Under phase-transfer or low-temperature conditions, the ylide generated from diphenylsulfonium salt 2 readily reacts with N -sulfonylimines 1 to give acetylenylaziridines in excellent yields, but low to moderate cis/trans selectivity. When using n -BuLi as the base to generate the ylide at low termperature, product 3 with an intact silyl protecting group is obtained. t -BuOK, however, leads to desilylation product 4 . With Cs 2 CO 3 as the base, dimethylsulfonium salts 6, 21, and 22 show much better cis/trans selectivity (>98:2) than diphenylsulfonium salt 2 . The asymmetric version of the above aziridination reaction using camphor-derived sulfonium salts 12 − 14 and 20 gives chiral aziridines with ee values up to 85%. Both (2 R,3 S )-(−)- 3 and (2 S,3 R )-(+)- 3 can be prepared from 12 / 20 or 13 / 14, respectively. Ylides produced from telluronium salt 7 failed to react with imine 1a at room temperature, but the reaction succeeded at low temperature. Arsonium ylides from 8 cannot react with N -sulfonylimines under both sets of conditions.
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Li et al. (1998) studied this question.