TEMPO-linked metalloporphyrins as efficient catalysts for selective oxidation of alcohols and sulfides

Article abstract of DOI:10.1016/j.tetlet.2006.06.039

Six new TEMPO-linked porphyrins and metalloporphyrins were synthesized and they exhibited efficient catalytic activity for selective oxidation of alcohols and sulfides to the corresponding aldehydes, ketones and sulfoxides using NaOCl as oxidant.

Full text of DOI:10.1016/j.tetlet.2006.06.039

Tetrahedron Letters 47 (2006) 5637–5640
TEMPO-linked metalloporphyrins as efficient catalysts
for selective oxidation of alcohols and sulfides
Jian-Ying Huang, Shi-Jun Li and Yan-Guang Wang*
Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China
Received 19 March 2006; revised 5 June 2006; accepted 6 June 2006
Available online 27 June 2006
Abstract—Six new TEMPO-linked porphyrins and metalloporphyrins were synthesized and they exhibited efficient catalytic activity
for selective oxidation of alcohols and sulfides to the corresponding aldehydes, ketones and sulfoxides using NaOCl as oxidant.
ꢀ
2006 Elsevier Ltd. All rights reserved.
The importance of metalloporphyrins as chemical
models of heme-containing enzymes and their use as
catalysts for selective and controlled oxidation reactions
and pyrrole (4 equiv) according to Lindesy method.19
Porphyrins 3a and 3b were hydrolyzed using NaOH to
give acids 4a and 4b, respectively. Esterification of acids
4 with 4-hydroxyl-TEMPO in the presence of DCC and
DMAP afforded the TEMPO-linked porphyrins 5a and
5b, which exhibit a three-line peak character of ESR
1
have prompted extensive studies of their reactions with
2
a variety of oxidants including hydroperoxides, mono-
3
4
5
peroxysulfate, iodosylbenzene, iodobenzene diacetate,
6
7
8
20
peracids, pyridine N-oxide, and hypochlorite. As
cytochrome P-450 mimics, simple Fe- or Mn–porphyrin
complexes were found to be good catalysts for transfer-
ring oxygen atoms from these oxidants with formation
spectra of nitroxyl. TEMPO-linked metalloporphyrins
2
0
6 and 7 were obtained by chelating 5 with FeCl and
2
2
1
MnCl according to the published method.
2
2
,9
of epoxides from alkenes, alcohols or ketones from
Initially, we evaluated the TEMPO-linked metallo-
porphyrins for their catalytic activity for epoxidation of
styrene using H O as oxidant. However, 6 and 7 were
3
,5,10
7a
alkanes,
from sulfides.
radicals, such as 2,2,6,6-tetramethyl-piperidyl-1-oxy
ketones from alcohols, and sulfoxides
8
b,11
On the other hand, stable nitroxyl
2
2
found to be unstable to oxidant and bleached within
10 min. Fortunately, we found that the TEMPO-linked
porphyrins and metalloporphyrins were stable in NaOCl
solution, and they could efficiently catalyze the selective
oxidization of alcohols and sulfides using NaOCl as
oxidant.
(
TEMPO), have been found to be another kind of effi-
1
2
13
14
17
cient oxidation catalysts to oxidize alcohols, diols,
sulfides, benzylic ethers, phosphines, naphthols,
and amines. Generally, TEMPO oxidation system is
similar to metalloporphyrin oxidation system because
they are suitable for the same oxidation substrates
and/or oxidants. As a part of our works on metallopor-
1
5
16
17
1
8
The oxidation of benzyl alcohol to benzaldehyde was
used as a model reaction (Table 1). The catalytic oxida-
tion system includes catalyst (1 mol %), KBr (10 mol %)
and aqueous NaOCl (l.25 equiv, pH 8.6). The catalysts
1
0a
phyrin-catalyzed oxidation reactions,
we are inter-
ested in the metalloporphyrin catalysts containing a
TEMPO moiety. For this reason, we synthesized several
TEMPO-attached porphyrins and metalloporphyrins,
and investigated their catalytic abilities to selectively
oxidize alcohols and sulfides using NaOCl as oxidant.
We report herein the results of this effort.
