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Synthesis of water-soluble monotosylated ethylenediamines and their application in ruthenium and iridium-catalyzed transfer hydrogenation of aldehydes.

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Full Paper
Received: 18 March 2011
Revised: 1 June 2011
Accepted: 7 June 2011
Published online in Wiley Online Library: 2 November 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1824
Synthesis of water-soluble monotosylated
ethylenediamines and their application in
ruthenium and iridium-catalyzed transfer
hydrogenation of aldehydes
Zhongqiang Zhou*, Qiong Ma, Aiqing Zhang and Lamei Wu
Synthesis of novel water-soluble monotosylated ethylenediamines and their application in ruthenium and iridium-catalyzed
transfer hydrogenation of aldehydes are described. Various aldehydes, including electron-deficient and electron-rich variants,
were reduced with high conversions and chemoselectivity using sodium formate as a hydrogen source in neat water.
Copyright © 2011 John Wiley & Sons, Ltd.
Keywords: monotosylated ethylenediamine; transfer hydrogenation; water; aldehyde
856
Introduction
Results and Discussion
The reduction of carbonyl compounds to the corresponding alcohols is one of the most fundamental and useful reactions of importance in the pharmaceutical and chemical industries. Among the
different methodologies used to carry out this reaction, catalytic
transfer hydrogenation (CTH) with the aid of a stable hydrogen donor has emerged as the most viable. The use of a hydrogen donor
has some advantages over the use of highly flammable and explosive molecular hydrogen since it avoids the risks and constraints
associated with hydrogen gas as well as the necessity for pressure
vessels. Water is readily abundant, inexpensive, non-flammable
and perhaps the most environmentally benign solvent. Processes
using water as a reaction medium have recently attracted a great
deal of attention.[1,2] Aqueous-phase transfer hydrogenation has
been studied for more than two decades.[3–5] Joo and co-workers[6,7]
described the first example of transfer hydrogenation of aldehydes
catalyzed by a water-soluble ruthenium–phosphine catalyst in neat
water. A variety of related ligands and transition metal complex catalysts have been developed for aqueous-phase transfer hydrogenation of aldehydes.[8–20] Noyori and co-workers disclosed that
monotosylated 1,2-diamine-based Ru(Z6-arene) catalyst can offer
high catalytic activity in transfer hydrogenation of benzaldehyde
using 2-propanol as a hydrogen donor.[21] Xiao and co-workers
demonstrated that monotosylated 1,2-diamine ligands exert a remarkable accelerating effect on the iridium-catalyzed reduction of
a wide range of aldehydes by sodium formate in neat water.[22]
Recently, a novel amphiphilic copolymer-based iridium catalyst
(Ir-PTsEN) containing monotosylated 1,2-diamines ligand showed
a remarkable rate acceleration for the transfer hydrogenation of
aldehydes in water.[23] Water-soluble ligands play an important key
role for water-soluble organometallic catalysts.[24] In continuing our
efforts for developing water-soluble ligands,[25] we report here the
synthesis of novel water-soluble monotosylated ethylenediamine
ligands and their application in transfer hydrogenation of aldehydes
in neat water using sodium formate as the hydrogen source.
The route for the synthesis of water-soluble monotosylated ethylenediamines is illustrated in Scheme 1. According to the literature
procedures,[26] ethylenediamine was mono-Boc protected by
using di-tert-butyl dicarbonate. In the second step, sulfonylation
of the N-Boc-ethylenediamine with 4-nitrobenzenesulfonyl
chloride in the presence of triethylamine at room temperature for
20 h afforded 3 in 91% yield. Reduction of compound 3 with Pd/C
(5%) in methanol was accomplished at room temperature for
only 1 h to give almost pure product 4. The reaction of chloroacetyl
chloride with 4 in the presence of triethylamine provided monosulfonamide 5. Introduction of the triethylamine to 5 was achieved in
refluxing acetonitrile to give the quaternary salt 6a. Then, removal
of the Boc group of 6a by treatment with 4 M HCl in methanol solution provided a novel ionic ligand 7a in quantitative yield. The
ligands 7b and 7c were similarly prepared using tri-n-butylamine
and N,N-dimethyloctylamine in place of triethylamine, respectively.
