The structures of 8- and 10-trifluoromethylquino[3,2-b]-benzo[1,4]thiazines and their benzyl derivatives

Article abstract of DOI:10.3987/COM-12-12528

The modification of the phenothiazine structure via the substitution of the benzene ring with the quinoline ring may proceed through the Ullmann cyclization or the Smiles rearrangement of the appropriate sulfides followed by cyclization. Reactions of 2,2'

Full text of DOI:10.3987/COM-12-12528

HETEROCYCLES, Vol. 85, No. 9, 2012
2281
HETEROCYCLES, Vol. 85, No. 9, 2012, pp. 2281 - 2290. © 2012 The Japan Institute of Heterocyclic Chemistry
Received, 18th June, 2012, Accepted, 17th July, 2012, Published online, 25th July, 2012
DOI: 10.3987/COM-12-12528
THE STRUCTURES OF 8- AND 10-TRIFLUOROMETHYLQUINO[3,2-b]-
BENZO[1,4]THIAZINES AND THEIR BENZYL DERIVATIVES†
Małgorzata Jeleń,a Kinga Suwińska,b Céline Besnard,c Krystian Pluta,a* and
Beata Morak-Młodawskaa
aDepartment of Organic Chemistry, The Medical University of Silesia,
Jagiellońska 4, 41-200 Sosnowiec, Poland, bInstitute of Physical Chemistry of the
Polish Academy of Sciences, Kasprzaka, 44/52, 01 224 Warszawa, and Faculty of
Biology and Environmental, Sciences, Cardinal Stefan Wyszyński University,
Wóycickiego 1/3, 01 938 Warszawa, Poland. cLaboratoire de Crystallographie,
University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switherland.
E-mail: pluta@sum.edu.pl
Abstract – The modification of the phenothiazine structure via the substitution of
the benzene ring with the quinoline ring may proceed through the Ullmann
cyclization or the Smiles rearrangement of the appropriate sulfides followed by
cyclization. Reactions of 2,2’-dichloro-3,3’-diquinolinyl disulfide or pentacyclic
diquinodithiin with m-trifluoromethylaniline led to two isomeric tetracyclic
trifluoromethylquinobenzothiazines. The product structures as the appropriate
6H-X-trifluoromethylquino[3,2-b]benzo[1,4]thiazines (X = 8, 10) were finally
confirmed by X-ray analysis (one product was transformed into N-benzyl
derivative). These results exclude the possibility of the reverse Smiles
rearrangement and the existence of 5H-tautomers in these conditions. Although
both compounds have the same quinobenzothiazine system, they differ in the
spatial structures and geometric data. Molecule 6b is unexpectedly almost planar
that is the result of larger than usual the C–S–C and C–N–C angles in the thiazine
ring. Molecule 14 is folded along the S–N axis with the thiazine ring in boat
conformation and the benzyl group in equatorial position.
Phenothiazines are known mainly as recognized antipsychotic, antihistaminic, antitussive and antiemetic
drugs.1 Recent reports deal with very promising anticancer and antibacterial activities, reversal of

2282
HETEROCYCLES, Vol. 85, No. 9, 2012
multidrug resistance and potential treatment in Alzheimer’s and Creutzfeldt-Jakob diseases not only for
classical but also for newly synthesized phenothiazines.2-6 The phenothiazine structures were modified by
the introduction of new pharmacophoric substituents at the thiazine nitrogen atom and the substitution of
the benzene ring with an azine ring. In continuation of our search for new anticancer and
immunosuppressive azaphenothiazines containing azine rings (pyridine and quinoline)7-12 we synthesized
tetracyclic quinobenzothiazines in original way from 2,2’-dichloro-3,3’-diquinolinyl disulfide 1 or
pentacyclic diquinodithiin 2 in the reactions with various substituted anilines 3 (Scheme 1).13 The reaction
ran through the formation of anilinium quinolinethiolate 4 which underwent the thiazine ring formation to
quino[3,2-b]benzo[1,4]thiazines 5, the only product in the reaction with p-substituted anilines (Z1 = Z3 = X
= H). In the case of the reaction with m-substituted anilines 3 (m-chloroaniline, m-bromoaniline,
m-trifluoromethylaniline, Z1 = Cl, Br, CF3, Z2 = Z3 = X = H) additional quinobenzothiazines 6 were also
observed as the result of two ways of the thiazine ring formation. Anilinium quinolinethiolate 4 can
undergo the Smiles rearrangement to sulfide 11 which can give quinobenzothiazines 12 and 13. When
o-chloroanilines 3 (X = Cl) were used, the reaction ran through the formation of sulfide 7 which could give
quinobenzothiazines 8 or could undergo the Smiles rearrangement to amine 9 and further to
quinobenzothiazines 10.
N
S
S S
or
Z1
Z2
S
S
2
N
N
Cl Cl
1
N
N
N
13
NH2
H
+
X
S
Z3
Z1
Z2
3
m- and p-substituted
anilines
o-chloroanilines
Z2
N
H
N
12
X = Cl, Z2 = H
X = H, Z3 = H
S
Z1
Z1
Z1
Z1
S
Z2
S
S
o
N
+
S
Z3
Z3
N
N
N
N
H
N
8
Z2
H2N
N
11
NH
H
H
2 Cl
4
7
Z1
o
N
S
Z1
H
H
Z2
Z2
Z1
S
S
Z3
S
N
Z3
N
H
N
5
N
H
N
6
N
H
N
10
SCl
N
9
Z1
Z1
Z1
H
Z2
H
H
Z1
H
Cl
H
Z2
5a 6a
5b/6b
5c/6c
=
8a = 10a
H
H
Cl
CF3 (Cl, Br)
H
8b 10b
/
8c/9c
Cl
Scheme 1

