Chiral Cryptates Derived from a Hexaazamacrocycle

Abstract

The reactions of hexaazamacrocycle 1 with 2,6-bis(bromomethyl)pyridine or 2,6-bis[(tosyloxy)methyl)]pyridine in the presence of appropriate carbonates result in the formation of derivatives of cryptand 6: enantiopure azacryptates of sodium and potassium. Crystal structures of these compounds indicate interaction of a metal ion with four pyridine nitrogen atoms and four tertiary amine atoms. The competition reactions monitored by NMR spectroscopy indicate preferential binding of Na over K as well as higher affinity of 6 for Na in comparison with the [2.2.1] cryptand.

Halide-Controlled Extending–Shrinking Motion of a Covalent Cage

“…Besides shedding light on the halide-induced conformational rearrangements of an interesting class of anion receptors, the obtained insights can be of great interest for the important applications in which covalent organic cages are involved (as, e.g., molecular hosts, nanoreaction vessels, and catalysts). ,− ,− ,− …”

“…Organic molecular cages, as the systems described in this work, are organic molecules possessing a three-dimensional (3D) cavity and a backbone, consisting of carbon–carbon and/or carbon–heteroatom bonds. − Compared with coordination cages, in which metal ions are pivotal structural elements, , organic cages are generally made more stable by the covalent bonds. , …”

“…In recent years, organic cages have been gaining attention for potential applications as nanoreaction vessels, , in catalysis, , sensing, stabilization of reactive compounds, and as materials for separation processes . When applied as molecular hosts, − guest selectivity is mainly driven by the complementarity of shape, size, and interaction sites between the cavity of the organic cage and the guest. Molecular cages with a rigid cavity, hardly adapting to different guests, generally lead to a higher degree of selectivity.…”

Synthesis of Cross-Chain Bridging Cryptands and Induction of Molecular Chirality

“…Chiral cryptands have been synthesized for the chiral discrimination of organic compounds, and easily available chiral synthons possessing chiral carbon centers have been used as parts of components for the synthesis of the chiral analogues of original cryptands. − The construction of chiral centers during synthetic processes is another approach to the synthesis of chiral analogues. , An alternative strategy for the synthesis of chiral cryptand analogues is the induction of molecular chirality. For example, Collet and Lehn et al synthesized a potentially chiral speleand consisting of an azacrown ether and a C 3 -symmetric cyclotriveratrylene unit .…”