The versatility of Acetamido-TEMPO in the chemical and electrochemical activated oxidation of alcohols

POLITANO, FABRIZIO; BRYDON, WILLIAM P.; SCHROEDER, CHELSEA M.; LEÓN SANDOVAL, ARTURO; LEADBEATER, NICHOLAS E.

Venecia

Taller; 14th Green Chemistry Postgraduate Summer School; 2022

Green Sciences for Sustainable Development Foundation

Oxoammonium salts (1) have been broadly used as oxidants in a variety of transformations ranging from simple alcohol oxidations to more complex reactions such as oxidative amidations and esterifications.[1] Altough its efficiency and ease to use, super-stoichiometric amounts of the salt are needed due to a comproportionation reaction between (1) and (3) to form two equivalents of (2). A more sustainable alternative is to employ its TEMPO-like radical precursor (2) as a pro-oxidant and a cheaper salt as a terminal oxidant.[2,3]A simple and robust, metal-free route for the oxidation of trifluoromethyl alcohols and secondary alcohols to ketones is described. The methodology employs sodium persulfate as a primary oxidant and a catalytic quantity of 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (acetamido-TEMPO, ACT, (2) with R = NHAc), and it is applicable to fluorinated and non-fluorinated alcohols. Going one step beyond, some recent advances in electrochemical oxidations of alcohols by using ACT as mediator are shown. In this way the oxidation of alcohols to ketones and aldehydes can be reached in a greener fashion substituting a chemical terminal oxidant by just an externally applied electron current.References[1] Leadbeater, N. E.; Bobbitt, J. M. Aldrichimica Acta 2014, 47 (3), 65–74.[2] Politano, F.; León Sandoval, A.; Witko, M. L.; Doherty, K. E.; Schroeder, C. M.; Leadbeater, N. E.European J. Org. Chem. 2022, 2022 (4), 38–41.[3] León Sandoval, A.; Politano, F.; Witko, M. L.; Leadbeater, N. E. Org. Biomol. Chem. 2022, 20 (3),667–671.