Silica nanoparticles as a high efficient catalyst for the one-pot synthesis of 3-oxo-3-phenylpropanamid derivatives from isocyanides, phenylacetaldehyde and secondary amines

Article abstract of DOI:10.3906/kim-1111-1

Reaction of an isocyanide with an iminium ion intermediate, formed by reaction between 2-oxo-2-phenylacetaldehyde and a secondary amine in the presence of silica nanoparticles, proceeds smoothly at room temperature to afford ketoamide derivatives in high

Full text of DOI:10.3906/kim-1111-1

Turk J Chem
36 (2012) , 467 – 476.
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˙
c
ꢀ TUBITAK
doi:10.3906/kim-1111-1
Silica nanoparticles as a high efficient catalyst for the
one-pot synthesis of 3-oxo-3-phenylpropanamid
derivatives from isocyanides, phenylacetaldehyde and
secondary amines
Ali RAMAZANI1,∗, Kourosh DASTANRA1, Fatemeh ZEINALI NASRABADI1,
Zahra KARIMI1, Morteza ROUHANI2, Mehdi HOSSEINI1
1Department of Chemistry, University of Zanjan, PO Box 45195-313, Zanjan-IRAN
e-mail: aliramazani@yahoo.com
2Young Researchers Club, Zanjan Branch, Islamic Azad University, Zanjan-IRAN
Received: 01.11.2011
Reaction of an isocyanide with an iminium ion intermediate, formed by reaction between 2-oxo-2-
phenylacetaldehyde and a secondary amine in the presence of silica nanoparticles, proceeds smoothly at
room temperature to afford ketoamide derivatives in high yields.
Key Words: Silica nanoparticles, multicomponent reaction, isocyanide, 2-oxo-2-phenylacetaldehyde, sec-
ondary amine, iminium ion
Introduction
Recently, multicomponent reactions (MCRs) have become important tools in modern preparative synthetic
chemistry because these reactions increase the efficiency by combining several operational steps without any
isolation of intermediates or changes of the conditions.1− 6 Among the multicomponent reactions known to
date, the most valuable reactions are those based on isocyanides. Isocyanide-based multicomponent reactions
(abbreviated to IMCRs by Ugi and Dmling) by virtue of their synthetic potential, their inherent atom efficiency,
convergent nature, ease of implementation, and molecular diversity have attracted much attention because of
the advantages that they offer in the field of combinatorial chemistry.7,8
∗Corresponding author
467

