Flash Communication: Carbanion Translocation via Intramolecular 1,2-Proton Transfer for One-Carbon Expansion of Lanthanide Metallacycles

Intramolecular hydrogen transfer represents one of the most fundamental and ubiquitous processes in both chemical and biological transformations. Here, we introduce a rare intramolecular 1,2-proton transfer within lanthanide metallacycles proceeds without external shuttles. The transformation converts five-membered lutetacyclopentenes into six-membered rings through a formal 1,2-proton transfer achieved via sequential 1,5- and 1,4-proton shifts. DFT calculations reveal that the Lu–C bond acts as an internal proton relay, preorganizing the transfer trajectory and lowering the barrier. Isolation of a ligand-stabilized intermediate further substantiates the proposed stepwise mechanism.