M. Roy, V. Berezhnaia, M. Villa, N. Vanthuyne, M. Giorgi, J. - V. Naubron, S. Poyer, V. Monnier, L. Charles, Y. Carissan, D. Hagebaum‐Reignier, J. Rodriguez, M. Gingras, et Y. Coquerel, « Stereoselective Syntheses, Structures, and Properties of Extremely Distorted Chiral Nanographenes Embedding Hextuple Helicenes », Angewandte Chemie International Edition, vol. 59, nᵒ 8, p. 3264-3271, 2020.
Résumé : We report a molecular design and concept using π-system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π-distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi-helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto-type cyclotrimerizations of racemic or enantiopure 9,10-dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°).
Mots-clés : aromaticity, helicenes, POLE 1, polycyclic aromatic hydrocarbons, ROCS, stereoselectivity, strained molecules.