Cyclooctatriene

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Take-aki Mitsudo - One of the best experts on this subject based on the ideXlab platform.

Teruyuki Kondo - One of the best experts on this subject based on the ideXlab platform.

Kendall N. Houk - One of the best experts on this subject based on the ideXlab platform.

  • Terminal Substituent Effects on the Reactivity, Thermodynamics, and Stereoselectivity of the 8π–6π Electrocyclization Cascades of 1,3,5,7-Tetraenes
    2015
    Co-Authors: Ashay Patel, Kendall N. Houk
    Abstract:

    M06-2X/6-31+G­(d,p) computations are reported for the 8π–6π electrocyclization cascades of 1,3,5,7-tetraenes. The rate-determining step for these cascades is typically the second (6π) ring closure. According to experiment and theory, un- and monosubstituted tetraenes readily undergo 8π electrocyclic ring closure to form 1,3,5-Cyclooctatrienes; however, the 6π electrocyclizations of these Cyclooctatriene intermediates are slow and reversible, and mixtures of monocyclic and bicyclic products are formed. Computations indicate that di- and trisubstituted tetraenes undergo facile but less exergonic 8π electrocyclization due to a steric clash that destabilizes the 1,3,5-Cyclooctatriene intermediates. Relief of this steric clash ensures the subsequent 6π ring closures of these intermediates are both kinetically facile and thermodynamically favorable, and only the bicyclic products are observed for the cascade reactions of naturally occurring tri- and tetrasubstituted tetraenes (in agreement with computations). The 6π electrocyclization step of these cascade electrocyclizations is also potentially diastereoselective, and di- and trisubstituted tetraenes often undergo cascade reactions with high diastereoselectivities. The exo mode of ring closure is favored for these 6π electrocyclizations due to a steric interaction that destabilizes the endo transition state. Thus, theory explains both the recalcitrance of the unsubstituted 1,3,5,7-octatetraene and 1-substituted tetraenes toward formation of the bicyclo[4.2.0]­octa-2,4-diene products, as well as the ease and the stereoselectivity with which terminal di- and trisubstituted tetraenes are known to react biosynthetically

  • Terminal substituent effects on the reactivity, thermodynamics, and stereoselectivity of the 8π-6π electrocyclization cascades of 1,3,5,7-tetraenes.
    The Journal of organic chemistry, 2014
    Co-Authors: Ashay Patel, Kendall N. Houk
    Abstract:

    M06-2X/6-31+G(d,p) computations are reported for the 8π-6π electrocyclization cascades of 1,3,5,7-tetraenes. The rate-determining step for these cascades is typically the second (6π) ring closure. According to experiment and theory, un- and monosubstituted tetraenes readily undergo 8π electrocyclic ring closure to form 1,3,5-Cyclooctatrienes; however, the 6π electrocyclizations of these Cyclooctatriene intermediates are slow and reversible, and mixtures of monocyclic and bicyclic products are formed. Computations indicate that di- and trisubstituted tetraenes undergo facile but less exergonic 8π electrocyclization due to a steric clash that destabilizes the 1,3,5-Cyclooctatriene intermediates. Relief of this steric clash ensures the subsequent 6π ring closures of these intermediates are both kinetically facile and thermodynamically favorable, and only the bicyclic products are observed for the cascade reactions of naturally occurring tri- and tetrasubstituted tetraenes (in agreement with computations). The 6π electrocyclization step of these cascade electrocyclizations is also potentially diastereoselective, and di- and trisubstituted tetraenes often undergo cascade reactions with high diastereoselectivities. The exo mode of ring closure is favored for these 6π electrocyclizations due to a steric interaction that destabilizes the endo transition state. Thus, theory explains both the recalcitrance of the unsubstituted 1,3,5,7-octatetraene and 1-substituted tetraenes toward formation of the bicyclo[4.2.0]octa-2,4-diene products, as well as the ease and the stereoselectivity with which terminal di- and trisubstituted tetraenes are known to react biosynthetically.

