Rearrangement of aldoximes to amides in water under air atmosphere catalyzed by water-soluble iridium complex [Cp*Ir(H2O) 3][OTf]2

Article abstract of DOI:10.1039/c3cy00934c

In the presence of the water-soluble iridium complex [Cp*Ir(H ₂O)₃][OTf]₂, a variety of aldoximes, including aromatic, aliphatic, conjugated unsaturated and non-conjugated unsaturated, were converted into their corresponding amides in water with good to excellent yields. Further, the one-pot synthesis of amides from aldehydes, hydroxylamine hydrochloride and sodium carbonate via a tandem condensation-rearrangement reaction in water was also accomplished. Compared with the reported organometallic catalysts for the rearrangement of aldoximes to amides in water, the present catalyst exhibited some advantages such as being phosphorus ligand-free, having low catalyst loading, and operational convenience under air atmosphere. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c3cy00934c

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Rearrangement of aldoximes to amides in water
under air atmosphere catalyzed by water-soluble
iridium complex [Cp*Ir(H2O)3][OTf]2†
Cite this: Catal. Sci. Technol., 2014,
4, 988
*
Chunlou Sun, Panpan Qu and Feng Li
In the presence of the water-soluble iridium complex [Cp*Ir(H2O)3][OTf]2, a variety of aldoximes, including
aromatic, aliphatic, conjugated unsaturated and non-conjugated unsaturated, were converted into their
corresponding amides in water with good to excellent yields. Further, the one-pot synthesis of amides from
aldehydes, hydroxylamine hydrochloride and sodium carbonate via a tandem condensation–rearrangement
reaction in water was also accomplished. Compared with the reported organometallic catalysts for
the rearrangement of aldoximes to amides in water, the present catalyst exhibited some advantages
such as being phosphorus ligand-free, having low catalyst loading, and operational convenience under
air atmosphere.
Received 15th November 2013,
Accepted 9th December 2013
DOI: 10.1039/c3cy00934c
www.rsc.org/catalysis
procedure required a high reaction temperature (160 °C).
Very recently, Cadierno and co-workers demonstrated the
Introduction
Amides are one of the most important functional groups of
proteins, and are also widely utilized as key intermediates in
the construction of numerous fine chemicals, natural products,
peptides and polymers.1 Typically, amides are synthesized by
reactions of activated carboxylic acid derivatives, such as acid
chlorides, anhydrides and esters, with amines.2 However, these
procedures suffer from the use of toxic and expensive reagents,
low tolerance to sensitive functional groups and the generation
of a large amount of harmful by-products. As a result of this, in
2005 the American Chemical Society Green Chemistry Institute
(comprising members from major pharmaceutical industries
worldwide) voted ‘amide formation avoiding poor atom economy
reagents’ as the top challenge for organic chemistry.3
The rearrangement of aldoximes to amides presents a
complete atom-economical transformation and is accom-
plished using a variety of transition metal catalysts, such as
Rh,4 Ru,5 Ir,6 Au,7 Pd,8 Cu,9 Zn10 and In10b as complexes or
salts (Scheme 1). However, these procedures have to be
performed in organic solvents such as toluene. In recent years,
much attention has been paid to the development of organic
synthesis in water because water is cheap, safe and environ-
mentally benign compared with traditional organic solvents. In
2007, Mizuno and co-workers reported the first example of the
rearrangement of aldoximes to amides in water catalyzed
by heterogeneous Rh(OH)x/Al2O3 (4 mol%).11 However, this
transformation of aldoximes to amides in water under a
nitrogen atmosphere catalyzed by homogeneous ruthenium
complexes bearing water-soluble tris(dimethylamino)phosphine
or tris(5-(2-aminothiazolyl))phosphine trihydrochloride as
ligands (3–5 mol%).12 From the standpoint of sustainable
chemistry, the development of a new organometallic catalyst
bearing non-phosphorus ligands with low catalyst loading for
the rearrangement of aldoximes to amides in water under air
atmosphere is highly desirable.
We have reported
a transition metal-catalyzed regio-
selective N-alkylation with alcohols for the preparation of
2-(N-alkylamino)azoles,13a–d 2-(N-alkylamino)quinazolines,13e
N,N′-alkylarylureas and N,N′-dialkylureas.13f We have also demon-
strated the direct synthesis of N-alkylated amides from aldoximes
and alcohols via a tandem rearrangement–N-alkylation reaction
catalyzed by a Ru/Ir dual catalyst system,14 Ir-catalyzed direct
coupling of indoles with methanol to 3,3′-bisindoles (3,3′-BIM's)15
and the N-alkylation of sulfonamides with alcohols in water
catalyzed by water-soluble [Cp*Ir(6,6′-(OH)2bpy)(H2O)][OTf ]2.16
As part of a continuing interest in developing iridium-catalyzed
reactions, herein we wish to describe our efforts towards the
rearrangement of aldoximes to amides in water under air atmo-
sphere catalyzed by a water-soluble iridium complex. Further,
the reaction mechanism was also investigated.
