Design, synthesis and antimycobacterial evaluation of 1-(4-(2-substitutedthiazol-4-yl)phenethyl)-4-(3-(4-substitutedpiperazin-1-yl) alkyl)piperazine hybrid analogues

Article abstract of DOI:10.1016/j.ejmech.2014.07.067

A series of twenty six new 1-(4-(2-substitutedthiazol-4-yl)phenethyl)-4-(3-(4-substitutedpiperazin-1-yl)alkyl)piperazine analogues were synthesized by seven steps and evaluated for their anti-tubercular activity against Mycobacterium tuberculosis H37Rv strain. Among the tested compounds, 7j, 7p, and 7r exhibited moderate activity (MIC = 6.25 mg/mL) and compounds 7a, 7f, 7g, 7n and 7v exhibited good activity (MIC = 3.125 mg/mL), while 7h displayed excellent activity (MIC = 1.56 μg/mL) by inhibiting 99% growth of M. tuberculosis H₃₇Rv strain. In addition, all the active compounds were subjected to cytotoxic studies against mouse macrophage (RAW264.7) cell lines and the selectivity index values for most of the compounds is >10 indicating suitability of compounds in an endeavour to attain lead molecule for further drug development.

Full text of DOI:10.1016/j.ejmech.2014.07.067

European Journal of Medicinal Chemistry 84 (2014) 605e613
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and antimycobacterial evaluation of 1-(4-(2-
substitutedthiazol-4-yl)phenethyl)-4-(3-(4-substitutedpiperazin-1-yl)
alkyl)piperazine hybrid analogues
Hunsur Nagendra Nagesh a, Amaroju Suresh a, Sirigina Devesh Sathya Sri Sairam a,
,
*
Dharmarajan Sriram b, Perumal Yogeeswari b, Kondapalli Venkata Gowri Chandra Sekhar a
a Department of Chemistry, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, R.R. District, 500078, Telangana, India
b Department of Pharmacy, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, R.R. District, 500078, Telangana, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of twenty six new 1-(4-(2-substitutedthiazol-4-yl)phenethyl)-4-(3-(4-substitutedpiperazin-1-
yl)alkyl)piperazine analogues were synthesized by seven steps and evaluated for their anti-tubercular
activity against Mycobacterium tuberculosis H37Rv strain. Among the tested compounds, 7j, 7p, and 7r
Received 23 May 2014
Received in revised form
3 July 2014
Accepted 20 July 2014
Available online 21 July 2014
exhibited moderate activity (MIC ¼ 6.25
m
g/mL) and compounds 7a, 7f, 7g, 7n and 7v exhibited good
g/mL) by inhibiting 99%
activity (MIC ¼ 3.125
m
g/mL), while 7h displayed excellent activity (MIC ¼ 1.56
m
growth of M. tuberculosis H37Rv strain. In addition, all the active compounds were subjected to cytotoxic
studies against mouse macrophage (RAW264.7) cell lines and the selectivity index values for most of the
compounds is >10 indicating suitability of compounds in an endeavour to attain lead molecule for
further drug development.
Keywords:
Thiazole
Piperazine
Alkyl linker
© 2014 Elsevier Masson SAS. All rights reserved.
Antimycobacterial activity
1. Introduction
that are less effective, more toxic and more expensive [2]. Efforts
have been steered to manipulate the biological processes of exist-
Tuberculosis (TB) is second only to HIV/AIDS as the greatest
killer worldwide due to a single infectious agent. In 2012, 8.6
million people fell ill with TB and 1.3 million died from TB. Over 95%
of TB deaths occur in low and middle income countries, and it is
among the top three causes of death for women aged 15 to 44.
People falling ill with TB each year is declining, although very
slowly. An estimated 22 million lives saved through use of Directly
Observed Therapy Shortcourse and the Stop TB strategy recom-
mended by World Health Organization [1]. Detection of Multi-Drug
resistant TB (MDR-TB) patients is increasing every year as a result of
scanty treatment and once TB organisms acquire resistance they
can spread from person to person in the same way as drug-sensitive
TB. The biggest increases were in India, South Africa and Ukraine.
Also, emergence of extensively drug-resistant TB (XDR-TB) and
Rifampicin-resistant TB has still deteriorated the TB treatment by
not responding to the standard six month treatment with first-line
anti-TB drugs and can take two years or more to treat with drugs
ing drugs for effective development of new chemical entities
against TB as a rational approach.
Ascribable to complexity and toxicity of the current TB drug
regimens and emergence of various forms of drug resistant TB
warranted the scientific community to focus on exploring novel
chemotherapeutical agents. As TB is an inevitable disease among
HIV patients, it is identified that current TB drugs (Rifabutin,
Rifampicin and Rifapentine) interact with the antiretroviral drugs
[3] taken by HIV positive people; hence it is essential to scrutinize
cost effective, less toxic chemical entities preferably with new
biochemical pathways to shorten treatment time, and to interrupt
drugedrug interaction.
2-Aminothiazoles are well acknowledged potential therapeutic
agents viz. antiviral, NPY5 antagonists, PGE2 inhibitors, anticancer,
opiod receptor agonists, antimycobacterial, anti-inflammatory,
antiprion etc., [4e11]. The wide applicability of thiazole frame-
work in drug discovery is attributed to the use of inexpensive
starting materials and adoption of simple synthetic strategy to
wangle diverse molecules. In particular, nitazoxanide (NTZ) and its
active metabolite tizoxanide (TIZ) are known to inhibit replicative
and non-replicative Mycobacterium tuberculosis (MTB) [12]. Some
of the drugs based on aminothiazoles moiety are depicted in Fig. 1.
* Corresponding author.
E-mail
addresses:
kvgc@hyderabad.bits-pilani.ac.in,
kvgcs@yahoo.com
(K.V.G. Chandra Sekhar).
http://dx.doi.org/10.1016/j.ejmech.2014.07.067
0223-5234/© 2014 Elsevier Masson SAS. All rights reserved.

606
H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
In addition, Tuberculosis Antimicrobial Acquisition and Coor-
in Fig. 3. We adopted reported procedure with slight modification to
prepare 4-(4-(2-chloroethyl)phenyl)-2-substitutedthiazole (3) [29],
then 3 was coupled with anhydrous piperazine in N,N-dime-
dinating Facility (TAACF) and the National Institutes of Health,
Molecular Libraries Screening Centres Network disclosed encour-
aging results from an MTB whole-cell high-throughput assay and
identified aminothiazoles as an important core which is depicted in
Fig. 2 [9,13e15]. Few research groups synthesized various 2-(2-
hydrazinyl)thiazole derivatives and reported good activity against
MTB strain H37Rv [16e18]. Similarly, Makam et al., reported 2-(2-
hydrazinyl)thiazole derivatives which are structurally similar to
thiolactomycin using rational hybrid approach with good anti-TB
activity [19]. Sridhar et al., synthesized Nl-hydroxy-N-(4H,5H-
naphtho[1,2-d]thiazol-2-yl)methanimidamide analogues which
inhibit MTB methionine aminopeptidases [20]. Ranjith et al., syn-
thesized (2-aminothiazol-4-yl)methyl 3-(2-cyanoethyl)benzoate
and found to exhibit good anti-TB activity than isoniazid against
MTB H37Rv, Mycobacterium Smegmatis (ATCC 19420), Mycobacte-
rium Fortuitum (ATCC 19542) and MDR-TB strains [21]. Meissner
et al., synthesized 3-bromo-N-(4-(pyridin-2-yl)thiazol-2-yl)benza-
thylformamide (DMF) at 100 ꢀC for
3 h to give 1-(4-(2-
substitutedthiazol-4-yl)phenethyl)piperazine (4). Compound 4-(4-
(4-(2-substitutedthiazol-4-yl)phenethyl)piperazin-1-yl)alkan-1-ol
(5) was obtained bycoupling 4 with bromoalkanols in the presence of
triethylamine (TEA) and DMF at 100 ꢀC for 3 h; further heating 5 at
120 ꢀC with 40% hydrobromic acid for 2 h fetched 1-(4-(2-
substitutedthiazol-4-yl)phenethyl)-4-(n-bromoalkyl)piperazine (6).
Subsequently various substituted piperazines were coupled with 6 at
120 ꢀC for 3 h using TEA and DMF to achieve title compounds (7aez).
All the title compounds displayed multiplet in the range
2.75e2.95 ppm and 3.45e3.65 ppm corresponding to piperazine
(eCH2e) protons. Characteristic aromatic proton (C-5) of thiazole
ring resonated in the range 6.50e6.75 ppm. Both analytical and
spectral data (1H NMR, 13C NMR, IR and HRMS) of all the synthesized
compounds were confirmed and employed further for their anti-
mycobacterial evaluation.
mide derivatives which inhibit MTB H37Rv strain at 0.008 mg/mL [9].
