Benzosultam Synthesis by Gold(I)-Catalyzed Ammonium Formation/Nucleophilic Substitution.

The synthesis of benzosultams has been achieved through a gold(I)-catalyzed ammonium formation strategy. Starting from easily available N-(2-alkynyl)phenylsulfonyl azetidine derivatives, a cyclization reaction generated a spiroammonium gold intermediate that was ring-opened by nucleophilic alcohol or indole. This new methodology is compatible with the large variation in the substrates and nucleophiles and allowed the formation of benzosultams in high yield (18-98%, 20 examples). This strategy also allowed the preparation of benzosultam analogs via iododeauration and subsequent cross-coupling reactions.