Synthesis, characterization and antimicrobial activity of new chalcones and their 6-aryl-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine derivatives

Article abstract of DOI:10.1080/10426507.2016.1277526

Chalcones (5a-h) were prepared in high yields via the condensation of 3-acetyl-2,5-dichlorothiophene (3) with aryl aldehydes (4a-h). The reaction of the resulting chalcones with thiourea in the presence of a catalytic amount of hydrochloric acid provided the 1,3-thiazin-2-amine derivatives (6a-g) in moderate yields. All new compounds were characterized by extensive NMR analysis data, including 1D NMR experiments (¹H and ¹³C) and 2D NMR experiments (COSY, HMBC, HSQC), as well as ESIMS and HRESIMS data. The newly synthesized compounds were evaluated for their biological activities, which demonstrate a very good to low bioactivities as antibacterial and antifungal, respectively.

Full text of DOI:10.1080/10426507.2016.1277526

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Synthesis, Characterization and Antimicrobial Activity of New Chalcones and Their 6-
Aryl-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine Derivatives
Mahmoud Al-Refaia,*, Mohammad M. Ibrahima, Sohail Alsohailib, Armin Geyerc.
a
Department of Chemistry, Faculty of Science, Al al-Bayt University, P.O.BOX 130040,
Al-Mafraq 25113, Jordan.
b
c
Department of Biology, Faculty of Science, Al al-Bayt University, Al-Mafraq, Jordan.
Faculty of Chemistry, Philipps University Marburg, Hans-Meerwein-Straße 4, 35032
Marburg, Germany.
*Corresponding author. M. Al-Refai, Department of Chemistry, Faculty of Science, University
of Al al-Bayt, P.O.BOX 130040, Al-Mafraq 25113, Jordan. e-mail:
mahmoud_alrefai@aabu.edu.jo
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Synthesis, Characterization and Antimicrobial Activity of New Chalcones and Their 6-
Aryl-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine Derivatives
Abstract
Chalcones (5a-h) were prepared in high yields via the condensation of 3-acetyl-2,5-
dichlorothiophene (3) with aryl aldehydes (4a-h). The reaction of the resulting chalcones with
thiourea in the presence of a catalytic amount of hydrochloric acid provided the 1,3-thiazin-2-
amine derivatives (6a-g) in moderate yields. All new compounds were characterized by
extensive NMR analysis data, including 1D NMR experiments (1H and 13C) and 2D NMR
experiments (COSY, HMBC, HSQC), as well as ESIMS and HRESIMS data. The newly
synthesized compounds were evaluated for their biological activities, which demonstrate a very
good to low bioactivities as antibacterial and antifungal, respectively.
Keywords
Thiazine; Thiophene; Thiourea; Condensation; Chalcone.
Introduction
Chalcones exhibit a wide range of biological properties including antioxidant[1-4], anticancer[5-7]
,
antiviral[8,9], anti-inflammatory[10-12], antimalarial[13,14], antileishmanial[15-19], antitubercular[20]
and antimicrobial activities[21,22]. During the studies on the structure of clavicin, it was found that
the biological activity of chalcones could be attributed to the presence of the α,β-unsaturated keto
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functional group[23]. In addition to this, chalcones are useful building blocks for the preparation
of synthetically significant heterocycles such as pyrazoles[24-28], isoxazoles[29], thiazine[30]
oxazine[31], and many others related motifs[32,33]
,
.
1,3-Thiazine is a six membered heterocyclic ring which contains two hetero atoms (N and S)
placed in the heterocyclic ring at the 1,3 positions. Many thiazine derivatives have been
synthesized because of their wide range of biological activities[34,35] such as fungicide[36-39], anti-
inflammatory[40,41], analgesic and antipyretic[42,43], antimicrobial and antiviral[44-48], and antitumor
properties[49,50]. One of the most convenient approaches to synthesize chalcones is the
condensation of aryl ketones with aromatic aldehydes mediated by a suitable base such as
potassium or sodium hydroxide. Herein, we report the synthesis, characterization and
antimicrobial activity of 1,3-thiazin-2-amine derivatives derived from chalcones bearing a
thiophene nucleus (Schemes 2 and 3).
