Endohedral Metal-Induced Regioselective Formation of Bis-Prato Adduct of Y₃N@<i>I</i>_<i>h</i>‑C₈₀ and Gd₃N@<i>I</i>_<i>h</i>‑C₈₀

Regioselective bisaddition of M₃N@<i>I</i>_<i>h</i>-C₈₀ (M = Y, Gd) was observed for the first time in the Prato reaction with <i>N</i>-ethylglycine and formaldehyde. The main kinetic bisadduct of Y₃N@C₈₀ was determined to be a [6,6],[6,6] adduct by ¹H and ¹³C NMR and vis/NIR spectroscopy, and it converted to a mixture of regioisomers upon heating via a sigmatropic rearrangement. The main kinetic bisadduct of Gd₃N@C₈₀ (the [6,6],[6,6] adduct on the basis of vis/NIR data) existed stably under thermal conditions without isomerization. The likely position of the second addition of the Gd₃N@C₈₀ bisadduct was predicted by DFT calculations