Gold‐Catalyzed Cycloisomerization–Halogenation Sequence of 1,3‐Enyne Esters with NXS: Efficient Synthesis of 5‐Bromo/Iodo Cyclopentenones

An efficient synthetic approach for the synthesis of 5‐bromo/iodo‐cyclopentenones containing a C–X (Br, I) stereocenter that relies on gold(I)‐catalyzed cycloisomerization–electrophilic halogenation sequence of 1,3‐enyne esters with N‐bromosuccinimide (NBS) or N‐iodosuccinimide (NIS) is described. This tandem transformation exhibited a broad substrate scope and excellent functional group compatibility, providing a novel protocol for rapid assembly 5‐bromo/iodo‐cyclopentenones in good to excellent yields under mild reaction conditions. An efficient and regioselective protocol for the construction of 5‐bromo/iodo cyclopentenones from gold(I)‐catalyzed tandem cycloisomerization/electrophilic halogenation of 1,3‐enyne esters with NXS in a one‐pot two‐step operation has been developed. The synthetic utility was further demonstrated by the scale‐up preparation of one example followed by its conversion to the corresponding α‐substituted cyclopentenones with a diverse array of functionalities.