Catalysts for convenient aerobic alcohol oxidations in air: Systematic ligand studies in Pd/pyridine systems

Article abstract of DOI:10.1016/j.tet.2013.03.011

We report highly convenient Pd catalysts for the aerobic oxidation of alcohols, which are generated in situ by combining commercially available catalyst precursors. Systematic optimizations of the L- and X-type ligand environment and the employed additive allow the use of air as the sole oxidant without formation of Pd black. The resulting novel protocol provides quantitative yields of a broad variety of ketones and aldehydes.

Full text of DOI:10.1016/j.tet.2013.03.011

Tetrahedron 69 (2013) 5758e5764
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Catalysts for convenient aerobic alcohol oxidations in air: systematic
ligand studies in Pd/pyridine systems
*
Lukas C. John, Ahmet Gunay, Andrew J. Wood, Marion H. Emmert
Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
We report highly convenient Pd catalysts for the aerobic oxidation of alcohols, which are generated
in situ by combining commercially available catalyst precursors. Systematic optimizations of the L- and
X-type ligand environment and the employed additive allow the use of air as the sole oxidant without
formation of Pd black. The resulting novel protocol provides quantitative yields of a broad variety of
ketones and aldehydes.
Received 14 January 2013
Received in revised form 1 March 2013
Accepted 4 March 2013
Available online 13 March 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Dedicated to Melanie Sanford on the occa-
sion of her receipt of the Tetrahedron Young
Investigator Award
1. Introduction
2. Results and discussion
The oxidation of alcohols is an important fundamental reaction
that is widely employed in the synthesis of organic molecules.
Traditional methodologies to achieve this transformation typically
use stoichiometric amounts of wasteful oxidants, for example,
pyridinium dichromate1 or NMO.2 In contrast, alternative aerobic
alcohol oxidations are highly atom economical because the termi-
nal oxidant, molecular oxygen, is readily available and inexpensive.
Various transition metal compounds, such as Pd,3 Ru,4 and Cu5
complexes, catalyze this reaction.6 While these catalytic protocols
are highly useful, several drawbacks remain, which include high
catalyst loadings, the necessity to use pure oxygen gas, or tedious
syntheses of catalyst precursors. In the case of Pd catalysts, catalyst
decomposition and the formation of Pd black are frequent concerns
at low partial pressures of oxygen and low catalyst loadings.7 The
described drawbacks currently limit the usefulness of Pd-catalyzed
aerobic alcohol oxidations in the every-day synthesis of organic
molecules.
2.1. Reaction setup
For our initial ligand studies, we chose 1-phenyl-1-propanol (1)
as substrate due to its relatively low volatility; as an additional
benefit, ketone 2 is the only possible oxidation product, which
simplified assessing the catalytic activity of the tested systems. The
GC yields of 2 were determined after 2 and 24 h in order to gain
information about the short-term reactivity as well as the longevity
of the catalysts (Scheme 1). Toluene was used as solvent and
Pd(OAc)2 was employed as catalyst precursor; initially, AcOH
(0.50 equiv) was employed as additive as precedented in the
literature.8
In order to address these challenges, we have evaluated a series
of Pd catalysts that can be synthesized in situ from commercial
catalyst precursors and ligands. As the outcome of these studies, we
herein report highly convenient catalytic protocols that address all
the drawbacks outlined above. Systematic optimizations of the
used L- and X-type ligands and additives allow the use of 1 atm air
as the sole oxidant, avoid the formation of Pd black, and provide
excellent yields of carbonyl compounds from a variety of primary
and secondary alcohol substrates.
Scheme 1. Alcohol oxidation assay.
When using simple Pd(OAc)2 (2 mol %) in the absence of L-type
ligands, 3 and 14% yields of 2 were obtained after 2 and 24 h,
respectively (Scheme 1). We further observed the formation of Pd
black in these reactions, which demonstrates the low stability of
the catalyst at low partial pressures of oxygen. Thus, we concluded
that the chosen conditions were suitable for the evaluation of
ligand and additive effects.
