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Updated: Jul 3, 2025

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
The First Example of the Friedel-Crafts Cyclization Leading to (10-Hydroxy-9,10-dihydroanthr-9-yl)phosphonium Salts
Krzysztof Owsianik1, Ewa Różycka-Sokołowska2, Marek Koprowski1
1Division of Organic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łódź, Poland.
Abstract:
The reaction of (ortho-acetalaryl)arylmethanols with various phosphines PR1R2R3 (R1 = R2 = R3 = Ph; R1 = R2 = Ph, R3 = Me and R1 = R2 = Me, R3 = Ph) under acidic conditions (e.g., HCl, HBF4, TsOH) unexpectedly led to the formation of (10-hydroxy-9,10-dihydroanthr-9-yl)phosphonium salts instead of the corresponding anthryl phosphonium salts. The cyclization occurred according to the Friedel-Crafts mechanism but without the usually observed Bradsher dehydration, giving cyclic products in the form of cis/trans isomers and their conformers. In case of electron-rich and less-hindered dimethylphenylphosphine, all four stereoisomers were recorded in 31P{1H} NMR spectra, while for the other phosphines, only the two most stable cis/trans stereoisomers were detected. This study was supported by DFT and NCI calculations in combination with FT-IR analysis.
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