Aerobic oxidation of cyclopentane-1,2-diols to cyclopentane-1,2-diones on Pt/C catalyst

Article abstract of DOI:10.1055/s-2008-1032056

A new method for the aerobic oxidation of cyclopentane-1,2-diols to corresponding 1,2-diones using heterogeneous Pt/C catalyst in the presence of LiOH is described. Different functional groups tolerate the oxidation conditions. Yields of 1,2-diones up to 76% were achieved. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1032056

LETTER
347
Aerobic Oxidation of Cyclopentane-1,2-diols to Cyclopentane-1,2-diones on
Pt/C Catalyst
O
xidatio
n
n
of Cyclope
d
ntane-1,2-di
r
eclopentanek
-1,2-diones Reile,a Anne Paju,a Margus Eek,b Tõnis Pehk,c Margus Lopp*a
a
Department of Chemistry, Faculty of Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
Fax +372(620)2828; E-mail: lopp@chemnet.ee
b
c
Prosyntest Ltd, Akadeemia tee 15, 12618 Tallinn, Estonia
National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Received 5 October 2007
domino oxidation, leading to tertiary hydroxyketones and
lactone acids,9 which are useful as the building blocks for
natural compounds.10
Abstract: A new method for the aerobic oxidation of cyclopentane-
1,2-diols to corresponding 1,2-diones using heterogeneous Pt/C cat-
alyst in the presence of LiOH is described. Different functional
groups tolerate the oxidation conditions. Yields of 1,2-diones up to
76% were achieved.
In the present paper we reveal our results on a new method
of aerobic oxidation of vicinal cyclopentane diols to 1,2-
Key words: diols, ketones, heterogeneous catalysis, oxidation,
platinum
diketones using
(Scheme 1).
a
heterogeneous Pt/C catalyst
We have found that aerobic oxidation on a commercially
available Pt/C catalyst11 at 60 °C converts cis-1,2-diols 1
into the corresponding 1,2-diones 3. In our preliminary
experiments toluene was used as a solvent for hydropho-
bic substrates, water for hydrophilic substrates, and a mix-
ture of MeCN and H2O as a universal medium for both
types of substrates. In these cases some amount of hy-
droxyketone 2 was also isolated, indicating that the oxida-
tion occurred in the succession: diol – hydroxyketone –
dione. In the case of 1a intermediate hydroxy ketone 2a
was isolated and identified by NMR. Presence of a minor
amount of the regioisomeric hydroxy ketone 2a¢ was also
observed in the spectrum.
Catalytic dehydrogenation is a common method for the
oxidation of alcohols to ketones. The use of atmospheric
air oxygen as an oxidant is preferred due to its ‘green’ na-
ture. The first reports on the platinum-metal-catalyzed
aerobic oxidations of alcohols date back to the seventies.1
Since then a variety of such oxidation methods have been
developed for the conversion of allylic and benzylic alco-
hols, as well as of nonactivated primary and secondary al-
iphatic alcohols, into carbonyl compounds. Both, the
homogeneous catalysis using metal complexes in organic
solvents2 or in water3 and the heterogeneous catalysis us-
ing easily recoverable traditional catalysts4 or metal
nanoparticles5 are used. Oxidation has been carried out in
different solvents: common organic solvents,5a,6 wa-
ter,4a,5b and supercritical carbon dioxide.7
The process is strongly dependent on the amount of oxy-
gen available to the reaction medium. We established that
the amount of oxygen that was present in the solvent and
in the catalyst converts approximately 30% of the sub-
strate into the product. Therefore, additional oxygen is
needed to complete the process. On the other hand, unre-
stricted access of air to the reaction system lowers the
yield of the product, presumably by overoxidizing the
There are only a few methods for oxidizing diols to
diones6b,8 and no methods for the catalytic aerobic oxida-
tion of cyclopentane-1,2-diols to the corresponding 1,2-
diketones available in literature. Cyclopentane-1,2-diones
were of interest to us as substrates for the asymmetric
R
R
R
R
R
cat.
O2
cat.
O2
+
O
OH
HO
O
HO
OH
O
O
O
OH
2'
1
3
2
R = a CH2CH2OBn
b CH2CH2OH
c Me
d CH2COOt-C5H11
e CH2CH2NHBoc
f Ph
g CH2CONH2
Scheme 1
SYNLETT 2008, No. 3, pp 0347–0350
x
x.
x
x.
