Synthesis, resolution, and chiroptical properties of hemicryptophane cage controlling the chirality of propeller arrangement of a C₃ triamide unit

Abstract

The five‐steps synthesis of a hemicryptophane cage combining a benzene‐1,3,5‐tricarboxamide unit and a cyclotriveratrylene (CTV) moiety is described. Chiral high‐performance liquid chromatography (HPLC) was used to resolve the racemic mixture. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental electronic circular dichroism (ECD) spectra with the calculated ones. X‐ray molecular structures reveal that the capped benzene‐1,3,5‐tricarboxamide unit adopts a structurally chiral conformation in solid state: the chirality of CTV moiety controls the Λ or Δ orientation of the three amides.

Controlling the Length of Cooperative Supramolecular Polymers with Chain Cappers

“…Based on these design rules, we selected asymmetrically N ‐methylated BTA units ( S ‐1Me‐BTA and S ‐2Me‐BTA ) because of their structural similarity with a‐BTA and the bulkiness of the methyl groups. Moreover, hemicryptophane‐BTA ( HC‐BTA ), previously developed for molecular recognition and catalysis, was selected for this study because of the preorganization of the amide units and the crowding of one of its faces with a bulky cyclotriveratrylene cage. The crystal structure of HC‐BTA was previously solved and presents a conformational organization of the three amides oriented in the same direction to one another with a tilt angle from 5° to 19° with respect to the benzene ring, comparable to the amide conformations in a‐BTA monomer (12° tilt) .…”

“…Whereas chiral S ‐BTA was obtained as a white solid, all S ‐nMe‐BTA s (with n =1, 2, and 3) were obtained as colorless isotropic liquids. HC‐BTA was synthesized from a cyclotriveratrylene derivative and benzenetricarbonyl trichloride in 5 % yield and was obtained as a white solid …”

“…We opted for chiral, non‐racemic methylated derivatives to permit the use of chiroptical spectroscopic techniques. In addition, one monotonic BTA derivative that comprises a bulky cyclotriveratrylene cage was also investigated ( HC‐BTA , Scheme ). We examine in detail the influence of the chain capper on the structure of the supramolecular polymers using a combination of static light scattering (SLS), infrared (IR), UV and circular dichroism (CD) spectroscopy and density functional theory (DFT) calculations.…”

Control and Transfer of Chirality Within Well-Defined Tripodal Supramolecular Cages

“…The design of the cage-ligand 6 therefore allowed the authors to report an unprecedented Cu(I) complex with a controlled helicity of the TPA-Cu(I) core, highlighting the promises of the approach for the preparation of novel optically pure metal-based catalysts and receptors. This strategy combining a chiral CTV cap and short spacers to control the chirality of another C 3 symmetrical unit, has been further exemplified by Martinez and his team through the preparation of the hemicryptophane 7 (Long et al, 2019). Due to its ability to engage strong hydrogen bonds, the benzene-1,3,5tricarboxamide (BTA) unit has been widely reported as useful building block for the preparation of supramolecular assemblies (Kulkarni and Palmans, 2017;Zimbron et al, 2017).…”

“…This strategy combining a chiral CTV cap and short spacers to control the chirality of another C 3 symmetrical unit, has been further exemplified by Martinez and his team through the preparation of the hemicryptophane 7 (Long et al, 2019 ). Due to its ability to engage strong hydrogen bonds, the benzene-1,3,5-tricarboxamide (BTA) unit has been widely reported as useful building block for the preparation of supramolecular assemblies (Kulkarni and Palmans, 2017 ; Zimbron et al, 2017 ).…”