Rhodium(II)-catalyzed nitrene transfer with phenyliodonium ylides

Mueller, P.; Baud, Corine; Naegeli, Ivo

doi:10.1002/(sici)1099-1395(199808/09)11:8/9<597::aid-poc45>3.0.co;2-m

Cited by 62 publications

(6 citation statements)

References 37 publications

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“…4D) but does not alter the mass of [1•3] + . In addition to [5] + , an m/z corresponding to the bis-ligated species [9] + (m/z 1,617.7317) is also recorded (Fig. 3).…”

Section: S1c) Although the Intensity Of [7+na]supporting

confidence: 60%

“…+ is low, its appearance is consistent with the catalytic pathway that we and others have postulated for the C-H amination process (7)(8)(9). Many of the ionic species detected in this study have been proposed previously based on bulk solution mechanistic data.…”

Section: S1c) Although the Intensity Of [7+na]mentioning

confidence: 83%

“…This complex is suspected to be in equilibrium with 5 and is off the previously proposed catalytic path. Dissociation of [9] + yields [5] + in MS 2 spectra (Fig. S4D), supporting its assignment.…”

Section: S1c) Although the Intensity Of [7+na]mentioning

confidence: 99%

“…The Du Bois laboratory has developed an amination protocol that uses the catalyst bis [rhodium(α,α,α′,α′-tetramethyl-1,3-benzenedipropionic acid)], hereafter designated as Rh 2 (esp) 2 , to promote both intra-and intermolecular oxidation reactions (1,2). Indirect evidence has implicated a reactive Rh-nitrene intermediate that oxidizes saturated C-H bonds through a concerted asynchronous two-electron insertion event (6)(7)(8)(9)(10). Studies of the reaction mechanism suggest the generation of a one-electron oxidized form of the catalyst, [Rh 2 (esp) 2 …”

mentioning

confidence: 99%

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Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Perry

Cahill

Roizen

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C-H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C-H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes.mass spectrometry | transient intermediates | C-H oxidation | catalysis C atalytic methods for selective C-H oxidation rely on the exquisite choreography of a series of ligand substitution and redox events (1, 2) and in some instances, the controlled generation of a hyperreactive electrophile (3-5). The Du Bois laboratory has developed an amination protocol that uses the catalyst bis [rhodium(α,α,α′,α′-tetramethyl-1,3-benzenedipropionic acid)], hereafter designated as Rh 2 (esp) 2 , to promote both intra-and intermolecular oxidation reactions (1, 2). Indirect evidence has implicated a reactive Rh-nitrene intermediate that oxidizes saturated C-H bonds through a concerted asynchronous two-electron insertion event (6-10). Studies of the reaction mechanism suggest the generation of a one-electron oxidized form of the catalyst, [Rh 2 (esp) 2 ]+ , which appears to result from reaction of the nitrenoid oxidant (4, 5, 11). The fast rates of the on-and off-path steps in this catalytic process and the transient nature of the reactive Rh-nitrene have confounded direct detection of many of the proposed reaction intermediates.A preponderance of experimental and theoretical data (7-10, 12, 13) supports the mechanism for Rh-catalyzed C-H amination depicted in Fig. 1. Sulfamate 2 and iodine oxidant 3 condense to form iminoiodinane 4 (14, 15). The iminoiodinane is a ligand for Rh 2 (esp) 2 , which react to generate [Rh 2 (esp) 2 ]•PhINSO 2 OR 5; subsequent loss of iodobenzene (PhI) furnishes nitrenoid 6. Oxidation of adamantane by 6 gives the sulfonamide product 7 and regenerates the dirhodium catalyst 1. The structures of intermediates 5 and 6 were postulated through analogy to carbenoid intermediates in reactions of dirhodium catalysts with diazo compounds, and to the best of our knowledge, have not been observed spectroscopically (6-10, 12, 13). In our experience, the oxidation of substrate by Rh-nitrene 6 seems to correlate with competitive formation of a mixed-valent (Rh 2+ /Rh 3+ ) dimer 8 that visibly colors the reaction solution red. Previous studies show that this red species is generated when Rh 2 (esp) 2 1, sulfamate 2, and oxidant 3 are mixed in solution (e.g., 0.3 mM 1 in chlorobenzene) (4,5,11). In this report, we provide direct...

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“…4D) but does not alter the mass of [1•3] + . In addition to [5] + , an m/z corresponding to the bis-ligated species [9] + (m/z 1,617.7317) is also recorded (Fig. 3).…”

Section: S1c) Although the Intensity Of [7+na]supporting

confidence: 60%

Section: S1c) Although the Intensity Of [7+na]mentioning

confidence: 83%

Section: S1c) Although the Intensity Of [7+na]mentioning

confidence: 99%

mentioning

confidence: 99%

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Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Perry

Cahill

Roizen

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…In the C–H amination pathway, coordination of the iminoiodinane to the dirhodium catalyst facilitates the extrusion of PhI and generates the active nitrenoid. 20,25,27 C–H bond oxidation proceeds through a direct insertion event to afford the heterocyclic product and to regenerate the catalyst. Kinetic data from NMR experiments show no variance in product formation rates within the first 100 s of oxidant addition across 0.5–5.0 mol % catalyst loadings, implying that the initial reaction rate is limited by the production of ROSO 2 N=IPh.…”

