The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Eric J Enholm - One of the best experts on this subject based on the ideXlab platform.
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synthesis of linear and angular triquinane skeletons by o Stannyl ketyl promoted fragmentation cyclization reactions of alpha keto cyclopropanes
Journal of Organic Chemistry, 1997Co-Authors: Eric J EnholmAbstract:Several investigations of rigid α-keto cyclopropane cleavage by O-Stannyl ketyls are summarized herein. Tricyclo[3.3.0.02,8]octan-3-one ring systems were treated with nBu3SnH, which produced different ring-cleavage products depending on the location and type of substituent present. An examination of both radical-stabilizing substituents and stereoelectronic factors was initiated to understand what factors bias bond cleavage in a configurationally restricted α-ketocyclopropane via O-Stannyl ketyls. A preference for cleavage of the cyclopropane bond with the best orbital overlap with the ketyl radical sp2-orbital even in the presence of radical stabilizing groups is indicated by these results. An O-Stannyl ketyl ring scission−cyclization resulted in the novel synthesis of either a linear or an angular triquinane skeleton depending on the length and location an alkene tether on the tricyclo[3.3.0.02,8]octan-3-one precursor.
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Construction of a linear triquinane skeleton by an O-Stannyl ketyl radical rearrangement
Chemical Communications, 1996Co-Authors: Eric J EnholmAbstract:An O-Stannyl ketyl ring scission–cyclization of a rigid tricyclo [3.3.0.02,8]octan-3-one ring system bearing an alkene tether results in the synthesis of a linear triquinane skeleton.
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Free radical reactions promoted by O-Stannyl ketyls 3. Tandem cyclizations
Tetrahedron Letters, 1992Co-Authors: Eric J Enholm, J. A. BurroffAbstract:Abstract Tandem free radical reactions promoted by O-Stannyl ketyls were examined which resulted in the formation of spiro- and fused-ring systems. Unactivated and activated alkenes with phenyl and ester functions easily afforded the desired five-membered rings.
Hiroyuki Matsuzaka - One of the best experts on this subject based on the ideXlab platform.
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iridium hydride mediated stannane fluorine and chlorine σ bond activation reversible switching between x type Stannyl and z type stannane ligands
Organometallics, 2017Co-Authors: Hajime Kameo, Yuki Baba, Shigeyoshi Sakaki, Didier Bourissou, Hiroshi Nakazawa, Hiroyuki MatsuzakaAbstract:Iridium(I) carbonyl hydride Ir(H)(CO)(PPh3)3 (1) cleaves the Sn–F and Sn–Cl bonds of four-coordinate stannanes {o-(Ph2P)C6H4}3Sn(X) (X = F (2a) and Cl(2b)) to afford the Stannyl complex [{o-(Ph2P)C6H4}3Sn]Ir(CO) (3) and HX (X = F and Cl) thanks to phosphine chelation. A plausible intermediate [{o-(Ph2P)C6H4}3(Cl)Sn]Ir(H)(CO) (6) featuring Z-type Ir → R3SnCl interaction was synthesized by the reaction of 3 with HCl. Compound 6 readily regenerated 3 upon treatment with Bronsted bases, enabling reversible switching between X-type Stannyl and Z-type stannane ligands. Density functional theory calculations suggest plausible pathways for Sn–F and Sn–Cl bond cleavage reactions and support the idea that the species bearing a Z-type Ir → R3SnX interactions (X = F and Cl) are intermediates for Sn–X bond cleavage.
