ChemComm
Communication
the catalyst an interesting complement for the selective oxidation of
secondary alcohols to ketones utilizing peroxides as the oxidants.
Notes and references
1 (a) S. Caron, R. W. Dugger, S. G. Ruggeri, J. A. Ragan and D. H. B.
Ripin, Chem. Rev., 2006, 106, 2943–2983; (b) R. W. Dugger, J. A. Ragan and
D. H. B. Ripin, Org. Process Res. Dev., 2005, 9, 253–258; (c) M. Christmann,
Angew. Chem., Int. Ed., 2008, 47, 2740–2742.
2 (a) F. A. Carey and R. J. Sundberg, Advanced Organic Chemistry Part B:
Reactions and Synthesis, Springer, New York, 5th edn, 2007;
(b) H. Tohma and Y. Kita, Adv. Synth. Catal., 2004, 346, 111–124;
(c) A. V. Bekish, Tetrahedron Lett., 2012, 53, 3082–3085.
3 (a) R. Noyori, M. Aokib and K. Satoc, Chem. Commun., 2003,
1977–1986; (b) E. P. Talsi and K. P. Bryliakov, Coord. Chem. Rev.,
2012, 256, 1418–1434.
Scheme 1 Investigations to better understand the selectivity of the reaction.
4 (a) M. Darwish and M. Wills, Catal. Sci. Technol., 2012, 2, 243–255;
ˇ
(b) W. M. Czaplik, M. Mayer, J. Cvengrosm and A. J. von Wangelin,
ChemSusChem, 2009, 2, 396–417; (c) A. A. O. Sarhan and C. Bolm,
Chem. Soc. Rev., 2009, 38, 2730–2744; (d) E. B. Bauer, Curr. Org.
Chem., 2008, 12, 1341–1369; (e) S. Enthaler, K. Junge and M. Beller,
Angew. Chem., Int. Ed., 2008, 47, 3317–3321; ( f ) B. D. Sherry and
A. Fu¨rstner, Acc. Chem. Res., 2008, 41, 1500–1511; (g) A. Correa,
when recorded in the presence of 1-decanol. However, the spectro-
scopic changes were also significant in the presence of 2-decanol
and 1,2-octanediol (see ESI†). Whether any of the alcohols deactivate
the catalyst is the objective of our current research.
˜
O. G. Mancheno and C. Bolm, Chem. Soc. Rev., 2008, 37, 1108–1117.
¨
To investigate if the reaction proceeds through a free radical
mechanism, we performed the oxidation of 1,2-octanediol (6) in the
presence of 2,4,6-tri-tert-butylphenol (TTBP), a radical scavenger.9a
Catalytic and substoichiometric amounts of TTBP neither terminated
nor slowed down the reaction; although a stoichiometric amount of
TTBP did slow down the rate of the reaction. However, TTBP is known
5 (a) A. Al-Hunaiti, T. Niemi, A. Sibaouih, P. Pihko, M. Leskela and
´
T. Repo, Chem. Commun., 2010, 46, 9250–9252; (b) E. Balogh-Hergovich
and G. Speier, J. Mol. Catal. A, 2005, 230, 79–83; (c) A. G. J. Ligtenbarg,
P. Oosting, G. Roelfes, R. M. La Crois, M. Lutz, A. L. Spek, R. Hage and
B. L. Feringa, Chem. Commun., 2001, 385–386.
6 (a) F. Shia, M. K. Tsea, M.-M. Pohl, J. Radnik, A. Bru¨ckner, S. Zhang
and M. Beller, J. Mol. Catal. A, 2008, 292, 28–35; (b) A. J. Pearson and
Y. Kwak, Tetrahedron Lett., 2005, 46, 5417–5419; (c) D. Sloboda-
Rozner, P. L. Alsters and R. Neumann, J. Am. Chem. Soc., 2003, 125,
to be easily oxidized, losing its radical scavenger capability.9b,c
A
¨
5280–5281; (d) H. Hosseini-Monfared, C. Nather, H. Winkler and
catalytic amount of phenol shuts down the oxidation, but it
cannot be excluded at this time that phenol deactivates the
catalyst in a manner similar to primary alcohols.
