Molecular dynamics study of a heteroditopic-calix[4]diquinone-assisted transfer of KCl and dopamine through a water-chloroform liquid-liquid interface.

The ability of two heteroditopic calix[4]diquinone receptors to transport a KCl ion-pair and a dopamine zwitterion through a water-chloroform interface was investigated via molecular dynamics (MD) simulations. Gas-phase conformational analysis has been carried on KCl and dopamine receptor binding associations and the lowest energy structures found in both cases show that the recognition of KCl and dopamine zwitterion occurs through multiple and cooperative N-H..

Cooperative AND ion-pair recognition by heteroditopic calix[4]diquinone receptors.

A new family of heteroditopic calix[4]diquinone receptors capable of the cooperative recognition of ion-pair species through a contact binding mechanism has been developed. The receptors bind contact ion pairs cooperatively, with an unprecedented AND recognition phenomenon being observed to operate in certain cases, in which receptors display no affinity for either of the individual "free" cation or anion, but bind the cation and anion ion-pair strongly. X-ray crystallographic, solution-state, and computational methods rationalize the observed recognition behavior of the receptors.

Interweaving anion templation.

A new general interweaving anion templation strategy for the formation of interpenetrated and interlocked architectures is presented. Furthermore, the functional properties of the resulting systems, which have novel anion binding and sensory properties, are discussed.

Anion-templated calix[4]arene-based pseudorotaxanes and catenanes.

We present the rational design and anion-binding properties of the first anion-templated pseudorotaxanes and catenanes in which the "wheel" component is provided by a calix[4]arene macrobicyclic unit. The designs and syntheses of two new calix[4]arene macrobicycles, 2 and 3, are presented, and the abilities of these new species both to bind anions and to undergo anion-dependent pseudorotaxane formation are demonstrated. Furthermore, it is shown that performing ring-closing metathesis reactions on some of these pseudorotaxane assemblies gives novel catenane species 14 and 15, in which the yield of interlocked molecule obtained is critically dependent on the presence of a suitable anion template, namely, chloride.

Anion-templated assembly of [2]rotaxanes.

Anion templation is used to develop a general method for rotaxane synthesis. The anion-templated synthesis of three new [2]rotaxanes containing positively charged pyridinium axles and neutral isophthalamide macrocyclic components is described. The incorporation of electron withdrawing substituents, such as the nitro group, into the 5-position of an isophthalamide bis-vinyl acyclic precursor results in a significant improvement in [2]rotaxane assembly yields.

Cooperative AND receptor for ion-pairs.

A novel heteroditopic calix[4]diquinone receptor capable of binding an anion and cation simultaneously in a cooperative fashion is shown only to recognise halide anions in the presence of a suitable cobound cationic guest species, and displays affinity for certain ion-pairs where no affinity for either of the free ions is observed.

Demonstrating the synergy of synthetic, mechanistic, and computational studies in a regioselective aniline synthesis.

Tri- and tetrasubstituted anilines are formed in good to excellent yields by the addition of ketones to vinamidinium salts (up to 98%). The reaction proceeds via the formation of dienone intermediates, which react to form an enamine with the liberated amine. In the case of a nitro, or dimethylaminomethylene substituent, the enamines undergo a facile electrocyclic ring closure to form a cyclohexadiene, which goes on to form anilines with a high degree of selectivity (up to 50:1) with a minor competing pathway proceeding via the enol providing phenols.