Generation and Reaction of Multi-functionalized Transition Metal Reactive Species

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In this research, generation and reaction of novel multi-functional reactive species are studied extensively. It is expected that electiophilic activation of alkynes with W(CO)_5(L) followed by attack of nucleophiles on them would give novel multi-functional reactive species, which are expected to behave both as a 1,3-dipole and as a carbene complex. Based on this concept, several unique and synthetically useful reactions have been developed.In the first place, generation and reaction of novel tungsten-containing carbonyl and azomethine ylides were developed. Treatment of ο-ethynylphenyl ketones or N-(ο-alkynylphenyl)imine derivatives with W(CO)_5(thf) generated the tungsten-containing 1,3-dipoles by the endo-mode of attack of the carbonyl oxygen or imino nitrogen onto the electrophilically activated alkyne moiety. The [3+2]-cycloaddition of the generated ylides with electron-rich alkenes followed by insertion of the resulting tungsten carbene moiety into a neighboring C-H bond or 1,2- … More alkyl-migration realized the construction of complex cyclic carbon frameworks in a single step. This reaction proceeded even with a catalytic amount of W(CO)_5(thf). Thus, novel multi-functional reactive species are successfully generated and react with alkenes to give synthetically useful compounds in a single operation.We next examined the possibility of realizing geminal carbo-functionalization of alkynes. Treatment of ω-acetylenic dienol silyl ethers with W(CO)_6 under photoirradiation gave bicyclo[3.3.0]octane derivatives, which were produced by addition of the silyl enol ether to the electrophilically activated alkynes to give alkenylmetallic intermediates. This further reacted with α,β-unsaturated oxonium moiety at the position β to the metal to give carbene complex intermediates, which underwent typical carbene reactions to give the products. This method constitutes a catalytic method for the geminal carbo-functionalization of alkynes. ReCl(CO)_5 showed paiticularly high activity for this reaction ; even 0.5〜3.0 mol% of ReCl(CO)_5 were sufficient to promote the reaction efficiently. Less