Fused and Spirocyclic Sulfones for Medicinal Chemistry via [3 + 2] Cycloaddition of Thiocarbonyl Ylide

The [3 + 2] cycloaddition between thiocarbonyl ylide CH2S(+)–CH2(−) and electron-deficient cyclic alkenes provides bicyclic sulfides. The reaction efficiently works on milligram, gram, and even multigram quantities. Standard modifications of the obtained products give fused and spirocyclic sulfones for medicinal chemistry.