Stable CAAC‐based Ruthenium Complexes for Dynamic Olefin Metathesis Under Mild Conditions

A series of olefin metathesis catalysts bearing cyclic (alkyl)(amino)carbene (CAAC) ligands of varying size and steric demand has been synthesized and evaluated in ring‐closing‐, self‐, and cross‐metathesis reactions at room temperature. The catalysts were also probed for potential applications in dynamic covalent chemistry. The majority of the catalysts showed high stability, and remained active in the reaction mixtures for several days, including in methanol‐based solutions. Higher temperatures could be used to control the reactivity towards sterically challenging substrates, enabling formation of tetrasubstituted olefins. The CAAC complexes exhibited remarkable functional group tolerance towards heteroaromatic and nucleophilic additives, making them potentially useful in the screening of biologically active compounds. Balance for dynamics: The efficiency of catalysts based on cyclic (alkyl)(amino) carbenes (CAACs) has been evaluated in benchmark olefin metathesis reactions under mild conditions. The catalysts displayed a delicate balance between activity and stability, where good performance and functional group tolerance could be identified. Well‐balanced catalysts allowed for the generation of dynamic systems of olefins.