* Corresponding author. Fax: þ1 508 831 4116; e-mail address: mhemmert@
wpi.edu (M.H. Emmert).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.03.011

L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
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2.2. Steric effects of pyridine-type ligands
substituents at 3- and/or 5-position.7 However, our findings are
contrary to results with Uemura’s protocol for aerobic alcohol ox-
idation under O2 atmosphere, in which 2,6-lutidine as ligand per-
forms worse than simple pyridine.3a,b
Bidentate ligands with substituents in ortho-position to the
ligation site have been shown to promote the Pd-catalyzed aerobic
oxidation of alcohols.9,10 Therefore, we hypothesized that mono-
dentate pyridine-type ligands with similar substitution patterns
may also accelerate alcohol oxidation and concurrently stabilize the
Pd catalyst. To test our hypothesis, we evaluated a variety of
pyridine-type (py) ligands with substituents at 2- and/or 6-position
(Scheme 2). All ligands were tested in Pd/py ratios of 1:1, 1:2, and
2.3. Electronic effects of pyridine-type ligands
We further evaluated ligands with different electronic charac-
teristics by testing pyridine ligands with electron-donating and
electron-withdrawing substituents in 3- or 4-position (Scheme 3).
Scheme 2. Oxidation of 1-phenyl-1-propanol with sterically differentiated py ligands.
1:4, as the Pd/py ratio is known to significantly influence the per-
formance of Pd catalysts in aerobic transformations.3b,11
In this study, the use of pyridines with electron-withdrawing
substituents (CF3, NO2, Cl) resulted in low catalytic activities and
catalyst decomposition. Conversely, electron-donating ligands (4-
tert-butyl pyridine 3, 4-methoxy pyridine 4, 4-dimethylamino
pyridine 5) showed an activating and stabilizing effect and excel-
lent yields (ꢁ96%) of the ketone 2 were obtained. Remarkably, in
several reactions (8 mol % of 3, 4, and 5; 4 mol % of 5), no catalyst
decomposition was observed, as indicated by the lack of Pd black in
the reaction mixture. These data clearly illustrate the superior
performance of 3, 4, and 5 in contrast to simple pyridine.
All catalytic systems explored (Scheme 2) show the highest ac-
tivity at Pd/py ratio of 1:4, a ratio that has been shown by Stahl to be
ideal with respect to catalyst activity and stability under an atmo-
sphere of O2 gas.11 Pyridine, the best ligand under Uemura’s con-
ditions,3a was employed as a reference ligand in this study and
provided a high yield of 2 (80ꢀ3%) after 2 h at a Pd/py ratio of 1:4;
however, the yield after 24 h was not improved (78ꢀ4%), which
suggests that catalyst decomposition is complete after 2 h. This hy-
pothesis is supported by the observations of Pd black in all reactions
employing pyridine. Compared to the results with pyridine, using
quinoline and acridine as ligands resulted in overall lower yields.
In contrast, methyl substituents in 2- and 6-position promoted
both the initial reactivity and the stability of the catalysts upon
prolonged heating; these trends were most significant with 2,6-
lutidine as ligand. For example, at Pd/py ratios of 1:1, the yield of
ketone 2 after 2 h was 13% higher with 2,6-lutidine than in the
analogous reaction with pyridine. Similar trends were observed
when comparing the reactions in which Pd/py ratios of 1:2 or 1:4
were used. Most remarkably, a quantitative yield of the oxidation
product 2 was obtained after 24 h with the catalytic system
Pd(OAc)2/2,6-lutidine (1:4), and no Pd black was observed in the
reaction mixture. When the even more sterically hindered ligand
2,6-diethyl pyridine was employed, lower yields and catalyst de-
composition were observed. We conclude from these data that
moderately bulky substituents in ortho-position to the ligation site
of a py ligand can be used to stabilize the catalyst at low oxygen
concentrations.
