Copper(II) and cobalt(II) tetrazole-saccharinate complexes as effective catalysts for oxidation of secondary alcohols

Frija, Luis M. T.; Alegria, Elisabete C. B. A.; Sutradhar, Manas; Cristiano, Maria De Lurdes; Ismael, Amin; Kopylovich, Maximilian N.; Pombeiro, Armando J. L.

http://hdl.handle.net/10400.1/9160

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Autores

Frija, Luis M. T.

Alegria, Elisabete C. B. A.

Sutradhar, Manas

Cristiano, Maria De Lurdes

Ismael, Amin

Kopylovich, Maximilian N.

Pombeiro, Armando J. L.

Resumo(s)

Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tertbutyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2 mol% content of the catalyst and under 20-50 W microwave irradiation, most reactions are complete within 10 min, presenting TONs up to 5.5 x 10(2) and TOFs up to 1.1 x 10(4)h(-1). No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined. (C) 2016 Elsevier B.V. All rights reserved.