Activation of Olefins with Polarity Inversion and Its Synthetic Application

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The reactions which introduce functionalities to carbon-carbon unsaturated bonds have been widely used for organic syntheses as useful methods for the construction of organic molecules. As one methodology for such transformations, there have been developed a number of reactions using a transition metal catalyst, but in many cases the late transition metal catalysts have been employed. The main object of the present studies is to develop new catalytic reactions using the characteristics of early transition metal ate complexes. Terminal alkenes undergo silylation by the reaction with chlorosilanes in the presence of a Grignard reagent employing a catalytic amount of zirconocene dichloride to give alkenyl and/or allylsilanes as the products. The reaction also proceeds under mild conditions when silyl sulfides, silyl selenides, and silyl tellurides are used in place of chlorosilanes. As an extension of this reaction, a new transformation of aryl alkenes via regioselective alkylation using alkyl tosylates, sulfates and bromides having a β-hydrogen has been developed using a zirconocene complex as the catalyst. When the reaction was carried out using tianocene catalyst, double alkylation of aryl alkenes proceeds in THF to give 1,2-vic-dialkylated products. On the other hand, Heck type transformation of aryl alkenes with alkyl bromides proceeds in ether under similar conditions. Carbosilylation and double silylation of 1,3-butadienes with chlorosilanes and/or alkyl bromides were also developed. This reaction proceeds under mild conditions by the use of titanocene catalyst in the presence of ^<11>BuMgCl giving rise to 1,4-carbosilylated or 1,4-double silylated 2-butenes. Aryl substituted alkenes also afford 1,2-carbosilylated or 1,2-double silylated products under similar conditions.