Mechanistic Studies on Bromocyclization of Unsaturated Thioester by Density Functional Theory and Experiment.

Using sulfur-containing nucleophiles in halocyclization has been underexplored notwithstanding their potential to generate novel -heterocycles and despite the extensive exploration of oxygen, nitrogen, and carbon nucleophiles. In this study, we focused on the bromocyclization of alkenoic thioesters with -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 -acetylsulfonium intermediates. HBr and Br played significant roles in these transformations.