Copper-Mediated Cascade Synthesis of Open-Cage Fullerenes

An open-cage fullerene bearing an eight-membered ring orifice has been synthesized in one pot by the reaction of C-60 with propargylic phosphate in the presence of CuCl. The reaction cascade involves the transformation of the phosphate to the 1,3-dienyl phosphate, which enables the reaction with C-60 by [4 + 2] cycloaddition to form the cyclohexene-annulated intermediate, and subsequent intramolecular syn-elimination of the phosphodiester affords the cyclohexadiene-annulated fullerene derivative as the precursor for the open-cage fullerene.