Nitrogen protection sulfonamide formation

Protection of Nitrogen Formation of Sulfonamides. Unlike the corresponding arenesulfonyl chlorides, benzenesulfonyl bromide has been used much less extensively in organic synthesis. Primary amines and imidazoles (eq 1) have been converted to the corresponding benzenesulfonamides and, with indoles, bromi-nation at C-3 occurs with concomitant sulfonamide formation (eq 2). ... 

Construction of the thiomorpholine moiety starts by protection of the carboxylic acid in penicillamine (102) by reaction with hexyl dimethylsUane (Dmhs). Condensation of 103 with 1,2-dichloroethane leads to formation of the heterocychc ring by sequential displacement of halogen by nitrogen and sulfur to yield 104. Reaction of intermediate 104 with the benzophe-none (101), leads to formation of the sulfonamide (105). Mild acid then serves to reveal the free carboxyhc acid (106). This function is then converted to the acid chloride with oxalyl chloride. Treatment of this reactive intermediate with hydroxylamine leads to acylation on nitrogen to afford the proteinase inhibitor 107. ... 

A variety of nucleophilic nitrogens can undergo pyrrole formation with dialkoxytetrahydrofurans. Anilines, amides, sulphonamides, and alkyl amines all react cleanly to form substituted pyrroles. With judicious choice of amides or sulfonamide a variety of N-H protected pyrroles can be generated in short order. 

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