Synthesis of Enhanced, Isolable Disulfanium Salts and their Application to Thiiranium-Promoted Polyene Cyclizations

Although electrophile-promoted polyene cyclizations have long been a mainstay transformation for the rapid and stereocontrolled preparation of varied natural products and designed molecules, efforts to effect sulfur-promoted variants have arguably lagged behind other counterparts. This state of affairs is particularly true with alkyl sulfide-based electrophiles, even in racemic variants. Herein, building on previously reported discoveries, is described a distinct and modular method to prepare a range of isolable alkyl and aryl disulfanium salts that can affect thiiranium-based polyene cyclizations in moderate to good yields. In most of the substrates probed, these reagents provide superior yields to previously reported alternatives. In addition, initial efforts to develop an asymmetric variant of the process through the use of chiral versions of these reagents are discussed.