Unprecedented cobalt-catalyzed isomerization reactions to single skipped 2,4,7-trienes applied in the synthesis of urushiol

Article abstract of DOI:10.1002/asia.201402323

The cobalt-catalyzed isomerization of 1,3-dienes to 2Z,4E-dienes was realized for the very challenging substrates with an additional double bond in the side chain. An isomerization to the conjugated 3,5,7-triene derivative was not observed, which is in stark contrast to observations with many other isomerization catalysts. Accordingly, the synthesis of the natural product urushiol, which has a sensitive 2Z,4E,7Z-triene subunit in the side chain, was investigated. The O-protected urushiol derivative was generated selectively without isomerization to the conjugated 3,5,7-triene or Z/E-isomerization of the double bond at position 7.