HETEROCYCLES, Vol. 85, No. 9, 2012
2283
We found the products with m-chloroaniline to be the same as those with 2,3- and 2,5-dichloroanilines, and
therefore we assigned them as 8-chloro- and 10-chloroquino[3,2-b]benzo[1,4]thiazines 5b and 6b,
respectively. The kind of fusion of the thiazine ring with the quinoline ring [3,2-b] in obtained
quinobenzothiazines was confirmed by homonuclear NOE experiment for the 6-methyl derivative. A
discrimination of 8-substituted and 10-substituted quinobenzothiazines was based on the 1H NMR analysis
of the benzene ring proton signals (as 1,2,4- and 1,2,3-trisubstituted benzenes, respectively) and their
13
coupling constants Jortho and Jmeta
.
Phenothiazines with biological activities are obtained most often from N-unsubstituted phenothiazines in
N-alkylation reactions. Such alkylations mainly occurred at the thiazine nitrogen atom but there are some
evidences that the azine nitrogen atom, sulfur atom or even carbon atom were also alkylated, even in basic
conditions.14-16 A ring contraction was also observed during alkylation.17 As biological activities of
phenothiazines depend on their structures, configurations and conformations, especially on the nature of the
substituent at the thiazine nitrogen atom, the place of additional substituents, and on the nature of the
phenothiazine and azaphenothiazine ring system, it is obvious the structures of phenothiazines should be
determined without any doubts. The proper determination of the phenothiazine products is difficult as the
Smiles rearrangement, which is widespread during synthesis via appropriate sulfide, is not always easy to
observe.15-17 The aim of this paper is to confirm unequivocally the kind of fusion of the quinoline ring with
thiazine ring and proper discrimination of the two isomeric trifluoromethylquinobenzothiazines, to verify
the place of the hydrogen atom (Nthiazine–H or Nquinoline–H) and an alkyl substituent at the nitrogen atom, and
finally to find out about planar or folded tetracyclic quinobenzothiazine ring system.
Synthesis and the product structures
The reaction of disulfide 1 or diquinodithiin 2 with m-trifluoromethylaniline 3a (or its hydrochloride) in
o
o
boiling monomethyl ether of diethylene glycol (MEDG) at 194 C or without solvent at 200–205 C,
o
o
respectively, led to two products with melting points of 225–226 C and 219–220 C assigned as
trifluoromethylquinobenzothiazines 5b and 6b13 but other tautomeric structures 5c and 6c should be also
taken into consideration. On the other hand intermediate 4a can undergo the reverse Smiles rearrangement
to sulfide 10 and further to trifluoromethylquinobenzothiazines 5d and 6d or their tautomers 5e and 6e
(Scheme 2).
The direct reaction products were changed into N-benzyl derivatives in 81% and 86% yield in the model
alkylation reaction with benzyl chloride in DMF in the presence of sodium hydride. As we found that
N-substituted quinobenzothiazines with pharmacophoric aminoalkyl groups exhibited very promising
antiproliferative and anticancer activities,18 this model benzylation showed which nitrogen atom underwent
alkylation.

2284
HETEROCYCLES, Vol. 85, No. 9, 2012
For X-ray study, we obtained proper quality monocrystals of the direct product of higher melting point. The
monocrystal quality of the second product (of lower melting point) was insufficient, therefore this com-
pound was transformed into N-benzyl derivative. X-Ray study confirmed the correctness of the assumed
structures of 6H-8-trifluoromethylquino[3,2-b]benzo[1,4]thiazine 6b and 6-benzyl-10-trifluoromethyl-
quino[3,2-b]benzo[1,4]thiazine 14 and proved that the model N-benzyl reactions occurred at the thiazine
nitrogen atom (giving compounds 14 and 15). These results exclude the possibility of the reverse Smiles
rearrangement and the existence of 5H-tautomers in these conditions.
CF3
S S
S
S
+
F3C
N
Cl Cl
1
N
N
N
H
N
N
H
6c
NH2
5c
CF3
3a
CF3
CF3
S
S
S
+
F3C
N
H
N
5b
N
H
N
6b
N
N
4a
H
H
o
S
S
F3C
+
S
N
H
N
H2N
CF3
N
11a
N
H
N
CF3
5d
6d
S
F3C
S
+
N
N
H
5e
N
N
H
6e
CF3
Scheme 2
X-Ray analysis
The isomeric trifluoromethylquinobenzothiazine systems have different spatial structures. Contrary to all
known structures of tricyclic phenothiazins, molecule 14 and other tetracyclic compounds i.e. dihydro-
quinobenzothiazine 1619 and naphthobenzothiazine 1720 (Scheme 3), molecule 6b is unexpectedly almost
planar (Figure 1). The dihedral angle between the halves of the thiazine ring (N6/C5a/C11a/S11 vs.
N6/C6a/C10a/S11) and between the benzene ring and quinoline ring (C6a/C7/C8/C9/C10/C10a vs.

