Synthesis and single crystal structures of substituted-1,3-selenazol-2-amines

Article abstract of DOI:10.3390/molecules22010046

The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3- selenazol-2-amines is reported. The efficient preparation of these compounds was carried out by two-component cyclization of the selenoureas with equimolar amounts of α-haloketones. The selenoureas were obtained from the reaction of Woollins' reagent with cyanamides, followed by hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.

Full text of DOI:10.3390/molecules22010046

molecules
Article
Synthesis and Single Crystal Structures of
Substituted-1,3-Selenazol-2-amines †
Guoxiong Hua, Junyi Du, Alexandra M. Z. Slawin and J. Derek Woollins *
EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK;
gh15@st-andrews.ac.uk (G.H.); liangfengzhiyi@163.com (J.D.); amzs@st-andrews.ac.uk (A.M.Z.S.)
* Correspondence: jdw3@st-andrews.ac.uk; Tel./Fax: +44-1334-463-861
† Dedication: This paper is dedicated to Prof. Eva Marie Hey-Hawkins on the occasion of her 60th birthday.
Academic Editors: Claudio Santi and Luana Bagnoli
Received: 15 December 2016; Accepted: 26 December 2016; Published: 29 December 2016
Abstract: The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3-
selenazol-2-amines is reported. The efficient preparation of these compounds was carried out
by two-component cyclization of the selenoureas with equimolar amounts of
α-haloketones.
The selenoureas were obtained from the reaction of Woollins’ reagent with cyanamides, followed by
hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR
(1H, 13C, 77Se) spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.
Keywords: cyanamides; haloketones; selenazol-2-amines; selenoureas; Woollins’ reagent
1. Introduction
Selenazoles have been extensively described as useful synthetic tools [
significant antibiotic [ ] and cancerostatic [ ] and superoxide anion scavenging activity [
reports have appeared on the synthesis of selenazoles and thiazoles, including both solid phase [
solution phase synthesis [10 12]. Narender et al. reported the synthesis of selenazoles/thiazoles
by the condensation of phenacylbromides/tosylates with selenourea/thiourea/thiobenzamide
employing -cyclodextrin as a catalyst [13 14]. Recently Varma and co-workers synthesized diaryl
thiazoles from various -tosyloxy ketones in water [15]. Several protocols are also described
1–
4
] with biologically
]. A few
] and
5
6,
7
8
9
–
β
,
α
for the synthesis of thiazoles and selenazoles using promoters or catalysts in different organic
solvents. However, development of novel environmentally benign approaches for the synthesis
of selenazoles/thiazoles is highly desirable. The first ever tandem one-pot synthetic protocol for the
synthesis of thiazoles/selenazoles from alkynes via the formation of 2,2-dibromo-1-phenylethanone
has been reported. The reaction is catalyzed by β-cyclodextrin in aqueous medium and resulted
in good yields [16]. A limitation to this route is the unavailability of the starting material primary
selenamides for the preparation of the selenazoles. Many synthetic strategies to primary selenoamides
have been documented, for example, by the reaction of nitrile with H2Se or NaSeH (generated
in situ from NaBH4/Se) [17] or Se/CO [18
monoselenophosphate [23]. In addition, although some alternative selenating reagents such as
Al2Se3 24], (Me3Si)2Se [25] and 4-methylselenobenzoate [26] have also been applied in these
–21] or P2Se5/H2O [22] and or tris(trimethylsilyl)
[
preparations, almost of these methods required prolonged reaction times, high temperature, and
inconvenient reaction conditions or could not be reproduced [22]. We have previously reported
a highly efficient approach for the preparation of a series of primary arylselenoamides from the
reaction of arylnitriles with 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [PhP(Se)(
(Woollins’ reagent) [27 35], followed by treatment of water [36]. By means of this privileged method,
selenoureas might be prepared in excellent yields. Herein, we report a very facile route to prepare
µ-Se)]2
–
Molecules 2017, 22, 46; doi:10.3390/molecules22010046
www.mdpi.com/journal/molecules

Molecules 2017, 22, 46
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a series of novel 4-substituted-1,3-selenazol-2-amines and single crystal X-ray structural profiles of
seven of the products.
2. Results and Discussion
Cyanamides
the reaction of cyanogen bromide with primary or secondary amines in dry methanol in the presence
of excess of anhydrous CH3COONa at room temperature [37]. Two selenoureas and were obtained
in the yields of 87% and 90%, respectively, by reaction of Woollins’s reagent with the corresponding
cyanamides and , followed by post-treatment with water [38]. As shown in Scheme 1 and Table 1,
cyclization of selenoureas and with an equivalent of the corresponding -haloketones in refluxing
ethanol solution gave a series of five-membered ring 4-substituted-1,3-selenazol-2-amines 15 in
excellent yields. The scope of the reaction was expanded by the reaction of various selenoureas with
phenylacetylene substrates and a variety of -haloketones. In these reactions, substituents on the
1 and 2 were prepared in almost quantitative yields by the literature method from
3
4
1
2
3
4
α
5
–
α
selenoureas did not have significant effect on the product yields. It is also interesting noting that
electron-rich aryl rings allowed for cyclization reactions in yields comparable to electron-deficient
aromatic moieties; and the steric hindrance was rarely permitted since the presence of CH3O, CH3, Cl,
Br and NO2 groups in the 4-aryl ring had minimal to no effect on reaction yields.