Results and Discussion
A large scale synthesis of 3-acetyl-2,5-dichlorothiophene (3) was achieved by Friedel-
Crafts acylation using 2,5-dichlorothiophene (1), acetyl chloride, anhydrous aluminium chloride
as a Lewis acid catalyst and carbon disulfide as the solvent (Scheme 1).[51]
Scheme 1: Preparation of 3-acetyl-2,5-dichlorothiophene (3).
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It was envisaged to prepare chalcones using Claisen-Schmidt condensation. For this purpose, the
precursor, 3-acetyl-2,5-dichlorthiophene (3) was condensed with an array of aromatic aldehydes
(4a-h) in the presence of potassium hydroxide. The reaction involves the formation of the
enolate anion that is subsequently condensed with the aldehydes to produce the desired
chalcones (5a-h) in excellent yields (Scheme 2). Chalcones 5a-c, g have been reported
previously [27,52-54], while all other chalcones are new.
Scheme 2: Base catalyzed Claisen-Schmidt synthesis of chalcones (5a-h).
Condensation of the synthesized chalcones (5a-d, f, g) with thiourea in the presence of
hydrochloric acid as catalyst afforded the 1,3-thiazine derivatives (6a-d, f, g) in moderate yields
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(Scheme 3). This two-step approach to synthesize thiazine derivatives has also been successfully
applied to one-pot multi-step transformation by achieving the synthesis of thiazine (6e) in a good
yield.
Scheme 3: Synthesis of substituted 1,3-thiazines (6a-g).
All new isolated chalcones (5d-f, h) and thiazines (6a-g) were characterized using different
1
13
spectroscopic methods including IR, H-NMR, C-NMR, 2D-NMR, and mass spectrometry. A
detailed analysis of 2D NMR data enabled an unambiguous determination of the exact chemical
shifts of all protons and carbons for all compounds. Complete assignments for all protons and
carbons are given in the experimental part. The ESIMS and HRESIMS data analyses revealed
the correct molecular ion peaks for all compounds as suggested by their molecular formulas.
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The H NMR spectra of all new chalcones (5d-f, h) showed two doublet peaks in the
3
olefinic region at 7.45-8.65 ppm due to the α, β‐protons with a coupling constant value of J =
15.59-16.87 Hz which supports the formation of the E isomers. In addition, the proton of the
thienyl moiety in all chalcones appeared as singlet at δ 7.70–7.89 ppm. The 1H NMR spectra of
1
the newly prepared heterocycles are in good agreement with the proposed structures. As the H
NMR spectra of the final products showed only one exchangeable proton signal, and the 13C
NMR have no C=S signal, it is plausible to conclude the formation of thiazine compared to
competing pyrimidine structure. The thiazine NH2 exchangeable proton signals appeared as
broad singlet at δ 6.92-7.14 ppm. The two mutually coupled doublet signals at δ 5.58-5.78 ppm
and δ 5.10-5.87 ppm are assigned to H-5 and H-6 thiazine protons, with coupling constants in the
range 6.24-7.52 Hz. The singlet appeared at δ 7.21-7.28 ppm is related to the thienyl proton (see
supporting information for details).
The 13C NMR spectra of the new chalcones (5d-f, h) showed the carbonyl carbon at 183.1-
183.7 ppm. The 13C NMR spectra of thiazines (6a-g) revealed absorption in the range 36.0-42.1
ppm corresponding to the C-6 carbon. The absorption appeared at 101.1-103.0 attributed to the
C-5 carbon of the thiazine ring.
Biological Screening
All the newly synthesized compounds were tested for their bioactivities using S. aureus
and pleasingly, chalcone 5d exhibited significant antibacterial activities compared to standard
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antibacterial agents. All remaining chalcones showed inferior activities against all the applied
bacterial species. Notably, all the thiazine compounds (6a-e) exhibited significant antibacterial
activity against S. aureus compared to the standard antibiotics, cefaclor and cefuroxime.
In contrast to antibacterial activities, both chalcones and thiazines possess low antifungal
properties when tested against C. albicans and no activity was observed against A. niger. A
summary of the biological activity is presented in Figures S 1 and S 2 (Supplemental Materials).
