Green one-pot multicomponent synthesis of pyrrolidinones using planetary ball milling process under solvent-free conditions

Article abstract of DOI:10.1080/00397911.2019.1601225

This paper presents a novel and efficient protocol for the synthesis of pyrrolidinones using catalytic loading of 1,1'-butylenebis(3-sulfo-3H-imidazol-1-ium) hydrogen sulfate as a recyclable Br?nsted acid ionic liquid through ball milling process at room temperature under solvent-free conditions. The developed method provides good to excellent yields of various pyrrolidinones in environmentally friendly conditions. Furthermore, this efficient protocol displays a combination of the synthetic advantage of one-pot multicomponent reaction with ecological benefits and convenience of a mechanochemical procedure.

Full text of DOI:10.1080/00397911.2019.1601225

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Green one-pot multicomponent synthesis of
pyrrolidinones using planetary ball milling process
under solvent-free conditions
Nader Ghaffari Khaligh, Taraneh Mihankhah & Mohd Rafie Johan
To cite this article: Nader Ghaffari Khaligh, Taraneh Mihankhah & Mohd Rafie Johan (2019):
Green one-pot multicomponent synthesis of pyrrolidinones using planetary ball milling process
under solvent-free conditions , Synthetic Communications, DOI: 10.1080/00397911.2019.1601225
To link to this article: https://doi.org/10.1080/00397911.2019.1601225
View supplementary material
Published online: 17 Apr 2019.
Submit your article to this journal
Article views: 8
View Crossmark data
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lsyc20

R
SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2019.1601225
Green one-pot multicomponent synthesis of pyrrolidinones
using planetary ball milling process under solvent-
free conditions
Nader Ghaffari Khaligha, Taraneh Mihankhahb, and Mohd Rafie Johana
aNanotechnology and Catalysis Research Center, Institute of Postgraduate Studies, University of Malaya,
b
Kuala Lumpur, Malaysia; Department of Water and Environmental Engineering, Environmental
Research Laboratory, School of Civil Engineering, Iran University of Science and Technology,
Tehran, Iran
ABSTRACT
ARTICLE HISTORY
Received 22 November 2018
This paper presents a novel and efficient protocol for the synthesis
of pyrrolidinones using catalytic loading of 1,1’-butylenebis(3-sulfo-
3H-imidazol-1-ium) hydrogen sulfate as a recyclable Bronsted acid
ionic liquid through ball milling process at room temperature under
solvent-free conditions. The developed method provides good to
excellent yields of various pyrrolidinones in environmentally friendly
conditions. Furthermore, this efficient protocol displays a combin-
ation of the synthetic advantage of one-pot multicomponent reac-
tion with ecological benefits and convenience of a mechanochemical
procedure.
€
KEYWORDS
Mechanochemistry; pyrroli-
dinone; ionic liquid;
€
Bronsted acid; eco-
friendly conditions
GRAPHICAL ABSTRACT
Introduction
The chemists have been broadly interested to the design of new protocols based on
some of the essential and sustainable approaches including avoiding toxic and volatile
solvents or perform the reaction under solvent-free conditions, load catalytic amounts
CONTACT Nader Ghaffari Khaligh
ngkhaligh@gmail.com; ngkhaligh@um.edu.my
Nanotechnology and Catalysis
Research Center, Institute of Postgraduate Studies, University of Malaya, 3rd Floor, Block A, Kuala Lumpur,
50603, Malaysia.
Supplemental data for this article is available online at on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
N. G. KHALIGH ET AL.
of catalyst instead of stoichiometric amounts and use nontoxic recyclable catalysts.[1,2]
The ball milling as a mechanochemical process under solvent-free conditions plays an
important role in the academic and industrial transformations which can lead to the
reduced amount of catalyst loading, a shorter reaction time, and a higher yield.[3] The
applications of the planetary ball mill was broadly reported in the literature for the syn-
thesis of catalysts,[4] metal complexes,[5] heterocycles,[6] N-methyl imines,[7,8] catenanes
and rotaxanes,[9] metal-organic frameworks (MOFs),[10] and the C–C bond formation
reactions, protection functional groups, fullerenes, and redox processes.[11]
€
We recently succeeded in the synthesis of two novel binuclear Bronsted acid ionic
liquids based on imidazole viz. 1,10-butylenebis(3-sulfo-3H-imidazol-1-ium) chloride
([BBSI]Cl) and 1,10-butylenebis(3-sulfo-3H-imidazol-1-ium) hydrogen sulfate
([BBSI][HSO4]). Their catalytic applications were demonstrated for the one-pot multi-
component synthesis of bis(indolyl)methanes,[12] xanthenes,[13] and pyrrolidinones under
conventional conditions.[14] As part of our studies in developing non-conventional proc-
esses for the synthesis of valuable compounds,[7,8] herein, the synthesis of pyrrolidinones
is reported in the presence of catalytic amount of [BBSI]Cl and [BBSI][HSO4]
under solvent-free conditions at room temperature using ball milling process. A simple
separation and purification of products without the requirement of a chromatography,
solvent-free and mild conditions and easy recycling of the catalyst are attractive merits of
the current protocol.
Results and discussion
Synthesis of pyrrolidinones in the presence of [BBSI]Cl and [BBSI][HSO4]
The condensation reaction of 4-chlorobenzaldehyde (1a), aniline, and diethyl acetylene-
dicarboxylate were investigated as a model reaction for the optimization of the reaction
parameters, (Scheme 1).
The model reactants were ground using the planetary ball mill in the absence of a
catalyst at room temperature under solvent-free conditions. After 2 hours, the TLC and
GC-MS spectra of the reaction mixture showed no respective product, viz. ethyl-2-(4-
chlorophenyl)-4-hydroxy-5-oxo-1-phenyl-2,5-dihydro-1H-pyrrole-3-carboxylate
(4a)
(Table 1, entry 1). Then, the model reactants were milled in the presence of [BBSI]Cl
for two hours. The crude product was extracted with ethyl acetate from grinding jar
and purified by recrystallization from hot ethanol which afforded the desired product
(4a) in 42% yield (Table 1, entry 2). A [BBSI]Cl loading to 1.0 mol% showed a more
favorable effect on the reaction yield (Table 1, entry 3). However, no significant
Scheme 1. Investigation and optimization of various reaction parameters.