Scheme 1. Synthesis of 4-substituted-1,3-selenazol-2-amines 5–15 (X, R and Ar groups defined
in Table 1).
Table 1. Definition of the X, R and Ar Groups, Yields and 77Se-NMR Data for Compounds 5–15.
Compound
X
R
Ar
Yield (%)
77Se-NMR (δ, ppm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
-
-
-
-
CH3
C2H5O(O)C
CH3
C2H5O(O)C
CH3
-
-
-
99
99
87
90
92
96
97
98
93
90
91
95
96
96
95
-
-
607.7
382.1
575.3
571.1
567.1
568.1
590.1
572.7
578.9
577.8
679.9
684.2
675.7
-
Cl
Br
Br
Br
Br
Br
Cl
Br
Cl
Br
Br
C6H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
4-ClC6H4
4-MeOC6H4
4-MeC6H4
4-NO2C6H4
2,5-di-MeOC6H3
2,4-di-ClC6H3
4-BrC6H4
C6H5
C2H5O(O)C
C2H5O(O)C
C2H5O(O)C
4-ClC6H4
4-MeOC6H4
The 4-substituted-1,3-selenazol-2-amines 5–15 are stable to air or moisture for months without
any signs of degradation occurring. Characterization of 4-substituted-1,3-selenazol-2-amines
5
–
15
1
was performed by means of H-, 13C-, and 77Se-NMR, IR spectroscopy and mass spectrometry in

Molecules 2017, 22, 46
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conjunction with single crystal X-ray crystallography of seven of the compounds. All new compounds
show the anticipated [M + H]+ peaks in their mass spectra, as well as satisfactory accurate mass
measurements and appropriate isotopic distributions. The IR spectra show very strong bands ranging
from 1554 to 1561 cm−1 for 4-substituted-1,3-selenazol-2-amines
4-substituted-1,3-selenazol-2-amines 13 15, attributed to the
bands in the range 699 to 705 cm−1 being characteristic of the
5
–
12 and 1513 to 1517 cm−1 for
(N=C) vibration, accompanied by intense
(C-Se) [39]. The CH3 group replaced
and 13 15 for the (N=C) into
–
ν
ν
by C2H5O(O)C group in amine N atom makes IR spectra of
2,
4
–
ν
1
higher frequency (ca. 40 cm−1). Furthermore, the H-NMR spectra exhibit the expected peaks
including sharp singlet signals between 7.44 and 7.90 ppm assigned to the 1,3-selenazole rings.
The 13C-NMR spectra have three signals typical for the 1,3-selenazole rings along with the expected
signals from the aromatic carbon backbones (see Supplementary Materials). The 77Se-NMR spectra of
all compounds
of the related 2-dialkylamino-1,3-selenazoles (528.9–575.9 ppm) [40
significantly lower than that in 2,4-dialkyl- or 2,4-diaryl-1,3-selenazoles (657.8–767.1 ppm) [45
5
–
15 display singlet signals in the range 567.1–684.2 ppm, comparable to the signals
44]; however, these values are
47
–
–
]
and 5-aminoselenazoles (629.0–707.0 ppm) [48]. The results indicated the high influence by the
basic skeletons of selenazoles and the substituents close to the selenium atom [49]. It is worth
noting that 4-substituted-1,3-selenazol-2-amines 13–15 bearing the electron-withdrawing substituted
C2H5O(O)C group on the amine N atom center have much higher 77Se-NMR chemical shifts than
4-substituted-1,3-selenazol-2-amines
amine N atom center.
5–12 bearing the electron-donating substituted CH3 group on the
The formation of 4-substituted-1,3-selenazol-2-amines
reaction mechanism depicted in Scheme 1. The intermediate A, an addition product of selenoureas
or and -haloketones, undergoes a further cyclization reaction resulting in another intermediate B,
which subsequently eliminates one molecule of H2O affording compounds 5–15.
Similarly, treating selenourea with an equivalent of 2-bromo-1,3-diphenylpropane-1,3-dione
5–15 can be explained considering the
3
4
α
3
produced the corresponding 4-phenyl-1,3-selenazol-5-yl)(phenyl)methanone 16 in excellent yield
(93%) as shown in Scheme 2. Compound 16 is a greyish yellow paste, soluble in common organic
solvents. The anticipated [M + H]+ peak was observed in its mass spectra with satisfactory accurate
1
mass measurement. No H-NMR signal was observed for the 1,3-selenazole ring except for the
expected signals for the presence of phenyl rings. Not surprisingly, the 77Se-NMR spectrum comprises
an expected sharp singlet at 609.7 ppm.
