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Hiroyuki Ishibashi - One of the best experts on this subject based on the ideXlab platform.
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Intramolecular Cycloaddition of O-tert-Butyldimethylsilyloximes in the Presence of BF3·OEt2
The Journal of organic chemistry, 2005Co-Authors: Osamu Tamura, Takahiro Mitsuya, Xin Huang, Yoshiyuki Tsutsumi, Sanae Hattori, Hiroyuki IshibashiAbstract:[reaction: see text] Intramolecular Cycloaddition of novel 1,3-dipoles, N-boranonitrones, was examined. Treatment of O-tert-butyldimethylsilyloximes 9-12 having olefin moieties with 2 equiv of BF3 x OEt2 generated N-boranonitrones, which underwent Intramolecular Cycloaddition to afford N-nonsubstituted cycloadducts 16 (and/or 18) after extractive workup. Despite the Lewis-acidic conditions, the olefin geometry of the substrates was retained in the cycloadducts in the present Cycloaddition. The electronic nature of the N-boranonitrones appeared to be electrophilic. In the case of substrate 11c, having an electron-donating methyl group at an internal position of the olefin moiety, the Cycloaddition gave the bridged cycloadduct 18b. The Cycloaddition proceeded at relatively low temperature, and the diastereoselectivity was high.
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Syntheses of (−)-Funebrine and (−)-Funebral, Using Sequential Transesterification and Intramolecular Cycloaddition of a Chiral Nitrone
The Journal of organic chemistry, 2004Co-Authors: Osamu Tamura, Nobutaka Iyama, Hiroyuki IshibashiAbstract:The first syntheses of (-)-funebrine [(-)-1] and (-)-funebral [(-)-2] are described. The syntheses feature sequential formation of nitrone VI from methyl glyoxylate (5) with oxime 6, transesterification of nitrone VI with (E)-crotyl alcohol (4), and Intramolecular Cycloaddition of the resulting nitrone VII bearing crotyl ester to afford cycloadduct 7 as a major product. The adduct 7 was readily elaborated to amino lactone (-)-3, the key synthetic intermediate of (-)-1 and (-)-2.
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BF3.OEt2-mediated Cycloaddition of O-tert-butyldimethylsilyloximes having olefin moieties: Intramolecular Cycloaddition of N-borano-nitrones.
Chemical communications (Cambridge England), 2002Co-Authors: Osamu Tamura, Takahiro Mitsuya, Hiroyuki IshibashiAbstract:Treatment of O-tert-butyldimethylsilyloximes having olefin moieties in the molecules with BF3.OEt2 results in efficient generation of N-borano-nitrones, which undergo Intramolecular Cycloaddition at room temperature to afford N-nonsubstituted cycloadducts after work-up.
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Tandem Transesterification and Intramolecular Cycloaddition of α-Methoxycarbonylnitrones with Chiral Acyclic Allyl Alcohols: Systematic Studies on the Factors Affecting Diastereofacial Selectivity of the Cycloaddition
The Journal of organic chemistry, 2001Co-Authors: Osamu Tamura, Hiroyuki Ishibashi, Naka Mita, Toshiyuki Okabe, Tatsuya Yamaguchi, Chieko Fukushima, Masayuki Yamashita, Yasuhiro Morita, Nobuyoshi Morita, Masanori SakamotoAbstract:Factors affecting the stereochemical course of the Intramolecular Cycloaddition of intermediary α-allyloxycarbonylnitrone resulting from transesterification of α-methoxycarbonylnitrones 1a−d with chiral allyl alcohols 5 or 6 were investigated systematically. It was found that the factors of diastereofacial selection are highly dependent on the geometries of the allyl alcohols. In the cases where primary or secondary chiral (Z)-allyl alcohols are used, A(1,3)-strain arising from the chiralities in the (Z)-nitrone transition states of the Intramolecular cycloaddtion is the most important factor. In contrast, in the case of the reaction using chiral nitrones 1c,d and (E)-allyl alcohols, steric interaction between the chiral N-substituent and the trans substituent of the olefin moiety in the intermediate is dominant. These aspects were applied to geometry-differentiated Cycloaddition using a mixture of (E)-5 and (Z)-5. As a typical example, treatment of bulky 1b with a 1:1 mixture of (E)-5 and (Z)-5 in the pr...