Key Laboratory for Soft Chemistry and Functional Materials, Ministry of Education,
Nanjing University of Science and Technology, Nanjing 210094, PR China.
E-mail: fengli@njust.edu.cn; Fax: +86 25 84431939; Tel: +86 25 84317316
† Electronic supplementary information (ESI) available: Copies of the 1H NMR
and 13C NMR spectra for all products. See DOI: 10.1039/c3cy00934c
Scheme
to amides.
1
Transition metal-catalyzed rearrangement of aldoximes
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Table 2 Reactions of a variety of aromatic and aliphatic aldoximes
1 to amides 2a
Results and discussion
Initially, the rearrangement of benzaldoxime 1a was
chosen as a model in order to explore the feasibility of
the reaction. A range of water-soluble Cp*Ir complexes (Cp* =
η5-pentamethylcyclopentadienyl) (2 mol%) were assayed
for their ability to catalyze this model reaction, including
cationic [Cp*Ir(bpy)Cl]Cl (bpy = 2,2′-bipyridine) (cat.1)17
a
Entry
1
Aldoxime
Amide
Yieldb (%)
Cp*Ir complex bearing ammonia ligands [Cp*Ir(NH3)3][Cl]2
(cat.2),18 a Cp*Ir complex bearing one or more aqua ligands
[Cp*Ir(bpy)(H2O)][OTf ]2 (cat.3)19 and [Cp*Ir(H2O)3][OTf ]2
(cat.4).20 In the presence of cat.1 and cat.3, reactions of 1a
(0.5 mmol) were carried out in water (1 ml) at 110 °C for 12 h
and no conversion was observed (Table 1, entry 1 and entry 3).
Using cat.2 as the catalyst, the product 2a was obtained in a
12% yield (Table 1, entry 2). To our delight, cat.4 exhibited
excellent reactivity for this rearrangement and this reaction
afforded the product 2a in a 90% yield (Table 1, entry 4). The
analogous complexes cat.5 and cat.6 bearing BF4 and PF6
as counteranions exhibited relatively low catalytic activities
(Table 1, entries 5–6). When the catalyst loading of cat.4 was
reduced to 1.5 mol%, the product 2a could be obtained with
an 89% yield (Table 1, entry 7). Attempts to further reduce
the catalyst loading resulted in a low yield (Table 1, entry 8).
With the optimal reaction conditions in hand (Table 1,
entry 7), the rearrangement of a variety of aromatic and
aliphatic aldoximes was examined and the results are
summarized in Table 2. The reactions of benzaldoximes bear-
ing one or two electron-donating groups, such as methyl 1b,
isopropyl 1c, tert-butyl 1d, methoxy 1e and dimethoxy 1f,
afforded the corresponding products 2b–f with 82–93%
yields (Table 2, entries 1–5). Similarly, transformations of
93
1b
1c
1d
1e
1f
2b
2c
2d
2e
2f
2
92
83
82c
92
83
95
88
93
81
3
4
5
6
Table 1 Rearrangement of benzaldoxime 1a to benzamide 2aa
1g
1h
1i
2g
2h
2i
7
Entry
Cat.
X
Yieldb (%)
1
2
3
4
5
6
7
8
Cat.1
Cat.2
Cat.3
Cat.4
Cat.5
Cat.6
Cat.4
Cat.4
2.0
2.0
2.0
2.0
2.0
2.0
1.5
1.0
0
12
0
90
83
60
89
76
8
9
1j
2j
10
a
Reaction conditions: 1a (0.5 mmol), catal. (X mol%), water (1 ml),
b
1k
2k
110 °C, 12 h. Isolated yield.
