New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities

Article abstract of DOI:10.1007/s00706-020-02674-7

Abstract: Novel 2-aminopyrimidine derivatives were prepared from acyclic starting materials, benzylidene acetones and ammonium thiocyanates, via 5 steps, including ring closure, aromatization, S-methylation, oxidation to methylsulfonyl compounds, and formation of guanidines with suitable amines. The prepared compounds differ from each other by the substitutions of their amino group and of their phenyl ring. The 2-aminopyrimidines were tested by use of microplate assays for their in vitro activities against a causative organism of sleeping sickness, Trypanosoma brucei rhodesiense, as well as against a causative organism of malaria, Plasmodium falciparum NF54. Their cytotoxic properties were determined with L-6 cells (rat skeletal myoblasts). Some of the compounds exhibited quite good antitrypanosomal activity, and others showed excellent antiplasmodial activity. The influence of the structural modifications on these activities is discussed. Graphic abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s00706-020-02674-7

Monatshefte für Chemie - Chemical Monthly
https://doi.org/10.1007/s00706-020-02674-7
ORIGINAL PAPER
New 2‑aminopyrimidine derivatives and their antitrypanosomal
and antiplasmodial activities
Michael Hofelner1 · Usama Hassan1 · Werner Seebacher1 · Johanna Dolensky1 · Patrick Hochegger1 ·
Marcel Kaiser2 · Pascal Mäser2 · Robert Saf3 · Robert Weis1
Received: 19 June 2020 / Accepted: 10 August 2020
© The Author(s) 2020
Abstract
Novel 2-aminopyrimidine derivatives were prepared from acyclic starting materials, benzylidene acetones and ammonium
thiocyanates, via 5 steps, including ring closure, aromatization, S-methylation, oxidation to methylsulfonyl compounds, and
formation of guanidines with suitable amines. The prepared compounds difer from each other by the substitutions of their
amino group and of their phenyl ring. The 2-aminopyrimidines were tested by use of microplate assays for their in vitro
activities against a causative organism of sleeping sickness, Trypanosoma brucei rhodesiense, as well as against a causative
organism of malaria, Plasmodium falciparum NF54. Their cytotoxic properties were determined with L-6 cells (rat skeletal
myoblasts). Some of the compounds exhibited quite good antitrypanosomal activity, and others showed excellent antiplas-
modial activity. The infuence of the structural modifcations on these activities is discussed.
Graphic abstract
Keywords Antiplasmodial activity · Antitrypanosomal activity · Heterocycles · Drug research · Structure–activity
relationships
Introduction
In the past two decades, over two billion of the world’s
poorest people have been afected by neglected tropical dis-
eases (NTDs). One of the 11 major NTDs studied is human
African trypanosomiasis (HAT) [1]. HAT or sleeping sick-
ness is caused by protozoa of the genus Trypanosoma like
Trypanosoma brucei gambiense (Tbg) and Trypanosoma
brucei rhodesiense (Tbr). The vector is the tsetse fy. Only
one drug, melarsoprol, is available for the late-stage Tbr
infection treatment [2]. This toxic arsenic compound causes
severe side efects including a deadly encephalopathy in
more than 5% of the patients [3]. Therefore it is an urgent
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s00706-020-02674-7) contains
supplementary material, which is available to authorized users.
* Werner Seebacher
we.seebacher@uni-graz.at
1
Institute of Pharmaceutical Sciences, University of Graz,
Graz, Austria
2
Swiss Tropical and Public Health Institute and University
of Basel, Basel, Switzerland
3
Institute for Chemistry and Technology of Materials (ICTM),
Graz University of Technology, Graz, Austria
Vol.:(0123456789)
1 3

M. Hofelner et al.
need to develop new efcient antitrypanosomal compounds
with less side efects.
chloroform yielding 4a–4d. The next step was an oxidation
to the methylsulfonyl compounds 5a–5d with m-chloro-
perbenzoic acid in dichloromethane. The fnal formation of
the target compounds 6–10 took place in dioxane or tet-
rahydrofuran in the presence of the various amines under
microwave irradiation at 120 °C or under refux. Struc-
tural modifcations were restricted to the amino substituent
including amino, a (pyrrolidin-1-yl) and (4-methylpiperazin-
1-yl) groups of compounds 6–8. Moreover, partial structures
of chloroquine were used as substituents for compounds 9
and 10. The chiral aliphatic amine moiety was connected
with the pyrimidine core giving compounds 9 as racemates.
In a further step, the quinoline residue was attached. Simi-
lar compounds, bearing an additional ester function have
already been investigated [15]. Further variations concerned
the substitution pattern of a phenyl ring (Scheme 1).
In 2018 malaria globally afected 228 million people and
caused 405,000 deaths [4]. The emergence and spread of
resistance in Plasmodium falciparum malaria to artemisinin
combination therapies in the Greater Mekong subregion
poses a major threat to malaria control and elimination [5].
Since the last defense line, the artemisinines, might fall pos-
sibly, there is a great demand for antiplasmodial compounds
with alternative mechanism of action.
Substituted pyrimidines were described early as antiplas-
modial compounds [6–12]. Some 2-aminopyrimidines were
reported to be active in low micromolar to submicromolar
concentration [13]. We prepared new methyl-aryl-substituted
2-aminopyrimidines including compounds bearing partial
structures of chloroquine which were connected to the nitro-
gen in ring position 2.
Scheme 1. Syntheses of compounds 2–10. Reagents and
conditions: (i) benzene, cyclohexanol, water separator, refux,
6 h, (ii) S, xylene, refux, overnight, (iii) CH3I, CHCl3, r.t.,
overnight to 3 days, (iv) m-chloroperbenzoic acid, CH2Cl2,
0–20 °C, 2 h, (v) NH3 conc. or amine, dioxane or THF, 85 °C,
refux overnight or microwave 120 °C 2–13 h. For the aroma-
tization from 2a–2d to 3a–3d we observed the disappearance
of the proton signal at 4.9 ppm of the CH group attached to
the aromatic moiety in 1H NMR spectra as well as the shift
of the signal of the olefnic proton from 4.7 ppm to 7.3 ppm.
Furthermore, the signals of the NH protons at 8.8 and 9.5 ppm
Results and discussion
Starting from benzylidene acetones 1a–1d pyrimidine-
thiones 2a–2d were prepared by reaction with ammonium
thiocyanate in refuxing benzene/cyclohexanol [14]. Aroma-
tization of the heterocyclic ring took place in boiling xylene
in the presence of sulfur giving compounds 3a–3d. Subse-
quently the SH group was methylated using methyl iodide in
Scheme 1
H
N
O
N
SCH
HI
S
N
SH
3
i
ii
iii
N
NH
N
NH SCN
4
1
R
1a-1d
1
a
b
c
d
: R = H
1
: R = Cl
1
1
1
R
R
R
1
: R = CH3
4a-4d
1
2a-2d
3a-3d
: R = OCH3
2
3
6a 6d
7a-7d
8a 8d
-
-
: R = R = H
iv
2
3
: R + R = -(CH2)4-
3'
2'
2
3
: R + R = -(CH2)2-N(CH3)-CH2-CH2-
2
R
O
S
CH
3
N
R
N
N
R
2
3
2''
1''
5'
3'
R
1'
2'
O
4'
2
3
N
9a-9d
: R = H, R =
N
N
v
N
Cl
2
3
1
1
10a-10d
: R = H, R =
2'
NH
3'
5a-5d
6-10
1 3

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities
Table 1 Antiprotozoal and cytotoxic activities of compounds 6–10
(IC50 values in µM)
disappeared and a new signal was observed for the SH group at
13.5 ppm. In 13C spectra, the signal of the carbon attached to
the aromatic moiety shifted from 54 to 165 ppm due to aroma-
tization. S-Methylation to compounds 4a–4d caused appear-
ance of an additional signal at 2.6 ppm for the methylthio
group in 1H NMR spectra and at 13.8 ppm in 13C spectra. The
subsequent oxidation to the methylsulfonyl group in 5a–5d
shifted the signal of the attached methyl group from 2.6 ppm
to 3.4 ppm in 1H NMR spectra and from 13.8 ppm to 39 ppm
in 13C spectra. The replacement of the methylsulfonyl group of
compunds 5a–5d by amino substituents shifted the signal for
the C-2 2–6 ppm to lower frequencies. Moreover, we observed
long-range couplings from protons of the amino substituent to
C-2 in HMBC spectra of compounds 6–10 which confrmed
the attachment of the amino groups to this ring position.
All 2-aminopyrimidine derivatives 6–10 were tested for
their antiplasmodial activities against P. falciparum NF54
and for their antitrypanosomal potencies against Trypanosoma
brucei rhodesiense STIB 200 as well as for their cytotoxicity
against rat skeletal myoblasts (L-6 cells) in microplate assays.
