Ruthenium hydride catalyzed direct oxidation of alcohols to carboxylic acids via transfer hydrogenation: Styrene oxide as oxygen source

Article abstract of DOI:10.1055/s-0032-1317676

Direct oxidation of alcohols to carboxylic acids using styrene epoxide as oxidant in the presence of [RuHCl(CO)(PPh₃)₃] complex as catalyst is reported. By this catalytic system, a variety of primary alcohols including substituted benzyl alcohols as well as linear ones were directly converted into carboxylic acids in good to excellent yields. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0032-1317676

90▌
LETTER
lRettuer thenium Hydride Catalyzed Direct Oxidation of Alcohols to Carboxylic
Acids via Transfer Hydrogenation: Styrene Oxide as Oxygen Source
Synthesis of Carboxylic Acids by Styrene Oxide
Behjat Barati, Majid Moghadam,* Abbas Rahmati,* Shahram Tangestaninejad, Valiollah Mirkhani,
Iraj Mohammadpoor-Baltork
Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441, Iran
Fax +98(311)6689732; E-mail: moghadamm@sci.ui.ac.ir; E-mail: a.rahmati@sci.ui.ac.ir
Received: 07.09.2012; Accepted after revision: 30.10.2012
O
Abstract: Direct oxidation of alcohols to carboxylic acids using
O
styrene epoxide as oxidant in the presence of [RuHCl(CO)(PPh3)3]
complex as catalyst is reported. By this catalytic system, a variety
of primary alcohols including substituted benzyl alcohols as well as
linear ones were directly converted into carboxylic acids in good to
excellent yields.
R
OH
[RuHCl(CO)(PPh3)3]
toluene, 90 °C, 12 h
R
OH
+
+
Key words: ruthenium hydride complex, alcohols, carboxylic ac-
ids, epoxides, oxidation
Scheme 1
First, the reaction parameters were optimized in the reac-
tion of benzyl alcohol (1a) with styrene oxide (2a, Table
1). First, the effect of catalyst amount was studied in the
model reaction and 5 mol% of catalyst was chosen as op-
timal catalyst amount (Table 1, entry 2). Increasing the
amount of catalyst to 10 mol% did not affect the yield of
product, but decreasing the catalyst amount to 3 mol%,
the yield decreased to 53% (Table 1, entries 1–3). The ef-
fect of solvent was also checked in the model reaction.
Among toluene, dichloromethane, dioxane, 1,2-dichloro-
ethane, acetonitrile, and THF as solvents; toluene was
chosen as reaction medium because the highest yield was
obtained in this solvent (Table 1, entries 2 and 4–8). The
ability of other ruthenium catalysts such as
Transition-metal hydrides have recently attracted great at-
tention due to their high efficiency and tolerance to func-
tional-group transformation.1 In particular, ruthenium
hydride catalysts have played a large rule in these impor-
tant reactions.2 However, most of the examples are limited
to the reduction of polar functional groups3 and reductive
carbon–carbon bond formations.2,4
Carboxylic acids are key building blocks for the synthesis
of a variety of pharmaceutically important compounds5
and also have specific industrial applications for produc-
tion of several compounds.6 Transition-metal-catalytic
systems have been used for the oxidative dehydrogenation
of alcohols to their corresponding carboxylic acids which
represents one of the most fundamental transformations in
organic chemistry.7 Generally, the direct oxidation of al-
cohols to carboxylic acids is a two-step process; oxidation
of the alcohol to the (potentially sensitive) aldehyde and
oxidation of the resulting aldehyde to the desired carbox-
ylic acid. Despite recent progress in the direct conversion
of primary alcohols into carboxylic acids, the number of
methods available is still limited, and often harsh reaction
conditions with low functional-group compatibility have
to be employed.8 But to date, application of transition-
metal hydrides for oxidation of alcohols to carboxylic
acids have not been reported. Considering the importance
of this reaction and relying pronounced ability of rutheni-
um hydride complex to influence the reactivity of organic
compounds, we decided to explore the ability of
[RuHCl(CO)(PPh3)3]9 catalyst in the direct oxidation of
alcohols to carboxylic acids in the presence of styrene ox-
ide as oxygen source (Scheme 1).
