The conversion of a wide range of carboxylic acids into their acyl imidazolides with subsequent addition of an aziridine rapidly gives a quantitative yield of the corresponding N- acyl aziridines. Iodide (or bromide) ion catalysed rearrangement of N-acyl 2 (S)- benzylaziridines 1 to oxazolines 6 proceeds quantitatively.