Scheme 2. Synthesis of 4-phenyl-1,3-selenazol-5-yl)(phenyl)methanone 16.
Crystals of compounds
grown by diffusion of a dichloromethane solution of the compound into hexane at room temperature in
each case. The absolute structures of compounds 12 14 and 16 were determined using X-ray
diffraction analysis as shown in Figure 1. Crystal data and structure refinement for compounds
12 14 and 16 are summarized in Tables 2 and 3. Selected bond lengths and angles are listed in Table 4.
5, 7, 8, 9, 12, 14 and 16 suitable for X-ray crystallographic analysis were
5
,
7,
8
,
9,
,
5, 7, 8,
9
,
,
All structures except 16 have a single molecule of the compound in the asymmetric unit and adopt
very similar conformation; 16, contains two independent molecules. In all cases, the newly formed
1,3-selenazole ring is not complete planar, and the mean plane of the newly formed five-membered
ring is not coplanar with the adjacent aryl rings, with the dihedral angles of 21.61◦ in
5
, 17.98◦ in
, 21.59◦ in 12, 18.99◦ in 14 and 47.14 [44.79]◦ in 16. Two aryl rings (one is from
the C6H5CH2CH2 group, another is the phenyl aryl ring attaching to the azole ring) are not parallel,
7,
22.78◦ in , 8.04◦ in
8 9

Molecules 2017, 22, 46
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with an angle 19.84◦ in
5
, 6.15◦ in
7
, 21.07◦ in
8
, 6.43◦ in
9
, 19.54◦ in 12, 49.91◦ in 14 and 44.39 [34.21]◦
in 16, the larger angles attribute to the effect of big substituted group [C2H5COC(O)] on N6 atom in 14
and an excess group [PhC(O)] on azole ring in 16.
5
7
8
9
Figure 1. Cont.

Molecules 2017, 22, 46
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12
14
16
Figure 1. Single crystal X-ray structures of compound 5, 7, 8, 9, 12, 14 and 16.

Molecules 2017, 22, 46
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Table 2. Details of the X-ray Data Collections and Refinements for Compounds 5, 7, 8 and 9.
Compound
5
7
8
9
Formula
C18H17ClN2Se
375.76
monoclinic
P21
C19H20N2OSe
371.34
orthorhombic
P212121
6.6544(8)
7.8134(9)
33.372(4)
90
C19H20N2Se
355.34
monoclinic
P21
10.719(4)
7.495(3)
11.294(4)
90
C18H17N3O2Se
386.31
monoclinic
P21/n
10.5159(7)
7.5401(5)
20.9330(15)
90
M
Crystal system
Space group
10.657(7)
7.525(5)
11.320(8)
90
a/Å
b/Å
c/Å
α
β
115.852(8)
90
817.0(10)
2
24.591
7051
2587
90
90
115.650(6)
90
818.0(5)
2
22.939
6175
1540
91.879(2)
90
1658.9(2)
4
22.793
12,160
γ
U/A3
Z
1735.1(4)
4
21.703
11,930
3043
−1
µ/cm
Reflections collected
Independent reflections
2895
Rint
R1
0.0291
0.0249
0.0544
0.1535
0.0695
0.1012
0.0336
0.0532
0.1398
0.0679
0.0394
0.0903
wR2 [I > 2σ(I)]
Table 3. Details of the X-ray Data Collections and Refinements for Compounds 12, 14 and 16.
