Note pubs.acs.org/joc
Stereoselective Synthesis and ROESY 1H NMR Study of Bidiaziridines Laura Carroccia, Maurizio Delfini, Stefania Fioravanti,* Lucio Pellacani,* and Fabio Sciubba Dipartimento di Chimica, Università degli Studi “La Sapienza”, P.le A. Moro 5, I-00185 Roma, Italy S Supporting Information *
ABSTRACT: The bisaziridination reaction of symmetric (E-strans-E)-α-diimines using ethyl nosyloxycarbamate as aminating agent yields symmetrically functionalized bidiaziridines, under mild conditions. The reactions take place with very high stereoselectivity giving only bidiaziridines with total retention of the starting α-diimine configuration, as determined by NMR measurements. Moreover, only a single pure diastereomer, derived from attack of the aza-anion on the opposite faces of conjugate system was obtained, starting from chiral substrates. ROESY analyses clearly show that all nitrogens have a stable pyramidal conformation, and the absolute configurations of new chiral centers were assigned.
B
According to reported X-ray crystallographic analyses and molecular modeling studies,9,10,15 all the α-diimines were obtained as a single diastereomer (E-s-trans-E)-1, as confirmed by 1H NMR spectra performed on the crude mixtures. With the aim of fixing the optimal reaction conditions, the aziridination reaction was tested on the diimine 1a. The reaction was performed following our already tested reaction conditions, using a molar ratio of substrate/NsONHCO2Et = 1:2, CH2Cl2 as solvent and working in the absence of an added base at room temperature. These conditions did not give any amination product, probably due to the decrease of the basicity of nitrogen atoms in the conjugated imines. By increasing the molar amount of the aminating agent (up to 3-fold), the bisaziridination product was obtained in very low yields (
