Reaction of quinidine acetate, epiquinidine and its acetate in superacid: formation of gem-difluoro derivatives with or without rearrangement |
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Authors: | Sébastien Debarge Marie-Paule Jouannetaud Jean-Claude Jacquesy Alain Cousson |
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Institution: | a Laboratoire ‘Synthèse et Réactivité des Substances Naturelles’, UMR 6514, 40, Avenue du Recteur Pineau, F-86022 Poitiers Cedex, France b Laboratoire Léon Brillouin-CEA Saclay, 91191 Gif-sur-Yvette Cedex, France |
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Abstract: | In HF-SbF5, quinidine 1a or its dihydrochloride cyclises previously obtained with usual acids. A similar reaction is observed in the presence of CCl4. Under similar conditions quinidine acetate 1b and epiquinidine acetate 2b dihydrochlorides both yield 10,10-difluoro derivatives epimeric at C-3, 6 and 7, and 9c and 10b, and a rearranged difluoro derivative 8b and 11b, respectively. Epiquinidine 2a leads to the expected analogues 10a and 11a and to a ketone 9a. Formation of gem-difluoro compounds implies chloro intermediates at C-10, precursors of α-chlorocarbenium ions, which are trapped by a fluoride ion and which lead by halogen exchange to the products. |
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Keywords: | Quinidine Fluoration Rearrangement Superacid |
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