An Access to Benzo[a]fluorenes, Benzo[b]fluorenes, and Indenes Triggered by Simple Lewis Acid

Kishore, Dakoju Ravi and Goel, Komal and Satyanarayana, G. and et al, . (2022) An Access to Benzo[a]fluorenes, Benzo[b]fluorenes, and Indenes Triggered by Simple Lewis Acid. The Journal of Organic Chemistry, 87 (5). pp. 2178-2203. ISSN 0022-3263

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This report illustrates BF3·OEt2 promoted intramolecular cascade cycloaromatization of 1,7-ynones toward synthesizing structurally diverse benzofluorene scaffolds. Remarkably, the present protocol promotes the formation of two consecutive C-C bonds intramolecularly and undergoes aromatization under mild reaction conditions to afford the tetracyclic benzo[a]fluorene frameworks. Besides, the formation of indenes was observed when 1-bromo-2-iodoarenes are relatively more electron-rich when compared with the one originating from the terminal arylacetylenes, under controlled conditions, wherein triple bond polarity has been just reversed due to the change of electronic effects exerted by the strong +M group of 1-bromo-2-iodoarenes, which is in conjugation to the connected triple bond. The same concept to generate indenes has also been extended by using aliphatic alkyne tethered ynones. Further, it was noticed that 1,7-ynones bearing the more electron-rich 1-bromo-2-iodoarenes than the arene ring arriving from the terminal arylacetylenes lead to benzo[b]fluorenes, under thermodynamic conditions, instead of delivering the benzo[a]fluorenes. In addition, this method features metal-free conditions, easily accessible starting materials, operational simplicity, gram-scale synthesis, and a wide range of substrate scopes. © 2022 American Chemical Society

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IITH Creators:
IITH CreatorsORCiD
Satyanarayana, G.UNSPECIFIED
Item Type: Article
Additional Information: We greatly acknowledge the financial support from DST-SERB (Department of Science and Technology, Science and Engineering Research Board, Grant EMR/2017/005312), New Delhi. D.R.K., K.G., and C.S. gratefully acknowledge UGC and CSIR, respectively, for providing fellowships.
Uncontrolled Keywords: Arylacetylenes; C-C bonds; Cycloaromatization; Electron-rich; Fluorenes; Iodoarenes; Lewis Acid; Mild reaction conditions; Simple++; Triple bonds
Subjects: Chemistry
Divisions: Department of Chemistry
Depositing User: . LibTrainee 2021
Date Deposited: 22 Jul 2022 06:15
Last Modified: 22 Jul 2022 06:15
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