[RuH2(CO)(PPh3)3],10
[Ru(O2CCF3)2(CO)(PPh3)2],11
[RuHCl(PPh3)3],12 [RuH2(PPh3)3],13 and [Ru(cod)(cot)]14
were also investigated, and no better results were obtained
in comparison with [RuHCl(CO)(PPh3)3] (Table 1, entries
9–13). It seems that the ease of selective substitution of
phosphine ligand trans to H– in cis,mer-
[RuHCl(CO)(PPh3)3] by alkoxy ligand (from epoxide)
provide clear evidence for the kinetic trans effect of the
strong σ-donor hydrido ligand.15 The carbon monoxide,
which acts as a weak σ-donor but a strong π-acceptor li-
gand, is ideal for tuning the electronic and steric proper-
ties of the Ru center in the reaction intermediates.16 The
presence of ligands, which increases the electron density
on the Ru, reduces the catalytic activity. In the case of
[Ru(cod)(cot)] both electronic and steric effects should be
considered.17 Finally, different epoxides were also applied
as oxygen source. The results showed that the best oxygen
source is styrene oxide (Table 1, entries 14–19). This can
be attributed to increased stability of styrene (as one of the
reaction products) relative to the other alkenes which were
produced upon oxidation reaction. On the other hand, no
progress was observed using H2O2 or tert-BuOOH as ox-
ygen source. The scope and generality of this method was
checked in the oxidation of a wide range of primary alco-
hols including benzylic and linear ones using styrene ox-
SYNLETT 2013, 24, 0090–0096
Advanced online publication: 05.12.2012
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0032-1317676; Art ID: ST-2012-B0752-L
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Carboxylic Acids by Styrene Oxide
91
Table 1 Optimization of Conditions for the Reaction of 1a with 2a
O
CH2OH
catalyst
solvent
OH
epoxide
+
1a
2
3a
Entry
1
Catalyst
Catalyst amount (mol%) Epoxide
Solvent
toluene
Yield (%)b
O
RuHCl(CO)(PPh3)3
10
85
2a
2
3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
RuH2(CO)(PPh3)3
Ru(O2CCF3)2(CO)(PPh3)2
RuHCl(PPh3)3
5
3
5
5
5
5
5
5
5
5
5
5
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
toluene
toluene
CH2Cl2
dioxane
DCE
83
53
30
45
38
25
5
4
5
6
7
MeCN
THF
8
9
toluene
toluene
toluene
toluene
toluene
55
35
19
29
33
10
11
12
13
RuH2(PPh3)4
Ru(cod)(cot)
O
14
15
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
5
5
toluene
toluene
47
30
2c
O
Cl
2d
2e
O
O
16
17
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
5
5
toluene
toluene
15
28
O
O
O
O
2f
18
19
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)3
5
5
toluene
toluene
17
60
2g
2h
O
a All reactions were performed using 1a (1 mmol), 2 (1.3 mmol), catalyst, and solvent (2 mL) for 12 h in a screw capped test tube at 90 °C.
b The yields refer to pure isolated products.
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 90–96

92
B. Barati et al.
LETTER
O
+
OH
R
3a
O
[Ru]-H
Ph
2
1H NMR (400 MHz, CDCl3)
1.56 (J = 3.2 Hz, d, 3H)
3.08 (J = 4.8 Hz, q, 1H)
[Ru]
CH3
[Ru]
H
O
O
CH2
Ph
[Ru]-
H
Ph
R
O
I
H
II
RCHO
4
H2
RCH2OH
1a
Scheme 2
ide as oxygen source (Table 2). Different benzyl alcohols Cl(CO)(PPh3)3] releases, and the catalytic cycle will con-
bearing electron-withdrawing and electron-donating sub- tinue (Scheme 2).
