Design, synthesis, and biological evaluation of structurally constrained hybrid analogues containing ropinirole moiety as a novel class of potent and selective dopamine D3 receptor ligands

Article abstract of DOI:10.1111/cbdd.13324

Two series of hybrid analogues were designed, synthesized, and evaluated as a novel class of selective ligands for the dopamine D3 receptor. Binding affinities of target compounds were determined (using the method of radioligand binding assay). Compared to comparator agent BP897, compounds 2a and 2c were found to demonstrate a considerable binding affinity and selectivity for D3 receptor, and especially compound 2h was similarly potent and more selective D3R ligand than BP897, a positive reference. Thus, they may provide valuable information for the discovery and development of highly potent dopamine D3 receptor ligands with outstanding selectivity.

Full text of DOI:10.1111/cbdd.13324

PROFESSOR JIN CAI (Orcid ID : 0000-0001-8826-1042)
Article type
: Research Article
Design, Synthesis and Biological Evaluation of Structurally Constrained Hybrid
Analogues Containing Ropinirole Moiety as a Novel Class of Potent and
Selective Dopamine D3 Receptor Ligands
Benhua Zhou a,b, Kwon Ho Hong c, Min Jid, e,*, Jin Cai a, e
*
a School of Chemistry and Chemical Engineering, Southeast University, Nanjing, Jiangsu, 210096, P. R.
China
b School of Chemistry and Chemical Engineering, Yancheng Institute of Technology, 211 Jianjun East
Road, Yancheng 224051, PR China.
c Department of Medicinal Chemistry and the Institute for Therapeutics Discovery and Development,
University of Minnesota, Minneapolis, MN 55414, USA
d School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, P. R.
China
e Suzhou Key Laboratory of Biomaterials and Technologies & Collaborative Innovation Center of
Suzhou Nano Science and Technology, Suzhou 215123, P. R. China
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10.1111/cbdd.13324
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*Corresponding Authors:
Jin Cai, Ph.D.
School of Chemistry and Chemical Engineering, Southeast University
87 Dingjiaqiao
Nanjing 210096, Jiangsu, China
Tel: 025-83272349
E-mail: caijin@seu.edu.cn
Abstract
Two series of hybrid analogues were designed, synthesized, and evaluated as a novel class
of selective ligands for the dopamine D3 receptor. Binding affinities of target compounds
were determined (using the method of radioligand binding assay). Compared to comparator
agent BP897, compounds 2a and 2c were found to demonstrate a considerable binding
affinity and selectivity for D3 receptor, and especially compound 2h was similarly potent
and more selective D3R ligand than BP897, a positive reference. Thus they may provide
valuable information for the discovery and development of highly potent dopamine D3
receptor ligands with outstanding selectivity.
Key words: Dopamine D3 receptor subtype; Novel ligands; Indoline-2-one; Hybrid
compounds; structure-activity relationship
1. Introduction
Since the dopamine 3 (D3) subtype receptor was first reported by Sokoloff et al. in
1990[1], it has been proved to be a promising therapeutic target for the central nervous
system (CNS) diseases[2-4], and potent and selective D3 ligands may have the therapeutic
potential for the treatment of drug addiction[5-8], Parkinson’s disease[9,10],
schizophrenia[11,12], restless legs syndrome (RLS) and other CNS disorders[13,14].
Although an enormous amount of work has been done in recent years toward the discovery
and development of potent and selective D3 ligands[15-17], a functional study of D3R in
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vivo is currently still limited due to the lack of D3 ligands possessing high binding affinity and
selectivity.
Dopaminergic neurotransmission is mediated by five dopamine receptors (D1-D5), which
can be grouped into the D1-like (D1 and D5) and D2-like (D2, D3, and D4) receptor subtypes.
It is a challenging task to develop highly potent and selective ligands for D3R, since the
sequences of the D2-like dopamine receptor subtypes are highly similar[18]. In particular,
D3R and D2R share 78% sequence identity within the seven transmembrane
domains[19-21].
In 2010, Chien et al. reported the crystal structure of the human D3R[19], providing an
insight for the rational design of D3R ligands. Chien and coworkers described the structural
observation of an extracellular binding pocket highlighting the importance of the
extracellular loops that were once thought to provide superficial definition to ligand binding
[19].
Ropinirole (Fig. 1) has been used as monotherapy or in combination with levodopa for the
treatment of parkinsonism and RLS[22,13]. It shows a full agonist activity in the mitogenic
functional assay[23]. The efficacy of this compound may be related to its high D3 binding
affinity, because a moderate Ki value of 69 nM is obtained for D3 receptor, while only a
weak value of 1380 nM is found for D2 receptor at the high affinity binding sites[24]. BP 897
is a potent (Ki <10 nM) dopamine D3 receptor compound and a high selectivity for the
dopamine D3 versus D2 receptors (70-fold) developed for the treatment of cocaine abuse
and craving[25]. Phenylpiperazine moiety has particularly been developed as an important
pharmacophore for the selective D3 receptor ligand[26, 27]. Through the hybridization of
the pharmacophores, we hope to get several compounds with high D3R binding affinity and
D3/D2 selectivity.
2. Chemistry
As summarized in Table 1, 16 compounds (1a-2h) were synthesized. The synthetic routes
were illustrated in Schemes 1 and 2.
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Synthesis of the key intermediate 10 of the target compounds is illustrated in Scheme 1.
Treatment of isochroman with benzoyl chloride in the presence of zinc chloride gave 4 with
a yield of 99%, which was oxidized by dimethyl sulfoxide to obtain 5 in 67% yield. Compound
5 was converted to nitrostyrene 6 (up to 98%) in the presence of nitromethane and
ammonium acetate in acetic acid[28]. Cyclization of 6 using ferric chloride and acetyl
chloride in dichloromethane gave 7 in 59% yield. Compound 7 was reduced by hydrazine
hydrate in the presence of Pd/C, and subsequently hydrolyzed under basic conditions to
produce 8 with a yield of 71%[29]. Treatment of 8 with p-toluenesulfonyl chloride and
pyridine in dichloromethane gave 9 in 86% yield, of which subsequent reaction with
n-propylamine under N2 gas gave the key intermediate 10 in 60% yield.
Halogenation of diethanolamine 11 gave 12 in 89% yield. Cyclization of 12 with various
substituted aniline produced 13a-13k that were subsequently neutralized with sodium
hydroxide to obtain 14a-14k. Condensation of 14a-14k with 1-bromo-2-chloroethane or
1-bromo-3-chloropropane yielded 15a-15h and 16a-16h. Aminolysis of 15a-15h and
16a-16h was performed using intermediate 10 to afford the corresponding target
compounds 1a-2h (Scheme 2).
3. Results and discussion
3.1 Rational design for hybrid analogues
In our effort to design and develop selective and novel ligands for the D3 receptor which
was based on the crystal structure of the human D3R[19], we adopted a hybrid approach by
merging ropinirole and BP897 and further optimized hybrids by incorporating piperazine
fragments with various subtituents into the ropinirole moiety as shown in Fig. 2. Interaction
of the phenyl piperazine fragment with the dopamine D3 receptor would generate binding
affinity, and the ropinirole moiety was expected to impart the selectivity for the D3 receptor
by occupying extracellular binding pocket of the D3 receptor[30-31]. Furthermore,
arylpiperazine derivatives may enhance the physicochemical properties of compounds to
penetrate the blood brain barrier, and show the desired CNS efficacy[32]. On the basis of
the crystal structure of the human D3R[19], as well as the basic design principals of
combination, we have devised and synthesized novel indoline-2-ones derivatives (Fig. 2): (1)
introduction of two important moiety of ropinirole and BP897; (2) connection of the two
moiety with a carbon-chain containing 2-3 carbon atoms in order to adjust the spatial
distance of the two fragments; and (3) various substituted phenylpiperazines were also
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investigated. Our objective was to determine whether these compounds favor affinity and
selectivity for the D3 receptor.
3.2 binding affinity of the target compounds
All the target compounds (1a-2h) were subjected to competitive binding assays for the
human dopamine receptor 3 (D3R) and receptor 2 (D2), and The Ki values of binding assays
were evaluated using BP 897 as a positive control. As shown in Table 1, some of the
compounds show good binding affinities for the D3 receptor and high D3R selectivities over
D2R. We inferred that both of the two fragments could probably make docking with
corresponding cavity in the D3 receptor.
By contrast, we found that the affinities of the second series compounds were better
than that of the first series, suggesting that it was associated with the length of the
carbon-chain between the two fragments. The compounds containing one three-carbon
linker are more likely to enter the cavity to dock with the D3 receptor. Moreover, after a
close inspection, we also found that compounds 2a, 2c, 2e and 2f-2h demonstrated good
affinities and selectivity for the D3 receptor (Ki < 10 nM). In particular, 2h has a Ki value of
1.05 nM for its binding affinity to the D3 receptor and is 197-fold more selective for D3R
over the D2 receptor.
