Direct Synthesis of γ-Keto Sulfones from Allylic Alcohols: One-Pot Palladium(II)-Catalyzed Generation of Enones Followed by Water-Mediated 1,4-Addition of Organosulfinates

Allylic alcohols were exploited as synthetic precursors of -keto sulfones. The reaction involved the one-pot generation of ,-enones in situ from the allylic alcohols by using a Pd-II-dioxygen catalytic system and subsequent sulfa-Michael addition in the presence of water. Importantly, water was identified as a sustainable substitute for a toxic copper salt to promote organosulfonyl addition. Diverse examples of aromatic and aliphatic -keto sulfones were prepared. Specially, Ar-X (X = Br, Cl) bonds were tolerated, which indicated a chemoselective catalytic system for the preparation of halogen-bearing -keto sulfones. This one-pot method does not require an acid, a base, or isolation of any intermediate. Control experiments indicated that the active catalyst of the first step also promoted the subsequent C-S bond-formation reaction. Water was found to accelerate the reaction rate and to be involved in the protonolysis of the sigma-alkylpalladium complex, as corroborated by deuterium incorporation.