Experimental
Materials
Aromatic aldehydes and thiourea were purchased from Aldrich. 2,5-dichlorothiophene was
purchased from Acros. 3-Acetyl-2,5-dichlorothiophene was prepared according to literature
procedure[51]. Solvents were dried and distilled according to standard methods[55]
.
Instrumentation
1H (500 MHz, 600 MHz) and 13C (125 MHz, 150 MHz) NMR spectra were recorded in DMSO-
d6 which was used as an internal standard at 300 K on Bruker spectrometers (500 MHz, 600
MHz). Chemical shifts δ are given in parts per million (ppm) and were determined from the
center of the respective coupling pattern (s: singlet, d: doublet, dd: doublet of doublet, t: triplet).
ESI-HMRS measurements were performed on a LTQ-FT mass spectrometer (Thermo Fisher
Scientific).
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Thin layer chromatography (TLC) monitoring of the reaction was carried out using analytical
TLC plates coated with silica gel (60 F254, Merck). Preparative thin layer chromatography
(PTLC) was carried out at room temperature (r.t.) with the mobile phase being CHCl3/pentane
(30 : 70) mixture. The Supplemental Materials contains sample 1H, 13C NMR spectra and HRMS
data for compounds 5 and 6 (Figures S 3 – S 45)
Synthesis
General procedure for the synthesis of Chalcones 5a-h
An equimolar mixture of the aryl aldehyde, KOH were dissolved in MeOH (50 mL). To this
solution 3-acetyl-2,5-dichloro-thiophene, 3, in MeOH (10 mL) was added dropwise. After the
addition was completed, the reaction mixture was stirred at r.t. for 10 h. The precipitate formed
was filtered off, washed with MeOH and dried without any further purification.
(E)-1-(2,5-dichlorothiophen-3-yl)-3-(2,4-dimethoxyphenyl)prop-2-en-1-one (5d). Yield:
95%, – 1H NMR (DMSO-d6, 500 MHz):  = 7.92 (d, J = 16.87 Hz, 1H, H-3), 7.85 (d, J = 8.62
Hz, 1H, H-6"), 7.70 (s, 1H, H-4'), 7.45 (d, J = 16.87 Hz, 1H, H-2), 6.67 (d, J = 2.20 Hz, 1H, H-
3"), 6.66 (dd, J = 7.33, 2.20 Hz, 1H, H-5"), 3.91 (s, 3H, 2"-OCH3), 3.86 (s, 3H, 4"-OCH3). – 13C
NMR (DMSO-d6, 125 MHz)  = 183.7 (C-1, C=O), 164.0 (Cq-4"),160.7 (Cq-2"), 140.4 (CH-3),
138.0 (Cq-2'), 131.1 (CH-6"), 130.5 (Cq-5'), 128.4 (CH-4'), 126.0 (Cq-3'), 121.6 (CH-2), 116.0
(Cq-1"), 107.0 (CH-5"), 98.8 (CH-3"), 56.4 (2"-OCH3), 56.1 (4"-OCH3). – (+)-HRESIMS m/z
364.9773 [M+Na]+, 366.9745 [M+Na+2]+, 368.9717 [M+Na+4]+, (calcd for C15H12Cl2O3SNa,
364.9773).
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(E)-3-(3,5-dibromo-4-hydroxyphenyl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one
(5e).
Yield: 80%, – 1H NMR (DMSO-d6, 500 MHz):  = 10.60 (bs, 1H, OH), 8.14 (s, 2H, 2", 6"), 7.89
13
(s, 1H, H-4'), 7.59 (d, J = 15.59 Hz, 1H, H-3), 7.52 (d, J = 15.59 Hz, 1H, H-2). – C NMR
(DMSO-d6, 125 MHz)  = 183.1 (C-1, C=O), 153.6 (Cq-4"),142.9 (CH-3), 137.1 (Cq-2'), 133.4
(CH-2",6"), 131.8 (Cq-5'), 129.3 (Cq-1"),128.5 (CH-4'), 125.9 (Cq-3'), 123.9 (CH-2), 112.7 (Cq-
3",5"). – (-)-ESIMS m/z 453 ([M - H]-, 38), 455 ([M-H+2]-, 100), 457 ([M-H+4]-, 92), 459 ([M-
H+6]-, 36), 461([M-H+8]-, 5). −(-)-HRESIMS m/z 454.7739 [M-H+2]-, 456.7715[M-H+4]-
,458.7687 [M-H+6]- (calcd for C13H5Br2Cl2O2S, 452.7760).
