Access to 2-Fluorinated Aziridine-2-phosphonates from α , α -Halofluorinated β -Iminophosphonates-Spectroscopic and Theoretical Studies.

The efficient one-pot halofluorination of a β -enaminophosphonate/ β -iminophosphonate tautomeric mixture resulting in α , α -halofluorinated β -iminophosphonates is reported. Subsequent imine reduction gave the corresponding β -aminophosphonates as a racemic mixture or with high diastereoselectivity. The proposed protocol is the first example of a synthesis of N -inactivated aziridines substituted by a fluorine and phosphonate moiety on the same carbon atom. Based on spectroscopic and theoretical studies, we determined the cis / trans geometry of the resulting fluorinated aziridine-2-phosphonate. Our procedure, involving the reduction of cis/trans -fluoroaziridine mixture 24 , allows us to isolate chiral trans- aziridines 24 as well as cis- aziridines 27 that do not contain a fluorine atom. We also investigated the influence of the fluorine atom on the reactivity of aziridine through an acid-catalyzed regioselective ring-opening reaction. The results of DFT calculations, at the PCM/ωB97x-D/def2-TZVPD level of theory, are in good agreement with the experiments. The transition states of the S N 2 intramolecular cyclization of vicinal haloamines have been modeled.