One‐Step Synthesis of Cyclobutene‐Annulated Fullerenes through a Cascade Reaction

Abstract

The physicochemical properties of fullerene‐based materials typically vary depending on the type and mode of addition of functional groups; therefore, developing fullerene derivatives with novel structures is imperative for further progress in materials science. In this study, we develop an efficient one‐step strategy for synthesizing cyclobutene‐annulated fullerene derivatives (cyclobutenofullerenes) and characterize their electronic properties. Despite the steric strain, cyclobutenofullerenes can be easily prepared via a one‐step reaction of C60 with a secondary propargylic phosphate. Structural analysis of the reaction intermediates suggests that the cascade reaction proceeds through a formal [2 + 2] cycloaddition of C60 with an allene, caused by the 1,3‐migration of the propargylic phosphate, followed by an additional 1,3‐migration and the subsequent 1,2‐elimination of the phosphodiester moiety.