stituents were efficiently converted into their correspond-
Further investigations showed that, in addition to styrene,
ing substituted benzoic acids (Table 2, entries 1–5, 12, and
ethylbenzene is also present in the reaction mixture. This
13). It seems that the nature of the substituents has no sig-
can be attributed to the fact that the produced styrene acts
nificant effect on the product yield. Surprisingly, upon ox-
as a hydrogen accepter (Scheme 3).18
idation of 4-methoxybenzyl alcohol (1l), the 4-
hydroxybenzoic acid (3l) was obtained as product, and the
[Ru]–H
methyl ether was deprotected to its corresponding hy-
+
H2
droxy compound (Table 2, entry 13).
A series of substituted N-(2-hydroxyethyl)benzamides
were also oxidized to their corresponding carboxylic acids
in high to excellent yields with styrene oxide in the pres-
ence of [RuHCl(CO)(PPh3)3] (Table 2, entries 7–10). Cin-
namyl alcohol as a linear alcohol was also oxidized
successfully to cinnamic acid in high yield (Table 2, entry
11).
Scheme 3
On the other hand, excess styrene oxide was not detected
in the reaction mixture, but a small amount of 1-phenyl-
ethanol was. It seems that the styrene oxide can also act as
hydrogen acceptor (Scheme 4).
Despite the ability of this catalyst in the catalyzing the
Tishchenko reaction,2l no Tishchenko products were ob-
served in the presence of styrene oxide (even for com-
pound 1f).
OH
O
[Ru]–H
+
H2
Scheme 4
The plausible mechanism for this reaction is as following:
First, the [RuHCl(CO)(PPh3)3] reacts with styrene oxide
2, and a hydroruthenation reaction gives the ruthenium
complex I. The structure of complex I was confirmed by
1H NMR and 13C NMR spectroscopy. As mentioned pre-
viously, the alcohol 1 can be converted into aldehyde 4 by
[RuHCl(CO)(PPh3)3] and releases H2 gas.2k The resulting
complex I would undergo a nucleophilic reaction with al-
dehyde 4 to give the ruthenium complex II, which in turns
converts into styrene and carboxylic acid 3, the [RuH-
To stress this point, the oxidation of benzaldehyde with
styrene oxide was also investigated in the presence of
[RuHCl(CO)(PPh3)3]. The results showed that the benzoic
acid was obtained in 80% after eight hours, and styrene
was produced as byproduct. These observations show that
benzyl alcohol should be converted firstly into benz-
aldehyde and then converted into benzoic acid. All these
observations showed that the proposed mechanism is rea-
sonable.
Synlett 2013, 24, 90–96
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Carboxylic Acids by Styrene Oxide
93
Table 2 Ruthenium Hydride Catalyzed Direct Oxidation of Alcohols to Carboxylic Acids with Styrene Oxidea
Entry
1
Alcohol 1
Carboxylic acid 3
Yield (%)b
O
OH
OH
83
80
90
86
93
1a
1b
3a
O
OH
OH
2
3
4
5
3b
O
OH
OH
F
F
1c
3c
O
OH
OH
Cl
Cl
1d
3d
O
OH
OH
O2N
O2N
1e
3e
OH
O
OH
6
71
HO
HO
O
3f
1f
O
O
OH
OH
N
H
N
H
7
8
80
80
O
1g
1h
3g
O
O
OH
OH
N
N
H
H
O
3h
O
O
OH
OH
N
H
N
H
9
83
85
O
O2N
1i
O2N
3i
Cl
O
Cl
O
OH
OH
N
H
N
10
H
O
1j
3j
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 90–96

94
B. Barati et al.
LETTER
Table 2 Ruthenium Hydride Catalyzed Direct Oxidation of Alcohols to Carboxylic Acids with Styrene Oxidea (continued)
Entry
Alcohol 1
Carboxylic acid 3
Yield (%)b
O
OH
OH
OH
11
79
1k
3k
O
O
OH
OH
12
13
83
86
MeO
HO
1l
3l
OH
HO
HO
1m
3l
a All reactions were performed using alcohol (1 mmol), styrene epoxide (1.3 mmol), and catalyst (5 mol%) in toluene (2 mL) at 90 °C for 12 h.
b The yields refer to pure isolated products.
