The first N-tritylpyrrolidino derivatives of D-3h (78:5) SC3N@C-78 were successfully synthesized and isolated. The addition sites for the two nearly equivalent kinetic monoadducts 1a and 1b are across two different 6,6 junction sites on the SC3N@C78 cage that are offset from the horizontal plane defined by the SC3N cluster. The adducts were characterized by NMR experiments, DFT calculations and X-ray crystallographic analysis of SC3N@C-78 derivative 1a. A unique finding of this study is the regiocontrol of adduct docking by the internal Sc3N cluster.