Unexpected Formation of Pyrazoline-Fused Metallofullerenes from the Multicomponent Cascade Reaction of Sc 3 N@ I h -C 80 with Tetrazines, Water, and Oxygen.

The multicomponent cascade reaction of Sc 3 N@ I h -C 80 with 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazines, water, and oxygen unexpectedly affords the pyrazoline-fused Sc 3 N@ I h -C 80 derivatives. The obtained endohedral metallofullerene derivatives have been characterized by various spectral means, and their structures have been unambiguously established by single-crystal X-ray crystallography. A possible reaction mechanism via a complicated sequence of Diels-Alder reaction, retro Diels-Alder reaction, hydration, rearrangement, and dehydrogenation processes is proposed for the formation of pyrazoline-fused metallofullerenes.