SbF5‐Mediated Cyclization of Polyfluorinated 1,1‐Diphenylethanes to Polyfluoro‐9‐Methylfluorenes: Revealed Dihydrofluorene Intermediates and Bifluorene Products

SbF5‐Mediated Cyclization of Polyfluorinated 1,1‐Diphenylethanes to Polyfluoro‐9‐Methylfluorenes: Revealed Dihydrofluorene Intermediates and Bifluorene Products Full article

Journal

ChemistrySelect
ISSN: 2365-6549

Output data

Year: 2025, Volume: 10, Number: 22, Article number : e01998, Pages count : DOI: 10.1002/slct.202501998

Tags

Antimony pentafluoride; Carbocation; Cyclization; Fluorene; Polyfluorinated

Authors

Komarov Vladislav V. ¹ , Krasnov Vyacheslav I. ¹ , Karpov Victor M. ¹ , Zonov Yaroslav V. ¹ , Parkhomenko Dmitriy A. ¹ , Mezhenkova Tatyana V. ¹

Affiliations

1	N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev Ave. 9, Novosibirsk 630090, Russia

A series of isomeric 1-(2,3,5,6-tetrafluorophenyl)-1-(tetrafluorophenyl)tetrafluoroethanes was synthesized by an SbF5-mediated alkylation of the corresponding tetrafluorobenzenes with 1,2,4,5-tetrafluoro-3-(perfluoroethyl)benzene. These diphenylethanes were shown to undergo cyclization to fluorenes under the action of antimony pentafluoride. Specifically, upon heating with SbF5 at 50 °C, the diphenylethane obtained from 1,2,3,4-tetrafluorobenzene yielded 1,2,3,4,5,7,8,9-octafluoro-9-(trifluoromethyl)fluorene as the major reaction product, the minor being 1,2,4,5,6,7,9-heptafluoro-9-(trifluoromethyl)fluorene. In the case of the diphenylethane obtained from 1,2,4,5-tetrafluorobenzene, the cyclization occurs at r.t., and in addition to target 1,2,4,5,7,8,9-heptafluoro-9-(trifluoromethyl)fluorene, the reaction gave some polyfluorinated dihydro- and tetrahydrofluorenes. As to the diphenylethane obtained from 1,2,3,5-tetrafluorobenzene, the isomer being the most reluctant to undergo the cyclization, the transformation required higher temperatures or longer times: at 50 °C the reaction occurred with incomplete conversion resulting mostly in dihydrofluorenes, whereas at 70–90 °C the reaction yielded 1,2,3,5,7,8,9-heptafluoro-9-(trifluoromethyl)fluorene and a polyfluorinated 9,9′-bis(trifluoromethyl)-9H,9′H-2,3′-bifluorene. From diphenylethanes synthesized in this study, the corresponding diphenylethyl cations were generated. The structure of the reaction products and cations was determined by 1H, 19F, 13C NMR, 19F–19F COSY, 1H–19F HMBC, and 19F–1H HOESY spectroscopy.

Komarov V.V. , Krasnov V.I. , Karpov V.M. , Zonov Y.V. , Parkhomenko D.A. , Mezhenkova T.V.
SbF5‐Mediated Cyclization of Polyfluorinated 1,1‐Diphenylethanes to Polyfluoro‐9‐Methylfluorenes: Revealed Dihydrofluorene Intermediates and Bifluorene Products
ChemistrySelect. 2025. V.10. N22. e01998 . DOI: 10.1002/slct.202501998 WOS OpenAlex

Submitted:	Apr 3, 2025
Accepted:	May 23, 2025
Published print:	Jun 6, 2025
Published online:	Jun 6, 2025

Web of science:	WOS:001503608800001
OpenAlex:	W4411088529

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