(E)-3-(3-bromo-4-methoxyphenyl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one (5f). Yield:
94%, – 1H NMR (DMSO-d6, 500 MHz):  = 8.20 (d, J = 2.20 Hz, 1H, H-2"), 7.83 (s, 1H, H-4'),
7.82 (dd, J = 8.62, 2.20 Hz, 1H, H-6"), 7.62 (d, J = 15.77 Hz, 1H, H-3), 7.48 (d, J = 15.77 Hz,
13
1H, H-2), 7.18 (d, J = 8.62 Hz, 1H, H-5"), 3.91 (s, 3H, 4"-OCH3). C NMR (DMSO-d6, 125
MHz)  = 183.3 (C-1, C=O), 157.9 (Cq-4"),144.0 (CH-3), 137.4 (Cq-2'), 133.4 (CH-2"), 131.5
(CH-6"), 131.4 (Cq-5'), 128.9 (Cq-1"), 128.5 (CH-4'), 125.9 (Cq-3'), 123.3 (CH-2), 113.2 (CH-
5"), 111.9 (Cq-3"), 57.1 (4"-OCH3). – (+)-ESIMS m/z 413 ([M+Na]+, 45), 415 ([M+Na+2]+, 76),
417 ([M+Na+4]+, 36). − (+)-HRESIMS m/z 412.8769 [M+Na]+, 414.8745 [M+Na+2]+,
416.8719 [M+Na+4]+, (calcd for C14H9BrCl2O2SNa, 412.8776).
1
(E)-3-(anthracen-9-yl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one (5h). Yield: 83%, – H
NMR (DMSO-d6, 500 MHz):  = 8.73 (s, 1H, H-8"), 8.65 (d, J = 16.02 Hz, 1H, H-3), 8.30 (dd, J
= 8.54,1.22 Hz , 2H, H-3"), 8.18 (dd, J = 8.24, 1.53 Hz, 2H, H-6"), 7.77 (s, 1H, H-4'),7.63 (m,
13
2H, H-4"), 7.46 (d, J = 16.02 Hz, 1H, H-2), 7.61 (m, 2H, H-5"). – C NMR (DMSO-d6, 125
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MHz)  =183.1 (C-1, C=O), 141.8 (CH-3), 137.3 (Cq-2'), 133.3 (CH-2), 131.8 (Cq-5'), 131.3 (Cq-
1"), 129.6 (Cq-7"), 129.5 (Cq-2"), 129.4 (CH-6"), 129.2 (CH-8"), 128.6 (CH-4'), 127.4 (CH-4"),
126.3 (Cq-3'), 126.2 (CH-5"), 125.5 (CH-3"). – (+)-ESIMS m/z 405 ([M+Na]+, 100), 407
([M+Na+2]+, 73), 409 ([M+Na+4]+, 17). − (+)-HRESIMS m/z 404.9877 [M+Na]+, 406.9848
[M+Na+2]+, (calcd for C21H12Cl2OSNa, 404.9878).
General procedure for the synthesis of thiazines 6a-g
A mixture of 1,3-diaryl-2-propen-1-ones (chalcones) (5a-g) (0.01 mol), thiourea (0.03 mol) and
concentrated hydrochloric acid (0.01 mol) in methanol (50 mL) was refluxed for about 10 hr, the
reaction mixture was cooled and then poured into ice water (150 mL), and then neutralized with
dilute potassium hydroxide solution. The obtained solid was filtered off, air-dried, and purified
using preparative thin layer chromatography (PTLC).
