Microwave-promoted one-pot conversion of alcohols to oximes using 1-methylimidazolium nitrate, [Hmim][NO3], as a green promoter and medium

Article abstract of DOI:10.1016/j.crci.2011.06.003

A wide variety of oximes were prepared from different types of alcohols with hydroxylamine hydrochloride using 1-methylimidaziloum nitrate, [Hmim][NO₃], ionic liquid as a reaction medium and promoter under microwave irradiation. This protocol provides a one-pot oxime synthesis with high yields that is facile, eco-friendly and the ionic liquid can be recovered and reused.

Full text of DOI:10.1016/j.crci.2011.06.003

C. R. Chimie 14 (2011) 1065–1070
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Preliminary communication/Communication
Microwave-promoted one-pot conversion of alcohols to oximes using
1-methylimidazolium nitrate, [Hmim][NO3], as a green promoter
and medium
a
a
Arsalan Mirjafari a, , Niloufar Mobarrez , Richard A. O’Brien , James H. Davis Jr a,b, Jalil Noei c
*
a Department of Chemistry, University of South Alabama, Mobile, Alabama 36688, USA
b Department of Chemical and biomolecular Engineering, University of South Alabama, Mobile, Alabama 36688, USA
c Department of Chemistry, Islamic Azad University, Mahshahr Branch, Mahshahr 63519, Iran
A B S T R A C T
wide variety of oximes were prepared from different types of alcohols with
A R T I C L E I N F O
A
Article history:
Received 18 April 2011
Accepted after revision 17 June 2011
Available online 30 July 2011
hydroxylamine hydrochloride using 1-methylimidaziloum nitrate, [Hmim][NO3], ionic
liquid as a reaction medium and promoter under microwave irradiation. This protocol
provides a one-pot oxime synthesis with high yields that is facile, eco-friendly and the
ionic liquid can be recovered and reused.
Keywords:
ß 2011 Acade
´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
[Hmim][NO3]
Ionic liquids
Oxime
Microwave irradiation
Oximes and oxime ether functional groups are used in a
large range of pharmaceutical molecules and are incorpo-
rated into many organic medicinal agents, including some
antibiotics such as gemifloxacin mesylate I, pralidoxime
chloride II and obidoxime chloride III (Scheme 1), which
are used in the treatment of poisoning by organophosphate
insecticides, malathion and diazinon [1]. Moreover, oximes
are frequently used in synthetic organic chemistry [2]. Its
synthetic utility is principally as an important precursor
for numerous functional group transformations such as
nitriles [3], nitro compounds [4], amines [5] and amides
[6]. The conventional synthesis procedure for oximes is
based on the reactions of hydroxylamine hydrochloride
and corresponding aldehydes or ketones in an acidic or
basic medium, and typically produces both isomeric
oximes, E and Z [7]. However, some oxidative preparations
of aldehydes or ketones are not desirable due to the
presence of other readily oxidizable functional groups. In
addition, the highly reactive nature of aldehydes and
ketones makes them unsuitable for oxime-forming reac-
tions [8].
Task-specific ionic liquids (TSILs) have gained increas-
ing interest in the context of green synthesis with their
dual roles as catalysts and solvents (media) in recent years.
Although ionic liquids were initially introduced as
alternative green reaction media because of their unique
chemical and physical properties (e.g. non-volatility, high
thermal and chemical stability, good solvating capability,
wide liquid range and ease of recycling), nowadays these
ionic liquids have achieved success and show increasing
promise in controlling the reaction as catalysts [9].
Furthermore, there are many reports concerning the
applications of these organic salts in the literature such
as cellulose dissolution [10], energetic materials [11],
lubricants [12], fuel cells [13], solar cell [14], CO2 capture
[15] and active pharmaceutical ingredients (APIs) [16].