To gain further insight into the influence of electronically differ-
entiated py ligands on the initial reactivity, we measured the yields
of 2 after the shorter reaction time of 1 h and plotted the obtained
yields against the corresponding Hammett parameters
s. The
resulting diagrams (Scheme 4A and B) exhibit some scattering, but
two distinct trends can be observed: First, linear correlations are
obtained with 2 and 4 mol % of py, corresponding to Pd/py ratios of
1:1 and 1:2, respectively (Scheme 4A). This indicates a promoting
effect of electron-donating substituents, which is contrary to ob-
servations by Stahl and co-workers under O2 atmosphere using
Pd(OAc)2/py catalysts.11 Second, the highest initial catalytic activities
with 8 mol % py are observed at s-values close to 0, rendering pyr-
idine the most active ligand. Both electron-donating and electron-
withdrawing substituents result in a decrease of activity (Scheme
4B). These data suggest a change in the turnover-limiting step of
the reaction under these conditions.
2.4. Evaluation of X-type ligands and additives
Our results with substituents at 2- and 6-positions are compli-
mentary to a study published by Tsuji and co-workers who
explore the use of non-commercial pyridine ligands with bulky
As both basic and acidic additives have been reported to sig-
nificantly influence Pd-based aerobic oxidation catalysts,8,11,12 we
further studied the effect of carboxylic acids and carboxylates on

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L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
Scheme 3. Oxidation of 1-phenyl-1-propanol with electronically differentiated py ligands.
Scheme 4. Influence of electronically differentiated substituents on aerobic alcohol oxidation.
our catalytic protocol. All additives were initially evaluated using
2 mol % of Pd(OAc)2 and 4 mol % quinoline as catalyst (Scheme 5A).
This catalytic system shows mediocre activity and catalyst de-
composition in the presence on 0.50 equiv AcOH (24% yield of 2
after 24 h). Notably, our experiments (Scheme 5A) employing other
carboxylic acids demonstrated that most acids inhibit the catalytic
PivOH (step B), which favors the generation of a free coordination
site at Pd for the following -hydride elimination (step C). Thus an
acceleration of both steps A and B is expected when pivalate ligands
are ligated to the Pd center instead of acetate ligands.
b
Additional catalyst optimization experiments evaluated the ef-
fect of basic additives on the performance of the Pd(OAc)2/quino-
line (1:2) system. Strikingly, all carboxylates used (NaOPiv, NaOAc,
NBu4OAc) resulted in an enhancement of catalytic activity (2 h
yield >70%; 24 h yield >84%) when compared to reactions without
additive. Even though the solubilities of NaOAc and NBu4OAc in the
reaction solvent toluene differ considerably, statistically the same
yields were obtained with these two salts (Scheme 5A). The ob-
served beneficial effects of added carboxylates are precedented for
Pd(OAc)2/pyridine oxidation catalysts under 1 atm of O2.11
Although the different additives shown in Scheme 5A resulted
in a notable enhancement of the reactivity, all experiments using
Pd(OAc)2 as catalyst precursor suffered from the formation of Pd
black in the reaction mixture. Thus, we tested Pd(OPiv)2 as catalyst
precursor in a second series of experiment (Scheme 5B), as our own
results and literature precedence8 suggest that pivalate ligands can
stabilize and activate the Pd catalysts. Remarkably, the Pd(OPiv)2/
quinoline systems are far superior to the Pd(OAc)2/quinoline
t
activity. However, the use of the bulky carboxylic acid BuCO2H
(pivalic acid/PivOH) resulted in a significant increase of the catalytic
activity. We hypothesized that this surge in reactivity may be due to
the exchange of X-type ligands on the Pd center, which leads to
a stabilization and activation of the catalyst. Similar observations
have been reported by Sigman and co-workers, when employing Pd
carbene catalysts in the presence of acidic additives; these effects
have been linked back to both the basicity as well as the steric bulk
of the carboxylate ligands.8,12
Our data in combination with this literature precedence
suggest that alcohol deprotonation plays an important role in the
catalytic mechanism of the herein developed protocol (Scheme 6).
