ZINC(II)-CATALYZED TRANSFORMATION OF EPOXIDES TO AZIRIDINES

The Lewis acid-catalysed transformation of epoxides to aziridines with iminophosphoranes as the nitrogen-fragment donor has been investigate d. Of the Lewis acids tested, zinc(II) complexes had the best catalyti c properties. The method works best for terminal and cyclic epoxides, internal epoxides being less reactive. Of the various iminophosphorane s employed N-(triphenylphosphoranylidene)-aniline and -isopropylamine were the most successful. The zinc(II)-catalysed reaction has been stu died for chiral styrene oxides for which the enantiomeric excess of th e aziridine produced is dependent on the reaction time. The reaction o f achiral and chiral styrene brides and N-(triphenylphosphoranylidene) aniline in the presence of a zinc(II) complex having a chiral ligand h as been investigated as has the reaction for cis-deuteriostyrene oxide in order to obtain information about the stereochemical outcome of th e reaction. A mechanism for the title reaction is discussed on the bas is of the experimental results.