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Molecules 2016, 21(11), 1593; doi:10.3390/molecules21111593

Stereoselective Alkane Oxidation with meta-Chloroperoxybenzoic Acid (MCPBA) Catalyzed by Organometallic Cobalt Complexes

1
Semenov Institute of Chemical Physics, Russian Academy of Sciences, ulitsa Kosygina, dom 4, Moscow 119991, Russia
2
Chair of Chemistry and Physics, Plekhanov Russian University of Economics, Stremyannyi pereulok, dom 36, Moscow 117997, Russia
3
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia
This work was partly presented at the 16th International Congress on Catalysis, Beijing, China, 2016, lecture OF24.
*
Author to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Received: 23 October 2016 / Revised: 15 November 2016 / Accepted: 16 November 2016 / Published: 22 November 2016
(This article belongs to the Special Issue Reactions of Hydrocarbons and other C‒H Compounds)
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Abstract

Cobalt pi-complexes, previously described in the literature and specially synthesized and characterized in this work, were used as catalysts in homogeneous oxidation of organic compounds with peroxides. These complexes contain pi-butadienyl and pi-cyclopentadienyl ligands: [(tetramethylcyclobutadiene)(benzene)cobalt] hexafluorophosphate, [(C4Me4)Co(C6H6)]PF6 (1); diiodo(carbonyl)(pentamethylcyclopentadienyl)cobalt, Cp*Co(CO)I2 (2); diiodo(carbonyl)(cyclopentadienyl)cobalt, CpCo(CO)I2 (3); (tetramethylcyclobutadiene)(dicarbonyl)(iodo)cobalt, (C4Me4)Co(CO)2I (4); [(tetramethylcyclobutadiene)(acetonitrile)(2,2′-bipyridyl)cobalt] hexafluorophosphate, [(C4Me4)Co(bipy)(MeCN)]PF6 (5); bis[dicarbonyl(B-cyclohexylborole)]cobalt, [(C4H4BCy)Co(CO)2]2 (6); [(pentamethylcyclopentadienyl)(iodo)(1,10-phenanthroline)cobalt] hexafluorophosphate, [Cp*Co(phen)I]PF6 (7); diiodo(cyclopentadienyl)cobalt, [CpCoI2]2 (8); [(cyclopentadienyl)(iodo)(2,2′-bipyridyl)cobalt] hexafluorophosphate, [CpCo(bipy)I]PF6 (9); and [(pentamethylcyclopentadienyl)(iodo)(2,2′-bipyridyl)cobalt] hexafluorophosphate, [Cp*Co(bipy)I]PF6 (10). Complexes 1 and 2 catalyze very efficient and stereoselective oxygenation of tertiary C–H bonds in isomeric dimethylcyclohexanes with MCBA: cyclohexanols are produced in 39 and 53% yields and with the trans/cis ratio (of isomers with mutual trans- or cis-configuration of two methyl groups) 0.05 and 0.06, respectively. Addition of nitric acid as co-catalyst dramatically enhances both the yield of oxygenates and stereoselectivity parameter. In contrast to compounds 1 and 2, complexes 9 and 10 turned out to be very poor catalysts (the yields of oxygenates in the reaction with cis-1,2-dimethylcyclohexane were only 5%–7% and trans/cis ratio 0.8 indicated that the oxidation is not stereoselective). The chromatograms of the reaction mixture obtained before and after reduction with PPh3 are very similar, which testifies that alkyl hydroperoxides are not formed in this oxidation. It can be thus concluded that the interaction of the alkanes with MCPBA occurs without the formation of free radicals. The complexes catalyze oxidation of alcohols with tert-butylhydroperoxide (TBHP). For example, tert-BuOOH efficiently oxidizes 1-phenylethanol to acetophenone in 98% yield if compound 1 is used as a catalyst. View Full-Text
Keywords: alkanes; alcohols; metal complexes; X-ray analysis; meta-chloroperoxybenzoic acid (MCPBA); stereoselective oxidation alkanes; alcohols; metal complexes; X-ray analysis; meta-chloroperoxybenzoic acid (MCPBA); stereoselective oxidation
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MDPI and ACS Style

Shul’pin, G.B.; Loginov, D.A.; Shul’pina, L.S.; Ikonnikov, N.S.; Idrisov, V.O.; Vinogradov, M.M.; Osipov, S.N.; Nelyubina, Y.V.; Tyubaeva, P.M. Stereoselective Alkane Oxidation with meta-Chloroperoxybenzoic Acid (MCPBA) Catalyzed by Organometallic Cobalt Complexes. Molecules 2016, 21, 1593.

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