The binding affinity of the resulting hybrid analogues appeared to be related to the
space structure and the electronic effect of the substituents on the phenyl ring on a
nitrogen of the piperazine group. It is worth pointing out that compound 2c without
substituent group on the benzene ring had a high binding affinity for the D3 receptor. We
propose that the phenyl piperazine moiety might easily enter the binding pocket of the D3
receptor. Moreover, compounds with electron donating groups at 4 position, and, at 3 and 4
positions of the phenyl ring also had high binding affinities for the D3R and high selectivity
for the D3R over the D2R. We inferred that the phenyl ring with electron donating groups at
the 3 or/and 4 positions could easily enter the binding pocket of the D3R, and the groups on
the phenyl ring were able to interact with the corresponding active sites of the D3R,
suggesting that the pocket surface is electron-deficient.
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4. Conclusion
In our study, adopting a hybrid approach, two series of novel hybrid analogues have
been designed and synthesized. The target compounds were assayed for their Ki values
against the D3R and D2R. Most tested compounds exhibited evident affinities to the D3R at
low nM concentrations while 1a, 1d and 2b manifested affinities to the D3R at a range of a
mid to high nM concentrations. The assay results show that compounds could induce good
binding affinities to the D3R when the linker is n-propylene. Furthermore, the affinity is
affected by the presence of a substituent on the phenyl ring: the electron donating groups
at the 3 or/and 4 positions of the phenyl ring lead to a significant improvement in affinity.
This study may provide valuable information for further optimization of these two series of
compounds for the development of the D3R ligand with an excellent potency and selectivity.
5. Experimental protocols
5.1 Synthesis
All reagents were purchased from commercial sources and used without further
purification. Melting points were measured on an RY-1 hot-stage microscope, and the
thermometer was uncorrected. 1H NMR and 13C NMR spectra were recorded in CDCl3 on a
Bruker-ACF 300/500 spectrometer; chemical shifts (d) are reported in parts per million
(ppm) relative to tetramethylsilane (TMS), used as an internal standard. Mass spectra (MS)
were obtained from Agilent 1100LC/MS Spectrometry Services. IR spectra were run on FI-IR
Spectrometer (PerkineElmer). Elementary analyses were performed on Elementar Vario EL
III instrument. All compounds were
routinely checked by TLC with silica gel GF-254 glass plates and viewed under UV light at 254
nm.
5.1.1 Synthesis of 2-(chloromethyl) phenethyl benzoate (4)
To a stirred solution of compound 3 (65.0 g, 484 mmol) in CH2Cl2 (150 mL) was added
ZnCl2 (1.95 g, 14.3 mmol). When the resulting mixture was heated to reflux, PhCOCl (71.5 g,
509 mmol) was dropped in slowly. The resulting mixture was refluxed with stirring for 1.5 h
and then cooled to room temperature. After that, the mixture was washed with water
(3×100 mL), and then dried over Na2SO4. Evaporation of the solvent in vacuo afforded the
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title compound (132 g, 99%) . 1H NMR (300 MHz, CDCl3), δH, ppm: 3.23 (t, J = 7.2 Hz, 2H),
4.58 (t, J = 7.2 Hz, 2H), 4.72 (s, 2H), 7.20-7.30 (m, 3H), 7.38 (d, J = 7.3 Hz, 1H), 7.44 (t, J = 7.7
Hz, 2H), 7.56 ( t, J = 7.3 Hz, 1H), 8.02 (d, J = 7.3 Hz, 2H).
5.1.2 Synthesis of 2-formyl phenethyl benzoate (5)
To a stirred solution of compound 4 (2.70 g, 9.83 mmol) in 25 mL DMSO was added
sodium bicarbonate (1.67 g, 19.9 mmol). The resulting mixture was stirred at 110-120 °C for
1.5 h. Thereafter, the mixture was filtered and distilled under vacuum to remove the
solvent. The residue obtained was diluted with water (10 mL) and exacted with
dichloromethane (3×10 mL). The organic layers were combined, washed with water (2×10
mL). After drying and filtration, the organic solution was concentrated in vacuo to afford the
crude title compound. To a mixture of sodium bisulfite (8.64 g, 83.0 mmol), water (12 mL)
and ethanol (7.2 mL) was added the crude product above. The resulting mixture was stirred
at 10 °C for 30 min, and a thick white precipitate was produced. The solid was collected with
a pump, washed with cold dichloromethane (2×6 mL), and dried. To a mixture of sodium
bicarbonate (3.0 g), water (40 mL) and dichloromethane (15 mL) was added the white solid.
The resulting mixture was stirred at rt. for 2 h. The aqueous layer was exacted with
dichloromethane (2×20 mL). The organic layers were combined, washed with water (2×20
mL) and saturated brine (20 mL), and the organic solution was concentrated in vacuo to
afford 1.67 g (67%) of the title compound as virescent oil. 1H NMR (300 MHz, CDCl3), δH,
ppm: 3.53 (t, J = 6.7 Hz, 2H), 4.57 (t, J = 6.7 Hz, 2H), 7.37-7.48 (m, 4H), 7.53 (t, J = 7.3 Hz, 2H),
7.84 (d, J = 7.4 Hz, 1H), 7.97 (d, J = 7.3 Hz, 2H), 10.26 (s, 1H).
5.1.3 Synthesis of 2-(2-nitrovinyl) phenethyl benzoate (6)
A mixture of compound 5 (1.78 g, 7.0 mmol), nitromethane (1.35 g, 22.1 mmol), glacial
acetic acid (22 mL) and ammonium acetate (1.37 g, 17.8 mmol) was refluxed with stirring for
8-10 h. After that, the mixture was diluted with water (40 mL), and then extracted with
dichloromethane (3×40 mL). The combined organic layers were washed with water (3×40
mL) and saturated brine (2×30 mL). After drying (Na2SO4) and filtration, the solvent was
removed in vacuo to afford 2.04 g (98%) of the title compound as a brown viscous liquid. 1H
NMR (300 MHz, CDCl3), δH, ppm: 3.26 (t, J = 6.7 Hz, 2H), 4.53 (t, J = 6.7 Hz, 2H), 7.32 (t, J =
7.5 Hz, 1H), 7.41 (t, J = 7.6 Hz, 3H), 7.46 (d, J = 4.9 Hz, 1H), 7.53 (m, 3H), 7.97 ( m, 2H), 8.45
(d, J = 13.5 Hz, 1H).
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5.1.4 Synthesis of 2-(3-Chloro-2-oxoindolin-4-yl) ethyl benzoate (7)
A mixture of dichloromethane (50 mL) and ferric chloride (15.9 g, 98.0 mmol) was stirred
with ice-salt bath cooling, and acetyl chloride (7.69 g, 98.0 mmol) was slowly dropped into
the mixture, keeping the temperature around -5 °C. Thereafter, compound 6 (7.28 g, 24.5
mmol) in 30 mL of dichloromethane was slowly added. The resulting mixture was stirred at
-5-0 °C for 2 h, and then water (80 mL) was added. After that, the mixture was stirred at 30
°C for 1 h, and allowed to separate the layers. The aqueous layer was extracted with
dichloromethane (2×100 mL). The organic layers were combined, washed with water (2×100
mL) and saturated brine (2×100 mL). After drying and filtration, the solution was
concentrated under reduced pressure to a volume of about 70 mL, and petroleum (35 mL)
was added. The resulting mixture was cooled to 0-5 °C for 1 h. After that, the product was
collected with a pump and washed with a cold mixture (20 mL) of dichloromethane and
petroleum (2: 1, v/v), and then dried in vacuo at 65 °C overnight to afford 4.58 g (59%) of the
title compound as a off-white solid. mp. 154-155 °C. 1H NMR (300 MHz, DMSO-d6), δH, ppm:
3.15 (m, 2H), 4.56 (t, J = 6.7 Hz, 2H), 5.69 (s, 1H), 6.76 (d, J = 7.7 Hz, 1H), 6.99 (d, J = 7.8 Hz,
1H), 7.28 (t, J = 7.8 Hz, 1H), 7.52 (t, J = 7.6 Hz, 2H), 7.66 (t, J = 7.4 Hz, 1H), 7.94 (d, J = 7.3 Hz,
2H), 10.76 (s, 1H).
5.1.5 Synthesis of 4-(2-hydroxyethyl)-1,3-dihydroindol-2-one (8)
A mixture of compound 7 (1.20 g, 3.80 mmol), 10% Pd/C (0.075 g, 0.070 mmol) and 15 mL
methanol was stirred and heated to reflux. Thereafter, hydrazine hydrate was slowly
dropped into the mixture at a rate to control refluxing, and the mixture was refluxed for 1 h.
Sodium hydroxide (8.10 g, 202 mmol) dissolved in water (33 mL) was added, and the
mixture was refluxed for additional 1 h. The hot mixture was filtered to remove the catalyst,
and the filtrate was concentrated under reduced pressure to remove most of the methanol.
