A Novel Process for Selective Ruthenium-Catalyzed Oxidation of Naphthalenes
electron-poor 2-bromonaphthalene yielded no qui- Acknowledgements
none at all (Table 3, entries 6 and 7).
We thank the State of Mecklenburg-Western Pomerania, the
Finally, the oxidation of monohydroxylated arenes
was studied. This reaction is also of significant indus-
trial interest, especially for the preparation of vitamin
E intermediates.[20] To our delight yields up to 83%
were achieved for the tested substrates.
Federal Ministry of Education and Research (BMBF), and
the Deutsche Forschungsgemeinschaft for funding of this re-
search.
More specifically, 2-methyl-1-naphthol, a possible
intermediate in the oxidation of 1 towards 2,[16] and 1-
naphthol are both oxidized in a yield of 78% (Table 3,
entries 9 and 10). In addition, different methylated
benzoquinones are obtained in 75–83% yield
(Table 3, entries 11–13).
In summary, we demonstrated the successful opti-
mization of the ruthenium-catalyzed oxidation of 2-
methylnaphthalene with environmentally benign hy-
drogen peroxide as oxidant. In our novel system no
strong acids are required and practical hydrogen per-
oxide (30% solution in water) can be used, so making
the process safer. Various naphthalene derivatives are
oxidized with good to excellent yields and high regio-
selectivity for the alkylated substrates. Applying
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ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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