Stereoselective synthesis of N-ethyl-2-arylvinyl-5-methyl fulleropyrrolidines: reaction of [60]fullerene with aromatic aldehydes and triethylamine/diethylamine in the absence or presence of manganese(iii) acetate.

The reaction of [60]fullerene with aromatic aldehydes and triethylamine/diethylamine in the absence or presence of manganese(iii) acetate under air conditions afforded a series of N-ethyl-2-arylvinyl-5-methyl fulleropyrrolidines in moderate to good yields, which would be difficult to synthesize by reported protocols. The in situ generation of arylvinyl aldehydes by the aldol reaction of aromatic aldehydes with acetaldehyde from an unusual C-N bond cleavage of triethylamine/diethylamine played a crucial role in the successful preparation of the corresponding fulleropyrrolidines. Depending on the reaction conditions, both cis and trans isomers of fulleropyrrolidines could be selectively synthesized. Cis isomers as major products could be obtained by reacting with triethylamine at 160 °C without the addition of manganese(iii) acetate, while trans isomers as major products, with rare exceptions, could be observed via the reaction with diethylamine at 120 °C under the assistance of manganese(iii) acetate. Moreover, the in situ generated arylvinyl aldehydes displayed higher reactivity towards diethylamine as compared with aryl aldehydes, leading to the formation of arylvinyl-substituted fulleropyrrolidines. A plausible formation mechanism for fulleropyrrolidines was provided based on the experimental observations.