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
In recent years, nanoparticles (NPs) have attracted tremendous attention in catalysis because of their
improved efficiency under mild and environmentally benign conditions in the context of ecological (green)
synthesis9,10 Due to their enormously large and highly reactive surface area, NPs have the potential to exhibit
superior catalytic activity in comparison to bulk counterparts11,12 The methods for the synthesis of β-keto
amides have been rarely reported in the literature.13−15 These protocols are multi-step in nature and usually
perform under harsh reaction conditions.13−15 In this article, we wish to report a simple and practical procedure
for the preparation of ketoamide derivatives through a one-pot multicomponent condensation reaction (MCR)
in the presence of silica nanoparticles (silica NPs, ca. 42 nm).
Experimental
Starting materials and solvents were obtained from Merck (Germany) and Fluka (Switzerland) and were used
without further purification. TLC and NMR spectroscopy were used to follow the reactions. Melting points
were measured on an Electrothermal 9100 apparatus and are uncorrected. IR spectra were measured on a
Jasco 6300 FTIR spectrometer. 1 H and 13 CNMR spectra were measured (CDCl3 solution) with a BRUKER
DRX-250 Avance spectrometer at 250.0 and 62.5 MHz, respectively. Elemental analyses were performed using
a Heraeus CHN-O-Rapid analyzer. Preparative layer chromatography (PLC) plates were prepared from Merck
silica gel (F254) powder.
General procedure for the preparation of compounds 4
Silica nanoparticles (0.1 g) were added to a mixture of 2-oxo-2-phenylacetaldehyde (2) (1 mmol), secondary
aminederivative 1 (1 mmol), and isocyanide 3 (1 mmol) at r.t., followed by 4 h of stirring. Residue was purified
by preparative layer chromatography (PLC) (silica gel (F254) powder; petroleum ether-ethyl acetate (4:1)).
The characterization data of the compounds are given below.
N-(tert-butyl)-2-(dibenzylamino)-3-oxo-3-phenylpropanamide (4a)
Yellow viscose oi, (yield: 92%). IR (neat): v = 3341 (NH), 2923, 2861, 1712, 1653, 1530, 1438, 1223 cm−1
.
1 HNMR (250 MHz, CDCl3) δ (ppm): 1.33 (s, 9H, 3CH3), 3.86 and 4.44 (ABq , 4H, 2CH2 of benzyl, J = 14.0
Hz), 4.91 (s, 1H, CH), 6.84 (s, 1H, NH), 7.09-8.72 (m, 15H, CHarom). 13 CNMR (62.5 MHz, CDCl3) δ (ppm):
28.67 (3CH3), 51.40 (C), 55.13 (2CH2), 66.46 (CH), 127.47, 128.49, 128.51, 128.59, 128.71, 133.26, 138.58
(15CH of arom, 128.93, 129.89, 137.58 (3C of aro), 167.85 (CO of amide), 198.78 (CO of ketone). Analysis of
C27 H30 N2 O2 (414.54). (% calculation/found): C: 78.23/78.28, H: 7.29/7.24, N: 6.76/6.72.
2-[benzyl(ethyl)amino]-N-( tert-butyl)-3-oxo-3-phenylpropanamide (4b)
Yellow viscose oi, (yield: 93%). IR (neat): v = 3456, 3069, 2927, 1718, 1638, 1449, 1269 cm−1 1 HNMR (250
.
MHz, CDCl3) δ (ppm): 1.06 (t, 3H, CH3), 1.31 (s, 9H, 3CH3), 2.82 (q, 2H, CH2), 3.86 and 3.99 (ABq , 2H,
CH2 of benzyl, J = 14.0 Hz), 4.96 (s, 1H, CH), 6.96 (s, 1 H, NH), 7.13-8.91 (m, 10H, CHarom). 13 CNMR
(62.5 MHz, CDCl3) δ (ppm): 23.00 (CH3), 28.57 (3CH3), 45.50, 48.00 (2CH2), 55.00 (C), 68.56 (CH), 127.47,
468

