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

The efficient one-pot halofluorination of a -enaminophosphonate/-iminophosphonate tautomeric mixture resulting in ,-halofluorinated -iminophosphonates is reported. Subsequent imine reduction gave the corresponding -aminophosphonates as a racemic mixture or with high diastereoselectivity. The proposed protocol is the first example of a synthesis of -inactivated aziridines substituted by a fluorine and phosphonate moiety on the same carbon atom. Based on spectroscopic and theoretical studies, we determined the / geometry of the resulting fluorinated aziridine-2-phosphonate. Our procedure, involving the reduction of -fluoroaziridine mixture , allows us to isolate chiral aziridines as well as aziridines 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 S2 intramolecular cyclization of vicinal haloamines have been modeled.