Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia.
Int J Mol Sci. 2021 Mar 21;22(6):3193. doi: 10.3390/ijms22063193.
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 -iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN) as a nitrogen donor. The reaction requires six steps with the activation barrier Δ = 33.5 kcal mol and a highly exergonic reaction free-energy Δ = -191.9 kcal mol in MeCN. Reaction profiles agree with several experimental observations, offering evidence for the formation of molecular I, 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 as an alternative to TMSN. Lastly, our results advise increasing the solvent polarity as another route to advance this metal-free strategy towards more efficient processes.
密度泛函理论计算阐明了二苯乙炔转化为苯甲腈的精确反应机制，涉及到三重 C≡C 键的断裂，其中 - 碘代琥珀酰亚胺 (NIS) 作为氧化剂，三甲基硅基叠氮化物 (TMSN) 作为氮供体。该反应需要六个步骤，在 MeCN 中的活化势垒 Δ = 33.5 kcal mol，反应自由能 Δ = -191.9 kcal mol 高度放热。反应轮廓与几个实验观察结果一致，为分子 I 的形成提供了证据，解释了需要提高温度以完成反应的必要性，并揭示了热力学方面的因素，使得带有供电子基团的炔烃具有更高的产率。此外，所提出的机制表明了该概念对于内部和末端炔烃的有用性，排除了用其 Cl-或 Br-类似物替代 NIS 的可能性，并强烈促进了 NaN 作为 TMSN 的替代物。最后，我们的结果建议增加溶剂极性作为推进这种无金属策略向更高效过程发展的另一种途径。