Compound
12
14
16
Formula
C18H17BrN2Se
420.21
monoclinic
P21
C20H19ClN2O2Se
433.80
orthorhombic
Pbca
C25H22N2OSe
445.42
monoclinic
P21/c
M
Crystal system
Space group
10.6448(10)
7.4660(7)
11.5064(11)
90
27.974(16)
17.910(11)
7.817(5)
90
10.1342(7)
14.6025(10)
27.942(2)
90
a/Å
b/Å
c/Å
α
β
116.039(3)
90
821.64(14)
2
47.219
6350
90
90
90.421(4)
90
4134.9(5)
8
18.350
31,646
γ
U/A3
Z
3916(4)
8
20.701
26,522
3437
−1
µ/cm
Reflections collected
Independent reflections
2839
7262
Rint
R1
0.0536
0.0309
0.0639
0.0694
0.0422
0.0975
0.2391
0.0701
0.1456
wR2 [I > 2σ(I)]
The bond lengths in 5, 7, 8, 9, 12, 14 and 16 range from 1.286(12) to 1.329(12) Å for C2-N1 and
1.349(11) to 1.366(11) Å for C4-C5, respectively, which are comparable to that in the analogous structure
of 2-piperidino-1,3-selenazole-5-carboxylic acid (1.330(3) and 1.359(4) Å, respectively) [22], indicating
clearly their double bond character. The two C-N bond lengths of both C2-N6 (1.348(112) to 1.402(4) Å)
and N1-C5 (1.374(11) to 1.401(4) Å) in 5, 7, 8, 9, 12, 14 and 16 are marginally longer than that in
2-piperidino-1,3-selenazole-5-carboxylic acid (1.339(3) and 1.361(3) Å, respectively) [50], however,
these values are significantly shorter than the usual single bond length of 1.47 Å [51]. The sums of
the three angles around each of the C2 and C5 atoms are 360.0 and 359.81◦ in
in 7 8 9
5
, 359.95 and 359.89◦
, 359.99 and 359.78◦ in , 360 and 359.98◦ in , 359.99 and 359.88◦ in 12, 360 and 359.99◦ in 14

Molecules 2017, 22, 46
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and 359.76 [360]◦ and 359.91 [359.57]◦ in 16, respectively. These results can be attributed to the
delocalization of -electrons and the lone pair electrons on N6. Also, it is worth noting that the N6
π
nitrogen has sp2 character rather than sp3 for all structures.
◦
Table 4. Selected Bond Distances (Å) and Angles ( ) for Compounds 5, 7, 8, 9, 12, 14 and 16.
5
7
8
9
12
14
16
N1-C2
C2-N6
C2-Se3
Se3-C4
C4-C5
1.302(5)
1.358(5)
1.906(3)
1.860(5)
1.349(5)
1.394(4)
123.8(3)
115.1(3)
121.1(3)
83.59(18)
111.5(3)
112.0(3)
117.1(3)
117.8(4)
124.9(3)
1.295(11)
1.350(11)
1.924(8)
1.886(9)
1.353(12)
1.395(11)
125.1(8)
114.5(6)
120.3(6)
83.9(4)
110.1(6)
112.7(7)
117.2(7)
118.8(8)
123.9(8)
1.300(13)
1.348 (12)
1.914(7)
1.858(12)
1.355(12)
1.387(10)
124.5(7)
114.4(6)
121.1(7)
83.6(4)
111.6(7)
112.9(6)
118.2(7)
117.4(9)
124.2(8)
1.291(4)
1.350(5)
1.912(3)
1.854(4)
1.359(5)
1.389(4)
124.8(3)
114.9(3)
120.3(2)
83.370(15)
111.3(3)
112.6(3)
117.5(3)
117.5(3)
124.9(3)
1.300(9)
1.368(9)
1.896(5)
1.862(8)
1.358(8)
1.387(7)
123.2(5)
115.7(4)
121.1(5)
83.1(3)
111.8(5)
111.6(4)
117.3(4)
117.7(6)
124.9(6)
1.301(4)
1.402(4)
1.899(3)
1.872(4)
1.356(5)
1.401(4)
120.3(3)
116.1(2)
123.7(2)
83.10(15)
111.9(3)
112.0(3)
116.3(3) *
116.9(3)
126.8(3) *
1.329(12)[1.286(12)]
1.348(12)[1.369(12)]
1.863(8)[1.886(7)]
1.866(8)[1.898(9)]
1.366(11)[1.349(11)]
1.374(11)[1.378(11)]
120.5(7)[121.5(7)]
115.6(6)[117.1(6)]
123.8(7)[121.4(6)]
84.3(4)[82.5(4)]
110.6(6)[110.2(6)]
111.7(7)[111.6(7)]
112.9(7)[113.7(7)]
117.8(8)[118.4(8)]
129.2(8)[127.6(8)]
C5-N1
N1-C2-N6
N1-C2-Se3
Se3-C2-N6
C2-Se3-C4
Se3-C4-C5
C5-N1-C2
N1-C5-C15
N1-C5-C4
C4-C5-C15
* C15 should be C19 in compound 14.
Interestingly, in the supramolecular structures of 5, 7, 8, 9, 12, 14 and 16, no intramolecular close
contacts were observed; however, a few intermolecular C-H···Se, C-H···N, C-H···O, C-H···Cl, C-H···Br
interactions are found (Figures 2 and 3 as representative samples). In all structures, there have highly
similar packing motifs with both selenium and nitrogen atoms within the azole ring involved in these
close contacts. Furthermore, there is one or more intermolecular C-H···O, C-H···Cl and C-H···Br close
contacts in the structures of 5, 7, 9, 12, 14 and 16 apart from 8, indicating that the presence of oxygen,
chlorine, bromine and nitrogen atoms implicates these intermolecular close contacts.
Figure 2. The packing framework shows the intermolecular C-H···Se, C-H···N and C-H···O close
contacts in 9.

