Palladium-catalyzed ortho-selective C-H deuteration of arenes: evidence for superior reactivity of weakly coordinated palladacycles.

We disclose a protocol for the palladium-catalyzed ortho-selective C-H deuteration of arenes. Phenylacetic acids and benzoic acids are suitable substrates for this reaction. This reaction offers a catalytic route to ortho-deuterated phenylacetic acids and benzoic acids and demonstrates the sharp difference in reactivity of palladacycle intermediates held together by weak and strong coordination.