p-tert-butylcalix[4]arenes containing azacrown ether substituents at the lower rim as potential polytopic receptors

Extraction and Complexing Abilities of a Series of p-Tert-butylcalix[4]arenes Substituted by N-carbonylmonoaza-12-crown-4

“…To introduce substituents containing an amide fragment into the calixarene molecule, a previously developed approach based on the acylation of amino components using carboxy-substituted calixarenes (1-4) under the conditions of the activated ester method in the presence of DCC and hydroxybenzotriazole (HOBt) was implemented [3,7]. Thus, the series was synthesized: mono-(5), di-( 6), tri- (7) and tetra- (8) [(1,4,7-trioxa-10-azacyclododec-10-yl)carbonylmethoxy]-p-tert-butylcalix [4]arenes (Scheme 1). The 1 H NMR spectra indicate that the molecules of all calixarenes adopt a cone conformation.…”

“…All of metal chlorides were of analytical grade. 5,11,17,23-tetra-tert-butyl-25,26,27-tris[(1,4,7-trioxa-10-aza-cyclododec-10-yl)carbonylmethoxy]-28-hydroxycalix [4]arene (7). White solid; yield 85%.…”

Synthesis and Extraction Properties of p-tert-Butylcalix[4]arenes with Crown-5 Ether Substituents

“…As appears from our previously investigation of the complexing ability of series of calixarenes with two azacrown ether fragments this compound formed trinuclear complex with Na + (logβ 1 =5.6, logβ 2 =7.8, logβ 3 =7.88) and binuclear complex with K + (logβ 1 = 6.21, logβ 2 =9.55). [11] Calixarene 3 displays greater avidity toward Na + picrate vis-à-vis the K + picrate and K + / Na + extraction selectivity factor S, expressed as the ratio of the percentages extraction of potassium over sodium, is 14.16. Moreover, only this disubstituted ligand functions effectively as an Rb + extractant (%E value for Rb + -30 %).…”

“…It was reported previously that application of a modified carbodiimide method in the presence of 1-hydroxybenzotriazole (HOBT) is rather efficient approach that allows to obtain p-tert-butylcalix [4]arenes (substituted in different degrees) containing the amide groups at the lower rim, with high yields. [10,11] This method was applied by us for calixarenes containing crown ethers units. Synthesis of calixarenes containing N-methoxycarbonylaza (or benzoaza)-and 4-N-methoxycarbonylbenzo-15-crown-5 ether fragments 2-4, 6 was based on the initial 1,3-di-1 or tetra-5 carboxymethoxy-p-tert-butylcalix [4]arene derivatives in cone conformation [11] (Scheme 1).…”

“…[10,11] This method was applied by us for calixarenes containing crown ethers units. Synthesis of calixarenes containing N-methoxycarbonylaza (or benzoaza)-and 4-N-methoxycarbonylbenzo-15-crown-5 ether fragments 2-4, 6 was based on the initial 1,3-di-1 or tetra-5 carboxymethoxy-p-tert-butylcalix [4]arene derivatives in cone conformation [11] (Scheme 1). The way which was used for obtaining the calixarene with 4-ethoxyamidobenzocrown-5 ether 8 consists of reduction of bis(methoxycarbamoyl)-p-tert-butylcalix [4]arene 7 by the B 2 H 6 in THF [12] with following acylation of amino groups by 4-carboxybenzo-15-crown-5 ether in the presence of DCC (Scheme 2).…”