Microwave irradiation assisted synthesis, alkylation reaction, and configuration analysis of aryl pyrogallol[4]arenes

A series of aryl pyrogallol4]arenes were efficiently synthesized in excellent yields by cyclocondensation of pyrogallol with aromatic aldehydes under microwave irradiation. The structures of aryl pyrogallol4]arenes were confirmed by characterization of their acylated derivatives. Under microwave irradiation, alkylation reactions of aryl pyrogallol4]arenes with some alkylating reagents such as n-butyl iodide, benzyl chloride, and ethyl α-chloroacetate were also finished quickly to yield fully O-alkylated products. The ¹H NMR spectra and crystal structures showed that the acylated and alkylated aryl pyrogallol4]arenes existed mainly in rctt (cis-trans-trans) configuration.