Synthesis of Calix[6]arenes Partially Functionalized at the Upper Rim

Several new examples of calix[6]arenes selectively functionalized at the upper rim are reported. Starting from calix[6]arenes 1,3,5-tri-, 1,2,4,5-tetra- and 1,2,3,4,5-pentaalkylated at the lower rim, it is possible to isolate macrocycles 2,4,6-tri-, 3,6-di- and 6-mono functionalized at the upper rim (18-94% yield) with nitro, formyl, bromo, chloromethyl and 2-propenyl groups. Modifications of these moieties allow the synthesis of macrocycles bearing amino, amido, hydroxymethyl, carboxy, cyano and chloromethyl functions which can be used for further transformation and preparation of new molecular receptors, based on calix[6]arenes, which have different geometries. Examples of di- and triquinones on the hexameric macrocycle are also reported