All the ligands obtained are insoluble in less polar solvents, such as
diethyl ether, ethyl acetate and hexane, but highly soluble in water.
These properties suffice for practical applications in aqueous
catalysis.
The ligands 7 were first tested in the reduction of benzaldehyde
in aqueous solution using sodium formate as the hydrogen source.
The catalysts were generated in situ by reacting monotosylated
ethylenediamines with [RuCl2(p-cymene)]2 or [(C5Me5)IrCl2]2 in neat
water at 80 C for 1 h. With Ru-7a catalyst, the reaction proceeded
Appl. Organometal. Chem. 2011, 25, 856–861
* Correspondence to: Zhongqiang Zhou, Key Laboratory of Catalysis and
Materials Science of the State Ethnic Affairs Commission and Ministry of
Education, College of Chemistry and Materials Science, South-Central University
for Nationalities, Wuhan 430074, China. E-mail: zhou-zq@hotmail.com
Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs
Commission and Ministry of Education, College of Chemistry and Materials
Science, South-Central University for Nationalities, Wuhan 430074, China
Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis of water-soluble monotosylated ethylenediamines
Scheme 1. Synthesis of monotosylated ethylenediamines 7a 7b and 7c. Reagents and conditions: (a) (Boc)2O, CH2Cl2, rt; (b) 4-nitrobenzenesulfonyl
chloride, triethylamine, CH2Cl2; (c) Pd/C, HCOONH4, MeOH, rt; (d) ClCH2COCl, triethylamine, CH2Cl2; (e) tertiary amine, CH3CN, reflux; (f) HCl(g),
MeOH, 0 C.
Appl. Organometal. Chem. 2011, 25, 856–861
drops dramatically thereafter.[23] The search for new reusable
catalysts, which are active and stable in an aqueous medium, is
a significant challenge.
As the catalysts prepared from [(C5Me5)IrCl2]2 and ligand 7
showed higher catalytic activity, subsequently we explored the
scope of the transfer hydrogenation of aldehydes using the catalyst Ir-7b. The results on the transfer hydrogenation of aromatic
aldehydes with Ir-7b at S/C 5000:1 are shown in Table 2. As can
be seen from the table, most of the aldehydes tested, including
electron-deficient and electron-rich variants, were reduced in a
few hours with excellent conversion using sodium formate as a
hydrogen source in neat water. For example, the reductions of
4-methyl-, 4-methoxy-, 4-fluoro- and 4-bromobenzaldehyde with
the Ir-7b catalyst both achieved 100% conversion within 5 h
(Table 2, entries 2, 3, 5 and 10). The transfer hydrogenation of
aromatic aldehydes appeared to be moderately dominated by
the electronic effect. Electron-deficient aldehydes were reduced
rapidly to the corresponding alcohols with high conversion.
Electron-rich aldehyde was reduced more slowly but also with
high conversion (Table 2, entry 8). The aldehydes also showed
a moderate steric effect during the reduction reaction. For
example, the reduction reaction of 2,4-dichlorobenzaldehyde
takes longer to complete than 2-chlorobenzaldehyde (Table 2,
entries 4 and 6). The chemoselective reduction of a,b-unsaturated
aldehydes is synthetically important, both in the laboratory and in
industry. Reduction of these substrates can be performed using a
lower S/C ratio (1000:1; Table 2, entries 13–15). Remarkably high
chemoselectivity is observed for Ir-7b-catalyzed transfer hydrogenation of a,b-unsaturated aldehydes in water. As shown in Table 2,
a,b-unsaturated aldehydes were readily reduced with exclusive selectivity towards the carbonyl group. For instance, crotonaldehyde
was reduced in 0.33 h to furnish the crotonyl alcohol in an excellent conversion of 100% (Table 2, entry 15). This feature makes it
very appropriate for the production of a,b-unsaturated alcohols.
The first example of transfer hydrogenation of aldehydes catalyzed by transition metal in neat water was described by Joo and
co-workers,[6,7] who reported that unsaturated aldehydes can be
reduced under very mild conditions (30–80 C) with good yields
Copyright © 2011 John Wiley & Sons, Ltd.
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857
to give benzyl alcohol with 100% conversion in 3 h (Table 1, entry 1).