R
SYNTHETIC COMMUNICATIONSV
3
improvement was observed in the yield of 4a at higher catalyst loading up to 2.0 mol%
(Table 1, entry 4). When the reaction time was curtailed to 30 min, no considerable dif-
ference was observed in the reaction yield (Table 1, entry 5), while the yield dropped
when the reaction time was reduced from 30 min to 20 min (Table 1, entry 6). Then,
the influence of technical parameters such as revolution per minute (rpm), number and
size of ball mill were studied on the performing of the model reaction. As shown in
Table 1, the results displayed that rpm has a vital influence on the yield of the desired
product, at which point, the best yield of 4a was observed at 600 rpm of the planetary
ball mill within 30 min (Table 1, entries 5, 7 and 8). While the other parameters were
kept constant, the number and the size of the milling balls were changed. As reported
in the literature, these parameters directly influence the active surface area and the total
mass of the milling balls, which are important variables for the energy transfer and
increase of internal temperature and pressure.[15] As expected, a higher yield of 4a was
obtained when the experiment was conducted with a higher number and larger size of
milling balls (Table 1, entries 13 and 14). Then, the model reaction was conducted in
the presence of [BBSI][HSO4] under the aforementioned optimized reaction conditions.
The results exhibited that the ionic liquid bearing an acidic and non-coordinating anion
had a crucial influence not just on the reaction yield but on the reaction time too
(Table 2). Therefore, entry 6 in Table 2 was chosen as the optimized reaction conditions
Table 1. Optimization of the synthesis of ethyl-2-(4-chlorophenyl)-4-hydroxy-5-oxo-1-phenyl-2,5-dihy-
dro-1H-pyrrole-3-carboxylate in the presence of [BBSI]Cl using planetary ball milla.
Loading
[BBSI]Cl (mol%)
Number of
ball mill
Ball mill
diameter (mm)
Milling
time (min)
Entry
Speed (rpm)
Yield (%)b
–c
1
2
3
4
5
6
7
8
0
4
4
4
4
4
4
4
4
6
6
300
300
300
300
300
300
600
500
600
600
7
7
7
7
7
7
7
7
7
5
120
120
120
120
30
20
30
30
30
30
0.5
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
42
58
59
56
47
68
65
87
46
9
10
aReaction conditions: 4-chlorobenzaldehyde (1a) (5.0 mmol), aniline (5.0 mmol), and diethyl acetylenedicarboxylate
(5.0 mmol), room temperature.
bIsolated yield.
cMonitored by GC-MS.
dBold values signify the optimize reaction conditions.
Table 2. The synthesis of ethyl-2-(4-chlorophenyl)-4-hydroxy-5-oxo-1-phenyl-2,5-dihydro-1H-pyrrole-
3-carboxylate in the presence of [BBSI][HSO4] using planetary ball mill.a
Loading [BBSI][HSO4]
Number of
ball mill
Ball mill
diameter (mm)
Milling
time (min)
Entry
(mol%)
Speed (rpm)
Yield (%)b
1
2
3
4
5
6
1.0
0.5
1.0
1.0
1.0
1.0
6
6
4
6
6
6
600
600
600
600
600
600
7
7
7
5
7
7
30
30
30
30
20
25
92
64
76
58
72
92
aReaction conditions: 4-chlorobenzaldehyde (1a) (5.0 mmol), aniline (5.0 mmol), and diethyl acetylenedicarboxylate
(5.0 mmol), room temperature.
bIsolated yield.
cBold values signify the optimize reaction conditions.