2-Chlorobenzoic Acid (3d)
In conclusion, in the present work an efficient and new
method for direct oxidation of alcohols to carboxylic acids
is reported. In the presence of [RuHCl(CO)(PPh3)3] com-
plex as catalyst different primary alcohols including sub-
stituted benzyl alcohols and also linear ones were directly
converted into carboxylic acids in good to excellent
yields.
White solid; yield 134.6 mg, 86%; mp 137–138 °C. 1H NMR (400
MHz, DMSO-d6): δ = 7.42–7.55 (m, 3 H), 7.79 (d, 2 H, J = 8 Hz),
13.44 (br s, 1 H). 13C NMR (100 MHz, DMSO-d6): δ = 127.21,
130.58, 130.76, 131.50, 132.56, 166.28.
4-Nitrobenzoic Acid (3e)
White solid; yield 155.4 mg, 93%; mp 237–239 °C. 1H NMR (400
MHz, DMSO-d6): δ = 8.27 (d, 2 H, J = 8 Hz), 8.38 (d, 2 H, J = 8
Hz), 12.92 (br s, 1 H). 13C NMR (100 MHz, DMSO-d6): δ = 183.4,
151.6, 133.9, 130.4, 124.7.
Typical Procedure for the Ruthenium Hydride Catalyzed Oxi-
dation of Benzyl Alcohol to Benzoic Acid
2,2′-Biphenyldicarboxylic Acid (3f)
White solid; yield 172.0 mg, 71%; mp 224–226 °C. IR (KBr): 3064,
2994, 2885, 2818, 2645, 2567, 1686, 1597, 1577, 1453, 1407, 1297,
Benzyl alcohol (1a, 108.1 mg, 1.0 mmol), styrene epoxide (2, 156.2
mg, 1.3 mmol), [RuHCl(CO)(PPh3)3] (50.9 mg, 0.052 mmol), and
toluene (2 mL) were mixed in a screw-capped test tube and purged
with argon and sealed. The mixture was stirred at 90 °C for 12 h. Af-
ter the reaction was completed, the solvent was removed under re-
duce pressure. The residue was purified by chromatography on
silica gel plate (PE–EtOAc, 6:1), and the pure compound 3a was ob-
tained as a white crystal after recrystallization from H2O–MeOH
(101.4 mg, 83%).
1273, 1136, 1049, 1105, 1049, 1003, 921, 796, 754, 703 cm–1. H
1
NMR (400 MHz, DMSO-d6): δ = 6.94–8.16 (m, 8 H), 12.47 (br s, 2
H). 13C NMR (100 MHz, DMSO-d6): δ = 126.9, 129.4, 130.3, 131.0,
142.9, 167.9. MS (EI): m/z (%) = 242 (19) [M+], 197 (100), 181
(28), 152 (46), 139 (13), 115 (18), 98 (6), 89 (3), 76 (11). Anal.
Calcd for C14H10O4: C, 69.42; H, 4.16; N, 5.78. Found: C, 69.23; H,
4.06; N, 5.68.
2-Benzamidoacetic Acid (3g)
Spectral Data
White solid; yield 143.3 mg, 80%; mp 185–188 °C. IR (KBr): 3343,
3075, 2938, 1742, 1602, 1556, 1490, 1416, 1395, 1336, 1317, 1305,
1-Benzoic Acid (3a)
Colorless crystals; yield 101.4 mg, 83%, mp 121–123 °C. 1H NMR
(400 MHz, DMSO-d6): δ = 7.51 (t, 2 H, J = 16 Hz), 7.63 (t, 1 H, J
= 8 Hz), 7.95 (d, 2 H, J = 4 Hz), 12.99 (br s, 1 H). 13C NMR (100
MHz, DMSO-d6): δ = 128.55, 129.23, 130.69, 132.58, 167.30.
