ORGN 607 |
| We report herein the high temperature, stereoselective coupling of dicobalthexacarbonyl-propargyl cations, occurring spontaneously within the temperature range of 40-147°C. Under these conditions, d,l- and meso-(3,4-diphenyl-1,5-hexadiyne)bis(dicobalthexacarbonyl) complexes were formed in good yields (84-93%), and with an excellent d,l-diastereoselectivity (de 80-88%). Elevated temperatures provided for a significant acceleration, bringing the reaction to completion in 1min at 147°C, as opposed to 11h at 20°C. Mechanistic studies revealed a heavy incorporation of 13CO molecules (up to 8) into the metal cores, indicating a one-electron, cluster-to-cluster oxidation along the reaction coordinate. One- and two-step experimental procedures were developed with the former exploiting a triflic anhydride and bypassing the propargyl cation isolation step. Impact of the aromatic substitution (4-, 3,4-, 3,4,5-) upon yield, diastereoselectivity, and kinetics will also be presented. |
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Materials, Devices and Switches, Metal-Mediated Reactions, Asymmetric Reactions, Total Synthesis, Biologically-Related Molecules and Processes
7:00 PM-9:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- La Louisiane, Blrm. C, Poster
Division of Organic Chemistry |