First Synthesis of Upper Rim Mono and Dinitrone Calix[4]arene Derivatives

Abstract

A new class of calix[4]arene derivatives bearing one or two nitrone groups on the upper rim has been synthesized using the oxidation of chiral imines with hydrogen peroxide. The imine intermediates were obtained via amination of the diformyl derivative. The ¹H NMR spectra and X-ray data indicated a 1,3-disubstituted cone conformation for the imine derivatives and the existence of a single (E,E) isomer. The structural identity of the nitrone derivatives was confirmed from NMR, IR and ES-MS data. Both mono and dinitrone calix[4]arenes were in E configuration.

Keywords:

• Calixarene
• Nitrone derivatives
• Synthesis
• Chiral ligands
• X-ray structure