After that, the residue was allowed to stand in the refrigerator for 2 h, and the product was
collected with a pump, washed with cold water (2×5 mL) and dried in vacuo at 65 °C
overnight to afford 0.48 g (71%) of the title compound as a colorless crystal. mp. 146-147 °C.
IR (KBr) δmax (cm-1): 3261, 3166, 1682, 1618, 1608; 1H NMR (300 MHz, DMSO-d6), δH, ppm:
2.64 (t, J = 7.0 Hz, 2H), 3.41 (s, 2H), 3.59 (t, J = 6.9 Hz, 2H), 4.56 (t, J = 5.2 Hz, 1H), 6.64 (d, J =
7.6 Hz, 1H), 6.77 (d, J = 7.7 Hz, 1H), 7.07 (t, J = 7.7 Hz, 1H), 10.23 (br, s, 1H); 13C NMR (75
MHz, DMSO-d6), δ: 34.8, 36.3, 61.0, 106.9, 121.9, 124.9, 127.3, 135.7, 143.3, 176.3; Anal.
Calcd for C10H11NO2 (%): C, 67.78; H, 6.26; N, 7.90. Found: C 67.73, H 6.35, N, 7.69.
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5.1.6 Synthesis of 2-(2-oxoindolin-4-yl)ethyl 4-methylbenzenesulfonate (9)
To a stirred mixture of compound 8 (2.00 g，11.29 mmol) and Py (9 mL) was addeda
solution of TsCl (3.02 g, 15.84 mmol) in dichloromethane (9 mL ) at 5 °C. The resulting
mixture was stirred at 5-10 °C for 2 h, and then a mixture of H2O (10 mL), CH2Cl2 (9 mL) and
conc. HCl (11 mL) was slowly dropped in. After that, the mixture was stirred for 0.5 h,
followed by separating the layers. The aqueous layer was extracted with CH2Cl2 (2×20 mL),
The organic layers were combined, washed with water (2×30 mL) and saturated brine (2×30
mL). After drying (anhydrous Na2SO4) and filtration, the solution was concentrated under
reduced pressure to a volume of about 20 mL, and the resulting mixture was cooled to 0-5
°C for 1 h. After that, the precipitate was collected with a pump, and dried to afford light
yellow solid (3.22 g, 86%). mp. 128-129 °C. 1H NMR (300 MHz, DMSO-d6), δH, ppm: 2.41 (s, 3
H), 2.86 (t, J = 6.9 Hz, 2 H), 3.30 (s, 2 H), 4.25 (t, J = 6.8 Hz, 2 H), 6.79 (m, 2 H), 7.10-7.29 (m, 3
H), 7.64 (d, J = 7.4 Hz), 9.46 (s, 1 H). MS: 332.1 [M+H]+.
5.1.7 Synthesis of 4-(2-(propylamino)ethyl)indolin-2-one (10)
Compound 9 (9.08 g, 27.40 mmol) was dissolved in absolute alcohol (85 mL), to this
solution was added slowly n-propylamine (85 mL) with ice-water bath under an atmosphere
of N2. The mixture was stirred for 5 min at 0 °C, and then refluxed for 1.5 h. Solvent was
evaporated under reduced pressure to get crude product, which was added to water (200
mL) and stirred for 30 min at room temperature. After the pH adjusted to 11 with 20%
NaOH at 0 °C , the mixture was extracted with CH2Cl2 (150 mL×3). The organic phase was
washed with water (150 mL×2) and brine (150 mL×2), and then dried with anhydrous
Na2SO4. The solvent was removed under vacuum and the brown crude product was purified
by column chromatography on silica gel. eluting with dichloromethane: methanol:
triethylamine (150: 1: 2) to afford brown viscous product (3.59 g，60 %). 1H NMR (300 MHz,
DMSO-d6), δH, ppm: 0.85 (t, J = 7.4 Hz, 3H), 1.36-1.43 (m, 2H), 2.45-2.51 (m, 3H), 2.61 (t, J =
6.81 Hz, 2H), 2.68-2.74 (m, 2H), 3.43 (s, 2H), 6.64 (d, J = 7.6 Hz, 1H), 6.77 (d, J = 7.7 Hz, 1H),
7.08 (t, J = 6.81 Hz, 1H), 10.31(br, s, 1H); MS: 219.1 [M+H]+.
5.1.8 Synthesis of bis(2-chloroethyl)amine hydrochloride (12)
To a stirred mixture of thionyl chloride (128 mL, 1.76 mol) and chloroform (80 mL) was
added dropwise a solution of diethanolamine (40 mL, 0.417 mol) in chloroform (68 mL) in 3
h. The resulting mixture was stirred at room temperature for 3 h. After that, the mixture
was heated to reflux for 0.5 h, and then cooled to room temperature. The precipitate
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obtained was filtered, washed with cold chloroform and dried to yield white solid (66g,
89%). mp: 214-215 °C([33], mp: 207-209 °C). 1H NMR (300 MHz, DMSO-d6), δH, ppm:
3.19-3.34 (m, 4 H), 3.72-3.93 (m, 4 H), 9.84 (s, 1 H). MS: 142.0 [M+I-HCl]+.
5.1.9 General process for the synthesis of the compounds 13a-13k
To a stirred mixture of compound 12 (30 g，0.168 mol) and n-BuOH (130 mL) was added
slowly a solution of substituted phenylamine (0.153 mol) in n-BuOH (20 mL), and heated at
reflux for 24 h, to this solution was added K2CO3 (23 g，0.168 mol), and refluxed for another
48 h. The hot mixture was filtered, and the deep red liquor was allowed to stand in the
refrigerator overnight. The precipitate was then collected by filtration, washed with cold
n-BuOH and dried to afford 13a-13k.
Compounds 13a-13k were characterized as follows.
5.1.9.1 Synthesis of 1-(m-tolyl)piperazine hydrochloride (13a). Off-white solid, yield: 64%. 1H
NMR (300 MHz, DMSO-d6), δH, ppm: 2.21 (s, 3 H), 3.16-3.35 (m, 8 H), 6.91-7.19 (m, 4 H),
9.50 (s, 1 H). MS: 177.1 [M+I-HCl]+.
5.1.9.2 Synthesis of 1-(2,3-dimethylphenyl)piperazine hydrochloride(13b). White solid, yield:
65%, mp: 286-290 °C ( [34] Lit. 294 °C). 1H NMR (300 MHz, CDCl3), δH, ppm: 2.18 (s, 3 H), 2.32
(s, 3 H), 2.60-3.37 (m, 8 H), 6.68-7.76 (m, 2 H), 7.13 (m, 1 H), 9.52 (s, 1 H). MS: 191.2
[M+I-HCl]+.
5.1.9.3 Synthesis of 1-(3-methoxyphenyl)piperazine hydrochloride (13c). White solid, yield:
61%. 1H NMR (300 MHz, DMSO-d6), δH, ppm: 3.25-3.49 (m, 8 H), 3.78 (s, 3 H), 6.45-6.57 (m,
2 H), 7.15-7.19 (m, 1 H), 9.58(, 1 H). MS: 193.1 [M+I-HCl]+.
5.1.9.4 Synthesis of 1-(2-ethylphenyl)piperazine hydrochloride (13d). Off-white solid, yield:
56%, mp: 251-254 °C ( [35] Lit. 252 °C). 1H NMR (300 MHz, CDCl3), δH, ppm: 1.26 (s, 3 H),
2.50-2.77 (m, 6H), 3.48 (m, 4 H), 6.58-6.73 (m, 2 H), 6.89-7.25 (m, 2 H), 9,62 (s, 1 H). MS:
191.2 [M+I-HCl]+.
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5.1.9.5 Synthesis of 1-(4-chlorophenyl)piperazine hydrochloride (13e). White solid, yield:
72%, mp: 272-276 °C ( [36] Lit. 275-278 °C). 1H NMR (300 MHz, CDCl3), δH, ppm: 3.18-3.52 (m,
8H), 6.95 (m, 2H), 7.22 (m, 2H), 9.50 (s, 1H ). MS: 197.1 [M+I-HCl]+.
5.1.9.6 Synthesis of 1-(4-(trifluoromethoxy)phenyl)piperazine hydrochloride (13f). Off-white
solid, yield: 60%. 1H NMR (300 MHz, CDCl3), δH, ppm: 3.09-3.22 (m, 4 H), 3.35-3.44 (m, 4 H),
6.80 (m, 2 H), 7.24 (m, 2 H), 9.46 (s, 1 H). MS: 247.1 [M+I-HCl]+.
5.1.9.7 Synthesis of 1-phenylpiperazine hydrochloride (13g). Light red solid, yield: 71%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.75-2.81 (m, 4H), 3.46-3.58 (m, 4H), 6.65-7.10 (m, 5H),
9.45 (s, 1H). MS: 163.1 [M+I-HCl]+.