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Table 2 (continued)
benzaldoximes bearing one or two halide atoms, such as fluoro
1g–h, chloro 1i–j, dichloro 1k and bromo 1l–m, gave
the desired products 2g–m with 80–95% yields (Table 2,
entries 6–12). The benzaldoximes bearing a strong electron-
withdrawing group, such as nitro 1n–o, trifluoromethyl 1p and
trifluoromethoxy 1q, were also proven to be suitable substrates,
and their corresponding products 2n–q were obtained with
82–86% yields (Table 2, entries 13–16). Furthermore, high
catalytic activities were also found in reactions of 2-naphthaldoxime
1r and thiophene-2-aldoxime 1s (Table 2, entries 17–18). In
the case of aliphatic aldoximes, including 2-pentanaldoxime 1t,
3-phenylpropanaldoxime 1u, butylaldoxime 1v and hexanaldoxime
1w, the desired products 2t–w could be obtained with 78–92%
yields (Table 2, entries 19–22).
To expand further the scope of the reaction, a series of
unsaturated aldoximes were investigated. As shown in Table 3,
α,β-unsaturated cinnamaldoxime 3a was converted into the
corresponding product 4a with 85% yield (Table 3, entry 1).
Reactions of cinnamaldoximes bearing an electron-donating
group 3b or strong electron-withdrawing group 3c afforded
the desired products 4b and 4c with 80% and 90% yields,
respectively (Table 3, entries 2–3). When the cinnamaldoximes
Entry
Aldoxime
Amide
Yieldb (%)
80
11
1l
2l
12
13
90
1m
1n
2m
82c
2n
2o
14
86
1o
15
16
84
Table
3
Reactions of a variety of unsaturated aldoximes 3 to
amides 4a
1p
1q
2p
2q
83d
Entry
1
Aldoxime
Amide
Yieldb (%)
17
18
19
80d
90
92
82
85
1r
1s
1t
2r
2s
2t
3a
4a
2
3
4
5
80
90
81
86
3b
3c
3d
3e
4b
4d
4d
4e
20
21
1u
1v
2u
2v
80
78
22
1w
2w
a
Reaction conditions: 1a (0.5 mmol), cat.4 (1.5 mol%), water (1 ml),
110 °C, 12 h. Isolated yield. c 120 °C. Cat.4 (2.5 mol%).
b
d
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Table 3 (continued)
no conversion was observed [eqn (1)]. With the aid of
butylaldoxime 1v, the hydration of 8 proceeded for 12 h
under the same conditions to give benzamide 2a with an
80% yield [eqn (2)]. Therefore, the rearrangement of
aldoximes to amides in water catalyzed by the water-soluble
iridium complex [Cp*Ir(H2O)3][OTf ]2 is in accord with the
secondary mechanism.
Entry
Aldoxime
Amide
Yieldb (%)
80c
6
3f
4f
7
77c
82c
3g
4g
8
3h
4h
a
Reaction conditions: 3 (0.5 mmol), cat.4 (1.5 mol%), water (1 ml),
120 °C, 12 h. Isolated yield. c Cat.4 (2.5 mol%).
b
Table 4 One-pot synthesis of amides from aldehydes, hydroxylamine
hydrochloride and sodium carbonatea
bearing a halide atom 3d and 3e were used as substrates, the
corresponding products 4d and 4e were obtained with 81%
and 86% yields, respectively (Table 3, entries 4–5). The
rearrangement was also applied to 3-(furan-2-yl)acrylamide 3f,
affording the desired product 4f with 80% yield (Table 3, entry 6).
Furthermore, the non-conjugated unsaturated aldoximes 3g
and 3h were examined and the desired products 4g and 4h
were obtained with 77% and 82% yields, respectively (Table 3,
entries 7–8).
Entry
1
Aldehyde
Amide
Yieldb (%)
85
The one-pot synthesis of amides from aldehydes, hydroxyl-
amine hydrochloride and sodium carbonate via a tandem
condensation–rearrangement reaction in water was also
investigated.21 As shown in Table 4, in the presence of cat.4,
reactions of a variety of aldehydes, including aromatic and
aliphatic aldehydes 5 and unsaturated aldehydes 6, afforded
the desired products 2 and 4 with 71–86% yields.
Two different reaction mechanisms for the transition
metal-catalyzed rearrangement of aldoximes to amides
have been proposed.22 The first mechanism involves the
metal-promoted dehydration of aldoximes into metal–nitrile
species, which are subsequently hydrated by water released in
the previous step to give amides (Scheme 2, left). In the
secondary mechanism, the metal–nitrile species, generated
in the initial dehydration of aldoximes, are attacked by
another coordinated aldoxime to give a five-membered cyclic
species, which decomposes to release amides with the regener-
ation of the metal coordinated nitrile as the catalytic species
(Scheme 2, right).
