Aziridination of ?,?-unsaturated esters bearing allylic hydroxy groups with 3-acetoxyaminoquinazolinones: evidence for a mechanism comprising Michael addition?SN2 nucleophilic displacement of acetoxy for aziridination of ?,?-unsaturated esters

Aziridinations of the allylic alcohol-bearing alpha,beta-unsaturated esters 6 and 7 and their corresponding acetates 8 and 9 have been carried out under standard conditions using 3-acetoxyaminoquinazolinone 2. Whereas the preferred sense of diastereoselectivity in aziridination of allyl alcohol 6 is inverted by comparison with its acetate 8, the preferred sense of diastereoselectivity is retained in aziridination of allylic alcohol 7 by comparison with its acetate 9, A mechanism is proposed for aziridinations of alpha,beta-unsaturated esters in which Michael addition of the N-acetoxy nitrogen to the beta-position of the ester runs ahead of S(N)2-type nucleophilic displacement of the acetoxy group from nitrogen.