Retraction of “Chemoselective Reactions of (E)-1,3-Dienes: Cobalt-Mediated Isomerization to (Z)-1,3-Dienes and Reactions with Ethylene”
نویسندگان
چکیده
In the asymmetric hydrovinylation (HV) of an E/Z-mixture of a prototypical 1,3-diene with (S,S)-(DIOP)CoCl2 or (S,S)-(BDPP)CoCl2 catalyst in the presence of Me3Al, the (E)-isomer reacts significantly faster, leaving behind the Z-isomer intact at the end of the reaction. The presumed [LCo-H](+)-intermediate, especially when L is a large-bite angle ligand, similar to DIOP and BDPP, promote an unusual isomerization of (E/Z)-mixtures of 1,3-dienes to isomerically pure Z-isomers. A mechanism that involves an intramolecular hydride addition via an [η(4)-(diene)(LCo-H)](+) complex, followed by π-σ-π isomerization of the intermediate Co(allyl) species, is proposed for this reaction.
منابع مشابه
Chemoselective Reactions of (E)-1,3-Dienes: Cobalt-Mediated Isomerization to (Z)-1,3-Dienes and Reactions with Ethylene
GENERAL METHODS S4 SYNTHESIS OF SUBSTRATES S4-S6 Synthesis of (Z)and (E)-1-cyclohexyl-1,3-butadiene (8) Typical procedure for the synthesis of (Z)and (E)-1,3-dienes (Z)and (E)-1-Benzylbuta-1,3-diene (18) (Z)and (E)-1-(2-Furyl)-1,3-butadiene (21) (Z)and (E)-1-(4-Butyl-1-cyclohexyl)-1,3-butadiene (22) SYNTHESIS OF COBALT COMPLEXES S7 CHEMOSELECTIVE ASYMMETRIC HYDROVINYLATIONS S7 Asymmetric hydrov...
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In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl2 complexes {Cl2Co[P P]} and Me3Al or methylaluminoxane, acyclic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydrovinylation products. The regioselectivity (1,4or 1,2-addition) and the alkene configuration (Eor Z-) of the resulting product depend on the nature of the ligand and temperature at whic...
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In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl2 complexes {Cl2Co[P~P]} and Me3Al or methylaluminoxane, acyclic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydrovinylation products. The regioselectivity (1,4- or 1,2-addition) and the alkene configuration (E- or Z-) of the resulting product depend on the nature of the ligand and temperature at ...
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The stereospecific polymerization of conjugated dienes began in 1954 with the first catalysts obtained by combining TiCl4 or TiCl3 with aluminum-alkyls, i.e. the catalytic systems previously employed for ethylene and propylene polymerizations. Subsequently, many other catalytic systems were obtained and examined by a combination of transition metal or lanthanide compounds with appropriate alkyl...
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