According to the literature, very few improved proce-
dures have been reported for the direct conversion of
alcohols to oximes [5,8,17]. Thus, development of an
efficient and eco-friendly method for a direct conversion of
alcohols to oximes is desirable. In view of this fact and also
as a part of our program to explore the full potential of
* Corresponding author.
E-mail address: mirjafari@usouthal.edu (A. Mirjafari).
1631-0748/$ – see front matter ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.06.003

1066
A. Mirjafari et al. / C. R. Chimie 14 (2011) 1065–1070
Table 1
Synthesis of benzaldeheyde oxime under various experimental conditions.a
Entry
Catalyst
Temp. (8C)
Time (min)
Conditions
Yield (%)d
1
No catalyst
85
85
85
85
85
85
85
80
85
75
80
80
80
10
10
5
MWb
MWb
MWb
MWb
MWb
MWb
MWb
MWb
MWb
MWb
MWb
MWb
CHc
0
0
2
HNO3
3
[bmim][PF6]
[bmim][NTf2]
[bmim][Cl]
0
4
5
0
5
5
0
6
[Hmim][Cl]
[Hmim][HSO4]
[Hmim][NO3]
[Hmim][NO3]
[Hmim][NO3]
[Hmim][NO3]
[Hmim][NO3]
[Hmim][NO3]
5
0
7
5
0
8
2.5
2.5
2.5
2
95
95
89
86
95
0
9
10
11
12
13
3
2.5
The bold data is used to distinguish optimized reaction conditions (Entry 8) from non-optimized reactions (Entries 1–7 and 9–13).
a
Reaction conditions: Alcohol (1 mmol), hydroxylamine hydrochloride (1.3 mmol), [Hmim][NO3] (2 mL).
b
Microwave irradiation (80 W).
c
Conventional heating.
d
Isolated yields.
promoter in the oxidative aromatic chlorination and has
considerable potential as a reaction medium [20].
The reactions were carried out in a Micro–SYNTH
labstation microwave system in an open vessel. During the
experiments; power, temperature, time and pressure were
monitored and controlled with the ‘‘easyCONTROL’’ soft-
ware.1 Reaction of benzyl alcohol 1a and hydroxylamine
hydrochloride 2 was selected as a model experiment in
order to optimize the reaction conditions. The type of ionic
liquids, as well as the effect of temperature and reaction
time were investigated and the obtained results are
illustrated in Table 1.
The efficiency of the potential oxidative systems was
studied in the model reaction. Experiments were carried out
using nitric acid (Table 1, entry 2), different types of classic
(Table1, entries3–5)andBrønstedacidicionicliquids(Table
1, entries6to13)inthepresenceofairandundermicrowave
irradiation (80 W). It was found that [Hmim][NO3] was the
most effective system, producing almost quantitative yields
of corresponding oxime 3a (Table 1, entry 8). While the
reaction occurred even at 85 8C, the best yield of benzalde-
hyde oxime 3a was obtained at 80 8C for 2.5 min under
microwave irradiation (80 W) (Table 1, entry 9). Reducing
the reaction temperature and time led to a reduction in the
desired product’s yield (Table 1, entries 10 and 11). In
addition, over longer reaction times, an increase in the yield
of benzaldehydeoximewas notobserved (Table1, entry 12).
The role of microwave energy was also determined by
conductinga modelreactionatelevatedtemperature(80 8C)
Scheme 1.
TSILs in chemical transformations [18], an efficient, one-
pot, environmentally-benign protocol for direct micro-
wave-promoted conversion of a variety of alcohols to the
corresponding oximes without going through aldehydes
and ketones, using Brønsted acidic ionic liquid, 1-
methylimidazolium nitrate [Hmim][NO3], as a promoter
and medium is reported in this communication.
