Synthesis and cation complexation selectivity of bis(syn-proximally) functionalized calixarenes

Article abstract of DOI:10.1002/recl.19921111203

A general method has been developed for the preparation of bis(syn-proximally) functionalized calix<4>arenes (6,8-10).Starting from p-tert-butylcalix<4>arene 1a and calix<4>arene 1b syn-proximally dialkylated calix<4>arenes 2a and 2b, 4, and 5, respectively, were obtained by treatment with 4.2 equiv of NaH and 2.2 equiv of alkylating reagent in DMF.The syn-proximal substitution pattern was unequivocally proven by an X-ray structural determination of 2b.Furthermore the influence of different bases on the functionalization of the free hydroxyl groups of 2b with chloroacetone was studied.Cs2CO3 as the base gave the bis(syn-proximally) functionalized calix<4>arene 6 in the highest yield (82percent).Cation complexation studies, with the picrate extraction method, showed that subtle changes in the regioselective functionalization influences the selectivity for Na+ considerably.