The C(sp3)–H bond oxygenation of a variety of cyclopropane containing hydrocarbons with hydrogen peroxide catalyzed by manganese complexes containing aminopyridine tetradentate ligands was carried out. Oxidations were performed in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and 2,2,2-trifluoroethanol (TFE) using different manganese catalysts and carboxylic acid co-ligands, where steric and electronic properties were systematically modified. Functionalization selectively occurs at the most activated C–H bonds that are ?- to cyclopropane, providing access to carboxylate or 2,2,2-trifluoroethanolate transfer products, with no competition, in favorable cases, from the generally dominant hydroxylation reaction. The formation of mixtures of unrearranged and rearranged esters (oxidation in HFIP in the presence of a carboxylic acid) and ethers (oxidation in TFE) with full control over diastereoselectivity was observed, confirming the involvement of delocalized cationic intermediates in these transformations. Despite such a complex mechanistic scenario, by fine-tuning of catalyst and carboxylic acid sterics and electronics and leveraging on the relative contribution of cationic pathways to the reaction mechanism, control over product chemoselectivity could be systematically achieved. Taken together, the results reported herein provide powerful catalytic tools to rationally manipulate ligand transfer pathways in C–H oxidations of cyclopropane containing hydrocarbons, delivering novel products in good yields and, in some cases, outstanding selectivities, expanding the available toolbox for the development of synthetically useful C–H functionalization procedures.
This work has been carried out by Prof. Massimo Bietti from Nanjing University, W. Suo and Prof. X. Guo from Università “Tor Vergata” and Dr. Marco Galeotti, Prof. Miquel Costas from the QBIS-Cat group of the Institute of Computational Chemistry and Catalysis of the University of Girona.
It has been recently published open access in Journal of the American Chemical Society:
M. Galeotti, M. Bietti* and M. Costas*.
“Catalyst and Medium Control over Rebound Pathways in Manganese-Catalyzed Methylenic C–H Bond Oxidation”
J. Am. Chem. Soc., 2024, ASAP
DOI: 10.1021/jacs.3c11555
Girona, April 4th, 2024
For more info: ges.iqcc@udg.edu