Ruthenium(II)-Catalyzed C-H Alkenylations of Phenols with Removable Directing Groups

Cationic ruthenium(II) complexes enabled oxidative alkenylations of phenols bearing easily cleavable directing groups. The optimized catalytic system allowed twofold C-H bond activations with excellent chemo-, site-, and diastereoselectivities. The double C-H functionalization process proceeded efficiently in an aerobic fashion under an atmosphere of ambient air. Detailed mechanistic studies were performed and provided strong support for an initial reversible C-H bond activation by the formation of six-membered ruthenacycles as the key intermediates.