Highly Selective Olefin Metathesis with CAAC-Containing Ruthenium Benzylidenes

Several olefin metathesis reactions are studied, namely, jojoba oil oligomerization, methyl oleate self-metathesis, ring-closing metathesis (RCM) to form a nitrogen heterocycle, and 1,5-hexadiene acyclic diene metathesis polymerization (ADMET). The catalyst containing the Bertrand-Grubbs cyclic alkyl amino carbene (CAAC) ligand showed high selectivity by diminishing isomerization reactions; this was especially clear at high temperatures where the more widely used nitrogen heterocyclic carbene (NHC)-based catalysts show side reactions. Experimental and computational studies determined that it is much more difficult to produce ruthenium hydrides with CAAC, a property that can explain the improved observed activity. This finding opens a pathway for the development of even more selective olefin metathesis catalysts for reactions that require harsh conditions.