(1) Schafer, L. L., Bexrud, J. A., Li, C., Organometallics 2007, 26, 6366.

1. Asymmetric Hydroamination of Aminoallenes Catalyzed by Metal Complexes with Electron-Withdrawing Sulfonamide Ligands Johnson Laboratory - Harvey Mudd College Hydroamination, the addition of an N-H bond across a C-C double bond, can be catalyzed by metal complexes with a variety of ligands. It was predicted that at lower temperatures, the stereoselectivity would improve. If the two enantiomers have the same energy but their transition states have different energies, the reaction favors the product with the lower energy transition state. At higher temperatures, energy is sufficient to achieve either transition state, so selectivity is decreased. It was also predicted that the most electron-withdrawing sulfonamides would be the most reactive and that these reactions would be the most stereoselective. The expected trends were not observed for the Titanium complexes. Reactions using Tantalum complexes were more stereoselective than those with Titanium complexes. Stereoselectivity improved at lower temperatures, but did not increase for more electron-withdrawing ligands. Electron-withdrawing ligands have been shown to increase reactivity1, and were predicted to improve stereoselectivity. This project focused specifically on sulfonamide ligands, which have electron-withdrawing properties. The sulfonyl group is highly electronegative and withdraws electrons from the nitrogen, which then becomes a poor electron donor to the metal center.2 Hydroamination was performed using Ti(NMe2)4 and Ta(NMe2)5 at 125 °C and 135 °C using each of the six sulfonamide ligands: (1) Schafer, L. L., Bexrud, J. A., Li, C., Organometallics 2007, 26, 6366. (2) Walsh, P. J., Pritchett, S., Woodmansee, D. H., Gantzel, P., J. Am. Chem. Soc.1998,120, 6423.