New calix[4]arenes having electron donating groups at the upper rim as molecular platforms and host molecules (original) (raw)
Related papers
Tetrahedron, 2003
The synthesis and isolation of elusive tetralkoxycalix [4]arenes 2 in the cone conformation and bearing two formyl groups in proximal (1,2) positions at the upper rim are described for the first time. They were obtained as a mixture with the distal (1,3) regioisomers 3 by optimizing the Gross formylation reaction on the tetralkoxycalix[4]arenes 1. After reduction to the corresponding alcohols, compounds 4 could be isolated and oxidized to 1,2-diformyl (2) and 1,2-diacid (6) tetralkoxycalix[4]arenes. These 1,2-difunctionalized derivatives are useful intermediates for the synthesis of calixarene-based molecular receptors having proximal binding groups. q
Synthesis of Lower Rim Polyhydroxylated Calix[4]arenes
Synthesis, 2001
Several synthetic procedures were evaluated and a protective/deprotective method, which allows the introduction of two, three, and four amide-linked polyhydroxylated units (TRIS) at the lower rim of calix[4]arenes was developed. Di-and trifunctionalized derivatives are poorly soluble in water, whereas the solubility of calix[4]arene having four polyhydroxylated amide groups is good (6 ¥ 10-3 M at 25°C).
An easy access to tetra-o-alkylated calix[4]arenes of cone conformation
Tetrahedron, 1995
Fully 0-alkylated calix[4larenes have been synthesbed by the alkylation of p-tertbutylcalix(4)arene and Its IJdialkylated derivatives in liquid-liquid phase-transfer catalytic process. 1Hd and lH2R2 could effeciently be deprotonated by aqueous NaOH (50% w/w)-toluene system and alkylated with alkyl (aralkyl, allyl) halogens in good yields affording cahx[4]arene tetraethers of cone conformation.
Functionalization of calix[4]arenes by alkylation with 2-(chloromethyl)pyridine hydrochloride
The Journal of Organic Chemistry, 1992
The syntheses, structures, and conformations of nine of the 13 possible [ (2-pyridylmethyl)oxy]calix[4]arene conformers obtainable by direct substitution on calix[4]arenes la,b are described. The conformer distribution in the exhaustive 0-alkylation of la,b with 2-(chloromethyl)pyridine hydrochloride (PicC1-HC1) in N,N-dimethylformamide (DMF) is strongly affected by the base applied: NaH induces only cone conformers, while KzC03 or CszC03 lead preferentially to partial cone and/or 1,a-alternate conformers, depending on the para substituent of the starting calix[(]arene. Single-crystal X-ray analyses on tetra-0-alkylated cone lk,l and partial cone 2c have been conducted. Molecule lk has a distorted cone conformation with pendant OCH,Py groups; a methanol of solvation is hydrogen bonded to one pyridine N atom and is exo to the calix cavity. The crystal structure of 11 contains two independent distorted cone shaped molecules per asymmetric unit which differ principally in the relative orientations of the OCH,Py groups. In the partial cone conformer 20 the conformation adopted is such that the pendant OCHzPy group of the rotated aryl ring lies in, and effectively fills, the calix cavity produced by the remaining three aryl rings; as in lk a methanol of solvation is hydrogen bonded to a pyridine N atom exo to the calix cavity. Regioselective syn-proximal (l,Z-) or syn-distal(l,3-) difunctionalization at the lower rim of calix[4]arenes has been also achieved. Syn-1,2-disubstituted derivatives have proved to be useful intermediates for the stereoselective synthesis of tTi-O-alkylated cone conformers, &[4]arenea with mixed ligating groups in the sequence AABB at the lower rim, for inherently chiral calix[4]arenes, and for the transfer of proximal regioselectivity from the lower to the upper rim. On the basis of stepwise 0-alkylation of calix[4]arenes, and with the aid of MM2 calculations on the involved intermediates and their anions, a possible genesis of the various conformers is proposed.
Synthesis of monoalkylated calix[4]arenes via direct alkylation
Tetrahedron, 1991
A new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented. Reaction of calix[4]arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the monoalkylated calix[4]arenes in moderate to good yields
Synthesis of New Calix[4]arenes Functionalizated by Acetylhydrazide Groups
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2007
A series of new calix[4]phenols, calix[4]resorcinols and calix[4]pyrogallols with acetylhydrazide substitutes has been synthesized with high yields by hydrazinolysis of ester group containing calix[4]arenes. The synthesized calix[4]phenols adopt the cone conformation while the calix[4]resorcinol and calix[4]pyrogallol derivatives prefer the boat conformation. The amide fragment of the hydrazide groups predominantly exists in the trans-conformation. The binding ability of synthesized calix[4]arenes toward transition and alkali metals by solvent extraction has been investigated.