Very recently, Pieroni et al., synthesized N-substituted-2-
aminothiazole derivatives and clearly briefed the structure activ-
ity relationship emphasizing on the mandatory of aminomethyl
group at second position of thiazole [22].
3. Results and discussion
3.1. Antimycobacterial activity
MTB cells wrap a protective sheath on the cell wall composed of
complex carbohydrates, proteins and glycolipids [23] making most
of the drugs very complicated to penetrate through this thick, non-
permeable, hydrophobic barrier which defies current treatment.
This being one of the greatest challenges put forward to the sci-
entists while designing a drug. Piperazine linkers have made vast
impact on drug discovery process as they have ability to increase
the lipophilicity of the molecule to a greater extent. Bogatcheva
et al., synthesized various diamine linked moieties and reported
good in vitro and in vivo anti-tubercular activity against MTB H37Rv
strain [24]. Huang et al., synthesized 2-methyl benzothiazoles
All the synthesized compounds were tested for their ability to
inhibit the growth of MTB H37RV strain by Microplate Alamar Blue
Assay (MABA). Isoniazid and Rifampicin were used as the positive
drug standard. The in vitro antimycobacterial test results of title
compounds are tabulated in Table 1 as minimum inhibitory con-
centration (MIC) and the activity ranges between 1.56 and
>6.25
m
g/mL. Compounds with MIC ꢁ6.25
mg/mL were further
subjected to cytotoxicity studies. Amongst the series, compounds
7j, 7p and 7r inhibit 99% growth of MTB H37Rv strain at a con-
centration 6.25
m
g/mL whereas compounds 7a, 7f, 7g, 7n and 7v
g/
which inhibited the growth of MTB H37Rv strain at 1.4 mM [25].
inhibit 99% growth of MTB H37Rv strain at a concentration 3.125
m
With this collective information and encouraged by our recent
anti-TB results emphasizing on molecular hybridization approach
[26e28] we drew a synthetic stratagem (Fig. 2) to fit all these
imperative pharmacophoric groups into one distinct scaffold and
synthesized 1-(4-(2-substitutedthiazol-4-yl)phenethyl)-4-(3-(4-
substitutedpiperazin-1-yl)alkyl)piperazine analogues.
mL. Compound 7h emerged as the most promising candidate by
inhibiting 99% growth of MTB H37Rv strain at a concentration
1.56 mg/mL.
Among the synthesized compounds electron releasing groups
like phenyl and benzhydryl piperazine with propyl and butyl linker
respectively, bearing N-methylthiazol-2-amine backbone were
found to be inactive (7c and 7i, MIC ¼ 50
mg/mL). Next, keeping
propyl linker intact we synthesized 2-methylthiazole moiety
2. Chemistry
bearing phenyl piperazine (7e) which exhibited 2 fold increase in
We synthesized 1-(4-(2-substitutedthiazol-4-yl)phenethyl)-4-(3-
(4-substitutedpiperazin-1-yl)alkyl)piperazine analogues as sketched
the activity (MIC ¼ 25
mg/mL). Subsequently an alkyl chain was
increased to fetch compound 7b which exhibited similar activity
Fig. 1. Drugs currently in use based on 2-aminothiazole skeleton.

H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
607
Fig. 2. Scaffold from TAACF high-throughput screening campaign and design strategy to achieve title compounds.
(MIC ¼ 25
phenyl group and N-methylthiazol-2-amine backbone leading to
g/mL).
Switching from aminothiazoles to 2-methylthiazole with
benzhydryl-piperazine and propyl linker exhibited significant ac-
m
g/mL). With this increased activity, butyl link tailored to
production and phagocytosis. As MTB generally reside and
multiply inside the macrophages, so to carry out the cytotoxicity
against RAW 264.7 cells is imperative to scrutinize the selec-
tivity of compounds against MTB rather than host macrophage.
Hence the active compounds 7a, 7f, 7g, 7h, 7j, 7n, 7p, 7r and 7v
were subjected to in vitro cytotoxicity studies by 3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)
assay. The IC50 and selectivity index (SI) values are tabulated in
Table 2. The SI is defined as the ratio of the IC50 to the MIC (MTB
7d, amplified the activity further by 2 fold (MIC ¼ 12.5
m
tivity (7j, MIC ¼ 6.25
mg/mL). Notably, compounds with phenyl and
benzhydryl piperazine tagged 2-aminothiazoles with propyl and
butyl linker respectively exhibited good activity (7a, 7f and 7g,
MIC ¼ 3.125
mg/mL). Eventually, compound 7h comprising N-
methylthiazol-2-amine attached to benzhydryl piperazine through
propyl link emerged as a potential candidate by inhibiting the MTB
H37Rv strain). SI value >10 indicates that the compound may be
considered for further studies. Tested active compounds
exhibited percentage growth inhibitions of RAW 264.7 cells in
H37Rv strain at 1.56 mg/mL. In general, compounds with electron
withdrawing groups were found to be inactive except compound
7n bearing N-methylthiazol-2-amine attached to 2-chlorophenyl
piperazine through butyl link exhibited good activity
the range of 31.76e46.43% at a concentration 50 mg/mL. Among
the tested compounds, 7j, 7p and 7r exhibited toxicity (SI ꢂ 7)
and compounds 7a, 7f, 7g, 7n and 7v exhibited non-toxic
(SI ꢂ 15). Nevertheless, most active compound 7h (SI ꢂ 30)
found to be safe for further studies and emerged as more potent
molecule of the series. These encouraging results imply the
suitability of compounds in an endeavour to attain lead mole-
cule for further drug development.
(MIC ¼ 3.125
mg/mL). On the other hand, employing 2-pyridyl
piperazine led to compound 7v consisting 2-aminothiazole back-
bone through propyl linker which exhibited good activity
(MIC ¼ 3.125
mg/mL). Structureeactivity relationship evidently in-
dicates the necessity of 2-aminomethyl group at 2nd position of
thiazole which might involve in hydrogen bonding to a greater
extent to exhibit good activity.
4. Conclusion
3.2. Cytotoxicity assay
In conclusion, our preliminary anti-tubercular screening results
earmarked us to fine-tune the architecture of 2-aminothiazole
framework to fetch desired pharmacophoric features that might
be explored to evaluate various drug resistant forms of TB. We
RAW 264.7 cell lines derived from BALB/c mice maintain
many of the properties of macrophages including nitric oxide

608
H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
Fig. 3. Synthetic strategy to achieve title compounds.
disclose that integrating N-methyl-4-(4-(2-(piperazin-1-yl)ethyl)
phenyl)thiazol-2-amine to benzhydryl piperazine through propyl
linker emerged as a prospective candidate by inhibiting the MTB
5. Experimental section
5.1. Materials and methods
H37Rv strain at concentration 1.56 mg/mL (7h).
Chemicals and solvents were procured from commercial sources
and are analytically pure. Thin-layer chromatography (TLC) was
carried out on aluminium-supported silica gel plates (Merck 60
F254) with visualization of components by UV light (254 nm).
Column chromatography was carried out on silica gel (Merck
230e400 mesh). 1H NMR spectra and 13C NMR spectra were
recorded at 300 MHz using a Bruker AV 300 spectrometer or
400 MHz using a Bruker AV 400 spectrometer (Bruker CO.,
Switzerland) in CDCl3 or DMSO-D6 solution with tetramethylsilane
Table 1
Antimycobacterial activities of compound 7aez against MTB H37Rv strain.
Compound no.
R1
n
R
MIC (
against MTB
37Rv
mg/mL)
H
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
7r
7s
7t
7u
7v
7w
7x
Ph
Ph
Ph
Ph
3
4
3
4
3
3
4
3
4
3
3
4
3
4
3
3
4
5
3
4
3
3
4
3
4
3
NH2
NH2
NHCH3
NHCH3
CH3
NH2
NH2
NHCH3
NHCH3
CH3
NH2
NH2
NHCH3
NHCH3
CH3
NH2
NH2
NH2
NHCH3
NHCH3
CH3
NH2
NH2
NHCH3
NHCH3
CH3
3.125
25
50
12.5
25
3.125
3.125
1.56
50
as the internal standard, and chemical shift values (d) are given in
ppm. Microwave reactions were performed in closed vessel using
Biotage Initiator microwave synthesizer (Uppsala, Sweden). IR
spectra were recorded on a FT-IR spectrometer (Schimadzu) and
peaks are reported in cmꢃ1. Melting points were determined on an
electro thermal melting point apparatus (Stuart-SMP30) in open
capillary tubes and are uncorrected. High-resolution mass spectra
Ph
(Ph)2CH
(Ph)2CH
(Ph)2CH
(Ph)2CH
(Ph)2CH
2-ClPh
2-ClPh
2-ClPh
2-ClPh
2-ClPh
4-NO2Ph
4-NO2Ph
4-NO2Ph
4-NO2Ph
4-NO2Ph
4-NO2Ph
2-Py
6.25
50
50
12.5
3.125
50
6.25
12.5
6.25
12.5
50
Table 2
IC50 (mg/mL) and selectivity index (SI) values of active compounds.
