ZnO nanoparticle-catalyzed efficient one-pot three-component synthesis of 3,4,5-trisubstituted furan-2(5H)-ones

Article abstract of DOI:10.1007/s13738-013-0266-9

An efficient and high-yielding protocol using nano-ZnO (50-100 nm) as an efficient heterogeneous catalyst for one-pot three-component synthesis of pharmacologically significant furanone derivatives by the condensation of aromatic aldehyde, amine and dimethylacetylenedicarboxylate has been developed. Since the catalyst is heterogeneous, it can be easily separated and recycled several times without much loss of its catalytic activity. Use of aqueous medium, recyclable nanocatalyst, operational simplicity, non-chromatographic purification technique, excellent yield and short reaction time makes this approach an attractive protocol for the synthesis of 3,4,5-trisubstituted furan-2(5H)-ones.

Full text of DOI:10.1007/s13738-013-0266-9

J IRAN CHEM SOC
DOI 10.1007/s13738-013-0266-9
ORIGINAL PAPER
ZnO nanoparticle-catalyzed efficient one-pot three-component
synthesis of 3,4,5-trisubstituted furan-2(5H)-ones
•
Sunil U. Tekale Sushma S. Kauthale
•
•
•
Vijay P. Pagore Vivekanand B. Jadhav
Rajendra P. Pawar
Received: 15 January 2013 / Accepted: 15 April 2013
Ó Iranian Chemical Society 2013
Abstract An efficient and high-yielding protocol using
nano-ZnO (50–100 nm) as an efficient heterogeneous cat-
alyst for one-pot three-component synthesis of pharmaco-
logically significant furanone derivatives by the
condensation of aromatic aldehyde, amine and dimethyla-
cetylenedicarboxylate has been developed. Since the cata-
lyst is heterogeneous, it can be easily separated and
recycled several times without much loss of its catalytic
activity. Use of aqueous medium, recyclable nanocatalyst,
operational simplicity, non-chromatographic purification
technique, excellent yield and short reaction time makes
this approach an attractive protocol for the synthesis of
3,4,5-trisubstituted furan-2(5H)-ones.
activities including antifungal, antibacterial, anti-oxidants,
anti-inflammatory, anti-microbial and anti-cancer agents [3–
7]. They are mutagenic in nature [8]. Chen et al. [9] reported
the LasR receptor inhibition on biofilm formation of Pseu-
domonas aeruginosa species. Consequently, furanones
constitute the biologically important targets in medicinal
chemistry.
Currently, one-pot multicomponent reactions (MCRs) are
becoming more popular over routine multistep organic
synthesis in terms of efficiency and practicability, as they
facilitate the construction of pharmacologically and medic-
inally active targets in a single step leading to diverse
molecular complexity [10]. These reactions allow the for-
mation of new bonds in one pot avoiding the number of steps;
afford clean reaction profile, high yield and are atom eco-
nomic. Thus MCRs are emerging as efficient and powerful
tools in modern synthetic organic chemistry for academia
and industry.
Keywords Aldehyde Á Amine Á DMAD Á
Furan-2(5H)-ones Á Nano-ZnO
Introduction
With the growing environmental hazards and emerging
green approaches, organic synthesis in aqueous medium is
preferred rather than the common organic solvents. Water
is abundant, easily available, low cost, non-toxic and green
reaction medium. It has high cohesive energy density and
high dielectric constant compared to organic solvents. It
has special effects on reactions due to inter- and intra-
molecular non-covalent interactions leading to novel sol-
vation processes. Water is being utilized for many organic
reactions. Organic synthesis in aqueous medium is pre-
ferred from commercial as well as economic point of view
[11].
Furanones are the five-membered heterocyclic compounds
possessing lactone ring in their structures. These heterocy-
cles are the core structures of many bioactive natural prod-
ucts as well as synthetic drugs such as rubrolide, sarcophine,
benfurodil hemisuccinate, etc. [1, 2]. 5H-Furan-2-one
derivatives exhibit many pharmacological and biological
S. U. Tekale Á V. P. Pagore Á V. B. Jadhav
Department of Chemistry, Shri Muktanand College,
Gangapur (MS), Maharashtra 431 109, India
Heterogeneous catalysts are superior to homogeneous
ones in terms of easy separation, recycling ability in suc-
cessive runs and minimization of metal traces in the
products. Consequently, performing multicomponent
reactions in aqueous medium using reusable heterogeneous
S. S. Kauthale Á R. P. Pawar (&)
Department of Chemistry, Deogiri College, Station Road,
Aurangabad, Maharashtra 431 005, India
e-mail: rppawar@yahoo.com
123

J IRAN CHEM SOC
catalysts is largely used in organic synthesis. These also
provide a number of active sites per unit area as compared
to their homogeneous counter parts. Reactions on solid
supports can be applied to increase reactivity.