  • Transition Structures of the Electrocyclic Reactions of cis,cis,cis‐1,3,5‐Cyclooctatriene
    Israel Journal of Chemistry, 1993
    Co-Authors: Bert E. Thomas, Jeffrey D. Evanseck, Kendall N. Houk
    Abstract:

    The electrocyclic reactions of cis,cis,cis-1,3,5-Cyclooctatriene have been studied using ab initio molecular orbital theory. cis,cis,cis-1,3,5-Cyclooctatriene can undergo an electrocyclic ring opening in a conrotatory fashion to form cis,cis-1,3,5,7-octatetraene and a disrotatory electrocyclization to form bicyclo[4.2.0]octa-2,4-diene. The transition structures for these electrocyclic reactions have been located. Geometry optimizations employed restricted Hartree-Fock calculations and the 3–21G and 6–31G* basis sets. Electron correlation energies were calculated using second-order, and in some cases fourth-order, Moller-Plesset theory. Scaled RHF/6–31G* force constants were employed in the prediction of secondary deuterium isotope effects for the conrotatory ring opening. The ground state of cis,cis,cis-1,3,5-Cyclooctatriene exists in a twist-boat conformation with staggering at the saturated linkage. The transition structure for the conrotatory electrocyclic ring opening to form cis,cis-1,3,5,7-octatetraene has a helical structure, which has implications for the stereoselectivities of ring closure of 1-substituted-cis,cis-1,3,5,7-octatetraenes. The disrotatory transition structure for the electrocyclization to form bicyclo[4.2.0]octa-2,4-diene is strongly distorted from Cs symmetry, in contrast to the transition structure for the disrotatory electrocyclization of cis-1,3,5-hexatriene. This distortion is caused by staggering about the saturated linkage.

Toshiaki Suzuki - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and characterization of a novel (μ3-oxo)tetraruthenium cluster
    Journal of Organometallic Chemistry, 2006
    Co-Authors: Teruyuki Kondo, Toshiaki Suzuki, Kenji Wada, Fumiaki Tsunawaki, Yasuyuki Ura, Syuhei Yamaguchi, Hideki Masuda, Kenji Yoza, Motoo Shiro, Take-aki Mitsudo
    Abstract:

    Abstract A novel (μ 3 -oxo)tetraruthenium cluster ( 2 ) was synthesized in an isolated yield of 73% by the reaction of a zerovalent ruthenium complex, Ru(η 6 -cot)(η 2 -dmfm) 2 ( 1 ) [cot = 1,3,5-Cyclooctatriene, dmfm = dimethyl fumarate], with water under reflux in 1,4-dioxane for 6 h. The structure and the X-ray characterization of this novel complex 2 as well as a possible formation mechanism of 2 are disclosed.

  • Synthesis of novel zerovalent ruthenium η6-arene complexes via direct displacement of a 1,3,5-Cyclooctatriene ligand by arenes
    Organometallics, 2003
    Co-Authors: Yasuyuki Ura, Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Kazuo Sadaoka, Take-aki Mitsudo
    Abstract:

    Novel zerovalent arene complexes bearing two dimethyl fumarate ligands, Ru(η6-arene)(dimethyl fumarate)2 (arene = benzene (2a), toluene (2b), p-xylene (2c), mesitylene (2d), hexamethylbenzene (2e), tert-butylbenzene (2f), anisole (2g), N,N-dimethylaniline (2h), biphenyl (2i), methyl benzoate (2j), naphthalene (2k)), were synthesized via the direct ligand exchange reaction of Ru(η6-cot)(dimethyl fumarate)2 (1; cot = 1,3,5-Cyclooctatriene) with arenes. The detailed structures of 2g,h were determined by X-ray crystallography, which revealed that the coordination geometry can be represented by a highly distorted trigonal bipyramid.

  • Synthesis, Structure, and Reactivity of a Stable Zerovalent Ruthenium Aqua Complex
    Organometallics, 2002
    Co-Authors: Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Yasuyuki Ura, Hiroshi Miyai, Take-aki Mitsudo
    Abstract:

    A novel ruthenium(0) aqua complex, Ru(dimethyl fumarate)2(dppe)(H2O) (4), was synthesized via the reaction of Ru(η6-1,3,5-Cyclooctatriene)(dimethyl fumarate)2 (3) with dppe in 1,2-dichloroethane/water, which is a quite rare example of a stable and isolable ruthenium(0) aqua complex. The X-ray crystallography of 4 indicated that coordination of a water molecule to the ruthenium center was stabilized by two hydrogen bonds with the carbonyl oxygen atoms of dimethyl fumarate ligands.

