Ruthenium Carbene Complexes with N,N‘-Bis(mesityl)imidazol-2-ylidene Ligands: RCM Catalysts of Extended Scope
摘要:
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.
Synthesis of novel macrocyclic peroxides by bis(sym-collidine)iodine (I) hexafluorophosphate-mediated cyclization of unsaturated hydroperoxides and unsaturated alcohols
Bis(sym-collidine)iodine (I) hexafluorophosphate-mediated cyclization of unsaturated hydroperoxides, prepared by a variety of different methods, afforded the corresponding 10- to 20-membered macrocyclic peroxides having two or three peroxide units located within one ring in moderate yields. By analogy, cyclization of unsaturated alcohols having one or two peroxide bond in the chain afforded the corresponding