Compound
MIC (
in MTB H37Rv
m
g/mL)
% Cell inhibition
IC50
approximation
(
m
g/mL)
SI value
IC50/MIC
at 50
m
g/mL
7a
7f
7g
7h
7j
7n
7p
7r
7v
3.125
3.125
3.125
1.56
6.25
3.125
6.25
35.62
38.42
46.43
31.76
42.8
40.4
36.46
44.6
>50
>50
>50
>50
>50
>50
>50
>50
>50
>15
>15
>15
>30
>7
>15
>7
>7
50
3.125
12.5
12.5
25
2-Py
2-Py
2-Py
2-Py
7y
7z
50
Isoniazid
Rifampicin
0.05
0.1
6.25
3.125
38.1
>15

H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
609
(HRMS) were recorded on QSTAR XL Hybrid MS/MS mass spec-
trometer. Elemental analysis was carried out on Elementar (vario
MICRO cube, Hanau, Germany).
2761 (aliphatic CeH stretch); 1638 (CeS stretch); 1612, 1595 (aro-
matic C]C stretch); 1272 (aliphatic CeN stretch); 838 (para
disubstituted benzene); HRMS: (ESI m/z) for C28H39N6S calculated:
491.2957, found: 491.2983 (MþH)þ; Anal. Calculated for C28H38N6S:
C 68.53, H 7.81, N 17.13, S 6.53; found: C 68.46, H 7.63, N 17.22, S
6.47.
5.2. Preparation of 4
To a suspension of 3 (1 eq) in DMF was added KI (0.2 eq), TEA
(1 eq) and stirred for 15 min at room temperature (rt). To the
resultant mixture anhydrous piperazine (3 eq) was added and
heated at 100 ꢀC for 3 h. Completion of the reaction was monitored
by TLC using 20% MeOH in DCM as mobile phase. After the reaction
was complete, DMF was evaporated under vacuo and added 5 mL of
water. Compound was extracted using EtOAc (3 ꢄ 5 mL). Combined
organic layers were washed with saturated brine solution, dried
over anhydrous sodium sulphate and evaporated in vacuo. The
crude residue was purified by column chromatography (MeOH/
DCM) to get compounds 4.
5.5.2. 4-(4-(2-(4-(4-(4-phenylpiperazin-1-yl)butyl)piperazin-1-yl)
ethyl)phenyl)thiazol-2-amine (7b)
Beige solid (86%); m.p. 192e194 ꢀC; 1H NMR (400 MHz, CDCl3)
d
7.64 (d, J ¼ 7.18 Hz, 2H), 7.29 (d, J ¼ 7.3 Hz, 2H), 7.19 (m, 2H), 6.86
(m, 3H), 6.64 (s, 1H), 5.49 (b, 2H), 3.53 (m, 4H), 3.27 (m, 2H), 2.76
(m, 4H), 2.58 (m, 8H), 2.36 (m, 6H), 1.96 (m, 4H). 13C NMR
(100.61 MHz, CDCl3) d 168.89, 151.83, 150.04, 142.92, 133.09, 128.15,
127.26, 126.28, 124.82, 101.69, 100.07, 59.37, 58.39, 56.81, 55.13,
51.61, 30.72, 25.56, 21.63, 12.06, 11.42. IR (KBr, nmax) cmꢃ1: 3440,
3410 (NH stretch); 3065, 3027 (aromatic CeH stretch); 2842, 2753
(aliphatic CeH stretch); 1647 (CeS stretch); 1603, 1590 (aromatic
C]C stretch); 1261 (aliphatic CeN stretch); 823 (para disubstituted
benzene); HRMS: (ESI m/z) for C29H41N6S calculated: 505.3113,
found: 505.3133 (MþH)þ; Anal. Calculated for C29H40N6S: C 69.01,
H 7.99, N 16.65, S 6.35; found: C 69.10, H 7.78, N 16.88, S 6.42.
5.3. Preparation of 5
To a solution of 4 (1 eq) in DMF was added bromoalkanol
(1.2 eq), TEA (1.5 eq) and heated at 100 ꢀC for 3 h. Completion of the
reaction was monitored by TLC using 20% MeOH in DCM as mobile
phase. After the reaction was complete, DMF was evaporated under
vacuo and added 5 mL of water. Compound was extracted using
EtOAc (3 ꢄ 5 mL). Combined organic layers were washed with
saturated brine solution, dried over anhydrous sodium sulphate
and evaporated in vacuo. The crude residue was purified by column
chromatography (MeOH/DCM) to get compounds 5.
5.5.3. N-methyl-4-(4-(2-(4-(3-(4-phenylpiperazin-1-yl)propyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7c)
Beige solid (79%); m.p. 178e180 ꢀC; 1H NMR (400 MHz, CDCl3)
d
7.61 (d, J ¼ 7.18 Hz, 2H), 7.35 (d, J ¼ 7.3 Hz, 2H), 7.27 (m, 2H), 6.78
(m, 3H), 6.59 (s, 1H), 4.96 (b, 1H), 3.61 (m, 4H), 2.92 (m, 4H), 2.81
(m, 8H), 2.47 (s, 3H), 2.38 (m, 8H), 1.79 (m, 2H). 13C NMR
(100.61 MHz, CDCl3) d 167.83, 151.62, 150.02, 144.68, 134.62, 129.26,
5.4. Preparation of 6
128.77, 127.62, 124.33, 102.15, 100.99, 61.83, 59.09, 56.44, 55.22,
51.88, 34.29, 32.14, 24.90, 20.48,11.94. IR (KBr, nmax) cmꢃ1: 3418 (NH
stretch); 3059, 3033 (aromatic CeH stretch); 2837, 2747 (aliphatic
CeH stretch); 1629 (CeS stretch); 1611, 1583 (aromatic C]C
stretch); 1263 (aliphatic CeN stretch); 827 (para disubstituted
benzene); HRMS: (ESI m/z) for C29H41N6S calculated: 505.3113,
found: 505.3129 (MþH)þ; Anal. Calculated for C29H40N6S: C 69.01,
H 7.99 N 16.65, S 6.35; found: C 69.10, H 7.81, N 16.77, S 6.44.
To a suspension of 5 (1 eq) in 40% aq. HBr (0.6 eq) was added
TBAB (0.3 eq) and heated at 120 ꢀC for 2 h. Completion of the re-
action was monitored by TLC using 5% MeOH in DCM as mobile
phase. After the reaction was complete, added 5 mL of water.
Compound was extracted using EtOAc (3 ꢄ 5 mL). Combined
organic layers were washed with saturated brine solution, dried
over anhydrous sodium sulphate and evaporated in vacuo. The
crude residue was purified by column chromatography (MeOH/
DCM) to get compounds 6.
5.5.4. N-methyl-4-(4-(2-(4-(4-(4-phenylpiperazin-1-yl)butyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7d)
Pale yellow solid (81%); m.p. 191e193 ꢀC; 1H NMR (400 MHz,
5.5. Synthesis of title compounds (7aez)
CDCl3)
6.83 (m, 3H), 6.61 (s, 1H), 4.82 (b, 1H), 3.58 (m, 4H), 2.87 (m, 4H),
2.72 (m, 8H), 2.51 (s, 3H), 2.37 (m, 8H), 2.11 (m, 2H),1.92 (m, 2H). 13
NMR (100.61 MHz, CDCl3) 168.12, 152.41, 151.83, 145.22, 135.21,
128.16, 127.72, 126.15, 124.11, 101.83, 100.54, 61.13, 59.85, 56.05,
55.24, 52.47, 34.25, 32.63, 25.35, 21.37, 12.88, 11.26. IR (KBr, nmax
d
7.71 (d, J ¼ 7.18 Hz, 2H), 7.42 (d, J ¼ 7.3 Hz, 2H), 7.28 (m, 2H),
To a solution of 6 (1 eq) in DMF and TEA (2 eq) was added
substituted piperazine (1.2 eq) and heated at 120 ꢀC for 3 h.
Completion of the reaction was monitored by TLC using 20% MeOH
in DCM as mobile phase. After the reaction was complete, DMF was
evaporated under vacuo and added 5 mL of water. Compound was
extracted using EtOAc (3 ꢄ 5 mL). Combined organic layers were
washed with saturated brine solution, dried over anhydrous so-
dium sulphate and evaporated in vacuo. The crude residue was
purified by column chromatography (MeOH/DCM) to get com-
pounds 7aez.