Some of these protocols although one pot, suffer from
several aspects such as the use of expensive reagents,
inconvenient handling, reusability of catalyst, poor yields,
longer reaction time, sophisticated purification techniques,
etc. Considering the widespread utility of furanone deriv-
atives and availability of few literature protocols for the
synthesis of furanones and their limitations, in the present
work we have successfully developed a synthetic route
with the minimized drawbacks. Herein, we wish to report a
simple, convenient, rapid (2.5 h) and high-yielding method
using ZnO nanoparticle as an efficient, non-toxic and
commercially available reusable heterogeneous catalyst for
the synthesis of 3,4,5-trisubstituted furan-2(5H)-ones by
the condensation of aromatic aldehyde, amine and DMAD
in ethanol:H2O (1:1) at 90 °C (Scheme 1).
The surface area of a catalyst increases with decreasing
particle size. Recently, nano-catalysts have become viable
alternatives to the conventional materials due to their high
surface area, greater reactivity, easy recovery and reus-
ability. Nano-particles of transition metal oxides have
attracted significant attention as efficient catalysts in many
organic reactions due to their high surface-to-volume ratio
and low co-ordinating sites.
Zinc oxide is a versatile wide band gap (3.37 eV)
semiconductor material; basically recruited for its poten-
tial applications in solar cells, gas sensing materials,
optoelectronics, biomedical devices, etc. [12–14]. Owing
to its low toxicity, low cost, low corrosion, large surface
area, high pores volume and eco-friendly nature [15],
nano-ZnO is being extensively employed as a promising
Lewis acid reusable heterogeneous catalyst for diverse
range of one-pot multicomponent organic transformations
[16–19].
Experimental
All the chemicals were purchased from Aldrich or SD Fine
Chemicals and used without further purification. Melting
points were recorded in capillaries open at one end and
As per literature survey, only a few synthetic protocols
are documented for the synthesis of furanones. 3,4-Bis-
stannyl-2(5H) furanones were synthesized by Sweeney
et al. [20] using Stille reaction. Bassetti [21] reported
rhodium-catalyzed ring-closing metathesis from acrylic
esters using first-generation Grubbs’ catalyst as an effective
promoter. Fukuta [22] carried out rhodium-catalyzed
hydroformylation of propargyl alcohols into 2(5H)-fura-
nones under high pressure in which substituted cyclohex-
enes were also obtained. 3-Substituted-2,5-dihydro-2,5-
dimethoxyfurans can be hydrolyzed to 3-substituted-furan-
2(5H)-ones [23]. Furanones were obtained as the unex-
pected products during the palladium-catalyzed synthesis
of 2(2H)-pyranone from (Z)-2-en-4-ynoic acids [24]. A
multistep approach was employed by Ahn [25] for the
synthesis of 3,4-diaryl-2(5H)-furanone derivatives with
potent cytotoxic activities from acetophenone precursors.
A two-step synthesis was documented in literature for the
synthesis of 5-(substituted-phenyl)-3-(substituted-arylid-
ene)-2(3H)-furanones [26]. Y.V.D. Nageswar et al. [27]
firstly synthesized 3,4,5-trisubstituted furan-2(5H)-ones by
the three-component reaction between aldehyde, amine and
diethylacetylenedicarboxylate using b-cyclodextrin supra-
molecule. Nagarapu et al. [28] documented a similar
organic transformation using SnCl2 2H2O as the catalyst.
