The novel title macrocycles, based on methylene-bridged 1,5-naphthalene units, have been obtained by template effect in a thermodynamically controlled synthesis. In details, the prism[5]arene 1 or the prism[6]arene 3 was selectively taken away from the equilibrium mixture by using the complemen-tary ammonium-templating agent. When only the solvent 1,2-DCE was used, then the 1,4-confused derivative 2 was ob-tained. The prism[5]arene here described shows a deep π-electron rich aromatic cavity thanks to which exhibits a great affinity for the quaternary ammonium guests, originat-ing from favorable cation··· π and +NC−H··· π interactions. This recognition motif is the basis of the templated synthesis of the prism[n]arenes here reported.

Ethyl- and propyl-prism[6]arenes are obtained in high yields and in short reaction times, independent of the nature and size of the solvent, in the cyclization of 2,6-dialkoxynaphthalene with paraformaldehyde. PrS[6]^Et or PrS[6]^nPr adopt, both in solution and in the solid state, a folded cuboid-shaped conformation, in which four inward oriented alkyl chains fill the cavity of the macrocycle. On these bases, we proposed that the cyclization of PrS[6]^Et or PrS[6]^nPr occurs through an intramolecular thermodynamic self-templating effect. In other words, the self-filling of the internal cavity of PrS[6]^Et or PrS[6]^nPr stabilizes their cuboid structure, driving the equilibrium toward their formation. Molecular recognition studies, both in solution and in the solid state, show that the introduction of guests into the macrocycle cavity forces the cuboid scaffold to open, through an induced-fit mechanism. An analogous conformational change from a closed to an open state occurs during the endo-cavity complexation process of the pentamer, PrS[5]. These results represent a rare example of a thermodynamically controlled cyclization process driven through an intramolecular self-template effect, which could be exploited in the synthesis of novel macrocycles.

The synthesis of water-soluble prism[n]arenes (n = 5 and 6) bearing anionic carboxylato groups on the rims is described. The binding properties of this novel class of water-soluble hosts are studied by nuclear magnetic resonance and calorimetry. The complexation of singly and doubly charged ammonium guests with the more rigid pentamer is enthalpically driven by secondary interactions, while the thermodynamic fingerprint for the larger hexamer reveals driving forces that strongly depend on the guest charge and/or size.

Methoxy-prism[5]arene PrS[5]^Me is demethylated by a supramolecularly assisted reaction. In the presence of a tetramethylammonium cation, PrS[5]^Me is demethylated by BBr₃ in high yield, while in its absence a 55/40 mixture of PrS[5]^OH/PrS[6]^OH is formed. The dealkylation of prismarenes, such as PrS[6]^R (R = Et, nPr) and c-PrS[5]^Me, can be easily obtained in high yields in the presence of BBr₃.

Calix[2]naphth[2]arenes make up a new class of phenol–naphthalene hybrid macrocycles. X-ray studies show that calix[2]naphth[2]arene 1 adopts a 1,2-alternate conformation. Alkali metal cations are complexed by the calixnaphtharenes in a 1,2-alternate conformation, by cation···π interactions with the naphthalene walls, and by RO···M⁺ ion–dipole interactions. In the presence of Cs⁺, chiral complexes of calixnaphtharenes 5 and 6 were observed in which the cation is nested on one of the two faces of the macrocycle.

The direct macrocyclization to prism[5]arenes of 2,6-dialkoxynaphthalenes with branched and bulky alkyl groups has been obtained in good yields. The chirality of these novel prism[5]arenes is stable on the NMR time scale.