Catalytic asymmetric heterogeneous aziridination of alkenes using zeolite CuHY with [N-(p-tolylsulfonyl)imino]phenyliodinane as nitrene donor

Copper-exchanged zeolite Y (CuHY) is found to be a highly effective heterogeneous catalyst for the aziridination of alkenes using [N-(p-tolylsulfonyl)imino]phenyliodinane (PhI=NTs) as the nitrogen source. Exchange of zeolite Y with other cations (Ag+, Co2+, Fe3+, Mg2+, Ni2+, Zn2+) was found to be ineffective. This is considered to be due to the ability of these metals to catalyse the breakdown of the PhI=NTs reagent into iodobenzene and toluene sulfonamide. Modification of the CuHY catalyst with bis(oxazolines) leads to preparation of the first heterogeneous enantioselective aziridination catalyst and the results showing the effect of temperature and modifier concentration are described and discussed. A pyridine-bridged bis(oxazoline) was observed to give the highest enantioselectivity of 61% ee for the aziridination of styrene using acetonitrile as solvent and at -10 degrees C.