Cyclobutane derivatives are important structural units in many natural products,[1, 2] but efficient methods for their synthesis are few compared to those for the preparation of other carbocyclic systems.[3, 4] An advance in the synthesis of cyclobutane derivatives involves metal-catalyzed ring-expansions of cyclopropane derivatives, including alkylidenecyclopropanes,[5] allenylcyclopropanols [6] or alkynylcyclopropanols,[7] with ...