This conclusion takes into account the greater basicity of pivalate
ligands that is expected to accelerate the deprotonation step
(Scheme 6, step A); at the same time, the additional bulk introduced
by the pivalate ligands is expected to accelerate the dissociation of

L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
5761
Scheme 5. Additive effects on the catalytic activity of PdX2/quinoline (1:2) catalyst. X¼OAc, OPiv.
can be obtained when PivOH, NaOAc, or NaBu4OAc are used as
additives in combination with Pd(OPiv)2. Importantly, no Pd black
is observed in any of these reactions, which suggests a significant
stabilization of the Pd catalyst by the pivalate ligands. We conclude
from this study that simple X-type ligands as well as common
additives can be used to achieve excellent yields of ketone 2
through Pd catalyzed alcohol oxidation of 1-phenyl-1-propanol (1)
with air as the sole oxidant.
2.5. Combining additive and ligand effects
Our studies described above demonstrate that pyridine-type
ligands, X-type ligands, and additives can all be used to optimize
the activity of alcohol oxidation catalysts. Based on this knowledge,
we hypothesized that combining the best ligands and additives in
the same reaction setup would lead to even more reactive catalysts.
By lowering the Pd precursor loading to 1 mol % Pd(OPiv)2 we ex-
pected to obtain statistically significant comparisons. All py ligands
and Pd/py ratios (Scheme 7) were chosen based on our previous
Scheme 6. Alcohol deprotonation (A), PivOH dissociation (B) and following
elimination (C).
b-hydride
catalysts with respect to yields and catalyst stability. For example,
the reaction with Pd(OPiv)2/quinoline in the presence of 0.5 equiv
AcOH provides 63% yield after 24 h; the analogous reaction with
Pd(OAc)2 affords 24% yield. The highest yields after 24 h (ꢁ94% of 2)
Scheme 7. Optimizing the catalytic activity by combining L-type ligands, X-type ligands, and additives.

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L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
studies: 2,6-lutidine (Pd/py 1:4), 4 (Pd/py 1:4), and 5 (Pd/py 1:2)
have been shown to be the best performing pyridine-type ligands
in Sections 2.2 and 2.3 above. The Pd/additive ratio was kept con-
stant at the value used in the studies above (1:25). The employed
additives, PivOH and NaOAc, have both resulted in increased ac-
tivities in the additive experiments in Section 2.4; furthermore,
both conditions (acidic and basic) are potentially useful with re-
spect to applications of the herein developed methodology in
complex molecule settings. For comparison, the experiments were
also performed without any additives (Scheme 7).
All optimized catalyst systems tested under these conditions
produced high yields of ketone 2 after 24 h (>80%). The use of
additives (NaOAc or PivOH) enhances the 24 h yields by several
percent up to 99% with NaOAc and 98% with PivOH in combination
with 4-dimethylamino pyridine (5) as ligand. The lowest perfor-
mance of the catalyst systems was observed with 2,6-lutidine as
ligand (37e63% after 2 h vs 57e80% after 2 h with ligand 4 or 5).
We conclude from these experiments that the additives NaOAc and
PivOH can both be used to enhance the performance of Pd-based
alcohol oxidation catalysts.
Scheme 8. Dependence of the catalytic activity on the reaction temperature.
temperatures after 48 h in high yields (ꢁ62%), even though a clear
drop in activity was observed at temperatures below 100 ꢂC.
Based on the experiments described in this section, we conclude
that the system Pd(OPiv)2/5 is a highly active and stable catalyst
and can be used under a variety of different acidic, basic, and
neutral conditions.