4
N. G. KHALIGH ET AL.
Scheme 2. Synthesis of pyrolidinones in the presence of [BBSI][HSO4] under optimal conditions.
Table 3. The one-pot multicomponent synthesis of pyrolidinone derivatives 4(a-o) using ball mill
process in the presence of [BBSI][HSO4] under optimized reaction conditionsa.
Entry
R1 (1)
R2 (2)
R3 (3)
Product (4)
Yield (%)b
1
2
3
4
5
6
7
8
4-Cl
H
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Me
Me
Et
Et
Et
H
H
H
H
H
H
H
H
H
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
92
90
88
96
92
87
85
95
84
82
90
86
84
82
87
4-CH3
4-CF3
4-NO2
4-CH3O
4-OH
2-NO2
2-Cl
2-CH3O
H
4-CH3
4-CF3
4-CF3
4-CF3
9
10
11
12
13
14
15
H
H
H
4-CH3
4-NO2
4-CH3O
aReaction conditions: aryl aldehyde (1) (5.0 mmol), dialkyl acetylenedicarboxylate (2) (5.0 mmol), aniline or its derivatives
(3) (5.0 mmol), [BBSI][HSO4] (0.05 mmol), six milling ball (diameter 7 mm), revolution rate (600 rpm), room tempera-
ture, milling time (25 min).
bIsolated yield.
and the scope and generality of the present protocol for the preparation of pyrrolidi-
nones was evaluated (Scheme 2).
A broad range of pyrrolidinone derivatives was prepared in good to excellent yield
under optimal reaction conditions (Table 3). The reaction proceeded smoothly with
aldehydes bearing electron-withdrawing or electron-donating substituents in the aro-
matic ring. The anilines bearing electron-withdrawing substituents in para-position
afforded a slightly lower yield of the desired product than electron-donating substituents
at the same position due to the deactivation of the amino group (Table 3, entries 13-
15). All the known products have spectral and physical data consistent with those
reported in the literature.[14] It is worth mentioning that the proton of the 4-hydroxyl
group in all of the respective pyrrolidinones showed the most downfield broad peak at
ꢀ9 ppm (1H NMR, CDCl3). It is probably due to the anisotropy of carbonyl groups
resulting from the b-interaction with one amino carbonyl function, and a c-interaction
with the carboxylate function.
A possible mechanism was previously reported in the presence of [BBSI]Cl in the lit-
erature.[14] The [BBSI]Cl and [BBSI][HSO4] have the same cation moiety, and the
experimental results exhibited that the anion moiety plays a vital role in the yield and

R
SYNTHETIC COMMUNICATIONSV
5
Scheme 3. A possible mechanism for the one-pot multicomponent synthesis of 4 b in the presence
of [BBSI][HSO4].
the reaction time. Therefore, a possible mechanism was proposed for the illustration
of this concept (Scheme 3). The sulfonic acid groups and CH-2 of imidazole rings
on the cation moiety and hydrogen sulfate anion of [BBSI][HSO4] simultaneously
activate benzaldehyde and aniline to initiate the condensation reaction through the
hydrogen bond (HB). The imine (I) is formed through the attack of aniline to the
carbonyl group of benzaldehyde followed by removing a water molecule. As shown
in the Scheme 3, the IL cation and hydrogen sulfate anion can promote the second
reaction step viz. the addition of water molecule from the first reaction step or
medium to diethyl acetylene dicarboxylate by the formation of HB. The intermediate
(III) is afforded through the Michael addition of imine (I) and intermediate (II).
An intermolecular cyclization (IV) and the elimination of one ethanol moleculeꢁ(V)
along with tautomerization will give the final product. The IL cation and HSO4 as
a good HB donor-acceptor and proton exchanger can prompt the third reaction
step too.
Table 4 exhibits the superiority of the current protocol in comparison with a few
other methods reported in the literature in terms of solvent-free condition, catalyst
loading, yield, reaction time, and recyclability of the catalyst.
The feasibility of the present method on gram scaled experiment was studied through
the reaction of the 4-chlorobenzaldehyde (0.05 mol), diethyl acetylene dicarboxylate
(0.05 mol), aniline (0.05 mol), and [BBSI][HSO4] (5 mmol) under optimized reaction
conditions which afforded 4a in 87% isolated yield within 25 min.

