Magnetic CuFe2O4nanoparticles: A retrievable catalyst for oxidative amidation of aldehydes with amine hydrochloride salts

Article abstract of DOI:10.1016/j.tet.2014.01.051

The application of magnetic CuFe₂O₄nanoparticles for the oxidative amidation of aldehydes with amine hydrochloride salts is described. A wide range of amides have been synthesized in good to excellent yields under mild conditions. Chiral amide also synthesized from its corresponding chiral amine salt with retention of the stereochemistry. In particular, the performance of the magnetic separation of the catalyst was very efficient and an alternative to time, solvent and energy-consuming separation procedures. The catalytic activity of the catalyst remains unaltered after five consecutive cycles, making it environmentally benign and widely applicable due to its efficiency, ease of handling and cost effectiveness.

Full text of DOI:10.1016/j.tet.2014.01.051

Tetrahedron xxx (2014) 1e9
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Magnetic CuFe2O4 nanoparticles: a retrievable catalyst for oxidative
amidation of aldehydes with amine hydrochloride salts
*
A. Suresh Kumar, B. Thulasiram, S. Bala Laxmi, Vikas S. Rawat, B. Sreedhar
Inorganic & Physical Chemistry Division, Indian Institute of Chemical Technology (Council of Scientific & Industrial Research), Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The application of magnetic CuFe2O4 nanoparticles for the oxidative amidation of aldehydes with amine
hydrochloride salts is described. A wide range of amides have been synthesized in good to excellent
yields under mild conditions. Chiral amide also synthesized from its corresponding chiral amine salt with
retention of the stereochemistry. In particular, the performance of the magnetic separation of the catalyst
was very efficient and an alternative to time, solvent and energy-consuming separation procedures. The
catalytic activity of the catalyst remains unaltered after five consecutive cycles, making it environmen-
tally benign and widely applicable due to its efficiency, ease of handling and cost effectiveness.
Ó 2014 Elsevier Ltd. All rights reserved.
Received 11 December 2013
Received in revised form 17 January 2014
Accepted 22 January 2014
Available online xxx
Keywords:
Aldehydes
Amidation
Amides
Amine salts
Magnetic nano-CuFe2O4
1. Introduction
The development of more direct catalytic approaches towards
synthesis of chemical products represents one of the key efforts of
achieving chemical sustainability.1 On the other hand, the use of
more benign catalysts and the simple separation of catalysts from
reaction mixtures provide both economical and ecological bene-
fits.2 In the last few decades, global concern for environment pro-
tection boosted the development of cost effective eco-friendly
catalytic processes. In this context, magnetic nanoparticles have
emerged as a new generation of catalysts or catalyst supports
owing to their large surface area, easy dispersion in several solvents
and more remarkably, their efficient recovery from the reaction
medium by magnetic separation.3 The magnetic nanoparticles have
been widely employed as novel magnetically recoverable catalysts
in traditional metal catalyzed reactions,4 organocatalysis and en-
zymatic catalysis.5 They are valuable addition to sustainable
methodologies as the demand for benign nanocatalysts and their
applications in synthesis is on the rise.
Fig. 1. Molecules containing an amide group.
revealed that the leading pharmaceutical companies Glaxo Smith-
Kline, Astra Zeneca and Pfizer utilized amide bond formation in
the synthesis of 66% of the drug molecules.7 Recently, the American
Chemical Society Green Chemistry Institute Pharmaceutical
Roundtable identified amide formation as one of the most utilized
and problematic synthesis in the pharmaceutical industry and has
been labeled as a high priority research field.8
Traditionally, amides were prepared by the reaction of an amine
with a carboxylic acid derivative (acyl halide or anhydride) or by
using a coupling reagent.9 However, these methods suffered from
the lability of activated carboxylic acid derivatives, use of hazardous
reagents, harsh conditions, tedious workup and generation of
Amide bond is one of the most important functional groups in
contemporary chemistry. It plays a major role in the elaboration
and composition of biological systems such as making up of peptide
bonds in proteins. It is a versatile building block in synthetic organic
chemistry and also exhibits a wide range of industrial applications
and pharmacological interest (Fig. 1).6 A comprehensive survey
* Corresponding author. E-mail address: sreedharb@iict.res.in (B. Sreedhar).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.01.051
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
Table 1
wastes that not only reduce process efficiency but also pose envi-
ronmental problems. To circumvent these problems, alternative
strategies toward the synthesis of amides have been explored.
These includes an azide based modified Staudinger reaction,10
hydrative amide synthesis with alkynes,11 thio-acid/ester ligation
methods.12 Due to the advanced properties, use of transition-metal
catalysts has developed rapidly in organic synthesis, and was also
employed to promote the formation of amides. For example, tran-
sition metal catalyzed amidations of nitriles,13 aldehydes,14 aldox-
imes,15 alcohols,16 alkenes,17 alkynes,18 and haloarenes19 with
amines have been reported. Although significant achievements
were made, the high cost of transition metals and harsh reaction
conditions restricted the large scale industrial application.
Among these the oxidative amidation of aldehydes with amine
salts is an attractive method with practicality and potential in-
dustrial applications as both starting materials are readily available
and less hazardous than those traditionally used. Recently, Li et al.,
reported an efficient and greener method for amide formation
through the oxidative amidation of aldehydes with amine hydro-
chlorides using CuIeAgIO3 as catalyst.20 However, this protocol
required a dual catalyst system and limited substrate scope. More
recently, Chen group identified iron and copper salts as effective
catalyst for the oxidative amidation of aldehydes with amine hy-
drochloride salts.21
Nanoparticles of spinel type CuFe2O4 have been recognized as
magnetic material with catalytically active copper centers, which
has resulted in a number of catalytic applications.22 The charac-
teristics of this catalyst, such as easy recovery of catalyst from the
reaction mixture by using an external magnet, efficient recycling,
and high stability make it very attractive for further applications.
Recently, we have reported the preparation, characterization, and
application of magnetic CuFe2O4 for the synthesis of tetrazoles,
triazoles and aryl amines. In continuation of our research en-
deavors on the applications of magnetic nanocatalysts,23 herein, we
have exploited magnetic CuFe2O4 nanoparticles22k for the oxidative
amidation of aldehydes with amine hydrochloride salts (Scheme 1).
