Figure 2: Proof of concept on alkoxycarbonylation of methylene C(sp3)–H bonds via Pd(II)/Pd(IV) catalysis.

(a) Synthesis of palladacycle I. (b) Stoichiometric reaction of palladacycle I with carbon monoxide. (c) Synthesis of CO-coordinated Pd(II) complex II. (d) Structure confirmation of complex II via the transformation to complex III. The structure of complex III was unambiguously confirmed by single-crystal X-ray diffraction. (e) Stoichiometric reaction of palladacycle I with ClCO2R. The structure of compounds 3a and 4b was confirmed by single-crystal X-ray diffraction.