5.1.9.8 Synthesis of 1-(3,4-dimethylphenyl)piperazine hydrochloride (13h). White solid, yield:
63%, mp: 170-172 °C ( [34] Lit. 173 °C). 1H NMR (300 MHz, CDCl3), δH, ppm: 2.18 (s, 3H), 2.36
(s, 3H), 2.98-3.40 (m, 8 H), 6.69 (m, 1 H), 6.86-6.94 (m, 2 H), 9.58 (s, 1 H). MS: 191.2
[M+I-HCl]+.
5.1.9.9 Synthesis of 1-(p-tolyl)piperazine hydrochloride (13i). White solid, yield: 65%. 1H NMR
(300 MHz, CDCl3), δH, ppm: 2.25 (s, 3H), 3.09-3.30 (m, 8H), 6.95-7.13 (m, 4H), 9.50 (s, 1 H).
MS: 177.1 [M+I-HCl]+.
5.1.9.10 Synthesis of 1-(2,6-dimethylphenyl)piperazine hydrochloride (13j). White solid,
yield: 68%, mp: 236-239 °C ( [34] Lit. 240 °C). 1H NMR (300 MHz, CDCl3), δH, ppm: 2.30 (s, 6
H), 3.16-3.42 (m, 8H), 6.82-6.89 (m, 1 H), 7.05-7.10 (m, 2H), 9.38 (s, 1 H). MS: 191.2
[M+I-HCl]+.
5.1.9.11 Synthesis of 1-(o-tolyl)piperazine hydrochloride (13k). Off-white solid, yield: 58%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.18 (s, 3 H), 3.14-3.32 (m, 8 H), 6.98-7.16 (m, 4 H), 9.78 (s,
1 H). MS: 177.1 [M+I-HCl]+.
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5.1.10 General process for the synthesis of the compounds 14a-14k
Different substituted phenyl piperazine hydrochloride (0.115 mol) was added into stirred
water (200 mL), and the pH value was adjusted to 11-12 with 40% NaOH. The mixture was
extracted with ethyl acetate (2×200 mL), and the combined extracts were washed with
water (80 mL) and brine (80 mL) respectively. After drying with anhydrous Na2SO4, the
solvent was removed under vacuum to afford the compounds 14a-14k.
Compounds 14a-14k were characterized as follows.
5.1.10.1 Synthesis of 1-(m-tolyl)piperazine (14a). Light yellow oil, yield: 92%. 1H NMR (300
MHz, CDCl3), δH, ppm: 2.25 (s, 3 H), 2.95-3.21 (m, 8 H), 6.86 (m, 1 H), 7.12-7.18 (m, 3 H). MS:
177.1 [M+H]+.
5.1.10.2 Synthesis of 1-(2,3-dimethylphenyl)piperazine (14b). Light yellow oil, yield: 96%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.10 (s, 3 H), 2.25 (s, 3 H), 2.37 (s, 1 H), 2.52-3.15 (m, 8 H),
6.59-6.72 (m, 2 H), 7.04 (m, 1 H). MS: 191.2 [M+H]+.
5.1.10.3 Synthesis of 1-(3-methoxyphenyl)piperazine (14c). Light yellow oil, yield: 95%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.32 (s, 1 H), 2.96-3.17 (m, 8 H), 3.74 (s, 3 H), 6.39-6.59 (m,
2 H), 7.11 (m, 1 H). MS: 193.1 [M+H]+.
5.1.10.4 Synthesis of 1-(2-ethylphenyl)piperazine (14d). Light yellow oil, yield: 95%. 1H NMR
(300 MHz, CDCl3), δH, ppm: 1.18 (s, 3 H), 2.36 (s, 1 H), 2.46-2.71 (m, 6 H), 2.96-3.07 (m, 4 H),
6.48-6.62 (m, 2 H), 6.76-7.16 (m, 2H). MS: 191.2 [M+H]+.
5.1.10.5 Synthesis of 1-(4-chlorophenyl)piperazine (14e). Light yellow oil, yield: 93%. 1H NMR
(300 MHz, CDCl3), δH, ppm: 2.32 (s, 1H), 3.08-3.25 (m, 8H), 6.90 (m, 2H), 7.18 (m, 2H). MS:
197.1 [M+H]+.
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5.1.10.6 Synthesis of 1-(4-(trifluoromethoxy)phenyl)piperazine (14f). Light yellow oil, yield:
93%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.84-2.90 (m, 4 H), 3.31-3.34 (m, 4 H), 6.68 (s, 2 H),
7.02 (s, 2 H). MS: 247.1 [M+H]+.
5.1.10.7 Synthesis of 1-phenylpiperazine (14g). Light yellow oil, yield: 95%. 1H NMR (300
MHz, DMSO-d6), δH, ppm: 2.25 (s, 1H), 2.88-3.02 (m, 8 H), 6.75 (s, 1H), 6.86-7.23 (m, 4H).
MS: 163.1 [M+H]+.
5.1.10.8 Synthesis of 1-(3,4-dimethylphenyl)piperazine (14h). Light yellow oil, yield: 95%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.12 (s, 6 H), 2.39 (s, 1 H), 2.85-3.34 (m, 8 H), 6.58 (m, 1 H),
6.76-6.82 (m, 2 H). MS: 191.2 [M+H]+.
5.1.10.9 Synthesis of 1-(p-tolyl)piperazine (14i). Light yellow oil, yield: 96%. 1H NMR (300
MHz, CDCl3), δH, ppm: 2.14 (s, 1 H), 2.30 (s, 3H), 2.85-3.28 (m, 8H), 6.63-7.01 (m, 4H). MS:
177.1 [M+H]+.
5.1.10.10 Synthesis of 1-(2,6-dimethylphenyl)piperazine (14j). Light yellow oil, yield: 96%. 1H
NMR (300 MHz, CDCl3), δH, ppm: 2.10 (s, 6 H), 2.32 (s, 1H), 3.16-3.29 (m, 8H), 6.68-6.96 (m,
3H). MS: 191.2 [M+H]+.
5.1.10.11 Synthesis of 1-(o-tolyl)piperazine (14k). Light yellow oil, yield: 94%. 1H NMR (300
MHz, CDCl3), δH, ppm: 2.28 (s, 3 H), 3.05-3.23 (m, 8 H), 6.80-6.94 (m, 2 H), 7.11-7.24 (m, 2 H).
MS: 177.1 [M+H]+.
5.1.11 General process for the synthesis of the compounds 15a-15h and 16a-16h
K2CO3 (2.56 g, 18.5 mmol) was added to the solution of different substituted phenyl
piperazine (7.40 mmol) in acetone (25 mL), to this solution was added slowly
1-Bromo-2-chloroethane or 1-Bromo-3-chloropropane (11.1 mmol) by droping at 0 °C. The
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mixture was stirred for 3 h at 35 °C, and then heated at reflux for 10 h. After cooled to room
temperature the solvent was removed under vacuum. The crude product was purified by
column chromatography on silica gel. eluting with petroleum ether : ethyl acetate (3:1) to
afford the compounds 15a-15h and 16a-16h.
Compounds 15a-15h and 16a-16h were characterized as follows.
5.1.11.1 Synthesis of 1-(2-chloroethyl)-4-(m-tolyl)piperazine (15a). Light yellow oil, yield:
65%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.31 (s, 3 H), 2.74 (m, 6 H), 3.20-3.29 (m, 4 H),
3.66-3.71 (m, 2 H), 6.67 (m, 1 H), 6.90-7.31 (m, 3 H). MS: 239.1 [M+H]+.
5.1.11.2 Synthesis of 1-(2-chloroethyl)-4-(2,3-dimethylphenyl)piperazine (15b). Light yellow
oil, yield: 64%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.27 (s, 3 H), 2.33 (s, 3 H), 2.76 (m, 4H),
3.19-3.32 (m, 4 H), 3.61-3.74 (m, 4 H), 6.67-6.74 (m, 2 H), 6.88-7.09 (m, 2 H). MS: 253.1
[M+H]+.
5.1.11.3 Synthesis of 1-(2-chloroethyl)-4-(3-methoxyphenyl)piperazine (15c). Light yellow oil,
yield: 63%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.69 (m, 4 H), 3.16-3.35 (m, 4 H), 3.63-3.80 (m, 7
H), 6.38-5.54 (m, 3 H), 7.20 (m, 1 H). MS: 255,1 [M+H]+.
5.1.11.4 Synthesis of 1-(2-chloroethyl)-4-(2-ethylphenyl)piperazine (15d). Light yellow oil,
yield: 62%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.17 (s, 3 H), 2.58-2.65 (m, 4 H), 3.21-3.42
(m, 4 H), 3.55-3.61 (m, 2 H), 3.66-3.74 (m, 4 H), 6.64-6.79 (m, 2 H), 6.86-7.21 (m, 2 H). MS:
253.1 [M+H]+.