The reaction was found to be considerably influenced by the
ligand and catalyst precursor used. Indeed, a dramatic increase
in the reaction rate of benzaldehyde was observed when 7b
and 7c were used in place of 7a (Table 1, entries 4 and 6) or when
[RuCl2(p-cymene)]2 was substituted by [(C5Me5)IrCl2]2 (Table 1,
entries 8, 11 and 12). Subsequently, we examined the transfer
hydrogenation of benzaldehyde with sodium formate in water,
using metal complexes with no additional ligands (Table 1, entries
16 and 17). As shown in Table 1, monotosylated ethylenediamines exert a remarkable accelerating effect on the ruthenium
and iridium-catalyzed reduction of aldehydes by sodium formate
in neat water. The results also indicate that the reaction was slow
without water (Table 1, entry 18). This is probably due to poor
solubility of the ligand 7b and sodium formate in benzaldehyde.
From the standpoint of green chemistry it is highly desirable
that the catalyst can be recovered and reused. We also studied
the possibility of reutilization of the present catalytic system
using benzaldehyde as a substrate. An attractive feature of the
present catalytic system lies in the easy separation of product
by extraction due to the low solubility of Ru-7 and Ir-7 in ethyl
ether. For each cycle, the reduced products were exacted with
ethyl ether and the supernatant was removed, followed by the
addition of 1.0 equiv. formic acid and the substrate. The activity
of the catalysts shows a remarkable drop in the recycled application (Table 1, entries 2, 3, 5, 7, 9, 10 and 14). Although a remarkable drop in activity was observed, in the course of the recycling
experiments a very high conversion (100%) was obtained after
a prolonged time. In the reduction of benzaldehyde with Ir-7a
catalyst (Table 1, entry 8), we measured the leached iridium. Inductively coupled plasma spectroscopy (PerkinElmer Elan DRC-e
ICP-MS) analysis showed that 0.88 mol% of iridium had leached
into the ether phase. The decrease in catalytic activity is most
likely due to catalyst decomposition rather than its loss during
solvent extraction. The recycling data showed that Ru complexes
are slightly more stable than Ir complexes (Table 1, entries 1–3
and 8–10). The amphiphilic copolymer-based iridium catalyst
shows excellent activity in the first cycle, and the activity also
Z. Zhou et al.
Table 1. Transfer hydrogenation of benzaldehyde catalyzed by [RuCl2(p-cymene)]2/7 and [(C5Me5)IrCl2]2/7a
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Catalyst
S/C
Time (h)
Conversion (%)b
Ru-7a
Ru-7a
Ru-7a
Ru-7b
Ru-7b
Ru-7c
Ru-7c
Ir-7a
Ir-7a
Ir-7a
Ir-7a
Ir-7a
Ir-7b
Ir-7b
Ir-7b
Ir
Ir
Ir-7b
Ir-7c
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
2500
5000
1000
1000
5000
5000
5000
5000
5000
3
3(19)
3
1
2
1
3
0.17
0.17
0.17
0.5
1
0.17
3.5
0.67
0.67
0.67
0.67
0.67
100
44.5(100)c
3.9d
100
100e
100
100f
100
10.3g
1.4h
98.7
100
100
100i
100
0j
0k
20.0l
100
a
Reaction conditions: S/C = 1000, benzaldehyde (10 mmol), 7 (0.012 mmol), [RuCl2(p-cymene)]2 or [(C5Me5)IrCl2]2 (0.005 mmol), HCO2Na2H2O (50 mmol),
water (10 ml), 80 C, argon. S/C = 2500, benzaldehyde (10 mmol), 7a (0.0048 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (50 mmol), water (10 ml),
80 C, argon. S/C = 5000, benzaldehyde (20 mmol), 7 (0.0048 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (100 mmol), water (15 ml), 80 C, argon.
b
Determined by GC-MS analysis on a HP-5 ms column.
c
Second cycle of entry 1.
d
Third cycle of entry 1.
e
Second cycle of entry 4.
f
Second cycle of entry 6.
g
Second cycle of entry 8.
h
Third cycle of entry 8.
i
Second cycle of entry 13.
j
Benzaldehyde (20 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (100 mmol), water (15 ml), 80 C, argon.
k
Benzaldehyde (20 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (100 mmol), 80 C, argon.
l
Benzaldehyde (20 mmol), 7b (0.0048 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (100 mmol), 80 C, argon.