4-(2,5-dichlorothiophen-3-yl)-6-(4-fluorophenyl)-6H-1,3-thiazin-2-amine (6a). Yield: 48%, –
1H NMR (DMSO-d6, 600 MHz):  = 7.38 (dd, J = 8.62, 5.50 Hz, 2H, H-2",6"), 7.24 (s, 1H, H-
4'), 7.18 (t, J = 8.80 Hz, 2H, H-3",5"), 7.09 (bs, 2H, 2-NH2), 5.71 (d, J = 6.24 Hz, 1H, H-5), 5.11
(d, J = 6.24, 3.0 Hz, 1H, H-6). – 13C NMR (DMSO-d6, 150 MHz)  = 162.8, 161.3 (d, J = 244.8
Hz, Cq-4"), 154.0 (Cq-2), 142.1 (Cq-4), 138.8 (Cq-1"), 138.3 (Cq-3'), 129.9, 129.8 (d, 8.67 Hz,
CH-2",6"), 128.6 (CH-4'), 124.6 (Cq-5'), 120.9 (Cq-2'), 116.0, 115.9 (d, J = 21.35 Hz, CH-3",5"),
103.01 (CH-5), 41.4 (CH-6). –(+)-HRESIMS m/z 380.9461 [M+Na]+, 382.9433 [M+Na+2]+,
384.2077 [M+Na+4]+, (calcd for C14H9Cl2FN2S2Na, 380.9460).
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6-(2-bromophenyl)-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine (6b). Yield: 57%,
– 1H NMR (DMSO-d6, 600 MHz):  = 7.66 (dd, J = 7.89, 1.10 Hz, 1H, H-3"), 7.39 (td, J = 7,70,
1.10 Hz, 1H, H-4"), 7.33 (dd, J = 7.89, 1.83 Hz, 1H, H-6"), 7.25 (s, 1H, H-4'), 7.24 (td, J = 7.70,
1.65 Hz, 1H, H-5"), 7.14 (bs, 2H, 2-NH2) 5.69 (d, J = 7.15 Hz, 1H, H-5), 5.21 (d, J = 7.15 Hz,
1H, H-6). – 13C NMR (DMSO-d6, 150 MHz)  = 153.9 (Cq-2), 142.7 (Cq-4), 140.1 (Cq-1"),
138.4 (Cq-3'), 133.6 (CH-3"), 130.1 (CH-5"), 129.5 (CH-6"), 128.7 (CH-4"), 128.6 (CH-4'),
124.6 (Cq-5'), 123.3 (Cq-2"), 121.2 (Cq-2'), 101.2 (CH-5), 40.3 (CH-6). – (+)-ESIMS m/z 419
([M+H]+, 62), 421 ([M+H+2]+, 100), 423 ([M+H+4]+, 52), 425 ([M+H+6]+, 12) . (+)-HRESIMS
m/z 418.8839 [M+H]+, 420.8815 [M+H+2]+, 422.8790 [M+H+4]+, 424.8762 [M+H+6]+, (calcd
for C14H10BrCl2N2S2, 418.8840).
6-(3-bromophenyl)-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine(6c). Yield: 51%, –
1H NMR (DMSO-d6, 600 MHz):  = 7.53 (d, J = 3.66, 1H, H-2"), 7.48 (dd, J = 7.52, 3.30 Hz, C-
4"), 7.33 (m, 2H, H-5",6"), 7.23 (s, 1H, H-4'), 7.11 (bs, 2H, 2-NH2), 5.71 (d, J = 7.52 Hz, 1H, H-
13
5), 5.10 (d, J = 7.52 Hz, 1H, H-6). – C NMR (DMSO-d6, 150 MHz)  = 153.4 (Cq-2),145.4
(Cq-1"), 142.1 (Cq-4), 138.5 (Cq-3'), 131.4 (CH-5"), 130.4 (CH-2"), 130.5 (CH-4"), 128.6 (CH-
4'), 126.8 (CH-6"), 124.6 (Cq-5'), 122.2 (Cq-3"), 121.2 (Cq-2'), 102.2 (CH-5), 41.4 (CH-6). – (+)-
ESIMS m/z 419 ([M+H]+, 62), 421 ([M+H+2]+, 100), 423 ([M+H+4]+, 52), 425 ([M+H+6]+, 12)
. – (+)-HRESIMS m/z 418.8839 [M+H]+, 420.8815 [M+H+2]+, 422.8790 [M+H+4]+, 424.8762
[M+H+6]+, (calcd for C14H10BrCl2N2S2, 418.8840).