The results are presented in Table 1.
Cpd
L-6 cells P. falciparum NF54
T. b. rhodesiense
a
a
b
a
c
IC50
IC50
SIPN
IC50
SIT
6a
304
439
270
465
215
107
178
178
89.4
33.1
61.1
70.2
59.3
12.6
31.8
78.8
19.6
9.90
14.3
3.24
7.78
116.9
0.012
270
139
112
204
1.12
3.16
2.41
2.28
2.47
4.71
7.84
5.04
2.18
2.96
5.18
2.37
3.59
4.81
5.76
1.08
140
172
1.77
5.78
2.93
12.3
1.00
0.68
0.85
0.96
12.8
17.4
25.5
11.3
9.22
30.7
30.9
11.4
2.28
2.35
2.92
0.81
1995
6b
75.9
92.3
37.9
214
158
210
6c
6d
7a
86.9
22.7
22.7
35.3
41.0
11.2
11.8
29.6
16.5
2.62
5.52
73.0
0.14
0.045
0.10
0.04
7b
7c
7d
185
8a
7.00
1.90
2.40
6.20
6.43
0.41
1.03
6.93
8.62
4.22
4.90
3.98
0.0039
8b
8c
8d
9a
9b
9c
9d
10a
10b
10c
10d
Meld
CQe
Pf
A series of 4-alkyl-6-(hetero)arylpyrimidin-2-amines
was reported to possess promising antiplasmodial activ-
ity (IC50 = 0.115–3.96 µM); however, the significance of
the results was not sustained by cytotoxicity data [13]. Our
2-amino compounds 6a–6d, 7a–7d, and 8a–8d were com-
pletely inactive (IC50 =11.2–270 µM) against P. falciparum
NF54. The by far lower activity of our 6-methyl compound
6b (IC50 =139 µM) compared to its 6-isopropyl analogue
(IC50 =3.96 µM) [13] may be explained by the use of difer-
ent strains test methods. The substitution of the amino group
with the side chain of chloroquine improved the antiplasmodial
activity (9a–9c: IC50 =2.62–73.0 µM) only slightly. Moreover,
the selectivity indexes of compounds 6–9 (SIPN =1.08–7.84)
were very low. High activity against P. falciparum NF54
(IC50 =0.04–0.14 µM) and good selectivity (SIPN =81–220)
was observed for the 2-aminopyrimidines 10a–10d, which
exhibit a 4-aminoquinoline partial structure linked to their
amino nitrogen. The most active compound 10d was addition-
ally tested against the multiresistant K1 strain of P. falciparum
and showed slightly decreased activity (IC50 =0.14 µM) but
is more active than chloroquine (IC50 =0.27 µM) [16] against
this strain.
220
143
81
0.007
16,700
aValues represent the average of four determinations (two determina-
tions of two independent experiments) indicated in µM
bSelectivity index for P. falciparum NF54 (SIPN), expressed as ratio
[IC50(L6)/IC50(P. falciparum NF54)]
cSelectivity index for T. b. rhodesiense (SIT), expressed as ratio
[IC50(L6)/IC50(T. b. rhodesiense)]. Reference compounds (Fig. 1)
dMel, melarsoprol
eCQ, chloroquine diphosphate
fP, podophyllotoxin
Conclusion
Most of the new compounds exhibited weak or negligible
antitrypanosomal activity (IC50 =6.20–214 µM) or low selec-
tivity (SIT =0.68–5.78) or both of them. However, moderate
activity (IC50 =1.90, 2.40 µM) and quite good selectivity
(SIT =17.4, 25.5) were observed for compounds 8b, 8c with
4-methylpiperazinyl substitution. The most promising anti-
trypanosomal compounds 9b and 9c (IC50 =0.41, 1.03 µM;
SIT =30.7, 30.9) feature the side chain of chloroquine.
Several new methyl-aryl-substituted 2-aminopyrimi-
dines with differing amino and phenyl substitution have
been prepared. The antitrypanosomal and antiplasmodial
activities of the new compounds were determined. The
most active antitrypanosomal compounds (IC50 = 0.41,
1.03 µM) exhibited the same side chain as chloroquine.
Compounds possessing the 7-chloroquinoline partial
structure of chloroquine showed excellent activity against
P. falciparum NF54 (IC50 = 0.04–0.14 µM). The most
1 3

M. Hofelner et al.
Fig. 1 Structures of reference
compounds
active compound was additionally tested against the mul-
tiresistant K1 strain of P. falciparum and showed twice
the activity of chloroquine against this strain. Therefore,
this compound could be a lead for further optimization.
plates (Merck, silica gel 60 F254 0.2 mm, 200 × 200 mm);
TLC plates (Merck, Alox 60 F254 neutral, 200×200 mm);
the substances were detected in UV light at 254 nm. Unless
otherwise stated silica gel was used for separations (CC,
TLC). Microwave-assisted reactions were carried out in a
CEM Discover/Explorer system in sealed 10 cm3 standard
vessels with temperature control. Syntheses of compounds
2a, 2b, and 2d were described previously [14]. Compund 3a
was prepared following a reported procedure [17]. Its melt-
ing point (201–205 °C) corresponded well with the reported
one (202–204 °C) [18]. The synthesis of 4a was already
described and the melting point (214 °C) corresponded well
with the reported one (213 °C) [19].
Experimental
Melting points were obtained on a digital melting point
apparatus Electrothermal IA 9200. IR spectra: Bruker Alpha
Platinum ATR FT-IR spectrometer (KBr discs). NMR spec-
tra: Varian Inova 400 (300 K) 5 mm tubes, spectra were
acquired in CDCl3 containing 0.03% TMS. Chemical shifts
1
were recorded in parts per million (ppm), for H spectra
TMS (0.00 ppm) was used as internal standard and for 13
C
6‑Methyl‑4‑(4‑methylphenyl)‑3,4‑dihydropyrimi‑
dine‑2(1H)‑thione (2c, C12H14N2S) The reaction of 21.27 g
of 1c (132.76 mmol) with 8.26 g of ammonium thiocyanate
(108.5 mmol) was carried out in 400 cm3 of toluene in the
presence of 4.12 g of cyclohexanol (41.16 mmol). The mix-
ture was heated for 18 h at 160 °C oil bath temperature using
a water separator flled with molecular sieves 4 Å. After
cooling to r.t., the orange precipitate was collected by fltra-
tion, washed with ether and ethanol. Then it was dissolved
in a mixture of hot ethanol/isopropanol (3:1), treated with
charcoal and fltered. The fltrate was concentrated in vacuo.
Thereafter it was allowed to stand overnight at r.t. to com-
plete crystallization. The product was collected by fltration,
washed with ethanol, and dried. Yield: 11.85 g of 2c (41%)
as white crystals. Rf =0.84 (benzene:CHCl3:EtOH=4:4:1);
m.p.: 207 °C; 1H NMR (DMSO-d6, 400 MHz):δ = 1.69 (s,
3H, CH3), 2.26 (s, 3H, ArCH3), 4.68 (d, J = 1.8 Hz, 1H,
H-5), 4.85 (s, 1H, H-4), 7.10 (d, J=8.1 Hz, 2H, ArH), 7.15
(d, J=7.7 Hz, 2H, ArH), 8.76 (s, 1H, H-3), 9.52 (s, 1H, H-1)
spectra the central peak of the CDCl3 peak was used as the
internal reference (77.0 ppm). Some spectra were acquired
in DMSO-d6. Here the proton signal at 2.49 ppm served as
internal reference as well as the central peak of the DMSO-
d6 signal at 39.7 ppm. Abbreviations: aromatic H, ArH;
aromatic C, ArC, quaternary aromatic C, ArCq. Signal mul-
tiplicities are abbreviated as follows: s, singlet; d, doublet;
t, triplet; m, multiplet; q, quartet; br, broad. Coupling con-
stants (J) are reported in Hertz (Hz). 1H and 13C resonances
were assigned using 1H, 1H- and 1H, 13C-correlation spectra.
