Isolation and identification of the pre-catalyst in iron-catalyzed direct arylation of pyrrole with phenylboronic acid

Brewer, Samantha M.; Palacios, Philip M.; Johnston, Hannah M.; Pierce, Brad S.; Green, Kayla N.

doi:10.1016/j.ica.2018.03.036

Cited by 13 publications

(34 citation statements)

References 110 publications

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“…The pyridine ring is responsible for the large deviation from linearity of the axial N (2)À Fe(1)À N(4) bond angle that is comparable to the values found in the literature for complexes containing analogous cyclic chelators. [21][22] Other structural parameters, such as FeÀ N bond distances, are similar to those reported for related systems. [21,23] The equatorial Fe(1)À N(1) (pyridinic nitrogen) bond is the shortest and thus the strongest metal-ligand bond, although all FeÀ N bond lengths are longer than 2.0 Å, typical of high-spin Fe(III)-complexes.…”

Section: Resultssupporting

confidence: 81%

“…[21][22] Other structural parameters, such as FeÀ N bond distances, are similar to those reported for related systems. [21,23] The equatorial Fe(1)À N(1) (pyridinic nitrogen) bond is the shortest and thus the strongest metal-ligand bond, although all FeÀ N bond lengths are longer than 2.0 Å, typical of high-spin Fe(III)-complexes. [24] Iron-catalysed alkene oxidations.…”

Section: Resultssupporting

confidence: 81%

“…Differently from figure 2a, the intensity of the low field feature decreased on decreasing T. EPR spectra of complex 6 b (see Figure 2b) shows absorption phenomena at low field and in the 3000-4000 G zone, with several differences in respect to the previous sample. [21] Summarizing, in 6 a · 2H 2 O both low (S = 1/2) and high (S = 5/2) spin Fe 3 + species are present. Their positions do not change on cooling, while their intensities increase and the g = 4.32 component sharpen (ΔH pp � 85 Gauss).…”

Section: Resultsmentioning

confidence: 94%

“…Brewer et al observed almost identical spectra in Fe(III) coordination compounds and attributed the absorption phenomena to a dominant transition arising from m s = � 1/2 doublet of a Fe 3 + S = 5/2 spin state with nearly axial symmetry coupled to a component originated from the m s = � 3/2 doublet in the same spin/charge state. [21] Summarizing, in 6 a · 2H 2 O both low (S = 1/2) and high (S = 5/2) spin Fe 3 + species are present. Lowering T, the intensities related to the S = 5/2 state grow up suggesting that it should be the ground electronic state of iron.…”

Section: Resultsmentioning

confidence: 94%

“…The coordination sphere consist of four N-donors from the tetraazamacrocycle, which adopts the expected cis-folded configuration, and two cis chloride ions. [21,23] The equatorial Fe(1)À N(1) (pyridinic nitrogen) bond is the shortest and thus the strongest metal-ligand bond, although all FeÀ N bond lengths are longer than 2.0 Å, typical of high-spin Fe(III)-complexes. [21][22] Other structural parameters, such as FeÀ N bond distances, are similar to those reported for related systems.…”

Section: Resultsmentioning

confidence: 99%

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Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine‐Containing Ligand)] Complexes

et al. 2019

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A highly reactive and selective catalytic system comprising Fe (III) and macrocyclic pyridine-containing ligands (Pc-L) for alkene oxidation by using hydrogen peroxide is reported herein. Four new stable iron(III) complexes have been isolated and characterized. Importantly, depending on the anion of the iron(III) metal complex employed as catalyst, a completely reversed selectivity was observed. When X = OTf, a selective dihydroxylation reaction took place. On the other hand, employing X = Cl resulted in the epoxide as the major product.The reaction proved to be quite general, tolerating aromatic and aliphatic alkenes as well as internal or terminal double bonds and both epoxides and diol products were obtained in good yields with good to excellent selectivities (up to 93 % isolated yield and d.r. = 99 : 1). The catalytic system proved its robustness by performing several catalytic cycles, without observing catalyst deactivation. The use of acetone as a solvent and hydrogen peroxide as terminal oxidant renders this catalytic system appealing.

