DOI: 10.1039/C3CC46051G
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electrolysis was conducted by applying a potential of -0.06 V (vs.
Notes and references
Fc/Fc+) for 20 hrs using Pt gauze working and counter electrodes.
A total of 38 C of charge were passed and GC/GC-MS (with
pentadecane as internal standard) analysis of the reaction mixture
determined that p-anisaldehyde was produced with a 32% yield.‡
This product yield corresponds to a Faradaic efficiency of >95%
for the two electron oxidation process. A control experiment was
run in parallel with the same solution mixture in the absence of an
applied potential, and after stirring at room temperature under Ar
*GE Global Research, Chemistry & Chemical Engineering Global
60 Technology Organization, Niskayuna, NY 12309 USA.
5
† Electronic Supplementary Information (ESI) available: Experimental
details for the deprotonation of 1 to form 2 with 1H NMR spectra, plot of
65 the linear increase in catalytic current, and other data.
See DOI: 10.1039/b000000x/
‡ An average of two runs determined p-anisaldehyde was produced with
a 32% yield.
10 (20 hrs) only a 4% yield of p-anisaldehyde was detected. An
additional control experiment was performed in which the
electrolysis conditions were the same as above, however 1 was
excluded. In this electrolysis experiment, 20 C of charge were
passed after applying a potential of -0.06 V for 20 hrs, and GC
15 analysis again determined only a 4% yield of p-anisaldehyde.
Charge passed in the latter electrolysis experiment resulted from
oxidation of sodium 4-nonylphenolate (in the absence of 1) based
on its CV data.† At the potential applied in electrolysis
experiments, both 4-methoxybenzyl alcohol and p-anisaldehyde
20 showed negligible oxidation currents by CV (voltammograms
may be found in ESI). Control experiments and data substantiated
that 1 was involved in the electrochemical oxidation process and
necessary for producing higher yields of selective aldehyde
product.
70
1
S. P. Annen, V. Bambagioni, M. Bevilacqua, J. Filippi, A.
Marchionni, W. Oberhauser, H. Schönberg, F. Vizza, C. Bianchini,
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3
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80 4 T. Matsumoto, K. Kim, and S. Ogo, Angew. Chem. Int. Ed., 2011, 50,
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25
When the electrolysis was repeated with 1, but allowed to run
for a total of 96 hrs, 78 C of charge passed resulting in a 64%
yield of p-anisaldehyde corresponding to a Faradaic efficiency of
94%. Electrolysis with
comparatively low applied potential relative to the only reported
7
”Low” applied potential is defined by quantitative comparison of
applied potentials between known catalysts. See ESI for a Table
comparing catalytic systems for the electro-oxidation of benzyl
alcohol.
1 at -0.06 V a
(vs. Fc/Fc+) is
90
30 example (to our knowledge) of an electrocatalytic system that
similarly produced benzaldehyde selectively from benzyl alcohol
with an 82% current efficiency (32% yield).11 The electrocatalyst
in that report, [Ru(bpea)(bpy)(H2O)]2+, required a fairly high
applied potential of 0.51 V (vs. Fc/Fc+) compared to -0.06 V (vs.
35 Fc/Fc+) used for 1.18
8
K.-C. Cheung, W.-L. Wong, D.-L. Ma, T.-S. Lai, and K.-Y. Wong,
Coord. Chem. Rev., 2007, 251, 2367.
95 9 S. Yamazaki, M. Yao, N. Fujiwara, Z. Siroma, K. Yasuda, and T.
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In this report, 1 was developed as an electro-oxidation catalyst
and displayed high Faradaic efficiency and selectivity in the
oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde at low
applied potential. The investigation of 1 in chemical catalysis
40 experiments demonstrated separation of electron and proton
transfer events in the dehydrogenation process, and enabled
identification of an anionic base that was compatible for
electrochemistry. Future studies will focus on establishing a
mechanistic understanding of the electrocatalytic process outlined
45 here, as well as the catalytic activity of 1 in the reverse electro-
reduction of p-anisaldehyde.
100 10 Y. Miyazato, T. Wada, and K. Tanaka, Bull. Chem. Soc. Jpn., 2006,
79, 745; H. Ozawa, T. Hino, H. Ohtsu, T. Wada, and K. Tanaka,
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17 A. J. Bard and L. R. Faulkner, Electrochemical Methods:
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50
18 V. V. Pavlishchuk and A. W. Addison, Inorg. Chim. Acta, 2000, 298,
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97 (Table 1 provided conversion constants to relate potentials
measured versus different reference electrodes).
55
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