Cyclometalated Ruthenium-Catalyst Enables ortho-Selective C–H Alkylation with Secondary Alkyl Bromides

While Ru-catalyzed meta-selective sp2 C–H alkylation with secondary alkyl halides is well established, ortho-selectivity has never been achieved. We demonstrate that the use of a cyclometalated Ru-complex, RuBnN, as the catalyst results in a complete switch of the inherent meta-selectivity to ortho-selectivity in the Ru-catalyzed sp2 C–H alkylation reaction with unactivated secondary alkyl halides. The high catalytic activity of RuBnN allows for mild reaction conditions that result in a transformation of broad scope and versatility. Preliminary mechanistic studies suggest that a bis-cycloruthenated species is the key intermediate undergoing oxidative addition with the alkyl halides, thus avoiding the more common SET pathway associated with meta-selectivity.