Telomers stereoselectivities

The reaction of hydrosilanes with butadiene is different from other reactions. Different products are obtained depending on the structurelof the hydrosilanes and the reaction conditions. Trimethylsiiane and other trialkylsilanes react to give the I 2 adduct, namely the l-trialkylsilyl-2,6-octadiene 74, in high yields[67-69]. Unlike other telomers which have the 2,7-octadienyl chain, the 2,6-octadienyl chain is formed by hydrosilylation. On the other hand, the 1 I adduct 75 (l-trichlorosilyl-2-butene)is formed selectively with trichlorosilane, which is more reactive than trialkylsilanes[69]. The Reaction gives the Z form stereoselectively[70]. A mixture of the I 1 and I 2 adducts (83.5 and 5.2%) is... 

Stereospecificity of this reaction reaches 15 1 for telomer T3. Telomer T3 is a crystalline product, this allowed the authors to use X-ray diffraction analysis for studying stereochemistry. Stereoselectivity observed in the formation of T3 shows that both addition step and the step of halogen transfer to the growing radical proceed stereoselectively in this case. 

Amine telomers are obtained from butadiene and secondary amines with nickel or palladium catalysts3. Highly regioselective (end on) and stereoselective E telomerization of butadiene and diethylamine to form ( )-A .A-diethyI-2,7-octadienamine (1) is achieved if the reaction is catalyzed by paIIadium(II) acetate, triphenylphosphane and triethylaluminum with an optimum Pd/P/Al ratio of 1 1 2X 3. While increasing the amount of triethylaluminum favors a high E/Z ratio, higher diene concentration leads to lower EiZ ratios and formation of higher telomers (C16). 

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