Reaktionen von Steroiden mit Dialkylaminoschwefeltrifluoriden. I. 11β-Hydroxysteroide. Über STeroide, 233. Mitteilung |
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Authors: | Michel Biollaz Jaroslav Kalvoda |
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Abstract: | Reactions of Steroids with Dialkylaminosulfur Trifluorides. I. 11β-Hydroxysteroids. Reactions of three types of 11β-hydroxy steroids with dialkylaminosulfur trifluorides (DAST) have been studied. 9Δ-unsubstituted 11-alcohols are dehydrated with DAST to Δ9(11)-unsaturated compounds under very mild conditions. 9α-Chloro-11β-hydroxy steroids are quantitatively fluorinated in position 11 yielding the known 9α-chloro-11β-fluoro derivatives. Finally, 9α, 11Δ-fluorohydrins at 0–25° are selectively transformed with DAST into Δ11-9α-fluorides. When the latter reaction is run at lower temperature, the corresponding 11-piperidinesulfinates, products of partial hydrolysis of the alkoxy-dialkylaminosulfur difluoride intermediates postulated by Middleton, can be isolated in high yields. A rational explanation of the results is presented. |
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