Chirality transfer in a cage controls the clockwise/anticlockwise propeller arrangement of the tris(2-pyridylmethyl)amine ligand

Abstract

A predictable control of the propeller arrangement of the tris(2-pyridylmethyl)amine (TPA) ligand was achieved in the smallest hemicryptophane 1. Coordination of Cu(i) result in a rare T-shaped complex with controlled helicity of the TPA-Cu core.

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

“…This solid-state structure reveals a CTV-dictated triple-stranded helical arrangement of the phenyl linkers of 5 , but no orientation of the southern TPA part was observed ( Figure 1E ). On this basis, Colomban, Martinez and co-workers have designed the structurally contracted cage 6 (Qiu et al, 2019 ) where the phenyl linkers are replaced by single methylene –CH 2 - ( Figure 2A ). The authors resonated that a closer proximity between the chiral northern CTV cap and the southern TPA ligand would result on the propagation of the chirality to the ligand, allowing for a predictable control of its helicity.…”

Rationalization of chirality transfer and fast conformational changes in a tris(2-pyridylmethyl)amine-based cage

“…9 In this line, we have recently reported the covalent capping of the TPA ligand by a chiral cyclotriveratrylene unit as an efficient strategy to obtain predictable control of the clockwise/ anticlockwise propeller arrangement of the TPA ligand. 10 Indeed, the hemicryptophane cage 1, which consists in a TPA ligand covalently attached to a CTV unit through three methylene -CH 2bridges, displays a propeller arrangement of the southern pyridines dictated by the chirality of its northern CTV (Fig. 1a): the X-ray structure reveals that the P-CTV imposes a right-handed propeller orientation of the TPA moiety (the P/P-1 cage), whereas the M-CTV enantiomer induces a le-handed orientation of the TPA moiety (the M/M-1 cage).…”

“…1a): the X-ray structure reveals that the P-CTV imposes a right-handed propeller orientation of the TPA moiety (the P/P-1 cage), whereas the M-CTV enantiomer induces a le-handed orientation of the TPA moiety (the M/M-1 cage). 10,11 The crystal structure of 1 is particularly compact: by observing the TPA part, Fig. 1a, we notice that one -CH 2unit connected to the nitrogen atom N sp 3 has its hydrogen atoms pointing inside the cage (one-arm-inside conformation).…”

“…Indeed, NOE correlations between the -CH 2 -N protons and the aromatic protons of the CTV unit were observed, suggesting that the self-inclusion process is certainly retained and that each arm goes in and out of the cavity at a rate that is fast on NMR time scale. 10 As the static view of the X-ray diffraction analysis and the time-scale resolution of the NMR, result in a relatively simple view of the three-dimensional arrangement, we present here a detailed study of the chiral cage 1 based on experimental observations and computational techniques. Indeed, computational treatments represent a powerful tool that allows for exploring the conformational space that could hardly be evidenced experimentally.…”

A tris(benzyltriazolemethyl)amine-based cage as a CuAAC ligand tolerant to exogeneous bulky nucleophiles

“…These NMR observations, which reveal that the C3 symmetry of Hm-TBTA is retained upon metal coordination at its tris(triazolemethyl)amine unit, strongly suggest that the coordination of the Cu I metal ion occurs with an endohedral functionalization of the copper complex. 17 The performance of our capped ligand Hm-TBTA was then evaluated and compared with the one of its related open analogue, in a model CuAAC transformation. We have studied the cycloaddition reaction between benzyl azide and phenylacetylene 3, catalyzed by 1.0 mol% of the Cu I (CH3CN)4(PF6) metal salt, in the absence of reducing agent, in a 10:1 CH2Cl2/MeOH solvent mixture, at room temperature, under an oxygen-protected atmosphere (see ESI).…”