1H and 13C resonances are numbered as given in the formu-
lae. Assignments marked with an asterisk are interchange-
able. HRMS: GCT-Premier, Waters (EI, 70 eV). Materials:
column chromatography (CC): silica gel 60 (Merck 70–230
mesh, pore-diameter 0.6 nm), aluminium oxide (Alox) basic
(Fluka for chromatography, 0.05–0.15 mm, Brockmann
activity I, basic); Alox neutral 90 (Merck, 0.063–0.2 mm,
activity I, neutral); thin-layer chromatography (TLC): TLC
1 3

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities
ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 17.87 (CH3),
20.90 (ArCH3), 54.75 (C-4), 99.49 (C-5), 126.43, 129.24
(ArC), 130.78 (C-6), 136.73, 142.05 (ArCq), 174.18 (C-2)
ppm; IR (KBr): v = 3184, 2987, 1706, 1569, 1489, 1323,
1197, 1180, 844, 819, 790 cm−1; HRMS (EI+): m/z calcd
C12H14N2S [M+] 218.0878, found 218.0874.
after crystallization with ethanol 2.02 g of 3d (32%) as buf
powder. Rf = 0.48 (CH2Cl2:CH3OH = 10:1); m.p.: 243–
245 °C; 1H NMR (DMSO-d6, 400 MHz): δ = 2.32 (s, 3H,
CH3), 3.83 (s, 3H, OCH3), 7.06 (d, J= 8.8 Hz, 2H, ArH),
7.30 (s, 1H, H-5), 8.11 (d, J=8.8 Hz, 2H, ArH), 13.50 (br,
s, 1H, SH) ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 18.71
(CH3), 55.69 (OCH3), 105.26 (C-5), 114.53 (ArC), 127.62
(ArCq), 130.03 (ArC), 158.22 (C-6), 162.81 (ArCq), 164.92
(C-4), 181.09 (C-2) ppm; IR (KBr): v=2836, 1619, 1605,
1581, 1553, 1456, 1340, 1257, 1242, 1203, 1168, 1027, 976,
818 cm−1; HRMS (EI +): m/z calcd. (C12H12N2OS) [M+]
232.0670, found 232.0655.
Preparation of pyrimidine‑2‑thiols 3b–3d
The aromatization of dihydropyrimidine-2(1H)-thiones
2b, 2c, and 2d took place overnight in refuxing xylene
in the presence of sulfur. The solution was then allowed
to cool to r.t.. A precipitate was formed which was col-
lected by fltration. The solid was stirred with 1 N NaOH
and fltered. The fltrate was acidifed with 2 N HCl. The
precipitate was collected by fltration, washed with water
and recrystallized.
Preparation of (methylsulfanyl)pyrimidine
hydroiodides 4b–4d
To a stirred suspension of 3b, 3c, or 3d in CHCl3 methyli-
odide (CH3I) was added dropwise. Stirring was continued
at r.t. for up to 3 days. Then the formed solid was collected
by fltration. The fltrate was evaporated to dryness and the
residue was crystallized by treatment with ethyl acetate to
give a second portion of the product. The solids were com-
bined and dried.
4‑(4‑Chlorophenyl)‑6‑methylpyrimidine‑2‑thiol (3b,
C11H9ClN2S) Reaction of 3.99 g of 2b (16.7 mmol) with
3.2 g of sulfur (0.1 mol) in 24 cm3 of xylene yielded
after crystallization from a mixture of ethanol and pro-
pan-2-ol 1.75 g of 3b (44%) as orange powder. Rf = 0.58
(CH2Cl2:CH3OH=10:1); m.p.: 249 °C; 1H NMR (DMSO-
d6, 400 MHz): δ = 2.34 (s, 3H, CH3), 7.37 (s, 1H, H-5),
7.59 (d, J = 8.7 Hz, 2H, ArH), 8.13 (d, J = 8.6 Hz, 2H,
ArH), 13.72 (br, s, 1H, SH) ppm; 13C NMR (DMSO-d6,
100 MHz): δ = 18.82 (CH3), 106.08 (C-5), 129.23, 129.84
(ArC), 134.31, 137.25 (ArCq), 159.37 (C-6), 164.36 (C-4),
181.34 (C-2) ppm; IR (KBr): v=3441, 2920, 2360, 1611,
1577, 1552, 1457, 1280, 1230, 1169, 1090, 977, 809 cm−1;
HRMS (EI +): m/z calcd. (C11H9ClN2S) [M+] 236.0175,
found 236.0162.
4‑(4‑Chlorophenyl)‑6‑methyl‑2‑(methylsulfanyl)pyrimi‑
dine hydroiodide (4b, C12H12ClIN2S) Reaction of 1.65 g of
3b (6.9 mmol) in 50 cm3 of CHCl3 with 2.48 g of CH3I
(17.4 mmol) yielded overnight 1.948 g of 4b (75%) as yel-
low-orange precipitate. Rf =0.60 (CH2Cl2:CH3OH=10:1);
1
m.p.: 193 °C; H NMR (DMSO-d6, 400 MHz): δ = 2.46
(s, 3H, CH3), 2.57 (s, 3H, SCH3), 7.60 (d, J=8.6 Hz, 2H,
ArH), 7.70 (s, 1H, H-5), 8.20 (d, J = 8.6 Hz, 2H, ArH)
ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 13.81 (SCH3),
23.96 (CH3), 112.00 (C-5), 129.04, 129.29 (ArC), 134.85,
136.32 (ArCq), 161.71 (C-4), 168.66 (C-6), 171.25 (C-2)
ppm; IR (KBr): v = 2862, 1610, 1577, 1552, 1455, 1335,
1279, 1229, 1168, 1089, 1010, 977, 818, 808 cm−1; HRMS
(EI +): m/z calcd. (C11H8ClN2S) [M+-H-CH3I] 235.0097,
found 235.0092.
4‑Methyl‑6‑(4‑methylphenyl)pyrimidine‑2‑thiol (3c,
C12H12N2S) Reaction of 11.85 g of 2c (54.28 mmol) with
2.09 g of sulfur (65.2 mmol) in 80 cm3 of xylene yielded
after crystallization from ethanol 4.35 g of 3c (37%) as
yellow powder. Rf = 0.57 (CH2Cl2:CH3OH = 10:1); m.p.:
249 °C; 1H NMR (DMSO-d6, 400 MHz): δ = 2.33 (s, 3H,
CH3), 2.36 (s, 3H, ArCH3), 7.32–7.34 (m, 3H, H-5, ArH),
8.03 (d, J=8.1 Hz, 2H, ArH), 13.60 (br, s, 1H, SH) ppm;
13C NMR (DMSO-d6, 100 MHz): δ = 18.75 (CH3), 21.26
(ArCH3), 105.78 (C-5), 128.05, 129.74 (ArC), 132.69,
142.58 (ArCq), 158.67 (C-4), 165.39 (C-6), 181.27 (C-2)
ppm; IR (KBr): v = 2827, 1612, 1577, 1553, 1453, 1336,
1288, 1238, 1198, 1173, 976, 811 cm−1; HRMS (EI+): m/z
calcd. (C12H12N2S) [M+] 216.0721, found 216.0712.
4‑Methyl‑6‑(4‑methylphenyl)‑2‑(methylsulfanyl)pyrimi‑
dine hydroiodide (4c, C13H15IN2S) Reaction of 4.21 g of 3c
(19.46 mmol) in 250 cm3 of CHCl3 with 6.63 g of CH3I
(46.71 mmol) yielded after 3 days 5.73 g of 4c (82%) as
brown solid. Rf =0.81 (CH2Cl2:MeOH=10:1); m.p.: 208–
209 °C; 1H NMR (DMSO-d6, 400 MHz): δ = 2.34 (s, 3H,
ArCH3), 2.43 (s, 3H, CH3), 2.56 (s, 3H, SCH3), 7.31 (d,
J=8.1 Hz, 2H, ArH), 7.66 (s, 1H, H-5), 8.06 (d, J=8.1 Hz,
2H, ArH) ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 13.79
(SCH3), 21.27 (ArCH3), 23.55 (CH3), 111.68 (C-5), 127.31,
129.82 (ArC), 132.99, 141.77 (ArCq), 163.21 (C-6), 167.73
(C-4), 170.49 (C-2) ppm; IR (KBr): v=2732, 1620, 1578,
4‑(4‑Methoxyphenyl)‑6‑methylpyrimidine‑2‑thiol (3d,
C12H12N2OS) Reaction of 6.29 g of 2d (26.86 mmol) with
1.03 g of sulfur (32.23 mmol) in 40 cm3 of xylene yielded
1 3

M. Hofelner et al.
1429, 1349, 1298, 1273, 1206, 1190, 834 cm−1; HRMS
(EI +): m/z calcd. (C13H14N2S) [M+-HI] 230.0878, found
230.0877.