5.1.11.5 Synthesis of 1-(2-chloroethyl)-4-(4-chlorophenyl)piperazine (15e). Light yellow oil,
yield: 63%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.65-2.69 (m, 4 H), 3.17-3.38 (m, 4 H),
3.57-3.71 (m, 4 H), 6.80-6.87 (m, 2 H), 7.03-7.12 (m, 2 H). MS: 259.1 [M+H]+.
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5.1.11.6 Synthesis of 1-(2-chloroethyl)-4-(4-(trifluoromethoxy)phenyl)piperazine (15f). Light
yellow oil, yield: 56%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.81 (m, 4 H), 3.19-3.33 (m, 4 H),
3.56-3.68 (m, 4 H), 6.85-7.24 (m, 4 H). MS: 309.1 [M+H]+.
5.1.11.7 Synthesis of 1-(2-chloroethyl)-4-phenylpiperazine (15g). Light yellow oil, yield: 61%.
1H NMR (300 MHz, CDCl3), δH, ppm: 2.72(m, 4 H), 3.21-3.30 (m, 4 H), 3.69-3.77 (m, 4 H),
6.80-7.01 (m, 3 H), 7.27 (m, 2 H). MS: 225.1 [M+H]+.
5.1.11.8 Synthesis of 1-(2-chloroethyl)-4-(3,4-dimethylphenyl)piperazine (15h). Light yellow
oil, yield: 59%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.18 (s, 3 H), 2.21 (s, 3 H), 2.73 (m, 4 H),
3.18-3.34 (m, 4 H), 3.57-3.69 (m, 4 H), 6.72-6.79 (m, 1 H), 6.90-7.14 (m, 2 H). MS: 253.1
[M+H]+.
5.1.11.9 Synthesis of 1-(3-chloropropyl)-4-(p-tolyl)piperazine (16a). Light yellow oil, yield:
74%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.99 (m, 2H), 2.33 (s, 3 H), 2.51-2.58 (m, 4H), 2.67
(m, 4 H), 3.15 (s, 4 H), 3.68 (t, J = 6.6 Hz, 2 H), 6.84-6.91 (m, 2 H), 6.99-7.10 (m, 2 H). MS:
253.1 [M+H]+.
5.1.11.10 Synthesis of 1-(3-chloropropyl)-4-(2,6-dimethylphenyl)piperazine (16b). Light
yellow oil, yield: 69%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.04 (m, 2 H), 2.35 (s, 6 H),
2.57-2.62 (m, 6 H), 3.17-3.21 (m, 4 H), 3.63-3.70 (m, 2 H), 6.95-7.04 (m, 3 H). MS: 267.2
[M+H]+.
5.1.11.11 Synthesis of 1-(3-chloropropyl)-4-phenylpiperazine (16c). Light yellow oil, yield:
59%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.98 (m, 2 H), 2.48-2.63 (m, 6 H), 3.18-3.21 (m, 4
H), 3.59-3.64 (m, 2 H), 6.82-6.91 (m, 3 H), 7.20-7.26 (m, 2 H). MS: 239.1 [M+H]+.
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5.1.11.12 Synthesis of 1-(3-chloropropyl)-4-(2,3-dimethylphenyl)piperazine (16d). Light
yellow oil, yield: 63%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.98 (m, 2 H), 2.30 (s, 3 H), 2.36 (s,
3 H), 2.54-2.60 (m, 6 H), 3.20-3.25 (m, 4 H), 3.61-3.72 (m, 2 H), 6.88-7.02 (m, 3 H). MS: 267.2
[M+H]+.
5.1.11.13 Synthesis of 1-(3-chloropropyl)-4-(o-tolyl)piperazine (16e). Light yellow oil, yield:
61%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.01 (m, 2 H), 2.34 (s, 3 H), 2.55-2.76 (m, 6 H),
3.24-3.28 (m, 4 H), 3.64 (t, J = 6.6 Hz, 2 H), 6.67-6.84 (m, 2 H), 6.97-7.16 (m, 2 H). MS: 253.1
[M+H]+.
5.1.11.14 Synthesis of 1-(3-chloropropyl)-4-(4-(trifluoromethoxy)phenyl)piperazine (16f).
Light yellow oil, yield: 61%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.96 (m, 2 H), 2.58-2.67 (m,
6 H), 3.15-3.26 (m, 4 H), 3.65 (t, J = 6.7 Hz, 2 H), 6.83-6.91 (m, 2 H), 6.98-7.17 (m, 2 H). MS :
323.1 [M+H]+.
5.1.11.15 Synthesis of 1-(3-chloropropyl)-4-(3-methoxyphenyl)piperazine (16g). Light yellow
oil, yield: 66%. 1H NMR (300 MHz, CDCl3), δH, ppm: 1.99 (m, 2 H), 2.48-2.61 (m, 4 H), 3.17 (s,
4 H), 3.67 (t, J = 6.7 Hz, 2 H), 3.79 (s, 3 H), 6.83-7.06 (m, 4 H). MS: 269.1 [M+H]+.
5.1.11.16 Synthesis of 1-(3-chloropropyl)-4-(3,4-dimethylphenyl)piperazine (16h). Light
yellow oil, yield: 62%. 1H NMR (300 MHz, CDCl3), δH, ppm: 2.01 (m, 2 H), 2.48 (s, 6 H),
2.51-2.61 (m, 6 H), 3.10-3.15 (m, 4 H), 3.66 (t, J = 6.7 Hz, 2 H), 6.84-7.10 (m, 3 H). MS: 267.2
[M+H]+.
5.1.12 General process for the synthesis of the compounds 1a-1h and 2a-2h
Compound 10 (0.70 g, 3.21 mmol) and compound 15a-15h or 16a-16h (3.21 mmol) were
dissolved in acetonitrile (22 mL), to this solution was added K2CO3 (0.89 g, 6.44 mmol) and KI
(0.54 g, 3.25 mmol). The mixture was stirred for 8 h at 45 °C. The hot precipitate was filtered
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and the filtrate was evaporated under reduced pressure to get crude product, which was
purified by column chromatography on silica gel. eluting with dichloromethane: methanol:
three ethylamine (200: 0.1: 1) to afford the final product.
Compounds 1a-1h and 2a-2h were characterized as follows.
5.1.12.1 Synthesis of 4-(2-(propyl(2-(4-(m-tolyl)piperazin-1-yl)ethyl)amino)ethyl)
indol-in-2-one (1a). Brown sticky product, yield: 72%. 1H NMR (300 MHz, CDCl3), δH, ppm:
0.89 (t, J = 7.3 Hz, 3H), 1.43-1.58 (m, 2H), 2.30 (s, 3H), 2.54-2.82 (m, 10H), 3.17-3.41 (m, 8H),
3.49 (s, 2H), 6.66 (d, J = 7.3 Hz, 1H), 6.71-6.73 (m, 3H), 6.84 (d, J = 7.5 Hz, 1H), 7.14 (t, J = 7.5
Hz, 2H), 9.08 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.8, 20.2, 21.7, 30.8, 34.9, 51.4, 53.3,
53.7, 54.7, 56.5, 57.0, 113.1, 116.8, 120.5, 120.6, 122.7, 128.0, 128.1, 128.9, 135.3, 135.4,
135.4, 136.8, 138.7, 142.5, 142.7, 151.2, 151.3, 156.1, 177.4, 177.5; MS: 421.3 [M+H]+; Anal.
calcd. for C26H36N4O (%): C 74.25, H 8.63, N 13.32; found: C 74.12, H 8.60, N 13.41.
5.1.12.2 Synthesis of 4-(2-((2-(4-(2,3-dimethylphenyl)piperazin-1-yl)ethyl)(propyl)
amin-o)ethyl)indolin-2-one (1b). Grey solid, yield: 69%, mp: 116-118 °C. 1H NMR (300 MHz,
CDCl3), δH, ppm: 0.89 (t, J = 7.3 Hz, 3H), 1.43-1.55 (m, 2H), 2.21 (s, 3H), 2.25 (s, 3H), 2.50 (t, J
= 7.7 Hz, 2H), 2.54-2.71 (m, 12H), 2.91 (t, J = 4.2 Hz, 4H), 3.49 (s, 2H), 6.73 (d, J = 7.7 Hz, 1H),
6.84-6.92 (m, 3H), 7.06 (t, J = 7.7 Hz, 1H), 7.14 (t, J = 7.7 Hz, 1H), 9.32 (br, s, 1H); 13C-NMR
(75 MHz, CDCl3), δ: 11.9, 13.9, 20.3, 20.5, 31.0, 35.2, 51.5, 52.0, 54.2, 54.8, 56.6, 56.8, 107.5,
116.6, 122.7, 124.0, 124.9, 125.7, 127.9, 131.2, 137.0, 137.8, 142.5, 151.5, 177.7, 177.8; IR
(KBr, cm-1): 3283, 3060, 2948, 2813, 1687, 1616, 1580, 1512, 1459, 1378, 1241, 1142, 1061,
777, 724, 648; MS: 435.3 [M+H]+; Anal. calcd. for C27H38N4O (%): C 74.61, H 8.81, N 12.89;
found: C 74.51, H 8.74, N 12.96.
