Novel Bismethanofullerenes and Ethenofullerene from the Reaction of Propiolates with C(60) in the Presence of Triphenylphosphine

Novel acid-catalyzed rearrangement of methanofullerenes bearing an alpha-ylidic ester to cyclopentanofullerenes: a vinyl cyclopropane-type ring expansion

A novel acid-catalyzed ring expansion of methanofullerenes bearing an alpha-ylidic ester has been investigated. Treatment of dialkyl acetylenedicarboxylate and tricycloalkylphosphine with C(60) led to the isolation of a methanofullerene ylide after passing the reaction mixtures through a basic alumina column. If the reaction mixture was passed through a silica gel column, a cyclopentanofullerene was isolated instead. These new cyclopentanofullerenes consisted of a fused cyclopentanone ring bearing an alpha-hydroxy ester and a phosphonium ylide and were confirmed by their NMR, mass, and X-ray diffraction data. The cyclopentanofullerenes were formed by the ring expansion of the corresponding methanofullerenes in the presence of silica gel. The ring expansion also proceeded by treating methanofullerene with acetic acid in chloroform. On the other hand, the methanofullerenes from RO(2)CCCCO(2)R, PAr(3), and C(60) were stable in silica gel. However, upon heating with acetic acid at 50 degrees C, they underwent ring expansion and dephosphination to give cyclopentenofullerenes. An implicit vinyl cyclopropane ring expansion mechanism was proposed to account for this novel acid-catalyzed rearrangement.

Fullerene Derivatives Bearing a Phosphite Ylide, Phosphonate, Phosphine Oxide, and Phosphonic Acid: Synthesis and Reactivities

Treatment of phosphites (P(OR)(3)) and MeO(2)CCCCO(2)Me with C(60) 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 PPh(2)(OMe) and MeO(2)CCCCO(2)Me with C(60) 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.

Synthesis and Chemistry of Fullerene Derivatives Bearing Phosphorus Substituents. Unusual Reaction of Phosphines with Electron-Deficient Acetylenes and C(60)

A unique method to introduce phosphorus substituents onto C(60) is based on the reaction of phosphines with acetylenes and C(60). Treatment of C(60) with phosphines (PR(3)) and electron-deficient acetylenes (A) in toluene at ambient temperature gave fullerene derivatives (1, R = C(6)H(5) and A = MeO(2)CC&tbd1;CCO(2)Me; 2, R = C(6)D(5) and A = MeO(2)CC&tbd1;CCO(2)Me; 3, R = C(6)H(5) and A = EtO(2)CC&tbd1;CCO(2)Et; 4, R = p-CH(3)C(6)H(5) and A = MeO(2)CC&tbd1;CCO(2)Me; 6, R = C(6)H(5) and A = trans-MeO(2)CC&tbd1;CCH=CHCO(2)Me) consisting of a phosphorus ylide group and a cyclopropane ring on the fullerene moiety in good to excellent yields. The structures of these ylide derivatives are determined on the basis of their spectral data and single-crystal X-ray diffraction measurements. All these ylides show temperature-dependent NMR spectra that can be rationalized on the basis of interchange between two Z,E isomers and restricted rotation of the substituents on the fullerene moiety. Based on the known chemistry of phosphines and acetylenes, we propose a mechanism to account for the formation of these ylide derivatives. Phosphine ylides 1 and 4 readily undergo protonation and decarboxylation in the presence of acid to give phosphonium salts 7 and 8, respectively.