5j
2j
2
3
4
5
80
5k
5t
2k
2t
86
71
5w
2w
83c
80d
6a
4a
To obtain information about the mechanism for this
present reaction, several experiments were undertaken. The
process of the rearrangement of benzaldoxime 1a to benzamide
6
4h
6h
1
2a (Table 1, entry 7) was monitored by H NMR spectroscopy
a
Reaction conditions: 5 or 6 (0.5 mmol), 7 (1 equiv.), Na2CO3
(0.5 equiv.), water (1 ml), rt, 0.5 h. Then, cat.4 (1.5 mol%) was added
into the reactor, 110 °C, 12 h. Isolated yield. Cat.4 (1.5 mol%),
120 °C. d Cat.4 (2.5 mol%), 120 °C.
and no benzonitrile as a by-product was detected. Further,
in the presence of cat.4 (1.5 mol%), the reaction of
benzonitrile 8 was carried out in water at 110 °C for 12 h and
b
c
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were recorded at 125 MHz using a Bruker Avance III spec-
trometer. Chemical shifts are reported in delta (δ) units, ppm
relative to the center of the triplet at 77.0 ppm for CDCl3 and
39.5 ppm for DMSO-d6. 13C NMR spectra were routinely run
with broadband decoupling. All reactions were run under an
atmosphere of air, unless otherwise indicated. Analytical
thin-layer chromatography (TLC) was carried out using
0.2 mm commercial silica gel plates.
[Cp*Ir(bpy)Cl]Cl (cat.1),23 [Cp*Ir(NH3)3][Cl]2 (cat.2),18
[Cp*Ir(bpy)(H2O)][OTf ]2 (cat.3),19 [Cp*Ir(H2O)3][OTf ]2 (cat.4),20a
[Cp*Ir(H2O)3][BF4]2 (cat.5)20a and [Cp*Ir(H2O)3][PF6]2 (cat.6)20a
were synthesized according to previous reports.
General procedure for the rearrangement of aldoximes to
amides in water catalyzed by [Cp*Ir(H2O)3][OTf]2
To an oven-dried, 25 ml Schlenk tube were added aldoxime
(0.5 mmol), [Cp*Ir(H2O)3][OTf ]2 (0.0075 mmol, 1.5 mol%)
and H2O (1 ml). The reaction mixture was heated at 110 °C
or 120 °C for 12 h and allowed to cool to ambient tempera-
ture. The reaction mixture was concentrated in vacuo, washed
with hexane, and isolated by simple filtration to afford the
desired product.
Scheme 2 Two different reaction mechanisms.
Conclusion
We have demonstrated a general and highly efficient protocol
for the rearrangement of aldoximes to amides in water under
an air atmosphere catalyzed by a water-soluble iridium
complex. In the presence of [Cp*Ir(H2O)3][OTf ]2, a variety of
aldoximes, including aromatic, aliphatic, conjugated unsatu-
rated and non-conjugated unsaturated, were converted into
their corresponding amides with good to excellent yields.
Further, the one-pot synthesis of amides from aldehydes,
hydroxylamine hydrochloride and sodium carbonate via a
tandem condensation–rearrangement reaction in water was
also accomplished. Compared with the reported organome-
tallic catalysts for the rearrangement of aldoximes to amides
in water, the present catalyst exhibited some advantages such
as being phosphorus ligand-free, having a low catalyst loading
and operational convenience under an air atmosphere.
Benzamide (2a)5a
MP 128–129 °C; 1H NMR (500 MHz, CDCl3) δ 7.82 (d, J = 7.6 Hz,
2H, ArH), 7.54 (t, J = 7.3 Hz, 1H, ArH), 7.45 (t, J = 7.6 Hz, 2H,
ArH), 6.16 (br s, 1H, NH), 6.00 (br s, 1H, NH); 13C NMR
(125 MHz, CDCl3) δ 169.7, 133.3, 131.9, 128.6, 127.3.
4-Methylbenzamide (2b)5a
MP 159–160 °C; 1H NMR (500 MHz, CDCl3) δ 7.71 (d, J = 7.9 Hz,
2H, ArH), 7.25 (d, J = 7.9 Hz, 2H, ArH), 6.12 (br s, 1H, NH), 5.87
(br s, 1H, NH), 2.41 (s, 3H, CH3); 13C NMR (125 MHz, CDCl3)
δ 169.5, 142.5, 130.4, 129.2, 127.3, 21.4.