2
0
0
8
Advanced online publication: 16.01.2008
DOI: 10.1055/s-2008-1032056; Art ID: G30807ST
© Georg Thieme Verlag Stuttgart · New York

348
I. Reile et al.
LETTER
product to carboxylic acids.8b Thus, better results were ob-
tained when the reactor was periodically flushed with
fresh air (in ca. 4 h intervals) during 16–20 hours. Using
this procedure with 10 mol% of Pt/C catalyst, the oxida-
tion of diol 1a resulted in 76% of dione 3a in toluene and
66% in acetonitrile–water mixture (1:1), the oxidation of
diol 1c resulted in dione 3c in 67% in water. It should be
noted that solubility of oxygen in these media is different
(8.7 mM in toluene and 8.1 mM in acetonitrile compared
to 1.3 mM in water at 20 °C12). We may suggest that the
amount of oxygen in water-containing solvents is not suf-
ficient for the reaction that slightly reduces the yield.
There is a slight difference in the reactivity of all-cis and
cis-diol-trans-alkyl compounds. In the case of 1d we ob-
served that cis-diol-trans-alkyl compounds react slower.
Figure 1 The effect of different amounts of LiOH·H2O on the iso-
lated yield of 3a. Reaction conditions: MeCN–H2O (1:1); 60 °C; 4 h;
5 mol% Pt/C catalyst.
Inorganic base additives to the oxidation system have
been recommended by Bäckvall for heterogeneous cata-
lytic dehydrogenations13 and Mueller et al. for aerobic ox-
idations.14 In our case the addition of alkali significantly
influenced the process by considerably increasing the re-
action rate. This enabled us to reduce the amount of cata-
lyst to 5 mol%. It is noteworthy that in the presence of
base hydroxyketone 2 was no longer detected among the
reaction products. Thus, in acetonitrile–water without al-
kali, the yields of 2a and 3a were 16% and 60%, respec-
tively, within 16 hours, while in the presence of one
equivalent of alkali the only reaction product was 3a in
70% yield within four hours. We may suggest that in the
presence of alkali the conversion of 2 into 3 is faster than
the conversion of 1 into 2. In the presence of base the pro-
cess was also less sensitive to the oxygen concentration.
A part of this effect can probably be caused by the com-
plex nature of the oxidation process, as discussed by
Steinoff and Stahl.12b By adding LiOH we achieved a sta-
ble process in acetonitrile–water when access of atmo-
spheric air was not restricted.
Table 1 Aerobic Oxidation of diols 1 to diones 3 in the Presence of
Pt/C Catalyst
Entrya
Substrate
1a
LiOH (equiv) Time (h)
Yield (%)
1
2b
3
0.2
0.4
0.6
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
4
61
67
69
70
68
49
74
28
76
69
0
1a
4
1a
4
4
1a
4
5c
6
1a
4
1b
5
7
1c
5
8
1d
1.3
4
9
1e
In order to establish the necessary amount of alkali, sub-
strate 1a was oxidized in a 1:1 mixture of acetonitrile–wa-
ter in the presence of different amounts of LiOH. The
obtained results are presented in Figure 1. We can note
that already starting from 0.5 equivalent of LiOH the
yields of the isolated product are close to maximum (ca.
70%).
10
11
1f
3.5
3
1g
a All experiments were run at 60 °C with 5 mol% Pt/C catalyst in an
open glass reactor equipped with a condenser. MeCN–H2O (1:1) used
as solvent unless stated otherwise.
b In toluene.
c Regenerated catalyst used in the experiment.
Using a reactor with unrestricted air access through an
open condenser, acetonitrile–water (1:1) as a solvent and (Table 1, entry 8); diol 1g, which bears an amido group,
LiOH as an additive, we performed the aerobic oxidation did not afford the expected dione 3g. At the same time
of alkyl, substituted alkyl, and aryl diols 1a–g15 on the Pt/ Boc-aminoalkyl substrate 1e resulted in the best isolated
C catalyst. The obtained results are presented in Table 1.16
yield of dione 3e (76%, Table 1, entry 9). In all these cases
no hydroxyketone intermediates 2 were observed.
In most cases 1,2-diones 317 were obtained in good yield
(around 70%). There are some exceptions: hydroxyalkyl When the catalyst was filtered from the reaction mixture
substrate with unprotected OH group 1b resulted in a and reused for the oxidation of diol 1a, only a minor de-
modest yield of 3b (49%, Table 1, entry 6). It is also note-
worthy that only the secondary OH groups of the substrate
were oxidized leaving the primary alcohol group un-
touched. The oxidation of tert-amylcarbonyloxy diol (1d)
proceeded quickly over about one hour, until a yield of 3d
of 28% was reached and then the reaction stopped
crease in the yield was observed and the product dione 3a
was isolated in 68% yield (Table 1, entry 5). Thus the cat-
alyst can be reused at least once without noticeable de-
crease in the catalyst activity and the TON for a batch
remains approximately 14.
