Direct Metal-Free Transformation of Alkynes to Nitriles: Computational Evidence for the Precise Reaction Mechanism
Density functional theory calculations elucidated the precise reaction mechanism for the conversion of diphenylacetylenes into benzonitriles involving the cleavage of the triple C≡C bond, with <i>N</i>-iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN<sub>3</sub...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-03-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/22/6/3193 |
| Summary: | Density functional theory calculations elucidated the precise reaction mechanism for the conversion of diphenylacetylenes into benzonitriles involving the cleavage of the triple C≡C bond, with <i>N</i>-iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN<sub>3</sub>) as a nitrogen donor. The reaction requires six steps with the activation barrier Δ<i>G</i><sup>‡</sup> = 33.5 kcal mol<sup>−1</sup> and a highly exergonic reaction free-energy Δ<i>G</i><sub>R</sub> = −191.9 kcal mol<sup>−1</sup> in MeCN. Reaction profiles agree with several experimental observations, offering evidence for the formation of molecular I<sub>2</sub>, interpreting the necessity to increase the temperature to finalize the reaction, and revealing thermodynamic aspects allowing higher yields for alkynes with para-electron-donating groups. In addition, the proposed mechanism indicates usefulness of this concept for both internal and terminal alkynes, eliminates the option to replace NIS by its Cl- or Br-analogues, and strongly promotes NaN<sub>3</sub> as an alternative to TMSN<sub>3</sub>. Lastly, our results advise increasing the solvent polarity as another route to advance this metal-free strategy towards more efficient processes. |
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| ISSN: | 1661-6596 1422-0067 |