Stereochemistry of the Isomerization of N-Acyl-2,3-Disubstituted Aziridin.es to A2-Oxazolines

Abstract

The iodide ion catalyzed isomerization of cis- and trans-1-acetyl and 1-aroyl-2,3-disubstituted aziridines to δ2-oxazolines has been studied. The rearrangement is stereoselective, the selectivity, being greater with trans-aziridines than with cis-aziridines. The former yield 90-95% trans- and 10-5% cis- δ2-oxazolines while the latter give 40-90% cis and 60-10% trans. The selectivity of isomerization for m-1-aroylaziridines was found to vary with the iodide ion concentration and the solvent system employed while the ratio of δ2-oxazolines formed from the corresponding trans-aziridines was unaffected. Using tetrabutylammonium iodide as the isomerization catalyst also affected the δ2-oxazoline isomer distribution. The stereochemical outcome of this reaction was found to be insensitive to the size of the 2,3-dialkyl substituents and to resonance effects. The ratio of isomers formed was determined by glpc, while stereochemical configurations were elucidated by means of nmr spectroscopy. © 1970, American Chemical Society. All rights reserved.