4‑(4‑Chlorophenyl)‑2‑(methanesulfonyl)‑6‑methylpy‑
rimidine (5b, C12H11ClN2O2S) Reaction of 378 mg of 4b
(1.00 mmol) in 36 cm3 of CH2Cl2 with 1 g of 3-chloro-
peroxybenzoic acid (4.46 mmol) yielded 246 mg of 5b
(87%). Rf =0.75 (CH2Cl2:CH3OH=10:1); m.p.:=161 °C;
1H NMR (CDCl3, 400 MHz): δ = 2.71 (s, 3H, CH3), 3.42
(s, 3H, SO2CH3), 7.49 (d, J=8.6 Hz, 2H, ArH), 7.73 (s, 1H,
H-5), 8.08 (d, J=8.6 Hz, 2H, ArH) ppm; 13C NMR (CDCl3,
100 MHz): δ = 24.41 (CH3), 39.02 (SO2CH3), 118.12 (C-5),
128.72, 129.39 (ArC), 133.06, 138.42 (ArCq), 164.02 (C-4),
165.94 (C-2), 170.61 (C-6) ppm; IR (KBr): v=3013, 1591,
1575, 1513, 1494, 1444, 1398, 1356, 1324, 1301, 1228,
1137, 1094, 1012, 968, 840, 754 cm−1; HRMS (EI+): m/z
calcd. (C12H11ClN2O2S) [M+] 282.0230, found 282.0224.
4‑(4‑Methoxyphenyl)‑6‑methyl‑2‑(methylsulfanyl)pyrimi‑
dine hydroiodide (4d, C13H15lIN2OS) Reaction of 1.88 g of 4d
(8.1 mmol) in 120 cm3 of CHCl3 with 2.75 g of CH3I yielded
after 2 days 2.65 g of 4d (87%) as yellow solid. Rf = 0.76
(CH2Cl2:MeOH = 10:1); m.p.: 213 °C; 1H NMR (DMSO-
d6, 400 MHz): δ = 2.43 (s, 3H, CH3), 2.57 (s, 3H, SCH3),
3.81 (s, 3H, OCH3), 7.05 (d, J=8.8 Hz, 2H, ArH), 7.66 (s,
1H, H-5), 8.15 (d, J = 8.8 Hz, 2H, ArH) ppm; 13C NMR
(DMSO-d6, 100 MHz): δ = 13.79 (SCH3), 23.17 (CH3),
55.75 (OCH3), 111.19 (C-5), 114.66 (ArC), 127.78 (ArCq),
129.33 (ArC), 162.45 (ArCq), 163.21 (C-4), 166.90 (C-6),
169.85 (C-2) ppm; IR (KBr): v=2698, 1602, 1560, 1399,
1348, 1262, 1212, 1178, 1022, 834 cm−1; HRMS (EI+): m/z
calcd. (C13H14N2OS) [M+-HI] 246.0827, found 246.0812.
2‑(Methanesulfonyl)‑4‑methyl‑6‑(4‑methylphenyl)‑
pyrimidine (5c, C13H14N2O2S) Reaction of 5.61 g of 4c
(15.66 mmol) in 575 cm3 of CH2Cl2 with 11.77 g of 3-chlo-
roperoxybenzoic acid (52.52 mmol) yielded 2.996 g of 5c
(73%). Rf = 0.44 (cyclohexane:ethyl acetate = 1:3); m.p.:
146–147 °C; 1H NMR (CDCl3, 400 MHz): δ = 2.43 (s, 3H,
ArCH3), 2.69 (s, 3H, CH3), 3.42 (s, 3H, SO2CH3), 7.32 (d,
J=8.1 Hz, 2H, ArH), 7.71 (s, 1H, H-5), 8.03 (d, J=8.1 Hz,
2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 21.46
(ArCH3), 24.34 (CH3), 38.99 (SO2CH3), 117.84 (C-5),
127.34, 129.82 (ArC), 131.83, 142.75 (ArCq), 165.11 (C-6),
165.82 (C-2), 170.08 (C-4) ppm; IR (KBr): v=3013, 1587,
1521, 1504, 1444, 1355, 1304, 1138, 966, 828, 746 cm−1;
HRMS (EI +): m/z calcd. (C13H14N2O2S) [M+] 262.0776,
found 262.0766.
Preparation of (methanesulfonyl)
pyrimidines 5a–5d
The methylthio-pyrimidine hydroiodides 4a, 4b, 4c, or 4d
were dissolved in CH2Cl2. The resulting solution was cooled
down to 0 °C and 3-chloroperoxybenzoic acid (77%) was
added slowly with stirring and cooling. The color of the
solution turned to cerise, the ice bath was removed and the
reaction mixture was stirred for 2 h at r.t.. During the reac-
tion the color of the solution turned to violet due to the oxi-
dation of iodide to iodine. The organic layer was washed
once with saturated NaHCO3 solution, once with an aque-
ous Na2S2O3 solution, and fnally with brine. Then it was
dried over anhydrous Na2SO4 and fltered. The solvent was
evaporated in vacuo giving white solids which were recrys-
tallized with a small amount of ethyl acetate giving colorless
needles.
2‑(Methanesulfonyl)‑4‑(4‑methoxyphenyl)‑6‑methylpy‑
rimidine (5d, C13H14N2O3S) Reaction of 2.512 g of 4d
(6.72 mmol) in 250 cm3 of CH2Cl2 with 5.04 g of 3-chlorop-
eroxybenzoic acid (22.49 mmol) yielded 1.32 g of 5d (71%).
1
Rf = 0.75 (CH2Cl2:CH3OH = 10:1); m.p.: 135–136 °C; H
NMR (CDCl3, 400 MHz): δ = 2.66 (s, 3H, CH3), 3.41 (s, 3H,
SO2CH3), 3.88 (s, 3H, OCH3), 7.00 (d, J=8.8 Hz, 2H, ArH),
7.65 (s, 1H, H-5), 8.10 (d, J =8.8 Hz, 2H, ArH) ppm; 13C
NMR (CDCl3, 100 MHz): δ = 24.29 (CH3), 38.96 (SO2CH3),
55.42 (OCH3), 114.40 (ArC), 117.14 (C-5), 126.89 (ArCq),
129.12 (ArC), 162.82 (ArCq), 164.61 (C-4), 165.72 (C-2),
169.75 (C-6) ppm; IR (KBr): v = 2932, 1587, 1524, 1417,
1354, 1298, 1281, 1261, 1223, 1189, 1140, 1021, 840,
750 cm−1; HRMS (EI +): m/z calcd. (C13H14N2O3S) [M+]
278.0725, found 278.0727.
2‑(Methanesulfonyl)‑4‑methyl‑6‑phenylpyrimidine (5a,
C12H12N2O2S) Reaction of 1.124 g of 4a (3.27 mmol) in
120 cm3 of CH2Cl2 with 2.452 g of 3-chloroperoxybenzoic
acid (10.94 mmol) yielded 751 mg of 5a (92%). Rf = 0.75
(CH2Cl2:CH3OH=10:1); m.p.: 176 °C; 1H NMR (CDCl3,
400 MHz): δ = 2.73 (s, 3H, CH3), 3.44 (s, 3H, SO2CH3),
7.52–7.58 (m, 3H, ArH), 7.75 (s, 1H, H-5), 8.14 (d,
J=6.6 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 24.38 (CH3), 39.01 (SO2CH3), 118.31 (C-5), 127.41,
129.09, 132.01 (ArC), 134.63 (ArCq), 165.18 (C-6),
165.90 (C-2), 170.36 (C-4) ppm; IR (KBr): v=3015, 1590,
1515, 1499, 1426, 1353, 1296, 1223, 1141, 974, 965,
883, 793, 765, 751, 697 cm−1; HRMS (EI +): m/z calcd.
(C12H12N2O2S) [M+] 248.0620, found 248.0623.
Preparation of pyrimidin‑2‑amines 6a–6d
The pyrimidin-2-amines were prepared similar to a reported
procedure [20]. Compounds 5a, 5b, 5c, or 5d were sus-
pended in dioxane and concentrated aqueous NH3 was
1 3

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities
added. The reaction mixture was subjected to microwave
irradiation at 120 °C. The solvents were evaporated in vacuo
to dryness. Water was added and the mixture was extracted
5 times with CH2Cl2. The combined organic layers were
washed once with water, dried over anhydrous Na2SO4, and
fltered. The solvent was evaporated in vacuo giving a crys-
talline residue. The crude products were purifed by means
of sublimation at reduced pressure yielding the products as
white needles.
1351, 809, 799 cm−1; HRMS (EI+): m/z calcd. (C12H13N3)
[M+] 199.1109, found 199.1097.
