Copper catalyzed atom transfer radical addition (ATRA) reactions are fundamental ways to make carbon-carbon bonds from alkenes and alkyl halides. The reaction involves the generation of a radical, identified as the activation step in the catalytic cycle, and has a rate constant of activation, kact. Copper catalyzed ATRA reaction rate constants are often extremely fast and cannot be measured used simple spectroscopic techniques. Therefore a new series of copper(I) complexes containing the tetradentate ligand tris-(2-aminoethyl)amine (TREN) was synthesized and evaluated for ATRA catalysis. Variation of the steric and electronic environment around copper was achieved through systematic modification of the ligand, TREN-R (R = H, Me, Cl, CF3). Kinetic studies were conducted using UV-vis spectroscopy with an alkyl halide and radical trapping agent (2, 2, 6, 6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO). The kact values for primary and secondary alkyl bromides and alkyl chlorides have been determined using the (TREN-R) copper(I) catalysts. The kact values for the (TREN-R) copper(I) catalysts are 1,000-1,000,000 times slower when compared to kact values for copper catalysts containing tris[2- (dimethylamino)ethyl]amine (Me6TREN) or tris(2-pyridylmethyl)amine (TPMA) ligands. Alkyl bromides react 1000 times faster than alkyl chlorides (CBr4 vs CCl4). Secondary alkyl chlorides react 100 times slower than CCl4. The electron donating effects of the methyl group also increase the rate constant while the electron-withdrawing effects of Cl and CF3 decrease the rate constant for all alkyl halides screened.

Measurement of the rate of activation constants (k<sub>act</sub>) for (TREN-R) copper catalysts utilized in atom transfer radical addition reactions

247th National Meeting (2014)

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Measurement of the rate of activation constants (kact) for (TREN-R) copper catalysts utilized in atom transfer radical addition reactions

Measurement of the rate of activation constants (k_act) for (TREN-R) copper catalysts utilized in atom transfer radical addition reactions