The photochemical reaction of [60]fullerene with RNMe2 (R = Ph and Me) gives an adduct (1, R = Ph; 2, R = Me) formed by the addition of an a-C-H bond of the amine to a 6/6 ring junction of [60]fullerene; 2 on further irradiation in the presence of [60]fullerene is converted to the pyrrolidine derivative 3 and 1,2-H2C60.

A novel method for the construction of a fused cyclohexadiene ring on C60 based on a nickel-promoted [2+2+2] cycloaddition of 1,6-diynes is described. Treatment of C60 with terminal 1,6-diynes (HC⋮CCH2)2X) in the presence of NiCl2(PPh3)2, Zn, and PPh3 at 90 °C in toluene afforded [2+2+2] bicyclic hexadiene derivatives (X = C(CO2Me)2 (2a), C(CO2Et)2 (2b), C(COMe)2 (2c), CH2 (2d), O (2e), NSO2-p-C6H5CH3 (2f), C(SO2Ph)2 (2g), and (2h) in good yields. Spectral data for products 2a − h indicated that the cycloaddition of diynes to C60 occurs across a 6,6-ring junction on the fullerene. On the basis of the established chemistry of metal-mediated [2+2+2] cycloaddition, a mechanism is proposed to account for the present nickel-mediated reaction. All the hexadiene derivatives 2a−h in solution are readily oxidized by molecular oxygen in the presence of light at ambient temperature. The oxidation process of compound 2a in chloroform-d was monitored by 1H NMR spectroscopy, and the results showed that 2a first reacted with molecular oxygen to form peroxide 3 and was subsequently converted to dialdehyde 4 and C60-containing polymeric material. Photochemical properties of some cyclohexadiene derivatives were then investigated. Upon irradiation (350 nm), compounds 2a−c, 2f, and 2h readily underwent [4+4] cycloaddition to give the corresponding bisfulleroids 5a−c, 5f, and 5h in excellent yields.

Treatment of [60lfullerene with HC=CC02R in the presence of P(Cy), at ambient temperature affords a cyclotrimerization product (R = Et, 1; Me, 2) which results from a head-to-tail addition of two HC-CC02R units to a 6-6 ring junction of [60lfullerene based on the observed spectral data. Functionalization of fullerenes by cycloaddition reactions provides important routes for the preparation of [60]fullerene derivatives.ld Various types of [l + 2],l [2 + 2],2 [3 + 2],3 [4 + 214,5 and [8 + 216 cycloaddition to fullerenes have been

Treatment of RCH2CrCCOX with [6O]fullerene in the presence of tricyclohexylphosphine (PCy,) afforded a [2 + 21 cycloaddition product (1: R = H, X = OMe; 2: R = Bu, X = OMe; 3: R = X = Me which resulted from addition of the P,y-carbons of RCH2CrCCOX to the carbon-carbon double bond across a 6/6 ring junction of [60lfuIIerene.Cycloadditions to fullerenes provide important routes for the preparation of fullerene derivatives. [1][2][3][4][5][6][7] The mass spectral data of this product showing a molecular ion at m/z 818 is consistent with a monoadduct of methylbut-2-ynoate to [60]fullerene. The 1H NMR spectrum exhibits a singlet, a doublet and a triplet at 6 3.93,4.63 and 7.82 assigned to the protons of the methyl, methylene and alkene groups, respectively, on the alkylidene cyclobutane ring. Evidence for [2 + 21 cycloaddition across the P,y-carbons of but-2-ynoate and across a 6/6 ring junction on [60]fullerene is provided by the observed magnetic equivalency of the two methylene protons, which exhibit a weak allylic coupling (J 2.7 Hz) with the alkenic proton. The observed number of 13C NMR signals, which indicate the presence of C, symmetry, is in agreement with the proposed structure 1. Further proof of a cyclobutane moiety in 1 comes from the results of a l3C DEPT experiment that led us to assign the resonances for the methylene carbon, the two fused quaternary sp3 carbons on the [60]fullerene fragment and the exocyclic tertiary alkenic carbon at 6 47.58, 69.30, 77.50 and 143.59, respectively. The observed highly deshielded NMR signal of the alkenic proton at 6 7.82, which is shifted ca. 2 ppm downfield relative to a normal a-proton of a cu,p-unsaturated ester, suggests that this proton is orientated towards a fivemembered ring (structure A).The strong paramagnetic current associted with the five-membered rings of fullerenes has been shown to cause downfield shifts of the NMR signals of protons oriented toward them.* Based on the observed chemical shift of the alkenic proton, the ester group is assigned cis to the methylene group on the 4-membered ring.The reaction of methyl oct-2-ynoate with [60]fullerene in the presence of PCy3 at 70 "C also gave a [2 + 21 cycloaddition product 2$ in 13.4% yield. The 1H NMR signal at 6 7.67 for the 1 R = H , X = O M e 2 R = MeCH2CH2CH2, X = OMe 3 R = X = M e alkene proton exhibits an allylic coupling of J 2.4 Hz with that of the methine proton at 6 4.53 on the 4-membered ring. This observation indicates that products 1 and 2 have a similar structures. However, unlike 1, product 2 possesses an asymmetric centre at the methine carbon leading to the diastereotopic nature of the protons in each methylene group of the butyl chain in the lH NMR spectrum. Furthermore, the asymmetric centre reduces the symmetry of 2 to C1, yielding separate signals for each carbon in the I3C NMR spectrum. To date, only a few [6O]fullerene adducts that display C1 symmetry have been reported.4~9 Similarly, hex-3-yn-2-one reacts with [60]fullerene in the presence of PCy3 at 70 "C to give 35 in 17.3% ...

Endo‐tetrahydrodicyclopentadiene (IV) is isomerized in the presence of trifluoromethanesulfonic acid (I) to give exo‐tetrahydrodicyclopentadiene (V). At higher acid concentrations, the isomerization occurs instantaneously. The preferred molar ratio of I to IV is in the range 0.05 to 4.0 and the preferred temperature is in the range 20°C to 100°C. Under these conditions, virtually no admantane is formed and undesirable C10H16 isomers can be reduced to a minimum. Besides the homogeneous system, the acid catalyst also works in a two‐phase heterogeneous system. The spent acid in the heterogeneous system can be reused without losing catalytic effectiveness.