Calix[4]resorcinols containing acetal fragments

Abstract

Recently the chemistry of calixarenes attracted considerable interest of chemists. Compounds of this type are easily obtained through condensation of phenols with aldehydes. They readily undergo functionalization and are of obvious interest as basic compounds for the synthesis of the spatially organized structures of new type [1–3]. Specifically, calixarenes having acetal fragments on the upper rim of the molecule are very promising substances since they can provide a basis for design of container and tubular structures by reaction with polyphenols molecules. Recently we reported the first example of calix[4]resorcinols derivatives aminomethylated on the upper rim and containing acetal fragments [4]. In this study functionalized secondary amine III, in which acetal and amino groups were separated by two carbon atoms, was involved into the Mannich reaction with calixarenes. Compound III was obtained as a result of successive interaction of isobutanal I with ethylamine hydrochloride and methanol without intermediate isolation of aldehyde II. By the reaction of aminoacetal III with paraformaldehyde and calixarenes IVa–IVc in the ratio 4 : 4 : 1 target products Va–Vc were obtained containing four acetal fragments in the calixarene matrix (Scheme 1).