1257, 1181, 1078, 999, 943, 849, 806, 723 cm–1. H NMR (400
1
MHz, DMSO-d6): δ = 3.95 (d, 2 H, J = 4 Hz), 7.49 (t, 2 H, J = 8 Hz),
7.55 (t, 2 H, J = 4 Hz), 7.89 (d, 1 H, J = 8 Hz), 8.87 (t, 1 H, J = 6
Hz), 12.64 (br s, 1 H). 13C NMR (100 MHz, DMSO-d6): δ = 41.2,
127.2, 128.2, 128.3, 131.4, 133.7, 166.4, 171.3. MS (EI): m/z (%) =
179 (10) [M+], 135 (82), 104 (100), 83 (67), 77 (95), 69 (74), 57
(82), 51 (87), 45 (82), 43 (81), 41 (74). Anal. Calcd for C9H9NO3:
C, 60.34; H, 5.06; N, 7.82. Found: C, 60.22; H, 4.96; N, 7.69.
4-Methylbenzoic Acid (3b)
White solid; yield 109.5 mg, 80%; mp 178–179 °C. 1H NMR (400
MHz, DMSO-d6): δ = 2.37 (s, 1 H), 7.31 (d, 2 H, J = 8 Hz), 7.84 (d,
2 H, J = 8 Hz), 12.82 (br s, 1 H). 13C NMR (100 MHz, DMSO-d6):
δ = 21.10, 127.96, 129.10, 129.30, 143.01, 167.29.
2-(4-Methylbenzamido)acetic Acid (3h)
White solid; yield 154.5 mg, 80%; mp 153–155 °C. IR (KBr): 3354,
2986, 1746, 1680, 1613, 1556, 1506, 1416, 1325, 1260, 1214, 1121,
1000, 833, 755 cm–1. 1H NMR (400 MHz, DMSO-d6): δ = 2.36 (s,
3 H), 3.91 (d, 2 H, J = 8 Hz), 7.29 (d, 2 H, J = 8 Hz), 7.78 (d, 2 H,
J = 8 Hz), 8.77 (t, 1 H, J = 4 Hz), 12.63 (s, 1 H). 13C NMR (100
MHz, DMSO-d6): δ = 20.93, 41.33, 127.2, 128.8, 131.0, 141.3,
166.3, 171.4. MS (EI): m/z (%) = 193 (1) [M+], 149 (37), 119 (100),
4-Fluorobenzoic Acid (3c)
1
White solid; yield 126.1, 90%; mp 182–184 °C. H NMR (400
MHz, DMSO-d6): δ = 7.33 (t, 2 H, J = 8 Hz), 7.99–8.03 (m, 2 H),
13.07 (br s, 1 H). 13C NMR (100 MHz, DMSO-d6): δ = 115.72,
127.26, 132.13, 163.61, 166.11.
Synlett 2013, 24, 90–96
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Carboxylic Acids by Styrene Oxide
95
91 (80), 65 (38). Anal. Calcd for C10H11NO3: C, 62.17; H, 5.74; N,
7.25. Found: C, 61.98; H, 5.63; N, 7.05.
References
(1) (a) Transition Metals for Organic Synthesis: Building
2-(4-Nitrobenzamido)acetic Acid (3i)
Blocks and Fine Chemicals; Vol. 1 and 2; Beller, M.; Bolm,
C., Eds.; Wiley-VCH: Weinheim, 1998. (b) Davies, S. G.
Organotransition Metal Chemistry: Application to Organic
Synthesis; Pergamon Press: Oxford, 1982, Chap. 6.
(2) (a) Michalak, M.; Wicha, J. Synlett 2005, 2277. (b) Doi, T.;
Fukuyama, T.; Minamino, S.; Husson, G.; Ryu, I. Chem.
