Wydział Chemii

Maciej Gierada

Izabela Czeluśniak

Jarosław Handzlik

2019

Molecular Catalysis

469

18-26

10.1016/j.mcat.2019.02.026

Naukowa

Angielski

Artykuł

Transformations of alkynes are of great importance in organic synthesis, including formation of natural compounds. Products of CC coupling of terminal alkynes, such as conjugated 1,3- or 1,4-enynes and tri-substituted benzene derivatives are key units of variety natural and biologically active products. Ruthenium catalysts can be effective for such synthesis, however, the mechanisms of these reactions are still not well understood. In this work, dimerization and cyclotrimerization of terminal arylalkyne (phenylacetylene) initiated by the third-generation Grubbs catalyst [RuCl₂(CHPh)(3-Br-py)₂(H₂IMes)] have been theoretically and experimentally studied. It is shown that ruthenium vinylidene species might be the key intermediate in the catalytic cycle of phenylacetylene dimerization, whereas [RuCl₂(H₂IMes)] can be the active species in phenylacetylene cycylotrimerization. Ruthenium alkyne species [RuCl₂(η²PhCCH)(H₂IMes)] is a common intermediate for both competitive reactions. An overall mechanism for terminal arylalkyne transformations is proposed. It includes alkyne-induced decomposition of the phosphine-free ruthenium alkylidene catalyst via ruthenium vinylcarbene to ruthenium vinylidene and [RuCl₂(H₂IMes)], followed by the dimerization and cyclotrimerization reactions.

Cyclotrimerization, DFT calculations, dimerization, Grubbs catalyst, Phenylacetylene

https://doi.org/10.1016/j.mcat.2019.02.026

http://www.elsevier.com