C
d
)
cmꢃ1: 3421 (NH stretch); 3072, 3011 (aromatic CeH stretch); 2834,
2768 (aliphatic CeH stretch); 1671 (CeS stretch); 1623, 1597 (aro-
matic C]C stretch); 1268 (aliphatic CeN stretch); 836 (para
disubstituted benzene); HRMS: (ESI m/z) for C30H43N6S calculated:
519.3270, found: 519.3251 (MþH)þ; Anal. Calculated for C30H42N6S:
C 69.46, H 8.16, N 16.20, S 6.18; found: C 69.23, H 8.22, N 16.11, S
6.09.
5.5.1. 4-(4-(2-(4-(3-(4-phenylpiperazin-1-yl)propyl)piperazin-1-
yl)ethyl)phenyl)thiazol-2-amine (7a)
5.5.5. 1-(4-(2-methylthiazol-4-yl)phenethyl)-4-(3-(4-
phenylpiperazin-1-yl)propyl)piperazine (7e)
Yield ¼ 83%; Off white solid, m.p. 184e186 ꢀC; 1H NMR
(400 MHz, CDCl3)
d
7.69 (d, J ¼ 7.18 Hz, 2H), 7.33 (d, J ¼ 7.3 Hz, 2H),
Off white solid (75%); m.p. 201e203 ꢀC; 1H NMR (400 MHz,
7.21 (m, 2H), 6.89 (m, 3H), 6.68 (s, 1H), 5.52 (b, 2H), 3.58 (m, 4H),
3.37 (m, 2H), 2.86 (m, 4H), 2.63 (m, 8H), 2.42 (m, 6H), 2.17 (m, 2H).
CDCl3)
d
7.69 (d, J ¼ 7.18 Hz, 2H), 7.45 (d, J ¼ 7.3 Hz, 2H), 7.32 (m, 2H),
6.73 (m, 3H), 6.58 (s, 1H), 3.58 (m, 6H), 2.87 (t, J ¼ 4.7 Hz, 2H), 2.72
(m, 6H), 2.51 (t, J ¼ 3.8 Hz, 2H), 2.41 (s, 3H), 2.34 (m, 8H), 1.86 (m,
13C NMR (100.61 MHz, CDCl3)
d
169.61, 152.86, 150.23, 143.65,
133.87, 128.91, 128.12, 127.53, 124.05, 102.11, 100.67, 60.86, 58.92,
56.11, 55.81, 51.34, 32.12, 24.61, 20.19, 12.87. IR (KBr, nmax) cmꢃ1
3436, 3407 (NH stretch); 3071, 3033 (aromatic CeH stretch); 2849,
2H). 13C NMR (100.61 MHz, CDCl3)
d 167.51, 153.83, 151.53, 146.66,
:
134.73, 128.16, 127.14, 126.62, 124.94, 102.35, 100.26, 60.83, 58.45,
56.11, 55.35, 52.17, 35.22, 31.62, 26.62, 21.88, 11.83. IR (KBr, nmax
)

610
H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
cmꢃ1: 3058, 3019 (aromatic CeH stretch); 2862, 2782 (aliphatic
CeH stretch); 1667 (CeS stretch); 1629 (thiazole CH3 CeC stretch),
1612, 1582 (aromatic C]C stretch); 1277 (aliphatic CeN stretch);
848 (para disubstituted benzene); HRMS: (ESI m/z) for C29H40N5S
calculated: 490.3004, found: 490.3023 (MþH)þ; Anal. Calculated
for C29H39N5S: C 71.12, H 8.03, N 14.30, S 6.55; found: C 71.09, H
8.10, N 14.23, S 6.49.
1H), 4.13 (s, 1H), 3.47 (m, 2H), 2.99 (m, 4H), 2.63 (m, 8H), 2.49 (s,
3H), 2.39 (m, 8H), 2.13 (m, 2H), 1.75 (m, 2H). 13C NMR (101 MHz,
CDCl3)
125.01, 124.31, 102.72, 60.62, 58.15, 56.26, 55.15, 53.63, 53.12, 52.67,
50.83, 32.21, 29.12, 25.53, 24.11, 20.28, 12.12, 11.68. IR (KBr, nmax
d 167.22, 151.61, 141.42, 138.26, 132.77, 128.15, 127.72, 126.15,
)
cmꢃ1: 3431 (NH stretch); 3072, 3043 (aromatic CeH stretch); 2878,
2716 (aliphatic CeH stretch); 1641 (CeS stretch); 1621, 1582 (aro-
matic C]C stretch); 1271 (aliphatic CeN stretch); 846 (para
disubstituted benzene); HRMS: (ESI m/z) for C37H49N6S calculated:
609.3739, found: 609.3721 (MþH)þ; Anal. Calculated for
5.5.6. 4-(4-(2-(4-(3-(4-benzhydrylpiperazin-1-yl)propyl)piperazin-
1-yl)ethyl)phenyl)thiazol-2-amine (7f)
White solid (72%); m.p. 168e170 ꢀC; 1H NMR (400 MHz, CDCl3)
C37H48N6S: C 72.99, H 7.95, N 13.80, S 5.27; found: C 72.82, H 7.91, N
d
7.65 (t, J ¼ 11.9 Hz, 2H), 7.41 (d, J ¼ 7.4 Hz, 4H), 7.26 (t, J ¼ 7.1 Hz,
13.87, S 5.22.
4H), 7.17 (dd, J ¼ 12.2, 7.4 Hz, 4H), 6.66 (s, 1H), 5.34 (b, 2H), 4.21 (s,
1H), 3.42 (m, 4H), 3.29 (m, 2H), 2.89 (m, 4H), 2.58 (m, 8H), 2.37 (m,
5.5.10. 1-(4-(2-methylthiazol-4-yl)phenethyl)-4-(3-(4-
benzhydrylpiperazin-1-yl)propyl)piperazine (7j)
6H), 1.49 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 167.54, 151.09,
142.70, 139.75, 132.70, 128.91, 128.49, 127.90, 126.94, 126.05, 102.11,
60.21, 59.03, 56.55, 56.52, 53.40, 53.06, 52.95, 51.68, 33.21, 24.15,
23.96, 19.76, 13.72. IR (KBr, nmax) cmꢃ1: 3482, 3426 (NH stretch);
3088, 3061 (aromatic CeH stretch); 2877, 2728 (aliphatic CeH
stretch); 1651 (CeS stretch); 1612, 1587 (aromatic C]C stretch);
1278 (aliphatic CeN stretch); 844 (para disubstituted benzene);
HRMS: (ESI m/z) for C35H45N6S calculated: 581.3426, found:
581.3418 (MþH)þ; Anal. Calculated for C35H44N6S: C 72.37, H 7.64, N
14.47, S 5.52; found: C 72.44, H 7.70, N 14.53, S 5.64.
Brown solid (76%); m.p. 208e210 ꢀC; 1H NMR (400 MHz, CDCl3)
d
7.65 (t, J ¼ 11.9 Hz, 2H), 7.41 (d, J ¼ 7.4 Hz, 4H), 7.26 (t, J ¼ 7.1 Hz,
4H), 7.17 (dd, J ¼ 12.2, 7.4 Hz, 4H), 6.66 (s, 1H), 4.32 (s, 1H), 3.52 (m,
2H), 2.98 (m, 4H), 2.75 (s, 3H), 2.61 (m, 8H), 2.36 (m, 8H), 1.71 (m,
2H). 13C NMR (101 MHz, CDCl3)
d 168.12, 154.86, 143.15, 140.82,
133.34, 129.24, 128.15, 127.26, 126.72, 125.74, 104.89, 61.83, 60.73,
57.83, 57.32, 54.26, 53.54, 52.62, 51.15, 34.63, 25.65 24.72, 21.56,
19.58, 14.22. IR (KBr, nmax) cmꢃ1: 3061, 3022 (aromatic CeH
stretch); 2872, 2779 (aliphatic CeH stretch); 1663 (CeS stretch);
1633 (thiazole-CH3 CeC stretch), 1622, 1587 (aromatic C]C
stretch); 1266 (aliphatic CeN stretch); 853 (para disubstituted
benzene); HRMS: (ESI m/z) for C36H46N5S calculated: 580.3474,
found: 580.3466 (MþH)þ; Anal. Calculated for C36H45N5S: C 74.57,
H 7.82, N 12.08, S 5.53; found: C 74.52, H 7.90, N 12.07, S 5.48.