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4-(2,5-dichlorothiophen-3-yl)-6-(2,4-dimethoxyphenyl)-6H-1,3-thiazin-2-amine (6d). Yield:
68%, – 1H NMR (DMSO-d6, 600 MHz):  = 7.22 (s,1H, H-4'), 7.08 (d, J = 8.80 Hz, 1H, H-6"),
6.94 (bs, 2H, 2-NH2), 6.58 (d, J = 2.57 Hz, 1H, H-3"), 6.50 (dd, J = 8.80, 2.20 Hz, 1H, H-5"),
5.58 (d, J = 7.15Hz, 1H, H-5), 5.11 (d, J = 7.15 Hz, 1H, H-6), 3.83 (s, 2"-OCH3), 3.75 (s, 4"-
OCH3). – 13C NMR (DMSO-d6, 150 MHz)  =160.7 (Cq-4"), 157.3 (Cq-2"), 154.7 (Cq-2), 141.6
(Cq-4), 138.4 (Cq-3'), 129.0 (CH-6"), 128.6 (CH-4’), 124.5 (Cq-5'), 121.3 (Cq-1"), 120.6 (Cq-2'),
105.2 (CH-5"), 102.3 (CH-5), 99.1 (CH-3"), 56.2 (2"-OCH3), 55.7 (4"-OCH3-), 35.8 (CH-6). –
(+)-ESIMS m/z 401 ([M+H]+, 100), 403 ([M+H+2]+, 71), 405 ([M+H+4]+, 16). – (-)-HRESIMS
m/z 398.9802 [M-H]-, 400.9771 [M-H+2]-, 402.8047 [M-H+4]-, (calcd for C16H13Cl2N2O2S2,
398.9801).
4-(2,5-dichlorothiophen-3-yl)-6-(2,5-dimethoxyphenyl)-6H-1,3-thiazin-2-amine (6e). Yield:
71%, – 1H NMR (DMSO-d6, 600 MHz):  = 7.21(s, 1H, H-4'), 6.99 (bs, 2H, 2-NH2), 6.96 (d, J =
8.99 Hz, 1H, H-3"), 6.85 (dd, J = 8.99, 3.12 Hz, 1H, H-4"), 6.77 (d, J = 3.12 Hz, 1H, H-6"), 3.80
(s, 3H, 2"-OCH3), 3.67 (s, 3H, 5"-OCH3), 5.59 (d, J = 6.79 Hz, 1H, H-5), 5.15 (d, J= 6.79 Hz, H-
6). – 13C NMR (DMSO-d6, 150 MHz)  = 154.4 (Cq-2), 153.5 (Cq-5"), 150.3 (Cq-2"), 142.0 (Cq-
4), 138.7 (Cq-3'), 130.3 (Cq-1"), 128.5 (CH-4'), 124.6 (Cq-5'), 120.9 (Cq-2'), 114.8 (CH-6"), 113.1
(CH-4"), 112.5 (CH-3"), 102.0 (CH-5), 56.5 (2"-OCH3), 55.7 (5"-OCH3), 36.0 (CH-6). – (-)-
ESIMS m/z 399 ([M-H]-, 100), 401 ([M-H+2]-, 69), 403 ([M-H+4]-, 16). – (-)-HRESIMS m/z
398.9803 [M-H]-, 400.9773 [M-H+2]-, 402.9743 [M-H+4]-, (calcd for C16H13Cl2N2O2S2,
398.9801).
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6-(3-bromo-4-methoxyphenyl)-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine (6f).
