35. Connecting Remote C–H Bond Functionalization and Decarboxylative Coupling Using Simple Amines

de Azambuja, F.; Yang, M.-H.; Feoktistova, T.; Selvaraju, M.; Brueckner, A. C.; Grove, M. A.; Koley, S.; Cheong, P. H.-Y.;* Altman, R. A.*

Nature Chem. 2020, 12, 489–496.

Transition metal-catalysed C–H functionalization and decarboxylative coupling are two of the most notable synthetic strategies developed in the past 30 years. Here, we connect these two reaction pathways using bases and a simple Pd-based catalyst system to promote a para-selective C–H functionalization reaction from benzylic electrophiles. Experimental and computational mechanistic studies suggest a pathway that involves an uncommon Pd-catalysed dearomatization of the benzyl moiety followed by a base-enabled rearomatization through a formal 1,5-hydrogen migration. This reaction complements ‘C–H activation’ strategies that convert inert C–H bonds into C–metal bonds prior to C–C bond formation. Instead, this reaction exploits an inverted sequence and promotes C–C bond formation prior to deprotonation. These studies provide an opportunity to develop general para-selective C–H functionalization reactions from benzylic electrophiles and show how new reactive modalities may be accessed with careful control of the reaction conditions.