C. Janiak, Inorg. Chim. Acta, 2012, 391, 75–82.
¨ ¨
¨
7 (a) B. Biswas, A. Al-Hunaiti, M. T. Raisanen, S. Ansalone, M. Leskela,
T. Repo, Y.-T. Chen, H.-L. Tsai, A. D. Naik, A. P. Railliet, Y. Garcia,
R. Ghosh and N. Kole, Eur. J. Inorg. Chem., 2012, 4479–4485; (b) B. Join,
Iron-catalyzed oxidation of alcohols with peroxides was suggested
to proceed through different mechanistic pathways.5b In hydride
transfer (HT) or hydrogen atom transfer (HAT) mechanisms,
hydrides10 or hydrogen atoms11 are transferred to the iron complex.
The involvement of a high-valent FenQO species in oxidation
reactions in HAT mechanisms has been investigated widely.11 Based
on the experiments performed herein, we cannot establish a
mechanism for the reaction. In [Fe(5)2]2+OTf2, all six coordina-
tion sites are occupied by ligands, and the system must first
form an open coordination site in order to activate the peroxide
oxidant or to generate an FenQO species. An outer sphere free
radical mechanism is also possible,12 and the iron complex could
maintain a low concentration of ꢀOH radicals in solution, which can
abstract a hydrogen atom from the alcohol. Investigations to
elucidate a mechanism for the title reaction are currently underway.
In conclusion, we reported herein the easily accessible iron
catalyst [Fe(5)2]2+OTf2 to selectively oxidize secondary alcohols
to the corresponding ketones in the presence of primary alcohols
(15 minutes, 3 mol% catalyst loading, an aqueous H2O2 oxidant,
room temperature, CH3CN solvent, 53 to 84% isolated yields).
¨
¨
¨
K. Moller, C. Ziebart, K. Schroder, D. Gordes, K. Thurow, A. Spannenberg,
K. Junge and M. Beller, Adv. Synth. Catal., 2011, 353, 3023–3030;
(c) Y. Kikukawa, K. Yamaguchi and N. Mizuno, Angew. Chem., Int. Ed.,
2010, 49, 6096–6100; (d) Y. M. A. Yamada, C. K. Jin and Y. Uozumi, Org.
Lett., 2010, 12, 4540–4543; (e) J. Wang, L. Yan, G. Qian, S. Li, K. Yang,
H. Liua and X. Wang, Tetrahedron, 2007, 63, 1826–1832; ( f ) S. L. Jain,
V. B. Sharma and B. Sain, Tetrahedron, 2006, 62, 4475–4479;
(g) D. Sloboda-Rozner, P. Witte, P. L. Alsters and R. Neumann, Adv.
Synth. Catal., 2004, 346, 339–345; (h) S. E. Martin and A. Garrone,
Tetrahedron Lett., 2003, 44, 549–552; (i) S. E. Martin and A. Garrone,
Tetrahedron Lett., 2003, 44, 4475–4479.
8 (a) M. Lenze, E. T. Martin, N. P. Rath and E. B. Bauer, ChemPlusChem,
2013, 78, 101–116; (b) M. Lenze, S. L. Sedinkin and E. B. Bauer, J. Mol.
Catal. A, 2013, 373, 161–171; (c) P. Shejwalkar, N. P. Rath and
E. B. Bauer, Dalton Trans., 2011, 40, 7617–7631; (d) P. Shejwalkar,
N. P. Rath and E. B. Bauer, Molecules, 2010, 2631–2650; (e) M. Lenze,
S. L. Sedinkin, N. P. Rath and E. B. Bauer, Tetrahedron Lett., 2010, 51,
2855–2858; ( f ) M. Lenze and E. B. Bauer, J. Mol. Catal. A, 2009, 309,
117–123.
9 (a) V. Piccialli, M. L. Graziano, M. R. Iesce and F. Cermola, Tetrahedron
Lett., 2002, 43, 8067–8070; (b) D. H. R. Barton, V. N. Le Gloahec, H. Patin
and F. Launay, New J. Chem., 1998, 559–563; (c) R. Bakshi and P. Mathur,
Inorg. Chim. Acta, 2010, 363, 3477–3488.
10 F. Shi, M. K. Tse, Z. Li and M. Beller, Chem.–Eur. J., 2008, 14, 8793–8797.
11 A.-R. Han, Y. J. Jeong, Y. Kang, J. Y. Lee, M. S. Seo and W. Nam,
Chem. Commun., 2008, 1076–1078.
´
The mild reaction conditions and the short reaction time make 12 K. Barbusinski, Ecol. Chem. Eng. S, 2009, 16, 347–358.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.