The general synthetic strategy for the preparation of
various types of oximes is simple and versatile. The
reaction of alcohols with hydroxylamine hydrochloride
using [Hmim][NO3] in the presence of air and under
microwave irradiation (Scheme 2) resulted in formation of
the desired oximes. Brønsted acidic [Hmim][NO3] was
prepared simply by neutralization. Combination of 1-
methylimidazole with HNO3 (67% w/w) in a 1:1 molar ratio
produces, after water removal, a white solid (Tm = 60 8C)
identified as 1-methylimidazolium nitrate. This ionic
liquid is air-stable, hydrophilic, easy to prepare and
handle, and its physicochemical properties have been
studied [19]. It has been used as a co-solvent and even as a
1
The microwave system used in these experiments includes the
following items: Micro-SYNTH labstation, equipped with a glass door, a
dual magnetron system with pyramid shaped diffuser, 1000 W delivered
power, exhaust system, magnetic stirrer, ‘‘quality pressure’’ sensor for
flammable organic solvents, and ATC-FO fiber optic sensor TS3517 for
automatic temperature control.

A. Mirjafari et al. / C. R. Chimie 14 (2011) 1065–1070
1067
Scheme 2.
Table 2
Microwave-promoted synthesis of oximes by oxidation/oxime-forming reaction using [Hmim][NO3] as a catalyst-medium.a
Entry
1
Alcohol
Oxime
Time (min)
2.5
Yield (%)b
95
E/Z (%)c
3a
0/100
2
3
3b
3c
3
5
97
89
25/75
0/100
4
5
3d
3e
3
93
95
12/88
0/100
2.5
6
3f
6
85
0/100
7
8
3g
3h
2.5
2.5
99
96
35/75
34/76
9
3i
2.5
96
31/69
10
11
3j
3
3
97
97
30/70
41/59
3k
12
3l
3
94
44/56

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A. Mirjafari et al. / C. R. Chimie 14 (2011) 1065–1070
Table 2 (Continued )
Entry
13
Alcohol
Oxime
Time (min)
4.5
Yield (%)b
92
E/Z (%)c
39/61
3m
14
3n
4
94
0/100
a
Reaction conditions: alcohol (1 mmol), hydroxylamine hydrochloride (1.3 mmol), [Hmim][NO3] (2 mL), MW power (80 W).
b
c
Isolated yield.
Separated by column chromatography.
applying conventional heating conditions. As expected, this
Results are summarized in Table 2. Benzyl-, allyl-, and
propargyl alcohols are also good substrates for this
reaction and their corresponding oximes were obtained
in 95, 96, and 96% yields, respectively (Table 2, entries 1, 8
and 9). Secondary alcohols led to ketoximes in the same
manner as aldoximes (Table 2, entries 3, 6 and 14).
Similarly, this protocol is also applicable for the direct
synthesis of oximes from hindered alcohols. For instance,
2’,4’,6’-trimethylacetophenone oxime can be easily pre-
pared in 6 min under microwave irradiation (Table 2, entry
reaction failed to give the desired product and starting
materials were recovered unchanged (Table 1, entry 13)
possibly because of the strong synergic effect of the
microwave energy and ionic liquid.
In order to explore the scope and versatility of
[Hmim][NO3] ionic liquid, various types of structurally
divergent primary and secondary alcohols 1 and hydrox-
ylamine hydrochloride 2 (Scheme 2) underwent smooth
microwave-promoted oxidation/oxime-forming reactions
to afford the corresponding oximes 3a–n in excellent
yields (85–99%) within short time periods (2.5–6 min).2
4-Phenyl-butan-2-one oxime (3c)
Z isomer: white crystalline solid, Tm = 83–84 8C (lit. [8] 81.5–81.8 8C);
IR (neat, cm-1): nmax 3249, 1685, 1555, 981, 834; 1H NMR (CDCl3,
400 MHz): dH 7.20–7.30 (m, 5H), 2.87 (dd, J = 8.3, 7.6 Hz, 2H), 2.55 (dd,
J = 9.3, 7.6 Hz, 2H), 1.96 (s, 3H); 13C NMR (CDCl3, 100 MHz): dC 158.3,
142.1, 129.7,129.3, 127.7, 39.2, 33.9, 14.8.