Section: Mechanistic Investigationsmentioning

confidence: 99%

Metal-Catalyzed Nitrogen-Atom Transfer Methods for the Oxidation of Aliphatic C–H Bonds

2012

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For more than a century, chemists have endeavored to discover and develop reaction processes that enable the selective oxidation of hydrocarbons. In the 1970s, Abramovitch and Yamada described the synthesis and electrophilic reactivity of sulfonyliminoiodinanes (RSO2N=IPh), demonstrating the utility of this new class of reagents to function as nitrene equivalents. Subsequent investigations by Breslow, Mansuy, and Müller would show such oxidants to be competent for alkene and saturated hydrocarbon functionalization when combined with transition metal salts or metal complexes, namely those of Mn, Fe, and Rh. Here, we trace our own studies to develop N-atom transfer technologies for C–H and π-bond oxidation. This Account discusses advances in both intra- and intermolecular amination processes mediated by dirhodium and diruthenium complexes, as well as the mechanistic foundations of catalyst reactivity and arrest. Explicit reference is given to questions that remain unanswered and to problem areas that are rich for discovery. A fundamental advance in amination technology has been the recognition that iminoiodinane oxidants can be generated in situ in the presence of a metal catalyst that elicits subsequent N-atom transfer. Under these conditions, both dirhodium and diruthenium lantern complexes function as competent catalysts for C–H bond oxidation with a range of nitrogen sources (e.g., carbamates, sulfamates, sulfamides, etc.), many of which will not form isolable iminoiodinane equivalents. Practical synthetic methods and applications thereof have evolved in parallel with inquiries into the operative reaction mechanism(s). For the intramolecular dirhodium-catalyzed process, the body of experimental and computational data is consistent with a concerted asynchronous C–H insertion pathway, analogous to the consensus mechanism for Rh-carbene transfer. Other studies reveal that the bridging tetracarboxylate ligand groups, which shroud the dirhodium core, are labile to exchange under standard reaction conditions. This information has led to the generation of chelating dicarboxylate dinuclear rhodium complexes, exemplified by Rh2(esp)2. The performance of this catalyst system is unmatched by other dirhodium complexes in both intra- and intermolecular C–H amination reactions. Tetra-bridged, mixed-valent diruthenium complexes function as effective promoters of sulfamate ester oxidative cyclization. These catalysts can be crafted with ligand sets other than carboxylates and are more resistant to oxidation than their dirhodium counterparts. A range of experimental and computational mechanistic data amassed with the tetra-2-oxypyridinate diruthenium chloride complex, [Ru2(hp)4Cl], has established the insertion event as a stepwise pathway involving a discrete radical intermediate. These data contrast dirhodium-catalyzed C–H amination and offer a cogent model for understanding the divergent chemoselectivity trends observed between the two catalyst types. This work constitutes an important step toward the ultimate goal of achiev...

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Asymmetric Oxidations and Related Reactions

Matsumoto

Katsuki

2010

Catalytic Asymmetric Synthesis

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GENERAL INTRODUCTIONOxidation is a fundamental technology for converting bulk chemicals into valuable materials and is also a useful tool for sophisticated functionalization of organic molecules. Thus, intensive research efforts have been devoted to the development of selective and practical oxidation methods, and a wide variety of chiral metal -based catalysts and organocatalysts have been developed for catalytic asymmetric oxidation reactions in industry and academia in the last half -century [1] . In contrast to the rapid improvement in stereoselectivity, the enhancement of atom economy [2] falls behind. While atom effi ciency (especially active oxygen content in oxygenation reactions) of stoichiometric oxidants is a factor that should be considered, most of the catalytic asymmetric oxidations still use conventional stoichiometric oxidants of low atomeffi ciency such as peracids, alkyl hydroperoxides, hypervalent iodine reagents, hypochlorite, and N -oxide compounds (Table 11.1 ). The use of such oxidants causes the formation of large amounts of undesirable waste. From the viewpoint of ecological sustainability, oxidation with a higher atom -effi cient, safe, abundant, and preferably inexpensive oxidant is favorable. Considering the requirements, molecular oxygen and hydrogen peroxide are the oxidants of choice [3] . Molecular oxygen offers a large advantage because it is abundant in air and is inexpensive. Aerobic oxidation that directly uses ambient air as an oxidant is similar to respiration in living organisms. Hydrogen peroxide is also recognized as a green oxidant. It is almost as equally atomeffi cient as molecular oxygen, and the by -product is safe and clean water. Moreover, its aqueous solution (typically 30 -35%) is inexpensive and easy to handle. Consequently, the development of catalytic asymmetric oxidations with molecular oxygen Catalytic Asymmetric Synthesis, Third Edition, Edited by Iwao Ojima

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Rhodium(II)-catalyzed nitrene transfer with phenyliodonium ylides

Cited by 62 publications

References 37 publications

Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Metal-Catalyzed Nitrogen-Atom Transfer Methods for the Oxidation of Aliphatic C–H Bonds

Asymmetric Oxidations and Related Reactions

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