1
a
TEMPO, Mn(TDCPP)Cl, TEMPO-linked porphyrins
5a and 5b as well as TEMPO-linked metalloporphyrins
6a, 6b, 7a and 7b were examined. We found that in
the absence of the catalyst, the yield was rather poor
(
Table 1, entry 1). Catalysts 5–7 (Table 1, entries 4–9)
As shown in Scheme 1, porphyrins 3a and 3b were syn-
thesized from aromatic aldehydes 1 (1 equiv), 2 (3 equiv)
gave higher yields than TEMPO (Table 1, entry 2) and
Mn(TDCPP)Cl (Table 1, entry 3). The Mn complexes
7a and 7b exhibited better catalytic activity (Table 1, en-
*
Corresponding author. Tel./fax: +86 571 87951512; e-mail: orgwyg@
zju.edu.cn
tries 8 and 9) than the corresponding porphyrins 5a and
5b (Table 1, entries 4 and 5) and Fe complexes 6a and 6b
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.06.039

5638
J.-Y. Huang et al. / Tetrahedron Letters 47 (2006) 5637–5640
OCH2COOH
OCH2COOC2H5
CHO
4
N
R
R
R
R
R
R
H
1. BF3 Et2O
. DDQ
1. NaOH, THF
2. HCl
N
HN
N
N
HN
N
2
+
OCH2CO2C2H5
CHO
CH2Cl2, rt
rt
NH
1
NH
R
R
R
R
3
R
R
R
R
2
2
a: R = H
b: R = Cl
4
a: R = H
3
a: R = H, 38%
4
b: R = Cl
3
b: R = Cl, 20%
N
O
N O
HO
N
O
R
R
R
R
MCl2
N
HN
N
N
N
Cl
N
N
2
,6-lutidine
M
DCC, DMAP
CH2Cl2, rt
CHCl /CH OH
3
3
NH
rt
R
R
R
R
R
R
R
R
5
a: R = H, 90% from 3a
6a: R = H, M = Fe, 82%
6b: R = Cl, M = Fe, 56%
5
b: R = Cl, 66% from 3b
7
7
a: R = H, M = Mn, 81%
b: R = Cl, M = Mn, 77%
Scheme 1. Synthesis of TEMPO-linked porphyrins and metalloporphyrins.
a
Table 1. Catalyzed oxidation of benzyl alcohol with NaOCl
primary alcohols were oxidized to the corresponding
aldehydes (Table 2, entries 2–4) and secondary alcohols
were oxidized to the corresponding ketones (Table 2,
entries 1, 5 and 6). The yields are good to excellent
CH OH
CHO
2
Cat.
NaOCl, KBr,
CH Cl /H O
2
2
2
(87–99%). It is noteworthy that the silyl ether protecting
b
group (TBDMS) is stable under the reaction conditions
(Table 2, entry 6).
Entry
Catalyst
Yield (%)
Bleached time
of catalyst (min)
1
2
3
4
5
6
7
8
9
None
TEMPO
Mn(TDCPP)Cl
5a
5b
6a
6b
7a
7b
5
85
48
89
90
86
92
97
96
The selective oxidation of sulfide to sulfoxide was also
investigated. Glycosyl sulfide phenyl 4,6-O-benzyl-
idene-1-S-b-D-gluco-pyranoside (8), an important
synthetic intermediate containing one sulfide and two
hydroxyl groups, was used as substrate. The reaction
was performed with NaOCl, TEMPO-linked metallo-
>30
>30
>30
>30
>30
>30
>30
>30
porphyrins (1 mol %), KBr (10 mol %) and Bu NBr
4
(
5 mol %) in CH Cl /saturated aq NaHCO solution at
2 2 3
a
Benzyl alcohol (1 mmol) was oxidized by NaOCl (1.25 mmol, pH 8.6)
in the presence of TEMPO (1 mol %), porphyrins (1 mol %) or
0 ꢁC (Table 3). The sulfide 8 was oxidized to sulfoxide
with high selectivity even using excess of NaOCl
2.0 equiv) (Table 3, entries 1–4 and 6–8). The Fe com-
9
(
metalloporphyrins (1 mol %) and KBr (10 mol %) in CH
O = 1:1 (8 mL) at 0 ꢁC for 30 min.
