Synthesis and characterization of new calixarenes from bisphenol A

The synthesis of bisphenol A-derived calixarenes has been studied by changing the protecting group of the phenol moiety and reaction conditions. Depending on the protecting groups, the corresponding calix[6,7,8]arenes are obtained in different ratios. For example, when mono-p-tert-butyldimethylsilyl-protected bisphenol A is treated with paraformaldehyde and a catalytic amount of aqueous KOH in refluxing p-xylene with a Dean-Stark water collector for 36 h, the corresponding calix[8]arene, calix[7]arene, and calix[6]arene are produced and separated in the ratio of about 3 : 2 : 1 and with overall 63% yield. The calixarenes are characterized by NMR spectroscopy and mass analysis. The X-ray crystal structure of the calix[8]arene shows a pleated loop conformation, stabilized by intramolecular hydrogen bonding between the inner phenolic hydroxy groups.X113sciescopu