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Litao Shen - One of the best experts on this subject based on the ideXlab platform.
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nhc catalyzed enantioselective 2 2 and 2 2 2 cycloadditions of ketenes with isothiocyanates
ChemInform, 2012Co-Authors: Xiaona Wang, Litao ShenAbstract:The [2 + 2]-cycloaddition reaction of the aromatic isothiocyanate (III) with ketenes proceeds at room temperature with formation of 4-thioxo-2-azetidinones.
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nhc catalyzed enantioselective 2 2 and 2 2 2 cycloadditions of ketenes with isothiocyanates
Organic Letters, 2011Co-Authors: Xiaona Wang, Litao ShenAbstract:The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at −40 °C favors the [2 + 2 + 2] cycloaddition.
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enantioselective 2 2 2 cycloaddition of ketenes and carbon disulfide catalyzed by n heterocyclic carbenes
Chemical Communications, 2011Co-Authors: Xiaona Wang, Litao ShenAbstract:The chiral N-heterocyclic carbene-catalyzed [2+2+2] cycloaddition of ketenes and carbon disulfide was realized to give the cycloadduct of 1,3-oxathian-6-ones in good yields with excellent enantioselectivities.
James A Ibers - One of the best experts on this subject based on the ideXlab platform.
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syntheses and characterization of the metal maleonitrilediselenolates k 2 2 2 cryptand 2 m se2c2 cn 2 2 m ni pd pt and ni dmf 5 cl 2 ni se2c2 cn 2 2
Inorganic Chemistry, 2001Co-Authors: Craig C Mclauchlan, Scott D Robowski, James A IbersAbstract:Reaction of KNH2, K2Se, Se, [2.2.2]-cryptand, and a metal source yields the metal bis(maleonitrilediselenolates) [K([2.2.2]-cryptand)]2[M(Se2C2(CN)2)2] (M = Ni, 1; Pd, 2, Pt, 3). These compounds are isostructural and crystallize with four formula units in the monoclinic space group P21/c in cells at T = 153 K with parameters (a (A), b (A), c (A), β (deg), V (A3)) of 12.220(1), 15.860(2), 15.306(1), 107.64(2), 2827(1) for 1; 12.291(1), 15.669(1), 15.548(1), 108.55(1), 2839(1) for 2; and 12.292(3), 15.671(3), 15.569(3), 108.59(3), 2842(1) for 3. The cation of 1 has been substituted to yield [Ni(dmf)5Cl]2[Ni(Se2C2(CN)2)2] (4). [Ni(dmf)5Cl]2[Ni(Se2C2(CN)2)2] (4) crystallizes with one molecule in the triclinic space group P1 in a cell with parameters (T = 153 K) of a = 8.842(2) A, b = 13.161(3) A, c = 13.831(3) A, α = 110.08(3)°, β = 95.23(3)°, γ = 93.72(3)°, V = 1484(1) A3. The electronic absorption and infrared spectra are characteristic of metal maleonitrilediselenolates. Cyclic voltammetry shows that the ...
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facile syntheses and structures of new metal maleonitrilediselenolates k 2 2 2 cryptand 3 ag se2c2 cn 2 se6 k 2 2 2 cryptand 2 ni se2c2 cn 2 2 and ni dppp se2c2 cn 2
Inorganic Chemistry, 2000Co-Authors: Craig C Mclauchlan, James A IbersAbstract:Facile syntheses of [K([2.2.2]-cryptand)]3Ag(Se2C2(CN)2)(Se6)] (1) and [K([2.2.2]-cryptand)]2[Ni(Se2C2(CN)2)2] (2) are achieved through reaction of polyselenides with KNH2, [2.2.2]-cryptand, and AgBF4 or Ni(dppp)Cl2 in acetonitrile. The syntheses of 2 and Ni(dppp)(Se2C2(CN)2) (3) may be achieved by reaction of 1 with NiCl2 or Ni(dppp)Cl2 in dmf. These compounds represent the first easily prepared metal−maleonitrilediselenolate derivatives.
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syntheses and crystal structures of k 2 2 2 cryptand 2 m o m o 2 si ch 3 2 2 gese 2 and k 2 2 2 cryptand 2 sb 2 se 6
Inorganic Chemistry, 1997Co-Authors: Donna M Smith, Changwoo Park, James A IbersAbstract:[K(2.2.2-cryptand)]2[(μ-O){μ-O2Si(CH3)2}2(GeSe)2] (1) forms from the adventitious reaction of silicone grease with the residue (dissolved in CH3CN) from the reduction of GeSe2 by K in NH3(l) in the presence of 2.2.2-cryptand. Reduction of SbSe under similar conditions leads to the isolation of [K(2.2.2-cryptand)]2[Sb2Se6] (2).
Ken Tanaka - One of the best experts on this subject based on the ideXlab platform.
