Yne Metathesis

The experiments performed simultaneously with the same batch of reagents in air clearly showed differences in reactivity of 5, 14a, and 14b.This issue will be the subject of further detailed investigations (e.g., including the Nolan and Cavallo method [H NMR spectrum confirmed the structure of the obtained catalysts.The signals derived from the mesityl group protons (three singlets from the methyl groups and two singlets from the aromatic protons) have been well resolved in C NMR spectra signals from the carbenic carbons were weak.The first one (type A) is based on earlier reported salts 6–8 as the source of NHC carbene.Several attempts were undertaken to obtain new catalysts of type A via exchange with the commercial Hoveyda-Grubbs 1 generation complex (2) or complex 3.Their activities were compared with that of commercially available indenylidene catalyst.The structures of complexes and their stability were investigated using static DFT calculations with mixed basis set.], which are therefore attractive alternatives to well-known and more frequently used benzylidene catalysts.The exchange of carbene ligands in the commercial complexes failed probably due to poor nucleophilicity of the NHCs bearing nitroaryl substituents [).A methylene spacer should effectively suppress electronic interaction with the imidazolinium ring.The relative energy differences between such conformers amount about 50 and 20 k J/mol for 14a and 14b, respectively (see Supplementary Material).Additionally, the movements of chlorine ligands are suppressed due to the presence of stabilizing C–H···Cl H-bonds.


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