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Show (E - CQ;Et) 3 libst 1 R i n in Ma Et ,Pi fBi no 5ft . Sn IB ¦ TBOMS ATOM EFFICIENT PREPARATION T.nti.ii.«tn,i.i*,«iHiifc. OF LACTONES FROM CARBON DIOXIDE E Marc V. Farnworth (Janis Louie) Department of Chemistry, University of Utah, Salt Lake City, UT 84112-0850 Carbon dioxide is an attractive, nontoxic Cl feedstock. However, despite extreme availability, only limited success has been achieved with the use of transition metal activatorsl and harsh reaction conditions.2 Recently, we have discovered a mild and efficient method for the catalytic formation of pyrones under atmospheric pressures of CO2. Specifically, catalytic amounts of Ni(COD)2 and IPr ligand (IPr = l,3-bis-(2,6-diiso-propylphenyl)-irnidazol-2-ylidene) mediated the 12+2+2] cydoaddi-tion of diynes under only 1 atmo-spheric pressures of CO2 to af-ford 2-pyrones. A variety of diynes were subjected to a nickel-cata-lyzed oxidative coupling reaction which resulted in good to excel-lent yields of the corresponding pyrones (Table 1). From the results obtained, we conclude that it is possible to cre-ate pyrones in good yields from the reaction of catalytic Ni(0) and CO2 under mild reaction condi-tions. Efforts to expand the sub-strate scope and understand the mechanism of activation are cur-rently underway. References (1) Takamoto, M.; Mori, M.; J. Am. Chem. Soc. 2001, 123, 2895 and references therein. (2) (a) Paddock, R. L; Nguyen, S. T. J. Am. Chem. Soc. 2001, 123, 11498. (b) Cheng, M.; Lobkovsky, E.B.; Coates, G. W. J. Am. Chem. Soc. 1998,12011018. cirbti dhiidi' m tfl0, ii\ TUS |
