Durch Kondensation von p-tert-Butylphenol mit Formaldehyd sind in einem Schritt in guten Ausbeuten cyclische Oligomere erhaltlich, in denen je nach Reaktionsbedingungen vier, sechs oder acht Phenolbausteine uber Methylenbrucken verknupft sind. Die kelchartige Gestalt der stabilsten Konformation des Tetramers erklart den Namen Calixaren (calix = Kelch). In ahnlicher Weise liefert Resorcin bei der Kondensation mit einer Vielzahl von Aldehyden cyclische Tetramere mit dem gleichen Grundgerust (Resorcarene). In beiden Fallen erfordert die Herstellung keine Verdunnungsbedingungen, so das auch grosere Mengen leicht zuganglich sind. Uberdies konnen die Stammverbindungen vielfaltig modifiziert werden, wobei die phenolischen Hydroxygruppen und die Phenylringe zwei Ansatzpunkte bieten, die getrennt oder in Kombination genutzt werden konnen. Calixarene sind deshalb ideale Edukte fur die Synthese der unterschiedlichsten Wirtverbindungen und Bausteine fur die Konstruktion groserer molekularer Systeme mit definierter Struktur und Funktion. Die potentiellen Anwendungen reichen vom Einsatz als hochspezifische Liganden fur die Analytik, die Sensortechnik und die medizinische Diagnostik uber die Verwendung zur Decontaminierung von Abwassern bis hin zur Konstruktion kunstlicher Enzyme und zur Herstellung neuer Materialien fur die nichtlineare Optik oder fur ultradunne Schichten und Siebmembranen mit molekularen Poren.

Calixarene – Makrocyclen mit (fast) unbegrenzten Möglichkeiten

Tetrahedron report number 205

Combretastatin-like chalcones as inhibitors of microtubule polymerization. Part 1: Synthesis and biological evaluation of antivascular activity

A novel class of resorcinarene-based cavitands 2a−e that fold into a deep (8 × 10 A dimensions) open-ended cavity by means of intramolecular hydrogen bonds has been synthesized. As follows from the FTIR and 1H NMR spectral data in apolar solvent, a seam of eight intramolecular hydrogen bonds is stitched along the upper rim of the structure 2a−e; the amide CO...H−N interactions bridge adjacent ringsinterannular bindingand are held in place by the seven-membered intraannular hydrogen bonds. The self-folding in 2a−e is reversibly controlled by solvent and temperature. Complexation of self-folding cavitands 2a−e with organic molecules such as (1-substituted) adamantanes, lactams, and cyclohexane derivatives was demonstrated by 1H NMR spectroscopy in CDCl3, benzene-d6 and p-xylene-d10; the binding energy -ΔG° values of 2−4 kcal mol-1 in p-xylene-d10 at 295 K were calculated. The exchange between complexed and free guest species is slow on the NMR time-scale, and it is proposed that hydrogen bonds are responsib...

Self-Folding Cavitands

In the last few years, polymers with highly conjugated chains have attracted much attention because of their wide variety of applications in the field of electronics, opto‐electronics, and photonics. Polyimines (PIs) (polymeric Schiff bases) is a class of polymer family, which has been less reviewed. In this paper, we focus on the synthesis methods of PIs by polycondensation, using diamines or hydrazine and dialdehydes, diketones or quinone compounds, or by chemical and electrochemical polymerization of imine oligomers containing terminal oxidable groups (pyrrole, thiophene, furan, naphthalene, etc). PIs with liquid crystalline behavior or having rotaxane and dendrimer architectures are also discussed. Structure, thermal, opto‐electronic, electrical, and mechanical properties and some potential applications of this class of polymers are presented in the last chapters.

Imine Oligomers and Polymers

Structurally new macrocycles from the resorcinol-aldehyde condensation. Configurational and conformational analyses by means of dynamic NMR, NOE, and T1 experiments

The conformational behaviour of the three macrocyclic octaols (4)–(6), obtained by acid-catalysed condensation of resorcinol with heptanal, is elucidated for the first time. Two of them, namely the diamond (5a) and the chair (6a) stereoisomers, undergo a ring-inversion conformational process in acetone to give the corresponding crown conformers (5b) and (6b). In DMSO or on addition of acetic acid to an acetone solution of diamond octaol (5), conformer (5a) is favoured. The presence of such equilibria and solvent effects are interpreted as an interplay between the tendency of the phenolic OH groups to form intramolecular hydrogen bonds and the alky chains to assume the endo position, avoiding steric repulsions and allowing self-aggregation.

Nuclear magnetic resonance elucidation of ring-inversion processes in macrocyclic octaols

Silver assisted rearrangement of primary and secondary α-bromo-alkylarylketones

Deuterium NMR spectroscopy of C6D6, added as a probe to compound 1, shows the formation of an uniaxial columnar mesophase, with domain directors perpendicular to the magnetic field. Spectral patterns at various temperatures are interpreted in terms of slow equilibrium between two solvent sites placed respectively between the cores and among the lateral chains. Deuterium NMR spectra of the deuteriated derivative 2 confirm this model, allow the evaluation of the molecular order parameter, Szz, and exclude the presence of fast rotational diffusion around the main molecular axis.

Deuterium NMR investigation of a new class of macrocyclic columnar liquid crystal

5,6-Dihydro-4H-1,3-thiazines with a wide variety of substituents have been obtained by a one-step condensation of a thioamide, an aldehyde, and an olefin. The reaction proceeds through polar 1,4-cycloaddition of the thioamidoalkyl ion (generated in situ from the aldehyde and the thioamide) to the olefin and is stereospecific and regiospecific. Conformational and configurational n.m.r. analysis has been carried out on the diastereoisomeric pairs of 5,6-dihydro-4H-1,3-thiazines so obtained.

A new stereospecific synthesis of 5,6-dihydro-4H1,3-thiazines by polar 1,4-cycloaddition of thioamidoalkyl ions to olefins. Configurational and conformational nuclear magnetic resonance analysis of the products

Luigi Abis

Papers

Structurally new macrocycles from the resorcinol-aldehyde condensation. Configurational and conformational analyses by means of dynamic NMR, NOE, and T1 experiments

Nuclear magnetic resonance elucidation of ring-inversion processes in macrocyclic octaols

Silver assisted rearrangement of primary and secondary α-bromo-alkylarylketones

Deuterium NMR investigation of a new class of macrocyclic columnar liquid crystal

A new stereospecific synthesis of 5,6-dihydro-4H1,3-thiazines by polar 1,4-cycloaddition of thioamidoalkyl ions to olefins. Configurational and conformational nuclear magnetic resonance analysis of the products