Ligand-Enabled β-C(sp)-H Olefination of Free Carboxylic Acids.

An acetyl-protected aminoethyl phenyl thioether has been developed to promote C(sp)-H activation. Significant ligand enhancement is demonstrated by the realization of the first Pd(II)-catalyzed olefination of C(sp)-H bonds of free carboxylic acids without using an auxiliary. Subsequent lactonization of the olefinated product via 1,4 addition provided exclusively monoselectivity in the presence of multiple β-C-H bonds. The product γ-lactone can be readily opened to give either the highly valuable β-olefinated or γ-hydroxylated aliphatic acids. Considering the challenges in developing Heck couplings using alkyl halides, this reaction offers a useful alternative.