Min Shi - One of the best experts on this subject based on the ideXlab platform.
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Rh(I)-Catalyzed stereoselective Intramolecular Cycloaddition reactions of ene-vinylidenecyclopropanes for the construction of fused 6,5-bicyclic skeletons with a quaternary all-carbon stereocenter
Organic Chemistry Frontiers, 2019Co-Authors: Kang-hua Rui, Song Yang, Yin Wei, Min ShiAbstract:A cationic Rh(I) complex catalyzed Intramolecular Cycloaddition reaction of ene-vinylidenecyclopropanes to produce bicyclo[4.3.0] skeletons containing a quaternary all-carbon center at the ring juncture has been successfully established. The reaction could afford a range of desired bicyclic products in good yields with a broad substrate scope and good functional-group tolerance. The asymmetric variant of this Cycloaddition could also be achieved by using chiral bisphosphine ligands to give the desired products with high ee values. Furthermore, the exclusive production of endo- and exocyclic double bond products could be achieved when the substituent at the quaternary carbon center is a methyl group. The synthetic utility of the obtained products has been demonstrated by several transformations of the obtained bicyclic products. The reaction mechanism and product selectivity were studied by control experiments, and plausible reaction mechanisms have been proposed.
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thermal induced Intramolecular 2 2 Cycloaddition of allene acps
Organic and Biomolecular Chemistry, 2013Co-Authors: Kai Chen, Min Shi, Yin Wei, Run SunAbstract:A facile synthetic method for preparation of bicyclo[4.2.0] nitrogen heterocycles has been developed via a thermal induced Intramolecular [2 + 2] Cycloaddition reaction of allene-ACPs. The DFT calculations indicate that this Intramolecular Cycloaddition proceeds in a concerted manner and a strained small ring is essential.
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rhodium i catalyzed 3 2 Intramolecular Cycloaddition of alkylidenecyclopropane propargylic esters
Tetrahedron Letters, 2012Co-Authors: Di-han Zhang, Min ShiAbstract:An interesting rhodium(I)-catalyzed [3+2] Intramolecular Cycloaddition of alkylidenecyclopropanes 1 containing propargylic esters has been described in this context. A variety of bicyclo[3.3.0]octene derivatives were obtained in moderate to good yields under mild conditions. The alkylidenecyclopropane-enynes 2 could be also converted to the corresponding cycloadducts 3 in good yields.
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Rhodium(I)-catalyzed [3+2] Intramolecular Cycloaddition of alkylidenecyclopropane–propargylic esters
Tetrahedron Letters, 2012Co-Authors: Di-han Zhang, Min ShiAbstract:An interesting rhodium(I)-catalyzed [3+2] Intramolecular Cycloaddition of alkylidenecyclopropanes 1 containing propargylic esters has been described in this context. A variety of bicyclo[3.3.0]octene derivatives were obtained in moderate to good yields under mild conditions. The alkylidenecyclopropane-enynes 2 could be also converted to the corresponding cycloadducts 3 in good yields.
Osamu Tamura - One of the best experts on this subject based on the ideXlab platform.
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Intramolecular Cycloaddition of O-tert-Butyldimethylsilyloximes in the Presence of BF3·OEt2
The Journal of organic chemistry, 2005Co-Authors: Osamu Tamura, Takahiro Mitsuya, Xin Huang, Yoshiyuki Tsutsumi, Sanae Hattori, Hiroyuki IshibashiAbstract:[reaction: see text] Intramolecular Cycloaddition of novel 1,3-dipoles, N-boranonitrones, was examined. Treatment of O-tert-butyldimethylsilyloximes 9-12 having olefin moieties with 2 equiv of BF3 x OEt2 generated N-boranonitrones, which underwent Intramolecular Cycloaddition to afford N-nonsubstituted cycloadducts 16 (and/or 18) after extractive workup. Despite the Lewis-acidic conditions, the olefin geometry of the substrates was retained in the cycloadducts in the present Cycloaddition. The electronic nature of the N-boranonitrones appeared to be electrophilic. In the case of substrate 11c, having an electron-donating methyl group at an internal position of the olefin moiety, the Cycloaddition gave the bridged cycloadduct 18b. The Cycloaddition proceeded at relatively low temperature, and the diastereoselectivity was high.