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Iridium Hydride Mediated Stannane–Fluorine and −Chlorine σ-Bond Activation: Reversible Switching between X-Type Stannyl and Z-Type Stannane Ligands
Organometallics, 2017Co-Authors: Hajime Kameo, Yuki Baba, Shigeyoshi Sakaki, Didier Bourissou, Hiroshi Nakazawa, Hiroyuki MatsuzakaAbstract:Iridium(I) carbonyl hydride Ir(H)(CO)(PPh3)3 (1) cleaves the Sn–F and Sn–Cl bonds of four-coordinate stannanes {o-(Ph2P)C6H4}3Sn(X) (X = F (2a) and Cl(2b)) to afford the Stannyl complex [{o-(Ph2P)C6H4}3Sn]Ir(CO) (3) and HX (X = F and Cl) thanks to phosphine chelation. A plausible intermediate [{o-(Ph2P)C6H4}3(Cl)Sn]Ir(H)(CO) (6) featuring Z-type Ir → R3SnCl interaction was synthesized by the reaction of 3 with HCl. Compound 6 readily regenerated 3 upon treatment with Bronsted bases, enabling reversible switching between X-type Stannyl and Z-type stannane ligands. Density functional theory calculations suggest plausible pathways for Sn–F and Sn–Cl bond cleavage reactions and support the idea that the species bearing a Z-type Ir → R3SnX interactions (X = F and Cl) are intermediates for Sn–X bond cleavage.
Akio Baba - One of the best experts on this subject based on the ideXlab platform.
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michael addition of Stannyl ketone enolate to α β unsaturated esters catalyzed by tetrabutylammonium bromide and an ab initio theoretical study of the reaction course
Journal of the American Chemical Society, 2003Co-Authors: Makoto Yasuda, Kouji Chiba, Noriyuki Ohigashi, Yasuhiro Katoh, Akio BabaAbstract:Michael addition of Stannyl ketone enolates to α,β-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu4NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl4 or Bu4NF) failed to give the desired products. The bromide anion from Bu4NBr coordinates to the tin center in enolate to accelerate the conjugate addition where a five-coordinated tin species was generated. The coordination of the bromide anion significantly raises the HOMO level of tin enolate and enhances its nucleophilicity. The conjugate addition provides the intermediate Michael adduct, which has an ester enolate moiety, and the adduct immediately transforms to α-Stannyl γ-ketoester by keto−enol tautomerization. This step contributes to the stabilization of the product system and leads to a thermodynamically favorable reaction course. An ab initio calculation reveals that the activation energy in the reaction using the bromide anion is lower than that of th...
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highly regioselective addition of an ester enolate equivalent to α β unsaturated ketones selective formation of both isomers derived from 1 2 and 1 4 additions using α Stannyl ester with additives
Chemical Communications, 2000Co-Authors: Makoto Yasuda, Yozo Matsukawa, Keishi Okamoto, Toshifumi Sako, Noriko Kitahara, Akio BabaAbstract:The reaction of α-Stannyl ester with α,β-unsaturated ketones in the presence of stannous chloride (SnCl2) and chlorosilanes (Me3SiCl or Me2SiCl2) gave 1,2- and 1,4-addition products, respectively.
Asuncion Barbero - One of the best experts on this subject based on the ideXlab platform.
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addition of organometallic compounds to tin containing cyclic ketones remote stereocontrol induced by the Stannyl group
Journal of the American Chemical Society, 2003Co-Authors: Asuncion Barbero, Francisco J. Pulido, Juan A RinconAbstract:The addition of organometallic reagents to cyclic ketones bearing Stannyl groups at an appropriate distance to the carbonyl group occurs with a high level of stereocontrol, giving alcohols resulting from attack of the nucleophile syn to the tin center. This remarkable remote control is a consequence of the anchoring of the organometallic reagent by the tin and carbonyl groups. The degree of selectivity observed depends on the spatial distance between the carbonyl group and the tin center. (Z)-β-Stannylvinyl ketones (Sn/CO separation: 5 bonds) react with organolithium reagents, showing a high degree of stereocontrol. On the contrary, the analogous ketones with E stereochemistry do not show selectivity at all. In the case of β-Stannyl ketones (Sn/CO separation: 3 bonds), the long distance between the tin center and the carbonyl group does not favor selective addition except when allyllithium derivatives are used. A chelation-controlled pathway assisted by the three-carbon chain of the allyl anion, which c...
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Stannyl-cupration of acetylenes and the reaction of the intermediate cuprates with electrophiles as a synthesis of substituted vinylstannanes
Journal of The Chemical Society-perkin Transactions 1, 1993Co-Authors: Asuncion Barbero, Ian Fleming, Purificación Cuadrado, Ana M. González, Francisco J. Pulido, R. RubioAbstract:Stannyl-cupration of acetylenes followed by electrophilic attack with a variety of electrophiles gives E-vinylstannanes. These can be used either to form acetylenes, thus achieving overall the addition of an ethynyl group, or to form carbon–carbon bonds in Stille reactions.
