One-Pot, Metal-Free Synthesis of Allyl Sulfones in Water

A one-pot dehydration cross-coupling reaction between allyl alcohols and sodium sulfinates that provides allyl sulfones in good to excellent yields is presented. Its broad substrate scope includes symmetrical and asymmetrical alpha,alpha-diaryl- and alpha-aryl-substituted allylic alcohols and aryl and alkyl sodium sulfinates. For asymmetrical allylic substrates, the E isomer predominates with examples of excellent stereoselectivity. Control experiments provide the basis for a proposed radical-mediated mechanism. The metal-free procedure applies cheap and commercially available tetrabutylammonium tribromide as the catalyst and H2O as the solvent. Notable features of this simple, efficient, weakly toxic, and environmentally benign strategy include mild and convenient operating conditions and readily accessible starting materials.