Convenient regioselective functionalization at the upper-rim of p-tert-butylcalix[8]arene through a protection–deprotection procedure

A viable method to obtain calix[8]arenes selectively functionalized at the upper rim of 1,5-aromatic rings is reported. The procedure relies on protected, readily accessible 1,5-xylylene-bridged derivatives, which are easily deprotected by hydrogenolysis. The method allowed the synthesis of the first examples of calix[8]arenes partially substituted with p-nitro, p-amino, quinone and hydroquinone functionalities.