Multiply exo-Methylated Corannulenes.

The curved π-conjugated surface of bowl-shaped corannulene is multiply methylated to form exo-di-, tetra-, and hexamethylated corannulenes. The multimethylations have become possible by in-situ iterative reduction/methylation sequences that involve the reduction of corannulenes using sodium to form the anionic corannulene species and the subsequent SN2 reaction of the anionic species with reduction-resistant dimethyl sulfate. X-ray diffraction analyses, NMR, MS, UV-Vis measurements, and DFT calculations have revealed the molecular structures of the multi-methylated corannulenes and the sequence of the multi-methylation. This work has the potential to contribute to the controlled synthesis and characterizations of multi-functionalized fullerenes.