4-Isopropylbenzamide (2c)24
MP 152–153 °C; 1H NMR (500 MHz, CDCl3) δ 7.75 (d, J = 8.2 Hz,
2H, ArH), 7.30 (d, J = 8.2 Hz, 2H, ArH), 6.09 (br s, 1H, NH),
5.84 (br s, 1H, NH), 2.96 (heptet, J = 6.9 Hz, 1H, CH), 1.27
(d, J = 6.9 Hz, 6H, CH3); 13C NMR (125 MHz, CDCl3) δ 169.8,
153.2, 130.8, 127.5, 126.6, 34.1, 23.7.
Experimental section
General experimental details
High-resolution mass spectra (HRMS) were obtained on a
HPLC-Q-Tof MS(Micro) spectrometer and are reported as m/z
(relative intensity). Accurate masses are reported for the
molecular ion [M + Na]+. Melting points (MPs) were mea-
sured on an X-6 micro-melting apparatus. Proton nuclear
magnetic resonance (1H NMR) spectra were recorded at
500 MHz using a Bruker Avance III spectrometer. Chemical
shifts are reported in delta (δ) units, parts per million (ppm)
downfield from tetramethylsilane or ppm relative to the
center of the singlet at 7.26 ppm for CDCl3 and 2.50 ppm for
DMSO-d6. Coupling constant J values are reported in Hertz
(Hz), and the splitting patterns are designated as follows:
s, singlet; d, doublet; t, triplet; m, multiplet; b, broad.
Carbon-13 nuclear magnetic resonance (13C NMR) spectra
4-(tert-Butyl)benzamide (2d)24
MP 173–174 °C; 1H NMR (500 MHz, CDCl3) δ 7.75 (d, J = 8.1 Hz,
2H, ArH), 7.47 (d, J = 8.0 Hz, 2H, ArH), 6.10 (br s, 1H, NH), 5.80
(br s, 1H, NH), 1.34 (s, 9H, CH3); 13C NMR (125 MHz, CDCl3)
δ 169.5, 155.5, 130.4, 127.2, 125.5, 34.9, 31.1.
4-Methoxybenzamide (2e)12
MP 167–168 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.85–7.83
(m, 3H, ArH and NH), 7.19 (br s, 1H, NH), 6.97 (d, J = 8.3 Hz,
2H, ArH), 3.80 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6)
δ 167.4, 161.5, 129.3, 126.5, 113.3, 55.3.
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3,4-Dimethoxybenzamide (2f)25
2-Nitrobenzamide (2n)5a
MP 166–167 °C; 1H NMR (500 MHz, CDCl3) δ 7.46 (d, J = 1.9 Hz,
1H, ArH), 7.34 (dd, J = 8.3 Hz and J = 1.9 Hz, 1H, ArH),
6.88 (d, J = 8.4 Hz, 1H, ArH), 6.09 (br s, 1H, NH), 5.84 (br s,
1H, NH), 3.94 (s, 3H, OCH3), 3.93 (s, 3H, OCH3); 13C NMR
(125 MHz, CDCl3) δ 169.2, 152.1, 148.9, 125.8, 120.1, 110.7,
110.2, 56.0.
MP 175–176 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.15 (br s,
1H, NH), 7.99 (s, 1H, ArH), 7.76–7.67 (m, 4H, ArH and NH);
13C NMR (125 MHz, DMSO-d6) δ 167.2, 147.2, 133.3, 132.6,
130.6, 128.8, 123.9.
4-Nitrobenzamide (2o)12
MP 199–200 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.30 (br s,
3H, ArH and NH), 8.09 (s, 2H, ArH), 7.73 (br s, 1H, NH);
13C NMR (125 MHz, DMSO-d6) δ 166.2, 149.1, 140.0, 128.9, 123.4.
2-Fluorobenzamide (2g)12
MP 115–116 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.69–7.64
(m, 3H, ArH and 2xNH), 7.54–7.50 (m, 1H, ArH), 7.29–7.25
(m, 2H, ArH); 13C NMR (125 MHz, DMSO-d6) δ 165.2, 159.3
3-(Trifluoromethyl)benzamide (2p)29
(d, JC–F = 247.7 Hz), 132.4 (d, JC–F = 8.8 Hz), 130.2 (d, JC–F
=
MP 120–121 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.24 (br s,
1H, NH), 8.21 (s, 1H, ArH), 8.17 (d, J = 7.8 Hz, 1H, ArH), 7.90
(d, J = 7.8 Hz, 1H, ArH), 7.71 (t, J = 7.8 Hz, 1H, ArH), 7.64
(br s, 1H, NH); 13C NMR (125 MHz, DMSO-d6) δ 166.3, 135.2,
131.4, 129.5, 129.1 (q, JC–F = 31.8 Hz), 127.7 (q, JC–F = 2.8 Hz),
124.1 (q, JC–F = 270.8 Hz), 124.0 (q, JC–F = 2.8 Hz).