1
were uncorrected. H NMR spectra were recorded using
DMSO-d6 solvent on 400 MHz Varian Spectrophotometer
with TMS as an internal standard and chemical shifts (d)
are expressed in ppm. IR spectra of samples were recorded
on Bruker Vector 22 FTIR spectrophotometer using KBr
discs. Mass spectra were analyzed on Shimadzu mass
analyzer with EI 70 eV. TEM images were recorded on the
Transmission Electron Microscope instrument (TECNAI
G2 20 U-TWIN, FEI, Netherlands). EDX analysis of the
catalyst was carried out using scanning electron micro-
scope (JEOL JSM6360A) instrument 6360 (LA).
General procedure for the ZnO nanoparticle-catalyzed
synthesis of 3,4,5-trisubstituted furan-2(5H)-ones:
A solution of aromatic amine (2 mmol), dimethylacetyle-
nedicaboxylate (2 mmol) and ZnO (5 mol%) nanoparticles
in Ethanol:H2O (1:1) (2 mL) was magnetically stirred at
room temperature for 15 min. To it aromatic aldehyde
(2 mmol) was added and the contents were heated with
stirring at 90 °C for 2.5 h. The progress of reaction was
monitored by TLC in 70 % EA:hexane. After completion
of the reaction; the reaction mass was concentrated under
reduced pressure. To this crude hot ethanol (10 mL) was
Scheme 1 ZnO nanoparticle
catalyzed one pot three
component synthesis of
trisubstituted furan-2(5H)-ones
O
OMe
NH
R1
COOMe
CHO
NH2
Nano ZnO (5 mol%)
R1
R2
EtOH : H2O (1:1)
90 oC, 2.5 h
O
R2
COOMe
O
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J IRAN CHEM SOC
added and filtered off to separate the catalyst. The filtrate
was further concentrated and purified by recrystallization
from ethanol.
to-volume ratio and affords high catalytic activity which
helps to enhance the rate of reaction along with reduction
in the reaction time.
Using this procedure a series of furanones was synthe-
sized (Table 1). The spectral data of representative com-
pounds is represented below.
EDX
Energy-dispersive X-ray spectroscopy (EDS or EDX) is a
sophisticated instrumental analytical technique applicable
for the elemental analysis and chemical characterization of
materials. The chemical composition of crystalline ZnO
was studied using EDX in the energy range of 0–20 kV on
using scanning electron microscope (JEOL JSM6360A)
instrument 6360 (LA). The EDX analysis (Fig. 2) indicates
highly pure nature of the catalyst.
Methyl 2,5-dihydro-5-oxo-2-phenyl-4-(phenylamino)furan-
3-carboxylate (entry 1, Table 1)
Faint yellow solid; MP (°C) 159–162; 1H NMR (400 MHz,
DMSO-d6) d ppm 3.6 (s, 3H), 6.12 (s, 1H), 7.05–7.6 (m,
10H), 11.78 (brs, 1H, NH); IR (KBr) cm-1 3,211.48,
2,956.87, 2,370.51, 1,697.06, 1,640.00, 1,498.69, 1,232.51,
1,080.14; ESMS: 310 (M?1)?.
XRD
Methyl4-(p-tolylamino)-2,5-dihydro-5-oxo-2-phenylfuran-
3-carboxylate (entry 2, Table 1)
XRD studies of nano-ZnO showed a characteristic pattern
as shown in Fig. 3. The presence of diffraction peaks at 2h
values of 32.08, 34.74, 36.64, 48.04, 57.04, 63.22, 68.28
and 69.24 correspond to (100), (002), (101), (102), (110),
(103), (200) and (201) planes, respectively. The strongest
peak at 2h = 36.64 belongs to the (101) plane of the ZnO.
No impurity peaks were detected. The XRD pattern indi-
cates the face centered cubic structure of zinc oxide
nanoparticles.
1
Off-white solid; MP (°C) 284–287; H NMR (400 MHz,
DMSO-d6) d ppm 2.18 (s, 3H), 3.56 (s, 3H), 5.98 (s, 1H),
7.05-(d, 2H, J = 7.05 Hz), 7.1–7.3 (m, 5H), 7.4 (d, 2H,
J = 7.30 Hz), 11.8 (br, s, 1H, NH); IR (KBr) cm-1
3,228.84, 2,924.09, 2,854.65, 2,366.66, 1,658.78, 1,597.06,
1,494.83, 1,234.44, 1,089.78; ESMS: 324.01 (M?1)?.
