2- and 4-Nitrobenzenesulfonamides: Exceptionally versatile means for preparation of secondary amines and protection of amines

2- and 4-Nitrobenzenesulfonamides, readily prepared from primary amines, undergo smooth alkylation by Mitsunobu reaction or by conventional methods to give N-alkylated sulfonamides in near quantitative yields. These sulfonamides could be deprotected readily via Meisenheimer complexes upon treatment with thiolates in DMF at room temperature, giving secondary amines in high yields.