A concise and inexpensive route to 2-cyano aziridine-2-carboxylates and 2,2-dicyano aziridines is reported by reaction of the easily obtainable corresponding a,b-unsaturated nitriles with sulfonyloxycarbamates in the presence of calcium oxide.

[reaction: see text] Unexpectedly, imidazolidin-2-ones are easily obtained from beta-keto esters upon treatment with tert-butyl nosyloxycarbamate and calcium oxide under mild conditions. The structure of the product was established by X-ray crystallography.

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Nosyloxycarbamates react with unsaturated b-dicarbonyl compounds at room temperature in the presence of calcium oxide to give N-alkoxycarbonyl aziridines in high yield.Aziridines have found widespread application in organic synthesis. Their value for preparative chemists is based on the high reactivity to give a variety of ring-opened or ringexpanded nitrogen-containing compounds. An electronwithdrawing group on the aziridine nitrogen plays a fundamental role in ring-opening reactions, which frequently occur with high regio-and stereoselectivity, depending on the ring substituents. 1Among the methods to obtain aziridines, the use of azides or carbamates as precursors of electrophilic nitrenes was reported in the reactions on electron-rich olefins 2 also by us. 3 Moreover, we found that arenesulphonyloxycarbamates (ArSO 3 NHCO 2 Et), used without catalyst in the presence of inorganic bases, 4 were suitable aziridination agents for both electron-rich and electron-poor olefins, in the last cases very likely through an aza-Michael addition. 5 Recently arenesulphonyloxycarbamates have been used by Hanessian 6 in the presence of sodium hydride in tetrahydrofuran at -40 °C to give unexpectedly an alkoxyaminocarbonylation of saturated b-dicarbonyl compounds. Nevertheless, starting from the same substrates we were able to perform direct electrophilic aminations. This was carried out using NsONHCO 2 Et in the presence of calcium oxide in dichloromethane at room temperature. 7 During this study we discovered a useful aziridination reaction and we now wish to describe this simple, fast one-pot synthesis of aziridines with NsONHCO 2 R starting from good Michael acceptors like 1,1-disubstituted olefins (Table). All reactions were performed in CH 2 Cl 2 in the presence of CaO at room temperature, using tert-butyl nosyloxycarbamate (NsONHCO 2 Bu-t) or ethyl nosyloxycarbamate (NsONHCO 2 Et) (Scheme). SchemeAfter stirring for 30-60 minutes and addition of petroleum ether, simple filtration of the crude mixtures gave the corresponding aziridines in high purity, as confirmed by 1 H and 13 C NMR spectra. Moreover, the aziridines can be easily isolated by flash chromatography on silica gel.Both considered nosyloxycarbamates showed similar reactivity. With oxo enoates (Entries 1-3) almost equimolar quantities and short reaction times were needed. With a bdiketone (Entry 5) and malonates (Entries 6 and 7) an excess of CaO and the reagent were required. Lower yields were obtained in the aziridination of a cyclic sulphonyl enone (Entry 9). Tetrasubstituted olefins (Entries 4 and 8) did not react under our conditions probably due to steric hindrance.We believe that the enhanced reactivity of 1,1-disubstituted olefins here reported, compared with previous results on a,b-unsaturated ketones, 8 may validate the aza-Michael pathway we proposed for the aziridination of nitroalkenes. 5In conclusion, the methodology reported in this paper provides an efficient and high-yielding route to substituted Nprotected aziridines under mild conditions. GC ...

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