Molecules 2017, 22, 46
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Figure 3. The packing framework shows the intermolecular C-H···Se, C-H···N and C-H···Br close
contacts in 12.
3. Experimental Section
3.1. General Information
Unless otherwise stated, all reactions were carried out under on oxygen free nitrogen atmosphere
using pre-dried solvents and standard Schlenk techniques, subsequent chromatographic and work
up procedures were performed in air. 1H (400.1 MHz), 13C (100.6◦MHz) and 77Se-{1H} (51.4 MHz
referenced to external Me2Se) NMR spectra were recorded at 25 C (unless stated otherwise) on
Advance II 400s (Bruker, Blue Lion Biotech, Carnation, WA, USA) and GSX 270 (JEOL, Inc., Peabody,
MA, USA) instrument. IR spectra were recorded as KBr pellets in the range of 4000–250 cm−1
on a 2000 FTIR/Raman spectrometer (Perkin-Elmer, Beaconsfield, UK). Mass spectrometry was
performed by the EPSRC National Mass Spectrometry Service Centre, Swansea. X-ray crystal data for
compounds
5
,
7
,
8
,
9
,
12
,
14 and 16 were collected using a SCXMIni Mercury CCD system (Rigaku,
steps accumulating area detector images
Houston, USA). Intensity data were collected using
ω
spanning at least a hemisphere of reciprocal space. All data were corrected for Lorentz polarization
effects. Absorption effects were corrected based on multiple equivalent reflections or by semi-empirical
methods. Structures were solved by direct methods and refined by full-matrix least-squares against F2
by using the program SHELXTL [52]. Hydrogen atoms were assigned riding isotropic displacement
parameters and constrained to idealized geometries. These data (CCDC 1522917–1522923) can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge
Crystallographic Data center, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk.
3.2. Synthesis
General Procedure for the Synthesis of Compounds 5–16
A mixture of α-haloketone (1.0 mmol) in dry methanol (10 mL) was added dropwise to a refluxing
solution of arylselenocarboamide (1.0 mmol) in dry methanol (20 mL) over the course of 1 h.
The reaction mixture was then refluxed for another 1 h. After cooling to room temperature, the mixture
was concentrated on a rotary evaporator, and the residue was neutralized with 5% aqueous ammonia
(30 mL), extracted with dichloromethane (30 mL
×
3), and the combined organic layers washed
with water (20 mL 3), brine (20 mL), and dried over MgSO4. After filtering and drying to
×
remove the solvent the organic residue was purified by silica gel column chromatography (1:9 ethyl
acetate/dichloromethane as eluent) to give 1,3-selenazoles 5–16.

Molecules 2017, 22, 46
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N-Methyl-N-phenethyl-4-phenyl-1,3-selenazol-2-amine (
5
). Pale yellow paste (0.315 g, 92%). Selected IR
1
(KBr, cm−1): 1555, 1480, 1453, 1362, 1324, 1299, 1171, 1099, 1043, 936, 772, 748, 699, 564, 496. H-NMR
(CD2Cl2,
3.05 (s, 3H), 3.01 (t, J(H,H) = 7.4 Hz, 2H) ppm. 13C-NMR (CD2Cl2,
129.0, 128.6, 128.5, 127.3, 126.4, 104.8, 56.0, 39.8, 33.4 ppm. 77Se-NMR (CD2Cl2,
(CI+, m/z): found 343.0717 [M + H]+, calculated mass for C18H18N2SeH: 343.0713.
δ
), 7.90 (s, 1H), 7.88 (d, J(H,H) = 8.3 Hz, 2H), 7.40–7.21 (m, 8H), 3.73 (t, J(H,H) = 7.4 Hz, 2H),
), 171.2, 152.9, 139.3, 136.2), 13.0,
), 575.3 ppm. HRMS
δ
δ
4-(4-Chlorophenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine ( ). Pale white solid (0.362 g, 96%).
6
M.p. 82–84 ◦C. Selected IR (KBr, cm−1): 1554, 1457, 1396, 1363, 1317, 1264, 1175, 1086, 1040, 1009, 935,
838, 756, 703, 679, 496. 1H-NMR (CD2Cl2,
δ), 7.83 (d, J(H,H) = 8.5 Hz, 2H), 7.81 (s, 1H), 7.35–7.21
(m, 7H), 3.72 (t, J(H,H) = 7.7 Hz, 2H), 3.03 (s, 3H), 3.00 (t, J(H,H) = 7.7 Hz, 2H) ppm. 13C-NMR
(CD2Cl2, δ), 171.3, 151.7, 139.2, 134.8, 132.7, 128.9, 128.6, 128.5, 127.7, 126.4, 105.3, 56.0, 39.8, 33.3 ppm.
