Synthesis and Conformational Studies of Novel Calixarene‐Analogous Macrocyclic [3.1.1]Metacyclophanes

Abstract

Hydroxy[3.1.1]rnetacyclophane 4c, which is regarded as an unsymmetric or uncomplete "homocalixarene " bearing a propane bridge, has been synthesized using Nafion-H catalyzed cyclobenzylation. A novel "pendulum" type motion steered by intramolecular hydrogen bonding has been observed. Demethylation of compound 4c with BBr3 in methylene dichloride was carried out at room temperature for 3 h to afford the dihydroxy[3.l.l]metacyclophane 4b in 74% yield along with the trio1 4a in 25% yield. Trio1 4a was tri-0-alkylated with methyl iodide in the presence of NaH to yield partial-cone conformer 4d in quantitative yield. Similarly, a significant amount of partial-cone conformer 5 results in the case of 0-alkylation of 4a with N,N-diethylchloroacetamide. 'H-NMR titration of partial-cone amide 5 with NaSCN clearly demonstrates that a 1:1 complex is formed which is stable on the NMR time scale.

Synthesis and conformational studies of calixarene analogue chiral [3.3.1]metacyclophanes

“…In contrast to the conventional calix [4]arenes, the conformational isomerism in the present system is relatively simple. Owing to the intrinsic structural features, we envisaged that calix [3]arenes would provide a unique platform for the construction of inherently chiral macrocycles and prompted us to attempt the synthesis of inherently chiral propane bridged homocalixarenes [33]. The main objective of this research is to synthesize asymmetric or incomplete calixarene analogues of the inherently inherently chiral [3.3.1]metacyclophane bearing two propane bridges.…”

Sterically Crowded, Rigid,C3Symmetric Phosphites: Synthesis, Structure, and Preparation of Metal Complexes

“…Unfortunately, calix[ n ]arene-like macrocycles with only three oxygen donors are often quite difficult to prepare. Ligands such as hexahomooxacalix[3]arenes and trihydroxy[3.3.3]metacyclophanes, require longer linkers between the aryloxide ligands and involve several synthetic steps . With the larger cyclic structures, the macrocycles are extremely flexible, complicating the preparation of complexes.…”

Synthesis and Structure of 1,2‐Dimethylene[2.10]metacyclophane and Its Conversion into Chiral [10]Benzenometacyclophanes

“…Given the intrinsic structural features, we envisaged that MCP 9 would lead to inherent chirality in macrocycles due to intramolecular overcrowding as observed for helicenes or MCPs . The synthesis and optical resolution of inherently chiral MCPs is challenging, but because of their potential uses in supramolecular chemistry, they remain attractive .…”