5.1.12.3 Synthesis of 4-(2-((2-(4-(3-methoxyphenyl)piperazin-1-yl)ethyl)(propyl)
amino)ethyl)indolin-2-one (1c). Brown sticky product, yield: 65%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.89 (t, J = 7.3 Hz, 3H), 1.43-1.52 (m, 2H), 2.47-2.53 (m, 4H), 2.62 (t, J = 4.7 Hz, 4H),
2.68-2.70 (m, 6H), 3.19 (t, J = 4.7 Hz, 4H), 3.48 (s, 2H), 3.78 (s, 3H), 6.41 (d, J = 8.0 Hz, 1H),
6.46 (s, 1H), 6.52 (d, J = 8.3 Hz, 1H), 6.71 (d, J = 7.7 Hz, 1H), 6.84 (d, J = 7.7 Hz, 1H), 7.11-7.18
(q, J = 7.3 Hz, 2H), 9.15 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.9, 20.3, 30.9, 35.1, 48.9, 51.5,
53.6, 54.7, 55.1, 56.5, 56.6, 102.4, 104.4, 107.5, 108.8, 122.7, 124.0, 128.0, 129.7, 137.0,
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142.5, 152.6, 160.5, 177.6; IR (KBr, cm-1): 3200, 3083, 2950, 2873, 2822, 1701, 1604, 1580,
1497, 1453, 1299, 1248, 1204, 1171, 1055, 774, 759, 719, 687, 650; MS: 437.2 [M+H]+; Anal.
calcd. for C26H36N4O2 (%): C 71.53, H 8.31, N 12.83; found: C 71.64, H 8.30, N 12.88.
5.1.12.4 Synthesis of 4-(2-((2-(4-(2-ethylphenyl)piperazin-1-yl)ethyl)(propyl)amino)
ethyl)indolin-2-one (1d). Brown sticky product, yield: 65%. 1H NMR (300 MHz, CDCl3), δH,
ppm: 0.89 (t, J = 7.3 Hz, 3H), 1.24 (t, J = 7.5 Hz, 3H), 1.43-1.55 (m, 2H), 2.48-2.57 (m, 4H),
2.64-2.71 (m, 12H), 2.92 (t, J = 4.4 Hz, 4H), 3.50 (s, 2H), 6.73 (d, J = 7.7 Hz, 1H), 6.85 (d, J =
7.8 Hz, 1H), 7.01-7.09 (m, 2H), 7.13-7.17 (m, 2H), 7.22 (t, J = 7.8 Hz, 1H), 9.19 (s, 1H);
13C-NMR (75 MHz, CDCl3), δ: 11.9, 14.8, 20.3, 23.3, 31.0, 35.2, 51.5, 52.5, 54.3, 54.8, 56.6,
56.8, 107.5, 119.9, 122.8, 123.8, 124.0, 126.4, 128.0, 128.8, 137.0, 139.2, 142.5, 151.2,
177.7; IR (KBr, cm-1): 3193, 3099, 3062, 3027, 2958, 2872, 1704, 1605, 1491, 1457, 1376,
1302, 1247, 1223, 1124, 762, 720, 651; MS m/z: 435.3[M+H]+; Anal. calcd. for C27H38N4O (%):
C 74.61, H 8.81, N 12.89; found: C 74.66, H 8.67, N 12.86.
5.1.12.5 Synthesis of 4-(2-((2-(4-(4-chlorophenyl)piperazin-1-yl)ethyl)(propyl)amino)
ethyl)indolin-2-one (1e). Grey solid, yield: 68%, mp: 136-137 °C. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.88 (t, J = 7.2 Hz, 3H), 1.44-1.52 (m, 2H), 2.50-2.70 (m, 14H), 3.15 (s, 4H), 3.49 (s,
2H), 6.72 (d, J = 7.6 Hz, 1H), 6.83 (t, J = 8.3 Hz, 3H), 7.11-7.19 (m, 3H), 9.19 (s, 1H); 13C-NMR
(75 MHz, CDCl3), δ: 11.9, 20.3, 31.0, 35.2, 49.0, 51.6, 53.5, 54.7, 56.5, 56.6, 107.5, 117.1,
122.8, 124.0, 124.4, 128.0, 128.9, 137.0, 142.5, 149.8, 177.6; IR (KBr, cm-1): 3211, 3066,
3039, 3019, 2948, 2873, 1669, 1603, 1498, 1451, 1299, 1245, 1128, 1082, 813, 769, 696,
658; MS: 441.2[M+H]+; Anal. calcd. for C25H33ClN4O (%): C 68.09, H 7.54, N 12.70; found: C
68.03, H 7.52, 12.76.
5.1.12.6 Synthesis of 4-(2-(propyl(2-(4-(4-(trifluoromethoxy)phenyl)piperazin-1-yl)
ethyl)amino)ethyl)indolin-2-one (1f). Brown sticky product, yield: 59%. 1H NMR (300 MHz,
CDCl3), δH, ppm: 0.89 (t, J = 7.3 Hz, 3H), 1.45-1.52 (m, 2H), 2.47-2.53 (m, 4H), 2.63 (t, J = 4.7
Hz, 4H), 2.68-2.71 (m, 6H), 3.17 (t, J = 4.6 Hz, 4H), 3.49 (s, 2H), 6.73 (d, J = 7.7 Hz, 1H),
6.83-6.88 (m, 3H), 7.08-7.16 (m, 3H), 9.39 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.9, 20.4,
31.0, 35.2, 49.1, 51.6, 53.6, 54.8, 56.6, 56.7, 107.5, 116.5, 121.9, 122.3, 122.8, 124.0, 128.0,
137.1, 141.9, 142.4, 150.0, 177.5; IR (KBr, cm-1): 3166, 3019, 2955, 2871, 2819, 1684, 1605,
1515, 1458, 1268, 1238, 1159, 1003, 832, 718, 646; MS: 491.2 [M+H]+; Anal. calcd. for
C26H33F3N4O2 (%): C 63.66 H 6.78 N 11.42; found: C 63.64, H 6.71, N 11.51.
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5.1.12.7 Synthesis of 4-(2-((2-(4-phenylpiperazin-1-yl)ethyl)(propyl)amino)ethyl)
indolin-2-one (1g). Grey solid, yield: 71%, mp: 113-114 °C. 1H NMR (300 MHz, CDCl3), δH,
ppm: 0.89 (t, J = 7.2 Hz, 3H), 1.44-1.56 (m, 2H), 2.47-2.53 (m, 4H), 2.64 (t, J = 4.6 Hz, 4H),
2.67-2.80 (m, 6H), 3.12-3.27 (m, 4H), 3.50 (s, 2H), 6.71 (d, J = 7.7 Hz, 1H), 6.83-6.88 (m, 2H),
6.92 (d, J = 8.0 Hz, 2H), 7.15 (t, J = 7.7 Hz, 1H), 7.26 (t, J = 7.6 Hz, 2H), 8.12 (s, 1H); 13C-NMR
(75 MHz, CDCl3), δ: 11.9, 20.4, 31.0, 35.1, 49.0, 51.6, 53.7, 54.8, 56.6, 56.7, 107.5, 116.0,
119.6, 122.8, 124.0, 128.0, 129.0, 137.1, 142.4, 151.2, 177.5; IR (KBr, cm-1): 3183, 3058,
3039, 3021, 2957, 2867, 1664, 1606, 1577, 1505, 1456, 1321, 1301, 1249, 1140, 1084, 753,
690, 656; MS: 407.3 [M+H]+; Anal. calcd. for C25H34N4O (%): C 73.85, H 8.43, N 13.78; found:
C 73.78, H 8.48 N 13.77.