77Se-NMR (CD2Cl2, ), 571.1 ppm. HRMS (ES+, m/z): found 377.0321 [M + H]+, calculated mass for
δ
C18H17N2ClSeH: 377.0324.
4-(4-Methox◦yphenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine (
7). Dark yellow solid (0.360 g, 97%).
M.p. 74–76 C. Selected IR (KBr, cm−1): 1560, 1490, 1455, 1455, 1408, 1357, 1320, 1244, 1170, 1107, 1029,
1
934, 834, 751, 703, 601, 499. H-NMR (CD2Cl2,
δ), 7.83 (s, 1H), 7.80 (d, J(H,H) = 8.3 Hz, 2H), 7.34–7.15
(m, 5H), 6.88 (d, J(H,H) = 8.3 Hz, 2H), 3.82 (s, 3H), 3.71 (t, J(H,H) = 7.7 Hz, 2H), 3.05 (s, 3H), 3.00
(t, J(H,H) = 7.7 Hz, 2H) ppm. 13C-NMR (CD2Cl2,
), 171.1, 159.1, 152.6, 139.3, 129.2, 129.0, 128.6, 127.6,
126.4, 113.7, 102.8, 56.0, 55.3, 40.0, 33.4 ppm. 77Se-NMR (CD2Cl2, ), 567.1 ppm. HRMS (CI+, m/z):
found 373.0811 [M + H]+, calculated mass for C19H20N2OSeH: 373.0814.
δ
δ
4-(4-Methylphenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine (8). Yellow solid (0.350 g, 98%). M.p.
90–91 ◦C. Selected IR (KBr, cm−1): 1561, 1487, 1457, 1406, 1363, 1321, 1265, 1173, 1110, 1040, 1018, 934,
1
826, 754, 702, 673, 600, 502. H-NMR (CD2Cl2,
δ
), 7.76 (d, J(H,H) = 8.2 Hz, 2H), 7.35–7.17 (m, 8H),
3.73 (t, J(H,H) = 7.4 Hz, 2H), 3.05 (s, 3H), 3.01 (t, J(H,H) = 7.4 Hz, 2H), 2.35 (s, 3H) ppm. 13C-NMR
(CD2Cl2,
21.0 ppm. 77Se-NMR (CD2Cl2,
mass for C19H10N2SeH: 357.0865.
δ), 171.1, 153.0, 139.3, 137.2, 133.5, 129.1, 129.0, 128.6, 126.4, 126.2, 103.9, 56.0, 39.8, 33.4,
δ
), 568.1 ppm. HRMS (CI+, m/z): found 357.0867 [M + H]+, calculated
◦
N-Methyl-4-(4-nitrophenyl)-N-phenethyl-1,3-selenazol-2-amine (
9
). Yellow solid (0.360 g, 93%). M.p. 96–98 C.
Selected IR (KBr, cm−1): 1600, 1593, 1558, 1501, 1406, 1336, 1174, 1106, 1045, 935, 857, 847, 755, 703,
1
501. H-NMR (CDCl3,
δ
), 8.15 (d, J(H,H) = 9.0 Hz, 2H), 7.94 (d, J(H,H) = 9.0 Hz, 2H), 7.44 (s, 1H),
7.27–7.17 (m, 5H), 3.68 (t, J(H,H) = 7.7 Hz, 2H), 3.00 (s, 3H), 2.95 (t, J(H,H) = 7.7 Hz, 2H) ppm. 13C-NMR
(CDCl3, ), 171.4, 151.0, 146.6, 141.9, 138.8, 128.9, 128.7, 126.8, 126.6, 124.0, 109.1, 56.2, 40.1, 33.4 ppm.
77Se-NMR (CDCl3, ), 590.1 ppm. HRMS (CI+, m/z): found 388.0557 [M + H]+, calculated mass for
δ
δ
C18H17N3O2SeH: 388.0559.
4-(2,5-Dimethoxyphenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine (10). Green oil (0.360 g, 90%).
Selected IR (KBr, cm−1): 1674, 1558, 1496, 1464, 1409, 1357, 1280, 1217, 1178, 1047, 1023, 809, 744,
1
700, 585. H-NMR (CDCl3,
δ
), 7.76 (s, 1H, Azole-H), 7.21–7.13 (m, 5H, Ar-H), 6.94 (d, J(H,H) = 7.7 Hz
,
1H, Ar-H), 6.82 (s, 1H), 6.79 (d, J(H,H) = 7.7 Hz, 1H), 3.80 (s, 3H), 3.70 (s, 3H), 3.63 (t, J(H,H) = 7.7 Hz,
2H), 2.96 (s, 3H), 2.93 (t, J(H,H) = 7.7 Hz, 2H) ppm. 13C NMR (CDCl3,
), 169.2, 153.6, 139.2, 128.9, 128.6,
),
δ
128.3, 126.4, 120.4, 116.1, 113.8, 113.2, 112.5, 110.7, 56.0, 55.8, 55.7, 40.0, 33.4 ppm. 77Se-NMR (CDCl3,
δ
572.7 ppm. HRMS (CI+, m/z): found 403.0915 [M + H]+, calculated mass for C20H22N2O2SeH: 403.0919.