2
General procedure for the synthesis of oximes
A mixture of alcohol, 1 (1 mmol), hydroxylamine hydrochloride 2
(1.3 mmol) and [Hmim][NO3] (2 mL) was stirred and irradiated for the
appropriate times (Table 2). The progress of the reaction was monitored
by TLC (n-hexane–Et2O, 5:1). After completion of the reaction, 10 mL
water was added to reaction mixture and extracted with diethyl ether
(3 Â 10 mL). The organic phase were dried over anhydrous MgSO4 and
then removed under reduced pressure to obtain the crude products,
which were purified by recrystallization from n-hexane and ethyl acetate
to afford the pure products in 85–99%. E and Z isomers were isolated by
column chromatography on silica gel (200 mesh), eluted with n-hexane
and diethyl ether. The water in the ionic liquid was evaporated in vacuo
and the residual ionic liquid then washed with small amount of diethyl
ether, dried under vacuum at 80 8C for 12 h and reused for the next run
without noticeable effect on the reaction yields.
4-Methoxybenzaldehyde oxime (3d)
E isomer: white crystalline solid, Tm = 63–64 8C (lit. [5b] 62–64 8C; IR
(neat, cm-1): nmax 3253, 3018, 1618, 1513, 1259, 1177; 1H NMR (CDCl3,
400 MHz): dH 8.11 (s, 1H), 7.60 (d, J = 9.4 Hz, 2H), 6.94 (d, J = 9.4 Hz, 2H),
3.86 (s, 3H); 13C NMR (CDCl3, 100 MHz): dC 163.0, 151.8, 129.9, 126.9,
117.9, 57.3.
Z isomer: white crystalline solid, Tm = 129–131 8C (lit. [5b] 132–
n
134 8C); IR (neat, cm-1): max 3176, 2849, 1632, 1517, 1273, 1172; 1H NMR
(CDCl3, 400 MHz): dH 7.97 (d, J = 8.4 Hz, 2H), 7.35 (s, 1H), 6.97 (d, J = 9.4 Hz,
2H), 3.89 (s, 3H); 13C NMR (CDCl3, 100 MHz): dC 160.7, 146.3, 132.9,
123.5,113.8, 55.3.
4-Nitrobenzaldehyde oxime (3e)
1H and 13C NMR were recorded on a JEOL LA-400 spectrometer. All 1
NMR spectra are reported in units, parts per million (ppm) downfield
H
E isomer: white crystalline solid, Tm = 126–128 8C (lit. [8] 127.6–
128.4 8C); IR (neat, cm-1): nmax 3307, 1605, 1537, 1513, 1349; 1H NMR
d
from tetramethylsilane (TMS) as the internal standard and coupling
constants are indicated in Hertz (Hz). All 13C NMR spectra are reported in
ppm relative to the central line of the triplet for CDCl3 at 77.0 ppm.
Infrared spectra (IR) were recorded on a Perkin-Elmer 298 Spectropho-
tometer. Melting points, determined on a MEL-TEMP Apparatus, are
uncorrected.
(CDCl3, 400 MHz): dH 8.29 (d, J = 8.4 Hz, 2H), 8.25 (s, 1H), 7.77 (d, J = 8.4 Hz,
2H), 7.72(s, 1H); 13C NMR (CDCl3, 100 MHz):
124.1.
dC 148.3, 148.3, 138.1, 127.6,
2’-4’-6’-Trimethylacetophenone oxime (3f)
isomer: white crystalline solid. Tm = 100–102 C (lit. [8] 96.0–
96.3 8C); IR (neat, cm-1): nmax 3340, 2965, 1632, 1434; 1H NMR (CDCl3,
400 MHz) H 6.95 (s, 2H, minor), 6.88 (s, 2H, major), 2.58 (s, 3H, major and
˚
Z
Physical characteristics and spectral data of products:
Benzaldehyde oxime (3a)
d
minor), 2.32 (s, 6H, major), 2.28 (s, 6H, minor), 2.18 (s, 3H, major), 2.10 (s,
minor); 13C NMR (CDCl3, 100 MHz) dC 159.8, 158.0, 138.7, 137.8, 135.7,
134.2, 133.5, 132.4, 128.2, 128.0, 21.2, 21.0, 20.7, 19.7, 19.2, 16.3.
