Aerobic Oxidation of Benzylic Alcohols in Water by 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)/Copper(II) 2-N-Arylpyrrolecarbaldimino Complexes

Authors

  • Paweł J. Figiel,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
    2. Current address:Centro de Quimica Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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  • Ahlam Sibaouih,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
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  • Jahir Uddin Ahmad,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
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  • Martin Nieger,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
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  • Minna T. Räisänen,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
    2. Current address: School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, United Kingdom
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  • Markku Leskelä,

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
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  • Timo Repo

    1. Laboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FI-00014 University of Helsinki, Finland, Fax: (+358)-9191-50198; phone: (+358)-9191-50194
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Abstract

Novel copper(II) 2-N-arylpyrrolecarbaldimine-based catalysts for the aerobic oxidation of benzylic alcohols mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are reported. The catalytic activity for both synthesized and in situ made complexes in alkaline water solutions was studied revealing high efficiency and selectivity (according to GC selectivity always >99%) for both of these catalytic systems. For example, quantitative conversion of benzyl alcohol to benzaldehyde can be achieved with the in situ prepared bis[2-N-(4-fluorophenyl)-pyrrolylcarbaldimide]copper(II) catalysts in 2 h with atmospheric pressure of O2 at 80 °C. Interestingly, these catalysts can utilize dioxygen as well as air or hydrogen peroxide as the end oxidants, producing water as the only by-product.

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