Copper-promoted functionalization of organic molecules: structure, spectroscopy and mechanism
Professor Isaac Garcia-Bosch (Southern Methodist University, Department of Chemistry)
Host: Professor Kathy Franz
Wednesday, September 25, 2019 - 1:30pm to 3:00pm
Location: French Family Science Center 4233
Rosenthal, Janet

Link for Professor Garcia-Bosch

Abstract:  Our research lab takes inspiration from metalloenzymes to develop metal complexes able to catalyze organic transformations under environmentally benign conditions using cheap reagents such as Cu, and green oxidants such as O2 or H2O2 (Chem. Rev. 2019, 119, 2954.). In 2016, we reported a practical synthetic protocol to oxidize strong C-H bonds with H2O2 using catalytic amounts of Cu and commercially available ligands (Angew. Chem., Int. Ed. 2016, 55, 12873). A detailed mechanistic study revealed that the oxidations occurred via formation of non-selective Fenton oxidants (·OH and ·OOH radicals) that were generated in the LCuII/LCuIII redox cycle. In organic synthesis, an elegant way to overcome the selectivity issues associated with the formation of radicals is the use of directing groups. We have also studied the mechanism by which Cu promotes the intramolecular hydroxylation of sp2 and sp3 C-H bonds, which allow us to develop oxidation conditions that utilize cheap reagents and mild conditions and reach unprecedented yields (J. Org. Chem. 2017, 82, 7887; Inorg. Chem. 2019, 58, 7584). An alternative approach to avoid the formation of radical species in 3d metal-catalyzed organic synthesis is the use of redox-active ligands. We have recently reported that Cu complexes bearing bidentate redox-active ligands with tunable H-bonding groups catalyzed the aerobic oxidation of alcohols under mild conditions (J. Am. Chem. Soc., 2018, 140, 16625). We found that these Cu catalysts were able to donate e- and stabilize Cu-O2 intermediates via H-bonding interactions, and that the mechanism of alcohol oxidation was unprecedented for galactose-oxidase model systems.