Optimization of the reaction conditionsa
Entry
Oxidant
Base
Solvent
Yield (%)b
1
2
3
4
5
6
7
8
H2O2
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
d
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
Toluene
t-BuOH
Dioxane
Water
18
10
15
12
NaOCl
NaO2Cl
PhI(OAc)2
O2 balloon
TBHP
d
0
86, 84c
0
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
14
9
CaCO3
Cs2CO3
Na2CO3
K2CO3
NaHCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3
10d
15
10
11
12
13
14
15
16
17
18
19
20
21
22
25
20
23
28
18
55
15
35
THF
DMF
CH3CNþH2O (1:1)
CH3CN
CH3CN
50
38
87e
0f, 55g
a
Reaction conditions: 4-methylbenzaldehyde (1.0 mmol), glycine methyl ester
HCl salt (1.2 mmol), base (1.1 mmol), oxidant (1.1 mmol), CuFe2O4 (10 mol %),
solvent (2 mL), rt, under nitrogen atmosphere, 10 h.
b
Isolated yields.
Reaction was carried out at 80 ꢀ C.
c
d
In the absence of catalyst.
Reaction time was 24 h.
Reaction with Fe3O4 nanoparticles (10 mol %) for 24 h.
With 10 mol % CuO nanoparticles for 10 h.
e
f
g
The scope of the reaction was further probed under the estab-
lished optimal reaction conditions. As depicted in Table 1, a wide
range of aldehydes and primary amine hydrochloride salts were
reacted to give secondary amides in good to excellent yields in 10 h.
Benzaldehyde as well as benzaldehyde with electron-donating
substituents at both para and meta positions reacted well and
gave the corresponding products in 68e86% yield (Table 2, entries
1e5). Further, the reaction was extended to di- and tri-substituted
aldehydes 3,5-dimethoxyaldehyde and 3,4,5-trimethoxyaldehyde
that afforded the corresponding amides in 75 and 78% yield, re-
spectively (Table 2, entries 6e7). Halogen substituted aldehydes,
such as 3-fluoroaldehyde, 4-chloroaldehyde, 4-bromoaldehyde
reacted smoothly and gave the desired products in 74e79% yield
(Table 2, entries 8e10).
Electron withdrawing aldehydes, such as 4-cyanoaldehyde, 4-
nitrobenzaldehyde, and 4-chloro-3-nitrobenzaldehyde reacted ef-
fectively to give the expected product in 60e78% yield (Table 2,
entries 11e13). In addition, 2-naphthaldehyde and 4-phenyl
substituted aldehyde reacted smoothly and gave the correspond-
ing products in 72 and 70% yield, respectively (Table 2, entries 14
and 15). Hetero-aromatic and aliphatic aldehydes were reacted well
and gave 70 and 68% yield of amide (Table 2, entries 16 and 17). The
reaction between hindered aromatic aldehydes and glycine methyl
ester hydrochloride also led to the corresponding amide formation
in 72e75% yield (Table 2, entries 18e20).
Scheme 1. Magnetically separable CuFe2O4 nanoparticles catalyzed oxidative amida-
tion of aldehydes with amine hydrochloride salts.
2. Results and discussion
Initial
experiments
were
performed
between
4-
methylbenzaldehyde and glycine methyl ester hydrochloride to
determine the optimized reaction conditions and the results are
summarized in Table 1. We first examined different oxidant sources
and tert-butyl hydroperoxide (TBHP) was identified as the best-
suited oxidant, while other oxidants were ineffective in giving the
desired product (Table 1, entries 1e6). The effect of the bases was
studied and CaCO3 was found to be optimal, among other bases
including Cs2CO3, Na2CO3, K2CO3, and NaHCO3 (Table 1, entries
10e13). Screening of solvents was also carried out and it was found
that acetonitrile was the best solvent among others solvents
screened (Table 1, entries 14e20). Decreasing the reaction tem-
perature from 80 ꢀC to room temperature did not affect the reaction
(Table 1, entry 6). The absence and low yield of product formation
in control reactions (Table 1, entries 7e9) demonstrates the im-
portance of catalyst, base, and oxidant for this transformation.
Optimization of the reaction times showed that the reaction was
completed within 10 h at room temperature as comparable yields
obtained when the reaction was carried out for 24 h at the same
temperature (Table 1, entries 6 and 21).
When the oxidative amidation reaction was applied to L-valine
methyl ester, the reaction proceeded smoothly in 86% (ee¼98%)
yield with the retention of configuration (Table 2, entry 23). Good
activity of the catalyst for the synthesis of secondary amides from
primary amine salts inspired us, to explore its catalytic activity for
the synthesis of tertiary amides, yielding the desired amides in
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
3
Table 2
Magnetically separable CuFe2O4-catalyzed synthesis of secondary amides from aldehydes and primary amine hydrochloride saltsa
Entry
Aldehyde
Amine salt
Product
Yield (%)b
1
82
2
3
2a
2a
86
68
4
5
2a
2a
72
80
6
7
2a
2a
75
78
74
8
9
2a
2a
76
79
10
11
2a
2a
60
(continued on next page)
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
Table 2 (continued )
Entry
Aldehyde
Amine salt
Product
Yield (%)b
12
13
14
15
2a
78
2a
2a
2a
72
72
70
16
17
2a
2a
70
68
18
2a
2a
2a
75
19
72
20
74
21
1g
78, 75c
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
5
Table 2 (continued )
Entry
Aldehyde
Amine salt
Product
Yield (%)b
22
1g
1a
82
23
86
a
Reaction conditions: aldehyde (1.0 mmol), primary amine HCl salt (1.2 mmol), CaCO3 (1.1 mmol), TBHP (1.1 mmol), CuFe2O4 (10 mol %), CH3CN (2 mL), rt, under nitrogen
atmosphere, 10 h.
b
Isolated yields.
