AbstractThe reaction of C70 with CH2(PO3Et2)2 or CH2(PO3Et2)CN in the presence of NaH has been reinvestigated. The reaction of C70 with the former phosphonate affords five products. Products 1–3 have molecular structures C70>CH(PO3Et2), whereas products 4 and 5 have molecular structures C70>C(PO3Et2)2. In contrast, only one product 6, with a molecular structure C70>C(PO3Et2)CN, could be isolated from the reaction of C70 with CH2(PO3Et2)CN and NaH. Ultrasonication was used to shorten the reaction times and increase the product yields. No product resulting from addition to the C7–C21 bond of C70 was observed in either cycloaddition reaction. Accordingly, the previously reported major products 3 and 6, which were assigned as the C7–C21 isomers, should be reassigned as the C1–C2 isomers. This correction is very important for understanding the reactivity of C70. Our reassignments are further supported by theoretical calculations. The newly isolated minor products 1, 2, and 4 were identified as the C5–C6 isomers. The present work proves that the reactivity order of the bonds in C70 for these two reactions is C1–C2 > C5–C6. These results resolve the confusion caused by previous incorrect product assignments.