5.5.7. 4-(4-(2-(4-(4-(4-benzhydrylpiperazin-1-yl)butyl)piperazin-
1-yl)ethyl)phenyl)thiazol-2-amine (7g)
Beige solid (81%); m.p. 175e177 ꢀC; 1H NMR (400 MHz, CDCl3)
7.72 (t, J ¼ 11.4 Hz, 2H), 7.39 (d, J ¼ 7.1 Hz, 4H), 7.29 (t, J ¼ 6.9 Hz,
d
4H), 7.19 (dd, J ¼ 11.9, 7.6 Hz, 4H), 6.68 (s, 1H), 5.33 (b, 2H), 4.18 (s,
1H), 3.48 (m, 4H), 3.36 (m, 2H), 2.92 (m, 4H), 2.51 (m, 8H), 2.46 (m,
5.5.11. 4-(4-(2-(4-(3-(4-(2-chlorophenyl)piperazin-1-yl)propyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7k)
6H), 1.92 (m, 2H), 1.55 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 167.41,
151.01, 141.66, 138.99, 133.45, 127.78, 127.32, 126.67, 126.23, 126.01,
104.43, 62.77, 60.96, 57.49, 56.83, 54.97, 53.76, 51.87, 50.54, 34.39,
25.75, 23.54,18.44,14.56,13.96. IR (KBr, nmax) cmꢃ1: 3440, 3410 (NH
stretch); 3065, 3027 (aromatic CeH stretch); 2842, 2753 (aliphatic
CeH stretch); 1647 (CeS stretch); 1603, 1590 (aromatic C]C
stretch); 1261 (aliphatic CeN stretch); 823 (para disubstituted
benzene); HRMS: (ESI m/z) for C36H47N6S calculated: 595.3583,
found: 595.3577 (MþH)þ; Anal. Calculated for C36H46N6S: C 72.69,
H 7.79, N 14.13, S 5.39; found: C 72.60, H 7.74, N 14.18, S 5.27.
Pale yellow solid (85%); m.p. 152e154 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
7.72 (d, J ¼ 8.1 Hz, 2H), 7.38 (d, J ¼ 7.8 Hz, 1H), 7.31 (dd,
J ¼ 14.4, 3.8 Hz, 3H), 7.18 (d, J ¼ 8.0 Hz, 1H), 7.03 (d, J ¼ 7.7 Hz, 1H),
6.67 (s, 1H), 5.25 (b, 2H), 3.39 (m, 2H), 3.22 (m, 4H), 2.78 (m, 2H),
2.52 (m, 12H), 2.36 (m, 4H), 1.83 (m, 2H). 13C NMR (101 MHz, CDCl3)
d
169.03, 158.61, 149.36,140.71, 133.88, 132.16,129.82, 128.16,127.11,
126.47, 123.71, 121.81, 110.88, 61.39, 59.27, 57.72, 55.87, 53.83, 52.04,
50.82, 31.61, 24.76, 18.72, 16.16, 13.67. IR (KBr, nmax) cmꢃ1: 3451,
3409 (NH stretch); 3078, 3033 (aromatic CeH stretch); 2855, 2759
(aliphatic CeH stretch); 1656 (CeS stretch); 1612, 1595 (aromatic
C]C stretch); 1288 (aliphatic CeN stretch); 846 (para disubstituted
benzene); 745 (ortho disubstituted benzene); 680 (aromatic CeCl
stretch); HRMS: (ESI m/z) for C28H38ClN6S calculated: 525.2567,
found: 525.2558 (MþH)þ; Anal. Calculated for C28H37ClN6S: C
64.04, H 7.10, Cl 6.75, N 16.00, S 6.11; found: C 64.00, H 7.09, Cl 6.67,
N 16.10, S 6.05.
5.5.8. 4-(4-(2-(4-(3-(4-benzhydrylpiperazin-1-yl)propyl)piperazin-
1-yl)ethyl)phenyl)-N-methylthiazol-2-amine (7h)
Pale yellow solid (88%); m.p. 193e195 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
7.68 (t, J ¼ 11.4 Hz, 2H), 7.41 (d, J ¼ 7.1 Hz, 4H), 7.26 (t,
J ¼ 6.9 Hz, 4H), 7.12 (dd, J ¼ 11.9, 7.6 Hz, 4H), 6.65 (s, 1H), 5.23 (b,
1H), 4.19 (s, 1H), 3.45 (m, 4H), 3.36 (m, 2H), 2.88 (m, 4H), 2.79 (s,
3H), 2.71 (m, 3H), 2.62 (m, 8H), 2.38 (m, 7H), 1.62 (m, 2H). 13C NMR
(101 MHz, CDCl3)
d
168.01, 152.67, 141.87, 139.34, 132.12, 128.26,
5.5.12. 4-(4-(2-(4-(4-(4-(2-chlorophenyl)piperazin-1-yl)butyl)
127.23, 126.77, 125.23, 124.22, 101.82, 61.82, 58.62, 56.66, 55.52,
53.85, 53.06, 52.24, 51.23, 32.77, 29.45 25.72, 24.15, 19.24, 12.72. IR
(KBr, nmax) cmꢃ1: 3422 (NH stretch); 3061, 3038 (aromatic CeH
stretch); 2887, 2725 (aliphatic CeH stretch); 1637 (CeS stretch);
1611, 1578 (aromatic C]C stretch); 1268 (aliphatic CeN stretch);
851 (para disubstituted benzene); HRMS: (ESI m/z) for C36H47N6S
calculated: 595.3583, found: 595.3571 (MþH)þ; Anal. Calculated
for C36H46N6S: C 72.69, H 7.79, N 14.13, S 5.39; found: C 72.60, H
7.74, N 14.18, S 5.27.
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7l)
Off white solid (71%); m.p. 148e150 ꢀC;
d
7.71 (d, J ¼ 8.1 Hz, 2H),
7.46 (d, J ¼ 7.8 Hz, 1H), 7.37 (dd, J ¼ 14.4, 3.8 Hz, 3H), 7.22 (d,
J ¼ 8.0 Hz, 1H), 7.17 (d, J ¼ 7.7 Hz, 1H), 6.68 (s, 1H), 5.27 (b, 2H), 3.42
(m, 2H), 3.27 (m, 4H), 2.86 (m, 2H), 2.61 (m, 12H), 2.35 (m, 4H), 1.76
(m, 2H), 1.47 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 169.16, 157.96,
149.13, 141.67, 134.67, 132.84, 129.67, 128.71, 127.82, 126.87, 123.22,
121.64, 110.11, 60.92, 58.61, 57.24, 55.15, 53.72, 52.55, 50.26, 32.82,
25.72, 19.26, 15.17, 12.72, 11.67. IR (KBr, nmax) cmꢃ1: 3466, 3423 (NH
stretch); 3066, 3024 (aromatic CeH stretch); 2867, 2762 (aliphatic
CeH stretch); 1448 (CeS stretch); 1654, 1611 (aromatic C]C
stretch); 1273 (aliphatic CeN stretch); 844 (para disubstituted
benzene); 748 (ortho disubstituted benzene); 679 (aromatic CeCl
stretch); HRMS: (ESI m/z) for C29H40ClN6S calculated: 539.2724,
found: 539.2745 (MþH)þ; Anal. Calculated for C29H39ClN6S: C
5.5.9. 4-(4-(2-(4-(4-(4-benzhydrylpiperazin-1-yl)butyl)piperazin-
1-yl)ethyl)phenyl)-N-methylthiazol-2-amine (7i)
Off white solid (77%); m.p. 211e212 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
7.67 (t, J ¼ 11.8 Hz, 2H), 7.43 (d, J ¼ 7.6 Hz, 4H), 7.33 (t,
J ¼ 7.2 Hz, 4H), 7.26 (dd, J ¼ 11.7, 7.9 Hz, 4H), 6.75 (s, 1H), 5.23 (b,

H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
611
64.60, H 7.29, Cl 6.58, N 15.59, S 5.95; found: C 64.53, H 7.25, Cl 6.67,
N 15.50, S 5.87.
2.78 (m, 2H), 2.66 (m, 6H), 2.51 (m, 6H), 2.45 (m, 4H), 1.53 (m, 2H).
13C NMR (101 MHz, CDCl3)
168.32, 158.63, 155.37, 138.93, 136.38,
d
131.70, 129.37, 127.12, 126.49, 111.44, 110.49, 60.48, 58.70, 57.25,
56.42, 54.74, 52.26, 44.96, 33.06, 25.70, 22.47, 18.58, 10.64. IR (KBr,
nmax) cmꢃ1: 3462, 3417 (NH stretch); 3087, 3029 (aromatic CeH
stretch); 2861, 2753 (aliphatic CeH stretch); 1658 (CeS stretch);
1632, 1609 (aromatic C]C stretch); 1549, 1367 (NO2 stretch); 1277
(aliphatic CeN stretch); 836 (para disubstituted benzene); 809
(para disubstituted benzene); HRMS: (ESI m/z) for C28H38N7O2S
calculated: 536.2808, found: 536.2811 (MþH)þ; Anal. Calculated
for C28H37N7O2S: C 62.78, H 6.96, N 18.30, O 5.97, S 5.99; found: C
62.59, H 6.85, N 18.42, O 5.89, S 5.85.
