Room temperature aerobic copper-catalysed selective oxidation of primary alcohols to aldehydes

Article abstract of DOI:10.1002/adsc.200404063

A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is catalysed using a [copper(II)-(N ligand)_n] complex with TEMPO and a base as co-catalysts. In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported. Best results are obtained in acetonitrile/water as solvent using a copper(II) catalyst generated in situ from a Cu(II) salt with weak or non-coordinating anions and bipyridine ligands with electron-donating substituents. A reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.

Full text of DOI:10.1002/adsc.200404063

FULL PAPERS
Room Temperature Aerobic Copper±Catalysed Selective
Oxidation of Primary Alcohols to Aldehydes
a, b
b
b,
a
Patrick Gamez, Isabel W. C. E. Arends, Roger A. Sheldon, * Jan Reedijk
a
Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P. O. Box 9502, 2300 RA Leiden,
The Netherlands,
Fax: (þ31)-71-527-4671
b
Laboratory for Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology,
Julianalaan 136, 2628 BLDelft, The Netherlands
Fax: (þ31)-15-278-1415, e-mail: r.a.sheldon@tnw.tudelft.nl
Received: March 3, 2004; Accepted: May 27, 2004
th
Dedicated to Joe Richmond on the occasion of his 60 birthday.
Abstract: A novel and very mild method for the oxi- lyst generated in situ from a Cu(II) salt with weak
dation of primary alcohols to aldehydes with excellent or non-coordinating anions and bipyridine ligands
conversions has been developed. The reaction is car- with electron-donating substituents. A reaction mech-
ried out under air at room temperature and is cata- anism is postulated which resembles that of galactose
lysed using a [copper(II)-(N ligand) ] complex with oxidase, and in which TEMPO seems to be involved
n
TEMPO and a base as co-catalysts. In this paper, as a hydrogen acceptor.
the performance of a series of N-containing ligands,
as well as different copper(II) salt precursors in differ-
ent solvents are reported. Best results are obtained in Keywords: alcohols; aldehydes; biomimetic oxidation;
acetonitrile/water as solvent using a copper(II) cata- copper; galactose oxidase; TEMPO
Introduction
of molecular oxygen or in mild and highly selective aero-
[15]
bic oxidative transformations. It is therefore surpris-
The selective oxidation of primary alcohols to the corre- ing that only a few examples using cheap and ™green∫
[
16±18]
sponding aldehydes, which can be performed by a varie- copper catalysts and molecular oxygen
or hydrogen
[
19±26]
[20]
ty of methods, remains one of the most important func- peroxide are known so far.
tional transformations in the synthesis of fine chemi- ported the efficient use of CuCl(Phen-DEADH2)
Mark o¬ et al. first re-
[
1±5]
cals.
Typically, the oxidation of alcohols is accom- (Phen¼1,10-phenanthroline; DEADH ¼diethyl hy-
2
plished by stoichiometric amounts of metallic oxidants, drazinodicarboxylate) catalytic system for the oxidation
[
6,7]
mostly chromium(VI) reagents. Safety hazards asso- of primary and secondary alcohols under dioxygen at
[
21]
ciated with these oxidants and their toxic by-products, 908C. Stack et al. described a Cu(II) species, namely
and the difficulty to work-up the reaction mixtures are [Cu(II)BSP] where BSP symbolises a salen-type ligand
the main problems of such processes. Consequently, a with a binaphthyl backbone and thioether functions,
number of catalytic methods using complexes contain- able tocatalyse the oxidationof benzylicandallylic alco-
ing transition metals, such as palladium, rhodium or hols under dioxygen at room temperature. Wieghardt
ruthenium and clean oxidants, such as dioxygen or hy- et al. similarly reported the catalytic oxidation of pri-
drogen peroxide has been developed.
