Copper-Catalyzed N-Heteroannulation of [60]Fullerene with Aryl Sulfonamides and Paraformaldehyde: Synthesis and Functionalization of [60]Fullerene-Fused Imidazolidines.

The Cu(II)-catalyzed N-heteroannulation reaction of [60]fullerene (C60) with aryl sulfonamides and paraformaldehyde has been disclosed for the synthesis of diverse C60-fused imidazolidines, of which one or both of the ArSO2 moieties could be removed selectively. Further transformations into the unexpected bicyclic 1,2,3,4-adduct and C60-fused imidazolidinium iodide salt have also been demonstrated. A plausible reaction mechanism is proposed on the basis of control experiments. C60-fused imidazolidinium iodide has been employed as an additive in the PC61BM layer of inverted planar perovskite solar cells to increase power conversion efficiency.