Selective ipso-nitration of tert-butylcalix[4]arene 1,3-diethers: X-ray structure of an unexpected side product

1,3-Diether derivatives of tert-butylcalix[4]arene can be selectively nitrated at the para-position of the phenolic units. In this way clix[4]arenes bearing tert-butyl and nitro groups at the upper rim in alternating sequence are easily available in yields up to 75% Ipso-attack may also occur ortho to the phenolic hydroxy group leading in a side reaction to macrocyclic compounds with two 6-nitrocyclohexa-2,4-dienone units. Both types of structures were established by single crystal X-ray analysis.