[
22]
[
8±13]
Nevertheless, mary and secondary alcohols by a dinuclear Cu(II)-phe-
many of these catalytic systems still exhibit some draw- noxyl complex at 208C under air with moderate conver-
[
23]
backs: (1) a low tolerance towards water, while water is sions. More recently, Knochel et al. followed by Gree
[
25]
formed stoichiometrically in the reaction; (2) the combi- et al. developed CuCl-TEMPO catalytic systems for
nation of flammable solvents with dioxygen at elevated the oxidation of alcohols under dioxygen, at 908C under
temperatures, which may result in dangerous situations; fluorous biphasic conditions and at 658C in an ionic liq-
[
26]
and (3) an often tedious work-up procedure.
uid, respectively. Lately, Punniyamurthy et al. report-
Copper is an essential trace element and it is, after iron ed the oxidation of alcohols to the corresponding car-
and zinc, the most abundant transition metal in the hu- boxylic acid analogues and ketones catalysed by a
[14]
man body. Thus, copper is found in various metallo- salen-type Cu(II) complex with H O as the source of
2
2
proteins, especially in enzymes implicated in the binding oxygen, at 808C in acetonitrile.
Adv. Synth. Catal. 2004, 346, 805±811
DOI: 10.1002/adsc.200404063
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805

FULL PAPERS
Patrick Gamez et al.
We recently developed a catalytic procedure for the equally be employed in place of t-BuOK) is probably
selective aerobic oxidation of primary alcohols to alde- to deprotonate the alcohol and, thus, favour the coordi-
hydes based on a CuBr (Bipy)-TEMPO system nation of the resulting alcoholate to the copper species,
2
[
27]
(
Bipy¼2,2’-bipyridine). This paper reports the use resulting in an increase of the activity.
of a series of closely related N-donor-containing ligands The exact role of TEMPO remains unclear. It might
for this reaction as well as different copper salts or sol- act as a hydrogen acceptor during the proposed catalytic
[
28]
vents in order to determine which parameters can affect cycle (Figure 2). The alcoholate coordinates to the
and/or improve the catalytic activity.
copper(II) complex I to lead to alkoxy species II. TEMPO
2
most likely coordinates to the copper(II) ion in an h
[
29,30]
manner (III) as reported by Caneshi et al.
The b-hy-
Results and Discussion
drogen is then transferred to TEMPO resulting in a rad-
ical-TEMPOH copper species (IV). Intramolecular
one-electron transfer leads to the aldehyde, TEMPOH
and Cu(I) species (V). Finally, species I are regenerated
by the TEMPO-mediated oxidation of Cu(I) to Cu(II)
species (I). The catalytic cycle is completed by the aero-
Oxidation of Benzyl Alcohol to Benzaldehyde
Catalysed by [CuBr (2,2’-bipyridine)]-TEMPO
2
The oxidation of primary alcohols to their correspond- bic oxidation of the TEMPOH to TEMPO.
ing aldehydes can be carried out at room temperature
in air with a [Cu(II)(N-ligand) ] complex (where n¼1
n
for didentate ligands and n¼2 for monodentate ones) Solvent Effect
as catalyst and 2,2,6,6-tetramethylpiperidinyl-1-oxy
(
TEMPO) and a base as co-catalysts (Figure 1).
The choice to use acetonitrile as a solvent was not arbi-
As shown in Table 1, the use of an N-donor ligand is trary. Indeed, a dramatic effect of acetonitrile on a sim-
essential. Only 6% of benzyl alcohol was converted to ilar reaction, namely the Cu(II)-catalysed oxidative cou-
benzaldehyde in 1.5 h when no 2,2’-bipyridine (Bipy) pling of 2,6-dimethylphenol has previously been report-
[
31]
was added (entry 1). This can well be due to the very ed. One explanation was the stabilisation of Cu(I)
poor solubility of the copper catalyst without ligand. species during the catalytic cycle caused by the coordi-
The presence of TEMPO is crucial for the oxidation, nation of acetonitrile molecules. Therefore, the oxida-
as no catalytic activity could be observed without it (en- tion reactions were performed in a 2:1 (v/v) acetoni-
try 2). The [CuBr (2,2’-bipyridine)]-TEMPO catalytic trile/water solvent mixture. As shown in Table 2, water
2
system is active without base, but 24 hours are required is necessary to obtain catalytic activity (entries 1 and
for the total conversion of benzyl alcohol to benzalde- 2). This is probably due to the insolubility of the base
hyde (entry 3). With 5 mol % potassium tert-butoxide in pure acetonitrile. In addition, the amount of water
added, only 2.5 hours are needed to fully and selectively also has an effect on the catalyst performance (entries 2
oxidise benzyl alcohol (entry 4). The function of the ba- and 3): only 47% conversion was achieved in 1.5 h. with
sic co-catalyst (sodium or potassium hydroxide could a 1:2 acetonitrile/water solvent mixture instead of 83%
with the 2:1 combination. This may be explained by a
decrease in the solubility of the benzyl alcohol in this
mixture.