2.7. Substrate scope
In order to demonstrate the wide applicability of our new cat-
alytic protocol, a combination of 2 mol % Pd(OPiv)2/4 mol % 5/
0.50 equiv PivOH was used to oxidize a broad scope of different
alcohols in air (Table 2). All secondary aliphatic and benzylic alco-
hols were oxidized in quantitative yields after 24 h; after 2 h, high
yields of these alcohols were observed (Table 2, entries 1e6) and
even sterically hindered secondary alcohols are oxidized efficiently
(entries 3 and 6).
Primary benzylic alcohols were oxidized selectively to the cor-
responding aldehydes (entries 8e12), with electron poor aldehydes
being more sluggish substrates (entries 11 and 12). Using 1-octanol
(entry 7) as an exemplary aliphatic primary alcohol substrate also
provided the corresponding aldehyde as the only product. How-
ever, the yield of 1-octanal (entry 7) with PivOH as additive was not
satisfactory after 2 h (56%), and was even lower (51%) after 24 h.
Gratifyingly, higher yields were observed without additive and
with 0.5 equiv NaOAc as additive (85% after 24 h for both reactions),
which suggests that the acid PivOH causes aldehyde decomposition
under the initially tested conditions. The above shown broad sub-
strate scope demonstrates the great potential of our novel catalytic
system for preparative oxidations using air as the only oxidant.
2.6. Challenging the best catalyst system
In order to explore the scope and limitations of our best catalytic
conditions, the following studies evaluate the best system
Pd(OPiv)2/5 (1:2) at low catalyst loadings, lower reaction temper-
atures, and for a wide variety of substrates.
The oxidation of 1-phenyl-1-propanol (1) was performed with
0.1 mol % of the catalyst system Pd(OPiv)2/5 (1:2) to gain in-
formation about the catalytic activity upon prolonged heating at
a high substrate/catalyst ratio. While maintaining the Pd/additive
ratio at 1:25, turnover numbers (TONs) up to 432 after 24 h could
be obtained, while no Pd black was formed (Table 1, entries 1, 3,
and 5). However, the TONs after 72 h did not differ significantly
from the TONs after 24 h under all tested conditions (entries 2, 4,
and 6). Since no formation of Pd black was observed, these data
suggest that other catalyst decomposition pathways are possible
in the tested systems. Raising the Pd/additive ratio to 1:250
(25 mol % PivOH) resulted in activation and stabilization of the
catalyst and, thus, higher TONs up to 684 were observed (entries
7 and 8).
Table 1
Pd catalyzed air oxidation of 1 at 0.1 mol % catalyst loadinga
Entry
Additive
Yield 2 (%)
TON
Pd black
1
2
3
4
5
6
7
8
PivOH (2.5 mol %)
PivOH (2.5 mol %)
d
43ꢀ2
52ꢀ3
21ꢀ0
22ꢀ1
29ꢀ2
31ꢀ2
54ꢀ2
68ꢀ2
432ꢀ17 (24 h)
515ꢀ34 (72 h)
210ꢀ1 (24 h)
223ꢀ9 (72 h)
287ꢀ20 (24 h)
307ꢀ19 (72 h)
537ꢀ15 (24 h)
684ꢀ16 (72 h)
n
n
n
n
n
n
n
n
d
NaOAc (2.5 mol %)
NaOAc (2.5 mol %)
PivOH (25 mol %)
PivOH (25 mol %)
a
Typical conditions: Pd(OPiv)2 (0.1 mol %), DMAP (5; 0.2 mol %), 1-phenyl-1-propanol (1; 0.20 mmol, 1.0 equiv), toluene (total volume of reaction mixture: 2 mL).
