Phosphine‐Mediated Dimerization of Open‐[60]Fullerenes.

By a reaction of trimethylphosphine with an open‐[60]fullerene, corresponding dimers could be generated via two‐fold deoxygenation processes even though the formation of β‐oxo‐phosphorous ylide is inevitable, a part of which is hydrolyzed to yield an α‐methylene carbonyl derivative. Nevertheless, Wittig reaction and aldol condensation did not proceed well, indicating the presence of an unknown dimerization pathway. In the ylide formation, 1‐phosphonium‐3‐carbabetaine was previously proposed as a key intermediate. Upon assuming that the betaine also participates in the dimerization process, we examined a possible reaction pathway computationally. As the results, the betaine formed by a reaction with the first phosphine was suggested to undergo nucleophilic addition to an unreacted molecule of the open‐[60]fullerene, yielding an epoxide dimer which is then deoxygenated by the second phosphine to furnish the desired open‐[60]fullerene dimer. [ABSTRACT FROM AUTHOR]