A range of other water-miscible co-solvents in a 2:1
v/v) ratio with water in the oxidation of benzyl alcohol
(
were tested (Table 2; entries 4 to 6). The use of acetone
Figure 1. CuBr -catalysed oxidation of primary alcohols.
2
Table 2. Influence of the co-solvent/water mixture on the
[
CuBr (Bipy)]-catalysed oxidation of benzyl alcohol.
2
Table 1. CuBr -catalysed oxidation of benzyl alcohol to ben-
zaldehyde.
2
[a]
Entry
Solvent mixture (v/v)
Conversion [%]
Entry
Bipy
TEMPO
t-BuOK
Conversion [%]
0.5 h
1.5 h
1
2
3
4
no
yes
no
yes
yes
yes
yes
no
6
1
2
3
4
5
6
7
Acetonitrile
No reaction
yes
yes
yes
No reaction
Acetonitrile/Water (2/1)
Acetonitrile/Water (1/2)
Acetone/Water (2/1)
Dioxane/Water (2/1)
Sulfolane/Water (2/1)
38
24
17
9
36
5
83
47
48
78
75
9
[
b]
27[
c]
yes
83
[
a]
Selectivity>99% based on GC; conversions were deter-
mined after a reaction time of 1.5 h.
00% conversion after 24 h.
00% conversion after 2.5 h.
[a]
Toluene/Water (2/1)
[
[
b]
c]
1
1
[a]
Biphasic reaction.
806
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Copper-Catalysed Selective Oxidation of Primary Alcohols
FULL PAPERS
Figure 2. Proposed mechanism of (Cu-N-ligand-TEMPO)-catalysed oxidation of primary alcohols.
instead of acetonitrile led to a lower activity (entry 4). stituents on the pyridine ring. This is confirmed with
This decrease may be due to the non-coordination of sol- the 2,2’-bipyridine derivatives (entries 7, 9 and 10). In-
vent molecules to the metal centre. On the contrary, a deed, the catalytic activities increase with the donating
very good conversion is achieved with dioxane (entry character of the para-substituents, from 83% conversion
5
), which is also known to coordinate to copper species in 1.5 h for 2,2’-bipyridine (entry 7) to total conversion
[32]
albeit weakly. Similar reaction rates to the ones ob- in 1.5 h for 4,4’-dimethyl-2,2’-bipyridine (MeBipy; en-
tained with acetonitrile were obtained when sulfolane try 9) and in 1 h for 4,4’-dimethoxy-2,2’-bipyridine
was used as co-solvent (entry 6). Once again, the coordi- (MeOBipy; entry 10). The last ligand tried was 1,10-phe-
nation of sulfolane molecules during the catalytic cycle nanthroline (entry 11) which showed a good catalytic ac-
[33]
is possible, which probably enhances the activity. Fi- tivity of its copper complex.
nally, the biphasic oxidation resulting from the utiliza-
At this point, it has to be mentioned that, after the end
tion of toluene (entry 7) showed a very poor catalytic ac- of the oxidation reaction, the copper catalyst is still ac-
tivity because of an unsatisfactory mixing of the reac- tive. For example, the addition of one more equivalent
tants.
of benzyl alcohol to the reaction mixture using MeOBi-
py as ligand led to its total conversion in 3 h. (entry 10).
However, the addition of another 5 mol % of TEMPO
Effect of the Ligand Structure and the Copper(II) Salt was necessary (entry 10) for this oxidation to proceed.
