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Stereoselective Syntheses, Structures, and Properties of Extremely Distorted Chiral Nanographenes Embedding Hextuple Helicenes

2019; Wiley; Volume: 132; Issue: 8 Linguagem: Inglês

10.1002/ange.201913200

1521-3757

Myriam Roy, Veronika Berezhnaia, Marco Villa, Nicolas Vanthuyne, Michel Giorgi, Jean‐Valère Naubron, Salomé Poyer, Valérie Monnier, Laurence Charles, Yannick Carissan, Denis Hagebaum‐Reignier, Jean Rodriguez, Marc Gingras, Yoann Coquerel,

Graph theory and applications

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 C90 H48 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°).