858
and excellent selectivities to the corresponding unsaturated
alcohols by hydrogen transfer from HCOONa/H2O with a watersoluble ruthenium–phosphine catalyst. Himeda et al. reported
the transfer reduction of benzaldehyde catalyzed by an iridium
catalyst with 4,4′-dihydroxy-2,2′-bipyridine (DHBP) in an aqueous
formate solution, when the highest turnover frequency of
8.1 104 h1 was obtained at 80 C.[18] Recently, Xiao and coworkers demonstrated that Ir–Ts(en) and Ir–CF3Ts(en) are highly
active and chemoselective catalysts for the aqueous-phase transfer hydrogenation of aldehydes. The catalytic reduction can be
carried out with S/C ratios as high as 5 104:1, the initial turnover
frequency being near 1.3 105 h1.[22] More recently, Li and coworkers reported that the amphiphilic polymer-based catalyst
Ir-PTsEN is likely the most efficient one for the transfer hydrogenation of aldehydes in water, and the highest turnover frequency
is up to 3.0 105 h1.[23] Herein, iridium–arene complexes containing water-soluble monotosylated ethylenediamine ligands
can be used as catalysts for transfer hydrogenation of aldehydes
in aqueous solution using sodium formate as hydrogen source,
with a turnover frequency up to 1 104 h1 obtained (Table 2,
entry 11). These iridium complex catalysts are partitioned in
aldehydes and aqueous phase, being more soluble in the latter.
The distribution of catalysts in the reaction does not favor the
high concentration of aldehyde around catalytic active sites.
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Water-soluble catalysts in an aqueous biphasic system exhibit
low efficiency due to the mass diffusion limitation of the hydrophobic substrate, which is often a major problem when using
water-soluble catalysts in aqueous biphasic systems.
Conclusions
In summary, novel water-soluble monotosylated ethylenediamines
were synthesized from ethylenediamine. This work shows that
ruthenium and iridium-catalyzed transfer hydrogen of aldehydes
can be efficiently performed in neat water with sodium formate
as a reductant using water-soluble monotosylated ethylenediamines containing quaternary ammonium groups as ligands. Work
is in progress to improve the recyclability of the catalytic system.
Experimental
General Methods
Melting points were determined on a melting point apparatus
and were uncorrected. IR spectra were recorded on a Nicolet
Nexus 470 FTIR spectrometer. 1H NMR spectra were recorded
Copyright © 2011 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 856–861
Synthesis of water-soluble monotosylated ethylenediamines
Table 2. Transfer hydrogenation of aldehydes catalyzed by [(C5Me5)
IrCl2]2/7ba
Entry
1
2
3
4
5
Aldehyde
S/C
Time (h)
Conversion (%)b
5000
0.67
100
5000
5000
5000
4.5
5
S/C
Time (h)
Conversion (%)b
11
5000
0.5
100
12
5000
11
22.9d
13c
1000
3
75.6d
14c
1000
3
89.1d
15c
1000
0.33
Entry
Aldehyde
100
100
2.5
5000
Table 2. (Continued)
1
100
100d
100
a
6
5000
16
7
5000
1.5
8
5000
9
99.9
100
84.6
Unless otherwise indicated, reaction conditions: aldehyde (20 mmol), 7b
(0.0048 mmol), [(C5Me5)IrCl2]2 (0.002 mmol), HCO2Na2H2O (100 mmol),
water (15 ml), 80 C, argon.
b
Determined by GC-MS analysis on a HP-5 ms column.
c
Reaction conditions: aldehyde (10 mmol), 7b (0.012 mmol), [(C5Me5)IrCl2]2
(0.005 mmol), HCO2Na2H2O (50 mmol), water (10 ml), 80 C, argon.
d
Product is the corresponding a,b-unsaturated alcohol.
on a Bruker Avance III 400 with tetramethylsilane as internal standard. Elemental analysis was performed using Flash EA 2000.
Reactions were monitored by thin-layer chromatography (TLC)
using pre-coated silica plates (silica gel for TLC, GF254, Qingdao
Haiyang Chemical Co., Ltd). The conversions were measured by
gas chromatography–mass spectrometry (GC-MS) on an Agilent
5973 N (HP-5 ms capillary column). The chemicals used in this
work were purchased from the Alfa Aesar, Acros and Sinopharm
Chemical Reagent Co., Ltd.