Precursor
Indeed, the concentration of TEMPO (determined by
GC) stays constant during the course of the reaction
Several N-containing ligands were tested with CuBr2 and dramatically drops when all the substrate is con-
[
28,34]
and the results are reported in Table 3. All N-donors em- sumed. TEMPO is deactivated
ployed led to reasonable to very good conversions. The nism which is currently under investigation.
coppercomplexes from monodentate ligands are less ac- Different copper(II) salts were tested with 2,2’-bipyr-
through a mecha-
tive than those from the didentate ones, which is most idine as catalyst precursors for the oxidation of benzyl
likely related to the smaller association constants. Activ- alcohol and the results are reported in Table 3. Copper(II)
ities with 1-methylimidazole and 1-benzylimidazole chloride and copper(II) nitrate gave the least active cat-
(
entries 1 and 2) are comparable while 4-cyanopyridine alysts with only 60 and 66% conversion, respectively, af-
and 4-methoxypyridine (entries 3 and 4) behave in com- ter 1.5 h (entries 5 and 6). Copper(II) bromide led to the
pletely different manners. The reason is certainly the formation of 83% benzaldehyde in the same reaction
electron-withdrawing and -donating effects of the sub- time (entry 7). Copper(II) perchlorate was found to be
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Patrick Gamez et al.
Table 3. Influence of the copper(II) salt and the ligand on the [CuX (ligand)]-catalysed oxidation of benzyl alcohol to ben-
2
zaldehyde.
Entry
Cu(II) saltþligand
Conversion [%]
.5 h
0
1.5 h
1
2
3
4
5
6
7
8
9
CuBr þ1-methylimidazole
26
22
11
9
30
30
38
42
78
85
36
53
68
12
78
60
66
83
90
2
CuBr þ1-benzylimidazole
2
CuBr þ4-cyanopyridine
2
CuBr þ4-methoxypyridine
2
CuCl þ2,2’-bipyridine
2
Cu(NO ) þ2,2’-bipyridine
3
2
CuBr þ2,2’-bipyridine
2
Cu(ClO ) þ2,2’-bipyridine
4
2
CuBr þ4,4’-dimethyl-2,2’-bipyridine
100[
2
a, b]
1
1
0
1
CuBr þ4,4’-dimethoxy-2,2’-bipyridine
100
75
2
CuBr þ1,10-phenanthroline
2
[
[
a]
1
00% conversion to benzaldehyde reached within one hour.
b]
After 2 h reaction time, 10 more mmol of benzyl alcohol were added as well as 0.5 mmol of TEMPO. 100% conversion to
benzaldehyde was achieved in 3 h.
the best catalyst precursor with 90% conversion ach-
ieved after 1.5 h (entry 8). These differences are likely
associated to the propensity for dissociation of the anion
from the copper centre. Chloride and nitrate ions are
more strongly coordinated to copper than bromide or
perchlorate anions, the latest even being non-coordinat-
ing. Therefore, it is easier, for the alcoholate, to enter the
copper coordination sphere when perchlorate is the
counter-ion rather than chloride. In this regard, coun-
ter-ions like tetrafluoroborate or triflate are expected
tolead to the same results. This is aplausibleexplanation
for the different activities observed.
Figure 3. Possible explanations for the lack of reactivity of
secondary alcohols: a) Steric hindrance due to the methyl
group of the secondary alcohol preventing the formation of
species III in the catalytic cycle; b) Stabilisation of the radical
species IV by the second b-hydrogen of the primary alcohol.
Substrate Scope
Various primary benzylic, allylic and aliphatic alcohols
have been successfully oxidized to their corresponding
carbonyl derivatives (Table 4). Benzyl alcohol is totally molecule. Furthermore, in the case of primary alcohols,
and selectively converted to benzaldehyde in 2.5 hours the second b-hydrogen atom can be bonded to the oxy-
(
entry 1). The same result can be achieved in 1 hour gen atom of TEMPOH, stabilising the radical inter-
when MeOBipy is used as a ligand (see Table 3, en- mediate IV (Figure 3). This is obviously not possible
try 10). This corresponds to a TOF of 20 h which is with secondary alcohols.