Yield: 42%, – 1H NMR (DMSO-d6, 600 MHz):  = 7.52 (d, J = 2.13 Hz, 1H, H-2"), 7.30 (dd, J =
3
8.59, 2.13 Hz, 1H, H-6"), 7.21 (s,1H, H-4'), 7.08 (d, J = 8.59 Hz, 1H, H-5"), 7.01 (bs, 2H, 2-
NH2), 5.67 (d, J = 6.65 Hz, 1H, H-5), 5.03 (d, J = 6.64 Hz, 1H, H-6), 3.83 (s, -4"-OCH3). – 13C
NMR (DMSO-d6, 150 MHz)  = 154.7 (Cq-4"), 153.2 (Cq-2), 141.2 (Cq-4), 135.7 (Cq-1"), 131.6
(CH-2"), 128.0 (CH-4'), 127.8 (CH-6"), 124.0 (Cq-5'), 120.3 (Cq-2'), 112.7 (CH-5"), 110.4 (Cq-
3"), 102.2 (CH-5), 56.2 (4"-OCH3), 42.1 (CH-6). − (-)-HRESIMS m/z 446.8804 [M-H]-,
448.8780 [M-H+2]-, 450.8745 [M-H+4]-, 452.8949 [M-H+6]- (calcd for C15H10BrCl2N2OS2Na,
446.8800). − (+)-HRESIMS m/z 470.8765 [M+Na]+, 472.8740 [M+Na+2]+, 474.8712
[M+Na+4]+, 476.3734 [M+Na+6]+(calcd for C15H11BrCl2N2OS2Na, 470.8765).
4-(2,5-dichlorothiophen-3-yl)-6-(naphthalen-3-yl)-6H-1,3-thiazin-2-amine (6g). Yield: 65%,
– 1H NMR (DMSO-d6, 600 MHz):  = 8.26 (d, J = 8.37 Hz, 1H, 4"), 7.97 (dd, J = 7.92, 1.50 Hz,
1H, H-7"), 7.86 (dd, J = 6.27, 3.15 Hz, 1H, H-9"), 7.60 (td, 8.30, 1.30 Hz, 1H, H-5"), 7.55 (td,
7.87, 1.30 Hz, 1H, H-6"), 7.48 (m, 2H, H-2", 10"), 7.28 (s, 1H, H-4’), 6.92 (bs, 2H, 2-NH2), 5.78
(d, J = 6.40 Hz, 1H, H-5), 5.87 (d, J = 6.40 Hz, 1H, H-6). – 13C NMR (DMSO-d6, 150 MHz)  =
153.8 (Cq-2), 142.3 (Cq-4), 138.3 (Cq-3'), 135.9 (Cq-1"), 133.8 (Cq-8"), 129.8 (Cq-3"), 128.8 (CH-
7"), 128.1 (CH-9"), 128.1 (CH-4'), 126.2 (CH-5"), 125.7 (CH-6"), 125.4 (CH-10"), 125.3 (CH-
2"), 123.9 (Cq-5'), 123.5 (CH-4"), 120.2 (Cq-2'), 102.2 (CH-5), 38.2 (CH-6). – (+)-ESIMS m/z
389 ([M-H]-, 100), 391 ([M-H+2]-, 66), 393 ([M-H+4]-, 17). – (+)-HRESIMS m/z 390.9890
[M+H]+, 392.9861 [M+H+2]+, 394.9833 [M+H+4]+, (calcd for C18H13Cl2N2S2, 390.9892).
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Biological screening test
The in vitro antibacterial activity of the newly synthesized compounds (chalcones 5d-f, h and
thiazines 6a-g) was carried out against 24h old cultures of E. coli, S. aureus and B. subtilis
bacterial species, whereas the antifungal activity was carried out against 48h old culture of C.
albicans, and A. niger spore suspension using well diffusion method at concentrations of 100
µg/mL in DMSO[56]. Nutrient agar and potato dextrose agars were used to culture the bacteria
and fungi, respectively. The plates were inoculated by the bacteria or fungi and incubated for 24h
at 37 ºC for bacteria and for 72h at 27 ºC for fungi. Simultaneously, cefaclor (S1) and
cefuroxime (S2) at concentrations 100 µg/mL was used as standard against bacteria while
fluconazole at the same concentration was used as standard antifungal agents.
Conclusion
Several novel structures of chalcones and thiazine heterocycles have been successfully
synthesized. All compounds were characterized using different spectroscopic methods. The
antimicrobial test of all new compounds was carried out against bacteria and fungi, which shows
significantly better antibacterial activities compared to standard antibiotics.
Acknowledgements
We are grateful to Al al-Bayt University (Mafraq, Jordan) and the DFG (Germany) for
financial support.
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