Synlett 2008, No. 3, 347–350 © Thieme Stuttgart · New York

LETTER
Oxidation of Cyclopentane-1,2-diols to Cyclopentane-1,2-diones
349
(13) Bäckvall, J.-E. Modern Oxidation Methods; John Wiley and
Sons: New York, 2004, 87.
(14) Mueller, J. A.; Sigman, M. S. J. Am. Chem. Soc. 2003, 125,
7005.
We may conclude that a new, safe, and easy to use Pt/C
catalytic aerobic oxidation method for the oxidation of cy-
clopentane-1,2-diols to the corresponding 1,2-diones was
developed. The method is viable in the presence of a vari-
ety of functional groups, including benzyl ethers, alkyl-,
Boc-amino-, hydroxyl-, and phenyl groups. A wide choice
of solvents ranging from toluene to water–acetonitrile
mixture to water makes it possible to oxidize many other
substrates by this method.
(15) Preparation of Substrates
(a) Substrates 1a,b and 1d–f were prepared from the
corresponding alkenes according to the following
dihydroxylation procedure: Alkene was dissolved in a H2O–
t-BuOH mixture (1:3), and NMO (1.3 equiv) and fiber bound
OsO4 catalyst (0.1 mol%) were added. The reaction mixture
was stirred at 60 °C for an appropriate time (the reaction was
monitored by TLC), the catalyst filtered, rinsed with EtOAc,
and the filtrate quenched with an aqueous solution of
Na2S2O3 (10%). The aqueous layer was extracted with
EtOAc, the organic extracts combined, dried over MgSO4,
the solvent evaporated and the crude product purified by
flash chromatography, to afford the corresponding diol. Due
to the synthetic route always the cis-diol was obtained as two
isomers at the 3-position and used as a mixture. (b) Diol 1c
is a commercial product18 and was used without
purification. (c) Alkenes preceding diols 1a and 1b were
prepared from 2-cyclopentene-1-acetic acid.9a (d) The
alkene preceding diol 1d was prepared from 2-cyclopentene-
1-acetic acid ethyl ester by transesterification, as reported
by: Frei, U.; Kirchmayr, R. EP 0278914, 1988. (e) Alkenes
preceding diols 1e and 1g were prepared from 2-cyclo-
pentene-1-acetic acid according to: Bertrand, M. B.; Wolfe,
J. P. Tetrahedron 2005, 61, 6447. (f) The alkene preceding
diol 1f was prepared according to: Büchner, I. K.; Metz, P.
Tetrahedron Lett. 2001, 42, 5381.
Acknowledgment
We are grateful to the Estonian Ministry of Education and Research
(Grant No: 0142725s06), Estonian Science Foundation (Grant No:
5628 and 6778) and ProSyntest Ltd for support and Prof. Jan E.
Bäckvall for helpful suggestions.
References and Notes
(1) Blackburn, T. F.; Schwartz, J. J. Chem. Soc., Chem.
Commun. 1977, 157.
(2) (a) Nishimura, T.; Onoue, T.; Ohe, K.; Uemura, S. J. Org.
Chem. 1999, 64, 6750. (b) Hallmann, K.; Moberg, C. Adv.
Synth. Catal. 2001, 343, 260. (c) Schultz, M. J.; Park, C. C.;
Sigman, M. S. Chem. Commun. 2002, 3034. (d) Jensen, D.
R.; Schultz, M. J.; Mueller, J. A.; Sigman, M. S. Angew.
Chem. Int. Ed. 2003, 42, 3810. (e) Iwasava, T.; Tokunaga,
M.; Obora, Y.; Tsuji, Y. J. Am. Chem. Soc. 2004, 126, 6554.
(f) Schultz, M. J.; Hamilton, S. S.; Jensen, D. R.; Sigman, M.
S. J. Org. Chem. 2005, 70, 3343. (g) Steinhoff, B. A.; King,
A. E.; Stahl, S. S. J. Org. Chem. 2006, 71, 1861.
(3) (a) ten Brink, G.-J.; Arends, I. W. C. E.; Sheldon, R. A.
Science 2000, 287, 1636. (b) Buffin, B. P.; Clarkson, J. P.;
Belitz, N. L.; Kundu, A. J. Mol. Catal. A: Chem. 2005, 225,
111.
