2009 Volume 82 Issue 3 Pages 393-400
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.
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