Transition-Metal-Free Reduction of -Keto Thioesters with Hydrosilanes at Room Temperature: Divergent Synthesis through Reagent-Controlled Chemoselectivities

The combination of hydrosilanes with a BrOnsted or Lewis acid as a promoter can be used for the reagent-controlled chemoselective reduction at room temperature of conjugated C=C bond, enone moiety, or the carbonyl of (,-unsaturated) -keto thioesters, providing facile access to ,-saturated -keto thioesters, -hydroxy thioesters, or silyl ethers. The reaction pathway and the chemoselectivity can be fine-tuned through the judicious choice of the hydrosilane or the reaction conditions. The reactions tolerate a wide range of functional groups including labile thioesters and the products are generally obtained in moderate to excellent yields. Unsymmetrical thioethers can also be synthesized using PMHS and catalytic B(C6F5)(3) via reductive deoxygenation of both the carbonyl groups. The applicability has been highlighted by the amine-mediated and coupling reagent-free syntheses of saturated -keto amides from ,-unsaturated -hydroxy thioesters and ,-saturated -keto thioesters.