The kinetics and mechanism of the reaction of trimethyl phosphate with benzylideneacetophenones

Petneházy, Imre; Clementis, György; Jászay, Zsuzsa M.; Tőke, Lásʐló; Hall, C. Dennis

doi:10.1039/p29960002279

Cited by 7 publications

(5 citation statements)

References 19 publications

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“…The Hammett plots are nevertheless a concise representation of the observed electronic effects and the ligand optimization process. For single reactions, curved Hammett plots generally signify a change in mechanism, yet here introduction of the R 4 substituent on nitrogen simply breaks the original C2 symmetry of the diamine. In short, the two aryl rings derived from the diamine are now different, and linear behavior for the sum of the electronic contributions of these two different rings is not expected in any case.…”

Section: Resultsmentioning

confidence: 99%

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

et al. 2004

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The Boehringer-Ingelheim phosphinoimidazoline (BIPI) ligands were applied to the formation of chiral quaternary centers in the asymmetric Heck reaction. Several different substrates were examined in detail, using more than 70 members of this new ligand class. Hammett relationships were determined through systematic variation of the ligand electronics. All substrates showed essentially the same Hammett behavior, where enantioselectivity increased as the ligands were made more electron-deficient. Ligand optimization has led to catalysts which give the highest enantioselectivities reported to date for these difficult systems.

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Section: Resultsmentioning

confidence: 99%

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

et al. 2004

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“…This method, which allowed us to characterize the electrophilicities of a large variety of Michael acceptors, could not be adapted to the investigation of the synthetically most important Michael acceptors, for example, monoacceptor-substituted ethylenes, because the nucleophilic attack of stabilized carbanions at acrylates, acrylonitrile, vinyl ketones, or vinyl sulfones is usually reversible due to the low stabilization of the resulting carbanions. Other groups have circumvented this problem by performing the kinetic investigations in aqueous or alcoholic solution, where the initially generated carbanions are immediately trapped by proton transfer from the solvent. − …”

Section: Introductionmentioning

confidence: 99%

Quantification and Theoretical Analysis of the Electrophilicities of Michael Acceptors

et al. 2017

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In order to quantify the electrophilic reactivities of common Michael acceptors, we measured the kinetics of the reactions of monoacceptor-substituted ethylenes (HC═CH-Acc, 1) and styrenes (PhCH═CH-Acc, 2) with pyridinium ylides 3, sulfonium ylide 4, and sulfonyl-substituted chloromethyl anion 5. Substitution of the 57 measured second-order rate constants (log k) and the previously reported nucleophile-specific parameters N and s for 3-5 into the correlation log k = s(E + N) allowed us to calculate 15 new empirical electrophilicity parameters E for Michael acceptors 1 and 2. The use of the same parameters s, N, and E for these different types of reactions shows that all reactions proceed via a common rate-determining step, the nucleophilic attack of 3-5 at the Michael acceptors with formation of acyclic intermediates, which subsequently cyclize to give tetrahydroindolizines (stepwise 1,3-dipolar cycloadditions with 3) and cyclopropanes (with 4 and 5), respectively. The electrophilicity parameters E thus determined can be used to calculate the rates of the reactions of Michael acceptors 1 and 2 with any nucleophile of known N and s. DFT calculations were performed to confirm the suggested reaction mechanisms and to elucidate the origin of the electrophilic reactivities. While electrophilicities E correlate poorly with the LUMO energies and with Parr's electrophilicity index ω, good correlations were found between the experimentally observed electrophilic reactivities of 44 Michael acceptors and their calculated methyl anion affinities, particularly when solvation by dimethyl sulfoxide was taken into account by applying the SMD continuum solvation model. Because of the large structural variety of Michael acceptors considered for these correlations, which cover a reactivity range of 17 orders of magnitude, we consider the calculation of methyl anion affinities to be the method of choice for a rapid estimate of electrophilic reactivities.

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“…In 1996, a new kind of ring enlargement was proposed: a vinylcyclopropane cyclopentene-type rearrangement of a transiently formed 3-vinyl-substituted oxaphosphirane; however, no strong evidence was provided for the existence of the latter. [7] s 3 l 3 -Oxaphosphirane complexes IV (E = W(CO) 5 ) were first described in 1990 by Mathey and co-workers, using epoxidation of phosphaalkenes with metachloroperbenzoic acid (m-CPBA). [8] In 1994 we used a thermal phosphinidene complex transfer reaction onto aldehydes [9] and, more recently, Li/Cl phosphinidenoid complexes and aldeyhdes at low temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Transient σ 5 λ 5 ‐oxaphosphiranes were claimed already in 1982,6a but until 1988, when Boisdon and Barrans reported a monomer–dimer equilibrium,6b their existence was not firmly established. In 1996, a new kind of ring enlargement was proposed: a vinylcyclopropane cyclopentene‐type rearrangement of a transiently formed 3‐vinyl‐substituted oxaphosphirane; however, no strong evidence was provided for the existence of the latter 7. σ 3 λ 3 ‐Oxaphosphirane complexes IV (E=W(CO) 5 ) were first described in 1990 by Mathey and co‐workers, using epoxidation of phosphaalkenes with meta ‐chloroperbenzoic acid ( m ‐CPBA) 8.…”

Section: Introductionmentioning

confidence: 99%

The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH₃PO Isomers and Their Cr(CO)₅ Complexes

Krahe

Neese

Streubel

2009

Chemistry A European J

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Opening gambit: A high-level theoretical study on the relative stabilities of oxaphosphirane isomers and their Cr(CO)(5) complexes is reported (see picture). Furthermore, thermodynamics and kinetics of possible ring-opening reactions of these complexes in the presence of a {Cp(2)Ti(III)Cl} fragment are theoretically investigated. The C--O bond cleavage is predicted to be the most efficient pathway, thus leading to reactive intermediates that are attractive for synthetic applications.A high-level theoretical study on the relative stabilities of oxaphosphirane isomers and their Cr(CO)(5) complexes is reported. Furthermore, thermodynamics and kinetics of possible ring-opening reactions of these complexes in the presence of a {Cp(2)Ti(III)Cl} fragment are theoretically investigated. The C--O bond cleavage is predicted to be the most efficient pathway thus leading to reactive intermediates that are attractive for synthetic applications. The ring-opening reaction is predicted to not lead to the most favorable product (a coordinated phosphinidene oxide species). Rather, the ring-opening product is separated by a substantial barrier of about 24 kcal mol(-1) from the thermodynamically most favorable species.

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The kinetics and mechanism of the reaction of trimethyl phosphate with benzylideneacetophenones

Cited by 7 publications

References 19 publications

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

Quantification and Theoretical Analysis of the Electrophilicities of Michael Acceptors

The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH₃PO Isomers and Their Cr(CO)₅ Complexes

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The kinetics and mechanism of the reaction of trimethyl phosphate with benzylideneacetophenones

Cited by 7 publications

References 19 publications

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

Electronic Control of Chiral Quaternary Center Creation in the Intramolecular Asymmetric Heck Reaction

Quantification and Theoretical Analysis of the Electrophilicities of Michael Acceptors

The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH3PO Isomers and Their Cr(CO)5 Complexes

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The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH₃PO Isomers and Their Cr(CO)₅ Complexes