6
N. G. KHALIGH ET AL.
Table 4. The comparative study of present vs. previously reported methodology for the synthesis
of 4b.
Catalyst
loading
(mol%)
Reaction
time (h)
Entry
Catalyst
[BBSI]Cl
Solvent
Temp. (ꢂC)
Yield (%) Recyclable
Ref.
[14]
[16]
1
2
1.0
–
Ethanol (96%)
Ethanol/H2O
(1:1 v/v)
r.t.
r.t.
30 min
15
86
87
Yes
–
–
[17]
[17]
[18]
[19]
[19]
3
4
5
6
7
8
9
Citric acid
200
200
20
Ethanol
r.t.
40
r.t.
30
30
r.t.
r.t.
10
20 min
48
85
90
No
No
No
No
No
Yes
Yes
monohydrate
Citric acid
monohydrate
p-toluenesul-
fonic acid
Lactic
acid (Solvent)
Glacial
acetic acid
[BBSI]Cl
Ethanol
(US 100W)
Ethanol
62
1 mL (1140) Lactic acid (85%
wt/wt)
1 mL (1746) Glacial
acetic acid
2
60a
24a
87
2
1.0
Solvent-free
(Ball milling)
Solvent-free
(Ball milling)
30 min
25 min
This work
This work
[BBSI][HSO4]
1.0
90
a4-methyl benzaldehyde.
Reusability of [BBSI][HSO4]
Two procedures were carried out to evaluate the recyclability of [BBSI][HSO4]. In the
first procedure involved, the extraction of the product with ethyl acetate several times.
Then, the remained IL was concentrated and the reaction jar was recharged with new
model reactants for another run. The product 4a was obtained in an average 92–90%
yield for three subsequent runs. Furthermore, the chemical structure of the IL showed
no significant change under the present workup.
In the other procedure, the [BBSI][HSO4] was washed with deionized water followed
by evaporation of water from an aqueous solution containing the IL. The recovered IL
was successfully reused for the subsequent runs without significant loss of catalytic
activity. The results demonstrated that both procedures were practical for the recovering
of [BBSI][HSO4] after reactions.
Experiment
General
Unless specified, all chemicals were analytical grade and purchased from Merck,
Aldrich, and Fluka Chemical Companies and used without further purification.
Products were characterized by their physical constant and IR, NMR and elemental ana-
lysis. The purity determination of the substrates and reaction monitoring were accom-
panied by TLC using silica gel SIL G/UV 254 plates. The FT-IR spectra were recorded
on a Perkin Elmer 781 Spectrophotometer using KBr pellets for solid and neat for liquid
1
samples in the range of 4000–400 cmꢁ1. In all the cases, the H and 13C NMR spectra
were recorded with Bruker Avance III 600 MHz and 400 MHz instrument. All chemical
shifts are quoted in parts per million (ppm) relative to TMS using deuterated solvent.

