Rate constants for the bimolecular self‐reaction of cyano‐substituted alkyl radicals in solution

Korth, Hans‐Gert; Lommes, P.; Sicking, Willi; Sustmann, Reiner

doi:10.1002/kin.550150306

Cited by 38 publications

(15 citation statements)

References 29 publications

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“…Succinonitrile has been detected in small amounts under these conditions, but this is clearly a minor process 12a. Actually, the steady‐state value of Φ red (SS) in neat MeCN is 0.004, 22 times smaller than the flash photolysis value, indicating that regeneration of TBADT and MeCN (rate constant k ′ bh , see Scheme , right‐hand side) efficiently competes with coupling of the cyanomethyl radicals ( k ′ c = 1.2×10 9 m −1 s −1 ) 25…”

Section: Discussionmentioning

confidence: 95%

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Barluenga

Fernández

Satrústegui

et al. 2008

Chemistry A European J

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Anorganische Schichten: Graphenartiges MoS2 und WS2 wurde durch drei verschiedene chemische Methoden hergestellt. Mikroskopische Untersuchungen offenbarten, dass die Strukturen aus einer oder wenigen Schichten aufgebaut sind (siehe TEM‐Aufnahme von WS2‐Schichten), und ein atomar aufgelöstes TEM‐Bild zeigt, dass schichtförmiges MoS2 eine hexagonale Anordnung von Mo‐ und S‐Atomen aufweist (siehe Einschub).

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Section: Discussionmentioning

confidence: 95%

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Barluenga

Fernández

Satrústegui

et al. 2008

Chemistry A European J

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“…Under the steady-state conditions employed, the relationship is K 1 = {[CoR 1 ](2 k T1 ) 1/2 }/{[Co] V 1/2 }, where k T1 is the rate constant for cyanoisopropyl radical termination. Self-termination constants ( k T1 ) for • C(CH 3 ) 2 CN at a series of temperatures were obtained from literature results; k T1 is diffusion-controlled and has been modified for the viscosity of chloroform at the temperatures used in this study.…”

Section: Methodsmentioning

confidence: 99%

Kinetic Model for the Reaction of Cobalt Porphyrins with Olefins under Free Radical Conditions¹

et al. 1996

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A general kinetic model to describe the interaction of two dissimilar olefins with cobalt-(II) tetrakis(anisyl)porphyrin complexes in the presence of organic radicals has been developed. The kinetic scheme presumes the formation of organometallic products both by radical addition to Co(II) and by reaction of hydridocobalt(III) complexes with the corresponding olefins. The proposed general mechanism also presumes that cobalt hydride is formed by two pathwaysseither by bimolecular reaction of the Co(II) porphyrin complex with the radical or by unimolecular -hydrogen atom elimination from the organocobalt(III) species. The general model is then modified to the specific case of competition between methacrylonitrile and aliphatic olefins. On application of the simplifying assumption that most of the hydride forms through the bimolecular reaction and that both olefins follow the same predominant reaction pathways, a model describing the concentration of organometallic species derived from both olefins is developed. This dependence allows the evaluation of some elementary relative reaction rate constants for organometallic dissociation and reactions of the olefins with the hydridocobalt complex. It is shown that, despite the observation that the products derived from simple olefins such as cyclopentene are formed at much higher steady-state concentrations, methacrylonitrile reacts with hydridocobalt(III) at more than 25 times the rate of those simple olefins. Limitations on applying the developed methods of rate constant measurements have also been considered.

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“…This value is logical because k rr represents the reaction between two small‐sized radicals, which are very near after the decomposition of initiator (cage effect). Korth et al56 determined the constant of primary radical deactivation k rr at 60 °C for AIBN. They found a value about 5 · 10 9 L · mol −1 s −1 .…”

Section: Resultsmentioning

confidence: 99%

Kinetic Evaluation of Cooperative [Co(salen)] Catalysts in the Hydrolytic Kinetic Resolution of rac‐Epichlorohydrin

et al. 2010

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A wide variety of [Co(salen)] catalysts with different structures designed to enhance salen–salen cooperative interactions have been reported as catalysts for the hydrolytic kinetic resolution (HKR) of epoxides. However, the myriad catalysts have been evaluated under inconsistent experimental conditions, at different catalyst loadings, at different temperatures, with various epoxides and in several different laboratories, making rigorous comparisons between the catalysts impossible. To this end, 12 representative catalysts from our studies, as well as catalysts originally described by others, are reported in the HKR of epichlorohydrin under rigorously identical conditions. The comparison of the reactivity and selectivity of the different catalysts indicates that the soluble, oligomeric [Co(salen)] catalysts with cyclic frameworks impart the highest activity and enantioselectivity (>99 % ee, krel>99) in this representative reaction, requiring very short reaction times (<30 min), including the most active catalyst reported to date for the target reaction. In general, it is found that soluble polymer or oligomer‐supported catalysts are more active than insoluble supported catalysts under the conditions used. Among the insoluble catalysts, a polymer resin supported [Co(salen)] catalyst with excellent enantioselectivity (>99 % ee, krel>99) and medium reaction time (222 min), is the most active and selective of the class. The lessons demonstrated herein regarding design of active and selective catalysts offer useful insights into refining design strategies for other related cooperative catalytic reactions, suggesting emphases on catalyst flexibility and solubility under reaction conditions.

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Rate constants for the bimolecular self‐reaction of cyano‐substituted alkyl radicals in solution

Cited by 38 publications

References 29 publications

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Kinetic Model for the Reaction of Cobalt Porphyrins with Olefins under Free Radical Conditions¹

Kinetic Evaluation of Cooperative [Co(salen)] Catalysts in the Hydrolytic Kinetic Resolution of rac‐Epichlorohydrin

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Rate constants for the bimolecular self‐reaction of cyano‐substituted alkyl radicals in solution

Cited by 38 publications

References 29 publications

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Tandem Intramolecular Hydroalkoxylation–Hydroarylation Reactions: Synthesis of Enantiopure Benzofused Cyclic Ethers from the Chiral Pool

Kinetic Model for the Reaction of Cobalt Porphyrins with Olefins under Free Radical Conditions1

Kinetic Evaluation of Cooperative [Co(salen)] Catalysts in the Hydrolytic Kinetic Resolution of rac‐Epichlorohydrin

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Product

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Kinetic Model for the Reaction of Cobalt Porphyrins with Olefins under Free Radical Conditions¹