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

The Cu(II)-catalyzed <i>N</i>-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.