4‑(4‑Methoxyphenyl)‑6‑methylpyrimidin‑2‑amine (6d,
C12H13N3O) Reaction of 213 mg of 5d (0.77 mmol) with
1.27 cm3 of concentrated aqueous NH3 (16.9 mmol) in 4.6
cm3 of dioxane for 3 h yielded 55 mg of 6d (33%). The
melting point (202 °C) corresponded well with the reported
1
one (204 °C) [24]. Rf = 0.74 (CH2Cl2:CH3OH = 9:1); H
NMR (DMSO-d6, 400 MHz): δ = 2.26 (s, 3H, CH3), 3.80
(s, 3H, OCH3), 6.47 (s, 2H, NH2), 6.96 (s, 1H, H-5), 7.01
(d, J = 9.2 Hz, 2H, ArH), 8.01 (d, J = 8.8 Hz, 2H, ArH)
ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 23.90 (CH3),
55.46 (OCH3), 104.56 (C-5), 114.13, 128.39 (ArC), 129.71,
161.25 (ArCq), 163.33 (C-4), 163.79 (C-2), 167.98 (C-6)
ppm; IR (KBr): v = 3310, 3176, 1636, 1608, 1579, 1545,
1514, 1463, 1417, 1382, 1351, 1249, 1233, 1182, 1033,
820 cm−1; HRMS (EI +): m/z calcd. (C12H13N3O) [M+]
215.1059, found 215.1045.
4‑Methyl‑6‑phenylpyrimidin‑2‑amine (6a, C11H11N3) Reac-
tion of 200 mg of 5a (0.81 mmol) with 1.34 cm3 of concen-
trated aqueous NH3 (18 mmol) in 4.8 cm3 of dioxane for 2 h
yielded 66 mg of 6a (44%). The melting point (169–170 °C)
corresponded well with the reported one (169–171 °C) [21].
1
Rf = 0.63 (CH2Cl2:CH3OH = 9:1); H NMR (DMSO-d6,
400 MHz): δ = 2.29 (s, 3H, CH3), 6.58 (s, 2H, NH2), 7.02 (s,
1H, H-5), 7.45–7.47 (m, 3H, ArH), 8.02–8.05 (m, 2H, ArH)
ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 23.91 (CH3),
105.38 (C-5), 126.86, 128.80, 130.43 (ArC), 137.46 (ArCq),
163.75 (C-6), 163.90 (C-2), 168.39 (C-4) ppm; IR (KBr):
v=3323, 3194, 1637, 1601, 1579, 1551, 1464, 1380, 1353,
1227, 770, 708 cm−1; HRMS (EI+): m/z calcd. (C11H11N3)
[M+] 185.0953, found 185.0942.
Preparation of (pyrrolidin‑1‑yl)pyrimidines
7a–7d
The compounds 5a, 5b, 5c, or 5d were dissolved in dry
THF and pyrrolidine was added. The reaction mixture was
refuxed at 85 °C overnight or subjected to microwave irra-
diation. Water was added and the mixture was extracted fve
times with diethyl ether. The combined organic layers were
washed neutral with water, dried over anhydrous Na2SO4,
and fltered. The solvent was evaporated in vacuo giving
pure compounds 7a–7d as white to yellowish needles. For
analytical purposes they were recrystallized giving white
needles.
4‑(4‑Chlorophenyl)‑6‑methylpyrimidin‑2‑amine (6b,
C11H10ClN3) Reaction of 215 mg of 5b (0.76 mmol) with
1.27 cm3 of concentrated aqueous NH3 (17 mmol) in 4.6 cm3
of dioxane for 3 h yielded 50 mg of 6b (30%). The melting
point (198 °C) was similar to the reported one (204 °C) [22].
1
Rf = 0.47 (CH2Cl2:CH3OH = 20:1); H NMR (DMSO-d6,
400 MHz): δ = 2.28 (s, 3H, CH3), 6.62 (s, 2H, NH2), 7.03 (s,
1H, H-5), 7.52 (d, J=8.4 Hz, 2H, ArH), 8.05 (d, J=8.8 Hz,
2H, ArH) ppm; 13C NMR (DMSO-d6, 100 MHz): δ = 23.91
(CH3), 105.27 (C-5), 128.62, 128.86 (ArC), 135.19, 136.26
(ArCq), 162.42 (C-4), 163.86 (C-2), 168.68 (C-6) ppm; IR
(KBr): v=3306, 3162, 1639, 1595, 1572, 1551, 1492, 1463,
1089, 808 cm−1; HRMS (EI +): m/z calcd. (C11H10ClN3)
[M+] 219.0563, found 219.0553.
4‑Methyl‑6‑phenyl‑2‑(pyrrolidin‑1‑yl)pyrimidine (7a,
C15H17N) Method 1: Reaction of 218 mg of 5a (0.88 mmol)
in 45 cm3 of dry THF with 157 mg of pyrrolidine
(2.21 mmol) yielded 200 mg of 7a (95%). Method 2: Reac-
tion of 200 mg of 5a (0.81 mmol) in 4 cm3 of dry THF with
172 mg of pyrrolidine (2.42 mmol) yielded after 1 h micro-
wave irradiation at 100 °C 148 mg of 7a (76%). Rf = 0.84
4‑Methyl‑6‑(4‑methylphenyl)pyrimidin‑2‑amine (6c,
C12H13N3) Reaction of 200 mg of 5c (0.76 mmol) with 1.27
cm3 (16.70 mmol) of concentrated aqueous NH3 in 4.6 cm3
of dioxane for 3 h yielded 100 mg of 6c (66%). The melting
point (148–149 °C) corresponded well with the reported one
(149–150 °C) [22, 22]. Rf =0.54 (CH2Cl2:CH3OH=9:1); 1H
NMR (DMSO-d6, 400 MHz): δ = 2.27 (s, 3H, CH3), 2.33 (s,
3H, ArCH3), 6.53 (s, 2H, NH2), 6.98 (s, 1H, H-5), 7.26 (d,
J=8.1 Hz, 2H, ArH), 7.94 (d, J =8.4 Hz, 2H, ArH) ppm;
13C NMR (DMSO-d6, 100 MHz): δ = 21.10 (ArCH3), 23.89
(CH3), 105.02 (C-5), 126.79, 129.40 (ArC), 134.65, 140.17
(ArCq), 163.67 (C-6), 163.86 (C-2), 168.19 (C-4) ppm; IR
(KBr): v=3361, 3186, 1638, 1576, 1550, 1514, 1462, 1379,
1
(CH2Cl2:CH3OH = 10:1); m.p.: 88 °C (ethyl acetate); H
NMR (CDCl3, 400 MHz): δ = 1.90 (t, J = 6.6 Hz, 4H,
(CH2)2), 2.33 (s, 3H, CH3), 3.60 (br, s, 4H, N(CH2)2), 6.72
(s, 1H, H-5), 7.34–7.36 (m, 3H, ArH), 7.97–7.99 (m, 2H,
ArH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 24.45 (CH3),
25.51 ((CH2)2), 46.63 (N(CH2)2), 104.33 (C-5), 126.93,
128.46, 129.98 (ArC), 138.10 (ArCq), 160.70 (C-2), 163.95
(C-6), 167.69 (C-4) ppm; IR (KBr): v=2971, 2928, 2857,
1587, 1555, 1512, 1482, 1458, 1374, 1336, 1223, 1183,
771, 693 cm−1; HRMS (EI+): m/z calcd. (C15H17N3) [M+]
239.1422, found 239.1421.
1 3

M. Hofelner et al.
4‑(4‑Chlorophenyl)‑6‑methyl‑2‑(pyrrolidin‑1‑yl)pyrimidine
(7b, C15H16ClN3) Reaction of 300 mg of 5b (1.06 mmol) in
5 cm3 of dry THF with 225 mg of pyrrolidine (3.16 mmol)
yielded after 2 h microwave irradiation at 120 °C 87 mg of
7b (30%). Rf =0.85 (CH2Cl2:CH3OH=10:1); m.p.: 87 °C
(MeOH); 1H NMR (CDCl3, 400 MHz): δ = 1.97–2.01 (m,
4H, (CH2)2), 2.41 (s, 3H, CH3), 3.65–3.68 (m, 4H, N(CH2)2),
6.76 (s, 1H, H-5), 7.41 (d, J = 8.4 Hz, 2H, ArH), 8.00 (d,
J=8.8 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 24.49 (CH3), 25.52 ((CH2)2), 46.66 (N(CH2)2), 104.04
(C-5), 128.25, 128.68 (ArC), 136.03, 136.56 (ArCq),
160.62 (C-2), 162.70 (C-4), 167.99 (C-6) ppm; IR (KBr):
v=2866, 1595, 1582, 1552, 1513, 1487, 1459, 1376, 1338,
1223, 1090, 1013, 806 cm−1; HRMS (EI +): m/z calcd.
(C15H16ClN3) [M+] 273.1033, found 273.1036.
Preparation of 2‑(4‑methylpiperazin‑1‑yl)
pyrimidines 8a–8d
The compounds 5a, 5b, 5c, or 5d were dissolved in dry THF
and 1-methylpiperazine was added. The reaction mixture
was refuxed at 100 °C overnight or subjected to microwave
irradiation. Water was added and the mixture was extracted
fve times with diethyl ether. The combined organic lay-
ers were washed neutral with water, dried over anhydrous
Na2SO4 and fltered. The solvent was evaporated in vacuo
giving a resin which was further purifed.
