Twofold π‑Extension of Polyarenes via Double and Triple Radical Alkyne peri-Annulations: Radical Cascades Converging on the Same Aromatic Core

• Published in: Journal of the American Chemical Society Vol. 142; no. 18; pp. 8352 - 8366
• Main Authors: Gonzalez-Rodriguez, Edgar, Abdo, Miguel A, dos Passos Gomes, Gabriel, Ayad, Suliman, White, Frankie D, Tsvetkov, Nikolay P, Hanson, Kenneth, Alabugin, Igor V
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 06.05.2020; Amer Chemical Soc
• Subjects: alkynes; carbon-hydrogen bond activation; chemical bonding; Chemistry; Chemistry, Multidisciplinary; cross-coupling reactions; fluorescence; iodination; Physical Sciences; polycyclic aromatic hydrocarbons; regioselectivity; Science & Technology; solubility; solvents; DENSITY FUNCTIONALS; TRACELESS DIRECTING GROUPS; HYDROSTANNATION; BENZANNULATION; PYRENE; GRAPHENE QUANTUM DOTS; RAPID ACCESS; SINGLET FISSION; NONCOVALENT INTERACTIONS; NANOGRAPHENES
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.0c01856

A versatile synthetic route to distannyl-substituted polyarenes was developed via double radical peri-annulations. The cyclization precursors were equipped with propargylic OMe traceless directing groups (TDGs) for regioselective Sn-radical attack at the triple bonds. The two peri-annulations converge at a variety of polycyclic cores to yield expanded difunctionalized polycyclic aromatic hydrocarbons (PAHs). This approach can be extended to triple peri-annulations, where annulations are coupled with a radical cascade that connects two preexisting aromatic cores via a formal C–H activation step. The installed Bu3Sn groups serve as chemical handles for further functionalization via direct cross-coupling, iodination, or protodestannylation and increase solubility of the products in organic solvents. Photophysical studies reveal that the Bu3Sn-substituted PAHs are moderately fluorescent, and their protodestannylation results in an up to 10-fold fluorescence quantum yield enhancement. DFT calculations identified the most likely possible mechanism of this complex chemical transformation involving two independent peri-cyclizations at the central core.