2.5 Hz), 124.3 (d, JC–F = 2.6 Hz), 123.8 (d, JC–F = 14.0 Hz),
116.0 (d, JC–F = 22.5 Hz).
4-Fluorobenzamide (2h)12
MP 156–157 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.00 (br s,
1H, NH), 7.95–7.92 (m, 2H, ArH), 7.41 (br s, 1H, NH), 7.28
(t, J = 8.8 Hz, 2H, ArH); 13C NMR (125 MHz, DMSO-d6)
δ 166.8, 163.9 (d, JC–F = 246.8 Hz), 130.7 (d, JC–F = 1.9 Hz),
130.0 (d, JC–F = 9.0 Hz), 115.0 (d, JC–F = 21.4 Hz).
4-(Trifluoromethoxy)benzamide (2q)12
MP 146–147 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.08 (br s,
1H, NH), 7.99 (d, J = 8.8 Hz, 2H, ArH), 7.51 (br s, 1H, NH),
7.45 (d, J = 8.3 Hz, 2H, ArH); 13C NMR (125 MHz, DMSO-d6)
δ 166.6, 150.3, 133.4, 129.7, 120.4, 119.9 (q, JC–F = 255.5 Hz).
2-Chlorobenzamide (2i)12
MP 143–144 °C; 1H NMR (500 MHz, CDCl3) δ 7.80 (d, J = 7.5 Hz,
1H, ArH), 7.44–7.34 (m, 3H, ArH), 6.38 (br s, 1H, NH), 6.12
(br s, 1H, NH); 13C NMR (125 MHz, CDCl3) δ 168.4, 133.8,
131.7, 130.8, 130.5, 130.3, 127.1.
2-Naphthamide (2r)30
1
MP 196–197 °C; H NMR (500 MHz, DMSO-d6) δ 8.48 (s, 1H,
4-Chlorobenzamide (2j)12
ArH), 8.14 (br s, 1H, NH), 8.01–7.96 (m, 4H, ArH), 7.62–7.57
(m, 2H, ArH), 7.48 (br s, 1H, NH); 13C NMR (125 MHz,
DMSO-d6) δ 168.0, 134.2, 132.1, 131.6, 128.9, 127.8, 127.8,
127.6, 126.6, 124.4.
MP 178–179 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.06 (br s,
1H, NH), 7.88 (d, J = 8.4 Hz, 2H, ArH), 7.52 (d, J = 8.4 Hz, 2H,
ArH), 7.48 (br s, 1H, NH); 13C NMR (125 MHz, DMSO-d6)
δ 166.8, 136.1, 133.0, 129.4, 128.3.
Thiophene-2-carboxamide (2s)12
3,4-Dichlorobenzamide (2k)26
MP 179–180 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.95 (br s,
1H, NH), 7.73 (s, 2H, ArH), 7.37 (br s, 1H, NH), 7.12 (s, 1H,
ArH); 13C NMR (125 MHz, DMSO-d6) δ 162.9, 140.3, 130.9,
128.7, 127.9.
MP 138–139 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.15 (br s,
1H, NH), 8.10 (s, 1H, ArH), 7.84 (d, J = 8.2 Hz, 1H, ArH), 7.75
(d, J = 8.6 Hz, 1H, ArH), 7.62 (br s, 1H, NH); 13C NMR
(125 MHz, DMSO-d6) δ 165.5, 134.6, 134.0, 131.2, 130.6,
129.4, 127.7.
2-Phenylacetamide (2t)31
MP 152–153 °C; 1H NMR (500 MHz, CDCl3) δ 7.37 (t, J = 7.4 Hz,
2H, ArH), 7.32–7.26 (m, 3H, ArH), 5.47 (br s, 1H, NH), 5.37
(br s, 1H, NH), 3.60 (s, 2H, CH2); 13C NMR (125 MHz, CDCl3)
δ 173.6, 134.8, 129.4, 129.0, 127.4, 43.3.
2-Bromobenzamide (2l)27
MP 158–159 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.88 (br s,
1H, NH), 7.64–7.58 (m, 2H, ArH), 7.41–7.34 (m, 3H, ArH);
13C NMR (125 MHz, DMSO-d6) δ 169.0, 139.3, 132.7, 130.6,
128.5, 127.5, 118.6.
