Synthesis of Imidized Cyclobutene Derivatives by Strain Release of [1.1.1]Propellane.

Herein, we report the metal-free synthesis of imidized methylene cyclobutane derivatives via a strain-release driven addition reaction of [1.1.1]propellane. Using this strategy, the methylene cyclobutyl cation intermediate generated by protonation of [1.1.1]propellane was found to be trapped by nitriles to form a nitrilium ion intermediate, which subsequently reacted with carboxylic acids to produce imidized methylene cyclobutene derivatives via a Mumm-type rearrangement.