Unravelling Structural Dynamics, Supramolecular Behavior, and Chiroptical Properties of Enantiomerically Pure Macrocyclic Tertiary Ureas and Thioureas

Synthesis of Imidazolidin-2-ones from trans-(R,R)-Diaminocyclohexane: A Statistical Analysis-Based Pseudo-Multicomponent Protocol

A pseudo-multicomponent one-pot protocol for the synthesis of 1,3-disubstituted imidazolidin-2-one is described, employing trans-(R,R)-diaminocyclohexane for the in situ formation of the Schiff base, followed by reduction to produce the respective diamine and cyclization with carbonyldiimidazole (CDI). This approach utilizes statistical analysis to optimize the reaction conditions, allowing a pseudo-multicomponent protocol to be proposed. The developed method demonstrates sustainability, efficiency, and potential applications in green chemistry, achieving yields ranging from 55% to 81%. This represents a significant advance in synthesizing heterocyclic compounds with biological and pharmacological applications.

Thio-modified trianglimines, a novel group of chiral macrocyclic compounds of high structural dynamics

The embellishing of the macrocycle core with sulfur substituents of varied sterical requirements changes the structural dynamics of chiral, triangular polyimines. Despite their formal high symmetry, these compounds adopt diverse conformations, in which the macrocycle core represents a non-changeable unit. DFT calculations reveal that the mutual arrangement of sulfur-containing substituents is controlled mainly by sterical interactions. The presence of sulfur atoms affects the chiroptical properties of these compounds and causes a red shift of respective absorption bands compared to the basic trianglimine. Unexpectedly, the aromatic fragments attached to the sulfur atom have less impact on ECD spectra, visible only in particular spectral regions. Such a possibility to adapt various conformations is also seen in the crystalline phase; however, a stiff basic unit - the triangular macrocycle core - caused macrocycles' self-assembly into columnar-like aggregates. In the crystal lattice, around the macrocycle having bulky SCPh3 groups, a space filled with solvent is formed; however, the macrocycle's internal cavity is closed and unavailable for guest molecules. Titration of the solutions of basic SBn-substituted imine and amine macrocycles by AgOTf results in significant changes in the ECD spectra, confirming possible binding interactions between macrocycle and metal cations.

Cycloglycolurils: Hybrid Glycoluril-Cyclobenzil Macrocycles

Two novel glycoluril macrocycles have been synthesized from cyclotetrabenzil and cyclotribenzoin precursors using solvent-free condensations with urea. The crystal structure of the cyclotetra(p-phenylene)glycoluril macrocycle shows a twisted ring conformation, while that of the cyclotri(m-phenylene)glycoluril hybrid exhibits a distinct tubular supramolecular packing. These structures establish a potentially broad new class of macrocycles with intriguing guest binding properties owing to their available N-H motifs.