Methyl 4-(4-fluorophenylamino)-2,5-dihydro-5-oxo-2-
phenylfuran-3-carboxylate (entry 4, Table 1)
Results and discussion
Faint yellow solid; MP (°C) 293–295; 1H NMR (400 MHz,
DMSO-d6) d ppm 3.58 (s, 3H), 6.07 (s, 1H), 7.15–7.45 (m,
9H), 11.8 (br, s, 1H, NH); IR (KBr) cm-1 3,228.84,
2,951.09, 2,360.87, 1,708, 1,676.14, 1,512.19, 1,234.44,
999.13; ESMS: 327.99 (M?1)?.
Initially to optimize the reaction conditions, various sol-
vents and catalysts were screened for three-component
model condensation of aniline (1 mmol), dimethylacety-
lenedicarboxylate (1 mmol) and benzaldehyde (1 mmol).
The effect of various alcoholic solvents such as ethanol
(EtOH), methanol (MeOH), isopropyl alcohol (IPA),
polyethylene glycol (PEG), etc. and catalysts like L-pro-
line, TBAF was investigated. The results are summarized
in (Table 2). It was observed that neither the use of
fluorinated reagent (entry 8) nor alcohol, i.e., 2,2,2-tri-
fluoroethyl alcohol (entry 1) could give good results
within 5–8 h. Nano-CuO was unable to increase the yield
(entry 9). The combination of zinc oxide nanoparticle
(5 mol%) and ethanol gave better yields (83 %) in 5 h
(entry 6). The use of EtOH:H2O (1:1) solvent system was
more effective than the mere use of ethanol in terms of
reduced reaction time and higher yields. Thus, better
results were obtained using 5 mol% ZnO and ethanol:H2O
solvent system within 3 h.
Methyl 2-(4-chlorophenyl)-2,5-dihydro-5-oxo-4-
(phenylamino)furan-3-carboxylate (entry 5, Table 1)
1
Off-white solid; MP (°C) 149–152; H NMR (400 MHz,
DMSO-d6) d ppm 3.56 (s, 3H), 6.05 (s, 1H), 7.10–7.58 (m,
9H), 11.90 (br, s, 1H, NH); IR (KBr) cm-1 3,265.49,
2,956.87, 2,368.59, 1,707.00, 16.8.63, 1,213.23, 1,128.36;
ESMS: 344.03 (M?1)?.
Catalyst characterization:
TEM
The size and morphology of nano-ZnO were studied using
transmission electron microscope (TEM). From the TEM
images (Fig. 1), particle size of the nano-crystalline ZnO
was found to be in the range of 50–100 nm. On account of
this small particle size, the catalyst exhibits high surface-
Furthermore, increasing the catalyst concentration from
5 to 10, 15 and 20 mol% could increase the yields to 94, 95
and 95 % indicating that 5 mol% of the nano-ZnO suffi-
cient enough to afford the corresponding furan-2 (5H)-ones
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J IRAN CHEM SOC
Table 1 ZnO nanoparticle-
catalyzed one-pot three-
component synthesis of
MP(°C)b
Entry
Aldehyde
(R1)
Amine (R2)
Product
Yield (%)a
O
OMe
trisubstituted furan-2(5H)-ones
NH
O
1
H
H
H
94
159–162
284–287
O
(F1)
O
OMe
NH
O
2
4-Me
95
O
Me
(F2)
MeO
O
OMe
NH
3
4
4-OMe
H
88
84
239–242
293–295
O
O
(F3)
O
OMe
NH
H
4-F
O
O
F
(F4)
Cl
O
OMe
NH
5
6
7
4-Cl
2-Cl
H
H
H
89
87
85
149–152
273–275
240–243
O
O
(F5)
O
OMe
NH
Cl
O
O
(F6)
O
OMe
NH
H3CO
3-OCH3
O
O
(F7)
Me
O
OMe
NH
8
9
4-Me
H
84
88
181–183
>300
O
O
(F8)
O
H
4-CHMe2
OMe
NH
O
O
(F9)
O
OMe
10
H
2-F
84
>300
NH
O
O
F
(F10
)
)
Cl
O
OMe
11
12
2,4-Cl2
2-F
85
83
271–273
NH
F
Cl
O
O
a
Yields of reactions performed on
aldehyde (2 mmol), amine
(F11
MeO
(2 mmol), DMAD (2 mmol) in 1:1
EtOH:H2O (2 mL) using 5 mol %
nano-ZnO at 90 °C for 2.5 h
O
OMe
NH
2,4-
(OMe)2
H
>300
OMe
O
b
O
