Electrochemical Alkylations Of [60] Fulleroindoline With Bulky Alkyl Bromides

Fullerene derivatives have captured wide attention due to their potential applications in biological science,materials science and many other fields.In this connection,chemists have made considerable efforts to modify fullerenes and have found many methods and strategies to synthesize fullerenes derivatives.Among the various methods,electrosynthesis is an efficient method for the preparation of fullerene derivatives,which is more and more popular because of its mild reaction conditions,good regioselectivity and relatively high yield.Moreover,some products with novel addition patterns can be obtained by electrosynthesis due to the unique electrochemical properties of fullerenes and their derivatives.It can be found that the selective formation for fullerene derivatives with different addition patterns mostly depends on the structures and electronic properties of the investigated fullerene-fused heterocyclic derivatives from previous studies.The steric effect of electrophiles is also an important factor affecting the addition pattern,thus the choice of electrophiles is particularly important.Firstly,the reaction of dianionic[60]fulleroindoline with 2,4,6-tris(bromomethyl)mesitylene was studied.By controlling the amount of the electrophile and reaction time,hydroalkylated and dialkylated 1,2,3,16-addcuts could be selectively obtained.Subsequently,bulkier diphenylbromomethane was used as an electrophile.When the amount of diphenylbromomethane was low,the hydroalkylated 1,2,3,16-adduct was obtained.However,when the amount of diphenylbromomethane was increased,the reaction time was prolonged,and a small amount of NaH was added,a major 1,4,9,12-adduct containing two Ph2CH groups was generated accompanied by a small amount of dialkylated 1,2,3,16-adduct were obtained.When 9-bromofluorene was used as the electrophile,the result was similar to that of diphenylbromomethane;and dialkylated 1,4,9,12-adduct could also be obtained,but the reaction selectivity was poor.Finally,the reason of poor selectivity was explained by theoretical calculations.