Fullerene derivatives bearing a phosphite ylide, phosphonate, phosphine oxide, and phosphonic acid: Synthesis and reactivities

Treatment of phosphites (P(OR)₃) and MeO₂CCCCO₂Me with C₆₀ affords the corresponding fullerene derivatives (1, R = Me; 2, R = Et; 3, R = n-Bu) consisting of a phosphite ylide group and a cyclopropane ring on the fullerene moiety in high yields. NMR data indicate that all phosphite ylides 1-3 exist as mixtures of E and Z isomers. Under similar reaction conditions, the reaction of phosphinite PPh₂(OMe) and MeO₂CCCCO₂Me with C₆₀ gives ylide 4. Ylides 1-3 readily undergo hydrolysis with HBr to give corresponding phosphonates 5-7 in excellent yields, while ylide 4 reacts with hydrobromic acid to afford phosphine oxide 8. A mechanism is proposed to account for the formation of these phosphonate derivatives. Further treatment of phosphonate derivative 5 with trimethylsilyl iodide followed by water gave phosphonic acid derivative 9 in 83% yield.