3-Phenylpropanamide (2u)12
4-Bromobenzamide (2m)28
MP 99–100 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.30–7.25
(m, 3H, ArH and NH), 7.21–7.15 (m, 3H, ArH), 6.78 (br s, 1H,
NH), 2.79 (t, J = 7.7 Hz, 2H, CH2), 2.34 (t, J = 7.5 Hz, 2H,
CH2); 13C NMR (125 MHz, DMSO-d6) δ 173.4, 141.5, 128.2,
128.2, 125.8, 36.7, 30.9.
MP 190–191 °C; 1H NMR (500 MHz, DMSO-d6) δ 8.06 (br s,
1H, NH), 7.81 (d, J = 8.1 Hz, 2H, ArH), 7.67 (d, J = 8.1 Hz, 2H,
ArH), 7.48 (br s, 1H, NH); 13C NMR (125 MHz, DMSO-d6)
δ 166.9, 133.4, 131.2, 129.6, 125.0.
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Butyramide (2v)5a
6.39 (d, J = 15.7 Hz, 1H, CH); 13C NMR (125 MHz, DMSO-d6)
δ 166.5, 150.9, 144.7, 126.6, 119.6, 113.6, 112.3.
1
MP 111–112 °C; H NMR (500 MHz, CDCl3) δ 5.82 (br s, 1H,
NH), 5.54 (br s, 1H, NH), 2.21 (t, J = 7.6 Hz, 2H, CH2), 1.67
(sext, J = 7.4 Hz, 2H, CH2), 0.97 (t, J = 7.5 Hz, 3H, CH3);
13C NMR (125 MHz, CDCl3) δ 176.0, 37.8, 18.9, 13.6.
2,6-Dimethylhept-5-enamide (4g)
MP 70–71 °C; 1H NMR (500 MHz, CDCl3) δ 5.67 (br s, 1H,
NH), 5.47 (br s, 1H, NH), 5.08 (s, 1H, CH), 2.28 (s, 1H, CH),
2.02 (s, 2H, CH2), 1.69 (s, 3H, CH3), 1.60 (s, 3H, CH3), 1.42 (s, 2H,
CH2), 1.16 (s, 3H, CH3); 13C NMR (125 MHz, CDCl3) δ 179.1,
132.2, 123.7, 40.1, 34.2, 25.7, 25.7, 17.7, 17.7; HRMS-EI
(70 eV) m/z calcd for C9H17NONa [M + Na]+ 178.1208, found
178.1201.
Hexanamide (2w)12
MP 95–96 °C; 1H NMR (500 MHz, CDCl3) δ 5.67 (br s, 1H,
NH), 5.49 (br s, 1H, NH), 2.22 (t, J = 7.6 Hz, 2H, CH2),
1.67–1.61 (m, 2H, CH2), 1.34–1.31 (m, 4H, CH2), 0.90 (t, J =
6.8 Hz, 3H, CH3); 13C NMR (125 MHz, CDCl3) δ 175.7, 35.9,
31.4, 25.2, 22.3, 13.9.
Cyclohex-3-enecarboxamide (4h)37
MP 125–126 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.25 (br s,
1H, NH), 6.73 (br s, 1H, NH), 5.65 (br s, 2H, 2xCH), 2.30–2.26
(m, 1H, ArH), 2.05–1.93 (m, 4H, ArH), 1.78–1.76 (m, 1H,
ArH), 1.51–1.42 (m, 1H, ArH); 13C NMR (125 MHz, DMSO-d6)
δ 177.1, 126.3, 125.9, 27.6, 25.4, 24.4.
Cinnamamide (4a)5a
MP 148–149 °C; 1H NMR (500 MHz, DMSO-d6) δ 7.56–7.55
(m, 3H, ArH, NH, CH), 7.43–7.36 (m, 4H, ArH), 7.13 (br s, 1H,
NH), 6.61 (d, J = 16.0 Hz, 1H, CH); 13C NMR (125 MHz,
DMSO-d6) δ 166.7, 139.2, 134.9, 129.5, 128.9, 127.6, 122.3.