Reaction was carried out by in situ HCl salt formation.
c
69e73% yield (Table 3, entries 1e4). We investigated the reaction
between 3,4,5-trimethoxybenzaldehyde and benzyl amine and
observed no formation of the corresponding product. Generally it is
known that amines undergo N-oxidative decomposition or imine
formation in the presence of TBHP.24 Hence, the use of amine salts
is crucial for this oxidative amidation, as it is less prone to oxidation
by TBHP.24 The use of insoluble base CaCO3 further slows down the
formation of the amine and thus minimizes the undesired amine
oxidation reactions. Further, when the reaction was carried out via
in situ generated HCl salt of benzyl amine21 the corresponding
amide was obtained in yields comparable to that obtained with
commercially available amine salt (Table 2, entry 21). So, all the
reactions were carried out with commercially available amine salts
only.
conditions. As can be seen in Table 1, no yield was observed with
nano Fe3O4, whereas nano CuO (entry 22) afforded 55% of the de-
sired product; clearly indicating that Cu is the active catalytic center
in this reaction. An increase in yield (Table 1, entry 6) with CuFe2O4
nanoparticles shows that iron plays a constructive role, possibly in
the reoxidation of copper during the catalytic cycle. On the basis of
these results, together with literature reports,20,21,25 we propose
a plausible mechanism as shown in Scheme 2. Initially, in the
presence of CaCO3, the amine salt is converted to free amine that
then reacts with the aldehyde and forms hemi-aminal intermediate
(I). Cuþ2 metal center catalysis the heterolytic cleavage of TBHP to
tert-butyl peroxide radical and a proton.25a The tert-butyl peroxide
radical abstracts a proton from hemi-aminal (I) to give radical in-
termediate (II). This intermediate (II), further undergoes oxidation
to form an amide in the presence of CuFe2O4 catalyst via a free-
radical mechanism. The free-radical nature of the reaction is con-
firmed by the addition of 1 equiv of the radical scavenger 2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO), which completely inhibi-
ted the formation of the amide product.
Table 3
Magnetically separable CuFe2O4-catalyzed synthesis of tertiary amides from sec-
ondary amine hydrochloride salts and 3,4,5-trimethoxybenzaldehydea
Entry
1
Amine salt
Product
Yield (%)b
73
2
3
71
69
70
4
Scheme 2. Plausible mechanism for the CuFe2O4-catalyzed oxidative amidation of
aldehydes with amine salts.
a
Reaction conditions: 3,4,5-trimethoxybenzaldehyde (1.0 mmol), secondary
amine hydrochloride salt (1.2 mmol), CaCO3 (1.1 mmol), TBHP (1.1 mmol), CuFe2O4
(10 mol %), CH3CN (2 mL), rt, under nitrogen atmosphere, 10 h.
b
Isolated yields.
After establishing the activity and versatility of the CuFe2O4
catalyst for oxidative amidation of aldehydes, its recyclability was
subsequently tested by recycling and reuse of the catalyst in the
reaction between 4-methylbenzaldehyde and glycine methyl ester
hydrochloride under the optimized reaction conditions. For this,
To understand the role of iron in the present catalytic system,
we carried out two independent reactions with 10 mol % of nano
Fe3O4 and nano CuO catalysts under the optimized reaction
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
after completion of the reaction, the catalyst was separated by
simple decantation using an external magnet, washed with ethyl
acetate, dried under at 50 ꢀC under vacuum to remove residual
solvents and subjected to the next cycle. The CuFe2O4 catalyst could
be reused up to five cycles without any significant loss of catalytic
activity (Fig. 2). Atomic absorption spectroscopy (AAS) was
employed to determine the copper content of CuFe2O4 nano-
particles, and it was found to be 27.30%. The leaching of the metal
after the third cycle was determined by AAS and was found to be
negligible (0.042%).
4.2. General procedure for the oxidative amidation of alde-
hydes with amine hydrochloride salts
To a mixture of primary amine hydrochloride salt (1.2 mmol),
CuFe2O4 (10 mol %) and CaCO3 (1.1 mmol) in acetonitrile (2 mL)
were added aldehyde (1 mmol) and TBHP (70 wt % in H2O,
1.1 mmol) under nitrogen atmosphere, at room temperature. The
reaction vessel was capped and allowed to stir at room temperature
for 10 h. The catalyst was separated with an external magnet after
completion of the reaction. The volatiles were removed under re-
duced pressure, and the crude product was purified by column
chromatography on silica.
4.2.1. Methyl 2-benzamidoacetate (3a).21 Colorless oil. IR (Neat):
3339, 3064, 2954, 1749, 1649, 1538, 1490, 1439, 1371, 1313, 1213,
1183, 1078, 1006, 975, 719, 694 cmꢁ1 1H NMR (300 MHz, CDCl3):
.
d
3.80 (s, 3H), 4.25 (d, 2H, J¼5.0 Hz), 6.79 (br s, 1H), 7.40e7.47 (m,
2H), 7.49e7.54 (m, 1H), 7.76e7.90 (m, 2H). 13C NMR (75 MHz,
CDCl3): d 41.4, 52.1,126.9,128.2,131.5, 133.3,167.7, 170.3. ESI-MS (m/
z): 194 [MþH]þ.
4.2.2. Methyl 2-(4-methylbenzamido)acetate (3b).21 White solid.
Mp 93e95 ꢀC. IR (KBr): 3272, 3076, 2925, 1751, 1625, 1545, 1472,
1324, 1209, 1111, 989, 841, 763, 669 cmꢁ1 1H NMR (300 MHz,
.
CDCl3):
d
2.40 (s, 3H), 3.80 (s, 3H), 4.25 (d, 2H, J¼5.2 Hz), 6.69 (br s,
1H), 7.42 (d, 2H, J¼8.3 Hz), 7.72 (d, 2H, J¼8.3 Hz). 13C NMR (75 MHz,
CDCl3):
d 21.4, 41.6, 52.4, 127.0, 129.2, 130.7, 142.2, 167.3, 170.0. ESI-
MS (m/z): 230 [MþNa]þ.
Fig. 2. Recyclability and reusability of magnetic nano-CuFe2O4 catalyst.
4.2.3. Methyl 2-(4-methoxybenzamido)acetate (3c).21 White solid.
Mp 100e102 ꢀC. IR (KBr): 3270, 2925, 1749, 1642, 1545, 1438, 1328,
3. Conclusion
1265, 1177, 1024, 975, 849, 772, 675 cmꢁ1 1H NMR (300 MHz,
.
