Activation of arene carbon-hydrogen bonds. Highly regioselective, electrophilic aromatic metalation with rhodium(III) porphyrin and subsequent cleavage of carbon-rhodium bond

Aoyama, Yasuhiro; Yoshida, Tohru; Sakurai, Ken-ichi; Ogoshi, Hisanobu

doi:10.1021/om00132a030

Cited by 63 publications

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“…29 In this system, however, very high para selectivity is observed. This could be a result of the higher electrophilicity of the Pd(IV) center; C-H activations at Pt(IV) 30 and Rh(III) 31 give high para selectivity under kinetic conditions. 32 Figure 10.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of N-Fluorobenzenesulfonimide Promoted Diamination and Carboamination Reactions: Divergent Reactivity of a Pd(IV) Species

et al. 2009

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The mechanism of the Pd-catalyzed diamination and carboamination of alkenes promoted by N-fluorobenzenesulfonimide (NFBS) was investigated. Stereochemical labeling experiments established that the diamination reaction proceeds via overall syn addition of the two nitrogen groups, whereas carboamination is the result of an anti addition of arene and nitrogen to the alkene. The intermediate Pd-alkyl complex arising from aminopalladation was observed, and an X-ray crystal structure of its 2,2'-bipyridine (bipy) complex was obtained, revealing strong chelation of the amide protecting group to palladium. Aminopalladation was shown to be an anti-selective process in both the presence and the absence of added ligands, proceeding via external attack of the nitrogen on a Pd-coordinated alkene. The intermediate Pd-alkyl complex was converted to diamination product upon exposure to NFBS with inversion of configuration via oxidative addition followed by dissociation of the benzenesulfonimide anion and S(N)2 displacement of the Pd-C bond. Conversely, arylation of the Pd-alkyl complex proceeds via retention of stereochemistry, consistent with C-H activation of the arene at the Pd(IV) center. A small intermolecular isotope effect (k(H)/k(D) = 1.1) and a large intramolecular isotope effect (k(H)/k(D) = 4) were measured for this process, indicating that C-H activation occurs via a poorly selective product-determining coordination of the arene followed by a highly selective C-H activation. Competition between arenes reveals an unusual reactivity order of toluene > benzene > bromobenzene > anisole.

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Section: Resultsmentioning

confidence: 99%

Mechanism of N-Fluorobenzenesulfonimide Promoted Diamination and Carboamination Reactions: Divergent Reactivity of a Pd(IV) Species

et al. 2009

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“…This result is inconsistent with electrophilic C-H bond activation, where the ρ values have been determined in the cases of PtCl 6 2-and [(OEP)RhCl] (OEP = octaethylporphyrinato). [13,14] Scheme 5. 1 H NMR analysis revealed that the kinetic isotope effect is 5.4.…”

Section: Introductionmentioning

confidence: 99%

Carbon–Hydrogen Bond Activation of Arenes by a [Bis(oxazolinyl)phenyl]rhodium(III) Acetate Complex

