Palladium ring compound, reaction with acetylene

The reaction of methylenecyclopropanes with transition metal complexes is well known to promote a catalytic a-ir cycloaddition reaction with unsaturated compounds, in which a trimethylenemethane complex might exist71-76. Recently, much interest has been focused on the interaction of strained silicon-carbon bonds with transition metal complexes. In particular, the reaction of siliranes with acetylene in the presence of transition metal catalysts was extensively investigated by Seyferth s and Ishikawa s groups77-79. In the course of our studies on alkylidenesilirane, we found that palladium catalyzed reaction of Z-79 and E-79 with unsaturated compounds displayed ring expansion reaction modes that depend on the (Z) and (E) regiochemistry of 79 as well as the... 

This catalyst has been optimized over the years [80-82], and the best support was found to be acetylene black due to its highly olefinic nature. Palladium was initially chosen as the main catalytic metal, due to its high activity and low cost. This was improved by promoting it with a small amount of platinum however, this catalyst was too active and yielded unwanted side products via reactions such as ring hydrogenation. The selectivity of this catalyst was then corrected by the addition of iron oxide, which impeded the undesired reactions. Iron has also been proven to be a promoter for the hydrogenation of aliphatic nitro compounds [83]... 

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