids 15-25, some of which are hydrogenated to 26-31.These are decarboxylated-desilylated to cyclic olefins 35-47 by Non-Kolbe electrolysis in 45-91percent yields.The dienophiles 1, 2, and 4 are thus suitable acetylene equivalents for Diels-Alder reactions.
- Hermeling, Dieter,Schaefer, Hans J.
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p. 1151 - 1158
(2007/10/02)
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- TRANSFER TECHNOLOGY II. Preparation of Transfer Reagents for the Site Specific Delivery of Disubstituted Cyclobutadienes and their use in the Synthesis of Hetero Bridged Propellanes.
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Transfer reagents (11) and (18) are used as synthetic equivalents for disubstituted cyclobutadienes in a new protocol for the synthesis of the heteropropellanes (5), (6), and (16).
- Butler, Douglas N.,Officer, David L.,Pitt, Ian G.,Russel, Richard A.,Warrener, Ronald N.
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p. 6507 - 6510
(2007/10/02)
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- Exothermic Isomerization of Water-soluble Quadricyclanes to Norbornadienes by Soluble and Insoluble Catalysts
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Water-soluble quadricyclane derivatives (1) were stable in an aqueous sodium carbonate solution, but addition of a catalytic amount of water-soluble cobalt porphyrin complexes (3) induced rapid and quantitative isomerization of (1) to norbornadiene derivatives (2) under release of heat.Insoluble catalysts (4) prepared by adsorption of Co-TPP or Co-Pc on activated carbon were similarly active as the soluble analogues.They were stable enough to keep high activities for recycling use.
- Maruyama, Kazuhiro,Tamiaki, Hitoshi,Kawabata, Shigeki
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p. 543 - 550
(2007/10/02)
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