Efficient access to chiral N-substituted saccharin analogues via the directed ortho-lithiation of 3-N-arylsulfonyloxazolidin-2-ones

Chiral 3-N-arylsulfonyloxazolidin-2-ones 1a–f, prepared from (l)-amino acids, were reacted with lithium diisopropylamide in anhydrous THF and HMPA. The resulting new, optically active benzisothiazolinone 1,1-dioxides 2a–c and naphthisothiazolinone 1,1-dioxides 2d–f were obtained in good yields.