N-Boc-N′-(4-Nitrophenylsulfonyl)-Ethylenediamine (3)
9
5000
0.67
100
10
5000
1.5
100
Copyright © 2011 John Wiley & Sons, Ltd.
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859
Appl. Organometal. Chem. 2011, 25, 856–861
To a solution of N-Boc-ethylenediamine (1.92 g, 12.0 mmol) and
triethylamine (4 ml, 28.0 mmol) in CH2Cl2 (40 ml) cooled in an
ice bath was added dropwise 4-nitrobenzenesulfonyl chloride
(2.21 g, 10.0 mmol) in CH2Cl2 (20 ml). After the ice bath was
removed, the mixture was stirred at room temperature for 20 h.
The mixture was washed successively with water, 0.5 M citric acid
and water, and dried over anhydrous MgSO4. After concentration,
the crude product was purified by recrystallization from ethanol
to afford 3 as a white solid (3.14 g, 91.0%). M.p.157–158 C. IR
(KBr), n: 3378, 3277, 1680, 1528, 1343, 1272, 1158, 1093 cm1.
1
H NMR (DMSO-d6, 400 MHz): d 1.34 (s, 9H, CH3), 2.84 (s, 2H,
CH2), 2.97 (s, 2H, CH2), 6.77 (s, 1H, NH), 8.04 (s, 2H, ArH), 8.42
(d, J = 7.2, 2H, ArH). 13 C NMR (DMSO-d6, 100 MHz): d 28.59
Z. Zhou et al.
(CCH3), 40.62 (NHCH2), 42.71 (NHCH2), 78.25 (C(CH3)3), 125.04 (Ar–
C), 128.49 (Ar–C), 146.61 (Ar–C), 150.00 (Ar–C), 155.92 (C–O). Anal.
calc. for C13H19N3O6S: C, 45.21; H, 5.55; N, 12.17. Found: C, 45.18;
H, 5.67; N, 12.11.
N-Boc-N′-(4-Aminophenylsulfonyl)-Ethylenediamine (4)
To a suspension of Pd/C (5%, 1.14 g) in methanol (90 ml) were
added 3 (3.11 g, 9.0 mmol) and ammonium formate (2.83 g,
45.0 mmol). The mixture was stirred at room temperature for 1 h,
filtered and washed with methanol. After concentration, water
(10 ml) was added and the resulting solid was filtered, washed
with water, and dried to afford 4 as a white powder (2.57 g,
90.2%). M.p. 128–130 C. IR (KBr), n: 3378, 2976, 1693, 1633,
1598, 1515, 1310, 1151, 1092 cm1. 1H NMR (CDCl3, 400 MHz): d
1.45 (s, 9H, CH3), 3.04 (s, 2H, CH2), 3.24 (s, 2H, CH2), 4.17 (s, 2H,
NH2), 4.87 (s, 1H, NH), 4.91 (s, 1H, NH), 6.69 (d, J = 7.2, 2H, ArH),
7.64 (d, J = 7.2, 2H, ArH). 13 C NMR (CDCl3, 100 MHz): d 28.34
(CCH3), 40.26 (NHCH2), 43.52 (NHCH2), 79.82 (C(CH3)3), 114.12
(Ar–C), 127.89 (Ar–C), 129.21 (Ar–C), 150.54 (Ar–C), 156.43 (C–O).
Anal. calc. for C13H21N3O4S: C, 49.51; H, 6.71; N, 13.32. Found: C,
49.76; H, 6.85; N, 13.28.
N-Boc-N′-(4-Chloroacetylaminophenylsulfonyl)Ethylenediamine (5)
To a solution of 4 (1.57 g, 5.0 mmol) and triethylamine (0.9 ml,
6.5 mmol) in CH2Cl2 (50 ml) cooled in an ice bath was added
dropwise a solution of chloroacetyl chloride (0.5 ml, 6.6 mmol)
in CH2Cl2 (20 ml). At the end of the addition, the mixture was
stirred for a further 8 h at the same temperature, and then stirred
for 24 h at room temperature. The mixture was washed successively with 0.5 M citric acid, water, saturated sodium bicarbonate
and brine, and dried over anhydrous MgSO4. After concentration,
the product 5 was obtained as a pale yellow solid (1.85 g, 94.7%).
