Arene Ring Expansion by Ruthenium η-Arene Complexes.

Transition metal π-arene complexes enable the dearomatization of benzene rings to access diversified unsaturated carbocycles through multistep synthetic procedures involving sequential addition of nucleophiles and electrophiles. This work details a single-step dearomatization process by reaction of Ru(η-arene) complexes with enolates derived from α-halo or α-(tosyloxy)esters to directly transform π-coordinated arenes to ring-expanded cycloheptatrienes.