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The Stannyl–cupration of acetylenes and the reaction of the intermediate cuprates with electrophiles as a synthesis of substituted vinylstannanes
Journal of The Chemical Society Chemical Communications, 1992Co-Authors: Asuncion Barbero, Ian Fleming, Purificación Cuadrado, Ana M. González, Francisco J. PulidoAbstract:Stannyl–cupration of acetylenes followed by electrophilic attack with a variety of electrophiles gives vinylstannanes.
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The synthesis of allylstannanes and, vinylstannanes by the Stannyl-cupration of allenes
Journal of The Chemical Society Chemical Communications, 1990Co-Authors: Asuncion Barbero, Ian Fleming, Purificación Cuadrado, Ana M. González, Francisco J. PulidoAbstract:Stannyl-cupration of allenes followed by electrophilic attack gives allyl- and vinylstannanes with a variety of substitution patterns; the regiochemistry of the reaction depends upon the temperature and the nature of the Stannyl-cuprate reagent.
Hajime Kameo - One of the best experts on this subject based on the ideXlab platform.
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iridium hydride mediated stannane fluorine and chlorine σ bond activation reversible switching between x type Stannyl and z type stannane ligands
Organometallics, 2017Co-Authors: Hajime Kameo, Yuki Baba, Shigeyoshi Sakaki, Didier Bourissou, Hiroshi Nakazawa, Hiroyuki MatsuzakaAbstract:Iridium(I) carbonyl hydride Ir(H)(CO)(PPh3)3 (1) cleaves the Sn–F and Sn–Cl bonds of four-coordinate stannanes {o-(Ph2P)C6H4}3Sn(X) (X = F (2a) and Cl(2b)) to afford the Stannyl complex [{o-(Ph2P)C6H4}3Sn]Ir(CO) (3) and HX (X = F and Cl) thanks to phosphine chelation. A plausible intermediate [{o-(Ph2P)C6H4}3(Cl)Sn]Ir(H)(CO) (6) featuring Z-type Ir → R3SnCl interaction was synthesized by the reaction of 3 with HCl. Compound 6 readily regenerated 3 upon treatment with Bronsted bases, enabling reversible switching between X-type Stannyl and Z-type stannane ligands. Density functional theory calculations suggest plausible pathways for Sn–F and Sn–Cl bond cleavage reactions and support the idea that the species bearing a Z-type Ir → R3SnX interactions (X = F and Cl) are intermediates for Sn–X bond cleavage.
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Iridium Hydride Mediated Stannane–Fluorine and −Chlorine σ-Bond Activation: Reversible Switching between X-Type Stannyl and Z-Type Stannane Ligands
Organometallics, 2017Co-Authors: Hajime Kameo, Yuki Baba, Shigeyoshi Sakaki, Didier Bourissou, Hiroshi Nakazawa, Hiroyuki MatsuzakaAbstract:Iridium(I) carbonyl hydride Ir(H)(CO)(PPh3)3 (1) cleaves the Sn–F and Sn–Cl bonds of four-coordinate stannanes {o-(Ph2P)C6H4}3Sn(X) (X = F (2a) and Cl(2b)) to afford the Stannyl complex [{o-(Ph2P)C6H4}3Sn]Ir(CO) (3) and HX (X = F and Cl) thanks to phosphine chelation. A plausible intermediate [{o-(Ph2P)C6H4}3(Cl)Sn]Ir(H)(CO) (6) featuring Z-type Ir → R3SnCl interaction was synthesized by the reaction of 3 with HCl. Compound 6 readily regenerated 3 upon treatment with Bronsted bases, enabling reversible switching between X-type Stannyl and Z-type stannane ligands. Density functional theory calculations suggest plausible pathways for Sn–F and Sn–Cl bond cleavage reactions and support the idea that the species bearing a Z-type Ir → R3SnX interactions (X = F and Cl) are intermediates for Sn–X bond cleavage.
