文摘
N-Heterocyclic carbene (NHC) ligands IMeslass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">NMe2l:math> and IMeslass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">(NMe2)2l:math> derived from the well-known IMes ligand by substituting the carbenic heterocycle with one and two dimethylamino groups, respectively, were employed for the synthesis of second-generation Grubbs- and Grubbs–Hoveyda-type ruthenium metathesis precatalysts. Whereas the stability of the complexes was found to depend on the degree of dimethylamino-substitution and on the type of complex, the backbone-substitution was shown to have a positive impact on their catalytic activity in ring-closing metathesis, with a more pronounced effect in the second-generation Grubbs-type series. The new complexes were successfully implemented in a number of challenging olefin metathesis reactions leading to the formation of tetra-substituted C=C double bonds and/or functionalized compounds.