ꢀ
1
an excellent result for a room temperature oxidation re-
These results are indeed confirmed when octan-1-ol
action involving a copper catalyst. Surprisingly, no reac- and octan-2-ol are used (Table 4, entries 5 and 7). Oc-
tion was observed with 1-phenylethanol, an activated tan-1-ol was oxidised in 61% conversion and>99% se-
secondary benzylic alcohol (entry 2). Recently, we lectivity after one day at room temperature (95% at
have described a Cu(I)-TEMPO system able to catalyse 408C, entry 6) while no octan-2-one formation is ob-
the oxidation of primary and secondary alcohols in served with octan-2-ol. Allylic alcohols, crotyl alcohol
[28]
DMF, indicating the involvement of different active and geraniol (entries 3 and 4) were converted to the cor-
species in the present study. This lack of reactivity of sec- responding aldehydes in excellent yields (91 and 100%,
ondary alcohols with the [Cu(II)(N ligand)] catalyst may respectively) and selectivities as no by-products were
be explained by two factors affecting the catalytic cycle. detected by gas chromatography. These data (entries 1,
Steric effects of the methyl group can hinder the forma- 3, 4 and 5) clearly demonstrate that the oxidation of ac-
tion of species III (Figures 2 and 3), crucial for the CꢀH tivated alcohols is faster than aliphatic ones, indicating
abstraction from the alcohol by the coordinated TEMPO that the hydrogen abstraction from the a-carbon atom
808
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Copper-Catalysed Selective Oxidation of Primary Alcohols
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Table 4. [CuBr (Bipy)]-catalysed oxidation of alcohols to aldehydes under air.
2
[a]
Entry
Alcohol
Time [h]
Conversion [%]
1
2
3
4
5
6
7
8
9
Benzyl alcohol
1-Phenylethanol
Crotyl alcohol
Geraniol
Octan-1-ol
2.5
5
5
100
No reaction
91
100
61[
5
24
24
5
1.5
1.5
b]
Octan-1-ol
Octan-2-ol
95
[c]
No reaction
[
d]
Benzyl alcoholþOctan-2-ol
67/0[
e]
Benzyl alcoholþ1-Phenylethanol
63/0
[a]
[b]
[c]
[d]
[e]
Selectivity in aldehyde>99%, based on GC.
Reaction performed at 40 C.
No oxidation after 24 h.
0
6
7
7% Benzaldehyde and no octan-2-one detected.
2% Benzaldehyde after 2.5 h. and no acetophenone detected.
by TEMPO (III to IV, Figure 2) is rate-determining in copper(II) salt and an aromatic didentate nitrogen-con-
the reaction. taining ligand such as 4,4’-dimethoxy-2,2’-bipyridine. In
Finally, a mixture of benzyl alcohol and octan-2-ol was addition, the reaction requires a baseand TEMPO as co-
reacted with air in the presence of the copper(II)- catalysts. The catalytic activity is enhanced when a wa-
TEMPO-base catalyst (entry 8). The result shows the ter-miscible co-solvent (acetonitrile, dioxane or sulfo-
specificity of the catalytic system towards primary alco- lane), which may act as a labile copper ligand during
hols. Thus, 67% of the benzyl alcohol was converted the catalytic cycle, is used. The reaction rates are also de-
whereas octan-2-ol remained unreacted. The same fea- pendent on the copper salt precursor and the electron-
ture was observed with a mixture of benzyl alcohol donating character of the para-substituent on the aro-
and 1-phenylethanol (entry 9) where 63% benzalde- matic rings of the ligand. This catalytic system can be
hyde was produced within 1.5 h while no acetophenone considered as a synthetic model of galactose oxidase as
could be detected. The oxidation of 72% benzyl alcohol both the observed chemoselectivity and the proposed
after 2.5 h (entry 9) instead of 100% (entry 1) tends to reaction mechanism are close to those of the natural
indicate that both benzylic alcohols are able to coordi- copper enzyme. The mechanism of the oxidation is the
nate to the Cu(II) ion. This competitive coordination subject of further investigations, and specifically UV-
may lead to a lower formation of benzaldehyde as less Vis, EPR and EXAFS measurements are expected to
binding sites are available for benzyl alcohol. This che- lead to more insights.
moselectivity is a typical characteristic of the natural
copper protein galactose oxidase (GOase). GOase is a
mononuclear type-2 copper enzyme that selectively cat-
alyses the two-electron oxidation of a large number of
Experimental Section
primary alcohols to their corresponding aldehydes, cou-
pled with the reduction of dioxygen to hydrogen perox-
ide (Figure 4).
