Chemoselective reactions of (E)-1,3-dienes: cobalt-mediated isomerization to (Z)-1,3-dienes and reactions with ethylene.
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.
Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
Yam N
YN
Timsina
Souvagya
S
Biswas
T V
TV
RajanBabu
D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D005030:Ethylenes / Q000737:chemistry*; D007536:Isomerism; D011090:Polyenes / Q000737:chemistry*
D005030:Ethylenes; D011090:Polyenes; D003035:Cobalt; C036216:ethylene