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
128.49, 128.51, 128.59, 128.71, 138.55 (10CH of arom, 129.89, 137.58 (2C of aro), 161.89 (CO of amide), 198.75
(CO of ketone). Analysis of C22 H28 N2 O2 (352.22). (% calculation/found): C: 74.97/74.93, H: 8.01/8.06, N:
7.95/7.90.
2-[benzyl(methyl)amino]-N-(tert-butyl)-3-oxo-3-phenylpropanamide (4c)
Yellow viscose oi, (yield: 92%). IR (neat): v = 3356, 3059, 2967, 1719, 1648, 1434, 1243 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 1.33 (s, 9H, 3CH3), 2.35 (s, 3H, CH3), 3.74 (s, 2H, br, CH2 of benzyl), 4.76
(s, 1H, CH), 7.00 (s, 1H, NH), 7.32-8.03 (m, 10H, CHarom). 13 CNMR (62.5 MHz, CDCl3) δ (ppm): 28.53
(3CH3), 39.37 (CH3), 51.10 (C), 59.35 (CH2), 73.46 (CH), 128.50, 128.64,128.70, 128.87, 133.60 (10CH of
arom), 128.19, 137.12 (2C of aro), 169.85 (CO of amide), 195.68 (CO of ketone). Analysis of C21 H26 N2 O2
(338.20) (% calculation/found): C: 74.52/74.57, H: 7.74/7.69, N: 8.28/8.33
2-(dibenzylamino)- N-(2,6-dimethylphenyl)-3-oxo-3-phenylpropanamid (4d)
Yellow viscose oi, (yield: 95%). IR (neat): v = 3332, 2989, 2927, 1712, 1656, 1460, 1233 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 2.25 (s, 6H, 2CH3), 3.86 and 4.15 (ABq , 4H, 2CH2 of benzyl, J = 13.7 Hz),
5.20 (s, 1H, CH), 7.10-7.77 (m, 18H, CHarom), 8.49 (s, 1H, NH). 13 CNMR (62.5 MHz, CDCl3) δ (ppm):
18.88 (2CH3), 55.03 (2CH2), 65.97(CH), 127.66, 128.31, 128.58, 128.65, 128.88 , 129.02, 135.20, 137.99 (18CH
of arom), 127.32, 133.57, 133.64, 136.46, 137.27 (6C of aro), 168.50 (CO of amide), 198.20 (CO of ketone).
Analysis of C31 H30 N2 O2 (462.58). (% calculation/found): C: 80.49/80.44, H: 6.54/6.50, N: 6.06/6.11
2-[benzyl(ethyl)amino]- N-(2,6-dimethylphenyl)-3-oxo-3-phenylpropanamide (4e)
Yellow viscose oi, (yield: 90%). IR (neat): v = 3346, 3082, 2978, 1711, 1642, 1434, 1220 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 1.25 (t, 3H, CH3), 2.29 (s, 6H, 2CH3), 2.77 (q, 2H, CH2), 3.91 (s, br, 2H, CH2
of benzyl), 4.27 (s,1H, CH), 7.14(s,1H, NH), 7.31-7.99 (m,13H, CHarom). 13 CNMR (62.5 MHz, CDCl3) δ
(ppm): 21.08 (2CH3), 24.23 (CH3), 49.45, 56.13 (2CH2), 63.57(CH), 127.66, 127.84, 128.52, 128.87, 129.02,
129.46, 133.27, 137.89 (13CH of arom, 127.02, 135.07, 137.06, 141.27 (4C of aro), 159.22 (CO of amide), 194.68
(CO of ketone). Analysis of C26 H28 N2 O2 (400.22). (% calculation/found): C: 77.97/77.92, H: 7.05/7.10, N:
6.99/6.94.
2-[3a,6-dihydro-1H-benzo[de]isoquinolin-2(3H)-yl]-3-oxo-3-phenyl-N-(1,1,3,3-tetramethylbutyl)
propanamide (4f)
Yellow viscose oi, (yield: 90%). IR (neat): v = 3361, 2959, 2917, 1717, 1679, 1446, 1218 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 0.96 (s, 9H, 3CH3), 1.02 (s, 6H, 2CH3), 1.41 (s, 2H, CH2), 3.84 and 4.02
(ABq , 4H, 2CH2 of benzyl, J = 14.3 Hz), 4.92 (s, 1H, CH), 6.92 (s, 1H, NH), 7.13-7.71 (m, 15H, CHarom).
13 CNMR (62.5 MHz, CDCl3) δ (ppm): 28.67, 31.45 (5CH3), 29.11, 31.57 (2C), 53.65, 55.13 (2CH2), 65.50
(CH), 127.47, 128.37, 128.50, 128.56, 128.68, 128.79, 128.93, 130.10 (9CH of arom), 127.72, 133.35, 138.50(3C of
aro), 167.52 (CO of amide), 199.28 (CO of ketone). Analysis of C31 H38 N2 O2 (470.29). (% calculation/found):
C: 79.11/79.16, H: 8.14/8.09, N: 5.95/5.90
469

