Nitration of thiacalix[4]arene derivatives

A direct nitration of the upper rim of thiacalix[4]arenes is not possible due to the undesirable oxidation of the sulphur atoms during the nitration step leading to very complicated reaction mixtures. On the other hand, thiacalix[4]arene derivatives can be at first transformed intentionally to the highest oxidation state—sulfones, and subsequently ipso-nitrated using 100% HNO3 in CF3COOH. This procedure gives smoothly mono- or dinitro-derivatives in acceptable yields which opens the way for further derivatisation of the upper rim of thiacalixarenes.