The one-pot synthesis of amides from aldehydes, hydroxylamine
hydrochloride and sodium carbonate catalyzed by
[Cp*Ir(H2O)3][OTf]2
(E)-3-(m-Tolyl)acrylamide (4b)32
MP 81–82 °C; 1H NMR (500 MHz, CDCl3) δ 7.62 (d, J = 15.6 Hz,
1H, CH), 7.33–7.31 (m, 2H, ArH), 7.28–7.25 (m, 1H, ArH), 7.18
(d, J = 7.2 Hz, 1H, ArH), 6.45 (d, J = 15.8 Hz, 1H, CH), 5.66
(br s, 2H, NH), 2.37 (s, 3H, CH3); 13C NMR (125 MHz, CDCl3)
To an oven-dried 25 ml Schlenk tube were added the aldehyde
5 or 6 (0.5 mmol), hydroxylamine hydrochloride 7 (1 equiv.),
and Na2CO3 (0.5 equiv.) and H2O (1 ml), and the mixture
was stirred at room temperature for 0.5 h. Then,
[Cp*Ir(H2O)3][OTf ]2 (1.5 mol%) was added into the reactor,
the reaction mixture was heated at 110 °C for another 12 h
and was allowed to cool to ambient temperature. The reaction
mixture was concentrated in vacuo, washed with hexane, and
isolated by simple filtration to afford the desired product.
δ
167.8, 142.7, 138.5, 134.4, 130.8, 128.7, 128.6, 125.1,
119.2, 21.3.
(E)-3-(2-Nitrophenyl)acrylamide (4c)33
1
MP 168–169 °C; H NMR (500 MHz, DMSO-d6) δ 8.04 (d, J =
7.7 Hz, 1H, CH), 7.78 (s, 2H, ArH), 7.69–7.64 (m, 3H, ArH and
NH), 7.29 (br s, 1H, NH), 6.61 (d, J = 15.5 Hz, 1H, CH);
13C NMR (125 MHz, DMSO-d6) δ 165.7, 148.3, 134.0, 133.7,
130.2, 129.9, 128.7, 127.1, 124.5.
The procedure for the hydration of benzonitrile 8 in water
catalyzed by [Cp*Ir(H2O)3][OTf]2
To an oven-dried, 25 ml Schlenk tube were added benzonitrile
8 (0.5 mmol), [Cp*Ir(H2O)3][OTf ]2 (1.5 mol%) and water
(1 ml). The reaction mixture was heated at 110 °C for 12 h,
and allowed to cool to ambient temperature. No conversion
was observed from the 1H NMR spectrum of the mixture.
(E)-3-(4-Fluorophenyl)acrylamide (4d)34
1
MP 130–131 °C; H NMR (500 MHz, DMSO-d6) δ 7.62 (s, 2H,
ArH), 7.53 (br s, 1H, NH), 7.41 (d, J = 15.6 Hz, 1H, CH), 7.24
(t, J = 7.1 Hz, 2H, ArH) 7.10 (br s, 1H, NH), 6.55 (d, J =
15.7 Hz, 1H, CH); 13C NMR (125 MHz, DMSO-d6) δ 166.6,
162.6 (d, JC–F = 245.7 Hz), 137.9, 131.5, 129.7 (d, JC–F = 33.3 Hz),
122.2, 115.8 (d, JC–F = 21.8 Hz).
The procedure for the hydration of benzonitrile 8 with the
aid of butylaldoxime in water catalyzed by
[Cp*Ir(H2O)3][OTf]2
(E)-3-(3-Chlorophenyl)acrylamide (4e)35
To an oven-dried, 25 ml Schlenk tube were added benzonitrile
8 (0.5 mmol), butylaldoxime 1v (2 equiv.), [Cp*Ir(H2O)3][OTf ]2
(1.5 mol%) and water (1 ml). The reaction mixture was heated
at 110 °C for 12 h, and allowed to cool to ambient tempera-
ture. The reaction mixture was concentrated in vacuo, washed
with hexane, and isolated by simple filtration to afford the
desired product.
MP 75–76 °C; 1H NMR (500 MHz, CDCl3) δ 7.58 (d, J = 15.8 Hz,
1H, CH), 7.50 (s, 1H, ArH), 7.38–7.29 (m, 3H, ArH), 6.46 (d, J =
15.7 Hz, 1H, CH), 5.78 (br s, 2H, 2xNH); 13C NMR (125 MHz,
CDCl3) δ 168.0, 140.7, 136.3, 134.7, 130.0, 129.7, 127.4,
126.2, 121.2.
(E)-3-(Furan-2-yl)acrylamide (4f)36
Acknowledgements
1
MP 170–171 °C; H NMR (500 MHz, DMSO-d6) δ 7.76 (s, 1H,
ArH), 7.57 (br s, 1H, NH), 7.21 (d, J = 16.0 Hz, 1H, CH), 7.08
(br s, 1H, NH), 6.75 (d, J = 2.6 Hz, 1H, ArH), 6.58 (s, 1H, ArH)
Financial support by National Natural Science Foundation
of China (no. 21272115) and Fundamental Research Funds
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for the Central Universities (no. 30920130111005 and no.
30920130122002) is greatly appreciated.
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