CDCl3):
d
3.79 (s, 3H), 3.85 (s, 3H), 4.23 (d, 2H, J¼5.0 Hz), 6.73 (br s,
In conclusion, we have developed a simple and efficient protocol
for the oxidative amidation of aldehydes with amine hydrochloride
salts using magnetically separable CuFe2O4 nanoparticles. This
catalyst has been used for the synthesis of both secondary and
tertiary amides in good to excellent yields. Furthermore, this
method was applied in the oxidative amidation of chiral amine salt
in which the stereochemistry was retained in the resulting amide
product. Easy magnetic separation of the catalyst eliminates the
requirement of catalyst filtration after completion of the reaction,
which is an additional green attribute of this protocol.
1H), 6.92 (d, 2H, J¼8.8 Hz), 7.78 (d, 2H, J¼8.8 Hz). 13C NMR (75 MHz,
CDCl3):
d 41.5, 52.2, 55.2, 113.6, 125.7, 128.8, 162.2, 167.0, 170.6. ESI-
MS (m/z): 224 [MþH]þ.
4.2.4. Methyl 2-(3-methoxybenzamido)acetate (3d). Colorless oil. IR
(Neat): 3336, 3073, 2953, 1749, 1649, 1538, 1486, 1437, 1370, 1312,
1211, 1147, 1041, 1013, 979, 756, 688 cmꢁ1 1H NMR (300 MHz,
.
CDCl3):
d
3.80 (s, 3H), 3.84 (s, 3H), 4.24 (d, 2H, J¼5.1 Hz), 6.76 (br s,
1H), 7.02e7.09 (s, 1H), 7.32e7.36 (m, 2H), 7.37e7.40 (m, 1H). 13C
NMR (75 MHz, CDCl3):
d 41.5, 52.1, 55.1, 112.2, 117.7, 118.8, 129.3,
134.8, 159.5, 167.4, 170.3. ESI-MS (m/z): 224 [MþH]þ. HRMS (ESI,
70 eV): calcd C11H14O4N¼224.09173, found: 224.09041.
4. Experimental section
4.1. General remarks
4.2.5. Methyl 2-(4-isopropylbenzamido)acetate (3e). White solid.
Mp 60e62 ꢀC. IR (KBr): 3265, 3029, 2962, 1758, 1642, 1542, 1458,
1370, 1207, 1181, 1012, 982, 861, 710, 681 cmꢁ1. 1H NMR (300 MHz,
All chemicals were purchased from SigmaeAldrich and S.D Fine
Chemicals, Pvt. Ltd. India and used as received. ACME silica gel
(100e200 mesh) was used for column chromatography and thin-
layer chromatography was performed on Merck-precoated silica
gel 60-F254 plates. The IR spectra of all compounds were recorded
on a PerkineElmer, Spectrum GX FTIR spectrometer. The IR values
are reported in reciprocal centimeters (cmꢁ1). The 1H, 13C NMR
spectra were recorded on a Bruker-Avance 300 MHz Spectrometer.
CDCl3):
d
1.25 (s, 3H), 1.27 (s, 3H), 2.95 (sep, 1H, J¼6.8 Hz), 3.80 (s,
3H), 4.25 (d, 2H, J¼5.0 Hz), 6.70 (br s,1H), 7.29 (d, 2H, J¼8.3 Hz), 7.75
(d, 2H, J¼8.3 Hz). 13C NMR (75 MHz, CDCl3):
d 23.5, 33.9, 41.5, 52.1,
126.4, 127.1, 130.9, 152.8, 167.5, 170.5. ESI-MS (m/z): 236 [MþH]þ.
HRMS (ESI, 70 eV): calcd C13H18O3N¼236.12812, found: 236.12791.
4.2.6. Methyl 2-(3,5-dimethoxybenzamido)acetate (3f). Pale yellow
solid. Mp 98e100 ꢀC. IR (KBr): 3439, 3011, 2924, 1732, 1659, 1592,
1453, 1347, 1201, 1154, 1067, 1014, 968, 842, 763, 675 cmꢁ1. 1H NMR
Chemical shifts (d) are reported in parts per million, using TMS
(
d
¼0) as an internal standard in CDCl3. ESI mass spectra were
(300 MHz, CDCl3):
d
3.81 (s, 3H), 3.83 (s, 6H), 4.24 (d, 2H, J¼5.2 Hz),
recorded on a Finnigan LCQ Advantagemax spectrometer. High-
resolution mass spectra (HRMS) were recorded on QSTAR XL Hy-
brid MS/MS mass spectrometer. All products reported showed 1H
NMR and 13C NMR spectra in agreement with the assigned struc-
tures. The purity of compounds was determined by HRMS and all
tested compounds yielded data consistent with a purity of at least
95% compared with the theoretical values.
6.59 (t, 1H, J¼2.2 Hz), 6.65 (br s, 1H), 6.93 (d, 2H, J¼2.2 Hz). 13C NMR
(75 MHz, CDCl3):
d 41.5, 52.1, 55.2, 103.7, 104.8, 135.5, 160.6, 167.4,
170.3. ESI-MS (m/z): 254 [MþH]þ. HRMS (ESI, 70 eV): calcd for
C12H16O5N¼254.10230, found: 254.10101.
4.2.7. Methyl 2-(3,4,5-trimethoxybenzamido)acetate (3g). White
solid. Mp 109e111 ꢀC. IR (KBr): 3286, 2947, 1751, 1638, 1585, 1464,
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A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
7
1345, 1211, 1128, 1078, 990, 846, 769, 664 cmꢁ1. 1H NMR (300 MHz,
CDCl3):
3.80 (s, 3H), 3.88 (s, 3H), 3.89 (s, 6H), 4.23 (d, 2H, J¼5.1 Hz),
6.75 (br s, 1H), 7.04 (s, 2H). 13C NMR (75 MHz, CDCl3):
41.4, 52.1,
55.8, 60.5, 104.2, 128.5, 140.5, 152.7, 167.1, 170.5. ESI-MS (m/z): 284
[MþH]þ. HRMS (ESI, 70 eV): calcd C13H18O6N¼284.11286, found:
284.11220.
d 41.5, 52.8, 124.5, 125.1, 125.2, 126.2, 127.0, 128.1, 129.9, 130.7, 133.3,
d
133.4, 169.6. 170.2. ESI-MS (m/z): 244 [MþH]þ. HRMS (ESI, 70 eV):
calcd for C14H14O3N¼244.09682, found: 244.09517.
d
4.2.15. Methyl 2-(biphenyl-4-ylcarboxamido)acetate (3o). White
solid. Mp 118e120 ꢀC. IR (KBr): 3327, 2949, 1766, 1647, 1537, 1441,
1379, 1210, 1006, 973, 852, 748, 688 cmꢁ1 1H NMR (300 MHz,
.
