| Research Abstract |
(1) Cross-coupling Reaction of Alkyl Halides with Organozinc and Grignard Reagents Using 1,3,8,10-Tetraenes as Additives
An efficient method for cross-coupling of organozinc reagents with alkyl bromides and tosylate has been established by the use of Ni(acac)_2 as the catalyst. The use of 1,3,8,10-tetraenes as the additive is essential to attain excellent yields of coupling products. This reaction proceeds efficiently under mild conditions using primary and secondary alkyl- and arylzinc reagents. Addition of a tetraene also improved the yield of cross-coupling of an alkyl fluoride with a Grignard reagent using Ni catalyst.
(2) Cu-Catalyzed Cross-Coupling Reaction of Alkyl-X with Grignard Reagents in the Presence of Alkynes as Additives
Cu-Catalyzed cross-coupling reaction of n-alkyl chlorides, fluorides, and mesylates with Grignard reagents proceeded efficiently under THF reflux conditions in the presence of 1-phenylpropyne. Addition of 1-phenylpropyne dramatically improved the yields.
(3)
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Ni-Catalyzed Alkylative Dimerization of Vinyl Grignard Reagents Using Alkyl Fluorides
Alkyl halides underwent unique cross-coupling reaction with vinyl Grignard reagent in the presence of Ni catalyst to give 2-alkyl-3-butenyl Grignard reagent in high yields. Alkyl fluorides react as the most suitable alkylating reagent in comparison to the corresponding chlorides, bromides, and iodides.
(4) Palladium-Catalyzed Dimerization Disilylation of 1,3-Butadiene with Chlorosilane
1,3-Buatdiene reacted with chlorosilanes and Grignard reagents at 20℃ in the presence of a catalytic amount of Pd(acac)_2 to give disilylated dimers 2 regioselectively, which have two silyl groups (R_3Si) at the 3- and 8-positions of a 1,6-octadiene skeleton. When phenyl or allyl substituted chlorosilanes were used, coupling product was obtained stereo- as well as regioselectively giving rise to only E-olefins. It is proposed that Pd-ate complexes play important roles in both C-Si bond forming process.
(5) Nickel-Catalyzed Novel Coupling Reaction of Allyl Ethers with Chlorosilanes, Alkyl Tosylates, or Alkyl Halides Promoted by Vinyl Grignard Reagent Leading to Allysilanes or Alkenes
A new method for carbon-silicon or carbon-carbon bond forming reaction between allyl ethers and chlorosilanes, alkyl tosylates, or alkyl halides giving rise to allylsilanes or alkenes has been developed. This reaction proceeds efficiently at ambient temperature by the combined use of nickel catalysts and vinyl Grignard reagent. A possible reaction pathway involving the formation of allyl Grignard reagents via transmetallation of π-allylnickel complexes with vinyl Grignard reagent and subsequent trapping of thus formed allyl Grignard reagents with electrophiles is proposed.
(6) Reaction Pathways of Zirconocene-Catalyzed Silylation of Alkenes with Chlorosilanes
Reaction pathways as well as stereochemistries and stoichiometries of zirconocene-catalyzed silylation of olefins with chlorosilanes in the presence of ^nBuMgCl were studied and discussed in detail. Rate determining steps were examined by kinetic studies and labeling experiments.
(7) Zr-Catalyzed Coupling Reaction of Alkyl Halides, Tosylates, and Sulfates with β-Phenethyl Grignard Reagents via Styrene-Zirconate Intermediates
β-Phenethylmagnesium chlorides react with alkyl halides, tosylates, and sulfates in the presence of a catalytic amount of Cp_2ZrCl_2 to afford 2-arylalkanes via alkylation of styrene-zirconate intermediates at the benzylic position. Competitive reaction using mixtures of alkyl halides (Alkyl-X; X =F, Cl, Br) showed that the reactivities of the halides increase in the order of Alkyl-Cl < Alkyl-F < Alkyl-Br with the relative rates of 1:19:428.
(8) Ni-Catalyzed Regioselective Three Component Coupling Reaction of Alkyl-X, Butadienes, and Ar-M
A new method for regioselective three component cross-coupling reaction of alkyl halides, 1,3-butadienes, and aryl Grignard reagents has been developed by the use of a nickel catalyst. Alkyl chlorides, bromides, and iodides can be used as suitable alkylating reagents. The reaction also proceeds when arylzinc halides are used instead of Grignard reagents. Less
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