Isolated yields.
2 2
Cl /
H
2
plexes 6a and 6b gave lower yields due to their instability
to oxidant (Table 3, entries 1 and 2), while the Mn com-
plexes 7a and 7b afforded the oxidation product 9 in
satisfactory yields (Table 3, entries 3 and 4). It is
noteworthy that the hydroxyl groups of substrate mole-
cule were not oxidized. In our oxidation system, TEM-
PO-linked metalloporphyrin 7b is more efficient than
b
(
Table 1, entries 6 and 7). The yields were almost quan-
titative when Mn complexes 7 were used (Table 1,
entries 8 and 9).
1
a
The oxidations of various alcohols were investigated
using the selected catalyst 7a. As shown in Table 2,
the published metalloporphyrin catalysts Mn(TPP)Cl,
Mn(TDCPP)Cl and TEMPO.
2
2

J.-Y. Huang et al. / Tetrahedron Letters 47 (2006) 5637–5640
5639
a
a
Table 2. 7a-Catalyzed oxidation of alcohols with NaOCl
Table 3. Catalyzed oxidation of sulfide 8 with NaOCl
Entry
Substrate
Product
Yield (%)
O
Ph
Ph
O
O
6 or 7
O
O
O
O
SPh
HO
HO
SPh
OH
O
NaOCl, KBr, Bu NBr
OH
4
OH
b
1
96
CH Cl /aq. NaHCO3
2
2
8
9
b
Entry Catalyst
Yield (%)
Bleached time of catalyst
c
2
3
PhCH
2
OH
OH
PhCHO
97
b
1
2
3
4
5
6
7
8
6a
6b
50
62
81
86
88
80
78
ꢀ20 min
ꢀ30 min
>30 min
>30 min
>30 min
>30 min
>30 min
>30 min
93
O
O
O
3
3
7a
7b
b
4
5
OH
OH
95
5
5
c
7b
TEMPO
Mn(TPP)Cl
b
99
Mn(TDCPP)Cl 84
HO
O
a
Compound 8 (0.5 mmol) was oxidized by NaOCl (1 mmol) in the
presence of metalloporphyrins (1 mol %), KBr (10 mol %) and
Bu NBr (5 mol %) in CH Cl /saturated aq NaHCO = 1:1 (10 mL)
4 2 2 3
c
6
87
at 0 ꢁC for 30 min.
Isolated yields.
Using 1.25 equiv NaOCl.
b
c
OTBDMS
Alcohol (1 mmol) was oxidized by NaOCl (1.25 mmol, pH 8.6) in the
presence of 7a (1 mol %) and KBr (10 mol %) in CH Cl /H O = 1:1
8 mL) at 0 ꢁC for 30 min.
OTBDMS
a
2
2
2
(
b
c
Yields were determined by GC analyses based on substrates used.
Isolated yields.
In conclusion, we have synthesized six new TEMPO-
linked porphyrins and metalloporphyrins, and found
that Mn complexes of TEMPO-linked porphyrins could
efficiently catalyze the selective oxidation of alcohols
and sulfides using NaOCl as oxidant. Using this proce-
dure, primary alcohols, secondary alcohols and sulfides
were oxidized to the corresponding aldehydes, ketones
and sulfoxides in high yields with excellent selectivity.
This type of catalysts is more efficient in comparison
with the conventionally used TEMPO, Mn(TPP)Cl
The generality of this protocol was examined by a vari-
2
3
ety of sulfides using 7b as catalyst. As shown in Table
, sulfides were oxidized to the corresponding sulfoxides
4
and no overoxidation to sulfone was observed on the
basis of TLC analysis. The yields are excellent (88–96%)
and the protective groups and hydroxyl groups remained
intact during the reactions (Table 4, entries 8 and 9).
