Albert Artigas, Anna Pla-Quintana, Agustí Lledó, Anna Roglans, and Miquel Solà, members of the DiMoCat group of the Institute of Computational Chemistry and Catalysis, have developed a synthetic method to generate open-cage fullerenes in a catalytic process. The Rh(I) catalyst employed is able to promote not only the [2+2+2] cycloaddition reaction but also the subsequent ring expansion, delivering an open-cage fullerene derivative in a single step without the need for photoexcitation. Molecular surgeryon fullerenes (i.e. preparation of endohedral fullerenes by partial break up and subsequent reassembly of the aromatic Csp2cage) requires lengthy multistep reaction sequences. The methodology described enables both the functionalization of C60and the formation of the 8-membered ring orifice in a single synthetic operation, thus streamlining the overall process.The obtained open-cage fullerenes can be derivatized by Suzuki-Miyaura cross-coupling, or subjected to ring expansion to deliver a 12-membered ring orifice in the fullerene structure. The complete mechanism of this transformation has been rationalized by DFT calculations, which indicate that, after [2+2+2] cycloaddition, the cyclohexadiene-fused intermediate evolves into the final product through a Rh-catalyzed di-p-methane rearrangement followed by a retro-[2+2+2] cycloaddition.
The paper has been published as a hot paper in Chem. Eur. J. and can be found in the following link Chem. Eur. J 2018, 24, 10653-10661. The motivation of the work is discussed in an open access cover profile. The front cover of the issue has been dedicated to this work.