  • Ruthenium-catalyzed intramolecular hydroamination of aminoalkynes
    Journal of Organometallic Chemistry, 2001
    Co-Authors: Teruyuki Kondo, Toshiaki Suzuki, Takumi Okada, Take-aki Mitsudo
    Abstract:

    Low-valent ruthenium complexes with a p-acidic ligand, such as Ru(h 6 -cot)(dmfm)2 [cot 1,3,5-Cyclooctatriene, dmfm dimethyl fumarate] and Ru3(CO)12, showed high catalytic activity for the intramolecular hydroamination of aminoalkynes. The reaction is highly regioselective, in which a nitrogen atom is selectively attached to an internal carbon of alkynes to give five-, six-, and seven-membered nitrogen heterocycles as well as indoles in good to high yields. © 2001 Elsevier Science B.V. All rights reserved.

  • reaction of ru 1 6 η Cyclooctatriene η2 dimethyl fumarate 2 with monodentate and bidentate phosphines a model reaction of catalytic dimerization of alkenes
    Organometallics, 2000
    Co-Authors: Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Kenji Wada, Take-aki Mitsudo
    Abstract:

    Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)2 1 reacts with monodentate tertiary phosphine ligands, PPh3, PMePh2, PMe2Ph, and PEt3, to give novel ruthenium(0) phosphine complexes, Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)(L) [L = PPh3 (2a), PMePh2 (2b), PMe2Ph (2c), and PEt3 (2d)], in high yields. The structures of the complexes 2b, 2c, and 2d were determined by X-ray analyses. The coordination geometry of the complexes around the central ruthenium atom is a highly distorted trigonal bipyramid, but the orientation of coordination of the Cyclooctatriene ligand differs from each other. Complexes 2a−d show dynamic behavior in solution involving the rotation of the Cyclooctatriene ligand around the axis, which lies between the ruthenium center and the center of the Cyclooctatriene ligand. Novel bidentate phosphine complexes, Ru(η2-dimethyl fumarate)(dppe)2 4 and 5 [dppe = 1,2-bis(diphenylphosphino)ethane] were prepared by the reaction of 1 with dppe in high yields. The structures of the complexes 4 a...

Masashi Shiotsuki - One of the best experts on this subject based on the ideXlab platform.

  • Ruthenium-catalyzed formal [4 + 2] cycloaddition of alkynes with alkenes: formation of cyclohexenedicarboxylates via isomerization of alkynes and successive Diels–Alder reaction
    Journal of Organometallic Chemistry, 2004
    Co-Authors: Masashi Shiotsuki, Teruyuki Kondo, Kenji Wada, Yasuyuki Ura, Takashi Ito, Take-aki Mitsudo
    Abstract:

    Abstract Formal [4 + 2] cycloaddition of alkynes with electron-deficient alkenes, which affords 3,6-dialkyl-4-cyclohexene-1,2-dicarboxylates, was achieved using Ru(η 6 -1,3,5-Cyclooctatriene)(η 2 -dimethyl fumarate) 2 as a catalyst. The reaction mechanism consists of two steps, isomerization of an alkyne to conjugated dienes and successive Diels–Alder reaction of the generated dienes with an electron-deficient alkene.

  • Synthesis of novel zerovalent ruthenium η6-arene complexes via direct displacement of a 1,3,5-Cyclooctatriene ligand by arenes
    Organometallics, 2003
    Co-Authors: Yasuyuki Ura, Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Kazuo Sadaoka, Take-aki Mitsudo
    Abstract:

    Novel zerovalent arene complexes bearing two dimethyl fumarate ligands, Ru(η6-arene)(dimethyl fumarate)2 (arene = benzene (2a), toluene (2b), p-xylene (2c), mesitylene (2d), hexamethylbenzene (2e), tert-butylbenzene (2f), anisole (2g), N,N-dimethylaniline (2h), biphenyl (2i), methyl benzoate (2j), naphthalene (2k)), were synthesized via the direct ligand exchange reaction of Ru(η6-cot)(dimethyl fumarate)2 (1; cot = 1,3,5-Cyclooctatriene) with arenes. The detailed structures of 2g,h were determined by X-ray crystallography, which revealed that the coordination geometry can be represented by a highly distorted trigonal bipyramid.

