Aziridines, the nitrogenous analogues of epoxides, have until recently excited far less interest amongst synthetic organic chemists than their oxygenated counterparts, with some justification. A range of reviews concerned with the physical properties, synthesis (asymmetric and otherwise), reactions and utility of aziridines exists; this review briefly summarizes the similarities and differences between oxiranes and their nitrogenated analogues, concentrating on the underlying properties of aziridines and recent developments in their chemistry. In addition to descriptions of the physical nature of aziridines, especially those features which underpin their utility as synthetic intermediates, the sections beneath describe reactions involving alkylative ring-opening and synthesis of aziridines.

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Rearrangement reactions occupy a special place within the canon of organic synthesis, by virtue of the inherently high efficiency of chemical processes which form and break bonds by redistribution of electrons around a retained atomic framework. Within the broader class, sigmatropic rearrangements are chemical processes defined by mechanisms involving unimolecular migration of sigma-bonds with concomitant redistribution of one or more pi-bonds. Sigmatropic processes may involve uncharged or charged species, with the charges located on carbon or heteroatoms; the latter reaction type is the subject of this tutorial review.

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The first examples of highly enantioselective [2,3]-sigmatropic rearrangements of acyclic allylic ammonium ylids are reported. Thus, a range of N-{2'-[(N'-allyl-N',N'-dialkyl)ammonium]}acetyl camphor sultams undergo rearrangement at 0 degrees C in DME solution with high diastereofacial control (up to 99:1 dr) to give allylglycines in generally high yield. The power of the method has been demonstrated in a rapid and efficient synthesis of (R)-allyl glycine.

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Supporting informationNMR data (E)-3-p-Tolylacrylic acid methyl ester 17a..