(2E)-3-Phenylprop-1-enal oxime (3g)
E isomer: white crystalline solid, Tm = 68–69 8C (lit. [8] 69.1–70.5 8C);
IR (neat, cm-1): max 3263, 1644, 1449, 1311; 1H NMR (CDCl3, 400 MHz) dH
n
Z isomer: white crystalline solid, Tm = 131–133 8C, IR (neat, cm-1
) nmax
1494, 1445, 1306, 1291, 953, 755, 692; 1H NMR (CDCl3, 400 MHz):
d
H 7.95
(m, 2H), 7.38 (m, 3H), 7.29 (s, 1H); 13C NMR (CDCl3, 100 MHz):
131.8, 130.1, 128.7, 127.1.
dC 150.6,
3-Phenylpropanal oxime (3b)
E and Z isomers: white crystalline solid, Tm = 95–97 8C (lit. [2] 93–
95 8C); IR (neat, cm-1): max 3210, 1597, 1499, 1459, 1440, 1317; 1H NMR
(CDCl3, 400 MHz): dH 7.47 (t, J = 5.6 Hz, 1H, minor), 7.21–7.37 (m, 5H,
major and minor), 6.76 (t, J = 5.6 Hz, 1H, major), 2.83 (t, J = 7.4 Hz, 2H, major
and minor), 2.71–2.76 (m, 2H, major), 2.51–2.58 (m, 2H, minor); 13C NMR
7.96 (t, J = 4.6 Hz, 1H), 7.23–7.45 (m, 5H), 7.47 (d, J = 6.5 Hz, 1H), 6.85 (d,
J = 5.5 Hz, 1H); 13C NMR (CDCl3, 100 MHz) dC 157.9, 142.5, 137.3, 129.3,
128.3, 127.5, 122.3.
n
Z isomer: Tm = 132–1338C (lit. [8] 132.0–133.2 8C); IR (neat, cm-1):
n
max 3183, 3034, 1633, 1463, 1345; 1H NMR (CDCl3, 400 MHz)
dH 7.55 (d,
(CDCl3, 100 MHz):
d
C 153.6, 152.5, 143.7, 140.9, 128.1, 127.8, 127.5, 127.3,
J = 8.4 Hz, 1H), 7.27–7.55 (m, 6H), 6.89 (d, J = 15.8 Hz, 1H); 13C NMR
(CDCl3, 100 MHz) dC 153.3, 144.2, 136.7, 133.1, 128.4, 115.6.
127.1, 125.9, 32.5, 31.4, 30.8, 25.7.

A. Mirjafari et al. / C. R. Chimie 14 (2011) 1065–1070
1069
6), while this reaction required a very long time, 32 days,
for completion using hindered ketones at room tempera-
ture [7c]. No cis- and trans-isomerization of the double
illustrated in Table 2, a preference for the formation of Z
isomer over the E isomer was observed using this synthetic
methodology and literature reports also show this
tendency [5,8,17].
bond was observed in a cis-a,b-unsaturated alcohol (Table
2, entry 8). Furthermore, the putative avoidance of
carbonyl intermediates makes this method effective for
To further expand of the scope of [Hmim][NO3], the
reusability of this ionic liquid was studied with the model
reaction. The ionic liquid could be recovered and reused
over the three runs with only limited reduction (80–95%)
in the catalytic activity of the ionic liquid.
