The first examples of metal-catalyzed extended Pummerer reactions through the activation of sulfoxides are described. The copper-catalyzed reactions of ketene dithioacetal monoxides with alkynyl sulfides and ynamides provided a wide variety of γ,γ-disulfanyl-β,γ-unsaturated carbonyl compounds with an accompanying oxygen rearrangement. The products can be easily converted into 1,4-dicarbonyl compounds and substituted heteroaromatics. DFT calculations and mechanistic experiments revealed a new interesting stepwise addition/oxygen rearrangement mechanism.

A method for the synthesis of 2-aryl-1,3-alkadienes has been developed. Treatment of aryl bromides with 3,4-alkadien-1-ols in the presence of a palladium catalyst results in 1-methylene-2-propenyl group transfer to aryl bromides. Taking advantage of palladium-mediated retro-allylation as an sp3C–sp3C bond cleavage reaction, one can regard 3,4-alkadien-1-ols as 1-methylene-2-propenyl metal equivalents that are easy to prepare and are not sensitive to air and moisture. In the event that the Diels–Alder dimerization of the product during the 1-methylene-2-propenylation reaction is problematic, addition of N-methylpyrrole to the reaction mixture can efficiently suppress the dimerization. The reactions of aryl bromides with 2-substituted 3,4-alkadien-1-ols yield the corresponding (E)-2-aryl-1,3-alkadienes stereoselectively.

Atom-transfer radical addition of α-iodo esters to 1-alkynyl sulfides is described. The products, 2-alkoxycarbonylmethyl-1-iodo-1-alkenyl sulfides, can be converted into γ-keto esters.

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Alkenes Q 0083Palladium-Catalyzed 1-Methylene-2-propenylation Reactions of Aryl Bromides with 3,4-Alkadien-1-ols via Carbon-Carbon Bond Cleavage for the Synthesis of 2-Aryl-1,3-butadiene Derivatives. -(IMOTO, J.; HAYASHI, S.; HIRANO, K.; YORIMITSU*, H.; OSHIMA, K.; Bull. Chem. Soc. Jpn. 82 (2009) 3, 393-400; Dep. Mater. Chem., Grad. Sch. Eng., Kyoto Univ., Nishikyo, Kyoto 615, Japan; Eng.) -D. Singer 30-064