General Remarks
[35±37]
The solvents, the copper(II) salts, the primary alcohols and the
corresponding aldehydes are commercially available and were
used without further purification. The yields of aldehydes were
determined by GC analyses, carried out with a Varian Star 3400
instrument equipped with a CP Sil 5-CB column (50 mꢁ
The reaction mechanism proposed for the TEMPO-
mediated oxidation reaction (Figure 2) is very similar
to one suggested for GOase (Figure 4b), with TEMPO
playing the role of the protein-bound phenoxyl radical.
Furthermore, the key catalytic species III and IV (Fig-
0
.53 mm) or carbowax column (50 mꢁ0.53 mm) using decane
ure 2) are analogous to the species B and C found in as internal standard.
the copper protein (Figure 4b) which also oxidises ben-
[
38]
zylic and allylic alcohols to aldehydes.
Typical Oxidation Procedure
The oxidation of alcohols was carried out under air in a 50-mL
three-necked, round-bottom flask equipped with a magnetic
stirrer. Typically, the alcohol (10.0 mmol) and decane
Conclusion
A new and mild catalytic system for the effective and se-
(
2.0 mmol; GC internal standard) were dissolved in 15 mLof
lective aerobic oxidation of primary alcohol to aldehyde a CH CN/H O (2:1) solvent mixture. 56 mg (0.5 mmol) of po-
3
2
has been developed. The optimum catalyst consists of a tassium tert-butoxide (potassium hydroxide can be used as
Adv. Synth. Catal. 2004, 346, 805±811
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Patrick Gamez et al.
Figure 4. a) Enzymatic oxidation of galactose with the reduction of O to H O ; b) Proposed reaction mechanism for galactose
2
2
2
[36]
oxidase.
well) were added followed by 112 mg (0.5 mmol) of copper(II)
bromide, resulting in blue-green suspension. 78 mg
0.5 mmol) of 2,2’-bipyridine were then introduced leading to
[5] M. Musawir, P. N. Davey, G. Kelly, I. V. Kozhevnikov,
a
Chem. Commun. 2003, 1414±1415.
(
[
6] G. Cainelli, G. Cardillo, Chromium Oxidations in Organ-
ic Chemistry, Springer, Berlin, 1984.
a dark-blue mixture. Finally, 2,2,6,6-tetramethylpiperidinyl-1-
oxy (TEMPO) (78 mg; 0.5 mmol) was added and the reaction
suspension immediately turned brown-orange and clear
dark-red after 2±3 minutes. Samples (0.5 mLwhich were ex-
tracted with Et O/H O) of the reaction mixture were taken
[
7] W. S. Trahanovsky, Oxidation in Organic Chemistry,
(
Eds.: A. T. Blomquist, H. Wasserman), Academic Press:
New York, 1978.
2
2
[
8] T. Iwahama, Y. Yoshino, T. Keitoku, S. Sakaguchi, Y. Ish-
ii, J. Org. Chem. 2000, 65, 6502±6507.
out regularly to monitor the reaction by GC. The products of
the reaction were determined by comparison with the commer-
cially available carbonyl compounds.
[9] R. Lenz, S. V. Ley, J. Chem. Soc. Perkin Trans. 1 1997,
291±3292.
3
[
[
10] I. E. Marko, P. R. Giles, M. Tsukazaki, I. Chelle-Reg-
naut, C. J. Urch, S. M. Brown, J. Am. Chem. Soc. 1997,
Acknowledgements
1
19, 12661±12662.
11] M. J. Schultz, C. C. Park, M. S. Sigman, Chem. Commun.
002, 3034±3035.
Financial support from COST Action D21/003/2001 and the
Dutch National Research School Combination Catalysis
2
(
HRSMC and NIOK) is gratefully acknowledged.
[12] B. Z. Zhan, M. A. White, T. K. Sham, J. A. Pincock, R. J.
Doucet, K. V. R. Rao, K. N. Robertson, T. S. Cameron, J.
Am. Chem. Soc. 2003, 125, 2195±2199.
[
[
[
[
13] H. B. Ji, T. Mizugaki, K. Ebitani, K. Kaneda, Tetrahedron
Lett. 2002, 43, 7179±7183.
14] E. Ochiai, Bioinorganic Chemistry, An Introduction, Al-
lyn and Bacon, Boston, 1977.
15] P. Gamez, P. G. Aubel, W. L. Driessen, J. Reedijk, Chem.
Soc. Rev. 2001, 30, 376±385.
