Temperature dependence of the cycloaddition of phenylchlorocarbene to alkenes. Observation of negative activation energies

Turro, Nicholas J.; Lehr, Gary F.; Butcher, Jared A.; Moss, Robert A.; Guo, Wenjeng

doi:10.1021/ja00370a059

Cited by 103 publications

(74 citation statements)

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“…As can be seen in Table 2, the nitrogen extrusion step is the rate-determining step of the catalytic cycle, as previously described for other similar systems. [10,16,21] The calculated activation energies for the cyclopropanation step indicate a very fast reaction, and compare well with the experimental [22] and theoretical [23] values determined for the cyclopropanation reactions with electrophilic carbenes, as well as with the experimental value determined for the reaction of a neutral carbene complex derived from a less electrophilic diazo compound (DG°= 20 kcal mol À1 ). [20] Concerning the mechanistic issue raised above, the results are not conclusive because the calculated carbene rotation barrier (14.5 kcal mol À1 ), which passes through TS 9 cr, is very similar to the cyclopropanation activation barriers (from 11.4 to 17.9 kcal mol À1 ), similarly to that described for salicylaldimine-Cu I systems.…”

Section: Experimental Catalysis Resultssupporting

confidence: 60%

C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

Fraile

Garcı́a

Gißibl

et al. 2007

Chemistry A European J

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A thorough experimental and theoretical study of the enantioselective cyclopropanation of alkenes catalyzed by chiral bis(oxazoline)- and azabis(oxazoline)-copper complexes, which comprise a new family of ligands that lack C2 symmetry, has been conducted. Surprisingly high enantioselectivities were observed with some of these ligands, which were rationalized on the basis of molecular modeling studies. The course of the asymmetric induction in connection with ligand symmetry and the implications for supported enantioselective catalysts are discussed.

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Section: Experimental Catalysis Resultssupporting

confidence: 60%

C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

Fraile

Garcı́a

Gißibl

et al. 2007

Chemistry A European J

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“…We found that favorable interaction energy contributes to negative ∆E at intermediate separation of the carbenes and alkenes studied here and suggests the formation of carbene-alkene precursor complexes, although the existence of these has been debated in the literature. [20][21][22][23][24][25][26][27][28][29] We have confirmed π-complexes for cycloadditions to 2a, 2b, and 2d that are stabilized by 0-5 kcal mol…”

Section: Resultsmentioning

confidence: 57%

Distortion/interaction analysis of the reactivities and selectivities of halo– and methoxy–substituted carbenes with alkenes

Sader¹,

Houk²

2014

Arkivoc

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Dedicated to Pierre Vogel, a great scientist and friend, on his 70 th birthday DOI: http://dx.doi.org/10.3998/ark.5550190.p008.408 AbstractThe transition structures for the (2+1) cycloadditions of dichlorocarbene, chlorofluorocarbene, and difluorocarbene to cyclohexene, 1-hexene, ethylene, and α-chloroacrylonitrile were located using quantum mechanical methods (M06-2X). In addition, transition structures for the (2+1) cycloadditions of chloromethoxycarbene, fluoromethoxycarbene, and dimethoxycarbene to ethylene and α-chloroacrylonitrile were computed. Except for the reactions with ethylene, these cycloadditions were studied experimentally and computationally by Moss and Krogh-Jespersen (Zhang, M.; Moss, R. A.; Thompson, J.; Krogh-Jespersen, K. J. Org. Chem. 2012, 77, 843-850). As a complement to the work of those groups, we have utilized the distortion/interaction model to understand reactivities and selectivities. Gas-phase calculations were carried out at the M06-2X/6-31+G(d,p) level of theory.

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“…The values obtained are quite small for both the k2 and k3 components (23) (the entropies of activation for the second-order reaction have larger errors incorporated into the calculation because of the fact that the values of k2 are intercepts). Negative activation energies have been obtained for the third-order components, which, although unusual, have been observed in other systems and are suggested as being support for intermediate formation along the reaction pathway in contrast to a direct displacement (24). The transition from tetrahedral phosphorus to a charged pentacoordinate intermediate, coupled with the incorporation of a second amine molecule in the transition state, should lead to very negative entropies of activation.…”

Section: Butylaminolysismentioning

confidence: 53%

The aminolysis of phosphinates; the kinetics and mechanism of the aminolysis of phosphinate esters in acetonitrile

Cook¹,

Daouk²,

Hajj³

et al. 1986

Can. J. Chem.

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. J. Chem. 64, 213 (1986).The aminolysis of aryl diphenylphosphinates, p-nitrophenyl diphenylphosphinothlonate, -phosphinothioate, and -phosphinodithioate by n-butylamine, by the secondary arnines piperidine, pyrrolidine, morpholine, and dipropylamine, as well as by a series of diamines, has been studied in acetonitrile. The general reactivity order is diamines > butylamine > sec-amines.Butylaminolysis follows a two-term rate law, one first order in amine and the other second order in amine. The second order in amine term predominates. sec-Arnines and diamines follow a rate law which is first order in amlne only. Leaving group effects, solvent effects, and activation parameters support a pathway which involves rate-determining collapse of a zwitterionic pentacoordinate intermediate. Operant dans I'acCtonitrile, on a CtudiC l'aminolyse des diphCnylphosphinates d'aryles et des diphCnyl-phosphinothionate, -phosphinothioate et -phosphinodithioate de p-nitro-phCnyle par la n-butylarnine, par les amines secondaires cornrne la pipendine, la pyrrolidine, la morpholine et la dipropylamine ainsi que par une sCrie de diamines. L'ordre de rCactivitC gCnCrale est le suivant: diamines, butylamine, amines secondaires. La butylaminolyse obCit a une Cquation de vitesse impliquant deux termes, un du premier ordre en amine et un autre du deuxieme ordre en amine. Le terme du deuxikme ordre en arnine prCdomine. Les reactions avec les arnines secondaires et avec les diamines obCissent a une Cquation du premier ordre en arnine seulement. Les effets de groupements nuclCofuges et de solvants ainsi que les parametres d'activation sont en accord avec un mCcanisme rCactionnel irnpliquant une Ctape dkterminante au cours de laquelle il y a dCcomposition d'un intermkdiaire zwitteriol~ique pentacoordonnC. Dans le cas de la butylamine, cette dCcomposition est sournise a une catalyse gCnCrale des bases et, pour les diarnines, la rCaction est soumise B une catalyse gCnCrale des bases qui est intramoltculaire.[Traduit par le journal]

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Temperature dependence of the cycloaddition of phenylchlorocarbene to alkenes. Observation of negative activation energies

Cited by 103 publications

References 0 publications

C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

Distortion/interaction analysis of the reactivities and selectivities of halo– and methoxy–substituted carbenes with alkenes

The aminolysis of phosphinates; the kinetics and mechanism of the aminolysis of phosphinate esters in acetonitrile

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Temperature dependence of the cycloaddition of phenylchlorocarbene to alkenes. Observation of negative activation energies

Cited by 103 publications

References 0 publications

C1‐Symmetric Versus C2‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

C1‐Symmetric Versus C2‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

Distortion/interaction analysis of the reactivities and selectivities of halo– and methoxy–substituted carbenes with alkenes

The aminolysis of phosphinates; the kinetics and mechanism of the aminolysis of phosphinate esters in acetonitrile

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C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions

C₁‐Symmetric Versus C₂‐Symmetric Ligands in Enantioselective Copper–Bis(oxazoline)‐Catalyzed Cyclopropanation Reactions