Meta-Selective CAr-H Nitration of Arenes through a Ru3(CO)12-Catalyzed Ortho-Metalation Strategy

The first example of transition metal-catalyzed meta-selective C-Ar-H nitration of arenes is described. With the use of Ru-3(CO)(12) as the catalyst and Cu(NO3)(2)center dot 3H(2)O as the nitro source, a wide spectrum of arenes bearing diversified N-heterocycles or oximido as the directing groups were nitrated with meta selectivity exclusively. Mechanism studies have demonstrated the formation of a new 18e-octahedral ruthenium species as a key ortho-C-Ar-H metalated intermediate, which may be responsible for the subsequent meta-selective electrophilic aromatic substitution (SEAr). Moreover, this approach provides a fast-track strategy for atom/step economical synthesis of many useful pharmaceutical molecules.