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Syntheses of (−)-Funebrine and (−)-Funebral, Using Sequential Transesterification and Intramolecular Cycloaddition of a Chiral Nitrone
The Journal of organic chemistry, 2004Co-Authors: Osamu Tamura, Nobutaka Iyama, Hiroyuki IshibashiAbstract:The first syntheses of (-)-funebrine [(-)-1] and (-)-funebral [(-)-2] are described. The syntheses feature sequential formation of nitrone VI from methyl glyoxylate (5) with oxime 6, transesterification of nitrone VI with (E)-crotyl alcohol (4), and Intramolecular Cycloaddition of the resulting nitrone VII bearing crotyl ester to afford cycloadduct 7 as a major product. The adduct 7 was readily elaborated to amino lactone (-)-3, the key synthetic intermediate of (-)-1 and (-)-2.
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BF3.OEt2-mediated Cycloaddition of O-tert-butyldimethylsilyloximes having olefin moieties: Intramolecular Cycloaddition of N-borano-nitrones.
Chemical communications (Cambridge England), 2002Co-Authors: Osamu Tamura, Takahiro Mitsuya, Hiroyuki IshibashiAbstract:Treatment of O-tert-butyldimethylsilyloximes having olefin moieties in the molecules with BF3.OEt2 results in efficient generation of N-borano-nitrones, which undergo Intramolecular Cycloaddition at room temperature to afford N-nonsubstituted cycloadducts after work-up.
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Tandem Transesterification and Intramolecular Cycloaddition of α-Methoxycarbonylnitrones with Chiral Acyclic Allyl Alcohols: Systematic Studies on the Factors Affecting Diastereofacial Selectivity of the Cycloaddition
The Journal of organic chemistry, 2001Co-Authors: Osamu Tamura, Hiroyuki Ishibashi, Naka Mita, Toshiyuki Okabe, Tatsuya Yamaguchi, Chieko Fukushima, Masayuki Yamashita, Yasuhiro Morita, Nobuyoshi Morita, Masanori SakamotoAbstract:Factors affecting the stereochemical course of the Intramolecular Cycloaddition of intermediary α-allyloxycarbonylnitrone resulting from transesterification of α-methoxycarbonylnitrones 1a−d with chiral allyl alcohols 5 or 6 were investigated systematically. It was found that the factors of diastereofacial selection are highly dependent on the geometries of the allyl alcohols. In the cases where primary or secondary chiral (Z)-allyl alcohols are used, A(1,3)-strain arising from the chiralities in the (Z)-nitrone transition states of the Intramolecular cycloaddtion is the most important factor. In contrast, in the case of the reaction using chiral nitrones 1c,d and (E)-allyl alcohols, steric interaction between the chiral N-substituent and the trans substituent of the olefin moiety in the intermediate is dominant. These aspects were applied to geometry-differentiated Cycloaddition using a mixture of (E)-5 and (Z)-5. As a typical example, treatment of bulky 1b with a 1:1 mixture of (E)-5 and (Z)-5 in the pr...
Anthony C. Willis - One of the best experts on this subject based on the ideXlab platform.
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Intramolecular Cycloaddition Reactions of cis-1,2-Dihydrocatechol Derivatives Incorporating C3-Tethered Diazoketones, Nitrile Oxides, and Azides: Stereocontrolled Routes to Enantiomerically Pure Spiro[5.5]undecanes and Related Systems.
ChemInform, 2013Co-Authors: Tristan A. Reekie, Martin G. Banwell, Anthony C. WillisAbstract:A series of enantiomerically pure 1,2-dihydrocatechol derivatives (I), (VI), (XI), and (XIV) bearing diazoketone, nitrile oxide, or azide residues is prepared and their regio- and stereoselective Intramolecular Cycloaddition reactions are described.
