scholarly journals Computational Study on the Boundary Between the Concerted and Stepwise Mechanism of Bimolecular SNAr Reactions

2020 ◽  
Vol 142 (35) ◽  
pp. 14871-14876 ◽  
Author(s):  
Simon Rohrbach ◽  
John A. Murphy ◽  
Tell Tuttle
Keyword(s):  
Computational Study ◽  
Stepwise Mechanism

scholarly journals A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5562
Author(s):  
Grzegorz Mlostoń ◽  
Karolina Kula ◽  
Radomir Jasiński
Keyword(s):  
Molecular Mechanism ◽  
Sulfur Atom ◽  
Molecular Mechanisms ◽  
Computational Study ◽  
Cycloaddition Reaction ◽  
Single Step ◽  
Stepwise Mechanism ◽  
Nucleophilic Carbenes ◽  
Transient Intermediate ◽  
Single Step Reaction

The molecular mechanisms of addition of dihalocarbenes and dimethoxycarbene to thioketones derived from 2,2,4,4-tetrmethylcyclobutane-1,3-dione were examined on the basis of the DFT wb97xd/6-311g(d,p)(PCM) calculations. Obtained results demonstrated that the examined processes exhibit polar nature and in the case of electrophilic dichloro-, and dibromocarbenes are initiated by the attack of carbene species onto the sulfur atom of the C=S group. Remarkably, reactions involving more electrophilic carbenes (dichloro-, and dibromocarbene) proceeds via stepwise mechanism involving thiocarbonyl ylide as a transient intermediate. In contrast, analogous reactions with nucleophilic dimethoxycarbene occur via a single step reaction, which can be considered as the [2 + 1] cycloaddition reaction initiated by the attack onto the C=S bond. A computational study showed that difluorocarbene tends to react as a nucleophilic species and resembles rather dimethoxycarbene and not typical dihalocarbene species. Significantly higher reactivity of the thioketone unit in comparison to the ketone group, both present in 3-thioxo-2,2,4,4-tetramthylcyclobutanone molecule, was rationalized in the light of DFT computational study.

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