Reaktionen von Steroiden mit Dialkylaminoschwefeltrifluoriden . I. 11β‐Hydroxysteroide. Über STeroide, 233. Mitteilung

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 Δ 9(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 Δ 11 ‐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.