The catalytic system Pd(OPiv)2/5/PivOH (1:2:25) was further
challenged at lower temperatures (80 and 60 ꢂC) and at a catalyst
loading of 2 mol % (Scheme 8). Gratifyingly, the catalytic protocol
converted 1-phenyl-1-propanol (1) into the ketone 2 at all tested
3. Conclusions
In summary, we have shown that a systematic optimization of
Pd/py catalysts for the quantitative oxidation of alcohols with air

L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
5763
Table 2
Substrate scope of Pd catalyzed air oxidation of alcoholsa,b
Entry
1
Substrate
Product
Yieldc
Entry
7
Substrate
Product
Yieldc
88ꢀ2% (2 h)
56ꢀ1% (2 h)
51ꢀ1% (24 h)
85ꢀ1% (24 h)d
97ꢀ1% (24 h)
2
3
86ꢀ1% (2 h)
>99% (24 h)
8
9
90ꢀ2% (2 h)
>99% (24 h)
73ꢀ2% (2 h)
>99% (24 h)
>99% (2 h)
>99% (24 h)
4
57ꢀ1% (2 h)
>99% (24 h)
10
>99% (2 h)
>99% (24 h)
5
6
81ꢀ2% (2 h)
>99% (24 h)
11
12
60ꢀ2% (2 h)
69ꢀ1% (24 h)
67ꢀ1% (2 h)
>99% (24 h)
73ꢀ2% (2 h)
>99% (24 h)
a
Typical conditions: Pd(OPiv)2 (2.0 mol %), DMAP (5; 4.0 mol %), substrate (0.20 mmol, 1.0 equiv), PivOH (0.50 equiv), toluene (total volume of reaction mixture: 2 mL).
All products have been previously reported in the literature and are commercially available.
Yields were determined based on calibrated GC analysis.
b
c
d
Without additive or with 0.50 equiv NaOAc as additive.
as the sole oxidant is possible by exploiting both ligand and
4.2. General procedure for pyridine-type ligand screening at
2 mol % catalyst loading
additive effects. Based on our data, we conclude that electronic as
well as steric effects of the used L-type and X-type ligands play
an important role for the activity and stability of the catalysts:
the best catalytic efficiencies were obtained by employing mod-
erate bulky pyridines and pyridines with electron-rich sub-
stituents as ligands. Our studies using air further suggest
mechanistic differences to other catalytic reactions using pure O2
gas.3a,b,11 Furthermore, we have found that the Pd/py ratio sig-
nificantly influences the stability and activity of our catalysts. The
simplicity of our novel protocols eliminates the need for spe-
cialized reactors; importantly, the commercial availability of the
catalyst precursors and ligands avoids lengthy catalyst syntheses.
Due to these advantages, we expect that the developed methods
will further promote the use of Pd-catalyzed aerobic alcohol
oxidation in every-day organic synthesis. Based on the reported
findings, new catalysts with even better activity and stability in
alcohol oxidations can be developed and will be reported in due
course.
To a 20 mL scintillation vial, equipped with a Teflon-coated
stirbar, were added 400
mL (4.00 mmol, 2.0 mol % Pd(OAc)2;
0.100 mmol, 0.50 equiv AcOH) of a standard solution of Pd(OAc)2
(224.5 mg, 1.00 mmol) and AcOH (1.43 mL, 1.50 g, 25.0 mmol) in
100 mL toluene. 100
mL (4 mmol, 2 mol % ligand) of a standard so-
lution of ligand (1.00 mmol) in 10 mL toluene, and 400
m
L
(0.20 mmol, 1.0 equiv) of a standard solution of 1-phenyl-1-
propanol (1) (6.79 mL, 6.71 g, 50 mmol) in 100 mL toluene were
added to this mixture. The resulting solution was diluted with
toluene (1.10 mL) to a total volume of 2.0 mL.13
The vial was sealed with a Teflon-lined cap and heated to 100 ꢂC
on a pre-heated vial plate under vigorous stirring (1500 rpm). After
the reaction time was completed (2 or 24 h) the vial was taken off
the heating block and the mixture was allowed to cool to room
temperature. 10 mL of para-xylene of were added as GC-standard
and 3 mL of a saturated aqueous solution of K2CO3 was added to
neutralize the acid in the reaction mixture. After stirring the bi-
phasic mixture vigorously, the phases were separated and the or-
ganic phase was filtered through a plug of Celite. The filtrate was
diluted to a total volume of 1.5 mL with ethyl acetate and the yield
of 2 was determined by calibrated GC analysis.
