Deprotection of Sulfonyl Aziridines

The deprotection of the chiral N-sulfonyl aziridines 1-3 has been studied under different desulfonylation conditions. Two methods for the efficient deprotection of 2-benzyl-, 2-phenyl-, and 2-carboxyl-N-sulfonylaziridines were found. The desulfonylation with lithium and a catalytic amount of di-tert-butyl biphenyl in THF at -78 °C led to the corresponding NH aziridines with yields up to 85%. Alternatively, the desulfonylation could be carried out with magnesium in methanol under ultrasonic conditions. The latter proved to be a very mild method and afforded the desulfonylated aziridines with yields up to 75%, even when the 2-phenyl substituted aziridine 2 was the studied substrate. Furthermore, in all the cases studied, no racemization was observed in the chiral center of the aziridines.