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Intramolecular Cycloaddition Reactions of cis-1,2-Dihydrocatechol Derivatives Incorporating C3-Tethered Diazoketones, Nitrile Oxides, and Azides: Stereocontrolled Routes to Enantiomerically Pure Spiro[5.5]undecanes and Related Systems
The Journal of organic chemistry, 2013Co-Authors: Tristan A. Reekie, Martin G. Banwell, Anthony C. WillisAbstract:A series of enantiomerically pure cis-1,2-dihydrocatechol derivatives incorporating C3-tethered diazoketone, nitrile oxide, or azide residues has been prepared from the precursor iodide 7 using Negishi cross-coupling reactions. Such derivatives, including diazoketone 12, participate in regio- and stereo-selective Intramolecular Cycloaddition reactions to give adducts, for example, 15, that are readily elaborated to spiro[5.5]undecanes such as 18.
José L. Mascareñas - One of the best experts on this subject based on the ideXlab platform.
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ruthenium catalyzed 2 2 Intramolecular Cycloaddition of allenenes
ChemInform, 2011Co-Authors: Moisés Gulías, Fernando López, Alba Collado, Beatriz Trillo, Enrique Oñate, Miguel A. Esteruelas, José L. MascareñasAbstract:The previously unnoticed Ru complex activates the title reaction which proceeds under mild conditions and is fully diastereoselective.
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Ruthenium-catalyzed (2 + 2) Intramolecular Cycloaddition of allenenes.
Journal of the American Chemical Society, 2011Co-Authors: Moisés Gulías, Fernando López, Alba Collado, Beatriz Trillo, Enrique Oñate, Miguel A. Esteruelas, José L. MascareñasAbstract:We report a ruthenium-catalyzed (2 + 2) Intramolecular Cycloaddition of allenes and alkenes. We have found that the use of the ruthenium complex RuH2Cl2(PiPr3)2, which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicyclo[3.2.0]heptane skeletons featuring cyclobutane rings.
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ruthenium catalyzed 2 2 Intramolecular Cycloaddition of allenenes
Journal of the American Chemical Society, 2011Co-Authors: Moisés Gulías, Fernando López, Alba Collado, Beatriz Trillo, Enrique Oñate, Miguel A. Esteruelas, José L. MascareñasAbstract:We report a ruthenium-catalyzed (2 + 2) Intramolecular Cycloaddition of allenes and alkenes. We have found that the use of the ruthenium complex RuH2Cl2(PiPr3)2, which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicyclo[3.2.0]heptane skeletons featuring cyclobutane rings.
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Gold‐Catalyzed [4C+3C] Intramolecular Cycloaddition of Allenedienes: Synthetic Potential and Mechanistic Implications
Chemistry (Weinheim an der Bergstrasse Germany), 2009Co-Authors: Beatriz Trillo, Fernando López, Luis Castedo, Sergi Montserrat, Gregori Ujaque, Agustí Lledós, José L. MascareñasAbstract:Efficient at room temperature: The Au complex generated in situ from [(IPr)AuCl] and AgSbF(6) promotes the [4C+3C] Intramolecular Cycloaddition of allenes and dienes at room temperature, and in a particularly efficient and versatile manner. A DFT study on dimethylallenyl precursors agreed with the formation and Cycloaddition of a metal-allyl cation intermediate, and points to the 1,2-hydride shift as the key rate-limiting step.
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gold catalyzed 4c 3c Intramolecular Cycloaddition of allenedienes synthetic potential and mechanistic implications
Chemistry: A European Journal, 2009Co-Authors: Beatriz Trillo, Fernando López, Luis Castedo, Sergi Montserrat, Gregori Ujaque, Agustí Lledós, José L. MascareñasAbstract:Efficient at room temperature: The Au complex generated in situ from [(IPr)AuCl] and AgSbF(6) promotes the [4C+3C] Intramolecular Cycloaddition of allenes and dienes at room temperature, and in a particularly efficient and versatile manner. A DFT study on dimethylallenyl precursors agreed with the formation and Cycloaddition of a metal-allyl cation intermediate, and points to the 1,2-hydride shift as the key rate-limiting step.