Calix[4]arene (2), readily accessible from p-tert-butylcalix[4]arene (l), is shown to react smoothly with formaldehyde and secondary amines to yield Mannich bases (3), which can be converted to the corresponding quaternary salts (4). Treatment of the quaternary salt with 2 equiv of a nucleophile (the first equivalent acting as a base) yields a para substituted calix[4]arene via a putative calixarene p-quinone methide intermediate. By means of this sequence of reactions a variety of functionalized calixarenes (6) have been prepared, including those carrying C N , OCH3, N,, SEt, CH(CO,Et),, CH(NO,)CO,Et, and imidazolyl functions. Of particular interest are p-(2-aminoethyl)calix[4]arene (7b), obtained by reduction of p-(cyanomethyl)calix[4]arene (6a), and the amino calixarenes obtained directly from the Mannich reaction. On the basis of N M R , IR, and UV measurements, the aminocalixarenes a r e shown to exist as zwitterions in polar organic solvents and as aminophenols in nonpolar solvents.The interaction of the p-bromobenzenesulfonate of p-(2-aminoethyl)calix[4]arene (1 1) with several metal ions, including Ni2+, Cu2+, Pd2+, Co2+, and Fez+, has been investigated. The spectral and chemical characteristics of these complexes are interpreted as indicating that 11 is more flexible than had been anticipated, behaving more like four independent ethylamine moieties than a single trialkylenetetramine moiety.
Synthesis of Functionalized Calixarenes: the p-Quinone MethideRoute. Calixarenes a r e cavity-containing macrocyclic compounds t h a t have attracted our interest because of their potential for forming host-guest complexes and, if appropriately functionalized,