Commun. 2006, 1875. (c) Krompiec, S.; Kuznik, N.; Urbala,
M.; He, R. J. Mol. Catal. A: Chem. 2006, 256, 17. (d) Doi,
T.; Fukuyama, T.; Horiguchi, J.; Okamura, T.; Ryu, I.
Synlett 2006, 721. (e) Doi, T.; Fukuyama, T.; Minamino, S.;
Ryu, I. Synlett 2006, 3013. (f) Arisawa, M.; Terada, Y.;
Takahashi, K.; Nakagawa, M.; Nishida, A. J. Org. Chem.
2006, 71, 4255. (g) Burling, S.; Paine, B. M.; Nama, D.;
Brown, V. S.; Mahon, M. F.; Prior, T. J.; Pregosin, P. S.;
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2007, 129, 1987. (h) Casey, C. P.; Clark, T. B.; Guzei, A. J.
Am. Chem. Soc. 2007, 129, 11821. (i) Fukuyama, T.; Doi,
T.; Minamino, S.; Omura, S.; Ryu, I. Angew. Chem. Int. Ed.
2007, 46, 5559. (j) Omura, S.; Fukuyama, T.; Horiguchi, J.;
Murakami, Y.; Ryu, I. J. Am. Chem. Soc. 2008, 130, 14094.
(k) Shibahara, F.; Bower, J. F.; Krische, M. J. J. Am. Chem.
Soc. 2008, 130, 6338. (l) Omura, S.; Fukuyama, T.;
Murakami, Y.; Okamoto, H.; Ryu, I. Chem. Commun. 2009,
6741.
Light brown solid; yield 186.1 mg, 83%; mp 152–154 °C. IR (KBr):
3316, 3110, 1706, 1641, 1601, 1541, 1425, 1351, 1297, 1231, 1108,
1013, 930, 874, 831, 801, 786, 716 cm–1. H NMR (400 MHz,
1
DMSO-d6): δ = 3.97 (d, 2 H, J = 8 Hz), 8.11 (d, 2 H, J = 8 Hz), 8.33
(d, 2 H, J = 8 Hz), 9.28 (t, 1 H, J = 5 Hz), 13.14 (br s, 1 H). 13C NMR
(100 MHz, DMSO-d6): δ = 41.3, 123.6, 128.8, 139.3, 149.1, 164.8,
170.9. MS (EI): m/z (%) = 224 (2) [M+], (179, 29), 150 (100), 120
(24), 104 (91), 92 (62), 50 (83). Anal. Calcd for C9H8N2O5: C,
48.22; H, 3.60; N, 12.50. Found: C, 48.12; H, 3.47; N, 12.27.
2-(2-Chlorobenzamido)acetic Acid (3j)
White solid; yield 181.6 mg, 85%; mp 158–162 °C. IR (KBr): 3289,
3082, 1721, 1626, 1597, 1596, 1553, 1469, 1437, 1402, 1350, 1321,
1259, 1230, 1173, 1052, 999, 947, 842, 760 cm–1. H NMR (400
1
MHz, DMSO-d6): δ = 3.92 (d, 2 H, J = 8 Hz), 7.40–7.49 (m, 3 H),
7.51 (t, 1 H, J = 4 Hz), 8.79 (t, 1 H, J = 4 Hz), 12.71 (br s, 1 H). 13
C
NMR (100 MHz, DMSO-d6): δ = 40.9, 127.0, 129.0, 129.9, 130.8,
132.6, 136.2, 166.6, 170.9. MS (EI): m/z (%) = 213 (1) [M+], 168
(34), 139 (100), 111 (47), 75 (38), 50 (17). Anal. Calcd for
C9H8NO3Cl: C, 50.60; H, 3.77; N, 6.56. Found: C, 50.45; H, 3.60;
N, 6.46.
