Water‐Promoted Dehydrative Tsuji–Trost Reaction of Non‐Derivatized Allylic Alcohols with Sulfinic Acids

A mild, green and extra activator‐free synthesis of allylic sulfones from non‐derivatized allylic alcohols and sulfinic acids was developed and only the easily‐available Pd(PPh 3 ) 4 was used as the catalyst. This new method could be easily scaled up to gram scale, affording the target allylic sulfones in a nearly quantitative yield with water as the sole by‐product. Mechanism studies both by various NMR techniques and by theoretical calculations suggested two reaction pathways may be involved in the reaction, which are dependent on the reaction media, that is, an eight‐membered ring binding species may be formed in aqueous media between allylic alcohol, sulfinic acid and water, while a six‐membered ring binding species may be formed in common aprotic organic solvent between allylic alcohol and sulfinic acid. Both binding species may be accounted for the efficient activation of allylic alcohols via hydrogen bonding.