<i>Ipso</i> ‐Nitration of <i>p‐tert‐</i> Butylcalix[4]arenes with <i>tert‐</i> Butyl Nitrite

Abstract In order to develop new ipso ‐nitration reagents, tert ‐butyl nitrite has been used to ipso ‐nitrate a variety of p‐tert ‐butylcalix[4]arene derivatives. The nitration experiments showed that the ipso ‐nitration with tert ‐butyl nitrite can be executed in moderate‐to‐high yields (up to 95%). The optimal reaction solvent, temperature, time, and tert ‐butyl nitrite amount for ipso ‐nitration of 1a are 1,2‐dichloroethane, 80 °C, 24 h, and 20 equiv., respectively. The p‐tert‐ butylphenoxy unit carrying an electron‐donating substituent can undergo ipso ‐nitration, and that carrying an electron‐withdrawing substituent can't. Calix[4]arene conformation can affect the ipso ‐nitration rate, but can't determine whether the ipso ‐nitration takes place or not. The nitration results confirm that tert ‐butyl nitrite can be used as an alternative and efficient reagent for the ipso ‐nitration of p‐tert ‐butylcalix[4]arene derivatives.