Solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes under high-speed vibration milling

The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C-60(CH2N(CH3)CHR), R=H (4a), C6H5 (4b), pNO(2)-C6H5 (4c), p-CH3O-C6H4 (4d), p-(CH3)(2)N-C6H4 (4e)) were obtained in moderate yields from reactions of C-60 with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C-60 with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C-70 with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines. (C) 2002 Elsevier Science Ltd. All rights reserved.