Nickel-catalyzed skeletal transformation of tropone derivatives via C–C bond activation: catalyst-controlled access to diverse ring systems |
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Authors: | Takuya Kodama Kanako Saito Mamoru Tobisu |
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Institution: | Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita Osaka 565-0871 Japan.; Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Suita Osaka 565-0871 Japan, |
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Abstract: | We report herein on nickel-catalyzed carbon–carbon bond cleavage reactions of 2,4,6-cycloheptatrien-1-one (tropone) derivatives. When a Ni/N-heterocyclic carbene catalyst is used, decarbonylation proceeds with the formation of a benzene ring, while the use of bidentate ligands in conjunction with an alcohol additive results in a two-carbon ring contraction with the generation of cyclopentadiene derivatives. The latter reaction involves a nickel–ketene complex as an intermediate, which was characterized by X-ray crystallography. The choice of an appropriate ligand allows for selective synthesis of four different products via the cleavage of a seven-membered carbocyclic skeleton. Reaction mechanisms and ligand-controlled selectivity for both types of ring contraction reactions were also investigated computationally.We report on C–C bond cleavage reactions of tropone derivatives by nickel catalysis. A single tropone derivative can be diversified into four different products with different ring skeletons by the judicious choice of the ligand. |
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