H-Bond-Assisted Regioselective (cis-1) Intramolecular Nucleophilic Addition of the Hydroxyl Group to [60]Fullerene

Abstract

The one-step reaction of 2,6-dihydroxyphenylmethyl ketone and sarcosine with [60]fullerene in refluxing chlorobenzene affords, in a totally regioselective process, the cis-1 bicyclic-fused organofullerene through a new intramolecular nucleophilic addition of one hydroxy group to the fullerene double bond. Experimental findings reveal the presence of a methyl group on C-2 of the pyrrolidine ring as an essential requirement for the cyclization process, whereas the existence of a H-bond between a second hydroxylic group and the nitrogen atom of the pyrrolidine ring seems to favor the approaching geometry without determining the reaction outcome. Theoretical calculations using the two-layered ONIOM approach and density functional theory support the experimental findings, predicting the strong impact that the presence of the methyl substituent on the C-2 of the pyrrolidine ring has on the molecular geometry and, hence, on the intramolecular cyclization process.