Conformationally Restricted Arene Intermediates in the Intermolecular Heck Arylation of Vinylarenes

Hii, King Kuok; Claridge, Timothy D. W.; Giernoth, Ralf; Brown, John M.

doi:10.1002/adsc.200404072

Cited by 11 publications

(22 citation statements)

References 55 publications

(13 reference statements)

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“…Further studies 12 described the complete mechanism for alkyne hydrogenation when the phosphine ligands are bcope and t bucope [where t bucope is (C 8 H 14 )PC 6 H 4 CH 2 P( t Bu) 2 ]. The nature of the Scheme 1 key alkyl resting state was confirmed as a cationic g 3 -palladium(II) benzyl complex, in agreement with the related studies of Brown et al 13 In these PHIP studies, cationic palladium monohydride species of the type [Pd(LL )(L )(H)] + (where L = solvent or pyridine) were proven to provide access to the catalytic cycle with additional intermediates, including analogous vinyl cations, also being detected and shown to play an active role in catalysis. These experimental results proved to be in good agreement with those presented in a recent theoretical (DFT) study.…”

Section: Introductionsupporting

confidence: 88%

Section: Hydrogenation Of Diphenylacetylenementioning

confidence: 99%

“…Reactions of the bis-triflate complexes 1a-1e with a fifty-fold excess of diphenylacetylene-d 13 C satellites. In the species, cis-and trans-PhCH= 13 CHPh-d 10 , that give rise to these signals, the two alkenic protons are magnetically inequivalent because of the 13 C label. This confirms that hydrogenation of the triple bond of diphenylacetylene to yield cis-and trans-stilbene proceeds in such a manner as to enable two protons from a single p-H 2 molecule to be placed in the same reaction product.…”

Section: Hydrogenation Of Diphenylacetylenementioning

confidence: 99%

“…A series of 1 H- 13 C HMQC experiments, using 13 C≡C enriched diphenylacetylene-d 10 were then completed. These experiments confirmed that the 1 H resonance of 2a, which appeared at d 4.38 was connected to a 13 C signal at 64.2 (dd, J CP = 46.0 and 10.0 Hz).…”

Section: Reactions Of Pd(dcpe)(otf) 2 (1a) With P-h 2 and Diphenylace...mentioning

confidence: 99%

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Palladium catalysed alkyne hydrogenation and oligomerisation: a parahydrogen based NMR investigation

et al. 2008

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The role phosphine ligands play in the palladium(ii)-bis-phosphine-hydride cation catalysed hydrogenation of diphenylacetylene is explored through a PHIP (parahydrogen induced polarization) NMR study. The precursors Pd(LL')(OTf)(2) (1a-e) [LL' = dcpe (PCy(2)CH(2)CH(2)PCy(2)), dppe, dppm, dppp, cppe (PCy(2)CH(2)CH(2)PPh(2))] are used. Alkyl palladium intermediates of the type [Pd(LL')(CHPhCH(2)Ph)](OTf) ( and ) are detected and demonstrated to play an active role in hydrogenation catalysis. Magnetization transfer experiments reveal chemical exchange from the alpha-H of the alkyl ligand of (LL' = dcpe) and linkage isomer ' (LL' = cppe) into trans-stilbene on the NMR timescale. Activation parameters (DeltaH( not equal) and DeltaS( not equal)) for this transformation have been determined. These experiments, coupled with GC/MS data, indicate that the catalytic activity is greater in methanol, where it follows the order: dcpe > cppe > dppp > dppe > dppm, than in CD(2)Cl(2). All five of the phosphine systems described are less active than those based on bcope [where bcope is (C(8)H(14))PCH(2)-CH(2)P(C(8)H(14))] and (t)bucope [where (t)bucope is (C(8)H(14))PC(6)H(4)CH(2)P((t)Bu)(2)]. cis, cis-1,2,3,4-Tetraphenyl-buta-1,3-diene is detected as a minor reaction product with Pd(LL')(PhCH-CHPh-CPh=CHPh)(+) (4) also being shown to play a role in the alkyne dimerisation step.

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Section: Introductionsupporting

confidence: 88%

Section: Hydrogenation Of Diphenylacetylenementioning

confidence: 99%

Section: Hydrogenation Of Diphenylacetylenementioning

confidence: 99%

Section: Reactions Of Pd(dcpe)(otf) 2 (1a) With P-h 2 and Diphenylace...mentioning

confidence: 99%

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Palladium catalysed alkyne hydrogenation and oligomerisation: a parahydrogen based NMR investigation

et al. 2008

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“…• C, σ -ArCH 2 CH(Ar )-Pd(THF)(dppp) + complexes are stabilized by interaction of the Pd II centre with the adjacent Ar group, which restricts the C C internal rotation [51]. + which reacts with styrene in the absence of a base (Scheme 1.30a ).…”

Section: Complexation/insertion Of the Alkene-regioselectivitymentioning

confidence: 99%

Mechanisms of the Mizoroki–Heck Reaction

Jutand

2009

The Mizoroki–Heck Reaction

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Rate and Mechanism of the Reaction of Alkenes with Aryl Palladium Complexes Ligated by a Bidentate P,P Ligand in Heck Reactions

Amatore¹,

Godin²,

Jutand³

et al. 2007

Chemistry A European J

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The regioselectivity of the Heck reaction is supposed to be highly affected by the electronic properties of the alkene and the ionic or neutral character of the aryl palladium(II) complexes involved in the reaction with alkenes. In Heck reactions performed in dmf, [Pd(dppp){dppp(O)}Ph](+) (dppp=1,2-bis(diphenylphosphino)propane) is generated in the oxidative addition of PhI with [Pd(0)(dppp)(OAc)](-) formed in situ from Pd(OAc)(2) associated to two equivalents of dppp. [Pd(dppp){dppp(O)}Ph](+) is not very reactive with alkenes (styrene or methyl acrylate); however, it reacts with iodide ions (released in the catalytic reactions) to give [Pd(dppp)IPh] and with acetate ions (used as base) to give [Pd(dppp)(OAc)Ph]. [Pd(dppp)(OAc)Ph] reacts with styrene and methyl acrylate exclusively by an ionic mechanism, that is, via the cationic complex [Pd(dppp)(dmf)Ph](+) formed by dissociation of the acetate ion. The reaction of [Pd(dppp)IPh] is more complex and substrate dependent. It reacts with styrene exclusively by the ionic mechanism via [Pd(dppp)(dmf)Ph](+). [Pd(dppp)IPh] (neutral mechanism) and [Pd(dppp)(dmf)Ph](+) (ionic mechanism) react in parallel with methyl acrylate. [Pd(dppp)(dmf)Ph](+) is more reactive than [Pd(dppp)IPh] but is always generated at lower concentration.

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Conformationally Restricted Arene Intermediates in the Intermolecular Heck Arylation of Vinylarenes

Cited by 11 publications

References 55 publications

Palladium catalysed alkyne hydrogenation and oligomerisation: a parahydrogen based NMR investigation

Palladium catalysed alkyne hydrogenation and oligomerisation: a parahydrogen based NMR investigation

Mechanisms of the Mizoroki–Heck Reaction

Rate and Mechanism of the Reaction of Alkenes with Aryl Palladium Complexes Ligated by a Bidentate P,P Ligand in Heck Reactions

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