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Trifluoromethylation of camphorquinone and its monoimine derivatives


Obijalska, E; Mloston, G; Linden, A; Heimgartner, H (2008). Trifluoromethylation of camphorquinone and its monoimine derivatives. Tetrahedron: Asymmetry, 19(14):1676-1683.

Abstract

Treatment of (1R)-camphorquinone 2 with (trifluoromethyl)trimethylsilane in the presence of catalytic amounts of caesium fluoride in DME at room temperature yields two pairs of exo/endo isomers of trifluoromethylated silylated alcohols 5 and 6. In this case, nucleophilic addition of the CF3 anion occurs neither regio- nor stereoselectively. On the other hand, the analogous reaction with (1R)-camphorquinone 3-imines 3, followed by hydrolysis with 5 M HCl in ethanol, leads stereoselectively to (1R,2S)-2-hydroxy-2-(trifluoromethyl)bornan-3-one 8. The attempted reductions of the intermediate adducts with NaBH4 in ethanol gave the corresponding (1R,2S)-3-imino-2-(trifluoromethyl)bornan-2-ols 9 as the sole isomers in high yield. The configuration of C(2), that is, the endo course of the nucleophilic CF3 addition, was proven by X-ray crystallography. Furthermore, the reduction of the Cdouble bond; length as m-dashN bond in 9 with DIBAL-H leads stereoselectively to the exo amino derivatives 10, which, by treatment with phosgene, smoothly form the fused 1,3-oxazolidin-2-ones 11. In contrast, the reduction of ketone 8 yields a mixture of the exo,exo- and exo,endo-2,3-diols 12.

Abstract

Treatment of (1R)-camphorquinone 2 with (trifluoromethyl)trimethylsilane in the presence of catalytic amounts of caesium fluoride in DME at room temperature yields two pairs of exo/endo isomers of trifluoromethylated silylated alcohols 5 and 6. In this case, nucleophilic addition of the CF3 anion occurs neither regio- nor stereoselectively. On the other hand, the analogous reaction with (1R)-camphorquinone 3-imines 3, followed by hydrolysis with 5 M HCl in ethanol, leads stereoselectively to (1R,2S)-2-hydroxy-2-(trifluoromethyl)bornan-3-one 8. The attempted reductions of the intermediate adducts with NaBH4 in ethanol gave the corresponding (1R,2S)-3-imino-2-(trifluoromethyl)bornan-2-ols 9 as the sole isomers in high yield. The configuration of C(2), that is, the endo course of the nucleophilic CF3 addition, was proven by X-ray crystallography. Furthermore, the reduction of the Cdouble bond; length as m-dashN bond in 9 with DIBAL-H leads stereoselectively to the exo amino derivatives 10, which, by treatment with phosgene, smoothly form the fused 1,3-oxazolidin-2-ones 11. In contrast, the reduction of ketone 8 yields a mixture of the exo,exo- and exo,endo-2,3-diols 12.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:July 2008
Deposited On:06 Feb 2009 13:36
Last Modified:05 Apr 2016 12:57
Publisher:Elsevier
ISSN:0957-4166
Funders:Polish Ministry for Science and Higher Education, F. Hoffmann-La Roche AG, Basel
Publisher DOI:https://doi.org/10.1016/j.tetasy.2008.07.003

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