Synthesis Of Calix[4]arene Esters And Their Esterification Of Alcohols Under Neutral Conditions

This paper reports synthesis and application of the derivatives of calix[4]arene. According to the literature procedure, the compound 5,11,17,23-tetra-tert-butyl-25,26, 27,28-tetra-hydroxycalix[4]arene and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra (chloroformyl methoxy)calix[4]arene was synthesized. We attempted to use them as platforms to synthesize cyclic tetrapeptide. Although the target compound was not yielded, we found new applications for calix[4]arene esters. And we synthesized another four calix[4]arene esters. These esters were 5,11,17,23-tetra-tert-butyl-25,27- dibenzoyloxy-26,28-dihydroxycalix[4]arene, 5,11,17,23-tetra-tert-butyl-25,27-di(2- chloro-benzoyloxy)-26,28-dihydroxycalix[4]arene, 5,11,17,23-tetra-tert-butyl-25,26, 27,28-tetra(3,5-bismethoxy-benzoyloxy)calix[4]arene and 5,11,17,23-terea-tert- butyl-25,26,27,28-tetra(3,5-bisphenylmethoxy-benzoyloxy) calix [4]arene. We found that the ester 5,11,17,23-terea-tert-butyl-25,26,27,28-tetra(3,5-bisphenylmethoxy- benzoyloxy)calix[4]arene easily reacted with methanol, ethanol, isopropanol, isobutanol, isoppentyl alcohol and benzyl alcohol without any catalysts. The corresponding esters were obtained in high yields (73-90%) The transesterificaiton were completed within 6-36 hours. But when calix[4]arene esters reacted with sterically hindered alcohols, both the yields and the reaction rates were not satisfactory. Analogously, the calix[4]arene ester 5,11,17,23-tetra-tert-butyl- 25,26,27,28-tetra(3,5-bismethoxy-benzoyloxy)calix[4]arene easily transesterified methanol, ethanol without any catalysts. This represents a new type of transesterification.