4.2.8. Methyl 2-(3-fluorobenzamido)acetate (3h). Colorless oil. IR
CDCl3):
d
3.79 (s, 3H), 4.27 (d, 2H, J¼4.9 Hz), 6.89 (br s, 1H), 7.38 (t,
(Neat): 3343, 3074, 2955, 1750, 1653, 1541, 1483, 1440, 1371, 1221,
1H, J¼7.1 Hz), 7.42e7.48 (m, 2H), 7.57e7.66 (m, 4H), 7.88 (d, 2H,
1136, 1078, 1015, 981, 756, 680 cmꢁ1
.
1H NMR (300 MHz, CDCl3):
J¼8.3 Hz). 13C NMR (75 MHz, CDCl3):
d 41.5, 52.2, 126.9, 127.5, 127.8,
d
3.81 (s, 3H), 4.25 (d, 2H, J¼4.9 Hz), 6.70 (br s, 1H), 7.18e7.24 (m,
1H), 7.39e7.46 (m, 1H), 7.51e7.60 (m, 2H). 13C NMR (75 MHz,
CDCl3):
128.7, 130.3, 132.0, 139.6, 144.3, 167.8, 170.5. ESI-MS (m/z): 292
[MþNa]þ. HRMS (ESI, 70 eV): calcd for C16H15O3NNa¼292.09441,
found: 292.09332.
d
41.5, 52.3, 114.3 (d, J¼22.7 Hz), 118.6 (d, J¼2.7 Hz), 122.5,
130.9 (d, J¼7.2 Hz), 135.5 (d, J¼6.3 Hz), 162.4 (d, J¼247.0 Hz), 166.5,
170.3. ESI-MS (m/z): 234 [MþNa]þ. HRMS (ESI, 70 eV): calcd for
4.2.16. Methyl 2-(thiophene-2-carboxamido)acetate (3p). White
solid. Mp 94e96 ꢀC. IR (KBr): 3093, 2925, 2854, 1726, 1644, 1539,
1440, 1370, 1226, 1160, 1081, 978, 857, 728 cmꢁ1. 1H NMR (300 MHz,
C
10H10O3NFNa¼234.05369, found: 234.05292.
4.2.9. Methyl 2-(4-chlorobenzamido)acetate (3i).21 White solid. Mp
121e123 ꢀC. IR (KBr): 3277, 3088, 2924,1750,1648,1552,1437,1365,
1172, 1091, 1008, 978, 847, 794, 666, 554 cmꢁ1. 1H NMR (300 MHz,
CDCl3):
d
3.79 (s, 3H), 4.22 (d, 2H, J¼5.3 Hz), 6.76 (br s, 1H),
7.04e7.10 (m, 1H), 7.46e7.52 (m, 1H), 7.56e7.59 (m, 1H). 13C NMR
(75 MHz, CDCl3):
d 41.3, 52.1, 127.5, 128.5, 130.3, 137.8, 162.1, 170.3.
CDCl3):
d
3.79 (s, 3H), 4.22 (d, 2H, J¼5.0 Hz), 6.95 (br s, 1H), 7.39 (d,
ESI-MS (m/z): 222 [MþNa]þ. HRMS (ESI, 70 eV): calcd for
C8H9O3NNaS¼222.01954, found: 222.01820.
2H, J¼8.4 Hz), 7.55 (d, 2H, J¼8.4 Hz). 13C NMR (75 MHz, CDCl3):
d
41.5, 52.3, 128.4, 128.6, 131.7, 137.9, 166.5, 170.4. ESI-MS (m/z): 228
[MþH]þ.
4.2.17. Methyl 2-(cyclohexanecarboxamido)acetate (3q).21 White
solid. Mp 102e104 ꢀC. IR (KBr): 3283, 3077, 2930, 2853, 1762, 1642,
1595, 1442, 1367, 1242, 1206, 1180, 1010, 915, 845, 719, 685 cmꢁ1. 1H
4.2.10. Methyl 2-(4-bromobenzamido)acetate (3j).21 White solid.
Mp 108e110 ꢀC. IR (KBr): 3267, 3090, 2945, 1750, 1646, 1558, 1482,
1435,1368,1331,1208,1168,1066,1010, 978, 761, 696 cmꢁ1. 1H NMR
NMR (300 MHz, CDCl3):
d 1.25e1.52 (m, 5H), 1.73e1.95 (m, 5H),
2.09e2.23 (m, 1H), 3.76 (s, 3H), 4.04 (d, 2H, J¼5.0 Hz), 6.01 (br s,
(300 MHz, CDCl3):
d
3.81 (s, 3H), 4.23 (d, 2H, J¼5.1 Hz), 6.76 (br s,
1H). 13C NMR (75 MHz, CDCl3):
d 25.4, 25.5, 29.3, 40.9, 44.9, 52.1,
1H), 7.57 (d, 2H, J¼8.6 Hz), 7.68 (d, 2H, J¼8.6 Hz). 13C NMR (75 MHz,
170.5, 176.3. ESI-MS (m/z): 200 [MþH]þ.
CDCl3):
d 41.6, 52.4, 126.5, 128.6, 131.7, 132.2, 166.5, 170.4. ESI-MS
(m/z): 271 [MþH]þ.
4.2.18. Methyl
2-(2-bromo-3,4,5-trimethoxybenzamido)acetate
(3r). White solid. Mp 115e117 ꢀC. IR (KBr): 3255, 3075, 2932, 1730,
4.2.11. Methyl 2-(4-cyanobenzamido)acetate (3k).21 White solid.
Mp 159e161 ꢀC. IR (KBr): 3284, 3093, 2953, 2233, 1745, 1654, 1552,
1644, 1545, 1483, 1387, 1239, 1105, 1006, 936, 834, 754, 699 cmꢁ1
.