4‑Methyl‑2‑(4‑methylpiperazin‑1‑yl)‑6‑phenylpyrimidine
(8a, C16H20N4) Reaction of 300 mg of 5a (1.21 mmol) in
12 cm3 of dry THF with 726 mg of 1-methylpiperazine
(7.24 mmol) yielded a yellow resin which was purifed by
means of CC (CH2Cl2:CH3OH = 40:1, Alox neutral) giv-
ing 245 mg of 8a (75%) as a yellow oil which crystallized
upon cooling. Rf =0.62 (CH2Cl2:CH3OH=40:1, Alox neu-
tral); m.p.: 65 °C; 1H NMR (CDCl3, 400 MHz):δ = 2.36 (s,
3H, NCH3), 2.40 (s, 3H, CH3), 2.50–2.53 (m, 4H, H-3′),
3.96–3.98 (m, 4H, H-2′), 6.84 (s, 1H, H-5), 7.44–7.45 (m,
3H, ArH), 8.02–8.04 (m, 2H, ArH) ppm; 13C NMR (CDCl3,
100 MHz): δ = 24.50 (CH3), 43.62 (C-2′), 46.21 (NCH3),
55.04 (C-3′), 105.32 (C-5), 126.93, 128.51, 130.11 (ArC),
137.93 (ArCq), 162.00 (C-2), 164.00 (C-6), 168.06 (C-4)
ppm; IR (KBr): v = 2924, 2794, 1558, 1493, 1443, 1368,
1345, 1300, 1272, 1223, 1188, 1173, 1073, 1007, 994, 890,
815, 764, 687 cm−1; HRMS (EI+): m/z calcd. (C16H20N4)
[M+] 268.1688, found 268.1693.
4‑Methyl‑6‑(4‑methylphenyl)‑2‑(pyrrolidin‑1‑yl)pyrimidine
(7c, C16H19N3) Reaction of 400 mg of 5c (1.52 mmol) in 15
cm3 of dry THF with 651 mg of pyrrolidine (9.15 mmol)
yielded 371 mg of 7c (96%). Rf =0.60 (cyclohexane:ethyl
acetate=1:3); m.p.: 76 °C (ethyl acetate); 1H NMR (CDCl3,
400 MHz): δ = 1.96–1.99 (m, 4H, (CH2)2), 2.38 (s, 3H,
ArCH3), 2.39 (s, 3H, CH3), 3.65–3.68 (m, 4H, N(CH2)2),
6.77 (s, 1H, H-5), 7.24 (d, J = 8.1 Hz, 2H, ArH), 7.96 (d,
J=8.1 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 21.34 (ArCH3), 24.53 (CH3), 25.53 ((CH2)2), 46.56
(N(CH2)2), 104.03 (C-5), 126.82, 129.18 (ArC), 135.36,
140.08 (ArCq), 160.88 (C-2), 163.80 (C-6), 167.66 (C-4)
ppm; IR (KBr): v = 2944, 2870, 1553, 1508, 1482, 1459,
1375, 1337, 1220, 1182, 1111, 803 cm−1; HRMS (EI+): m/z
calcd. (C16H19N3) [M+] 253.1579, found 253.1575.
4‑(4‑Chlorophenyl)‑6‑methyl‑2‑(4‑methylpiperazin‑1‑yl)‑
pyrimidine (8b, C16H19ClN4) Reaction of 375 mg of 5b
(1.33 mmol) in 5 cm3 of dry THF with 787 mg of 1-methyl-
piperazine (7.86 mmol) yielded after 5 h microwave irradia-
tion at 120 °C a yellow resin. It was purifed by means of CC
(CH2Cl2: CH3OH=10:1) giving 235 mg of 8b (58%) as a
white amorphous solid. Rf =0.43 (CH2Cl2:CH3OH=10:1);
1H NMR (DMSO-d6, 400 MHz):δ = 2.20 (s, 3H, NCH3),
2.33 (s, 3H, CH3), 2.34–2.36 (m, 4H, H-3′), 3.75–3.82 (m,
4H, H-2′), 7.11 (s, 1H, H-5), 7.53 (d, J=8.4 Hz, 2H, ArH),
8.11 (d, J=8.4 Hz, 2H, ArH) ppm; 13C NMR (DMSO-d6,
100 MHz):δ = 24.36 (CH3), 43.46 (C-2′), 46.06 (NCH3),
54.67 (C-3′), 105.06 (C-5), 128.71, 128.93 (ArC), 135.41,
136.11 (ArCq), 161.59 (C-2), 161.91 (C-4), 168.61 (C-6)
ppm; IR (KBr): v = 2930, 2795, 1585, 1556, 1508, 1491,
1447, 1371, 1345, 1303, 1283, 1269, 1093, 1006, 995,
804 cm−1; HRMS (EI +): m/z calcd. (C16H19ClN4) [M+]
302.1298, found 302.1310.
4‑(4‑Methoxyphenyl)‑6‑methyl‑2‑(pyrrolidin‑1‑yl)pyrimidine
(7d, C16H19N3O) Reaction of 300 mg of 5d (1.08 mmol) in
10 cm3 of dry THF with 460 mg of pyrrolidine (6.47 mmol)
yielded an oil which was purifed by means of CC with
cyclohexane:ethyl acetate (1:1) as eluent giving 276 mg
of 7d (95%). Rf = 0.48 (cyclohexane:ethyl acetate = 1:1);
1
m.p.: 88 °C (ethyl acetate); H NMR (CDCl3, 400 MHz):
δ = 1.96–1.99 (m, 4H, (CH2)2), 2.39 (s, 3H, CH3), 3.65–
3.68 (m, 4H, N(CH2)2), 3.84 (s, 3H, OCH3), 6.74 (s, 1H,
H-5), 6.95 (d, J=8.4 Hz, 2H, ArH), 8.03 (d, J=8.8 Hz, 2H,
ArH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 24.53 (CH3),
25.52 ((CH2)2), 46.54 (N(CH2)2), 55.26 (OCH3), 103.54
(C-5), 113.76, 128.32 (ArC), 130.62 (ArCq), 160.83 (C-2),
161.21 (ArCq), 163.32 (C-4), 167.52 (C-6) ppm; IR (KBr):
v=2955, 2875, 1607, 1587, 1553, 1512, 1483, 1458, 1379,
1351, 1338, 1249, 1173, 1109, 1033, 839, 808, 789 cm−1;
HRMS (EI +): m/z calcd. (C16H19N3O) [M+] 269.1528,
found 269.1528.
4‑Methyl‑6‑(4‑methylphenyl)‑2‑(4‑methylpiperazin‑1‑yl)‑
pyrimidine (8c, C17H22N4) Reaction of 400 mg of 5c
1 3

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities
(1.52 mmol) in 3 cm3 of dry THF with 916 mg of 1-meth-
ylpiperazine (9.14 mmol) yielded after 7 h microwave irra-
diation at 120 °C a resin. It was purifed by means of CC
(CH2Cl2:CH3OH = 10:1) giving 334 mg of 8c (78%) as
an orange oil which crystallized upon cooling. Rf = 0.43
2-amino-5-(diethylamino)pentane (4.84 mmol) yielded
after 12 h microwave irradiation at 120 °C a residue which
was purifed by means of CC (CH2Cl2:CH3OH=40:1, Alox
neutral) giving 122 mg of 9a (46%) as yellow oil. Rf =0.24
(CH2Cl2: CH3OH=40:1, Alox neutral); 1H NMR (CDCl3,
400 MHz): δ = 1.03 (t, J = 7.1 Hz, 6H, H-2′′), 1.26 (d,
J=6.5 Hz, 3H, H-1′), 1.54–1.65 (m, 4H, H-3′, H-4′), 2.38
(s, 3H, CH3), 2.50–2.55 (m, 2H, H-5′), 2.56 (q, J=7.1 Hz,
4H, H-1′′), 4.23–4.28 (m, 1H, H-2′), 4.96 (d, J=8.3 Hz, 1H,
NH), 6.84 (s, 1H, H-5), 7.44–7.46 (m, 3H, ArH), 8.01–8.02
(m, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 11.28
(C-2′′), 21.12 (C-1′), 23.13 (C-4′), 24.32 (CH3), 35.11
(C-3′), 46.48 (C-2′), 46.71 (C-1′′), 52.71 (C-5′), 105.75
(C-5), 126.92, 128.55, 130.13 (ArC), 137.85 (ArCq), 162.27
(C-2), 164.44 (C-6), 168.25 (C-4) ppm; IR (KBr): v=3268,
2965, 1574, 1551, 1495, 1458, 1373, 1346, 1203, 1069,
767, 693 cm−1; HRMS (EI+): m/z calcd. (C20H30N4) [M+]
326.2470, found 326.2471.