5.5.13. 4-(4-(2-(4-(3-(4-(2-chlorophenyl)piperazin-1-yl)propyl)
piperazin-1-yl)ethyl)phenyl)-N-methylthiazol-2-amine (7m)
Brown solid (78%); m.p. 141e143 ꢀC; 1H NMR (400 MHz, CDCl3)
d
7.68 (d, J ¼ 8.1 Hz, 2H), 7.39 (d, J ¼ 7.8 Hz, 1H), 7.27 (dd, J ¼ 14.4,
3.8 Hz, 3H), 7.07 (d, J ¼ 8.0 Hz, 1H), 6.78 (d, J ¼ 7.7 Hz, 1H), 6.63 (s,
1H), 5.17 (b, 1H), 3.42 (m, 2H), 3.29 (m, 4H), 2.66 (m, 2H), 2.45 (m,
12H), 2.36 (s, 3H), 2.29 (m, 4H), 1.72 (m, 2H). 13C NMR (101 MHz,
CDCl3) d 167.23, 157.42, 148.55, 139.78, 132.11, 131.35, 129.15, 128.66,
127.75, 126.34, 122.86, 120.58, 111.25, 60.36, 59.70, 57.58, 54.44,
52.68, 51.95, 50.26, 32.36, 24.97, 23.32, 18.37, 16.88, 13.37. IR (KBr,
nmax) cmꢃ1: 3412 (NH stretch); 3046, 3028 (aromatic CeH stretch);
2874, 2717 (aliphatic CeH stretch); 1623 (CeS stretch); 1609, 1584
(aromatic C]C stretch); 1276 (aliphatic CeN stretch); 857 (para
disubstituted benzene); 739 (ortho disubstituted benzene); 681
(aromatic CeCl stretch); HRMS: (ESI m/z) for C29H40ClN6S calcu-
lated: 539.2724, found: 539.2728 (MþH)þ; Anal. Calculated for
5.5.17. 4-(4-(2-(4-(4-(4-(4-nitrophenyl)piperazin-1-yl)butyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7q)
Yellow solid (71%); m.p. 193e195 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.38 (d, J ¼ 9.3 Hz, 2H), 7.48 (d, J ¼ 8.0 Hz, 2H), 7.31 (d, J ¼ 3.0 Hz,
2H), 6.72 (d, J ¼ 9.3 Hz, 2H), 6.62 (s, 1H), 5.52 (b, 2H), 3.65 (m, 6H),
2.71 (m, 2H), 2.63 (m, 6H), 2.52 (m, 6H), 2.43 (m, 4H), 1.74 (m, 2H),
C
29H39ClN6S: C 64.60, H 7.29, Cl 6.58, N 15.59, S 5.95; found: C
1.43 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 167.89, 157.75, 154.78,
64.63, H 7.25, Cl 6.67, N 15.50, S 5.87.
138.37, 136.70, 131.36, 129.48, 127.70, 126.33, 110.23, 109.60, 60.37,
58.26, 57.27, 56.18, 54.29, 52.80, 44.22, 33.25, 24.32, 23.72, 22.19,
19.49, 11.93. IR (KBr, nmax) cmꢃ1: 3457, 3406 (NH stretch); 3076,
3016 (aromatic CeH stretch); 2871, 2765 (aliphatic CeH stretch);
1661 (CeS stretch); 1644, 1607 (aromatic C]C stretch); 1546, 1372
(NO2 stretch); 1259 (aliphatic CeN stretch); 843 (para disubstituted
benzene); 812 (para disubstituted benzene); HRMS: (ESI m/z) for
5.5.14. 4-(4-(2-(4-(4-(4-(2-chlorophenyl)piperazin-1-yl)butyl)
piperazin-1-yl)ethyl)phenyl)-N-methylthiazol-2-amine (7n)
Pale yellow solid (80%); m.p. 145e147 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
7.71 (d, J ¼ 8.1 Hz, 2H), 7.43 (d, J ¼ 7.8 Hz, 1H), 7.32 (dd,
J ¼ 14.4, 3.8 Hz, 3H), 7.12 (d, J ¼ 8.0 Hz, 1H), 6.86 (d, J ¼ 7.7 Hz, 1H),
6.61 (s, 1H), 5.22 (b, 1H), 3.39 (m, 2H), 3.14 (m, 4H), 2.78 (m, 2H),
2.59 (m, 12H), 2.49 (s, 3H), 2.38 (m, 4H), 2.05 (m, 2H), 1.55 (m, 2H).
C
29H40N7O2S calculated: 550.2964, found: 550.2954 (MþH)þ; Anal.
Calculated for C29H39N7O2S: C 63.36, H 7.15, N 17.84, O 5.82, S 5.83;
found: C 63.49, H 7.28, N 17.72, O 5.77, S 5.75.
13C NMR (101 MHz, CDCl3)
d 166.16, 156.82, 149.62, 139.16, 133.21,
131.83, 129.93, 128.41, 127.18, 126.67, 123.26, 120.11, 110.82, 60.43,
58.34, 56.05, 53.83, 52.22, 51.43, 50.34, 33.66, 24.57, 23.26, 18.82,
16.23, 13.71, 11.78. IR (KBr, nmax) cmꢃ1: 3446 (NH stretch); 3052,
3034 (aromatic CeH stretch); 2866, 2723 (aliphatic CeH stretch);
1634 (CeS stretch); 1612, 1591 (aromatic C]C stretch); 1283
(aliphatic CeN stretch); 851 (para disubstituted benzene); 743
(ortho disubstituted benzene); 677 (aromatic CeCl stretch); HRMS:
(ESI m/z) for C30H42ClN6S calculated: 553.2880, found: 553.2859
(MþH)þ; Anal. Calculated for C30H41ClN6S: C 65.13, H 7.47, Cl 6.41, N
15.19, S 5.80; found: C 65.28, H 7.35, Cl 6.47, N 15.22, S 5.85.
5.5.18. 4-(4-(2-(4-(5-(4-(4-nitrophenyl)piperazin-1-yl)pentyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7r)
Yellow solid (79%); m.p. 187e189 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.21 (d, J ¼ 9.3 Hz, 2H), 7.59 (d, J ¼ 8.0 Hz, 2H), 7.22 (d, J ¼ 3.0 Hz,
2H), 6.69 (d, J ¼ 9.3 Hz, 2H), 6.59 (s, 1H), 5.46 (b, 2H), 3.57 (m, 6H),
2.65 (m, 2H), 2.53 (m, 6H), 2.46 (m, 6H), 2.41 (m, 4H), 1.61 (m, 4H),
1.36 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 168.62, 157.38, 155.21,
137.69, 136.75, 131.87, 130.43, 127.26, 126.19, 110.61, 110.04, 61.72,
58.83, 57.86, 56.47, 54.38, 52.23, 45.52, 33.69, 25.68, 24.32, 23.37,
22.93, 19.72, 12.26. IR (KBr, nmax) cmꢃ1: 3463, 3413 (NH stretch);
3084, 3023 (aromatic CeH stretch); 2864, 2751 (aliphatic CeH
stretch); 1678 (CeS stretch); 1637, 1603 (aromatic C]C stretch);
1545, 1361 (NO2 stretch); 1261 (aliphatic CeN stretch); 851 (para
disubstituted benzene); 807 (para disubstituted benzene); HRMS:
(ESI m/z) for C30H42N7O2S calculated: 564.3121, found: 564.3143
(MþH)þ; Anal. Calculated for C30H41N7O2S: C 63.91, H 7.33, N 17.39,
O, 5.68, S 5.69; found: C 63.89, H 7.38, N 17.42, O 5.57, S 5.65.