5.1.12.8 Synthesis of 4-(2-((2-(4-(3,4-dimethylphenyl)piperazin-1-yl)ethyl)(propyl)
amino)ethyl)indolin-2-one (1h). Brown sticky product, yield: 70%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.88 (t, J = 7.2 Hz, 3H), 1.44-1.52 (m, 2H), 2.17 (s, 3H), 2.22 (s, 3H), 2.47-2.53 (m,
4H), 2.63-2.70 (m, 10H), 3.14 (s, 4H), 3.48 (s, 2H), 6.66-6.74 (m, 3H), 6.84 (d, J = 7.7 Hz, 1H),
7.00 (d, J = 8.1 Hz, 1H), 7.13 (t, J = 7.7 Hz, 1H), 9.22 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.9,
18.7, 20.1, 20.4, 31.0, 35.1, 49.6, 51.6, 53.7, 54.8, 56.6, 56.7, 107.5, 113.7, 118.0, 122.7,
124.0, 127.9, 128.0, 130.1, 137.0, 137.0, 142.5, 149.5, 177.6; IR (KBr, cm-1): 3186, 3080,
3025, 2948, 2856, 1702, 1605, 1569, 1505, 1455, 1307, 1242, 1140, 1091, 886, 804, 704,
660; MS: 435.3 [M+H]+; Anal. calcd. for C27H38N4O (%): C 74.61, H 8.81, N 12.89; found: C
74.74 H 8.79, 12.94.
5.1.12.9 Synthesis of 4-(2-(propyl(3-(4-(p-tolyl)piperazin-1-yl)propyl)amino)ethyl)
indolin-2-one (2a). Brown sticky product, yield: 67%. 1H NMR (300 MHz, CDCl3), δH, ppm:
0.88 (t, J = 7.2 Hz, 3H), 1.41-1.53 (m, 2H), 1.63-1.73 (m, 2H), 2.26 (s, 3H), 2.39 (t, J = 7.4 Hz,
2H), 2.46 (t, J = 7.5 Hz, 2H), 2.54 (t, J = 7.3 Hz, 2H), 2.60 (s, 4H), 2.67 (s, 4H), 3.15 (s, 4H), 3.47
(s, 2H), 6.71 (d, J = 7.7 Hz, 1H), 6.84 (d, J = 7.9 Hz, 3H), 7.06 (d, J = 8.0 Hz, 2H), 7.13 (t, J = 7.7
Hz, 1H), 9.28 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.9, 20.3, 20.3, 24.5, 30.9, 35.1, 49.6,
52.1, 53.2, 54.3, 56.1, 56.6, 107.5, 116.3, 122.7, 124.0, 127.9, 129.1, 129.5, 137.1, 142.5,
149.2, 177.6; IR (KBr, cm-1): 3368, 2954, 2815, 1687, 1610, 1577, 1511, 1459, 1451, 1237,
811, 720, 651; MS: 435.3 [M+H]+; Anal. calcd. for C27H38N4O (%): C 74.61, H 8.81, N 12.89;
found: 74.55, H 8.83, N 12.89.
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5.1.12.10 Synthesis of 4-(2-((3-(4-(2,6-dimethylphenyl)piperazin-1-yl)propyl)(propyl)
amino)ethyl)indolin-2-one (2b). Brown sticky product, yield: 71%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.90 (t, J = 7.2 Hz, 3H), 1.45-1.55 (m, 2H), 1.69-1.79 (m, 2H), 2.32 (s, 6H), 2.40 (t, J =
7.4 Hz, 2H), 2.45 (t, J = 7.5 Hz, 2H), 2.56 (t, J = 7.3 Hz, 2H), 2.61 (s, 4H), 2.72 (s, 4H), 3.16 (s,
4H), 3.48 (s, 2H), 6.75 (d, J = 7.7 Hz, 1H), 6.86 (d, J = 7.7 Hz, 1H), 6.94-6.97 (m, 3H), 7.15 (t, J
= 7.7 Hz, 1H), 8.34 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.7, 19.5, 19.9, 24.0, 30.5, 35.0,
49.2, 51.9, 52.8, 54.3, 55.8, 56.8, 107.7, 122.4, 123.9, 124.9, 127.8, 128.7, 136.5, 136.7,
142.8, 148.0, 177.3; IR (KBr, cm-1): 3423, 3060, 2944, 1678, 1606, 1550, 1476, 1460, 1248,
769, 721, 651; MS: 449.3 [M+H]+; Anal. calcd. for C28H40N4O (%): C 74.96, H 8.99, N 12.49;
found: C 75.08, H 8.93, N 12.44.
5.1.12.11 Synthesis of 4-(2-((3-(4-phenylpiperazin-1-yl)propyl)(propyl)amino)ethyl)
indolin-2-one (2c). Brown sticky product, yield: 64%. 1H NMR (300 MHz, CDCl3), δH, ppm:
0.92 (t, J = 7.2 Hz, 3H), 1.54-1.59 (m,2H), 1.75-1.85 (m, 2H), 2.45 (t, J = 7.0 Hz, 2H), 2.63-2.81
(m, 12H), 3.22 (s, 4H), 3.46 (s, 2H), 6.81 (d, J = 7.4 Hz, 1H), 6.86 (d, J = 7.4 Hz, 1H), 6.91-6.94
(m, 3H), 7.12 (t, J = 7.7 Hz, 1H), 7.23-7.30 (m, 2H), 9.71 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ:
11.7, 19.5, 24.2, 30.6, 35.5, 48.6, 51.4, 52.9, 53.3, 53.9, 55.1, 56.7, 107.9, 115.8, 120.4,
122.9, 124.2, 128.02, 129.1, 136.5, 142.8, 149.6, 177.1; MS: 421.3 [M+H]+; Anal. calcd. for
C26H36N4O (%): C 74.25, H 8.63, N 13.32; found: C 74.32, H 8.60, N 13.37.
5.1.12.12 Synthesis of 4-(2-((3-(4-(2,3-dimethylphenyl)piperazin-1-yl)propyl)(propyl)
amino)ethyl)indolin-2-one (2d). Brown sticky product, yield: 62%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.89 (t, J = 7.3 Hz, 3H), 1.43-1.55 (m, 2H), 1.65-1.75 (m, 2H), 2.22 (s, 3H), 2.27 (s,
3H), 2.39-2.49 (m, 4H), 2.53-2.69 (m, 10H), 2.91-2.94 (m, 4H), 3.48 (s, 2H), 6.72 (d, J = 7.7 Hz,
1H), 6.83-6.93 (m, 3H), 7.07 (t, J = 7.7 Hz, 1H), 7.15 (t, J = 7.7 Hz, 1H), 9.08 (s, 1H); 13C-NMR
(75 MHz, CDCl3), δ: 11.9, 13.9, 20.2, 20.5, 24.5, 30.8, 35.1, 52.0, 52.1, 53.7, 54.2, 56.0, 56.7,
107.5, 116.6, 122.7, 124.0, 124.8, 125.7, 127.9, 131.1, 137.1, 137.8, 142.5, 151.5, 177.6; IR
(KBr, cm-1): 3440, 3067, 3025, 2952, 2872, 1679, 1619, 1606, 1581, 1475, 1460, 1452, 1376,
1243, 1145, 1082, 779, 721, 651; MS: 449.4[M+H]+; Anal. calcd. for C28H40N4O (%): C 74.96, H
8.99, N 12.49; found: C 74.85, H 8.98, N 12.52.
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5.1.12.13 Synthesis of 4-(2-(propyl(3-(4-(o-tolyl)piperazin-1-yl)propyl)amino)ethyl)
indolin-2-one (2e). Brown sticky product, yield: 66%. 1H NMR (300 MHz, CDCl3), δH, ppm:
0.89 (t, J = 7.2 Hz, 3H), 1.44-1.51 (m, 2H), 1.64-1.74 (m, 2H), 2.30 (s, 3H), 2.41 (t, J = 7.2 Hz,
2H), 2.46 (t, J = 7.3 Hz, 2H), 2.54 (t, J = 7.4 Hz, 2H), 2.60 (s, 4H), 2.68 (s, 4H), 2.94 (s, 4H), 3.48
(s, 2H), 6.72 (d, J = 7.6 Hz, 1H), 6.84 (d, J = 7.7 Hz, 1H), 6.96 (t, J = 7.3 Hz, 1H), 7.02 (d, J = 7.8
Hz, 1H), 7.15-7.17 (m, 3H), 9.31 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.9, 17.8, 20.3, 24.6,
30.9, 35.1, 51.6, 52.1, 53.7, 54.3, 56.0, 56.7, 107.5, 118.9, 122.7, 123.0, 124.0, 126.5, 127.9,
130.9, 132.5, 137.1, 142.5, 151.4, 177.7; IR (KBr, cm-1): 3199, 3066, 3021, 2954, 2872, 1687,
1618, 1607, 1492, 1458, 1375, 1266, 1146, 1084, 777, 722, 650; MS: 435.2 [M+H]+; Anal.
calcd. for C27H38N4O (%): C 74.61, H 8.81, N 12.89; found: C 74.65, H 8.79, N 12.84.
