Factors determining the course of reaction (i.e., usual coupling vs. abnormal cine-substitution) in the Stille coupling of trisubstituted iodoalkene and trans-vinylstannane were investigated. The palladium-catalyzed reaction with triphenylarsine
and lithium chloride in N-methylpyrrolidone gave the normal Stille coupling product in good yield and good
selectivity, while the use of N,N-diisopropylethylamine and cuprous iodide in toluene afforded the cine-substituted product exclusively. It is proposed that transmetalation between vinylpalladium
and vinylstannane species determines the course of reaction.
Key words
Stille reaction - cross-coupling - palladium - regioselectivity - alkenes