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

• Published in: European journal of organic chemistry 2016-07, Vol.2016 (21), p.3575-3583
• Main Authors: Vellakkaran, Mari, Andappan, Murugaiah M. S., Nagaiah, Kommu, Nanubolu, Jagadeesh Babu
• Format: Article
• Language: English
• Subjects: Allylic compounds; Enones; Oxygen; Palladium; Sulfur
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201600494

Allylic alcohols were exploited as synthetic precursors of γ‐keto sulfones. The reaction involved the one‐pot generation of α,β‐enones in situ from the allylic alcohols by using a PdII–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 γ‐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 γ‐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 σ‐alkylpalladium complex, as corroborated by deuterium incorporation. Allylic alcohols are exploited as synthetic precursors of γ‐keto sulfones. The reaction involves the one‐pot generation of α,β‐enones in situ from the allylic alcohols by using a PdII–dioxygen catalytic system and subsequent sulfa‐Michael addition in the presence of water.