Carbanion-Accelerated Claisen Rearrangements. 6. Preparative and Stereochemical Studies with Sulfonyl-Stabilized Anions

The aliphatic Claisen rearrangement is markedly accelerated by an arylsulfonylmethide substituent at position 2. The generality of this anion variant has been extensively examined (31 allyl vinyl ethers) with regard to substitution, stereochemistry, and anion-stabilizing groups. The reactions generally proceed in good yield and with high regio- and stereoselectivities. The regiochemical course of the reaction is independent of the structure of the anionic precursor (α, β- or β, γ-unsaturated). The anionic rearrangement is highly diastereoselective producing either syn or anti products with 90-96% de. Vicinal quaternary centers are constructed easily. Other sulfur-based, anion-stabilizing groups were found to be inferior (sulfide, sulfoxide, and sulfilimine).