Alternative and Eco-Friendly Synthesis of Tetrakis(Aminomethyl)Calix-[4]-Resorcinarene

Abstract

A cleaner and eco-friendly method was developed for the preparation of tetra-kis(aminomethyl)calix-[4]-resorcinarene via a synthetic pathway of five steps starting from methylresorcinol. This alternative methodology is firstly based on avoiding the use of CH 2 BrCl, which is a non-eco-friendly substance with high ozone depletion potential, and on replacing it by CH 2 Cl 2 as a readily available reagent with much less dangerous effects. Secondly, this method engages ace-tone or CH 2 Cl 2 as the solvent of the bromination step in the place of the very toxic CCl 4 , leading to tetrakis(bromomethyl)calix-[4]-resorcinarene. The brominated intermediate has been reacted with sodium azide in acetone instead of the high-boiling solvent DMSO to produce tetrakis(azidomethyl) ca-lix-[4]-resorcinarene without the need of tedious purification. Lastly, this work reports an efficient hydrogenation method of the versatile azido adduct employing Pt/C (5%) as the catalyst for the preparation of the amino cavitand as an alternative route with high atom economy that can replace the classical methods used currently.