Mechanism of the chromium-catalyzed epoxidation of olefins. Role of oxochromium(V) cations

Samsel, E. G.; Srinivasan, K.; Kochi, Jay K.

doi:10.1021/ja00311a064

Cited by 399 publications

(225 citation statements)

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“…Norbornene oxide was obtained in greater yield than cis-cyclooctene oxide. Therefore, norbornene was a better trap for the hypervalent metal-oxo species in agreement with the findings of Samsel et al (16) and Groves et al (17). From the use of initial slopes of the first-order formation of epoxide vs. time the "initial rate" for norbornene oxide and cis-cyclooctene oxide formation were identical.…”

supporting

confidence: 89%

Observations and comments on the mechanism of epoxidation of alkenes by manganese(III) porphyrins with hypochlorite.

Lee

Nakagaki

Palaniappan

et al. 1988

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

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The kinetics of olefin epoxidation in a methylene chloride/water biphase containing a phase-transfer agent with hypochlorite as oxygen transfer reagent and manganese(E) tetraphenylporphyrin, catalysts has been reinvestigated. The results do not support the accumulation of an intermediate composed of an alkene and a hypervalent metaloxo porphyrin. Second-order rate constants for oxygen transfer from hypochlorite to the manganese porphyrin, comproportionation of the hypervalent manganese-oxo porphyrin with manganese(lI) porphyrin, and olerm epoxidation by the hypervalent manganese-oxo porphyrin were obtained from experiments in a wet organic monophase.In the reaction of a metal(III) porphyrin [(P)M"'(X)] with species OY (Eq. 1), where X is an anion and Y: is a good leaving group, the oxygen atom is transferred to the metalloporphyrin (1, 2). The generated hypervalent metal-oxo porphyrin species epoxidizes (Eq. 2) alkenes (3, 4).[1][(P)(X)Mn+2O] + alkene -* (P)Mn(X) + epoxide [2] In search of an inexpensive epoxidizing system, Meunier and associates (5) RESULTS AND DISCUSSION The following studies are reported: (i) determination of the steady-state concentration of the putative metallaoxetane intermediate by computer simulation of reported kinetic data using the reaction steps of Scheme I, which were proposed by for both iron(III) and manganese (III) porphyrins; (it) reinvestigation of the kinetics of epoxidation The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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supporting

confidence: 89%

Observations and comments on the mechanism of epoxidation of alkenes by manganese(III) porphyrins with hypochlorite.

Lee

Nakagaki

Palaniappan

et al. 1988

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

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“…While the chromium oxo complexes are often isolable, [137] the manganese oxo complexes are not (at room temperature only stable (L)Mn V = O species with other types of ligands L are known). [138,139] Nevertheless compounds such as 27 are now the accepted reactive intermediates in the catalytic Jacobsen-Katsuki epoxidation [135,140] having been identified as such by a series of techniques.…”

Section: Epoxidation Catalystsmentioning

confidence: 99%

The Role of Radicals in Metal‐Assisted Oxygenation Reactions

Limberg

2003

Angew Chem Int Ed

185

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The oxo-functionalization of organic substrates with the aid of metal oxo moieties is of fundamental importance not only in nature but also in academic and industrial research. Nevertheless the corresponding reaction mechanisms remain among the most enigmatic in chemistry and few of them are understood in detail. Recent research efforts have resulted in significantly improved information: in the cases of many oxygenation reactions evidence has been provided for the occurrence radical intermediates, even though the high selectivity observed suggests to a different mechanism. Examples stem from various areas of chemistry and include processes involving molecular metal oxo complexes, gas-phase and matrix-isolated species, metalloenzymes, and solid-state oxide surfaces. This review treats this seemingly wide variety of systems with the aim of providing an overview of common reactivity patterns and principles, as well as open problems.

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“…Replacement of C8-and C8'-phenyl groups of 5 with the more bulky 4-tbutylphenyl group constitutes a more effective design of the catalyst (7,13,14) 813)).…”

Section: Design Of Optically Active Mn-salen Catalystmentioning

confidence: 99%

Mn-Salen Catalyzed Asymmetric Oxidation of Simple Olefins and Sulfides.

Katsuki

1995

J. Syn. Org. Chem., Jpn.

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Among the several Mn-salen type catalysts studied, a rationally designed Mnsalen catalyst (14) was found to be the most effective for asymmetric epoxidation of simple olefins, especially cis-disubstituted and trisubstituted olefins conjugated with aryl, alkenyl and alkynyl groups. The mechanism of asymmetrc-inducition of this reaction has been well rationalized by the proposal that olefins approach oxo-metal from the side-on to give a metallaoxetane intermediate, wherein steric and electronic repulsions between the salen ligand and the olefinic substituent dictate the orientation of the incoming olefins and, the intermediate is transformed into epoxides via a radical intermediate. Asymmetric oxidation of sulfides was also found to be effectively catalyzed by Mn-salen catalyst (21).

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Mechanism of the chromium-catalyzed epoxidation of olefins. Role of oxochromium(V) cations

Cited by 399 publications

References 1 publication

Observations and comments on the mechanism of epoxidation of alkenes by manganese(III) porphyrins with hypochlorite.

Observations and comments on the mechanism of epoxidation of alkenes by manganese(III) porphyrins with hypochlorite.

The Role of Radicals in Metal‐Assisted Oxygenation Reactions

Mn-Salen Catalyzed Asymmetric Oxidation of Simple Olefins and Sulfides.

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