Development of New Catalytic Reactions Involving Silylmetalation as a Key Step

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The aim of this project was to develop new catalytic reactions involving silylmetalation as a key step. I found the following new reactions.1.The reaction of terminal acetylenes with Me_3SiI (1) and organozinc reagents in the presence of Pd (PPh_3)_4 results in addition of the trimethylsilyl group of 1 and an alkyl group of the organozinc reagent to the acetylenes. In all cases the trimethylsilyl group adds to the terminal carbon of the acetylenes. Both aromatic and aliphatic terminal acetylenes undergo the coupling reaction with high regio- and stereoselectivities. The yield and stereoselectivity are relatively sensitive to the nature of the organozinc reagent used. The reaction of phenylacetylene using Bu_2Zn gives the corresponding coupling product in high yield with high stereoselectivity (>98%). In contrast, the use of BuZnI results in 92% stereoselectivity. The stereoselectivity for the reaction using (Me_3SiCH_2)_2Zn is lower than those for Me_2Zn, Et_2Zn, and Bu_2Zn.2.The palladium-catalyzed reaction of trimethylgermyl cyanide (Me_3GeCN,2) with terminal acetylenes is studied in detail with particular emphasis focused on functional group compatibility as well as the factor affecting stereoselectivity. The reaction of 2 with terminal aromatic acetylenes in the presence of PdCl_2 results in the addition of 2 to the carbon-carbon triple bonds with high regioselectivity leading to beta-cyano vinylgermanes in high yields. The stereoselectivity depends on the electronic nature of the substituents on the aromatic ring. The reaction of terminal aliphatic acetylenes also afford the adduct with high regio-and stereoselectivity.