Deoxyfluorination of α-N-phthaloyl cycloalkanones with bis(2-methoxyethyl)aminosulfur trifluoride (Deoxo-Fluor)

The deoxyfluorination of alpha-N-phthaloyl cyclobutanone with bis(2-methoxyethyl)aminosulfur trifluoride (Deoxo-Fluor) produced a gem-difluoride product together with a vic-difluoride bearing a cyclopropane ring. In contrast, the deoxyfluorination of the corresponding alpha-N-phthaloyl cyclopentanone produced the gem-difluoride only. Furthermore, the deoxyfluorination of the corresponding alpha-N-phthaloyl cyclohexanone produced an intramolecular cyclization product with two fluorine atoms as the main product, which provided the starting material after workup. Cationic species formed through neighboring group participation are most likely the key intermediates in these reactions. Control experiments using N-benzoyl congeners produced oxazole or oxazoline derivatives, indicating that the presence or absence of a hydrogen atom on the protected amine moiety was critical to determining the reaction path. (C) 2015 Elsevier B.V. All rights reserved.