Cinnamic Acid (3k)
White solid; yield 117.5 mg, 79%; mp 129–132 °C. 1H NMR (400
MHz, DMSO-d6): δ = 6.56 (d, 1 H, J = 8 Hz), 7.43–7.73 (m, 5 H),
7.90 (d, 1 H, J = 8 Hz), 11.61 (br s, 1 H). 13C NMR (100 MHz,
DMSO-d6): δ = 173.9, 147.16, 135.1, 130.9, 128.9, 128.3, 118.4.
(3) (a) Denichoux, A. I.; Fukuyama, T.; Doi, T.; Horiguchi, J.;
Ryu, I. Org. Lett. 2010, 12, 1. (b) Patman, R. L.; Williams,
V. M.; Bower, J. F.; Krische, M. J. Angew. Chem. Int. Ed.
2008, 47, 5220.
4-Hydroxybenzoic Acid (3l)
White solid; yield 114.6 mg, 83%; mp 210–214 °C. 1H NMR (400
MHz, DMSO-d6): δ = 6.93 (d, 2 H, J = 8.4 Hz), 7.77 (d, 2 H, J = 8.4
Hz), 9.79 (s, 1 H), 10.63 (br s, 1 H). 13C NMR (100 MHz, DMSO-
d6): δ = 115.8, 128.4, 132.1, 163.3, 191.0.
(4) (a) Wakamatsu, H.; Nishida, M.; Adachi, N.; Mori, M. J.
Org. Chem. 2000, 65, 3966. (b) Krompiec, S.; Pigulla, M.;
Szczepankiewicz, W.; Bieg, T.; Kuznik, N.; Leszczynska-
Sejda, K.; Kubicki, M.; Borowiak, T. Tetrahedron Lett.
2001, 42, 7095. (c) Kuznik, N.; Krompiec, S.; Bieg, T.; Baj,
S.; Skutil, K.; Chrobok, K. J. Organomet. Chem. 2003, 665,
167. (d) Shibahara, F.; Bower, J. F.; Krische, M. J. J. Am.
Chem. Soc. 2008, 130, 14120. (e) Ngai, M.-Y.; Skucas, E.;
Krische, M. J. Org. Lett. 2008, 10, 2705. (f) Smejkat, T.;
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Formation of Ruthenium Complex I:
{Ru[OCH(CH3)Ph]Cl(CO)(PPh3)2}
RuHCl(CO)(PPh3)3 (0.05 mmol) and CDCl3 (1 mL) were placed in
an NMR tube. The tube was purged with N2, capped with a rubber
septum, and heated at 90 °C for 10 min. After cooling to r.t., styrene
oxide (2a, 0.05 mmol) was added. The resulting mixture was heated
at 90 °C for 30 min. The formation of complex I was confirmed by
1H NMR and 13C NMR measurements. Recrystallization from
CHCl3 and hexane gave the ruthenium complex I.
White solid. IR (KBr): νCO = 1920 cm–1. H NMR (400 MHz,
1
CDCl3): δ = 1.56 (d, 3 H, J = 3.2 Hz), 3.08 (q, 1 H, J = 4.8 Hz), 7.38–
7.42 (m, 17 H), 7.51–7.55 (m, 6 H), 7.59–7.64 (m, 6 H), 7.73–7.76
(m, 6 H). 13C NMR (125 MHz, CDCl3): δ = 18.27, 51.09, 125.34,
127.71, 128.10, 129.97 [d, 3J(C–P) = 7 Hz], 130.42 [d, 4J(C–P) = 2
2
1
Hz], 131.84 [d, J(C–P) = 14 Hz], 134.42 [d, J(C–P) = 43 Hz],
207.17 (t, J = 9.5 Hz). 31P NMR (160 MHz, CDCl3): δ = 35.95,
38.96. Anal. Calcd for C45H39ClO2P2Ru: C, 66.70; H, 4.85. Found:
C, 66.47; H, 4.83.
Acknowledgment
The financial support of this work by the Research Council of The
University of Isfahan is acknowledged.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.SnoIufproig
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iotSrat
ungIifoop
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© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 90–96

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Synlett 2013, 24, 90–96
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