16] M. F. Semmelhack, C. R. Schmid, D. A. Cortes, C. S.
Chou, J. Am. Chem. Soc. 1984, 106, 3374±3376.
References
[1] R. A. Sheldon, J. K. Kochi, Metal-Catalysed Oxidations
of Organic Compounds, Academic Press, New York,
1
981.
[
[
[
2] A. E. J. de Nooy, A. C. Basemer, H. van Bekkum, Syn-
thesis 1996, 1153±1156.
3] R. A. Sheldon, I. W. C. E. Arends, A. Dijksman, Catal.
Today 2000, 57, 157±166.
4] T. Mallat, A. Baiker, Catal Today 1994, 19, 247±283.
[17] M. F. Semmelhack, C. R. Schmid, D. A. Cortes, Tetrahe-
dron Lett. 1986, 27, 1119±1122.
810
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 805±811

Copper-Catalysed Selective Oxidation of Primary Alcohols
FULL PAPERS
[
18] I. P. Skibida, A. M. Sakharov, Catal. Today 1996, 27,
87±193.
[29] A. Caneschi, A. Grand, J. Laugier, P. Rey, R. Subra, J.
Am. Chem. Soc. 1988, 110, 2307±2309.
1
[
19] I. E. Marko, P. R. Giles, M. Tsukazaki, I. Chelle-Reg-
naut, A. Gautier, S. M. Brown, C. J. Urch, J. Org.
Chem. 1999, 64, 2433±2439.
[30] J. Laugier, J. M. Latour, A. Caneschi, P. Rey, Inorg.
Chem. 1991, 30, 4474±4477.
[31] P. Gamez, C. Simons, R. Steensma, W. L. Driessen, G.
Challa, J. Reedijk, Eur. Polym. J. 2001, 37, 1293±1296.
[32] J. C. Barnes, T. J. R. Weakley, Acta Crystallogr. B 1977,
33, 921±923.
[33] R. D. Willett, D. Swank, K. Chang, S. Hawkinson, Acta
Crystallogr. A 1969, A 25, S175.
[34] A. Dijksman, A. Marino-Gonzalez, A. M. I. Payeras,
I. W. C. E. Arends, R. A. Sheldon, J. Am. Chem. Soc.
2001, 123, 6826±6833.
[
[
[
[
[
20] I. E. Marko, P. R. Giles, M. Tsukazaki, S. M. Brown, C. J.
Urch, Science 1996, 274, 2044±2046.
21] Y. Wang, J. L. DuBois, B. Hedman, K. O. Hodgson,
T. D. P. Stack, Science 1998, 279, 537±540.
22] P. Chaudhuri, M. Hess, U. Florke, K. Wieghardt, Angew.
Chem. Int. Ed. 1998, 37, 2217±2220.
23] G. Ragagnin, B. Betzemeier, S. Quici, P. Knochel, Tetra-
hedron 2002, 58, 3985±3991.
24] B. Betzemeier, M. Cavazzini, S. Quici, P. Knochel, Tetra-
hedron Lett. 2000, 41, 4343±4346.
[35] Y. Wang, T. D. P. Stack, J. Am. Chem. Soc. 1996, 118,
13097±13098.
[
[
25] I. A. Ansari, R. Gree, Org. Lett. 2002, 4, 1507±1509.
26] S. Velusamy, T. Punniyamurthy, Eur. J. Org. Chem. 2003,
[36] M. M. Whittaker, J. W. Whittaker, Biophys. J. 1993, 64,
762±772.
3
913±3915.
[37] M. M. Whittaker, Y. Y. Chuang, J. W. Whittaker, J. Am.
Chem. Soc. 1993, 115, 10029±10035.
[38] M. M. Whittaker, V. L. Devito, S. A. Asher, J. W. Whit-
taker, J. Biol. Chem. 1989, 264, 7104±7106.
[
27] P. Gamez, I. W. C. E. Arends, J. Reedijk, R. A. Sheldon,
Chem. Commun. 2003, 2414±2415.
28] A. Dijksman, I. W. C. E. Arends, R. A. Sheldon, Org. Bi-
omol. Chem. 2003, 1, 3232±3237.
[
Adv. Synth. Catal. 2004, 346, 805±811
asc.wiley-vch.de
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