1
(CH2Cl2:CH3OH = 10:1); m.p.: 73 °C; H NMR (CDCl3,
400 MHz): δ = 2.34 (s, 3H, NCH3), 2.38 (s, 3H, CH3), 2.39
(s, 3H, ArCH3), 2.48–2.50 (m, 4H, H-3′), 3.94–3.96 (m, 4H,
H-2′), 6.80 (s, 1H, H-5), 7.24 (d, J=8.1 Hz, 2H, ArH), 7.93
(d, J=8.1 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 21.33 (ArCH3), 24.46 (CH3), 43.67 (C-2′), 46.25
(NCH3), 55.06 (C-3′), 104.94 (C-5), 126.81, 129.20 (ArC),
135.10, 140.25 (ArCq), 161.99 (C-2), 163.91 (C-6), 167.82
(C-4) ppm; IR (KBr): v = 2930, 2793, 1585, 1570, 1556,
1504, 1447, 1371, 1345, 1300, 1285, 1272, 1008, 804 cm−1;
HRMS (EI+): m/z calcd. (C17H22N4) [M+] 282.1844, found
282.1850.
4‑(4‑Methoxyphenyl)‑6‑methyl‑2‑(4‑methylpiperazin‑1‑yl)‑
pyrimidine (8d, C17H22N4O) Reaction of 250 mg of 5d
(0.90 mmol) in 9 cm3 of dry THF with 540 mg of 1-meth-
ylpiperazine (5.39 mmol) yielded after 3 days refuxing at
100 °C a residue which was crystallized from ethyl ace-
tate giving 141 mg of 8d (53%) as white needles. Rf =0.43
4‑(4‑Chlorophenyl)‑N‑[5‑(diethylamino)pentan‑2‑yl]‑6‑meth‑
ylpyrimidin‑2‑amine (9b, C20H29ClN4) Reaction of 246 mg
of 5b (0.87 mmol) in 5 cm3 of dry THF with 826 mg of
2-amino-5-(diethylamino)pentane (5.22 mmol) yielded
after 7.5 h microwave irradiation at 120 °C a residue which
was purifed by means of CC (CH2Cl2:CH3OH=40:1, Alox
neutral) giving 196 mg of 9b (62%) as yellow oil. Rf =0.70
1
(CH2Cl2:CH3OH = 10:1); m.p.: 93 °C; H NMR (CDCl3,
400 MHz): δ = 2.34 (s, 3H, NCH3), 2.38 (s, 3H, CH3),
2.48–2.50 (m, 4H, H-3′), 3.84 (s, 3H, OCH3), 3.95 (br, s, 4H,
H-2′), 6.77 (s, 1H, H-5), 6.95 (d, J=8.4 Hz, 2H, ArH), 8.01
(d, J=8.4 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 24.45 (CH3), 43.67 (C-2′), 46.25 (NCH3), 55.06 (C-3′),
55.24 (OCH3), 104.46 (C-5), 113.78, 128.33 (ArC), 130.34,
161.30 (ArCq), 161.95 (C-2), 163.44 (C-4), 167.67 (C-6)
ppm; IR (KBr): v2936, 2788, 1610, 1586, 1570, 1557, 1514,
1492, 1459, 1350, 1301, 1286, 1270, 1258, 1172, 1027,
1009, 813 cm−1; HRMS (EI +): m/z calcd. (C17H22N4O)
[M+] 298.1794, found 298.1793.
1
(CH2Cl2:CH3OH = 10:1); H NMR (CDCl3, 400 MHz):
δ = 1.01 (t, J=7.2 Hz, 6H, H-2′′), 1.25 (d, J=6.5 Hz, 3H,
H-1′), 1.53–1.62 (m, 4H, H-3′, H-4′), 2.37 (s, 3H, CH3),
2.45–2.48 (m, 2H, H-5′), 2.52 (q, J = 7.2 Hz, 4H, H-1′′),
4.20–4.25 (m, 1H, H-2′), 5.02 (d, J = 8.3 Hz, 1H, NH),
6.79 (s, 1H, H-5), 7.41 (d, J = 8.5 Hz, 2H, ArH), 7.96 (d,
J=8.4 Hz, 2H, ArH) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 11.44 (C-2′′), 21.03 (C-1′), 23.38 (C-4′), 24.29 (CH3),
35.08 (C-3′), 46.53 (C-2′), 46.70 (C-1′′), 52.78 (C-5′),
105.36 (C-5), 128.19, 128.71 (ArC), 136.12, 136.27 (ArCq),
162.21 (C-2), 163.11 (C-4), 168.45 (C-6) ppm; IR (KBr):
v=3268, 2965, 2798, 1573, 1549, 1491, 1456, 1402, 1374,
1342, 1091, 1013, 808 cm−1; HRMS (EI +): m/z calcd.
(C20H29ClN4) [M+] 360.2081, found 360.2103.
Preparation of N‑[5‑(diethylamino)
pentan‑2‑yl]pyrimidin‑2‑amines 9a–9d
The compounds 5a, 5b, 5c, or 5d were dissolved in dry THF
and 2-amino-5-(diethylamino)pentane was added. The reac-
tion mixture was subjected to microwave irradiation. Water
was added and the mixture was extracted fve times with
diethyl ether. The combined organic layers were washed neu-
tral with water, dried over anhydrous Na2SO4 and fltered.
The solvent was evaporated in vacuo giving residues which
were further purifed.
N‑[5‑(Diethylamino)pentan‑2‑yl]‑4‑methyl‑6‑(4‑meth‑
ylphenyl)pyrimidin‑2‑amine (9c, C21H32N4) Reaction of
300 mg of 5c (1.14 mmol) in 3 cm3 of dry THF with 1.09 g
of 2-amino-5-(diethylamino)pentane (6.86 mmol) yielded
after 13 h microwave irradiation at 120 °C a residue which
was purifed by means of CC (CH2Cl2:CH3OH=40:1, Alox
neutral) giving 313 mg of 9c (81%) as orange oil. Rf =0.23
1
(CH2Cl2:CH3OH = 40:1, Alox neutral); H NMR (CDCl3,
400 MHz):δ = 1.00 (t, J = 7.1 Hz, 6H, H-2′′), 1.24 (d,
J=6.6 Hz, 3H, H-1′), 1.51–1.60 (m, 4H, H-3′, H-4′), 2.36
(s, 3H, CH3), 2.40 (s, 3H, ArCH3), 2.43–2.46 (m, 2H, H-5′),
2.51 (q, J = 7.1 Hz, 4H, H-1′′), 4.21–4.24 (m, 1H, H-2′),
N‑[5‑(Diethylamino)pentan‑2‑yl]‑4‑methyl‑6‑phenylpy‑
rimidin‑2‑amine (9a, C20H30N4) Reaction of 200 mg
of 5a (0.81 mmol) in 4 cm3 of dry THF with 766 mg of
1 3

M. Hofelner et al.
4.97 (d, J = 8.1 Hz, 1H, NH), 6.80 (s, 1H, H-5), 7.24 (d,
J=8.1 Hz, 2H, ArH), 7.92 (d, J =8.1 Hz, 2H, ArH) ppm;
13C NMR (CDCl3, 100 MHz): δ = 11.56 (C-2′′), 21.02
(C-1′), 21.33 (ArCH3), 23.45 (C-4′), 24.24 (CH3), 35.14
(C-3′), 46.50 (C-2′), 46.71 (C-1′′), 52.84 (C-5′), 105.30
(C-5), 126.79, 129.21 (ArC), 135.01, 140.25 (ArCq), 162.21
(C-2), 164.32 (C-6), 167.96 (C-4) ppm; IR (KBr): v=2965,
1574, 1549, 1510, 1454, 1374, 1345, 1182, 806 cm−1;
HRMS (EI+): m/z calcd. (C21H32N4) [M+] 340.2627, found
340.2636.
of N-(2-aminoethyl)-7-chloroquinolin-4-amine (6.44 mmol)
yielded after 7 h microwave irradiation at 120 °C and extrac-
tion with CH2Cl2 a residue. This was purifed using CC
(CH2Cl2:CH3OH = 40:1, Alox neutral) giving 285 mg of
10a (45%) as white foam. Rf =0.36 (CH2Cl2:CH3OH=40:1,
Alox neutral); 1H NMR (DMSO-d6, 400 MHz): δ = 2.33 (br,
s, 3H, CH3), 3.46–3.51 (m, 2H, H-3′), 3.58–3.72 (m, 2H,
H-2′), 6.62–6.88 (m, 1H, ArH), 7.07 (s, 1H, H-5), 7.29–7.50
(m, 6H, 2NH, ArH), 7.77 (s, 1H, ArH), 8.04–8.24 (m, 3H,
ArH), 8.28–8.42 (m, 1H, ArH) ppm; 13C NMR (DMSO-
d6, 100 MHz): δ = 24.04 (CH3), 39.07 (C-2′), 42.45 (C-3′),
98.96 (ArC), 105.61 (C-5), 117.60 (ArCq), 124.10, 124.20,
126.96, 127.73, 128.90, 130.60 (ArC), 133.54, 137.54,
149.29, 150.33 (ArCq), 152.07 (ArC), 162.75 (C-2), 163.53
(C-6), 168.55 (C-4) ppm; IR (KBr): v=3269, 2953, 1582,
1556, 1429, 1374, 1348, 1299, 1231, 1140, 769 cm−1;
HRMS (EI +): m/z calcd. (C22H20ClN5) [M+] 389.1407,
found 389.1404.
