Sulfonium Ylides by (3+2) Cycloaddition of Arynes with Vinyl Sulfides: Stereoselective Synthesis of Highly Substituted Alkenes

The reaction of in situ generated arynes with vinyl sulfides provides benzannulated sulfonium ylides in a (3+2) cycloaddition. Trapping of the intermediate ylides with electrophiles (proton transfer or a second aryne addition) and subsequent beta-elimination give rise to di-, tri-, or tetrasubstituted alkenes with high stereoselectivity. Experimental studies and DFT calculations provide insight into the mechanisms of these cascade reactions.