TheBingel reaction infullerene chemistry is afullerenecyclopropanation reaction to amethanofullerene first discovered by C. Bingel in 1993 with thebromo derivative ofdiethyl malonate in the presence of abase such assodium hydride orDBU.[1] The preferred double bonds for this reaction on the fullerene surface are the shorter bonds at the junctions of two hexagons (6-6 bonds) and the driving force is relief ofsteric strain.
The reaction is of importance in the field of chemistry because it allows the introduction of useful extensions to the fullerene sphere. These extensions alter their properties, for instance solubility and electrochemical behavior, and therefore widen the range of potential technical applications.
Thereaction mechanism for this reaction is as follows: abase abstracts the acidic malonate proton generating acarbanion orenolate which reacts with the electron deficient fullerenedouble bond in anucleophilic addition. This in turn generates a carbanion which displaces bromine in anucleophilic aliphatic substitution in anintramolecular ringcyclopropane ring closure.
The Bingel reaction is a popular method in fullerene chemistry. Themalonate (functionalized with thehalide atom) is often obtainedin situ in a mixture ofbase andtetrabromomethane oriodine.[2] The reaction is also known to take place with theester groups replaced byalkyne groups indialkynylmethanofullerenes.[2]
An alternative to the Bingel reaction is a fullerenediazomethane reaction. N-(Diphenylmethylene)glycinate Esters[3] in a Bingel reaction take a different conjugate course and react to a fullerenedihydropyrrole.
Protocols exist for the removal of the methano group based onelectrolytic reduction[4][5] or amalgamatedmagnesium.[6]