Remarkably High Reactivity of Pd(OAc)<sub>2</sub>/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes

Emmert, Marion H.; Cook, Amanda K.; Xie, Yushu J.; Sanford, Melanie S.

doi:10.1002/anie.201103327

Cited by 167 publications

(85 citation statements)

References 48 publications

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“…20 Similarly, Sanford reported a palladium-catalyzed acetoxylation that gives C–O bond formation predominantly meta to the electron-withdrawing trifluoromethyl group ( o:m:p = 1:78:21). 21 In contrast, by enhancing the electrophilicity of the arene through η 6 -coordination, our protocol has the potential to complement these selectivities, with hydroxylation occurring at the position of least electron density.…”

Section: Resultsmentioning

confidence: 99%

Selective Aromatic C–H Hydroxylation Enabled by η⁶-Coordination to Iridium(III)

2015

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We report an aromatic C–H hydroxylation protocol in which the arene is activated through η6-coordination to an iridium(III) complex. η6-Coordination of the arene increases its electrophilicity and allows for high positional selectivity of hydroxylation at the site of least electron density. Through investigation of intermediate η5-cyclohexadienyl adducts and arene exchange reactions, we evaluate incorporation of arene π-activation into a catalytic cycle for C–H functionalization.

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Section: Resultsmentioning

confidence: 99%

Selective Aromatic C–H Hydroxylation Enabled by η⁶-Coordination to Iridium(III)

2015

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“…As a consequence of rising levels of chloride ions, the ratio [2a]/[2b] continuously soared upon styrene conversion, thus boosting the overall reactivity. 59 Therefore, the presence of pyridine amplified the reactivity of Pd IV both by imposing a positive charge on the metal in LPd IV Cl 3 (py) + and by enabling a chloride-rich counteranion environment. In comparison, a recent literature report on Pd II /Pd IV -catalyzed aromatic C−H acetoxylations in the presence of PhI(OAc) 2 / Pd(OAc) 2 /py highlighted dramatic "pyridine effects" on reaction rates and yields as well (presumably through the action of (py)Pd(OAc) 2 ).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Pyridine-Assisted Chlorinations and Oxidations by Palladium(IV)

McCall

Kraft

2012

Organometallics

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The reactivity of the bis-NHC complex LPd IV Cl 4 (L = κ 2 -[R-NHCCH 2 NHC-R] with R = C 14 H 29 ) in chlorinations and oxidations of organic substrates was considerably increased in the presence of pyridine. For alkene chlorinations, this effect was due to the in situ formation of highly reactive LPd IV Cl 3 (py) + , which was able to transfer Cl + to the CC bond in a ligand-mediated process (devoid of π complexation), which did not require py dissociation. The enhanced reactivity in the presence of pyridine also extended to the oxidation of secondary and benzylic alcohols under mild conditions in a reaction where py served as a base, broadening the known scope of reactivity for Pd IV complexes. LPd IV Cl 3 (py) + could be formed from Cl − /py exchange or from the oxidation of LPd II Cl(py) + by Cl 2 . Taking advantage of the enhanced reactivities that pyridine coordination imparted on both Pd II and Pd IV complexes allowed for the catalytic chlorination of styrene with LPd IV Cl 4 as a sacrificial oxidant, thereby establishing the principal feasibility of Pd II /Pd IV catalyses that obviates Pd II activations of the substrate.

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“…DMAP may act as a ligand for the palladium catalyst and an external base. [16] Based on these observations and former studies by other groups, [5b,c,f] we proposed the following mechanistic pathway to account for the chemoselectivity and stereochemistry of the cascade cooperative catalytic reaction (Scheme 4). Figure 1.…”

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confidence: 95%

“…The products were obtained in moderate to high yields with constantly remarkable enantioselectivity ( Table 2, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In the case of less reactive aliphatic enals, good enantioselectivities were also obtained, albeit with lower yields (Table 2, entries [15][16][17]. The absolute configuration of the products was determined by X-ray analysis.…”

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confidence: 99%