Finally, another and related stereospecific approach to 1, 4-and 1, 5-dienes was developed based on the addition of copper reagents to 2, 4-pentadienoic ester derivatives. Reaction of vinylcopper and methallylcopper at-78" with methyl trans-2, 4-pentadienoate followed by quenching at-78" with methanol and isolation as outlined above afforded in good yield the trans-diene esters lo4 and 11, 4 respectively [ir max (neat) for 10, 1750, 1640, 990, 910, ...