1H NMR (300 MHz, CDCl3):
d 3.81 (s, 3H), 3.88 (s, 3H), 3.90 (s, 3H),
1435, 1370, 1214, 1075, 1012, 970, 863, 770, 699 cmꢁ1
.
1H NMR
3.91 (s, 3H), 4.27 (d, 2H, J¼5.0 Hz), 6.75 (br s, 1H), 7.02 (s, 1H). 13
C
(300 MHz, CDCl3):
d
3.82 (s, 3H), 4.26 (d, 2H, J¼5.0 Hz), 6.83 (br s,
NMR (75 MHz, CDCl3): d 41.7, 52.4, 52.6, 61.0 (2C), 106.4, 108.8,
1H), 7.75 (d, 2H, J¼8.3 Hz), 7.92 (d, 2H, J¼8.3 Hz). 13C NMR (75 MHz,
131.9, 144.8, 151.0, 152.8, 167.0, 169.9. ESI-MS (m/z): 362 [MþH]þ.
HRMS (ESI, 70 eV): calcd for C13H17O6NBr¼362.02338, found:
362.02104.
CDCl3):
d 41.7, 52.3, 115.3, 117.8, 127.7, 132.4, 137.4, 165.6, 170.1. ESI-
MS (m/z): 219 [MþH]þ.
4.2.12. Methyl 2-(4-nitrobenzamido)acetate (3l). Pale yellow solid.
Mp 148e151 ꢀC. IR (KBr): 3304, 3105, 2935, 1744, 1658, 1551, 1491,
4.2.19. Methyl 2-(4,5,6-trimethoxy-biphenyl-2-ylcarboxamido)ace-
tate (3s). Pale yellow solid. Mp 122e124 ꢀC. IR (KBr): 3230, 3054,
2936,1755,1640,1567,1480,1437,1368,1200,1142,1092,1005, 933,
1351, 1214, 1196, 1010, 966, 729, 684 cmꢁ1 1H NMR (300 MHz,
.
CDCl3):
d
3.83 (s, 3H), 4.28 (d, 2H, J¼5.0 Hz), 6.84 (br s, 1H), 7.99 (d,
852, 709 cmꢁ1 1H NMR (300 MHz, CDCl3):
. d 3.57 (s, 3H), 3.65 (s,
2H, J¼8.8 Hz), 8.31 (d, 2H, J¼8.8 Hz). 13C NMR (75 MHz, CDCl3):
3H), 3.84 (d, 2H, J¼4.9 Hz), 3.94 (s, 3H), 3.95 (s, 3H), 5.66 (br s, 1H),
d
41.8, 52.6, 123.8, 128.3, 139.1, 149.1, 165.4, 170.1. ESI-MS (m/z): 239
7.20 (s,1H), 7.32e7.38 (m, 3H), 7.41e7.45 (m, 2H). 13C NMR (75 MHz,
[MþH]þ. HRMS (ESI, 70 eV): calcd for C10H11O5N2¼239.06625,
CDCl3): d 41.5, 52.2, 126.9, 127.5, 127.8, 128.7, 130.3, 132.0, 139.6,
found: 239.06723.
144.3, 167.8, 170.5. ESI-MS (m/z): 360 [MþH]þ. HRMS (ESI, 70 eV):
calcd for C19H22O6N¼360.14416, found: 360.14485.
4.2.13. Methyl 2-(4-chloro-3-nitrobenzamido)acetate (3m). Pale
yellow solid. Mp 125e127 ꢀC. IR (KBr): 3327, 3084, 2925, 2111, 1740,
1642, 1546, 1478, 1404, 1364, 1223, 1113, 1042, 970, 843, 743,
4.2.20. Methyl 2-(4,40,5,6-tetramethoxy-biphenyl-2-ylcarboxamido)
acetate (3t). Pale yellow solid. Mp 127e129 ꢀC. IR (KBr): 3241, 3075,
2927, 1747, 1643, 1565, 1485, 1400, 1347, 1210, 1179, 1094, 1027, 993,
641 cmꢁ1 1H NMR (300 MHz, CDCl3):
. d 3.82 (s, 3H), 4.25 (d, 2H,
J¼5.1 Hz), 7.10 (br s, 1H), 7.46 (d, 1H, J¼8.3 Hz), 7.97 (dd, 1H,
846, 739 cmꢁ1. 1H NMR (300 MHz, CDCl3):
d 3.576 (s, 3H), 3.66 (s,
J¼2.0 Hz, 8.3 Hz), 8.33 (d, 1H, J¼2.0 Hz). 13C NMR (75 MHz, CDCl3):
3H), 3.85 (s, 3H), 3.88 (d, 2H, J¼5.0 Hz), 3.92 (s, 3H), 3.94 (s, 3H),
d
41.7, 52.6, 124.3, 130.4, 131.4, 132.2, 133.2, 147.7, 164.2, 170.2. ESI-
5.74 (br s, 1H), 6.99 (d, 2H, J¼8.3 Hz), 7.18 (s, 1H), 7.27 (d, 2H,
MS (m/z): 295 [MþNa]þ. HRMS (ESI, 70 eV): calcd for C10H9O5N2
ClNa¼295.00922, found: 295.00885.
J¼8.3 Hz). 13C NMR (75 MHz, CDCl3):
d 41.7, 52.1, 55.1, 56.0, 60.8,
-
60.9, 108.2, 113.9, 126.9, 127.4, 130.1, 131.0, 144.3, 151.3, 152.6, 159.1,
168.3, 169.5. ESI-MS (m/z): 390 [MþH]þ. HRMS (ESI, 70 eV): calcd
for C20H24O7N¼390.15473, found: 390.15568.
4.2.14. Methyl 2-(2-naphthamido)acetate (3n). White solid. Mp
94e96 ꢀC. IR (KBr): 3318, 3046, 2925, 1746, 1643, 1543, 1435, 1363,
1211, 1068, 961, 898, 786, 648 cmꢁ1
.
1H NMR (300 MHz, CDCl3):
4.2.21. N-Benzyl-3,4,5-trimethoxybenzamide (3u). White solid. Mp
120e122 ꢀC. IR (KBr): 3303, 2925, 2853, 1730, 1626, 1581, 1498,
d
3.81 (s, 3H), 4.32 (d, 2H, J¼5.3 Hz), 6.85 (br s, 1H), 7.42e7.47 (m,
1H), 7.50e7.57 (m, 2H), 7.65e7.68 (m, 1H), 7.84e7.88 (m, 1H), 7.92
1458, 1331, 1235, 1127, 1077, 989, 840, 751, 696 cmꢁ1 1H NMR
.
