Highly Robust and Efficient Blechert-Type Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Olefin Metathesis

New Blechert-type ruthenium complexes containing cyclic(alkyl)(amino)carbene (CAAC) ligands are reported. These catalysts demonstrate remarkable thermal stability in solution and excellent catalytic performances at low catalytic loading (up to 0.005 mol %) in ring-closing metathesis (RCM), macro-RCM, ring-closing enyne metathesis (RCEYM), cross-metathesis (CM), ethenolysis and ring-opening cross metathesis (ROCM). Moreover, up to 95% enantiomeric excess (ee) was obtained in asymmetric ring-opening cross metathesis (AROCM) and 57% ee was obtained in asymmetric cross-metathesis (ACM).