Effect of Alkoxy Substituents on the Regioselectivity of Catalytic C-H Activation in Benzoic Acids: Experimental and DFT Study

This work demonstrates the influence of the catalyst and alkyne nature on the regioselectivity of rhodium-catalyzed annulation of alkoxy-substituted benzoic acids (such as 3-methoxybenzoic, 3,4-dimethoxybenzoic, and piperonylic acids) with alkynes. Here, X-ray diffraction and DFT calculation data gave evidence that the observed regioselectivity is provided by both steric and coordination effects of methoxy groups. The latter is the result of weak non-covalent C–H⋯O interactions with the supporting ligand rather than with the rhodium atom. We believe that these results are also valid for other reactions of the C-H activation of methoxy-substituted arene compounds.