2010
DOI: 10.1021/ja108809u
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Regioselectivity-Switchable Hydroarylation of Styrenes

Abstract: Cobalt-phosphine and cobalt-carbene catalysts have been developed for the hydroarylation of styrenes via chelation-assisted C-H bond activation, to afford branched and linear addition products, respectively, in a highly regioselective fashion. Deuterium-labeling experiments suggested a mechanism involving reversible C-H bond cleavage and olefin insertion steps and reductive elimination as the rate- and regioselectivity-determining step.

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Cited by 251 publications
(110 citation statements)
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“…The first branch-selective processes of this type were reported in 2011 by Yoshikai and Gao, who demonstrated efficient 2-pyridyl-directed hydroarylation of styrenes using a PCy 3 -ligated Co(0)-catalyst, which was generated in situ by Grignard-mediated reduction of Co(II) (Scheme 3). 12 The process tolerates substitution at the 3-and 4-positions of the arene and functional groups such as aryl ethers, aryl-fluorides, and anilines can be accommodated. Substitution at the arene 2-position is not tolerated, presumably because this causes the pyridyl directing group to twist away from the plane of the arene such that directed insertion of the Co-catalyst is prevented.…”
Section: Directed Branch Selective Murai-type Alkene Hydroarylationsmentioning
confidence: 99%
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“…The first branch-selective processes of this type were reported in 2011 by Yoshikai and Gao, who demonstrated efficient 2-pyridyl-directed hydroarylation of styrenes using a PCy 3 -ligated Co(0)-catalyst, which was generated in situ by Grignard-mediated reduction of Co(II) (Scheme 3). 12 The process tolerates substitution at the 3-and 4-positions of the arene and functional groups such as aryl ethers, aryl-fluorides, and anilines can be accommodated. Substitution at the arene 2-position is not tolerated, presumably because this causes the pyridyl directing group to twist away from the plane of the arene such that directed insertion of the Co-catalyst is prevented.…”
Section: Directed Branch Selective Murai-type Alkene Hydroarylationsmentioning
confidence: 99%
“…A related IMesligated Co-catalyst promoted highly linear-selective alkene hydroarylations on the same range of substrates. 12 Computational studies by Fu and co-workers suggest that the steric effects of PCy 3 vs. IMes play a key role in switching from branch-to linear-selectivity. 13 For the former, secondary coordination of the Co-center to the aryl moiety of the styrenic component likely facilitates branch-selectivity at the stage of alkene hydrometalation.…”
Section: Directed Branch Selective Murai-type Alkene Hydroarylationsmentioning
confidence: 99%
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“…29 This was interesting because typical ruthenium and rhodium catalysts are known to show linear selectivity in the same or related transformations. 13 To our further surprise, we observed a near complete switch of the regioselectivity by using an N-heterocyclic carbene (NHC) ligand, IMes, instead of PCy 3 .…”
Section: Hydroarylation Of Alkynes and Alkenesmentioning
confidence: 99%
“…20 In contrast to related reactions using ruthenium and rhodium phosphine catalysts, 21 a cobalt phosphine catalyst generated from CoBr 2 , PCy 3 , and Me 3 SiCH 2 MgCl was found to promote the addition of 2 phenylpyridine to styrene in a branched manner with high regioselectivity (Scheme 8). 22 We were further surprised to nd that the use of an N heterocyclic carbene ligand (IMes) and tBuCH 2 MgBr instead of PCy 3 and Me 3 SiCH 2 MgCl, respectively, led to a near complete reversal of the regioselectivity. While this regiodivergent hydroarylation was achieved for a reasonable variety of 2 arylpyridines and Scheme 6.…”
Section: Cobalt Catalyzed Directed Hydroarylation Of Styrenesmentioning
confidence: 99%