Unprecedented synthesis of chiral calix[4](aza)crowns and its potent encapsulating methanol

Abstract

Unprecedented synthesis of chiral (aza)crown ethers of calix[4]arene derivatives bearing a carboxyl amide bridge was described. The synthesis proceeds through condensation of the corresponding dinitriles with optically active 1,2-aminoalcohols, and is catalyzed by the ZnCl 2 Lewis acid at elevated temperature in a very efficient one-pot process. The cavity of calix[4](aza)crowns can encapsulate methanol molecules by O-H· · ·π interaction, which has been confirmed by X-ray crystal structures and ESI-MS.chiral calix[4](aza)crown, dinitrile, 1,2-aminoalcohol, X-ray crystal structure, inclusion complex

Chiral Moieties-Oriented Single-Stranded Helical Assembly of Calix[4]azacrown Derivatives

“…Interestingly, very limited methodologies for constructing calix[4]azacrown derivatives have been reported. In a previous publication, we demonstrated the facile synthesis of S - 1 , R - 1 , and S - 2 (Scheme ) in high yield, starting from 5,11,17,23-tetra- p - tert -butyl-25,27-di(cyanomethoxy)-26,28-dihydroxycalix[4]arene and substituted l / d -amino alcohols, while their solid state supramolecular helical structures were overlooked. In this paper, we demonstrate that the optically active calix[4]azacrown derivatives S - 1 , R - 1, and S - 2 form helical arrangements in the solid state with opposite supramolecular chirality (M for S - 1 and P for R - 1 ).…”

“…S - 1 , R - 1 , and S - 2 were prepared according to published literature procedures . Detailed synthetic procedures are also given in the Supporting Information.…”

“…The crystal data and structure refinement details for S - 1 and R - 1 are summarized in Table . The X-ray crystal structure of S - 2 has been reported previously by us but was not discussed with regard to intermolecular interactions. Unfortunately, we were unable to grow crystals of R - 2 that could be suitable for X-ray analysis, despite repeated efforts and using various methods.…”

“…S-1, R-1, and S-2 were prepared according to published literature procedures. 15 Detailed synthetic procedures are also given in the Supporting Information. The crystal data and structure refinement details for S-1 and R-1 are summarized in Table 1.…”

“…The single-crystal X-ray analysis reveals that S-2 crystallizes in chiral space group P2 1 , the unit cell containing two independent calix[4]arene derivative moieties and two encapsulated methanol solvent molecules. Although the crystal structure of S-2 has been reported in our 15 its supramolecular chain structure had not been noticed at this time. In the crystal of S-2, we can clearly see that each helix has a pitch of 34.928(5) Å (Figure 5a).…”