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
2-[benzyl(methyl)amino]-N-cyclohexyl-3-oxo-3-phenylpropanamide (4g)
Yellow viscose oi, (yield: 92%). IR (neat): v = 3416, 3069, 2925, 1723, 1642, 1434, 1243 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 1.25-1.83 (m, 10H, CH2 of cyclohexyl), 2.95 (s, 3H, CH3), 3.73 (s, br, 2H, CH2
of benzyl), 4.29 (m, 1H, CH of cyclohexyl), 4.35(s, 1H, CH), 7.04 (s, 1H, NH), 7.33-8.01 (m, 10H, CHarom).
13 CNMR (62.5 MHz, CDCl3) δ (ppm): 24.90, 25.00, 26.20 (5CH2 of cyclohexyl), 33.15 (CH3), 48.05 (CH
of cyclohexyl), 57.12 (CH2), 63.50(CH), 128.00, 128.57, 128.60, 128.64, 128.69, 129.15 (10CH of arom, 129.72,
131.75(2C of aro), 175.32 (CO of amide), 196.68 (CO of ketone). Analysis of C23 H28 N2 O2 (364.22). (%
calculation/found): C: 75.79/75.73, H: 7.74/7.79, N: 7.69/7.64.
2-[3a,6-dihydro-1H-benzo[de]isoquinolin-2(3H)-yl]-N-cyclohexyl-3-oxo-3-phenylpropanamide (4h)
Yellow viscose oi, (yield: 91%). IR (neat): v = 3372, 3084, 2976, 1713, 1636, 1461, 1271 cm−1 1 HNMR (250
.
MHz, CDCl3) δ (ppm): 0.83-1.63 (m, 10H, CH2 of cyclohexyl), 3.84 and 4.07 (ABq , 2H, CH2 of benzyl, J
= 14.3 Hz), 4.50 (m, 1H, CH of cyclohexyl), 4.92(s, 1 H, CH), 6.92 (s, 1H, NH), 7.13-7.71 (m, 15H, CHarom).
13 CNMR (62.5 MHz, CDCl3) δ (ppm): 30.30, 31.02, 31.46 (5CH2 of cyclohexyl), 52.18 (CH of cyclohexyl),
55.11 (2CH2), 65.48(CH), 127.50, 128.19, 128.45, 128.61, 129.84, 138.50 (10CH of arom, 127.30, 129.25(3C of
aro), 167.82 (CO of amide), 199.38 (CO of ketone). Analysis of C29 H32 N2 O2 (440.25). (% calculation/found):
C: 79.06/79.11, H: 7.32/7.38, N: 6.36/6.42.
2-[benzyl(methyl)amino]-3-oxo-3-phenyl-N-(1,1,3,3-tetramethylbutyl)propanamide (4i)
Yellow viscose oi, (yield: 89%). IR (neat): v = 3365, 3058, 2968, 1718, 1668, 1457, 1263 cm−1
.
1 HNMR
(250 MHz, CDCl3) δ (ppm): 1.24 (s, 9H, 3CH3), 1.58 (s, 6H, 2CH3), 2.84 (s, 2H, CH2), 3.06 (s, 3H, CH3),
4.20 and 4.40 (ABq , 2H, CH2 of benzyl), 4.74 (s, 1H, CH), 6.92(s, 1H, NH), 7.31-7.98 (m, 15H, CHarom).
13 CNMR (62.5 MHz, CDCl3) δ (ppm): 26.47, 30.22 (5CH3), 22.11, 31.46 (2C), 40.06 (CH3), 53.35, 55.01
(2CH2), 67.50(CH), 127.50, 128.19, 128.45, 128.61, 129.84, 138.50 (10CH of arom, 127.30, 129.25(2C of aro),
165.52 (CO of amide), 198.28 (CO of ketone). Analysis of C25 H34 N2 O2 (394.26). (% calculation/found): C:
76.10/76.05, H: 8.69/8.74 N: 7.10/7.15
2-[benzyl(methyl)amino]-N-(2,6-dimethylphenyl)-3-oxo-3-phenylpropanamide (4j)
Yellow viscose oi, (yield: 88%). IR (neat): v = 3374, 3092, 2977, 1719, 1638, 1444, 1225 cm−1
MHz, CDCl3) δ (ppm): 2.30 (s, 6H, 2CH3), 2.63 (s, 3H, CH3), 3.09 (s, br, 2H, CH2 of benzyl), 4.92 (s, 1H,
CH), 7.14 (s,1H, NH), 7.30-7.99 (m, 10H, CHarom
13 CNMR (62.5 MHz, CDCl3) δ (ppm): 20.06 (2CH3),
.
1 HNMR (250
)
39.11(CH3), 54.23 (CH2), 67.94 (CH), 124.67, 127.06, 128.21, 128.40, 128.65, 128.98 , 129.00, 132.20 (13CH of
arom), 127.35, 134.62, 136.43, 138.22 (4C of aro), 165.50 (CO of amide), 196.27 (CO of ketone). Analysis of
C25 H26 N2 O2 (386.20). (% calculation/found): C: 77.69/77.75, H: 6.78/6.83, N: 7.25/7.20.
470

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
Results and discussion
As part of our ongoing program to develop efficient and robust methods for the preparation of organic
compounds,16−4 4 we sought to develop an efficient route for the one-pot synthesis of sterically congested
ketoamide derivatives 4 from simple and readily available alkyl isocyanides 3, secondary amine 1, and 2-oxo-
2-phenylacetaldehyde (2) (Scheme 1 and Table 1). The reaction occurs smoothly in the presence ofsilica NPs
at ambient temperature, to produce ketoamide derivatives 4 inexcellent yields (Table 1). In the absence of
silicaNPs, the reactions were not conducted in the compounds 4 and in all cases several products were observed
(based on TLC investigations).
O
O
H
N
R'
SiO2 NP
r.t., 4 h
+
+
R'
N
C
Bn
R
HN
Bn
H
N
R
O
3
2
1
O
4
Scheme 1. Three-component synthesis of ketoamide derivatives 4 in the presence of silica nanoparticles.
Silica NPs were prepared by thermal decomposition of rice hulls.45 The results from X-ray diffraction
(XRD) showed that the sample was silica NP as indicated by broadened peaks around 2θ = 22◦ (Figure 1).
The morphology and grain size of the silica NP was investigated by scanning electron microscopy (SEM) (Figure
2).43,44
Figure 1. X-ray diffraction pattern of the synthesized of silica nanoparticles.
471

