Ruthenium carbene complexes with N,N'-bis(mesityl)imidazol-2-ylidene ligands: RCM catalysts of extended scope
The ruthenium carbene complexes 3a,b bearing imidazol-2-ylidene ligands constitute excellent precatalysts for ring-closing metathesis (RCM) reactions allowing the formation of tri- and tetrasubstituted cycloalkenes. They also apply to annulations that are beyond the scope of the standard Grubbs carbene 1 as well as to ring-closing reactions of acrylic acid derivatives even if the resulting alpha,beta-unsaturated lactones (or lactams) are tri- or tetrasubstituted. The reactivity of 3a was found to be highly dependent on the reaction medium: particularly high reaction rates are observed in toluene, although this solvent also leads to an increased tendency of the catalyst to isomerize the double bonds of the substrates.
Furstner
A
Max-Planck-Institut fur Kohlenforschung, Mulheim/Ruhr, Germany. fuerstner@mpi-muelheim.mpg.de
Thiel
OR
Ackermann
L
Schanz
HJ
Nolan
SP