5.5.15. 1-(4-(2-methylthiazol-4-yl)phenethyl)-4-(3-(4-(2-
chlorophenyl)piperazin-1-yl)propyl)piperazine (7o)
Beige solid (74%); m.p. 156e158 ꢀC; 1H NMR (400 MHz, CDCl3)
d
7.79 (d, J ¼ 8.1 Hz, 2H), 7.35 (d, J ¼ 7.8 Hz, 1H), 7.25 (dd, J ¼ 14.4,
3.8 Hz, 3H), 7.05 (d, J ¼ 8.0 Hz, 1H), 6.98 (d, J ¼ 7.7 Hz, 1H), 6.63 (s,
1H), 3.33 (m, 2H), 3.16 (m, 4H), 2.86 (m, 2H), 2.71 (s, 3H), 2.65 (m,
12H), 2.48 (m, 4H),1.46 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 165.81,
155.04, 149.09,139.78,132.64,130.63,129.04,128.77,127.62,126.42,
123.79, 120.43, 111.80, 59.95, 56.35, 53.30, 52.82, 52.53, 50.91,
33.09, 24.24, 23.54, 19.80, 19.32, 13.71. IR (KBr, nmax) cmꢃ1: 3078,
3031 (aromatic CeH stretch); 2886, 2785 (aliphatic CeH stretch);
1676 (CeS stretch); 1643 (thiazole-CH3 CeC stretch), 1631, 1586
(aromatic C]C stretch); 1278 (aliphatic CeN stretch); 847 (para
disubstituted benzene); 737 (ortho disubstituted benzene); 674
(aromatic CeCl stretch); HRMS: (ESI m/z) for C29H39ClN5S calcu-
lated: 524.2615, found: 524.2633 (MþH)þ; Anal. Calculated for
5.5.19. N-methyl-4-(4-(2-(4-(3-(4-(4-nitrophenyl)piperazin-1-yl)
propyl)piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7s)
Yellow solid (73%); m.p. 181e183 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.29 (d, J ¼ 9.3 Hz, 2H), 7.69 (d, J ¼ 8.0 Hz, 2H), 7.16 (d, J ¼ 3.0 Hz,
2H), 6.75 (d, J ¼ 9.3 Hz, 2H), 6.61 (s, 1H), 5.22 (s, 1H), 3.61 (m, 6H),
2.74 (m, 2H), 2.67 (m, 6H), 2.59 (m, 6H), 2.57 (s, 3H), 2.47 (m, 4H),
1.67 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 167.24, 156.16, 154.27,
C
29H38ClN5S: C 66.45, H 7.31, Cl 6.76, N 13.36, S 6.12; found: C 66.38,
138.77, 136.37, 131.48, 130.55, 128.74, 127.33, 111.47, 110.37, 60.16,
59.72, 57.23, 56.16, 54.77, 52.73, 45.48, 33.77, 29.58, 24.37, 23.25,
19.32, 11.69. IR (KBr, nmax) cmꢃ1: 3447 (NH stretch); 3076, 3037
(aromatic CeH stretch); 2854, 2718 (aliphatic CeH stretch); 1645
(CeS stretch); 1609, 1586 (aromatic C]C stretch); 1531, 1367 (NO2
stretch); 1278 (aliphatic CeN stretch); 842 (para disubstituted
benzene); 812 (para disubstituted benzene); HRMS: (ESI m/z) for
H 7.35, Cl 6.27, N 13.22, S 6.25.
5.5.16. 4-(4-(2-(4-(3-(4-(4-nitrophenyl)piperazin-1-yl)propyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7p)
Yellow solid (69%); m.p. 186e188 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.41 (d, J ¼ 9.3 Hz, 2H), 7.44 (d, J ¼ 8.0 Hz, 2H), 7.33 (d, J ¼ 3.0 Hz,
2H), 6.77 (d, J ¼ 9.3 Hz, 2H), 6.61 (s, 1H), 5.53 (b, 2H), 3.57 (m, 6H),
C
29H40N7O2S calculated: 550.2964, found: 550.2951 (MþH)þ; Anal.

612
H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
Calculated for C29H39N7O2S: C 63.36, H 7.15, N 17.84, O 5.82, S 5.83;
found: C 63.49, H 7.28, N 17.72, O 5.77, S 5.89.
(m, 4H). 13C NMR (101 MHz, CDCl3)
d 168.22, 160.23, 152.64, 149.17,
140.88, 139.25, 133.66, 129.34, 127.61, 114.43, 108.19, 103.51, 61.83,
57.37, 56.11, 53.84, 52.83, 51.24, 46.24, 34.77, 26.49, 24.92. IR (KBr,
nmax) cmꢃ1: 3458, 3419 (NH stretch); 3142, 3081 (aromatic CeH
stretch); 2879, 2719 (aliphatic CeH stretch); 1655 (CeS stretch);
1619, 1593 (aromatic C]C stretch); 1292 (aliphatic CeN stretch);
839 (para disubstituted benzene); HRMS: (ESI m/z) for C28H40N7S
calculated: 506.3066, found: 506.3059 (MþH)þ; Anal. Calculated
for C28H39N7S: C 66.50, H 7.77, N 19.39, S 6.34; found: C 66.67, H
7.62, N 19.42, S 6.47.
5.5.20. N-methyl-4-(4-(2-(4-(4-(4-(4-nitrophenyl)piperazin-1-yl)
butyl)piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7t)
Yellow solid (78%); m.p. 189e191 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.06 (d, J ¼ 9.3 Hz, 2H), 7.81 (d, J ¼ 8.0 Hz, 2H), 7.27 (d, J ¼ 3.0 Hz,
2H), 6.93 (d, J ¼ 9.3 Hz, 2H), 6.63 (s, 1H), 5.26 (s, 1H), 3.42 (m, 6H),
2.79 (m, 2H), 2.69 (m, 6H), 2.56 (m, 6H), 2.52 (s, 3H), 2.43 (m, 4H),
2.01 (m, 2H), 1.46 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 166.01,
156.96, 154.25, 139.43, 137.97, 132.94, 130.66, 127.27, 126.16, 112.28,
110.78, 61.82, 59.83, 57.7 4, 56.46, 53.27, 52.49, 45.72, 33.28, 29.39,
24.82, 23.29, 19.77, 13.23, 11.62. IR (KBr, nmax) cmꢃ1: 3456 (NH
stretch); 3087, 3041 (aromatic CeH stretch); 2844, 2721 (aliphatic
CeH stretch); 1656 (CeS stretch); 1631, 1595 (aromatic C]C
stretch); 1527, 1362 (NO2 stretch); 1286 (aliphatic CeN stretch);
852 (para disubstituted benzene); 806 (para disubstituted ben-
zene); HRMS: (ESI m/z) for C30H42N7O2S calculated: 564.3121,
found: 564.3139 (MþH)þ; Anal. Calculated for C30H41N7O2S: C
63.91, H 7.33, N 17.39, O 5.68, S 5.69; found: C 63.89, H 7.39, N 17.42,
O 5.85, S 5.73.
5.5.24. N-methyl-4-(4-(2-(4-(3-(4-(pyridin-2-yl)piperazin-1-yl)
propyl)piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7x)
Beige solid (71%); m.p. 179e181 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.62 (dd, J ¼ 4.7, 1.5 Hz, 1H), 7.11 (d, J ¼ 7.8 Hz, 2H), 7.49 (ddd,
J ¼ 8.1, 6.7, 1.7 Hz, 1H), 7.34 (d, J ¼ 8.7 Hz, 2H), 6.92e6.53 (m, 3H),
5.37 (s, 1H), 3.54e3.43 (m, 4H), 2.93 (dd, J ¼ 9.7, 5.8 Hz, 2H),
2.72e2.63 (m, 6H), 2.53e2.45 (m, 8H), 2.38e2.27 (m, 7H),
1.78e1.66 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 166.89, 158.95,
152.44, 148.21, 138.62, 138.11, 133.84, 129.15, 127.84, 114.37, 108.26,
103.44, 59.51, 57.72, 55.94, 53.32, 52.73, 51.22, 46.53, 34.35, 29.83
26.62. IR (KBr, nmax) cmꢃ1: 3426 (NH stretch); 3161, 3102 (aromatic
CeH stretch); 2883, 2725 (aliphatic CeH stretch); 1671 (CeS
stretch); 1625, 1598 (aromatic C]C stretch); 1282 (aliphatic CeN
stretch); 847 (para disubstituted benzene); HRMS: (ESI m/z) for
5.5.21. 1-(4-(2-methylthiazol-4-yl)phenethyl)-4-(3-(4-(4-
nitrophenyl)piperazin-1-yl)propyl)piperazine (7u)
Pale yellow solid (73%); m.p. 177e179 ꢀC; 1H NMR (400 MHz,
C
28H40N7S calculated: 506.3066, found: 506.3041 (MþH)þ; Anal.
CDCl3)
d
8.11 (d, J ¼ 9.3 Hz, 2H), 7.78 (d, J ¼ 8.0 Hz, 2H), 7.24 (d,
J ¼ 3.0 Hz, 2H), 6.81 (d, J ¼ 9.3 Hz, 2H), 6.61 (s, 1H), 3.49 (m, 6H),
Calculated for C28H39N7S: C 66.50, H 7.77, N 19.39, S 6.34; found: C
66.66, H 7.82, N 19.44, S 6.49.