a
Table 4. 7b-Catalyzed oxidation of sulfides with NaOCl
b
Entry
Substrate
Product
Yield (%)
93
O
S
1
PhSCH
3
Ph
CH3
O
S
2
3
4
5
6
7
p-TolSCH
3
89
95
92
96
95
94
p
-Tol
CH3
O
S
PhSEt
Ph
CH CH3
2
O
S
p-TolSCH
2
CH
3
p
-Tol
CH CH3
2
O
PhSPh
S
Ph
Ph
Ph
O
S
PhSTol-p
Tol-p
O
PhCH
2
SCH
2
Ph
Ph
S
Ph
O
O
Ph
Ph
Ph
O
O
O
O
8
9
S-Tol-p
O
S-Tol-p
91
HO
HO
OH
OH
O
O
O
HO
O
O
Ph
O
O
SPh
SPh
88
HO
OH
OH
a
Different sulfide (1 mmol) was oxidized by NaOCl (1.25 mmol, pH 8.6) in the presence of 7b (1 mol %), KBr (10 mol %) and Bu
CH Cl /saturated aq NaHCO = 1:1 (10 mL) at 0 ꢁC for 30 min.
Isolated yields.
4
NBr (5 mol %) in
2
2
3
b

5640
J.-Y. Huang et al. / Tetrahedron Letters 47 (2006) 5637–5640
and Mn(TDCPP)Cl, especially for the oxidation of
alcohols.
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04; (b) Siedlecka, R.; Skarzewski, J. Synlett 1996, 757–
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58.
1
6. (a) Miyazawa, T.; Endo, T. Tetrahedron Lett. 1986, 27,
395–3398; (b) Cho, N. S.; Park, C. H. J. Korean Chem.
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Acknowledgements
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This work was financially supported by the Specialized
Research Fund for Doctoral Program of Higher Educa-
tion, China (No. 20050335101), the Natural Science
Foundation of Zhejiang Province (No. R404109) as well
as the Teaching and Research Award Program for
Outstanding Young Teachers in Higher Education
Institutions of MOE, PR China.
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2
0. Spectral data for selected compounds. Compound 3a: H
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3
J = 7.2 Hz, 3H), 4.41 (dd, J = 7.2 Hz, 14.2 Hz, 2H), 4.91
(
(
s, 2H), 7.3 (d, J = 8.3 Hz, 2H), 7.73–7.77 (m, 9H), 8.13
dd, J = 2.2 Hz, 8.3 Hz, 2H), 8.21 (d, J = 5.1 Hz, 6H), 8.85
1
3
References and notes
(s, 8H); C NMR (125 MHz, CDCl ) d: 14.5, 61.8, 66.0,
3
1
13.2, 119.8, 120.4, 126.9, 127.9, 134.8, 135.8, 142.4, 158.0,
+ 1
1
2
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3
1997, 30, 251–259.
J = 7.1 Hz, 3H), 4.39 (dd, J = 7.1 Hz, 14.2 Hz, 2H), 4.90
(s, 2H), 7.27 (d, J = 8.5 Hz, 2H), 7.67–7.69 (m, 3H), 7.77
(d, J = 7.9 Hz, 6H), 8.12 (d, J = 8.5 Hz, 2H), 8.65 (d,
. (a) Bartoli, J.-F.; Barch, K. L.; Palacio, M.; Battioni, P.;
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1
3
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(125 MHz, CDCl ) d: 14.4, 61.7, 65.9, 113.1, 113.4, 114.3,
3
7
120.8, 127.8, 127.9, 130.6, 135.2, 135.6, 138.8, 138.9, 139.5,
+
3
4
5
139.8, 157.9, 169.1; MS (ESI) m/z: 923 ([M+H] ).
+
1
Compound 4a: MS (ESI) m/z: 689 ([M+H] ). Compound
+
4b: MS (ESI) m/z: 895 ([M+H] ). Compound 5a: HMRS
+
1
(ESI): Calcd for C55
843.3776; ESR (1 · 10
H
49
À4
N
5
O
mol L
4
([M+H] ) 843.3784, found
À1
in CHCl ): 3 lines,
g = 2.0059, A = 15.9 Gs. Compound 5b: HMRS (ESI):
3
4
0
N
+
Chem. 2004, 214, 95–101.