In summary, we have reported herein a microwave-
promoted, efficient, environmentally-benign and one-pot
conversion of alcohols to corresponding oximes using
[Hmim][NO3] as a solvent-promoter (or catalyst). This
present protocol offers attractive features such as reduced
reaction times, high yields and economic viability of the
ionic liquid.
the preparation of
b,g-unsaturated oxime (Table 2, entry
10). It is also noteworthy that in the conversion of alcohols
bearing acid-sensitive functional groups to the corre-
sponding oximes, epoxide ring-opening (Table 2, entry 11),
acetal deprotection (Table 2, entry 13) and ester hydrolysis
(Table 2, entry 14) reactions were not observed. As
(2Z)-4-Acetoxy-but-2-enal oxime (3h)
E and Z isomers: clear viscous oil; IR (neat, cm-1) 3380,1746, 1399,
1238; 1H NMR (CDCl3, 400 MHz)
dH 8.20 (d, J = 11.0 Hz, 1H, major), 7.59 (d,
J = 10.0 Hz, 1H, minor), 6.95 (dd, J = 10.5, 10.5 Hz, 1H, minor), 6.29 (dd,
J = 11.0, 11.0 Hz, 1H, major), 5.94–6.10 (m, 1H, major and minor), 4.85 (d,
J = 7.5 Hz, 2H, minor), 4.79 (d, J = 7.5 Hz, 2H,major), 2.17 (s, 3H, minor), 2.04
(s, 3H, major); 13C NMR (CDCl3, 100 MHz) dC 175.0, 172.9, 148.9, 145.2,
133.8, 132.1, 127.9, 121.0, 64.3, 62.1, 24.8, 21.7.
References
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Clarendon Press, Oxford, 1994.
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1259.
Hex-5-en-2-ynal oxime (3i)
E and Z isomers: yellow oil; IR (neat, cm-1): nmax 3234, 3117, 2874,
2316, 1640, 1411, 960, 923; 1H NMR (CDCl3, 400 MHz) dH 7.46 (t,
J = 1.6 Hz, 1H, minor), 6.84 (t, J = 1.6 Hz, 1H, major), 5.79–5.88 (m, 1H,
major and minor), 5.35–5.41 (m, 1H, major and minor), 5.17–5.19 (m, 1H,
major and minor), 3.25 (d, J = 3.8 Hz, 2H, major), 3.18 (d, J = 4.6 Hz, 2H,
minor); 13C NMR (CDCl3, 100 MHz) dC 137.5, 132.8, 132.1, 130.7, 119.3,
117.1, 100.2, 94.1, 75.7, 75.2, 23.8, 23.1.
(3Z)-Non-3-enal oxime (3j)
E and Z isomers: clear viscous oil, IR (neat, cm-1): nmax 3283, 2977,
2927, 2858, 1667, 1479, 1334; 1H NMR (CDCl3, 400 MHz) dH 7.30 (t,
J = 6.2 Hz, 1H, minor), 6.73 (t, J = 4.5 Hz, 1H, major), 5.55–5.60 (m, 1H,
major and minor), 5.37–5.55 (m, 1H, major and minor), 3.13 (t, J = 6.4 Hz,
2H, major), 2.86 (t, J = 6.5 Hz, 2H, minor), 2.02–2.06 (m, 2H, major and
minor), 1.30–1.37 (m, 6H, major and minor), 0.88–0.92 (m, 3H, major and
minor); 13C NMR (CDCl3, 100 MHz) dC 155.3, 152.2, 143.5, 132.7, 125.9,
32.6, 30.3, 29.0, 28.4, 24.1, 22.5, 17.3, 14.8.
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301.
