ORGN 552 |
| Studies of direct cyclopalladation reactions of oxazolines by our group recently revealed that the formation of endo-palladacycles is favored over exo-palladacycles. On the other hand, the preferential activation of aromatic, over aliphatic, C–H bonds in cyclometalation reactions is widely accepted. In order to determine which factor, endo-effect or carbon hybridization, is more important, we studied the direct cyclopalladation of (S)-2-tert-butyl-4-phenyl-2-oxazoline (1), where the endo-effect and carbon hybridzation are acting in opposite directions. We found that palladium acetate reacts with 1 in acetic acid to form two palladacycles: endo-sp3 (2) and exo-sp2 (3) in a ratio of 13:1. The endo-effect appears to be more important than the carbon hybridization in determining the regioselectivity of the reaction. The effects of palladation reagent, solvent, and temperature on the regioselectivity of this reaction will be disscussed.
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Heterocycles, Aromatics, Metal-Mediated Reactions and Syntheses, Materials, Devices, and Switches
8:00 PM-10:00 PM, Wednesday, 29 March 2006 Georgia World Congress Center -- Ex. Hall B4, Poster
Division of Organic Chemistry |
