Comparative Investigations of Cp*-Based Group 9 Metal-Catalyzed Direct C–H Amination of Benzamides

Figg, Travis M.; Park, Sehoon; Park, Juhyeon; Chang, Sukbok; Musaev, Djamaladdin G.

doi:10.1021/om5005868

Cited by 124 publications

(49 citation statements)

References 106 publications

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“…30,48,49 Therefore, we have also modelled this previously reported mechanism (pathway II). We found that the pathway II requires an activation barrier of 34.5 kcal/mol of energy (via TS5) to form the rhodacycle, d* and the amino product in a concerted process (k is the associated complex of rhodacycle and the product; ∆Grel = -56.7 kcal/mol).…”

Section: Resultsmentioning

confidence: 94%

A potential role of a substrate as a base for the deprotonation pathway in Rh-catalysed C–H amination of heteroarenes: DFT insights

et al. 2016

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Section: Resultsmentioning

confidence: 94%

A potential role of a substrate as a base for the deprotonation pathway in Rh-catalysed C–H amination of heteroarenes: DFT insights

et al. 2016

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“…Interestingly, not only The observed individual performance of rhodium and iridium catalysts in the C−H amination with organic azides motivated us to compare these catalytic systems. 35 A series of amination reactions of N-tert-butylbenzamide with several types of azides was analyzed using Cp*Rh(III) and Cp*Ir(III) catalysts. In general, the iridium catalyst displayed much higher performance toward sulfonyl, aryl, and acyl azides, while rhodium catalyzed amination exhibited superior efficiency with alkyl azides.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

Transition-Metal-Catalyzed C–N Bond Forming Reactions Using Organic Azides as the Nitrogen Source: A Journey for the Mild and Versatile C–H Amination

2015

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Owing to the prevalence of nitrogen-containing compounds in functional materials, natural products and important pharmaceutical agents, chemists have actively searched for the development of efficient and selective methodologies allowing for the facile construction of carbon-nitrogen bonds. While metal-catalyzed C-N cross-coupling reactions have been established as one of the most general protocols for C-N bond formation, these methods require starting materials equipped with functional groups such as (hetero)aryl halides or their equivalents, thus generating stoichiometric amounts of halide salts as byproducts. To address this aspect, a transition-metal-catalyzed direct C-H amination approach has emerged as a step- and atom-economical alternative to the conventional C-N cross-coupling reactions. However, despite the significant recent advances in metal-mediated direct C-H amination reactions, most available procedures need harsh conditions requiring stoichiometric external oxidants. In this context, we were curious to see whether a transition-metal-catalyzed mild C-H amination protocol could be achieved using organic azides as the amino source. We envisaged that a dual role of organic azides as an environmentally benign amino source and also as an internal oxidant via N-N2 bond cleavage would be key to develop efficient C-H amination reactions employing azides. An additional advantage of this approach was anticipated: that a sole byproduct is molecular nitrogen (N2) under the perspective catalytic conditions. This Account mainly describes our research efforts on the development of rhodium- and iridium-catalyzed direct C-H amination reactions with organic azides. Under our initially optimized Rh(III)-catalyzed amination conditions, not only sulfonyl azides but also aryl- and alkyl azides could be utilized as facile amino sources in reaction with various types of C(sp(2))-H bonds bearing such directing groups as pyridine, amide, or ketoxime. More recently, a new catalyst system using Ir(III) species was developed for the direct C-H amidation of arenes and alkenes with acyl azides under exceptionally mild conditions. As a natural extension, amidation of primary C(sp(3))-H bonds could also be realized on the basis of the superior activity of the Cp*Ir(III) catalyst. Mechanistic investigations revealed that a catalytic cycle is operated mainly in three stages: (i) chelation-assisted metallacycle formation via C-H bond cleavage; (ii) C-N bond formation through the in situ generation of a metal-nitrenoid intermediate followed by the insertion of an imido moiety to the metal carbon bond; (iii) product release via protodemetalation with the concomitant catalyst regeneration. In addition, this Account also summarizes the recent advances in the ruthenium- and cobalt-catalyzed amination reactions using organic azides, developed by our own and other groups. Comparative studies on the relative performance of those catalytic systems are briefly described.

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“…The direct C-H amination of N-tert-butylbenzamide with organic azides catalyzed by Gp 9 M(OAc) 2 Cp* species has been modeled by Chang, Musaev, and coworkers with M06(DCE) calculations (Figure 1.39) [94]. Experimentally, [MCl 2 Cp*] 2 precatalysts are employed along with an AgSbF 6 additive, and the latter is assumed to effect the necessary C-H activation (presumably via an EA mechanism, i.e., without any specific base assistance) to arrive at a [M(BA)Cp] + intermediate (where BA is an O-bound, C-H-activated N-tert-butylbenzamide ligand).…”

Section: Alkenylation and Aminationmentioning

confidence: 99%

Computational Studies of Heteroatom‐Assisted CH Activation at Ru, Rh, Ir, and Pd as a Basis for Heterocycle Synthesis and Derivatization

Carr¹,

Macgregor²,

McMullin³

2016

Transition Metal‐Catalyzed Heterocycle Synthesis via CH Activation

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IntroductionModern computational chemistry is a key tool by which insight into organometallic reaction mechanisms can be gained. The ability to characterize short-lived intermediates and transition states provides an ideal complement to experiment, where such information is often extremely difficult, if not impossible, to obtain. Recent years have seen great advances in understanding the mechanisms of C-H bond activation, and this area was the subject of several major reviews toward the end of the last decade [1,2]. More recently, the focus has shifted to how C-H activation can be integrated into catalytic cycles for useful organic transformations. The C-H bond activation event is itself mechanistically diverse, with oxidative addition (OA), σ-bond metathesis (SBM), and electrophilic activation (EA) all potentially available at late transition metal centers, depending on the metal, its oxidation state, and the coordination environment. C-H activation assisted by a heteroatom base (typically a carboxylate or carbonate) falls into the last of these categories and forms the focus of this chapter. More recently, computational studies of catalytic cycles for C-H activation and functionalization have become more common. These reveal the complexity of what are usually multiple-step processes, and calculations are particularly well placed to test different mechanistic possibilities. Such studies are most effectively pursued through a close interaction between experiment and computation, and increasingly this is allowing for a more quantitative assessment of computed reaction mechanisms.As well as progress in mechanistic understanding, the last 10 years have seen important developments in the computational methodologies available to model transition metal reactivity. While density functional theory (DFT) remains the core method of choice, the ability to model larger systems that more closely reflect experiment has highlighted the known shortcomings of DFT in describing dispersion interactions. These long-range, stabilizing interactions are individually weak, but their cumulative effect in large systems can be significant. Methods to incorporate this component include its separate calculation (e.g., Transition Metal-Catalyzed Heterocycle Synthesis via C-H Activation, First Edition. Edited by Xiao-Feng Wu.

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Comparative Investigations of Cp*-Based Group 9 Metal-Catalyzed Direct C–H Amination of Benzamides

Cited by 124 publications

References 106 publications

A potential role of a substrate as a base for the deprotonation pathway in Rh-catalysed C–H amination of heteroarenes: DFT insights

A potential role of a substrate as a base for the deprotonation pathway in Rh-catalysed C–H amination of heteroarenes: DFT insights

Transition-Metal-Catalyzed C–N Bond Forming Reactions Using Organic Azides as the Nitrogen Source: A Journey for the Mild and Versatile C–H Amination

Computational Studies of Heteroatom‐Assisted CH Activation at Ru, Rh, Ir, and Pd as a Basis for Heterocycle Synthesis and Derivatization

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