Ito

Nishiyama

2007

Eur J Inorg Chem

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Thermolysis of the rhodium(III) complex [(dm‐Phebox‐dm)Rh(OAc)2(H2O)] [1; dm‐Phebox‐dm = 2,6‐bis(4,4‐dimethyloxazolinyl)phenyl] in various arenes results in the formation of the corresponding aryl complexes [(dm‐Phebox‐dm)Rh(Ar)(κ2‐OAc)] [Ar = C6H5 (2), 3,5‐Me2C6H3 (3), 3,4‐Me2C6H3 (4), C6H4Me (5), C6H4CF3 (6), C6H4OMe (7), C6H4COMe (8), C6H4Cl (9)]. The reaction of 1 with monosubstituted benzenes such as toluene, anisole, acetophenone, trifluorotoluene, and chlorobenzene produces a mixture of meta‐ and para‐activated complexes, the ratio of which depends on the substituents on the benzene ring. The relative rate of the reaction of 1 with monosubstituted benzenes C6H5X was determined to be: X = OMe (1.8) > COMe (1.6) > CF3 (1.2), Cl (1.2) > CH3 (1). The acetato ligand of 1 appears to be essential for C–H bond activation of arenes as no reaction of the RhIII complex [(dm‐Phebox‐dm)RhCl2(H2O)] is observed in chlorobenzene at 120 °C. The first‐order rate constants obtained by thermolysis of 1 in [D8]toluene at 97.1–116.5 °C yielded the following activation parameters: ΔH‡ = 22(2) kcal mol–1, ΔS‡ = –24(5) cal mol–1 K–1. The kinetic isotope effect for the C–H bond activation of toluene by 1 was determined to be kH/kD = 5.4 at 100 °C. These data suggest that the rate‐determining step involves the C–H bond cleavage with a rigid, cyclic transition structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…The apparent two-point/one-point selectivities (K 2pt /K 1pt ) also change from 55 through 95 to 10 3 . It is impressive on the other hand, to note that the term K 2pt /(K 1pt ) 2 remains nearly constant at 10. In terms of free energy, this corresponds to the difference between one two-point adduct and two one-point adducts; …”

Section: Award Accountsmentioning

confidence: 95%

“…We elucidated the complete details of this electrophilic aromatic metallation with Hammett-type substituent correlation. 2 We then switched to acetone, which readily gave the corresponding organometallic compound 6 presumably via enolization of the ketone with Rh III as an acidic promoter and a base (formally ClO 4 ¹ ) to abstract a proton (Scheme 1). The cationic Rh III is essential as a promoter, since the chlororhodium derivative 3 shows no activity at all.…”

Section: Hostguest Systems With Convergent Multiplementioning

confidence: 99%

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Structure and Function of Molecular Assembly. A Personal Reminiscence

Aoyama¹

2009

Bulletin of the Chemical Society of Japan

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In this account is described an outline of research the author has conducted over the last 35 years. Depending on the type of molecular assemblies dealt with, the whole work is divided into four parts, i.e., small hostguest systems in organic media, infinite solid systems, huge but finite nano systems in aqueous media, and manipulated biological systems. The essence of the hostguest systems (Section 2) is molecular recognition based on convergent multiple interactions involving OH£O hydrogen bonds, where sugar binding and detailed thermodynamic analysis of multipoint recognition may be taken as highlights. A couple of new fields arise from the hostguest chemistry by paradigm shift. One is in the direction of multiple interactions, from convergent to divergent. Section 3 thus concerns molecular alignment control in crystals using orthogonal aromatic triad and diad building blocks. Catalysis by microporous metallo-organic frameworks as organic zeolites is also described. The other shift in paradigm is in the media, from organic to aqueous, and also in the significance of sugar binding, from sugars as a guest to sugars as a probe. Section 4 is devoted to the highly adhesive (hydrogen bonding) nature of glycocluster compounds and their micelle-like aggregates, focusing on the formation of glycoviruses and glycoviral gene delivery. With DNA and RNA manipulation techniques in hand, we became interested in in-cell gene sensing and transcription monitoring. The latest activity in this area is shown in Section 5. The entire work is design-based. The author, who is soon retiring from Kyoto University, now has mixed feelings about this apparently natural approach, as briefly referred to in the Closing Remark (Section 6).

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Activation of arene carbon-hydrogen bonds. Highly regioselective, electrophilic aromatic metalation with rhodium(III) porphyrin and subsequent cleavage of carbon-rhodium bond

Cited by 63 publications

References 0 publications

Mechanism of N-Fluorobenzenesulfonimide Promoted Diamination and Carboamination Reactions: Divergent Reactivity of a Pd(IV) Species

Mechanism of N-Fluorobenzenesulfonimide Promoted Diamination and Carboamination Reactions: Divergent Reactivity of a Pd(IV) Species

Carbon–Hydrogen Bond Activation of Arenes by a [Bis(oxazolinyl)phenyl]rhodium(III) Acetate Complex

Structure and Function of Molecular Assembly. A Personal Reminiscence

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