4-(2,4-Dichlorophenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine (11). Yellow oil (0.375 g, 91%). Selected IR
(KBr, cm−1): 1697, 1560, 1550, 1496, 1464, 1370, 1309, 1172, 1100, 1030, 936, 866, 825, 797, 747, 699, 554,
1
529, 497. H-NMR (CDCl3,
δ), 7.78 (d, J(H,H) = 8.5 Hz, 2H), 7.45 (s, 1H), 7.44 (d, J(H,H) = 8.4 Hz, 1H),
7.36–7.35 (m, 2H), 7.22–7.15 (m, 3H), 3.62 (t, J(H,H) = 7.7 Hz, 2H), 2.94 (s, 3H), 2.93 (t, J(H,H) = 7.7 Hz,
2H) ppm. 13C-NMR (CDCl3,
), 169.2, 147.6, 137.9, 132.5, 132.0, 131.5, 129.7, 129.0, 127.8, 127.6, 125.9,
125.4, 109.5, 55.1, 39.0, 32.4 ppm. 77Se-NMR (CDCl3, ), 578.9 ppm. HRMS (CI+, m/z): found 410.9921
[M + H]+, calculated mass for C18H16Cl2N2SeH: 410.9924.
δ
δ

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10 of 13
4-(4-Bromophenyl)-N-methyl-N-phenethyl-1,3-selenazol-2-amine (12). Yellow solid (0.418 g, 95%). Selected IR
(KBr, cm−1): 1559, 1472, 1455, 1407, 1392, 1367, 1318, 1176, 1069, 1007, 937, 836, 753, 705, 676, 491.
1H-NMR (CDCl3,
δ
), 7.67 (d, J(H,H) = 8.7 Hz, 2H), 7.59 (s, 1H), 7.40 (d, J(H,H) = 8.7 Hz, 2H), 7.26–7.15
(m, 5H), 3.65 (t, J(H,H) = 7.5 Hz, 2H), 2.97 (s, 3H), 2.93 (t, J(H,H) = 7.5 Hz, 2H) ppm. 13C-NMR
(CDCl3, ), 171.2, 152.0, 139.0, 135.1, 131.5, 128.9, 128.7, 128.0, 126.5, 125.4, 105.3, 56.2, 40.0, 29.7 ppm.
77Se-NMR (CDCl3, ), 577.8 ppm. HRMS (CI+, m/z): found 420.9809 [M + H]+, calculated mass for
δ
δ
C18H17BrN2SeH: 420.9811.
Ethyl phenethyl(4-phenyl-1,3-selenazol-2-yl)carbamate (13). Yellowish white solid (0.384 g, 96%).
M.p. 65–67 ◦C. Selected IR (KBr, cm−1): 1695, 1600, 1517, 1477, 1439, 1408, 1383, 1269, 1197, 1025, 880,
753, 718, 699, 666, 499. 1H-NMR (CD2Cl2,
δ
), 7.95 (d, J(H,H) = 8.5 Hz, 2H), 7.79 (s, 1H), 7.44–7.29
(m, 8H), 4.44 (q, J(H,H) = 7.2 Hz, 2H), 4.21 (t, J(H,H) = 6.9 Hz, 2H), 3.08 (t, J(H,H) = 6.9 Hz, 2H),
1.29 (t, J(H,H) = 7.2 Hz, 3H) ppm. 13C-NMR (CD2Cl2,
), 161.8, 150.6, 139.1, 136.0, 129.1, 128.6, 128.5,
), 679.9 ppm. HRMS (ES+, m/z): found 401.0766
δ
127.55, 126.4, 126.2, 113.3 ppm. 77Se-NMR (CD2Cl2,
[M + H]+, calculated mass for C20H20N2O2SeH: 401.0768.
δ
Ethyl (4-(4-chlorophenyl)-1,3-selenazol-2-yl)(phenethyl)carbamate (14). Pale orange solid (0.416 g, 96%).
◦
M.p. 68–70 C. Selected IR (KBr, cm−1): 1698, 1518, 1474 1441, 1382, 1314, 1244, 1189, 1089, 1030,
839, 739, 701, 578, 554, 498. 1H-NMR (CD2Cl2,
7.39 (d, J(H,H) = 8.5 Hz, 2H), 7.31–7.22 (m, 5H), 4.42 (t, J(H,H) = 6.9 Hz, 2H), 4.19 (q, J(H,H) = 7.2 Hz
2H), 3.07 (d, J(H,H) = 7.2 Hz, 2H), 1.29 (t, J(H,H) = 6.9 Hz, 3H) ppm. 13C-NMR (CD2Cl2,
),
162.0, 149.4, 139.0, 134.6, 133.0, 129.1, 128.7, 128.5, 127.6, 126.5, 113.9, 63.4, 48.5, 34.2, 14.2 ppm.