4. Experimental section
4.1. General considerations
Experiments evaluating 4.0 and 8.0 mol % of ligand loading were
Reactions were conducted without rigorous exclusion of air and
moisture. All reagents were purchased and used as received. Stir-
bars used in catalytic reactions were cleaned with aqua regia for at
least 3 h, rinsed with copious amounts of water, and dried in an
oven at 120 ꢂC prior to use. Standard solutions were prepared using
volumetric flasks. All liquid reagents were dispensed by difference
using gas-tight Hamilton syringes. All oxidation products included
in the substrate scope have been previously reported in the liter-
ature and are commercially available. The identities of the oxida-
tion products were verified by comparison of the obtained data
from catalytic runs with GC and GCeMS data of the original com-
mercial samples.
performed according to the procedure above, using (i) 200
ligand standard solution (4.0 mol %, 8.00 mol of ligand) and
1.00 mL of toluene or (ii) 400 L of ligand standard solution
(8.0 mol %, 16.00 mol of ligand) and 0.800 mL of toluene. The total
mL of
m
m
m
volume of the reaction mixtures was 2 mL in all experiments.
4.3. General procedure for additive screening at 2 mol %
catalyst loading
900
m
L (4.00
m
mol, 2.0 mol %) of a standard solution of Pd(OAc)2
L (8 mol, 4.0 mol %)
(99.8 mg, 0.444 mmol) in 100 mL toluene, 80
m
m

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L.C. John et al. / Tetrahedron 69 (2013) 5758e5764
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m
L, 129.2 mg, 1.00 mmol) in
L (0.20 mmol,
1.0 equiv) of a standard solution of 1-phenyl-1-propanol (1)
(6.79 mL, 6.71 g, 50 mmol) in 100 mL toluene, and toluene (620 L)
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Acknowledgements
Acknowledgment is made to the Donors of the American
Chemical Society Petroleum Research Fund for partial support of
this research (ACS PRF 52119-DNI3). We also acknowledge Brendan
J. McKeogh for assistance with initial experiments.
8. Schultz, M. J.; Hamilton, S. S.; Jensen, D. R.; Sigman, M. S. J. Org. Chem. 2005, 70,
3343e3352.
Supplementary data
9. Conley, N. R.; Labios, L. A.; Pearson, D. M.; McCrory, C. C. L.; Waymouth, R. M.
Organometallics 2007, 26, 5447e5453.
10. Pearson, D. M.; Conley, N. R.; Waymouth, R. M. Organometallics 2011, 30,
1445e1453.
11. Steinhoff, B. A.; Guzei, I. A.; Stahl, S. S. J. Am. Chem. Soc. 2004, 126,
11268e11278.
Additional experimental procedures and data of further additive
and ligand screenings. Supplementary data associated with this
article can be found in the online version, at http://dx.doi.org/
10.1016/j.tet.2013.03.011.
12. Mueller, J. A.; Goller, C. P.; Sigman, M. S. J. Am. Chem. Soc. 2004, 126, 9724e9734.
13. The amount of oxygen in the vial was approximated to be 0.15 mmol (0.
77 equiv) based on the abundance of oxygen in air (20.95%), the remaining
volume in the vial (18 mL), and the ideal gas law. If the decomposition of the
primary reaction product H2O2 into O2 and H2O is assumed to be quantitative,
only 0.5 equiv of oxygen is needed for the reaction: alcoholþ0.
5O2/ketoneþH2O.
References and notes
1. Corey, E. J.; Schmidt, G. Tetrahedron Lett. 1979, 20, 399e402.
2. Ley, S. V.; Norman, J.; Griffith, W. P.; Marsden, S. P. Synthesis 1994, 1994,
639e666.