(d, 1H, J¼8.2 Hz), 8.36 (d, 1H, J¼8.2 Hz). 13C NMR (75 MHz, CDCl3):
(300 MHz, CDCl3):
d
3.85 (s, 6H), 3.86 (s, 3H), 4.61 (d, 2H, J¼5.6 Hz),
Please cite this article in press as: Suresh Kumar, A.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.01.051

8
A. Suresh Kumar et al. / Tetrahedron xxx (2014) 1e9
6.67 (br s, 1H), 7.04 (s, 2H), 7.27e7.37 (m, 5H). 13C NMR (75 MHz,
References and notes
CDCl3):
d 43.6, 55.7, 60.4, 104.3, 126.9, 127.3, 128.2, 129.3, 138.2,
140.3, 152.7, 166.9. ESI-MS (m/z): 302 [MþH]þ. HRMS (ESI, 70 eV):
calcd for C17H20O4N¼302.13868, found: 302.13927.
1. (a) Trost, B. M. Acc. Chem. Res. 2002, 35, 695; (b) Li, C.-J.; Trost, B. M. Proc. Natl.
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Chemistry: Theory and Practice; Oxford University: Oxford, UK, 1998; (c) Jenck, J.
F.; Agterberg, F.; Droescher, M. J. Green Chem. 2004, 6, 544.
4.2.22. N-(2-Chloroethyl)-3,4,5-trimethoxybenzamide
yellow solid. Mp 116e118 ꢀC. IR (KBr): 3301, 2925, 2854, 1715, 1632,
1584, 1462, 1336, 1235, 1129, 992, 850, 767, 653 cmꢁ1 1H NMR
(300 MHz, CDCl3): 3.73e3.77 (m, 2H), 3.78e3.81 (m, 2H), 3.89 (s,
3H), 3.91 (s, 6H), 6.65 (br s, 1H), 7.02 (s, 2H). 13C NMR (75 MHz,
(3v). Pale
€
3. (a) Lu, A.-H.; Salabas, E. L.; Schuth, F. Angew. Chem., Int. Ed. 2007, 46, 1222; (b)
.
Zhu, Y.; Stubbs, L. P.; Ho, F.; Liu, R.; Ship, C. P.; Maguire, J. A.; Hosmane, N. S.
ChemCatChem 2010, 2, 365; (c) Polshettiwar, V.; Varma, R. S. Org. Biomol. Chem.
2009, 7, 37.
d
4. (a) Reziq, R. A.; Alper, H.; Wang, D. S.; Post, M. L. J. Am. Chem. Soc. 2006, 128,
5279; (b) Chouhan, G.; Wang, D. S.; Alper, H. Chem. Commun. 2007, 4809; (c)
Hara, T.; Kaneta, T.; Mori, K.; Mitsudome, T.; Mizugaki, T.; Ebitani, K.; Kaneda,
K. Green Chem. 2007, 9, 1246; (d) Jin, M. J.; Lee, D. H. Angew. Chem., Int. Ed.
2010, 49, 1119; (e) Yang, H. Q.; Wang, Y.; Qin, Y.; Chong, Y.; Yang, Q.; Li, G.;
Zhang, L.; Li, W. Green Chem. 2011, 13, 1352; (f) Garrido, S. E. G.; Francos, J.;
Cadierno, V.; Basset, J.-M.; Polshettiwar, V. ChemSusChem 2011, 4, 104; (g) Lee,
J.; Chung, J.; Byun, S. M.; Kim, B. M.; Lee, C. Tetrahedron 2013, 69, 5660; (h)
Sheykhana, M.; Mohammadnejad, H.; Akbari, J.; Heydari, A. Tetrahedron Lett.
2012, 53, 2959.
CDCl3):
d 41.7, 43.7, 56.2, 60.8, 104.4, 129.3, 140.9, 153.0, 167.3. ESI-
MS (m/z): 296 [MþNa]þ. HRMS (ESI, 70 eV): calcd for C12H16O4N-
ClNa¼296.06556, found: 296.06556.
4.2.23. (S)-Methyl-2-benzamido-3-methylbutanoate (3w).21 White
solid. Mp 114e116 ꢀC. IR (KBr): 3347, 2967, 2872, 1739, 1641, 1521,
1489, 1360, 1203, 1150, 994, 894, 733 cmꢁ1 1H NMR (300 MHz,
.
5. (a) Wang, X.; Dou, P. P.; Zhao, P.; Zhao, C. M.; Ding, Y.; Xu, P. ChemSusChem 2009,
2, 947; (b) Lee, J.; Lee, Y.; Youn, J. K.; Na, H. B.; Yu, T.; Kim, H.; Lee, S. M.; Koo, Y. M.;
Kwak, J. H.; Park, H. G.; Chang, H. N.; Hwang, M.; Park, J. G.; Kim, J.; Hyeon, T. Small
2008, 4, 143.
6. (a) Zabicky, J. In The Chemistry of Amides; Wiley-Interscience: New York, NY,
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Alagirusami, R. In Polyesters and Polyamides; CRC: Boca Raton, 2008; (d) Jo-
hansson, I. Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley &
Sons: New York, NY, 2004, Vol. 2, p 442.
7. (a) Carey, J. S.; Laffan, D.; Thomson, C.; Williams, M. T. Org. Biomol. Chem. 2006,
4, 2337; (b) Dugger, R. W.; Ragan, J. A.; Ripin, D. H. B. Org. Process Res. Dev. 2005,
9, 253.
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Zhang, T. Y. Green Chem. 2007, 9, 411.
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Falque, V. Tetrahedron 2005, 61, 10827; (c) Valeur, E.; Bradley, M. Chem. Soc. Rev.
2009, 38, 606; (d) Larock, R. C. Comprehensive Organic Transformations; VCH:
New York, NY, 1999.
10. (a) Saxon, E.; Bertozzi, C. R. Science 2000, 287, 2007; (b) Nilsson, B. L.; Kiessling, L. L.;
Raines, R. T. Org. Lett. 2000, 2, 1939; (c) Damkaci, F.; DeShong, P. J. Am. Chem. Soc.
