Pyrrole as a Directing Group: Regioselective Pd(II)-Catalyzed Alkylation and Benzylation at the Benzene Core of 2-Phenylpyrroles

Pyrrole has been employed for the first time as a directing group in the Pd(II)-catalyzed ortho-functionalization of C(sp²)-H bonds. A variety of substituted 2-phenylpyrroles were successfully methylated, alkylated, or benzylated in the ortho-position of the benzene ring, yielding the respective 2-substituted pyrrol-2-yl benzenes (36 examples, 51-93% yield). Neither additives nor additional ligands were required to perform the reaction, which was routinely conducted with PdBr₂ as the catalyst and Li₂CO₃ as the base. Mechanistically, there is evidence that precoordination of palladium to the pyrrole enables the regioselective ortho-attack. (Chemical Equation Presented).