A Solid‐State Intramolecular Wittig Reaction Enables Efficient Synthesis of Endofullerenes Including Ne@C(60), (3)He@C(60), and HD@C(60)

An open‐cage fullerene incorporating phosphorous ylid and carbonyl group moieties on the rim of the orifice can be filled with gases (H(2), He, Ne) in the solid state, and the cage opening then contracted in situ by raising the temperature to complete an intramolecular Wittig reaction, trapping the atom or molecule inside. Known transformations complete conversion of the product fullerene to C(60) containing the endohedral species. As well as providing an improved synthesis of large quantities of (4)He@C(60), H(2)@C(60), and D(2)@C(60), the method allows the efficient incorporation of expensive gases such as HD and (3)He, to prepare HD@C(60) and (3)He@C(60). The method also enables the first synthesis of Ne@C(60) by molecular surgery, and its characterization by crystallography and (13)C NMR spectroscopy.