2003, 125, 4408.
11. (a) Cho, S.; Yoo, E.; Bae, I.; Chang, S. J. Am. Chem. Soc. 2005, 127, 16046; (b)
Cassidy, M. P.; Raushel, J.; Fokin, V. V. Angew. Chem., Int. Ed. 2006, 45, 3154.
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CDCl3):
(dd, 1H, J¼4.9 Hz, 8.6 Hz), 6.67 (d, 1H, J¼7.7 Hz), 7.35e7.61 (m, 3H),
7.67e7.95 (m, 2H). 13C NMR (75 MHz, CDCl3):
17.8, 18.8, 31.4, 52.0,
d
1.00 (t, 6H, J¼6.9 Hz), 2.15e2.39 (m, 1H), 3.78 (s, 3H), 4.79
d
57.3, 126.9, 128.4, 131.5, 133.9, 176.9, 172.5. ESI-MS (m/z): 236
25
24
[MþH]þ. [
ee¼98%.
a
]
þ42.3 (c 1, CHCl3) [lit.21
[
a
]
þ43.0 (c 1, CHCl3)].
D
D
4.2.24. 3,4,5-Trimethoxy-N,N-dimethylbenzamide (5a).26 Light yel-
low oil. IR (neat): 2931, 1721,1632,1585,1494, 1411, 1327,1237,1168,
1127, 1005, 970, 862, 766 cmꢁ1. 1H NMR (300 MHz, CDCl3):
d
3.02
(br s, 3H), 3.11 (br s, 3H), 3.86 (s, 3H), 3.87 (s, 6H), 6.65 (s, 2H). 13
C
NMR (75 MHz, CDCl3):
d 35.3, 39.6, 56.1, 60.8, 104.3, 131.5, 138.9,
153.1, 171.3. ESI-MS (m/z): 240 [MþH]þ.
4.2.25. N,N-Diethyl-3,4,5-trimethoxybenzamide (5b).26 Light yellow
oil. IR (neat): 2933, 1724, 1630, 1584, 1461, 1413, 1332, 1236, 1163,
1127, 1007, 927, 819, 765 cmꢁ1. 1H NMR (300 MHz, CDCl3):
d
1.20 (br
s, 6H), 3.41 (br d, 4H), 3.86 (s, 3H), 3.87 (s, 6H), 6.60 (s, 2H). 13C NMR
(75 MHz, CDCl3):
d 12.8, 14.2, 39.3, 43.2, 56.1, 60.8, 103.5, 132.5,
138.6, 153.1, 170.9. ESI-MS (m/z): 268 [MþH]þ.
4.2.26. N-3,4,5-Tetramethoxy-N-methylbenzamide
(5c). Colorless
oil. IR (neat): 2926, 2854, 1762, 1639, 1582, 1460, 1414, 1374, 1238,
1126, 1003, 938, 858, 747 cmꢁ1. 1H NMR (300 MHz, CDCl3):
3.36 (s,
3H), 3.60 (s, 3H), 3.89 (s, 9H), 6.98 (s, 2H). 13C NMR (75 MHz, CDCl3):
d
d
33.9, 56.1, 60.8, 61.0, 105.8, 128.9, 140.0, 152.6, 169.2. ESI-MS (m/z):
14. Tillack, A.; Rudloff, I.; Beller, M. Eur. J. Org. Chem. 2001, 523.
15. Park, S.; Choi, Y.; Han, H.; Yang, S. H.; Chang, S. Chem. Commun. 2003, 1936.
16. Owston, N. A.; Parker, A. J.; Williams, J. J. M. Org. Lett. 2007, 9, 73.
17. Beller, M.; Cornils, B.; Frohning, C. D. J. Mol. Catal. A: Chem. 1995, 104, 17.
18. (a) Ali, B. E.; Tijani, J. Appl. Organomet. Chem. 2003, 17, 921; (b) Knapton, D. J.;
Meyer, T. Y. Org. Lett. 2004, 6, 687; (c) Uenoyama, Y.; Fukuyama, T.; Nobuta, O.;
Matsubara, H.; Ryu, I. Angew. Chem., Int. Ed. 2005, 44, 1075.
19. (a) Lin, Y.-S.; Alper, H. Angew. Chem., Int. Ed. 2001, 40, 779; (b) Uozumi, Y.; Arii, T.;
Watanabe, T. J. Org. Chem. 2001, 66, 5272; (c) Nanayakkara, P.; Alper, H. Chem.
Commun. 2003, 2384.
256 [MþH]þ. HRMS (ESI, 70 eV): calcd for C12H18O5N¼256.11850,
found: 256.11727.
4.2.27. (2-Ethylmorpholino)(3,4,5-trimethoxyphenyl)methanone
(5d). Colorless oil. IR (neat): 2926, 2853, 1723, 1633, 1583, 1462,
1419, 1328, 1232, 1127, 1103, 966, 862, 764 cmꢁ1. 1H NMR (300 MHz,
CDCl3):
d 0.91e1.03 (m, 3H), 1.55 (br s, 3H), 1.82 (br s, 2H), 3.45 (br d,
20. Yoo, W.-J.; Li, C.-J. J. Am. Chem. Soc. 2006, 128, 13064.
21. Ghosh, S. C.; Ngiam, J. S. Y.; Chai, C. L. L.; Seayad, A. M.; Dang, T. T.; Chen, A. Adv.
Synth. Catal. 2012, 354, 1407 J. Org. Chem. 2012, 77, 8007.
4H), 3.86 (s, 3H), 3.87 (s, 6H), 6.62 (s, 2H). 13C NMR (75 MHz,
CDCl3): d 9.4, 26.0, 46.6, 47.8, 56.1, 60.7, 66.4, 77.2,104.2,130.6,139.1,
153.2, 169.9. ESI-MS (m/z): 310 [MþH]þ. HRMS (ESI, 70 eV): calcd
for C16H24O5N¼310.16545, found: 310.16401.
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Acknowledgements
A.S.K. and B.T.R. thank University Grant Commission (UGC), New
Delhi for the award of Senior and Junior Research Fellowship (SRF-
JRF), respectively.
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