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rhodium catalyzed asymmetric 2 2 2 cycloaddition of unsymmetrical α ω diynes with acenaphthylene
Journal of Organic Chemistry, 2018Co-Authors: Yukimasa Aida, Yu Shibata, Ken TanakaAbstract:It has been established that a cationic rhodium(I)/(R)-BINAP complex catalyzes the asymmetric [2 + 2 + 2] cycloaddition of unsymmetrical α,ω-diynes with acenaphthylene at room temperature to give the corresponding chiral multicyclic compounds with high yields and ee values. Interestingly, enantioselectivity highly depended on the structures of α,ω-diynes used. The structural requirements of α,ω-diynes for high enantioselectivity were opposite to those in our previously reported cationic rhodium(I)/(R)-Difluorphos complex-catalyzed asymmetric [2 + 2 + 2] cycloaddition of α,ω-diynes with indene.
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Enantioselective Helicene Synthesis by Rhodium-Catalyzed [2+2+2] Cycloadditions
Bulletin of the Chemical Society of Japan, 2015Co-Authors: Ken Tanaka, Yuki Kimura, Koichi MurayamaAbstract:The highly enantioselective synthesis of functionalized helicenes and helicene-like molecules have been achieved via rhodium-catalyzed [2+2+2] cycloaddition reactions. The rhodium-catalyzed enantio...
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enantioselective synthesis of 9 and 11 helicene like molecules double intramolecular 2 2 2 cycloaddition
Angewandte Chemie, 2014Co-Authors: Yuki Kimura, Ken Tanaka, Keiichi Noguchi, Naohiro Fukawa, Yuta MiyauchiAbstract:The enantioselective synthesis of completely ortho-fused [9]- and [11]helicene-like molecules has been achieved through a rhodium-mediated, intramolecular, double [2+2+2] cycloaddition of phenol- or 2-naphthol-linked hexaynes. Crystal structures and photophysical properties of these [9]- and [11]helicene-like molecules have also been disclosed.
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asymmetric synthesis of axially chiral biaryl diphosphine ligands by rhodium catalyzed enantioselective intramolecular double 2 2 2 cycloaddition
ChemInform, 2011Co-Authors: Fumiya Mori, Naohiro Fukawa, Keiichi Noguchi, Ken TanakaAbstract:The novel catalyst CDP is applied in Rh-catalyzed asymmetric hydrogenation and [2 + 2 + 2]-cycloaddition reactions.
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asymmetric synthesis of axially chiral biaryl diphosphine ligands by rhodium catalyzed enantioselective intramolecular double 2 2 2 cycloaddition
Organic Letters, 2011Co-Authors: Fumiya Mori, Naohiro Fukawa, Keiichi Noguchi, Ken TanakaAbstract:The concise synthesis of axially chiral biaryl diphosphine ligands by the rhodium-catalyzed intramolecular [2 + 2 + 2] cycloaddition of hexayne diphosphine oxides has been achieved. These new chiral diphosphine ligands could be employed as a ligand for the rhodium-catalyzed asymmetric catalyses.
Xiaona Wang - One of the best experts on this subject based on the ideXlab platform.
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nhc catalyzed enantioselective 2 2 and 2 2 2 cycloadditions of ketenes with isothiocyanates
ChemInform, 2012Co-Authors: Xiaona Wang, Litao ShenAbstract:The [2 + 2]-cycloaddition reaction of the aromatic isothiocyanate (III) with ketenes proceeds at room temperature with formation of 4-thioxo-2-azetidinones.
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nhc catalyzed enantioselective 2 2 and 2 2 2 cycloadditions of ketenes with isothiocyanates
Organic Letters, 2011Co-Authors: Xiaona Wang, Litao ShenAbstract:The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at −40 °C favors the [2 + 2 + 2] cycloaddition.
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enantioselective 2 2 2 cycloaddition of ketenes and carbon disulfide catalyzed by n heterocyclic carbenes
Chemical Communications, 2011Co-Authors: Xiaona Wang, Litao ShenAbstract:The chiral N-heterocyclic carbene-catalyzed [2+2+2] cycloaddition of ketenes and carbon disulfide was realized to give the cycloadduct of 1,3-oxathian-6-ones in good yields with excellent enantioselectivities.
Iwao Ojima - One of the best experts on this subject based on the ideXlab platform.
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Data_Sheet_1_Construction of Fused Tropone Systems Through Intramolecular Rh(I)-Catalyzed Carbonylative [2+2+2+1] Cycloadditon of Triynes.PDF
2018Co-Authors: Yu-han G. Teng, Chih-wei Chien, Wen-hua Chiou, Tadashi Honda, Iwao OjimaAbstract:“Tropone” is a non-benzenoid aromatic skeleton that can be found in a variety of natural products. This cyclohepta-2,4,6-trien-1-one skeleton appears simple, but there have been no straightforward ways to construct this molecular architecture. It is conceivable that this molecule can be constructed via a higher order cycloaddition of three acetylene units and CO, but such process was not known until we have discovered that the carbonylative [2+2+2+1] cycloaddition of triynes can take place in the presence of a Rh complex catalyst and CO. However, this highly challenging process is naturally accompanied by ordinary [2+2+2] cyclotrimization products, i.e., benzenes, as side products. A mechanistic study led to two competing processes wherein the critical CO insertion occurs either to a rhodacyclopentadiene intermediate (Path A) or a rhodacycloheptatriene intermediate (Path B). The DFT analysis of those two pathways disclosed that the Path A should be the one that yields the carbonylative [2+2+2+1] cycloaddition products, i.e., fused tricyclic tropones. A further substrate design, inspired by colchicine structure, led to the almost exclusive formation of a fused tetracyclic tropone from a triyne bearing 1,2-disubstituted benzene moiety in a single step and excellent yield.