(4) (a) Jia, C.-G.; Jing, F.-Y.; Hu, W.-D.; Huang, M.-Y.; Jiang,
Y.-Y. J. Mol. Catal. 1994, 91, 139. (b) Stuchinskaya, T. L.;
Musawir, M.; Kozhevnikova, E. F.; Kozhevnikov, I. V.
J. Catal. 2005, 231, 41.
(5) (a) Karimi, B.; Abedi, S.; Clark, J. H.; Budarin, V. Angew.
Chem. Int. Ed. 2006, 45, 4776. (b) Yamada, Y. M. A.;
Arakawa, T.; Hocke, H.; Uozumi, Y. Angew. Chem. Int. Ed.
2007, 46, 704.
(16) General Procedure for the Catalytic Aerobic Oxidation
of Diols
Diol (0.424 mmol), catalyst (5 mol%), LiOH·H2O (1.0
equiv) and solvent [2 mL, MeCN–H2O (1:1)] were added to
a 10 mL glass reactor, equipped with a condenser and stirred
at 60 °C for an appropriate time. Consumption of the
substrate was monitored by TLC. When the substrate was
consumed the catalyst was filtered, rinsed with EtOAc (15
mL), EtOAc (10 mL) was added and the obtained two-phase
solution was washed with 0.025 M HCl aq soln (20 mL). The
separated aqueous layer was extracted once with EtOAc (20
mL). The combined extracts were dried over MgSO4 and
concentrated in vacuum. The solid crude product was
purified by flash chromatography [EtOAc–PE (2.5:10)] to
give the diketone as a white crystalline solid.
(17) All products have been fully characterized by 1H NMR and
13C NMR. The analyses of known compounds are in
agreement with published data. The characteristics of
compounds are as follows:
(6) (a) Kakiuchi, N.; Maeda, Y.; Nishimura, T.; Uemura, S. J.
Org. Chem. 2001, 66, 6620. (b) Yamaguchi, K.; Mizuno, N.
Chem. Eur. J. 2003, 9, 4353. (c) Karimi, B.; Zamani, A.;
Clark, J. H. Organometallics 2005, 24, 4695.
Compound 2a: 1H NMR (800 MHz, CDCl3): d = 7.48 (m, 4
H, Bn o-, m-), 7.43 (m, 1 H, Bn p-), 4.67 and 4.65 (2d,
J = 11.8 Hz, 2 H, Bn CH2O), 3.74 (dd, J = 1.8, 10.9 Hz, 1 H,
H-2), 3.69 (td, J = 2 × 5.0, 9.6 Hz, 1 H, H-7), 3.65 (ddd,
J = 4.5, 8.5, 9.6 Hz, 1 H, H-7), 2.41 (ddddd, J = 0.6, 1.4, 1.9,
9.2, 19.6 Hz, 1 H, H-5), 2.20 (dddd, J = 0.4, 9.6, 11.0, 19.6
Hz, 1 H, H-5), 2.09 (ddddd, J = 0.5, 1.4, 6.2, 9.6, 13.1 Hz, 1
H, H-4), 1.97 (m, 2 H, H-3,6), 1.86 (m, 1 H, H-6), 1.51
(dddd, J = 9.1, 11.0, 11.6, 13.1 Hz, 1 H, H-4). 13C NMR (125
MHz, CDCl3): d = 216.4 (C-1), 137.6 (C-9), 128.3 (C-11),
127.7 (C-10, C-12), 81.1 (C-2),73.1 (C-8), 68.9 (C-7), 42.5
(C-3), 34.2 (C-6), 34.0 (C-5), 23.3 (C-4). This structure was
confirmed by 2D FT correlation diagrams and 1H–1H
coupling constants from H-2 and H-5 (19.6 Hz geminal
coupling). The assignment of trans-configuration results
from the comparison of 13C chemical shifts with cis- and and
trans-isomers of 3-[2-(benzyloxy)ethyl]cyclopentane-cis-
1,2-diol.
(7) Steele, A. M.; Zhu, J.; Tsang, S. C. Catal. Lett. 2001, 73, 9.
(8) (a) Iwahama, T.; Sakaguchi, S.; Nishiyama, Y.; Ishii, Y.
Tetrahedron Lett. 1995, 36, 6923. (b) Iwahama, T.;
Yoshino, Y.; Keitoku, T.; Sakaguci, S.; Ishii, Y. J. Org.
Chem. 2000, 65, 6502.
