Direct Synthesis of γ-Keto Sulfones via Bronsted Acid-Promoted Tandem Sulfonylation of Propargylic Esters with RSO ₂ H

A novel and general strategy has been developed for the synthesis of γ-keto sulfones via Bro̷nsted-acid-promoted tandem sulfonylation of propargylic esters with RSO₂H under metal-free and oxidant-free conditions. The novel transformation proceeds through α,β-unsaturated ketone intermediates as the key intermediate, which then undergoes thia-Michael addition with sulfinic acids to afford the target γ-keto sulfones in moderate to excellent yields. The key merits of this approach include operational simplicity, the avoidance of metals and oxidants, and good functional group tolerance.