Hetero-helicenes synthesis through 1,3-dipolar-cycloaddition of sydnones with arynes: Synthesis, origins of selectivity and application to pH triggered chiroptical switch with CPL-sign reversal
Abstract : The regioselective access to hetero-helicenes through 1,3-dipolar cycloaddition of sydnones with arynes is described. Novel access to sydnones and poly-(hetero)aromatic aryne precursors allowed the introduction of chemical diversity over multiple positions of the helical scaffolds. The origins of the unconventional regioselectivity during the cycloaddition steps was systematically investigated using density functional theory (DFT) calculations, unveiling the key features which control this reactivity, namely face-to-face ($\pi$…$\pi$) or edge-to-face (C-H…$\pi$) interactions, primary orbital interactions and distortion from coplanarity in the transition structures (TSs) of the transformation. From the library of 24 derivatives synthesized, a pyridyl containing derivative displayed reversible, red-shifted, pH triggered chiroptical switching properties, with CPL-sign reversal. It is found that protonation of the helicene causes a change of the angle between the electric and magnetic dipole moments related to the S$_1$ → S$_0$ transition, resulting in this rare case of reversible CPL sign inversion upon application of an external stimulus.
https://hal-cea.archives-ouvertes.fr/cea-03563860 Contributor : Serge PalacinConnect in order to contact the contributor Submitted on : Thursday, February 10, 2022 - 7:43:10 AM Last modification on : Saturday, February 12, 2022 - 3:39:26 AM Long-term archiving on: : Wednesday, May 11, 2022 - 6:10:46 PM
Expédite Yen-Pon, Floris Buttard, Lucas Frédéric, Pierre Thuéry, Frédéric Taran, et al.. Hetero-helicenes synthesis through 1,3-dipolar-cycloaddition of sydnones with arynes: Synthesis, origins of selectivity and application to pH triggered chiroptical switch with CPL-sign reversal. 2022. ⟨cea-03563860⟩