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Section: Resultssupporting

confidence: 81%

Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine‐Containing Ligand)] Complexes

et al. 2019

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Catalytic Selective Oxidation of Primary and Secondary Alcohols Using Nonheme [Iron(III)(Pyridine‐Containing Ligand)] Complexes

et al. 2020

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The selective oxidation of different primary and secondary alcohols to carbonyl compounds by hydrogen peroxide was found to be catalyzed in conversion ranging from good to excellent by an iron(III) complex of a pyridine‐containing macrocyclic ligand (Pc‐L), without the need of any additive. The choice of the counteranion (Cl, Br, OTf) appeared to be of fundamental importance and the best results in terms of selectivity (up to 99 %) and conversion (up to 98 %) were obtained using the well‐characterized [Fe(III)(Br)2(Pc‐L)]Br complex, 4c. Magnetic moments in solid‐state, also confirmed in solution ([D6]DMSO) by Evans NMR method, were calculated and point out to an iron metal center in the high spin state of 5/2. The crystal structure shows that the iron(III) center is coordinated by the four nitrogen atoms of the macrocycle and two bromide anions to form a distorted octahedral coordination environment. The catalytic oxidation of benzyl alcohol in acetonitrile was found occurring with better conversions and selectivities than in other solvents. The reaction proved to be quite general, tolerating aromatic and aliphatic alcohols, although very low yields were obtained for terminal aliphatic alcohols. Preliminary mechanistic studies are in agreement with a catalytic cycle promoted by a high‐spin iron complex.

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Recent Advances in Functionalization of Pyrroles and their Translational Potential

Hunjan

Panday

Gupta

et al. 2021

The Chemical Record

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Among the known aromatic nitrogen heterocycles, pyrrole represents a privileged aromatic heterocycle ranging its occurrence in the key component of “pigments of life” to biologically active natural products to active pharmaceuticals. Pyrrole being an electron‐rich heteroaromatic compound, its predominant functionalization is legendary to aromatic electrophilic substitution reactions. Although a few excellent reviews on the functionalization of pyrroles including the reports by Baltazzi in 1963, Casiraghi and Rassu in 1995, and Banwell in 2006 are available, they are fragmentary and over fifteen years old, and do not cover the modern aspects of catalysis. A review covering a comprehensive package of direct functionalization on pyrroles via catalytic and non‐catalytic methods including their translational potential is described. Subsequent to statutory yet concise introduction, the classical functionalization on pyrroles using Lewis acids largely following an ionic mechanism is discussed. The subsequent discussion follows the various metal‐catalyzed C−H functionalization on pyrroles, which are otherwise difficult to implement by Lewis acids. A major emphasize is given on the radical based pyrrole functionalization under metal‐free oxidative conditions, which is otherwise poorly highlighted in the literature. Towards the end, the current development of pyrrole functionalization under photocatalyzed and electrochemical conditions is appended. Only a selected examples of substrates and important mechanisms are discussed for different methods highlighting their scopes and limitations. The aromatic nucleophillic substitution on pyrroles (being an electron‐rich heterocycle) happened to be the subject of recent investigations, which has also been covered accentuating their underlying conceptual development. Despite great achievements over the past several years in these areas, many challenges and problems are yet to be solved, which are all discussed in summary and outlook.

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Isolation and identification of the pre-catalyst in iron-catalyzed direct arylation of pyrrole with phenylboronic acid

Cited by 13 publications

References 110 publications

Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine‐Containing Ligand)] Complexes

Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine‐Containing Ligand)] Complexes

Catalytic Selective Oxidation of Primary and Secondary Alcohols Using Nonheme [Iron(III)(Pyridine‐Containing Ligand)] Complexes

Recent Advances in Functionalization of Pyrroles and their Translational Potential

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