Regioselective Acylation And Carboxylation Of [60] Fulleroindoline Via Electrochemical Synthesis

Recently,fullerenes and their derivatives have been widely investigated and synthesized by scientists due to their potential application in material science,photovoltaic device and biological medicine etc.Until now,numerous strategies and methodologies for the surface derivatization of fullerenes have been successfully developed,including nucleophilic additions,cycloadditions,radical additions and hydrogenation.In recent years,metal-catalyzed methods have also provided the new and high efficient strategies for the functionalization of fullerenes and their derivatives.However,the aforementioned methods usually require high temperature,long reaction time,and expensive metal catalyst,which definitely limit their application in practical synthesis.Accordingly,our group introduced the electrochemical method to fulfill the surface functionalization of fullerene derivatives.Compared to traditional method,electrochemistry can not only overcome the drawbacks that classical protocols possess,but specially show its advantage on the multi-addition of fullerene derivatives.The carbonyl fullerene derivatives have attracted much attention among fullerenes and their derivatives,owing to the great synthetic potential of the carbonyl group.For instance,the carbonyl group can be oxidized to form corresponding carboxylic derivatives,or reduced to give the alcohol derivatives.Based on our previous investigation,we firstly apply the electrosynthsis on the multi-addition for[60]fullerene with different carbonyl groups.By using inexpensive and readily available acyl chlorides and chloroformates,both keto and ester groups can be easily attached onto the fullerene skeleton to afford 1,2,3,16-functionalized[60]fullerene derivatives regioselectively.In addition,a plausible mechanism for the formation of fullerenyl ketones and esters is proposed,and their further transformations under basic and acidic conditions have been investigated.Through the deuterium experiment,we have found that the proton resource for the formation of the fullerenyl proton is not from the trace amount of water exists in the water,but is from other much acidic source.Subsequently,we have investigated the reaction between the electron donating group substituted fulleroindoline and phthaloyl dichloride and obtained 1,3,4,9-dicarbonyl fullerene derivatives.In addition,a plausible mechanism is also depicted.