Calcd for C55
H43Cl
6
N
5
O
4
([M+H] ) 1047.1446, Found
6
7
8
. (a) Takata, T.; Ando, W. Tetrahedron Lett. 1983, 24,
1047.1452. Compound 6a: MS (ESI) m/z: 896.1
+
3631–3634; (b) Mohajer, D.; Tayebee, R.; Goudarziafshar,
([MÀCl] ). Compound 6b: MS (ESI) m/z: 1102.1
+
+
H. J. Chem. Res. (S) 1999, 168–169.
. (a) Nestler, O.; Severin, K. Org. Lett. 2001, 3, 3907–3909;
([MÀCl] ). Compound 7a: MS (ESI) m/z: 895 ([MÀCl] ).
+
Compound 7b: MS (ESI) m/z: 1101 ([MÀCl] ).
(
1
b) Zhang, J.-L.; Che, C.-M. Org. Lett. 2002, 4, 1911–
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22. General procedure for the catalytic oxidation of alcohols
to carbonyl derivatives. To a solution of alcohols (1 mmol)
in CH Cl (3 mL) was added the catalyst (1 mol %), KBr
(
b) Ramsden, J. H.; Drago, R. S.; Riley, R. J. Am. Chem.
2
2
Soc. 1989, 111, 3958–3961; (c) Collman, J. P.; Tanaka, H.;
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(10 mol %) and saturated NaHCO3 solution (2 mL).
0.35 M NaOCl solution (2.86 mL, pH 8.6) was added at
0 ꢁC and the mixture well stirred at the same temperature
for 30 min. The organic phase was separated, dried over
Na SO , and analyzed by GC or evaporated and then
3689–3690.
9
. Chan, W.-K.; Liu, P.; Yu, W.-Y.; Wong, M.-K.; Che,
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2
4
1
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purified by column chromatography on silica gel.
23. General procedure for the catalytic oxidation of sulfides to
sulfoxides. To a solution of sulfides (1 mmol) in CH Cl
8
Perkin Trans. 1998, 2, 2221–2226.
2
2
1
1
1
1. Baciocchi, E.; Gerini, M. F.; Lapi, A. J. Org. Chem. 2004,
(3 mL) was added the catalyst (1 mol %), Bu
(5 mol %), KBr (10 mol %) and saturated aq NaHCO
4
NBr
69, 3586–3589.
3
2. Adam, W.; Saha-M o¨ ller, C. R.; Ganeshpure, P. A. Chem.
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solution (2 mL). The mixture was cooled to 0 ꢁC and then
0.73 M NaOCl in saturated NaHCO solution (0.92 mL,
3
1.25 mmol) was added dropwise. The mixture was stirred
at 0 ꢁC for 30 min, and then the layers were separated. The
aqueous phase was extracts with CH Cl (3 · 3 mL) and
2
2
2002, 35, 774–781; (c) Liu, R.; Dong, C.; Liang, X.; Wang,
the combined organic extracts were washed with water,
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chromatography on silica gel. Compound 9: H NMR
2 4
1
(
e) Zhao, M. Z.; Li, J.; Mano, E.; Song, Z. G.; Tschaen, D.
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(500 MHz, CDCl ) d: 2.96 (s, 1H), 3.41–3.42 (m, 1H), 3.64
3
(t, J = 9.4 Hz, 1H), 3.75 (t, J = 10.3 Hz, 1H), 3.87 (t,
J = 9.6 Hz, 1H), 4.17 (d, J = 9.4 Hz, 1H), 4.24–4.28 (m,
2H), 4.31 (s, 1H), 5.55 (s, 1H), 7.35–7.37 (m, 3H), 7.46–
6
Recupero, F. Tetrahedron Lett. 2001, 42, 6651–6653; (g)
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1
3
4.47 (m, 2H), 7.57–7.58 (m, 3H), 7.70–7.72 (m, 2H);
NMR (125 MHz, CDCl ): d = 68.3, 71.0, 73.4, 74.4, 79.7,
93.8, 102.2, 124.8, 126.5, 128.6, 129.5, 129.6, 132.3, 136.9,
C
3
1
4. Anelli, P. L.; Banfi, S.; Montanari, F.; Quici, S. J. Org.
Chem. 1989, 54, 2970–2972.
+
+
141.6; MS (ESI) m/z: 399 ([M+Na] ), 775 ([2M+Na] ).