Solvent-free reactions of C-60 with active methylene compounds, either with or without carbon tetrabromide, in the presence of bases under high-speed vibration milling conditions

Solvent-free reactions of C-60 with active methylene compounds, either with or without carbon tetrabromide ( CBr4), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C-60 with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na2CO3 to afford cyclopropane derivative 2. In the presence of CBr4, methanofullerenes 2, 7, 8 and 9 could be obtained by the direct reaction of C-60 with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na2CO3. More interestingly, 1,4-bisadducts 10 and 11 were produced by the reaction of C-60 with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na2CO3 under HSVM conditions. On the other hand, dihydrofuran-fused C-60 derivatives 18, 19 and 20 were obtained from the reaction of C-60 with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives 27, 28 and 29. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism.