Ligand-promoted palladium-catalyzed β-methylene C-H arylation of primary aldehydes.

The transient directing group (TDG) strategy allowed long awaited access to the direct β-C(sp)-H functionalization of unmasked aliphatic aldehydes palladium catalysis. However, the current techniques are restricted to terminal methyl functionalization, limiting their structural scopes and applicability. Herein, we report the development of a direct Pd-catalyzed methylene β-C-H arylation of linear unmasked aldehydes by using 3-amino-3-methylbutanoic acid as a TDG and 2-pyridone as an external ligand.