From 2 + 2 to 8 + 8 Condensation Products of Diamine and Dialdehyde: Giant Container-Shaped Macrocycles for Multiple Anion Binding

Abstract

The combination of 2,6-diformylpyridine and trans-1,2-diaminocyclopentane fragments results in 2 + 2, 3 + 3, 4 + 4, 6 + 6, and 8 + 8 macrocyclic imine condensation products. These imines can be reduced to the corresponding 2 + 2, 3 + 3, 4 + 4, 6 + 6, and 8 + 8 macrocyclic amines. The X-ray crystal structures of their protonated derivatives show a rich variety of macrocycle conformations ranging from a stepped 2 + 2 macrocycle to a multiply folded 8 + 8 macrocycle of globular shape. These compounds bind anions via hydrogen bonds: two chloride anions are bound above and below the macrocyclic ring of the 2 + 2 amine, one chloride anion is bound approximately in the center of the 3 + 3 macrocycle, and two chloride anions are deeply buried inside a folded container-shaped 4 + 4 macrocycle, while in the case of the previously reported 6 + 6 amine four chloride anions and two solvent molecules are buried inside a container-shaped macrocycle. Yet another situation was observed for a multiply folded protonated 8 + 8 macrocycle which binds six sulfate anions; two of them are deeply buried inside the container structure while four anions interact with the clefts at the surface of the container.

Internal Hydrogen Bond Influences the Formation of [2+2] Schiff Base Macrocycle: Open‐Chain Vs. Hemiaminal and Macrocycle Forms

“…[19][20][21][22] The condensation of DFP with racemic DACH, run in boiling methanol (338K) and in the absence of any templating agent, leads to [2+2] imine 1(CH) accompanied with its 4+4 homologue. [19][20][21][22] The condensation of DFP with racemic DACH, run in boiling methanol (338K) and in the absence of any templating agent, leads to [2+2] imine 1(CH) accompanied with its 4+4 homologue.…”

“…[19][20][21][22] The condensation of DFP with racemic DACH, run in boiling methanol (338K) and in the absence of any templating agent, leads to [2+2] imine 1(CH) accompanied with its 4+4 homologue. racemic DACP, delivers exclusively the [2+2] Schiff base condensation product 1(CP) having also characteristic meso structure (Scheme 1) [21,22] Both small [2+2] imines serve as precursors in their unusual expansion reaction into enlarged 6+6, 8+8 and even bigger derivatives. The same reaction of DFP with a smaller homologue of DACH, i.e.…”

“…[23][24][25][26][27][28][29][30][31][32][33][34][35][36] It should be emphasized that the 1,2-cycloalkyldiamines (especially trans-1,2-diaminocyclohexane) were studied in detail in the formation of ([2+2]) imine macrocycles scrutinizing the role of chirality of conformational preorganization. [19][20][21][22] tion. What does not raise doubts are three stages of the reaction, i.e.…”

“…[44] Again, for the reaction between benzaldehyde and 4-amine-4H-1,2,4-triazole quantum chemical topology methods revealed that the detachment of the [OH] fragment precedes the H′ transfer in N-H′···O bridge ((f ) in Scheme 2), the final step leading to H 2 O formation. [19][20][21][22] The not-templated synthesis of the macrocycle product is possible, however the outcome of the reaction strongly depends on the experimental conditions. Interestingly, between the CO bond dissociation and the NH′/OH′ bonds alteration, the latter roughly coinciding with the maximum of the energy barrier, there is a relatively long part of the reaction path whose crossing requires some one third of the energy barrier.…”

“…As examples of such dynamic libraries one can mention reactions possible within 2,6-diformylpyridine (DFP)/trans-1,2-diaminocyclohexane (DACH) and 2,6-diformylpyridine (DFP)/ trans-1,2-diaminocyclopentane (DACP) systems. [19][20][21][22] The condensation of DFP with racemic DACH, run in boiling methanol (338K) and in the absence of any templating agent, leads to [2+2] imine 1(CH) accompanied with its 4+4 homologue. Both imine products of alternating RRSS and RRSSRRSS chiralities of diamine units [19,20] have meso type structures.…”