77Se-NMR (CD2Cl2, ), 684.2 ppm. HRMS (CI+, m/z): found 435.0375 [M + H]+, calculated mass for
δ), 7.89 (d, J(H,H) = 8.5 Hz, 2H), 7.77 (s, 1H),
,
δ
δ
C20H19N2ClO2SeH: 435.0378.
Ethyl (4-(4-methoxyphenyl)-1,3-selenazol-2-yl)(phenethyl)carbamate (15). Pale yellow solid (0.410 g, 95%).
M.p. 52–54 ◦C. Selected IR (KBr, cm−1): 1689, 1603, 1578, 1513, 1438, 1405, 1382, 320, 1301, 1250, 1176,
1027, 881, 835, 748, 700, 618, 562. 1H-NMR (CD2Cl2,
δ
), 7.87 (d, J(H,H) = 8.8 Hz, 2H), 7.62 (s, 1H),
7.31–7.25 (m, 5H), 6.94 (d, J(H,H) = 8.0 Hz, 2H), 4.43 (t, J(H,H) = 6.9 Hz, 2H), 4.20 (q, J(H,H) = 6.6 Hz,
2H), 3.83 (s, 3H), 3.07 (d, J(H,H) = 6.9 Hz, 2H), 1.29 (t, J(H,H) = 6.6 Hz, 3H) ppm. 13C-NMR (CD2Cl2,
),
δ
161.6, 159.3, 150.4, 139.1, 130.5, 129.1, 128.5, 127.4, 126.4, 113.9, 113.6, 111.2, 63.3, 55.3, 48.5, 34.2,
14.2 ppm. 77Se-NMR (CD2Cl2, δ), 675.7 ppm. HRMS (CI+, m/z): found 431.0867 [M + H]+, calculated
mass for C21H22N2O3SeH: 431.0870.
(2-(Methyl(phenethyl)amino)-4-phenyl-1,3-selenazol-5-yl)(phenyl)methanone (16). Pale yellow paste (0.415 g,
93%). Selected IR (KBr, cm−1): 1595, 1575, 1542, 1473, 1327, 1284, 1103, 1025, 881, 779, 697, 670,
1
599. H-NMR (CDCl3,
δ
), 7.35–7.32 (m, 2H), 7.27–7.22 (m, 4H), 7.19–7.16 (m, 3H), 7.13–7.09 (m, 2H),
7.04–6.93 (m, 4H), 4.04 (t, J(H,H) = 7.4 Hz, 2H), 2.97 (t, J(H,H) = 7.4 Hz, 2H), 1.97 (s, 3H) ppm. 13C-NMR
(CDCl3, ), 190.3, 172.9, 160.6, 138.5, 138.4, 136.0, 131.9, 130.1, 129.3, 129.1, 128.7, 127.5, 127.4, 126.7,
60.4, 33.5, 15.0 ppm. 77Se-NMR (CDCl3, ), 609.7 ppm. HRMS (CI+, m/z): found 447.0968 [M + H]+,
δ
δ
calculated mass for C25H22N2OSeH: 447.0972.
4. Conclusions
In summary, a series of new 4-substituted-1,3-selenazol-2-amines were prepared in excellent
yields by two-component cyclization of α-haloketones with equimolar amounts of selenoureas which
were obtained from the reaction of Woollins’ reagent with cyanamides, followed by hydrolysis.
The structures of all new compounds have been elucidated by using 1H-, 13C-, 77Se-NMR spectroscopy
and accurate mass measurements. Seven single crystal X-ray structures reveal slightly different
structure profiles. In all cases, the newly formed 1,3-selenazole ring is not complete planar, and none
of the mean planes of the newly formed five-membered ring are coplanar with the adjacent aryl rings,
showing different dihedral angles. Interestingly, no intramolecular close contacts were found; however,
intermolecular C-H···Se, C-H···N, C-H···O, C-H···Cl and C-H···Br short interactions are found in

Molecules 2017, 22, 46
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the structures and the oxygen, chlorine, bromine and nitrogen atoms play very key roles in these
intermolecular close contacts.
Supplementary Materials: Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/22/
1/46/s1.
Acknowledgments: We are grateful to the University of St. Andrews for financial support and the EPSRC
National Mass Spectrometry Service Centre (Swansea) for mass spectral measurements.
Author Contributions: G.H. and J.D.W. conceived and designed; G.H. performed the experiments; J.D. and
A.M.Z.S. performed the X-ray structural measurements; J.D.W. provided critical intellectual input in this study;
All authors participated in the preparation of the manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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