(9) (a) Paju, A.; Kanger, T.; Pehk, T.; Müürisepp, A.-M.; Lopp,
M. Tetrahedron: Asymmetry 2002, 13, 2439. (b) Paju, A.;
Laos, M.; Jõgi, A.; Päri, M.; Jäälaid, R.; Pehk, T.; Kanger,
T.; Lopp, M. Tetrahedron Lett. 2006, 47, 4491.
(10) Paju, A.; Kanger, T.; Pehk, T.; Eek, M.; Lopp, M.
Tetrahedron 2004, 60, 9081.
(11) Johnson Matthey, 5% Platinum Charcoal Catalyst Type 160,
57.9% H2O.
(12) (a) Perry, R. H.; Green, D. W.; Maloney, J. O. Perry’s
Chemical Engineers’ Handbook, Seventh Edition; McGraw-
Hill: New York, 1997. (b) Steinhoff, B. A.; Stahl, S. S.
J. Am. Chem. Soc. 2006, 128, 4348.
Synlett 2008, No. 3, 347–350 © Thieme Stuttgart · New York

350
I. Reile et al.
LETTER
Compound 2a¢: 1H NMR (500 MHz, CDCl3): d = 7.28–7.34
(m, 5 H, Bn o-, m-, p-), 4.46 (s, 2 H, H-8), 4.01 (tdd,
J = 2 × 0.5, 8.3, 11.8 Hz, 1 H, H-5), 3.57 and 3.54 (m, 2 H,
H-7), 2.37 and 1.60 (m, 2 H, H-4), 2.30 (m, 1 H, H-2), 2.15
2), 138.61 (C-1), 84.24 [OC(Me)2], 35.42 (CH2CO), 33.36
(CH2CH3), 32.01 (C-4), 25.36 [OCMe2 and C-5], 8.09
(CH3CH2). IR: n = 3315, 2979, 2937, 2885, 1727, 1699,
1665, 1465, 1386, 1193, 1149 cm–1.
and 1.49 (m, 2 H, H-3), 2.02 and 1.75 (m, 2 H, H-6). 13
C
Compound 3e: 1H NMR [500 MHz, CDCl3, broadened
spectrum (E/Z exchange of Boc)]: d = 6.40 (br s, 1 H, OH),
4.89 (br s, 1 H, NH), 3.41 (br m, 2 H, H-7), 2.59 (t,
J = 2 × 6.6 Hz, 2 H, H-6), 2.47 (br m, 2 H, H-5), 2.41 (br m,
2 H, H-4), 1.41 (br s, 9 H, H-11). 13C NMR (125 MHz,
CDCl3): d = 203.21 (C-3), 155.96 (C-9), 149.57 (C-2),
144.18 (C-1), 79.33 (C-10), 37.82 (C-7), 31.90 (C-4), 29.88
(C-6), 28.32 (C-11), 25.51 (C-5). IR: n = 3371, 3326, 3008,
1689, 1657, 1524, 1451, 1393, 1367, 1249, 1169, 1119 cm–1.
Compound 3f: Ramage, R.; Griffiths, G. J.; Shutt, F. E.
J. Chem. Soc., Perkin Trans. 1 1984, 7, 1531.
NMR (125 MHz, CDCl3): d = 219.6 (C-1), 138.1 (C-9),
128.2 (C-11), 127.4 (C-10, C-12), 75.5 (C-5), 72.7 (C-8),
67.3 (C-7), 43.3 (C-2), 30.2 (C-6), 29.3 (C-4), 22.9 (C-3).
Large coupling constants of C-5 carbinol proton point to a
methylene group bonded to C-5.
Compound 3a: data available in ref. 9a. Compound 3b: data
available in ref. 9a. Compound 3c: data are in accordance
with commercial compound purchased from Aldrich.
Compound 3d: 1H NMR (500 MHz, CDCl3): d = 6.85 (s, 1
H, OH), 3.38 (s, 2 H, CH2CO), 2.53 (m, 2 H, H-5), 2.43 (m,
2 H, H-4), 1.75 (q, J = 7.3 Hz, 2 H, CH2CH3), 1.42 (s, 6 H,
(CH3)2, 0.86 (t, J = 7.3 Hz, 3 H, CH2CH3). 13C NMR (125
MHz, CDCl3): d = 203.16 (C-3), 168.80 (COO), 150.04 (C-
(18) 3-Methylcyclopentane-1,2-diol was purchased from Alfa
Aesar as a mixture of diastereomers, 95%.
Synlett 2008, No. 3, 347–350 © Thieme Stuttgart · New York

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