RESUMO
Using sulfur-containing nucleophiles in halocyclization has been underexplored notwithstanding their potential to generate novel S-heterocycles and despite the extensive exploration of oxygen, nitrogen, and carbon nucleophiles. In this study, we focused on the bromocyclization of alkenoic thioesters with N-bromoacetamide, which leads to the formation of cyclic bromosulfides. Investigation into the mechanistic pathways of these reactions revealed that the sulfur atom behaves as a nucleophile, leading to S-acetylsulfonium intermediates. HBr and Br2 played significant roles in these transformations.
RESUMO
Although oxygen, nitrogen, and carbon have been extensively studied as nucleophilic elements in the halocyclization of alkenes, sulfur-based nucleophiles are relatively unexplored. Herein, we investigated bromocyclization chemistry involving unsaturated thioesters, with a focus on their use as potential S-nucleophiles. We developed a bromocyclization method that uses alkenoic thioesters and N-bromoacetamide (NBA) to form cyclic bromosulfides. The resulting 5-exo products are labile and can be used in various nucleophilic substitution reactions.