4-(Oxiran-2-yl)butanal oxime (3k)
E and Z isomers: Yellow oil. IR (neat, cm-1): nmax 3237, 2937, 1612,
1456; 1H NMR (CDCl3, 400 MHz)
dH 7.45 (t, J = 6.2 Hz, 1H, minor), 6.74 (t,
J = 5.5 Hz, 1H, major), 2.91–2.95 (m, 1H, major and minor), 2.76–2.79 (m,
1H, major and minor), 2.44–2.52 (m, 2H, major and minor), 2.25–2.30 (m,
1H, major and minor), 1.52–1.70 (m, 4H, major and minor); 13C NMR
(CDCl3, 100 MHz) dC 155.8, 153.7, 52.9, 51.8, 48.0, 47.3, 31.9, 31.6, 29.4,
24.8, 22.9, 22.4.
[8] K. Kitahara, T. Toma, J. Shimokawa, T. Fukuyama, Org. Lett. 10 (2008)
2259.
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Wiley-VCH Verlag GmbH & Co. KGaA, Weinhiem, 2008;
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Davis Jr., J. Am. Chem. Soc. 124 (2002) 5962;
7-(Phenylseleno)heptanal oxime (3l)
(c) J..H. Davis Jr., Chem. Lett. 33 (2004) 1072;
E and Z isomers: white crystalline solid, Tm = 62–64 8C (lit. [8] 63.0–
)
63.7 8C); IR (neat, cm-1 nmax 3239, 2929, 2859, 1575, 1479; 1H NMR
(CDCl3, 400 MHz) dH 7.46–7.49 (m, 2H, major and minor), 7.41 (t, J = 6.3 Hz,
1H, minor), 7.22–7.26 (m, 3H, major and minor), 6.73 (t, J = 5.7 Hz, 1H,
major), 2.90 (t, J = 7.5 Hz, 2H, major and minor), 2.38 (q, J = 7.5, 6.5 Hz, 2H,
major), 2.18 (q, J = 7.5, 6.5 Hz, 2H, minor), 1.27–1.75 (m, 8H, major and
minor); 13C NMR (CDCl3, 100 MHz) dC 152.8, 152.5, 132.7, 130.8, 129.3,
126.9, 30.2, 29.8, 29.3, 28.7, 28.4, 27.9, 26.1, 25.3, 24.5.
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1,2:3,4-Di-O-isopropylidene-
nose oxime (3m)
a-D-galacto-hexodialdo-1,5-pyra-
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E and Z isomers: viscous oil, 107–108 8C (lit. [8] 109.6–110 8C); IR
(neat, cm-1): nmax 3420, 1397, 1266, 1233, 1179, 1173; 1H NMR (CDCl3,
400 MHz) dH 7.51 (d, J = 6.5 Hz, 1H, major), 6.88 (d, J = 4.8 Hz, 1H, minor),
5.57 (d, J = 4.8 Hz, 1H, major and minor), 5.00–5.03 (m, 1H, minor), 4.66–
4.63 (m, 2H, major), 4.62–4.66 (m, 1H, minor), 4.30–4.47 (m, 2H, major and
minor), 1.34–1.60 (m, 12H major and minor); 13C NMR (CDCl3, 100 MHz) dC
150.2, 149.3, 111.7, 111.6, 111.0, 109.9, 98.2, 97.1, 96.5, 73.2, 72.1, 71.3,
70.4, 70.2, 66.8, 66.3, 63.9, 63.5, 26.4, 25.3, 24.7, 24.5, 24.2, 24.0.
Methyl pyruvate oxime (3n)
Z isomer: white crystalline solid, Tm = 74–75 8C (lit. [8] 72.0–72.8 8C);
IR (neat, cm-1):
(CDCl3, 400 MHz)
dC 164.8, 152.3, 55.7, 10.9.
n
max 3244, 1739, 1461, 1326, 1244, 1175, 1043; 1H NMR
d
H 3.89 (s, 3H), 2.22 (s, 3H); 13C NMR (CDCl3, 100 MHz)

1070
A. Mirjafari et al. / C. R. Chimie 14 (2011) 1065–1070
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