Selective functionalization of calix[4]arenes at the upper rim
The Journal of Organic Chemistry, 1990
Methods are described for the Selective diametrical functionaCization of calix[4]arenes at the uppeT@ trarufer of functionality and selective substitutions at the para positions of the phenol rings. The crystal structure of 26,28-dimethoxy-11,23-dinitrocalix[4]arene is described. Calix[4]arenes1 are able to form host-guest complexes in the solid state2 as well as in solution3. Most work has been directed to the complexation of cations in the 'polyoxygen' cavity (lower rim)4. Recently, we have used 26,28-dimethoxy-l1,23-bis[(dimethyla~o)methyl]calix[4]a 12 could be isolated in 91% yield (mp >330
Synthesis of carbohydrate functionalised n-propoxy-Calix[4]arenes
Tetrahedron Letters, 1998
The Suzuki ~action has been used to couple para-bromophenyl glycosides to boronic acid derivatives ofn-propox3,-Calix[41arenc ; " a one-pot " methodology eliminates the need to isolate the boronic acids and increases the overall yield. The synthesis provides a new class of carbohydrate containing calixarencs with a deepened cavi .ly. In order to enlarge the cavity of calix[4]arene derivatives, Atwood et allhave prepared a pphenylcalix[4]arene tetramethylether. Such calix[4]arene derivative should be capable of binding organic guest molecules. However the methyl derivatives are present in the semi-cone conformation, which is neither optimised for guest binding nor for increasing carbohydrate recognition by cooperative interaction. 2 In view of this, the tetra-propyl derivatives blocked in the cone conformation are of great interest. Bearing in mind the significant role played by sugars in many biological events, the coupling of carbohydrate antennae to the calix[4]arenes may provide a new class of molecular vectors. To this end, Dondoni and Ungaro3'4et al have described the synthesis of calix[4]arenes substituted by carbohydrate units at
Synthesis of 1,2-bridged calix[4]arene-biscrowns in the 1,2-alternate conformation
Tetrahedron, 1997
New methods to obtain 1,2-bridged calix[4]arene-biscrowns in the 1,2-alternate conformation are described. The stereochemistry of the proximal double functionalization reaction is mainly governed by the solvent, the length of the polyether units and the base used to deprotonate the calix[4]arene. The possibility to synthesize cyclophanes having different orientations of the binding sites in general and of the aromatic nuclei in particular, is important for the preparation of efficient and selective hosts for ions and neutral molecules. In this perspective versatile building blocks for the synthesis of specific receptors are the four stereoisomers of calix[4]arenes (Cone, Partial Cone, 1,2-Alternate, 1,3-Alternate).l However, in spite of the extensive synthetic efforts carried out by us and others to obtain stereocontrolled functionalization of calix[4]arenes, only few and indirect methodologies have been reported so far for the synthesis of calix[4]arenes in the 1,2-alternate conformation. 2 Only very recently, Pappalardo et al. have reported the synthesis of 1,2-bridged calix[4]crown derivatives in the 1,2-alternate conformation starting from bis-1,2-picoline precursors) As part of a general project aimed at enhancing the selectivity and efficiency of calixarene hosts in molecular recognition processes, we tackled the synthesis of calix[4]arene-biscrown-5 (3) in the cone conformation.
The Journal of Organic Chemistry, 1994
A versatile route to a series of C-alkylcalix[4lresorcinarenes has been developed, using 2,4dimethoxycinnamates as starting materials under carefully controlled reaction conditions employing BF3 as a Lewis acid catalyst. Depending on the reaction conditions and the nature of the ester side chain in the cinnamates, the calixarenes can adopt 1,2-alternate, 1,3-alternate, or flattened-cone conformational states. An extensive study, relating to the influence of the Lewis acid, temperature, and reaction time, has provided information on the relative ratios of the different conformations and their interconversion. Structural assignments are based on detailed spectroscopic analyses including X-ray analyses. The latter provide evidence of their molecular structure and shape in the solid state. A detailed molecular modeling study has been completed and is described. From the data obtained, good agreement with NMR data, X-ray analyses and experimental results is observed.