New syntheses of calixarene-p-sulphonates and p-nitrocalixarenes

Calixarene-p-sulphonates (tetramer, hexamer, and octamer) have been prepared (75-88%) and used to give p-nitrocalixarenes (15-22% yields based on the starting calixarenes). The novel nitration has two advantages: (i) calixarenes are protected from nitric acid oxidation by the electron-withdrawing sulphonate groups and (ii) the difference in the water-solubility of the p-nitrocalixarenes from the sulphonate-containing, lower nitration products, allows ready isolation of the former. The p-nitrocalixarenes thus obtained have potential as intermediates in the synthesis of a variety of functionalised calixarenes.