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Construction of Fused Tropone Systems Through Intramolecular Rh(I)-Catalyzed Carbonylative [2+2+2+1] Cycloadditon of Triynes
'Frontiers Media SA', 2018Co-Authors: Yu-han G. Teng, Chih-wei Chien, Wen-hua Chiou, Tadashi Honda, Iwao OjimaAbstract:“Tropone” is a non-benzenoid aromatic skeleton that can be found in a variety of natural products. This cyclohepta-2,4,6-trien-1-one skeleton appears simple, but there have been no straightforward ways to construct this molecular architecture. It is conceivable that this molecule can be constructed via a higher order cycloaddition of three acetylene units and CO, but such process was not known until we have discovered that the carbonylative [2+2+2+1] cycloaddition of triynes can take place in the presence of a Rh complex catalyst and CO. However, this highly challenging process is naturally accompanied by ordinary [2+2+2] cyclotrimization products, i.e., benzenes, as side products. A mechanistic study led to two competing processes wherein the critical CO insertion occurs either to a rhodacyclopentadiene intermediate (Path A) or a rhodacycloheptatriene intermediate (Path B). The DFT analysis of those two pathways disclosed that the Path A should be the one that yields the carbonylative [2+2+2+1] cycloaddition products, i.e., fused tricyclic tropones. A further substrate design, inspired by colchicine structure, led to the almost exclusive formation of a fused tetracyclic tropone from a triyne bearing 1,2-disubstituted benzene moiety in a single step and excellent yield
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Data_Sheet_2_Construction of Fused Tropone Systems Through Intramolecular Rh(I)-Catalyzed Carbonylative [2+2+2+1] Cycloadditon of Triynes.zip
2018Co-Authors: Yu-han G. Teng, Chih-wei Chien, Wen-hua Chiou, Tadashi Honda, Iwao OjimaAbstract:“Tropone” is a non-benzenoid aromatic skeleton that can be found in a variety of natural products. This cyclohepta-2,4,6-trien-1-one skeleton appears simple, but there have been no straightforward ways to construct this molecular architecture. It is conceivable that this molecule can be constructed via a higher order cycloaddition of three acetylene units and CO, but such process was not known until we have discovered that the carbonylative [2+2+2+1] cycloaddition of triynes can take place in the presence of a Rh complex catalyst and CO. However, this highly challenging process is naturally accompanied by ordinary [2+2+2] cyclotrimization products, i.e., benzenes, as side products. A mechanistic study led to two competing processes wherein the critical CO insertion occurs either to a rhodacyclopentadiene intermediate (Path A) or a rhodacycloheptatriene intermediate (Path B). The DFT analysis of those two pathways disclosed that the Path A should be the one that yields the carbonylative [2+2+2+1] cycloaddition products, i.e., fused tricyclic tropones. A further substrate design, inspired by colchicine structure, led to the almost exclusive formation of a fused tetracyclic tropone from a triyne bearing 1,2-disubstituted benzene moiety in a single step and excellent yield.
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silicon initiated carbonylative carbotricyclization and 2 2 2 1 cycloaddition of enediynes catalyzed by rhodium complexes
ChemInform, 2006Co-Authors: Bibia Bennacer, Masaki Fujiwara, Seungyub Lee, Iwao OjimaAbstract:The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilane catalyzed by Rh(acac)(CO)2 at ambient temperature and pressure of CO gives the corresponding fused 5-7-5 tricyclic products, 5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatom congeners, in excellent yields through a unique silicon-initiated cascade carbonylative carbotricyclization (CO-SiCaT) process. It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process. The characteristics of these two tricyclization processes and the fundamental differences in their reaction mechanisms are discussed. This novel higher-order cycloaddition reaction has also been successfully applied to the tricyclization of undeca-5,10-diyn-1-als, affording the corresponding 5-7-5 fused-ring products bearing a seven-membered lactone moiety. Related [2+2+2] tricyclizations of enediyne and diynal substrates are also discussed. These newly discovered reactions can construct multiple bonds all at once, converting linear starting materials to polycyclic compounds in a single step. Thus, these new processes provide innovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural and unnatural products.
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novel 2 2 2 1 cycloaddition of enediynes catalyzed by rhodium complexes
Organic Letters, 2004Co-Authors: Bibia Bennacer, And Masaki Fujiwara, Iwao OjimaAbstract:The first Rh-catalyzed intramolecular [2 + 2 + 2 + 1] cycloaddition reaction of enediynes and CO is reported. This novel higher order cycloaddition process gives the corresponding 5-7-5 ring systems in high yield and selectivity. This process is another significant addition to the arsenal of cycloaddition-based synthetic methods, which provide powerful tools for rapid and efficient construction of complex polycyclic systems.
