ORGN 148 |
| Jin kyun Lee1, A. B. Holmes2, Edward J. Bush3, and Ian McConvey3. (1) Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom, (2) Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom, (3) Process Research and Development, Astra Zeneca, Macclesfield, Cheshire, SK10 4LS, United Kingdom |
| As an environmentally benign solvent, supercritical carbon dioxide has attracted much interest. However, due to its non-polar properties chemical reactions in scCO2 show different reactivity from those in polar solvents. This poster describes the investigation of alternative ligands for successful Heck reactions in scCO2. A number of phosphines and phosphites with varying electronic and steric effects were investigated in a model Heck reaction in heptane and the results were used to optimize reactions in scCO2 as solvent. Based on the observation that an electron withdrawing group on the phosphine resulted in a large increase in reactivity in heptane, the more electron withdrawing phosphites were investigated and shown to give much improved yields. With a biphenyl based phosphite excellent conversion was observed in heptane and scCO2. One possible explanation for these results is that phosphites seem to stabilize active Pd species in the catalytic cycle, and therefore increase its life time. |
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Asymmetric Reactions and Syntheses, Metal-Mediated Reactions, Materials, Molecular Recognition
8:00 PM-10:00 PM, Sunday, August 22, 2004 Pennsylvania Convention Center -- Hall D, Poster
Division of Organic Chemistry |