Dagmar Kraft

Calixarenes with diphenylphosphoryl acetamide functions at the upper rim. A new class of highly efficient extractants for lanthanides and actinides

Various calix[4]arene tetraalkyl ethers and a calix[5]arene pentaalkyl ether substituted at the upper rim by the CMPO-like functional group –NH–C(O)–CH2–P(O)Ph2 as well as some linear model compounds have been synthesized for the first time. Their ability to extract europium, thorium, neptunium, plutonium and americium from 1 mol dm–3 aqueous HNO3 into methylene chloride or o-nitrophenyl hexyl ether was studied under various conditions. All the new oligomeric ligands, but especially the calixarene derivatives, are tremendously strong extractants compared with the commonly used CMPO [(N,N-diisobutylcarbamoylmethyl)octylphenylphosphine oxide]. Also in transport studies through supported liquid membranes their efficiency is higher than that of CMPO which shows lower transport rates even at a 10-fold concentration.

Regioselective synthesis of calixcrowns derived from p-tert-butylcalix[5]arene

Abstract Alkylation of p-tert-butylcalix[5]arene with oligoethylene glycol-ditosylates in the presence of CsF affords the 1,3-bridged calix[5]crowns 1a–c in 51 to 72% yield. In the case of hexaethylene glycol the isomeric 1,2-bridged calix[5]crown-7 2c was obtained additionally. The calixcrowns were further modified by alkylation of the remaining hydroxyl groups.

Double and triple calix[4]arenis connected via the oxygen functions

New macrocyclic molecules are described containing two or three p-tert-butylcalix[4]arene subunits connected via their oxygen atoms. These macrocycles are available by two general methods which are capable of producing assemblies with bridges of varying rigidity and length.

Inherently chiral calixarenes

Due to the nonplanarity of the basic 1 n -metacyclophane system, calixarenes and resorcarenes can be transformed into molecules with inherent chirality. Various attempts to achieve this goal are reviewed. Special emphasis is given to derivatives with C n -symmetry, including derivatives of spherand calixarenes and other calixarene-like macrocycles.

Cyclic esters of calixarenes with phthalic acid and pyromellitic acid; synthesis and X-ray molecular structures

The reaction of phthaloyl dichloride with tert-butylcalix[4]-, calix[5]- and calix[6]-arene has been studied. While the 1,2-bridged macrocyclic ester is the main product in the case of calix[4]- and calix[6]-arene, the intramolecular bridging of the calix[5]arene occurs mainly in the 1,3-position. The derivatives of calix[4]- and calix[6]-arene could be further O-alkylated and the ester bonds may be easily hydrolysed in these derivatives. 1,2-Singly bridged derivatives of calix[4]- and calix[6]-arene were also obtained with ClCH2Br. Reaction of tert-butylcalix[4]arene with pyromellitic acid tetrachloride leads to the formation of a new double calixarene.The structures of two cyclic esters have been determined by X-ray crystallography. Crystals of compound 6c·0.2 McOH are triclinic, space group P, with two molecules in a unit cell of dimensions a= 10.9292(6), b= 15.0534(10), c= 16.8534(14)A, α= 94.195(6)°, β= 90.044(6)°, γ= 100.171(5)°, R= 0.075 for 2187 observed reflections. Crystals of compound 8·0.83 C7H8·0.38 C6H14 are monoclinic, space group P21/n, with 4 molecules in a unit cell of dimensions a= 14.5554(13), b= 35.3802(24), c= 15.0160(12)A, β= 99.782(7)°, R= 0.072 for 4028 observed reflections. The phthaloyl residue is enclathrated in the molecular cavity of a neighbouring calix[6]arene in a self-inclusion process resulting from C–H⋯π(arene) hydrogen-bonding interactions.

The number of possible structures of conformationally fixed O-alkylation products of calix[4]arenes

Abstract O-Alkylation of calix[4]arenes leads to conformationally fixed derivatives provided the groups attached to the oxygen are large enough. In principle 34 different tetra-, 13 tri-, 8 dialkylation products may be obtained starting with a calix[4]arene consisting of four identical phenolic units. 17,9 and 3 of these derivatives are inherently chiral.