M.p. 138–140 C. IR (KBr), n: 3360, 3274, 2982, 1689, 1596, 1530,
1323, 1276, 1252, 1158, 1095 cm1. 1H NMR (CDCl3, 400 MHz): d
1.45 (s, 9H, CH3), 3.09 (s, 2H, CH2), 3.25 (s, 2H, CH2), 4.24 (s, 2H,
CH2Cl), 4.85 (s, 1H, NH), 5.27 (s, 1H, NH), 7.74 (d, J = 7.6, 2H, ArH),
7.87 (d, J = 7.2, 2H, ArH), 8.45 (s, 1H, NH). 13 C NMR (CDCl3,
100 MHz): d 28.35 (CCH3), 40.26 (NHCH2), 42.90 (NHCH2), 43.71
(CH2Cl), 79.99 (C(CH3)3), 119.96 (Ar–C), 128.30 (Ar–C), 135.49
(Ar–C), 140.74 (Ar–C), 156.64 (C–O), 164.52 (C–O). Anal. calc. for
C15H22ClN3O5S; C, 45.97; H, 5.66; N, 10.72. Found: C, 45.82;
H, 5.75; N, 10.68.
Preparation of 7a
860
A mixture of 5 (392 mg, 1.0 mmol), triethylamine (1 ml, 7.0 mmol)
and acetonitrile (6 ml) was stirred under reflux for 24 h. Solvent
and excess of triethylamine were removed under reduced pressure. The residue was purified by column chromatography on silica gel (AcOEt, methanol as eluents) to give the desired product
6a as a pale yellow solid. 4 M HCl methanol solution (1.5 ml) was
added to 6a at 0 C. After stirring for 2 h at 0 C, the mixture
was allowed to warm to room temperature and stirred for an
additional 6 h at room temperature. The solution was concentrated under reduced pressure to give 7a as a pale yellow solid
(293 mg, 68.3%, two steps). M.p. 50–52 C. IR (KBr), n: 3421,
1697, 1597, 1543, 1465, 1324, 1157, 1094, 1029, 842 cm1. 1H
NMR (D2O, 400 MHz): d 1.30 (t, J = 7.2, 9H, CH3), 3.09 (s, 2H,
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NH+3 CH2), 3.13 (s, 2H, NHCH2), 3.57 (d, J = 7.2, 6H, CH2), 4.14 (s,
2H, COCH2), 7.69 (d, J = 7.2, 2H, ArH), 7.85 (d, J = 7.2, 2H, ArH).
13
C NMR (D2O, 100 MHz): d 7.04 (CH3), 39.13 (NH+3 CH2), 39.88
(NHCH2), 54.73 (CH3CH2), 56.40 (COCH2), 121.40 (Ar–C), 128.70
(Ar–C), 133.86 (Ar–C), 140.96 (Ar–C), 163.11 (C–O). Anal. calc. for
C16H30Cl2N4O3S: C, 44.75; H, 7.04; N, 13.05. Found: C, 44.28; H,
7.36; N, 12.77.
Preparation of 7b
Compound 7b was prepared using the same procedure as 7a,
yield 58.8 % (two steps). M.p. 257–258 C. IR (KBr), n: 3435, 2966,
2876, 1697, 1598, 1596, 1545, 1465, 1328, 1156, 1095, 840,
771 cm1. 1H NMR (D2O, 400 MHz): d 0.85 (d, J = 5.6, 9H, CH3),
1.30 (d, J = 6.0, 6H, CH3CH2), 1.67 (s, 6H, CH3CH2CH2), 3.07 (s, 2H,
NH+3 CH2), 3.12 (s, 2H, NHCH2), 3.47 (d, J = 6.8, 6H, CH3CH2CH2CH2),
4.16 (s, 2H, COCH2), 7.66 (d, J = 8.0, 2H, ArH), 7.83 (d, J = 7.2, 2H,
ArH). 13 C NMR (D2O, 100 MHz): d 12.81 (CH3), 19.06 (CH3CH2),
23.45 (CH3CH2CH2), 39.13 (NH+3 CH2), 39.88 (NHCH2), 57.91
(CH3CH2CH2CH2), 60.10 (COCH2), 121.37 (Ar–C), 128.25 (Ar–C),
133.97 (Ar–C), 140.90 (Ar–C), 163.12 (C¼O). Anal. calc. for
C22H42Cl2N4O3S: C, 51.45; H, 8.24; N, 10.91. Found: C, 51.13; H,
8.44; N, 10.43.