R
SYNTHETIC COMMUNICATIONSV
7
Microanalyses were performed on a Perkin- Elmer 240-B microanalyzer. Melting points
were recorded on a Bu€chi B-545 apparatus in open capillary tubes. Ball-milling was per-
formed in a Retsch PM100 planetary ball mill using a 10 mL and 25 mL stainless steel
chamber and four-six stainless steel balls (diameter: 5 or 7 mm) with 300–600 revolution
per minute (rpm).
The typical procedure for the synthesis of ethyl-1-phenyl-2-(4-chlorophenyl)-4-
hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxylate (4a)
A mixture of 4-chlorobenzaldehyde (5.0 mmol) (1), dialkyl acetylene dicarboxylate
(5.0 mmol), aniline (5.0 mmol), and [BBSI][HSO4] ionic liquid (0.05 mmol, 1.0 mol%)
was ground stirred in milling jar at 600 rpm for 25 min in the presence of six milling
ball (diameter 7 mm). The crude products were extracted by EtOAc (3 ꢃ 10 mL) and the
collected extracted organic phases were dried on anhydrous Na2SO4 and the solvent was
removed under vacuum and the product purified by recrystallized from hot ethanol to
get the pure ethyl-1-phenyl-2-(4-chlorophenyl)-4-hydroxy-5-oxo-2,5-dihydro-1H-pyr-
role-3-carboxylate (4a).
Ethyl-1-phenyl-2-(4-chlorophenyl)-4-hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxyl-
1
ate (4a): 1.65 g (yield 92%); mp 189–192 ꢂC; H NMR (400 MHz, CDCl3) d: 1.20 (t,
J ¼ 7.0 Hz, 3H), 4.20 (q, J ¼ 7.0 Hz, 2H), 5.72 (s, 1H), 7.11–7.17 (m, 3H), 7.22–7.30 (m,
4H), 7.43 (d, J ¼ 8.0 Hz, 2H), 9.04 (br s, 1H) ppm; 13C NMR (100 MHz, CDCl3) d: 13.6,
60.5, 61.1, 112.5, 122.0, 125.8, 128.6, 128.7, 128.9, 133.4, 134.1, 135.8, 156.3, 162.4,
164.6 ppm; Anal. Calcd. for C19H16ClNO4: C, 63.78; H, 4.51; N, 3.91; Found: C, 63.73;
H, 4.49; N, 3.86%.
All the known products have spectral and physical data consistent with those
reported in the literature as well as the samples prepared from previously
reported methods.[14]
Recycling catalyst
After extraction of the crude products, the remaining IL was concentrated and the reac-
tion jar was recharged with new model reactants for the next run.
Conclusion
The catalytic efficiency of [BBSI][HSO4] was demonstrated for the synthesis of pyr-
rolidinones through ball mill process under mild and solvent-free conditions. The
current protocol has the advantages such as solvent-free process, good to excellent
yield of the desired products within short reaction times, a broad substrate-scope,
and recyclability of the catalyst. The achieved experimental data for the synthesis of
€
pyrrolidinones shows that [BBSI][HSO4] can be an efficient Bronsted acid ionic
liquid catalyst for the one-pot multicomponent reactions and we hope that our work
will encourage further research in this area with promising results for future applica-
tions of [BBSI][HSO4].

8
N. G. KHALIGH ET AL.
Acknowledgments
The authors are grateful to staff members in the Analytical and Testing Center of Malaya
University for partial support. The authors received no specific funding for this research.
Disclosure statement
There are no conflicts of interest to declare.
Supporting information
1
Full experimental detail along with yield, melting point, H and 13C NMR spectra, elemental ana-
1
lysis data, and H NMR and 13C NMR copies of 4a, 4d, 4 g, 4 l, 4 m, 4n, and 4o can be found via
the “Supplementary Content” section of this article’s webpage.
References
[1] Tanaka, K.; Toda, F. Solvent-Free Organic Synthesis. Chem. Rev. 2000, 100, 1025–1074.
DOI: 10.1021/cr940089p.
[2] Wenda, S.; Illner, S.; Mell, A.; Kragl, U. Industrial Biotechnology—The Future of Green
Chemistry? Green Chem. 2011, 13, 3007–3047. DOI: 10.1039/c1gc15579b.
[3] Martins, M. A. P.; Frizzo, C. P.; Moreira, D. N.; Buriol, L.; Machado, P. Solvent-Free
Heterocyclic Synthesis. Chem. Rev. 2009, 109, 4140–4182. DOI: 10.1021/cr9001098.
[4] Kubias, B.; Fait, M. J. G.; Schlogl, R. Mechanochemical Methods. In Hand Book of
Heterogeneous Catalysis, 2nd ed.; Ertl, G., Knozinger, H., Schuth, F., Weitkamp, J., Eds.;
Wiley-VCH: Weinheim, 2008, pp. 571–583.
[5] Garay, A. L.; Pichon, A.; James, S. L. Solvent-Free Synthesis of Metal Complexes. Chem.
Soc. Rev. 2007, 36, 846–855. DOI: 10.1039/b600363j.
[6] M’hamed, M. O. Ball Milling for Heterocyclic Compounds Synthesis in Green Chemistry:
A Review. Synth. Commun. 2015, 45, 2511–2528. DOI: 10.1080/00397911.2015.1058396.
[7] Khaligh, N. G.; Abbo, H. S.; Salam, S. J. J. Synthesis of N-Methyl Imines in the Presence
of Poly(N-Vinylpyridine) as a Reusable Solid Base Catalyst by a Mechanochemical
Process. Res. Chem. Intermed. 2017, 43, 901–910. DOI 10.1007/s11164-016-2672-y. DOI:
10.1007/s11164-016-2672-y.
[8] Khaligh, N. G.; Ling, O. C.; Mihankhah, T.; Johan, M. R.; Ching, J. J. Mechanosynthesis
of N-Methyl Imines Using Recyclable Imidazole-Based Acid-Scavenger: In Situ Formed
Ionic Liquid as Catalyst and Dehydrating Agent. Aust. J. Chem. 2018, 72, 194–199. DOI:
10.1071/CH18408.
[9] Hsu, C. C.; Chen, N. C.; Lai, C. C.; Liu, Y. H.; Peng, S. M.; Chiu, S. H. Solvent-Free
Synthesis of the Smallest Rotaxane Prepared to Date. Angew. Chem. Int. Ed. 2008, 47,
7475–7478. DOI: 10.1002/anie.200803056.
[10] Wilke, M.; Klimakow, M.; Rademann, K.; Emmerling, F. Fast and Efficient Synthesis of a
Host Guest System: A Mechanochemical Approach. CrystEngComm. 2016, 18, 1096–1100.
DOI: 10.1039/C5CE01868D.
[11] Stolle, A.; Szuppa, T.; Leonhardt, S. E. S.; Ondruschka, B. Ball Milling in Organic
Synthesis: Solutions and Challenges. Chem. Soc. Rev. 2011, 40, 2317–2329. DOI: 10.1039/
c0cs00195c.
[12] Khaligh, N. G.; Mihankhah, T.; Johan, M. R.; Ching, J. J. Two Novel Binuclear Sulfonic
Functionalized Ionic Liquids: Influence of Anion and Carbon-Spacer on Catalytic
Efficiency for One-Pot Synthesis of Bis(Indolyl)Methanes. J. Mol. Liq. 2018, 259, 260–273.
DOI: 10.1016/j.molliq.2018.03.044.

