to catalyze asymmetric aziridination using azide compounds carrying p-nitrobenzenesulfonyl and 2-(trimethylsilyl)ethanesulfonyl (SES) groups, which are easily removable N-protecting groups under mild conditions, as a nitrene precursor in a highly enantioselective manner. In particular, the reactions with SES azide showed excellent enantioselectivity greater than 90% ee, except for one example.
Design of a robust Ru(salen) complex: aziridination with improved turnover number using N-arylsulfonyl azides as precursorsElectronic supplementary information (ESI) available: typical experimental procedures, determination of enantiomeric excess and elementary analysis for complexes 3 and 5. See http://www.rsc.org/suppdata/cc/b4/b407693a/
A new robust fluorinated (OC)Ru(salen) complex was designed on the basis of an X-ray structure of its parent complex to show improved turnover numbers (up to 878) and enantioselectivities (up to 99%) in aziridination reactions using p-toluenesulfonyl (Ts) or p-nitrobenzenesulfonyl (Ns) azide as the nitrene precursor; the latter is synthetically advantageous since the Ns group is N-protecting and can
higher than that for the equivalent homogeneously catalysed reaction. With copper-exchangedzeolite Y the leaching of Cu2+ into solution during reaction was much lower for the substituted styrene derivatives (0.4-7% of total Cu) than with styrene itself (10.3% of the total Cu). The effect of reaction time on aziridine yield reveals an S-shaped profile that is accentuated by the position of the substituent