Melting points were compared
with the literature values in Ref. [28]
(F12
)
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J IRAN CHEM SOC
Fig. 1 TEM images of the nano-crystalline ZnO
Table 2 Effect of various reaction conditions on the one-pot three-
component synthesis of furanones
Entry Reaction conditionsa
Yield (%)b
1
2
ZnO (5 mol%), TFE, 70 °C, 5 h
ZnO(5 mol%), MeOH, 60 °C, 5 h
ZnO (5 mol%), IPA, 85 °C, 5 h
30
67
38
3
4
ZnO (5 mol%), Ethylene glycol, 80 °C, 5 h 26
5
ZnO (5 mol%), PEG, 80 °C, 8 h
ZnO (5 mol%), EtOH, 80 °C, 5 h
L-Proline (5 mol%), EtOH, 80 °C, 7 h
TBAF (5 mol%), THF, 70 °C, 8 h
Nano-CuO (5 mol%), EtOH, 80 °C, 5 h
12
6
83
7
28
8
09
9
32
10
b-Cyclodextrin (mol%), H2O, 60–70 °C,
12–16 h
78–88 [27]
11
12
SnCl2, EtOH, reflux, 6.5–7.0 h
85–90 [28]
Fig. 2 EDX analysis of nano-ZnO
ZnO, EtOH:H2O (1:1), 90 °C, 2.5 h
94 (present
work)
1000
a
ZnO
Reactions were tried on benzaldehyde (1 mmol), aniline (1 mmol),
DMAD (1 mmol) in 1 mL solvent
b
800
600
400
200
0
Isolated yields
Table 3 Recycle study of nano-ZnO catalyst
Run
Yield (%)a
1
2
3
4
94
91
87
84
a
Reactions were carried on benzaldehyde (1 mmol), aniline
(1 mmol), DMAD (1 mmol) using 5 mol% nano-ZnO catalyst in 1:1
EtOH:H2O (1 mL) at 90 °C for 2.5 h
To explore the scope and feasibility of these optimized
conditions a series of furanones was obtained from dif-
ferent substituted amines, aldehydes and DMAD in the
presence of 5 mol% nano-ZnO at 90 °C (Table 1). Studies
reveal that almost all aldehydes and amines reacted cleanly
to afford the corresponding products in excellent yields.
Substituents on neither the aldehyde nor amine had
prominent effect on yield of reaction. This is one of the
20
30
40
50
60
70
80
2 Theta (degree)
Fig. 3 XRD of nano-ZnO
in higher yields. Nano-ZnO seems to be more efficient than
the other screened catalysts. The catalyst recovered after
the reaction gives good recycle results (Table 3).
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J IRAN CHEM SOC
H
N
ZnO
COOMe
COOMe
O
R2
NH2
R2
H
R1
DMAD
O
H
R2
OMe
N+
H
ZnO
COOMe
O
ZnO
O
OMe
NH
R1
O
H
R2
OMe
N+
H
O
R2
O+H
O
O
OMe
ZnO
Fig. 4 Proposed mechanism for ZnO nanoparticle-catalyzed synthesis of trisubstituted furan-2(5H)-ones
Acknowledgments The authors are thankful to the Principal,
Deogiri College Aurangabad, for providing laboratory facilities and
constant encouragement during the work. We thank the Department
of Physics, Pune University, for providing the Sophisticated Analyt-
ical and Instrument (SAIF) Facilities.
important advantages of the present ZnO nanoparticle-
catalyzed synthesis of furanones.
The plausible mechanism for the ZnO nanoparticle-
catalyzed synthesis of furan-2(5H)-ones from aldehydes,
amines and DMAD is depicted in Fig. 4. Initially, ZnO
promotes the formation of enamine from amine and
DMAD. ZnO polarizes the carbonyl group of aldehyde to
form polarized adduct which reacts with the enamine fol-
lowed by cyclization with the elimination of methanol
molecule to afford the corresponding furan-2(5H)-ones.
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In summary, we have successfully developed an efficient
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