Preparation of 7c
Compound 7c was prepared using the same procedure as 7a,
yield 68.9% (two steps). M.p. 78–80 C. IR (KBr), n: 3421, 2929,
2859, 1700, 1597, 1544, 1469, 1326, 1158, 1095, 1026, 843,
769 cm1. 1H NMR (D2O, 400 MHz): d 0.71 (s, 3H, CH3), 0.78
(s, 2H, CH2), 1.11–1.24 (m, 6H, 3CH2), 1.62 (s, 2H, CH2), 1.74
(s, 2H, CH2), 2.78 (s, 6H, CH3), 3.01-3.07 (m, 2H, NH+3 CH2), 3.11
(s, 2H, NHCH2), 3.51 (d, J = 6.0, 2H, N+CH2), 4.21 (s, 2H, COCH2),
7.69 (d, J = 8.4, 2H, ArH), 7.83 (d, J = 7.2, 2H, ArH). 13 C NMR (D2O,
100 MHz): d 14.1 (CH2CH3), 21.93 (CH2), 23.85 (CH2), 25.47 (CH2),
27.98 (CH2), 31.03 (CH2), 39.13 (NH+3 CH2), 39.87 (NHCH2), 52.51
(N+CH3), 62.37 (N+CH2), 65.54 (COCH2), 121.35 (Ar–C), 128.28
(Ar–C), 133.97 (Ar–C), 141.03 (Ar–C), 163.06 (C¼O). Anal. calc. for
C20H38Cl2N4O3S: C, 49.48; H, 7.89; N, 11.54. Found: C, 49.28; H,
8.13; N, 11.37.
General Procedure for Transfer Hydrogenation
7 (0.012 mmol) and [RuCl2(p-cymene)]2 (3.1 mg, 0.005 mmol) were
dissolved in degassed water (10 ml). The resulting solution was
stirred at 80 C for 1 h under an argon atmosphere. HCO2Na2H2O
(5.2 g, 50.0 mmol) and benzaldehyde (10.0 mmol) were then introduced. The mixture was stirred at 80 C for a certain period of
time. After cooling to room temperature, the organic compounds
were extracted with ethyl ether (4 5 ml) using a syringe. The
conversions (based on the amounts of unreacted substrate and
product formed) were determined by GC-MS analysis with an
HP-5 capillary column.
Recycle Experiment for the Transfer Hydrogenation of
Benzaldehyde in Water
7 (0.012 mmol), [RuCl2(p-cymene)]2 or [(C5Me5)IrCl2]2 (0.005 mmol)
was dissolved in degassed water (10 mL). The resulting solution
was stirred at 80 C for 1 h under an argon atmosphere. HCO2Na
2H2O (5.2 g, 50.0 mmol) and benzaldehyde (10.0 mmol) were
then introduced. The mixture was stirred at 80 C for a certain
Copyright © 2011 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 856–861
Synthesis of water-soluble monotosylated ethylenediamines
period of time. After cooling to room temperature, the organic
compounds were extracted with ethyl ether (4 5 mL) using a
syringe. The residual aqueous phase containing the catalyst was
reused by adding formic acid (0. 39 ml, 10.0 mmol) to regenerate
sodium formate and then benzaldehyde (1.06 g, 10.0 mmol) was
added to the aqueous solution for a new reaction cycle, and the
second cycle of the reaction was started under the same conditions. Unreacted substrate and product in the ethyl ether phase
were determined by GC-MS analysis with an HP-5 capillary column.
Acknowledgments
Financial support of this work by the Natural Science Foundation
of Hubei Province (2007ABA291, 2008CDA067) is gratefully
acknowledged.
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aldehyde, ethylenediamine, water, synthesis, application, transfer, iridium, soluble, hydrogenation, ruthenium, monotosylated, catalyzed
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