Tetra-O-alkylated calix[4]arenes in the 1,3-alternate conformation
摘要:
A general method has been developed for the preparation f tetra-O-alkylated calix[4]arenes in the 1,3-alternate conformation (3a,c-e) starting from p-tert-butylcalix[4]arenes 1a,b using Cs2CO3 in DMF. The 1,3-alternate conformation was unequivocally proved by an X-ray structure determination of 3a. The scope of the reaction was investigated starting from a series of diametrically di-O-alkylated calix[4]arenes 4a-e having different substituents R2 (t-Bu, CHO, NO2, Br, CN) at the para positions of the phenolic rings. The reactions of 4a-d (R2 = t-Bu, CHO, NO2, Br) yielded the corresponding tetra-0-alkylated calix[4]arenes in the 1,3-alternate conformation 5a-d (51-73%). However, the dicyanocalix[4]arene 4e gave the partial cone conformer 6 as the major reaction product.
A series of mixed [2 + 2'] p-tert-butylcalix[4]arene have been synthesised by selective 1,3-dialkylation of phenolic groups using various alkylating agents such as benzyl bromide, methyl iodide, ethyl bromoacetate, and 2-methoxyethyl tosylate. The extraction and complexation properties of the synthesized calixarenes towards alkali and alkaline earth metal cations have been investigated in acetonitrile
A new fluorescent chemosensor based on calix[4]arene bearing four iminoquinoline subunits on the upper rim was conveniently synthesized, which showed a remarkable enhanced fluorescent intensity in the presence of Cu(2+) ion and a high selectivity toward Cu(2+) ion over a wide range of tested metal ions in acetonitrile.