Yashmin S, Khan AT, Akula SJ, P R, Bhattacharyya K. One-Step Synthesis of 7-Bromobenzo[
c]chromeno[4,3,2-
gh]phenanthridines through a Sequential Bromination/Cyclization/Aromatization Reaction Using
N-Bromosuccinimide (NBS).
J Org Chem 2023;
88:13622-13633. [PMID:
37738657 DOI:
10.1021/acs.joc.3c01329]
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Abstract
Herein, metal- and oxidant-free synthesis of 7-bromobenzo[c]chromeno[4,3,2-gh]phenanthridines is reported using N-bromosuccinimide. Sequential regioselective bromination, intramolecular ring cyclization, and aromatization reactions occur in a single step through a successive radical-catalyzed pathway. The mechanistic pathway for the cyclization is supported by a DFT study. Selective bromination in the fully aromatic skeleton is accomplished without involving additional aromatic electrophilic ring bromination. As a synthetic application, the Suzuki coupling reaction of compound 5a with boronic acid is reported to get compound 8a. Aggregation-induced emission of one of the synthesized compounds (5h) is also investigated in THF/hexane solvent along with concentration-dependent emission spectroscopy.
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