N‑[5‑(Diethylamino)pentan‑2‑yl]‑4‑(4‑methoxyphenyl)‑
6‑methylpyrimidin‑2‑amine (9d, C21H32N4O) Reaction of
300 mg of 5d (1.08 mmol) in 3 cm3 of dry THF with 1.02 g
of 2-amino-5-(diethylamino)pentane (6.47 mmol) yielded
after 6 h microwave irradiation at 120 °C a residue which
was purified by means of CC (CH2Cl2:CH3OH = 40:1,
Alox neutral). The fractions containing the product were
combined, solvents evaporated, and the residue was sub-
jected again to CC (CH2Cl2:CH3OH = 60:1, Alox neu-
tral) giving 250 mg of 9d (65%) as yellow oil. Rf = 0.35
7‑Chloro‑N‑[2‑[[4‑(4‑chlorophenyl)‑6‑methylpyrimidin‑2‑yl]‑
amino]ethyl]quinolin‑4‑amine (10b, C22H19Cl2N5) Reac-
tion of 226 mg of 5b (0.8 mmol) in 5 cm3 of dry THF with
714 mg of N-(2-aminoethyl)-7-chloroquinolin-4-amine
(3.22 mmol) yielded after 5.5 h microwave irradiation at
120 °C and extraction with tert-butylmethyl ether a resi-
due. This was purifed by CC (CH2Cl2:CH3OH=10:1, Alox
neutral) giving 62 mg of 10b (18%) as a white-yellow amor-
phous solid. Rf = 0.26 (CH2Cl2:CH3OH = 10:1, Alox neu-
tral); 1H NMR (DMSO-d6, 400 MHz): δ = 2.32 (br, s, 3H,
CH3), 3.47–3.50 (m, 2H, H-3′), 3.56–3.70 (m, 2H, H-2′),
6.64–6.80 (m, 1H, ArH), 7.09 (s, 1H, H-5), 7.33–7-56 (m,
5H, 2NH, ArH), 7.76 (s, 1H, ArH), 8.08 (d, J=8.3 Hz, 2H,
ArH), 8.14 (br, s, 1H, ArH), 8.34–8.38 (m, 1H, ArH) ppm;
13C NMR (DMSO-d6, 100 MHz): δ = 23.94 (CH3), 38.81
(C-2′), 42.01 (C-3′), 98.98 (ArC), 105.47 (C-5), 117.63
(ArCq), 124.12, 127.72, 128.70, 128.93 (ArC), 133.54,
135.32, 149.29, 150.33 (ArCq), 152.07 (ArC), 162.24 (C-4),
162.70 (C-2), 168.63 (C-6) ppm; IR (KBr): v=3433, 3268,
2927, 1577, 1556, 1492, 1456, 1371, 1342, 1330, 1239,
1140, 1092, 1013, 808 cm−1; HRMS (EI +): m/z calcd.
(C22H19Cl2N5) [M+] 423.1017, found 423.1056.
1
(CH2Cl2:CH3OH = 60:1, Alox neutral); H NMR (CDCl3,
400 MHz):δ = 1.00 (t, J = 7.3 Hz, 6H, H-2′′), 1.24 (d,
J=6.6 Hz, 3H, H-1′), 1.50–1.60 (m, 4H, H-3′, H-4′), 2.35
(s, 3H, CH3), 2.43–2.46 (m, 2H, H-5′), 2.51 (q, J=7.3 Hz,
4H, H-1′′), 3.85 (s, 3H, OCH3), 4.21–4.24 (m, 1H, H-2′),
4.96 (d, J = 8.1 Hz, 1H, NH), 6.77 (s, 1H, H-5), 6.96 (d,
J=8.8 Hz, 2H, ArH), 8.00 (d, J=8.8 Hz, 2H, ArH) ppm; 13C
NMR (CDCl3, 100 MHz): δ = 11.56 (C-2′′), 21.02 (C-1′),
23.46 (C-4′), 24.24 (CH3), 35.15 (C-3′), 46.49 (C-2′), 46.71
(C-1′′), 52.85 (C-5′), 55.26 (OCH3), 104.80 (C-5), 113.80,
128.33 (ArC), 130.25, 161.30 (ArCq), 162.16 (C-2), 163.85
(C-4), 167.81 (C-6) ppm; IR (KBr): v=2964, 1575, 1547,
1510, 1453, 1374, 1348, 1305, 1294, 1250, 1171, 1033,
810 cm−1; HRMS (EI +): m/z calcd. (C21H32N4O) [M+]
356.2576, found 356.2585.
Preparation of N‑[2‑[(pyrimidin‑2‑yl)amino]‑
ethyl]‑7‑chloroquinolin‑4‑amines 10a–10d
The compounds 5a, 5b, 5c, or 5d were dissolved in dry THF
and N-(2-aminoethyl)-7-chloroquinolin-4-amine was added.
The reaction mixture was subjected to microwave irradia-
tion. The solution was transferred into a separatory funnel
and water was added. The mixture was extracted fves times.
The combined organic layers were washed with water, dried
over anhydrous Na2SO4, and fltered. The solvent was evapo-
rated in vacuo giving a residue which was further purifed.
7‑Chloro‑N‑[2‑[[4‑methyl‑6‑(4‑methylphenyl)pyrimidin‑2‑yl]‑
amino]ethyl]quinolin‑4‑amine (10c, C23H22ClN5) Reaction
of 200 mg of 5c (0.76 mmol) in 4 cm3 of dry THF with
676 mg of N-(2-aminoethyl)-7-chloroquinolin-4-amine
(3.05 mmol) yielded after 7 h microwave irradiation at
120 °C and extraction with CH2Cl2 a residue. This was
purifed by CC (CH2Cl2:CH3OH=40:1, Alox neutral) giv-
ing 133 mg of 10c (43%) as an of-white amorphous solid.
Rf =0.27 (CH2Cl2:CH3OH=40:1, Alox neutral); 1H NMR
(DMSO-d6, 400 MHz): δ = 2.31 (br, s, 3H, CH3), 2.36 (s,
3H, ArCH3), 3.47–3.50 (m, 2H, H-3′), 3.54–3.71 (m, 2H,
7‑Chloro‑N‑[2‑[(4‑methyl‑6‑phenylpyrimidin‑2‑yl)amino]‑
ethyl]quinolin‑4‑amine (10a, C22H20ClN5) Reaction of
400 mg of 5a (1.61 mmol) in 8 cm3 of dry THF with 1.43 g
1 3

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities
provide a link to the Creative Commons licence, and indicate if changes
H-2′), 6.59–6.88 (m, 1H, ArH), 7.04 (s, 1H, H-5), 7.25–
7.31 (m, 4H, ArH, NH), 7.45 (t, J=4.9 Hz, 1H, NH), 7.77
(br, s, 1H, ArH), 7.97–7.99 (m, 2H, ArH), 8.13 (br, s, 1H,
ArH), 8.30–8.45 (m, 1H, ArH) ppm; 13C NMR (DMSO-
d6, 100 MHz): δ = 21.15 (ArCH3), 24.06 (CH3), 39.25
(C-2′), 42.49 (C-3′), 98.95 (ArC), 105.24 (C-5), 117.60
(ArCq), 124.11, 124.20, 126.89, 127.73, 129.48 (ArC),
133.54, 134.72, 140.39, 149.28, 150.34 (ArCq), 152.06
(ArC), 162.70 (C-2), 163.45 (C-6), 168.14 (C-4) ppm; IR
(KBr): v=3264, 2924, 1582, 1513, 1447, 1431, 1369, 1347,
1330, 1239, 1140, 810, 802 cm−1; HRMS (EI+): m/z calcd.
(C23H22ClN5) [M+] 403.1564, found 403.1579.
were made. The images or other third party material in this article are
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