Alkyldisulfanium Salts: Isolable, Electrophilic Sulfur Reagents Competent for Polyene Cyclizations

Tools that can effect electrophilic
sulfur-promoted cation−π
cyclizations are generally lacking, especially using alkylsulfide-based
reagents. Herein we report that combining three different 1,2-dithioethers
with Cl2 and SbCl5 generates isolable alkyldisulfanium
salts that can effect such reactions. These new reagents can install
−SMe, −SEt, and −SCH2CH2CF3 in modest, moderate, or good yield on diverse frameworks,
including polyenes that terminate with electron-deficient groups.
We also show that reagents such as dimethyl­(methylthio)­sulfonium
tetrafluoro­borate (DMTSF) can accomplish similar chemistry.