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Show Marc Farmvrith Carbon Dioxide as a Carbon Source M. hmmmfKt J* Lfluk r ni: i-nu^it^ University *f Ltah Carbon dioxide is an attractive, nontoxic C1 feedstock. However, despite, extreme availability, onJy lira ited success has been achieved with the use of transition metal activators (lief. I) and harsh reaction conditions (Ref. 2). Recently, \ve have discovered a mild and efficient method for the catalytic formation of py rones under atoitispkeric pressures of CO:. Specifically, catalytic amounts of Ni(CQD)2 andlPr ligand (TPr = 1>bi&<i6-diisopropylphenyl)-imidazDl-2-ylidene) mediated, the [2+2-1-2] cycloadtlition of diynes under onJy 1 atmospheric pressures of CO] to afford 2-pyrones. A variety of diynes were subjected to a nickel -catalyzed oxidative coupling reaction which resulted in good to excellent yields of the corresponding pyrones. From the results obtained, we conclude that it is possible 10 crtfltt pyranes in good yields from the reaction of catalytic Ni(0) and COz under mild reaction conditions. Efforts to expand the substrate scope and understand the mechanism of activation are currently underway. : 1) Takamoto, M.; Mori, M.; J. Am. Chem. Soc. 2001, 123, 2395 and references therein. 2) Paddock, E_ L.; Nguyen, S. T. J. Am. Chem. Soc. 2001, 125, 11498. 34 |