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Опарина, Л. А.; Паршина, Л. Н.; Khil’ko, M. Ya.; Gorelova, O. V.; Preiß, Thomas; Henkelmann, Jochem; Трофимов, Б. А.

doi:10.1023/a:1013847901532

Cited by 11 publications

(7 citation statements)

References 3 publications

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“…Indeed, in both PENTA and MONO models, the PhC(O)CH 2 − carbanion is bound to the water molecule present in the coordination sphere. The hydration of the nucleophile decreases its activity as evidenced by experimental data . Indeed, for the ANION GAS model, simply including a water molecule in the reaction system leads to an increase of the activation energy for reaction ( 9 ) by 2.13 kcal/mol and improves the agreement with the results of the more complicated PENTA and MONO models.…”

Section: Resultsmentioning

confidence: 72%

Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Vitkovskaya

Orel

Кобычев

et al. 2020

Int J of Quantum Chemistry

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The mechanisms of fundamental base‐promoted acetylene reactions, namely, nucleophilic addition to the triple C ≡ C bond (vinylation) and nucleophilic addition of acetylenic carbanion to a carbonyl group (ethynylation), are addressed using three models of different complexity—pentasolvate, monosolvate, and anionic—which describe the catalytic superbasic systems MOH(OBut)/DMSO (suspensions of alkali hydroxides or tert‐butoxides in dimethyl sulfoxide). The above acetylene reactions and sequential transformations of reagents arranged by the superbasic center are modeled within the framework of the most complete pentasolvate model, in which the superbase is represented by the KOH·5DMSO (KOBut·5DMSO) complexes. We have developed approaches to the construction of simplified models (monosolvate and anionic) to describe transformations in complex systems. The mechanisms of cascade assemblies of 6,8‐dioxabicyclo[3.2.1]octanes, cyclopentenones, and furan cycles from ketones and acetylenes in the superbasic environment are investigated using a uniform B2PLYP/6‐311+G**//B3LYP/6‐31+G* approach, and the energy profiles of these different carbo‐ and heterocycles are analyzed.

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Section: Resultsmentioning

confidence: 72%

Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Vitkovskaya

Orel

Кобычев

et al. 2020

Int J of Quantum Chemistry

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“…It is known that the presence of water hinders the vinylation reactions in superbasic media. , Our quantum-chemical calculations show that water molecules can hydrate the initial nucleophile, reducing its activity, the activation barrier of the reaction being increased owing to a larger stabilization of the starting reagents relative to the corresponding transition state. The activation barrier of nucleophilic addition of “anhydrous” complex of potassium enolate, K + [CH 2 (CO)CH 3 ] − ·5DMSO, to the triple bond of phenylacetylene is estimated to be Δ H ⧧ = 15.7 kcal/mol, Δ G ⧧ = 23.4 kcal/mol, which is lower (by ΔΔ H ⧧ = 1.0 kcal/mol, ΔΔ G ⧧ = 1.2 the kcal/mol) than the vinylation barrier in complex 7 containing a water molecule.…”

Section: Resultsmentioning

confidence: 99%

Transition-Metal-Free C-Vinylation of Ketones with Acetylenes: A Quantum-Chemical Rationalization of Similarities and Differences in Catalysis by Superbases MOH/DMSO and tBuOM/DMSO (M = Na, K)

et al. 2018

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Transition-metal-free C-vinylation of acetone with phenylacetylene catalyzed by superbases MOH/DMSO and tBuOM/DMSO (M = Na, K) has been theoretically evaluated in the B3LYP/6-311++G**//B3LYP/6-31+G* approach to rationalize similarities and differences in activity of the above catalytic systems. The close solvate surroundings of sodium and potassium tert-butoxides have been studied. Formation of tBuOM· nDMSO complexes and their structure and thermodynamic stability are discussed in comparison with similar complexes of alkali-metal hydroxides MOH· nDMSO. Activation barriers of the title reaction in the presence of tBuOM· nDMSO complexes are found to be less than those with MOH· nDMSO complexes participating.

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“…However, the possibility of proton transportation to the remote carbanionic center is far from being fully clarified. In some cases, the presence of water hinders the reaction . At the same time, some examples of intentional introduction of water to the reaction system for suppression of undesirable side processes were reported .…”

Section: Introductionmentioning

confidence: 99%

Exploring acetylene chemistry in superbasic media: A theoretical study of the effect of water on vinylation and ethynylation reactions with acetylene in KOH/DMSO and NaOH/DMSO systems

Vitkovskaya

Orel

Кобычев

et al. 2016

J. Phys. Org. Chem.

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A rapidly developing approach adding new dimensions to acetylene chemistry relying on employment of high basicity media such as alkali metal hydroxide suspensions in dimethyl sulfoxide (DMSO) has been, for the first time, investigated theoretically using ab initio models. Extending our recently introduced model of superbase catalysis with a nondissociated KOH (or NaOH) participation, we present here a model for a superbasic reaction center with the first solvation shell explicitly included. The alkali metal hydroxides in a DMSO solution were found to form KOH·5DMSO and NaOH·4DMSO complexes that are stabilized due to the interligand interaction. Our present MP2/6‐311++G**//B3LYP/6‐31+G* computations show that 1 and 2 water molecules can build themselves into the MOH close surrounding without substantially perturbing the DMSO ligands and easily travel between different insertion positions. Our results predict that the activation energies in the series of reactions of nucleophilic addition to a triple bond with water, methanol, methanethiol, sodium hydrosulfide, and acetone in the presence of dihydrated complexes should be larger than those obtained with the participation of monohydrated ones, which is in fair agreement with the experimental findings. The present model also explains an increase in the ethynylation reaction yield in the presence of water by suppression of the competitive enolization reaction.

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Cited by 11 publications

References 3 publications

Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Transition-Metal-Free C-Vinylation of Ketones with Acetylenes: A Quantum-Chemical Rationalization of Similarities and Differences in Catalysis by Superbases MOH/DMSO and tBuOM/DMSO (M = Na, K)

Exploring acetylene chemistry in superbasic media: A theoretical study of the effect of water on vinylation and ethynylation reactions with acetylene in KOH/DMSO and NaOH/DMSO systems

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Untitled

Cited by 11 publications

References 3 publications

Quantum‐chemical models of KOH(KOBut)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Quantum‐chemical models of KOH(KOBut)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Transition-Metal-Free C-Vinylation of Ketones with Acetylenes: A Quantum-Chemical Rationalization of Similarities and Differences in Catalysis by Superbases MOH/DMSO and tBuOM/DMSO (M = Na, K)

Exploring acetylene chemistry in superbasic media: A theoretical study of the effect of water on vinylation and ethynylation reactions with acetylene in KOH/DMSO and NaOH/DMSO systems

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Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions

Quantum‐chemical models of KOH(KOBu^t)/DMSO superbasic systems and mechanisms of base‐promoted acetylene reactions