Catalytic cyclopropanation of fullerene[60] with diazomethane

Abstract

The selective cyclopropanation of C 60 -fullerene with diazomethane was performed under the catalysis with Pd(acac) 2 , and individual 5,6-open and 6,6-closed cycloadducts were obtained.The deep interest attracted by methanofullerenes is due to the prospects of their application as components of energy-rich fuel and also nanomaterials for produc-tion of modern additives for highly loaded mechanisms and machines, initial substances in the synthesis of drugs [1][2][3][4][5][6][7].In 1992 first information appeared on the possibility of [2+3]-cycloaddition of diazomethane to the [6,6]-bond of the C 60 -fullerene molecule with the formation of fulleropyrazoline I that under the conditions of thermal process converted into 5,6-open [2+1]-cycloadduct [8]. At a photochemical irradiation of the fulleropyrazoline a mixture was formed of 6,6-closed and 5,6-open adducts II and III in the ratio 3:4 [9]. Fulleropyrazoline I under the action of catalytic amounts of Pd(OAc) 2 (20 mol% Pd, toluene, 20°C, 8 h) transformed into individual 5,6-open fulleroid III. On increasing the reaction time to 30 h a mixture formed of 5,6-open, 6,6-closed adducts II and III, and unindentified fullerene derivatives in the ratiõ 2:1: 1 (HPLC). At the use of a stoichiometric quantity of Pd(OAc) 2 in the reaction of C 60 -fullerene with an ether solution of diazomethane (3-4 equiv of CH 2 N 2 , toluene, 0°C) methanofullerene II formed in ~15% yield [10].Homofullerene III does not isomerize into metanofullerene II [9][10][11] in contrast to cycloadducts obtained by the cycloaddition of substituted diazomethanes or diazoacetates to C 60 -fullerene [11-17].The above described syntheses of methanofullerenes posses a number of disadvantages related to the low yields of the target [2+1]-cycloadducts or with the necessity of preliminary preparation of fulleropyrazolines that only at heating, irradiation, or under the action of transition metal complexes are converted into methanofullerenes. Besides the selective synthesis of methanofullerene II from C 60 -fullerene and diazomethane required a stoichiometric amount of Pd(OAc) 2 .Proceeding from the above and aiming at development of a preparative method of catalytic cyclopropanation of C 60 -fullerene with diazomethane with the goal of obtaining methanofullerenes in high yields we investigated this reaction using as catalysts complexes of Cu, Pd, and Rh known as the most active and selective in diazocompounds cycloaddition to olefins [18][19][20][21][22][23][24][25][26].The diazomethane reaction with C 60 -fullerene provided the highest yield of the target methanofullerenes at the use as a catalyst Pd(acac) 2 . In this connection all subsequent experiments were carried out with this complex. In the reaction of ether solution of diazomethane with C 60 -fullerene [molar ratio 1:1, 20 mol% Pd(acac) 2 , 40°C, 5 min, toluene] fulleropyrazoline I formed in ~30% yield. The addition of 1 equiv more of diazomethane in ether resulted in an increase in the fullerene conversion to 60%. After 2 h the disappearence of f...

Sulfur-Containing Homo- and Methanofullerenes: Synthesis and Study of Tribological Properties

“…As a follow-up to the ongoing work in our group [13][14][15][16][17][18][19][20] related to the selective functionalization of C 60 -fullerene with diazo compounds, we studied the catalytic cycloaddition reaction of sulfur-containing diazoalkanes generated in situ by the oxidation of hydrazones of the corresponding ketosulfides with MnO 2 to C 60 . Of the tested catalysts based on salts 2 of 11 and compounds of Cu, Pd, and Rh, the three-component catalyst prepared in situ from Pd(acac) 2 , PPh 3 , and Et 3 Al, taken in a ratio of 1:2:4, respectively, showed the highest activity in the reaction of diazoalkanes and C 60 -fullerene.…”

Carbene Additions to Fullerenes

“…They employed Pd(OAc) 2 in the reaction of ethereal diazomethane with C 60 at 0 °C and isolated the methanofullerene in 15% yield. Tuktarov and co-workers developed three-component catalytic systems Pd(acac) 2 –PPh 3 –Et 3 Al to improve the efficiencies of cycloadditions. − The formation ratio of the adducts depends on the substituents of the diazo compounds they used and the reaction conditions. When diazoesters or diazoketones were used for the three-component Pd(acac) 2 –4PPh 3 –4Et 3 Al catalytic reactions, [6,6] closed methanofullerenes were obtained exclusively in 30–60% yields.…”

Catalytic cycloaddition of diazoalkanes generated in situ to fullerene C60

“…We previously reported [4] on selective cycloaddition of diazomethane (generated in situ) to C 60 in the presence of palladium complexes. In continuation of these studies, the present communication reports on cycloaddition of alkyl(aryl)-substituted diazoalkanes to C 60 in the presence of palladium complexes, which was examined with a view to reveal the effect of diazoalkane structure on the reaction direction and develop efficient procedures for the synthesis of substituted [5,6]-fulleroids.…”