ORGN 153 |
| Radical cyclization of bromoacetates and brominated acrylates in the presence of tributyltin hydride (nBu3SnH) and AIBN (2,2'-azobisisobutyronitrile) yields predominantly an open-chain product and a small amount of lactone. Copper(I) complexes, namely bis[(hydrotris(1-pyrazolyl)borato)copper(I)] ([TpCu]2), bis[(hydrotris (3,5-dimethyl-1-pyrazolyl)borato)copper(I)] ([TpMeCu]2), hydrotris(3,5-dimethyl-1-pyrazolyl)borato(acetonitrile)copper(I) (TpMeCu(CH3CN)) and hydrotris(3,5-bis(trifluoromethyl)-1-pyrazolyl)borato(acetonitrile)copper(I) (TpCF3Cu(CH3CN)) have been synthesized by the reaction of CuIBr with the corresponding ligand in methylene chloride. The synthesized complexes were utilized in free radical cyclization of bromoacetates and brominated acrylates with the aim of investigating the effect of C=C double bond coordination to the copper (I) center on the yield and selectivity of the cyclization reaction. The presence of a copper (I) complex in the reaction system increased the percent conversion of bromoacetates and brominated acrylates. Radical cyclization of bromoacetates in the presence of copper (I) complexes with electron-donating pyrazole ligands showed a three-fold increase in the percent yield of lactones. On the other hand, copper (I) complexes with electron-withdrawing pyrazole ligands favored the formation of lactones for brominated acrylates. |
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Process R&D, Physical Organic Chemistry, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Sunday, March 25, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Organic Chemistry |