Pd(II)-Catalyzed Synthesis of Benzocyclobutenes by β-Methylene-Selective C(sp3)‒H Arylation with a Transient Directing Group

Methylene-selective C‒H functionalization is a significant hurdle that remains to be addressed in the field of Pd(II) cataly-sis. In this paper we report a Pd(II) catalyzed synthesis of benzocyclobutenes by methylene-selective C(sp3)‒H arylation of ketones using a transient directing group. The reaction utilizes glycine as a transient directing group and an electron poor pyridone ligand which is expected to promote concerted metallation deprotonation, but also controls methylene selectivity by intimate interactions with the substrate. These reaction conditions are shown to be highly selective for in-tramolecular methylene C(sp3)‒H arylation, and thus enable sequential C(sp3)‒H functionalization.