RESUMO
Selective functionalization of fullerenes is an important but challenging topic in fullerene chemistry and synthetic chemistry. Here we present the first example of catalytic system-controlled regioselective 1,2- and 1,4-addition reactions for the flexible and efficient synthesis of novel 1,2- and 1,4-carbocycle-fused fullerenes via a palladium-catalyzed decarboxylative carboannulation process.
RESUMO
An interrupted N-heterocyclic carbene-catalyzed radical coupling strategy is disclosed for efficient alkylation and arylation of [60]fullerene. This novel and general strategy bridges the gap between organocatalytic radical cross-coupling and functionalization of fullerenes. Readily available feedstocks, remarkably broad substrate scope and functional group compatibility, and convenient late-stage nanomodification of complex molecules make this strategy with incomparable diversity and practicality in the synthesis of monoalkylated and -arylated fullerenes.
RESUMO
Herein, we report divergent additions of 2,2'-diazidobiphenyls to C60 and Sc3 N@Ih -C80 . In stark contrast to that of the previously reported bis-azide additions, the unexpected cascade reaction leads to the dearomative formation of azafulleroids 2 fused with a 7-6-5-membered ring system in the case of C60 . In contrast, the corresponding reaction with Sc3 N@Ih -C80 switches to the C-H insertion pathway, thereby resulting in multiple isomers, including a carbazole-derived [6,6]-azametallofulleroid 3 and a [5,6]-azametallofulleroid 4 and an unusual 1,2,3,6-tetrahydropyrrolo[3,2-c]carbazole-derived metallofullerene 5, whose molecular structures have been unambiguously determined by single-crystal X-ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole-derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the [5,6]-isomer 4 to the [5,6]-isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between [5,6]- and [6,6]-isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.
RESUMO
Herein, a concise and robust approach for the highly efficient assembly of [60]fullerene-fused tricyclic scaffolds has been developed through a palladium-catalyzed cascade [2 + 2 + 2] annulation process. Diverse tricyclic scaffolds incorporating various ring sizes (6-19 membered) and types (carbocycles and N- and O-heterocycles) can be expediently constructed in a single-step transformation.