Palladium-catalysed reactions conjugated dienes

Palladium(0)-catalysed coupling of non-conjugated dienes, aryl iodides and stabilized carbon nucleophiles has been developed468. An incredibly high yield (86%) of pentacycle 343 has been obtained from a Pd(0)-catalysed zipper reaction of acetylenic pentaene 342. The reaction is triggered off by a Pd-catalysed cyclization of acetylenic bond and the first olefinic bond469. 

Palladium catalysed coupling reactions are also effectively applied to vinyl derivatives and thus constitute a particularly convenient access to conjugated diene systems [23bj. 

An interesting 1,4-elimination reaction occurs upon treatment of allylic acetates with catalytic [Pd(Ph3P)4] together with propargylzinc bromide to act as a base (Scheme 43). What is important in this reaction is the observed regioselectivity, which is in contrast to that of previously reported palladium-catalysed elimination reactions giving conjugated dienes. 

A simple method for the synthesis of terminal conjugated dienes is based on the palladium-catalysed elimination of acetic acid or phenol from the readily available allylic acetates or phenyl ethers [equation (18)]. The reaction proceeds... 

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