One-step synthesis of a singly bridged biscalix[6]arene and evaluation of its alkali metal recognition properties

Abstract

This article describes one-step synthesis of a singly bridged biscalix[6]arene (2) and evaluation of its recognition properties towards alkali metal ions for the first time. Synthesis of 2 was accomplished through coupling of two 4-tert-butylcalix[6]arene units with one molecule of diethyleneglycol ditosylate. Both base and linker were found to play a role in the outcome of coupling reaction for the simple and efficient synthesis of 2. Complexation ability of 2 was studied by liquid-liquid extraction using alkali metal (Na Carrier activity of 2 towards the facilitated transport of alkali metal ions across a bulk liquid membrane was also studied and the transport behaviour was mechanistically explained. The predominant role of an ion exchange action mechanism in the transport process was observed.

Direct Synthesis of Singly-Bridged Biscalixarenes and Crowned-Calixarenes

“…Piqued by the previous work 10 , KHCO 3 -diethyleneglycol ditosylate combination have been further explored in this report to afford singly-bridged biscalixarenes. Thus, the substrates calix [6]arene (1b), calix [4]arene (1c) and p-tert-butylcalix [4]arene (1d) were reacted with KHCO 3 and diethyleneglycol ditosylate as shown in Scheme 1.…”

“…During the previous work on synthesis of biscalix [6]arene 2 from 1a, it was observed that changing the linker to triethyleneglycol ditosylate led to formation of calix[6]crown 3 10 . This part of the study was conducted to further investigate the effect of linker over the outcome of this KHCO 3 mediated reaction of bifunctional linkers with 1a (Scheme 2).…”

“…For the synthesis of these macrobicyclic compounds, calixarenes are coupled with bifunctional reagents which results in inter-and/or intra-molecular bridging depending on the reaction conditions 1,2 . For example, 5,11,17,23-tetrakis[(propargyloxy)methyl]-25,26,27,28-tetra(benzyloxy)calix [4]arene in 1,3-alternate conformation afforded both kinds of products when oxidatively coupled, though intermolecularly coupled product is obtained in just 7% yield 3 In the literature, direct reaction of calix [4]/ [6]arenes with oligoethyleneglycol ditosylates afforded crowned-calixarenes and/or multi-bridged biscalixarenes [31][32][33] as the reaction products; and in only few of the reports, formation of singly-bridged biscalixarenes like 2 was mentioned 10,34 .…”

Investigation of O-Methylation of p-tert-Butylcalix[6]arene using Methyl p-Tosylate

“…Since past two decades, I have been involved in exploiting calixarene based hosts for various targets like cesium 13,14 and fullerenes [15][16][17] , and developing synthetic protocols for selective functionalization of calixarenes 18,19 .…”