R
SYNTHETIC COMMUNICATIONSV
9
[13] Khaligh, N. G. Synthesis and Characterization of Novel Binuclear Task-Specific Ionic
Liquid: An Efficient and Sustainable Sulfonic-Functionalized Ionic Liquid for One-Pot
Synthesis of Xanthenes. Res. Chem. Intermed. 2018, 44, 4045–4062. DOI: 10.1007/s11164-
018-3354-8.
[14] Khaligh, N. G.; Chong, K. F.; Mihankhah, T.; Titinchi, S.; Johan, M. R.; Ching, J. J. An
Efficient Synthesis of Pyrrolidinone Derivatives in the Presence of 1,1’-Butylenebis(3-
Sulfo-3H-Imidazol-1-Ium) Chloride. Aust. J. Chem. 2018, 71, 566–572. DOI: 10.1071/
CH18246.
[15] Schneider, F.; Stolle, A.; Ondruschka, B.; Hopf, H. The Suzuki ꢁ Miyaura Reaction under
Mechanochemical Conditions. Org. Process Res. Dev. 2009, 13, 44–48. DOI: 10.1021/
op800148y.
[16] Zonouz, A. M.; Eskandari, I.; Notash, B. Efficient Synthesis of 3-Pyrrolin-2-One
Derivatives in Aqueous Media. Synth. Commun. 2015, 45, 2115–2121. DOI: 10.1080/
00397911.2015.1065506.
[17] Ahankar, H.; Ramazani, A.; SꢀLepokura, K.; Lis, T.; Joo, S. W. Synthesis of Pyrrolidinone
Derivatives from Aniline, an Aldehyde and Diethyl Acetylenedicarboxylate in an Ethanolic
Citric Acid Solution under Ultrasound Irradiation. Green Chem. 2016, 18, 3582–3593.
DOI: 10.1039/C6GC00157B.
[18] Sun, J.; Wu, Q.; Xia, E.-Y.; Yan, C.-G. Molecular Diversity of Three-Component Reactions
of Aromatic Aldehydes, Arylamines, and Acetylenedicarboxylates. Eur. J. Org. Chem.
2011, 2011, 2981–2986. DOI: 10.1002/ejoc.201100008.
[19] Yang, J.; Tan, J.-N.; Gu, Y. Lactic Acid as an Invaluable Bio-Based Solvent for Organic
Reactions. Green Chem. 2012, 14, 3304–3317. DOI: 10.1039/c2gc36083g.