  • Synthesis, Structure, and Reactivity of a Stable Zerovalent Ruthenium Aqua Complex
    Organometallics, 2002
    Co-Authors: Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Yasuyuki Ura, Hiroshi Miyai, Take-aki Mitsudo
    Abstract:

    A novel ruthenium(0) aqua complex, Ru(dimethyl fumarate)2(dppe)(H2O) (4), was synthesized via the reaction of Ru(η6-1,3,5-Cyclooctatriene)(dimethyl fumarate)2 (3) with dppe in 1,2-dichloroethane/water, which is a quite rare example of a stable and isolable ruthenium(0) aqua complex. The X-ray crystallography of 4 indicated that coordination of a water molecule to the ruthenium center was stabilized by two hydrogen bonds with the carbonyl oxygen atoms of dimethyl fumarate ligands.

  • reaction of ru 1 6 η Cyclooctatriene η2 dimethyl fumarate 2 with monodentate and bidentate phosphines a model reaction of catalytic dimerization of alkenes
    Organometallics, 2000
    Co-Authors: Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Kenji Wada, Take-aki Mitsudo
    Abstract:

    Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)2 1 reacts with monodentate tertiary phosphine ligands, PPh3, PMePh2, PMe2Ph, and PEt3, to give novel ruthenium(0) phosphine complexes, Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)(L) [L = PPh3 (2a), PMePh2 (2b), PMe2Ph (2c), and PEt3 (2d)], in high yields. The structures of the complexes 2b, 2c, and 2d were determined by X-ray analyses. The coordination geometry of the complexes around the central ruthenium atom is a highly distorted trigonal bipyramid, but the orientation of coordination of the Cyclooctatriene ligand differs from each other. Complexes 2a−d show dynamic behavior in solution involving the rotation of the Cyclooctatriene ligand around the axis, which lies between the ruthenium center and the center of the Cyclooctatriene ligand. Novel bidentate phosphine complexes, Ru(η2-dimethyl fumarate)(dppe)2 4 and 5 [dppe = 1,2-bis(diphenylphosphino)ethane] were prepared by the reaction of 1 with dppe in high yields. The structures of the complexes 4 a...

  • Reaction of Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)2 with Monodentate and Bidentate Phosphines: A Model Reaction of Catalytic Dimerization of Alkenes
    Organometallics, 2000
    Co-Authors: Masashi Shiotsuki, Toshiaki Suzuki, Teruyuki Kondo, Kenji Wada, Take-aki Mitsudo
    Abstract:

    Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)2 1 reacts with monodentate tertiary phosphine ligands, PPh3, PMePh2, PMe2Ph, and PEt3, to give novel ruthenium(0) phosphine complexes, Ru(1−6-η-Cyclooctatriene)(η2-dimethyl fumarate)(L) [L = PPh3 (2a), PMePh2 (2b), PMe2Ph (2c), and PEt3 (2d)], in high yields. The structures of the complexes 2b, 2c, and 2d were determined by X-ray analyses. The coordination geometry of the complexes around the central ruthenium atom is a highly distorted trigonal bipyramid, but the orientation of coordination of the Cyclooctatriene ligand differs from each other. Complexes 2a−d show dynamic behavior in solution involving the rotation of the Cyclooctatriene ligand around the axis, which lies between the ruthenium center and the center of the Cyclooctatriene ligand. Novel bidentate phosphine complexes, Ru(η2-dimethyl fumarate)(dppe)2 4 and 5 [dppe = 1,2-bis(diphenylphosphino)ethane] were prepared by the reaction of 1 with dppe in high yields. The structures of the complexes 4 a...

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