5.1.12.14 Synthesis of 4-(2-(propyl(3-(4-(4-(trifluoromethoxy)phenyl)piperazin-1-yl)
propyl)amino)ethyl)indolin-2-one (2f). Brown sticky product, yield: 70%. 1H NMR (300 MHz,
CDCl3), δH, ppm: 0.89 (t, J = 7.2 Hz, 3H), 1.43-1.54 (m, 2H), 1.65-1.75 (m, 2H), 2.40 (t, J = 7.2
Hz, 2H), 2.51 (t, J = 7.5 Hz, 2H), 2.58-2.71 (m, 10H), 3.18 (t, J = 4.5 Hz, 4H), 3.45 (s, 2H),
6.81-6.89 (m, 4H), 7.08-7.14 (m, 3H), 9.64 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ: 11.7, 19.7,
23.9, 29.6,, 30.3, 35.1, 49.0, 51.8, 52.8, 53.0, 54.0, 55.7, 56.2, 108.0, 116.4, 121.8, 122.4,
124.0, 127.9, 136.1, 141.8, 142.9, 149.9, 177.1; IR (KBr, cm-1): 3392, 3079, 2955, 2874, 2818,
1697, 1618, 1607, 1512, 1457, 1380, 1264, 1159, 1085, 1008, 834, 807, 710, 647; MS: 505.2
[M+H]+; Anal. calcd. for C27H35F3N4O2 (%): C 64.27, H 6.99, N 11.10; found: C 64.16, H 6.99, N
11.14.
5.1.12.15 Synthesis of 4-(2-((3-(4-(3-methoxyphenyl)piperazin-1-yl)propyl)(propyl)
amino)ethyl)indolin-2-one (2g). Brown sticky product, yield: 65%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.89 (t, J = 7.0 Hz, 3H), 1.43-1.55 (m, 2H), 1.66-1.76 (m, 2H), 2.40 (t, J = 7.1 Hz, 2H),
2.51 (t, J = 7.4 Hz, 2H), 2.59-2.72 (m, 10H), 3.20 (s, 4H), 3.44 (s, 2H), 3.78 (s, 3H), 6.40 (d, J =
7.9 Hz, 1H), 6.46 (s, 1H), 6.53 (d, J = 8.0 Hz, 1H), 6.81 (d, J = 7.7 Hz, 1H), 6.87 (d, J = 7.6 Hz,
1H), 7.11 (t, J = 6.9 Hz, 1H), 7.16 (t, J = 7.8 Hz, 1H), 9.71 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ:
11.8, 19.9, 24.1, 30.5, 35.1, 48.8, 51.8, 52.9, 54.1, 55.1, 55.8, 56.3, 102.3, 104.3, 108.0,
108.7, 122.3, 123.9, 127.9, 129.6, 136.3, 142.9, 152.5, 160.4, 177.0; IR (KBr, cm-1): 3392,
3079, 2954, 2871, 2816, 1683, 1605, 1576, 1533, 1496, 1456, 1255, 1171, 1050, 1011, 801,
776, 689, 650; MS: 451.3 [M+H]+; Anal. calcd. for C27H38N4O2 (%): C 71.97, H 8.50, N 12.43;
found: C 71.99, H 8.52, N 12.36.
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5.1.12.16 Synthesis of 4-(2-((3-(4-(3,4-dimethylphenyl)piperazin-1-yl)propyl)(propyl)
amino)ethyl)indolin-2-one (2h). Brown sticky product, yield: 63%. 1H NMR (300 MHz, CDCl3),
δH, ppm: 0.88 (t, J = 7.3 Hz, 3H), 1.41-1.53 (m, 2H), 1.62-1.72 (m, 2H), 2.17 (s, 3H), 2.22 (s,
3H), 2.39 (t, J = 7.5 Hz, 2H), 2.45 (t, J = 7.5 Hz, 2H), 2.53 (t, J = 7.4 Hz, 2H), 2.59 (t, J = 4.6 Hz,
4H), 2.67 (s, 4H), 3.15 (t, J = 4.5 Hz, 4H), 3.47 (s, 2H), 6.67-6.74 (m, 3H), 6.83 (d, J = 7.7 Hz,
1H), 7.00 (d, J = 8.2 Hz, 1H), 7.12 (t, J = 7.7 Hz, 1H), 9.15 (s, 1H); 13C-NMR (75 MHz, CDCl3), δ:
11.9, 18.7, 20.1, 20.3, 24.6, 30.9, 35.1, 49.7, 52.1, 53.3, 54.3, 56.1, 56.6, 107.4, 113.7, 118.0,
122.7, 124.0, 127.9, 130.1, 137.0, 137.2, 142.5, 149.6, 177.6; IR(KBr, cm-1): 3195, 3021,
2954, 2872, 1695, 1614, 1572, 1505, 1455, 1379, 1149, 1085, 880, 803, 719, 651; MS: 449.3
[M+H]+; Anal. calcd. for C28H40N4O (%): C 74.96, H 8.99, N 12.49; found: C 74.87, H 8.95, N
12.50.
5.2. Binding assays (Ki values)
All the target compounds were subjected to competitive binding assays for the human
dopamine receptor 3 and receptor 2, using membrane protein obtained from HEK-293 cells
stably transfected respective receptor, and [3H]-spiperone was used as standard
radiolabeled ligand. Duplicated tubes were incubated at 30 °C for 50 min with increasing
concentrations (1 nM-100 μM) of respective compound and with 0.7 nM [3H] spiperone in a
final volume of 200 μL binding buffer containing 50 mM Tris, 4 mМ MgCl2 and pH value of
7.4. Non-specific binding was determined by parallel incubations with 10 μM spiperone for
D2 and D3 receptors respectively. Binding was terminated by the condition of ice bath and
filtration over a glass-fiber filter (Schleicher and Schuell No.32). Filters were washed with
cold buffer (50 mM Tris-HCl, PH 7.5) (3 mL×3)and the radioactivity were measured using a
Packard Cobra gamma counter. Estimates of the equilibrium dissociation constant and
maximum number of binding sites were obtained using non-linear regression analysis[37].
Data from competitive inhibition experiments were modeled using non-linear regression
analysis to determine the concentration of inhibitor that inhibits 50% of the specific binding
of the radioligand. Competition curves were modeled for a single site, and the IC 50 values
will be converted to equilibrium dissociation constants (Ki values) (GraphPad, San Diego, CA,
USA).
Acknowledgment
This work is supported by Natural Science Foundation of Jiangsu Province
(BK20161438 ).
This article is protected by copyright. All rights reserved.

Fig 1.
Chemical structure of ropinirole.
A design for hybrid analogues.
1
2
Fig. 2.
Scheme 1.
Synthetic route for the preparation of the compound 10. Reagents and
conditions: (a) ZnCl2, PhCOCl, CH2Cl2, reflux, 1.5 h, 99%; (b) DMSO,
NaHCO3, 110-120 °C, 1.5 h, 67%; (c) MeNO2, NH4OAc, AcOH, reflux, 8-10
3
4
.
h, 98%; (d) FeCl3, AcCl, CH2Cl2, -5-0 °C, 2 h, 59%; (e) N2H4 H2O, MeOH,
10%Pd/C, reflux, 1 h, NaOH, H2O, reflux, 1 h, 71%; (f) TsCl, Py, CH2Cl2,
5-10 °C, 2 h, 86%; (g) n-PrNH2, EtOH, reflux, 1.5 h, 60%.
Scheme 2.
Synthetic route for the preparation of the compounds 1a-1h and 2a-2h.
Reagents and conditions: (a) SOCl2, CHCl3, rt, 3 h, reflux, 0.5 h, 89%; (b)
substituted phenylamine, n-BuOH, K2CO3, reflux, 48 h, 56-72%; (c) NaOH,
rt. 0.5 h, 92-96%; (d) 1-Bromo-2-chloroethane or
1-Bromo-3-chloropropane, K2CO3, acetone, 35 °C, 3 h, reflux, 10 h,
56-74%; (e) 10, K2CO3, KI, CH3CN, 45 °C, 8 h, 59-72%.
Table 1
Binding affinities of target compounds for D2R and D3R (Ki values )
5
6
Supporting Information
I have stated that my co-authors and I have no conflict of interest.
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Table 1
Binding affinities of target compounds for D2R and D3R (Ki values )
Ki ± SEM (nM)
Compd n
R
D3R
D2R
D2R/D3R
8.8
4.3
8.7
13
1a
1b
1c
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3-Me
49.3±3.1
433±28
107±4.1
118±2.6
2108±360
82.3±12
69.3±0.79
397±51
98.3±2.6
195±3.1
202±14
258±9.6
169±5.8
209±11
367±13
344±16
207±15
69±4.81
2,3-di-Me 24.7±0.43
3-OMe
2-Et
13.5±0.76
168±13
1d
1e
1f
4-Cl
18.7±0.62
22.6±0.55
12.8±0.61
4.4
3.1
31
4-OCF3
H
1g
1h
2a
2b
2c
3,4-di-Me 15.7±0.72
4-Me 2.13±0.37
2,6-di-Me 48.5±3.6
3.61±0.40
2,3-di-Me 12.7±1.4
6.3
92
4.2
71
H
2d
2e
2f
13
2-Me
7.28±0.36
9.04±0.25
7.71±0.38
29
4-OCF3
3-OMe
41
2g
45
2h
BP 897
3,4-di-Me 1.05±0.23
1.27±0.25
197
54
This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.