2.81 (m, 2H), 2.76 (s, 3H), 2.63 (m, 6H), 2.58 (m, 6H), 2.44 (m, 4H),
1.46 (m, 2H). 13C NMR (101 MHz, CDCl3)
d 165.84, 155.02, 154.85,
139.89, 138.39, 132.61, 129.04, 126.41, 125.96, 112.61, 111.81, 60.06,
59.15, 56.42, 56.31, 53.01, 52.68, 46.99, 33.19, 24.23, 23.94, 19.80,
19.34,13.71. IR (KBr, nmax) cmꢃ1: 3122, 3076 (aromatic CeH stretch);
2867, 2726 (aliphatic CeH stretch); 1662 (CeS stretch); 1639
(thiazole-CH3 CeC stretch); 1628, 1597 (aromatic C]C stretch);
1523, 1356 (NO2 stretch); 1276 (aliphatic CeN stretch); 844 (para
disubstituted benzene); 807 (para disubstituted benzene); HRMS:
(ESI m/z) for C29H39N6O2S calculated: 535.2855, found: 535.2862
(MþH)þ; Anal. Calculated for C29H38N6O2S: C 65.14, H 7.16, N 15.72,
O 5.98, S 6.00; found: C 65.29, H 7.20, N 15.62, O 5.88, S 6.07.
5.5.25. N-methyl-4-(4-(2-(4-(4-(4-(pyridin-2-yl)piperazin-1-yl)
butyl)piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7y)
Off white solid (73%); m.p. 191e193 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
8.35 (dd, J ¼ 5.1, 1.6 Hz, 1H), 7.82 (d, J ¼ 8.1 Hz, 2H), 7.72
(ddd, J ¼ 7.6, 6.2, 1.3 Hz, 1H), 7.34 (d, J ¼ 7.6 Hz, 2H), 6.61e6.54 (m,
3H), 5.41 (s, 1H), 3.53e3.41 (m, 4H), 2.68 (dd, J ¼ 9.2, 6.7 Hz, 2H),
2.55e2.47 (m, 6H), 2.43e2.37 (m, 8H), 2.29e2.23 (m, 7H),1.92e1.86
(m, 4H). 13C NMR (101 MHz, CDCl3)
d 169.44, 161.56, 151.62, 150.67,
141.34, 140.87, 134.12, 130.73, 128.81, 115.99, 109.44, 104.33, 60.52,
56.84, 55.73, 54.24, 53.45, 51.73, 46.87, 35.41, 27.16, 25.84, 24.21. IR
(KBr, nmax) cmꢃ1: 3422 (NH stretch); 3157, 3104 (aromatic CeH
stretch); 2877, 2713 (aliphatic CeH stretch); 1679 (CeS stretch);
1644, 1587 (aromatic C]C stretch); 1273 (aliphatic CeN stretch);
851 (para disubstituted benzene); HRMS: (ESI m/z) for C29H42N7S
calculated: 520.3222, found: 520.3234 (MþH)þ; Anal. Calculated
for C29H41N7S: C 67.02, H 7.95, N 18.86, S 6.17; found: C 67.16, H 7.88,
N 18.94, S 6.19.
5.5.22. 4-(4-(2-(4-(3-(4-(pyridin-2-yl)piperazin-1-yl)propyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7v)
White solid (84%); m.p. 175e177 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.19 (dd, J ¼ 4.9, 1.2 Hz, 1H), 7.67 (d, J ¼ 8.2 Hz, 2H), 7.47 (ddd,
J ¼ 8.8, 7.2, 2.0 Hz, 1H), 7.20 (d, J ¼ 8.2 Hz, 2H), 6.83e6.49 (m, 3H),
5.45 (s, 2H), 3.59e3.51 (m, 4H), 2.81 (dd, J ¼ 9.9, 6.3 Hz, 2H),
2.74e2.59 (m, 6H), 2.59e2.48 (m, 8H), 2.47e2.39 (m, 4H), 1.82e1.68
(m, 2H). 13C NMR (101 MHz, CDCl3)
d
167.49, 159.53, 151.14, 147.93,
139.75, 137.48, 132.71, 128.92, 126.05, 113.31, 107.10, 102.11, 60.22,
56.67, 56.60, 53.12, 53.05, 52.96, 45.17, 33.24, 24.14. IR (KBr, nmax
5.5.26. 1-(4-(2-methylthiazol-4-yl)phenethyl)-4-(3-(4-(pyridin-2-
yl)piperazin-1-yl)propyl)piperazine (7z)
)
cmꢃ1: 3461, 3421 (NH stretch); 3136, 3071 (aromatic CeH stretch);
2875, 2733 (aliphatic CeH stretch); 1658 (CeS stretch); 1631, 1602
(aromatic C]C stretch); 1284 (aliphatic CeN stretch); 846 (para
disubstituted benzene); HRMS: (ESI m/z) for C27H38N7S calculated:
492.2909, found: 492.2912 (MþH)þ; Anal. Calculated for
Off white solid (79%); m.p. 180e182 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
8.19 (dd, J ¼ 4.9, 1.2 Hz, 1H), 7.67 (d, J ¼ 8.2 Hz, 2H), 7.47
(ddd, J ¼ 8.8, 7.2, 2.0 Hz, 1H), 7.20 (d, J ¼ 8.2 Hz, 2H), 6.83e6.49 (m,
3H), 5.45 (s, 2H), 3.59e3.51 (m, 4H), 2.81 (dd, J ¼ 9.9, 6.3 Hz, 2H),
2.74e2.59 (m, 6H), 2.59e2.48 (m, 8H), 2.47e2.39 (m, 4H), 1.82e1.68
C
27H37N7S: C 65.95, H 7.58, N 19.94, S 6.52; found: C 65.89, H 7.50, N
(m, 2H). 13C NMR (101 MHz, CDCl3)
d
167.49, 159.53, 151.14, 147.93,
139.75, 137.48, 132.71, 128.92, 126.05, 113.31, 107.10, 102.11, 60.22,
56.67, 56.60, 53.12, 53.05, 52.96, 45.17, 33.24, 24.14. IR (KBr, nmax
19.82, S 6.57.
)
5.5.23. 4-(4-(2-(4-(4-(4-(pyridin-2-yl)piperazin-1-yl)butyl)
piperazin-1-yl)ethyl)phenyl)thiazol-2-amine (7w)
cmꢃ1: 3164, 3096 (aromatic CeH stretch); 2869, 2710 (aliphatic
CeH stretch); 1682 (CeS stretch); 1639 (thiazole-CH3 CeC stretch);
1612, 1592 (aromatic C]C stretch); 1281 (aliphatic CeN stretch);
844 (para disubstituted benzene); HRMS: (ESI m/z) for C28H39N6S
calculated: 491.2957, found: 491.2967 (MþH)þ; Anal. Calculated for
Off white solid (77%); m.p. 182e184 ꢀC; 1H NMR (400 MHz,
CDCl3)
d
8.23 (dd, J ¼ 4.7, 1.1 Hz, 1H), 7.78 (d, J ¼ 7.9 Hz, 2H), 7.61
(ddd, J ¼ 8.1, 6.9, 1.8 Hz, 1H), 7.22 (d, J ¼ 8.1 Hz, 2H), 6.72e6.56 (m,
3H), 5.39 (s, 2H), 3.55e3.47 (m, 4H), 2.77 (dd, J ¼ 9.7, 6.6 Hz, 2H),
2.68e2.54 (m, 6H), 2.49e2.36 (m, 8H), 2.33e2.26 (m, 4H),1.91e1.72
C
28H38N6S: C 68.53, H 7.81, N 17.13 S, 6.53; found: C 68.46, H 7.74, N
17.24, S 6.45.

H.N. Nagesh et al. / European Journal of Medicinal Chemistry 84 (2014) 605e613
613
5.6. Anti-tubercular activity against MTB H37RV strain
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umns 3 to 11 received 100
solutions were added to the wells in rows B to G in columns 2 and
3. By using a multichannel pipette, 100 l was transferred from
ml of 7H9GC broth. 100
mL of 2 ꢄ drug
m
column 3 to column 4, and the contents of the wells were mixed
well. Identical serial 1:2 dilutions were continued through column
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column 10. 100
B to G in columns 2 to 10. 100
control), 100 L of MTB inoculum to D11 and E11 and 100
m
l of excess medium was discarded from the wells in
L of MTB inoculum was added to the wells in rows
L of medium to B11 and C11 (media
L of
m
m
m
m
MTB inoculum with 3e5% DMSO to F11 and G11 (solvent control)
were added. The plates were sealed with parafilm and were
incubated at 37 ꢀC for 5 days. 50
mL of a freshly prepared 1:1
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day). The microplates were resealed with parafilm and were
incubated for an additional 24 h at 37 ꢀC, and the colours of all
wells were recorded. A blue colour in the well was interpreted as
no growth, and a pink colour was scored as growth. A few wells
appeared violet after 24 h of incubation, but they invariably
changed to pink after another day of incubation and thus were
scored as growth (while the adjacent blue wells remained blue).
The MIC was defined as the lowest drug concentration which
prevented a colour change from blue to pink.
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Most active compounds 7a, 7f, 7g, 7h, 7j, 7n, 7p, 7r and 7v were
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