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
Table. Synthesis of ketoamide derivatives 4a-j in the presence of silica nanoparticles.
4
a
R
R'
Product
Yield (%)
92
O
O
H3C
CH3
CH3
N
H
Benzyl
tert-Butyl
N
Ph
Ph
O
O
H3C
CH3
N
H
CH3
b
c
Et
Me
tert-Butyl
tert-Butyl
93
92
95
N
Ph
CH3
O
O
H3C
CH3
N
H
CH3
N
CH3
Ph
O
H3C
O
N
H
d
Benzyl
2,6-Dimethylphenyl
N
CH3
Ph
Ph
H3C
O
O
N
H
e
f
Et
2,6-Dimethylphenyl
90
90
N
CH3
Ph
CH3
CH3
O
O
H3C
CH3
-
1,1,3,3
H3C
CH3
Benzyl
N
H
Tetramethylbutyl
N
Ph
Ph
472

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
Table. Continued.
4
g
R
R'
Product
Yield (%)
92
O
O
Me
Cyclohexyl
N
H
N
CH3
Ph
O
O
h
Benzyl
Cyclohexyl
91
89
88
N
H
N
Ph
Ph
CH3
O
O
H3
C
1,1,3,3 -
CH3
i
Me
H3C
N
H
CH3
Tetramethylbutyl
N
CH3
Ph
O
H3C
O
j
Me
2,6-Dimethylphenyl
N
H
N
CH3
CH3
Ph
a
Yield of isolated 4
The structures of the products were elucidated from their IR, 1 H-NMR, 13 C-NMR, and elemental
analyses. For example, the 1 H-NMR spectrum of 4a consisted of a singlet for 3CH3 of tert-buytl (δ = 1.33
ppm), and an AB quartet for the H-atoms of CH2 Ph (δ = 3.86 and 4.44 ppm, J = 14.0 Hz), a singlet for CH (δ
= 4.91), and a singlet for NH (δ = 6.84). The aryl groups exhibited characteristic signals in the aromatic region
of the spectrum. The 1 H-decoupled 13 C-NMR spectrum of 4a showed 16 distinct signals; partial assignment
of these signals is given in the experimental section. The 1 H- and 13 C-NMR spectra of compounds 4b-j were
similar to those of 4a, except for the aromatic moiety, and the alkyl groups, which exhibited characteristic
signals with appropriate chemical shifts.
Although we have not established the mechanism of the reaction in an experimental manner, a plausible
reaction sequence that accounts for the formation of 4 is shown in Scheme 2. Thus condensation of 2-oxo-
473

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
2-phenylacetaldehyde (2) and secondary amine 1 would give the iminium ion intermediate 5, which would
react with the alkyl isocyanide 3 to afford intermediate 6. The ionic intermediate 6was unstable and quickly
converted to a compound 4 (Scheme 2).
Figure 2. SEM of the synthesized of silica nanoparticles.
O
R
N
O
Bn
R
O
Bn
N
H
OH
O
H
1 +
2
H
H
O
O
Bn
R
Bn
R
O
O
N
N
R'
3
OH
NH
Bn
OH
OH
H
N
R
N
O
R'
O
6
5
4
Scheme 2. Proposed mechanism for the formation of ketoamide derivatives 4 in the presence of silica nanoparticles.
474

Silica nanoparticles as a high efficient catalyst for the one-pot synthesis..., A. RAMAZANI, et al.
The silica NPs could be recycled and reused by separating them from the mixture through centrifugation,
and frequent washing with EtOH and then drying under vacuum to remove the residual solvent.The results show
that the yield of products was only slightly reduced after 5 runs.
Conclusions
We developed an efficient route for the one-pot synthesis of ketoamide derivatives 4 from simple and readily
available isocyanides 3, secondary amines 1, and 2-oxo-2-phenylacetaldehyde (2) in the presence of silicaNPs.
The ease of work-up and high yields of products make this procedure a useful addition to modern synthetic
methods.
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