Synthesis and properties of double-calix[4]arenes, doubly-crowned calix[4]arenes, and double-calix- crowns

Content Provider	Semantic Scholar
Copyright Year	2004
Abstract	Syntheses of double-calix[4]arenes, doublycrowned calix[4larenes, and double-calix-crowns have been achieved by reacting p-tert-butylcalix[4larene or a new mesitol based calixL41arene with various polyethylene glycol ditosylates in the presence of potassium carbonate in refluxing acetonitrile. Depending on the nature of the ditosylate and on the reaction times are differently obtained calixarene ligands. The complexation properties toward alkali cations are presented for the double-calix-crown derived of p-tert-butylcalix[4larene. INTRODUCTION Calixarenes (refs 1 & 2) are a new class of macrocyclic compounds that have attracted supramolecular chemists because of their chemical versatility and conformational properties for designing flexible and preorganized molecular receptors such as calixcrowns and calixspherands (ref. 3). The present work enlarges the family of calixcrown based receptors. SYNTHESIS AND PROPERTIES The treatment of p-tert-butylcalix[4larene and lI3-dimethoxy-p-tertbutylcalix[4larene with triethylene glycol ditosylate in the presence of potassium carbonate in refluxing acetonitrile for 7 days afforded the corresponding double-calix[4larenes Ia ( R = H) and Ib ( R = CH3) which were shown to consist of two calixr4larene moieties linked by two opposite glycolic chains (ref. 4). It is known that p-tert-butylcalix[4larene reacts with ditosylates to give capped p-tert-butylcalix[4larenes in which the glycolic chain is intramolecularly connecting the 1and 3positions (ref. 5). The preference in the formation of doubleor capped calix[4]arenes may be explained by the difference in the experimental conditions. Capping of p-tert-butylcalix[4larene was achieved by reaction with the ditosylate ( 1 equiv.) in refluxing benzene using 2 equiv. of potassium tert-butoxide added stepwise in two 7 equiv. portions (ref. 5). Double-calix[4larenes Ia,b have been prepared by using an excess of potassium carbonate ( 1 0 equiv.) in one crop in acetonitrile. It is assumed that in these conditions the Il3-diphenolate is more easily formed due to the excess of base in a more polar solvent. The 1,3-diphenolate might react simultaneously with two tosylates (2 equiv.) to afford lI3-dialkylated p-tert585 586 2. ASFARI et a/. L i6W 'm I U butylcalix[4larene bearing two glycolic chains ended by tosylate leaving groups which can therefore react with a new dianion. 'H-NMR showed the two p-tert-butylcalix[4larene units of Ia to exist in the cone conformation as illustrated in Figure 1 .
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://old.iupac.org/publications/pac/1993/pdf/6503x0585.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article