Water-soluble calix[n]arenes as receptor molecules for non-polar substrates and inverse phase transfer catalysts

Water-soluble calix[n]arenes are powerful receptors for non-polar substrates in aqueous solution. The inclusion of the guests is studied by 1H NMR titration experiments and molecular modeling studies combined with ab initio NMR shift calculations. The complexation is mainly enthalpically driven. The tested water-soluble calix[n]arenes are promising candidates for carrier molecules for the transport of non-polar substrates through bulk water as well as inverse phase transfer catalysts as proven for the Suzuki coupling of iodobenzene with phenyl boronic acid. In all cases the efficiency of the tested macrocycles is higher than that for β-cyclodextrin.