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.