HETEROCYCLES, Vol. 85, No. 9, 2012
2285
C1/C2/C3/C4/C4a/N5/C5a/C11a/C12/C12a) are 171.86(10)o and 174.02(8)o, respectively. We found only
one case in literature when the phenothiazine structure was planar, despite some complexes with inorganic
and organic compounds. Out from two reported structures of related linear fused azaphenothiazines
possessing two quinoline rings instead of the benzene rings, pentacyclic 6-phenyldiquinothiazine 18 was
folded but 6-(p-nitrophenyl)diquinothiazine 19 was unexpected planar due to the interaction of the thiazine
nitrogen atom with electron-withdrawing p-nitrophenyl group.21,22
The similar dihedral angles in molecule 14 are 139.20(9)o and 145.97(6)o, respectively. The thiazine ring is
in boat conformation and the benzyl group is located in equatorial position with the S11···N6–C17 angle of
163.8(2)o and torsion angles C10a–C6a–N6–C17 and C11a–C5a–N6–C17 of -164.4(2)o and 168.1(2)o. The
benzyl group is turned around the N6–C17 bond (the torsion angles C5a–N6–C17–C18 and
CF3
S
S
S
S
S
F3C
N
N
R
N
N
N
N
H
N
N
N
N
CH2
CH2
CH3
16
R
17
18 C6H5
19
C6H4NO2
15
14
Scheme 3
a
b
Figure 1. ORTEP drawings: (a) 6H-8-trifluoromethylquino[3,2-b]benzothiazine 6b; (b) 6-benzyl-8-triflu-
oromethylquino[3,2-b]benzothiazine 14
C6a–N6–C17–C18 of -133.4(2)o and 68.2(3)o) and less turned around the C17–C18 bond (the torsion
angles N6–C17–C18–C19 and N6–C17–C18–C23 of -164.4(2)o and 26.1(3)o). The phenyl group plane

2286
HETEROCYCLES, Vol. 85, No. 9, 2012
(C18/C19/C20/C21/–C22/C23) is rather perpendicular to the C5a/C6a/C10a/C11a plane with the angle of
112.89(9)o.
Whereas the thiazine ring is symmetrical with similar S–C (1.753(2) and 1.754(2) Å) and N–C bond lengths
(1.388(2) and 1.377(2) Å), the pyridine ring is distorted with different C–C (1.355(3) vs. 1.432(2) Å) and
a
b
Figure 2. Intermolecular interactions in 6-benzyl-8-trifluoromethylquino[3,2-b]benzothiazine 14 crystal
structure: (a) dimer formation; (b) C–H···π interactions.
a
b
Figure 3. Crystal packing shown along the b axis in: (a) 6H-8-trifluoromethylquino[3,2-b]benzothiazine
6b; (b) 6-benzyl-8-trifluoromethylquino[3,2-b]benzothiazine 14
N–C bond lengths (1.303(2) Å vs. 1.373(2) Å). The C–N–C and C–S–C angles in the thiazine ring are
significantly large (128.22(15)o and 103.31(9)o) in molecule 6b in comparison with appropriate angles in
molecule 14 (120.9(2)o and 98.78(12)o, what enables the thiazine ring to be almost planar. It is worth noting
that the same angles in planar similar structure 19 are also large (125.7(4)o and 102.6(3)o) but in folded

HETEROCYCLES, Vol. 85, No. 9, 2012
2287
structure 18 are smaller (123.8(2)o and 100.1(2)o, respectively).21,22 Similarly to compound 6b, the thiazine
ring in compound 14 is quite symmetrical (with the S–C bond lengths of 1.759(3) and 1.768(3) Å, and with
the N–C bond lengths of 1.408(3) and 1.411(3) Å), but the pyridine ring is distorted with different the C–C
(1.360(4) vs 1.429(4) Å) and N–C bond lengths (1.306(4) Å vs. 1.377(3) Å).
The electron-withdrawing trifluoromethyl group in compounds 6b and 14, similarly to the p-nitrophenyl
group in compound 19, reduces the electron density at the thiazine nitrogen atom what makes possible to
take a planar conformation of the thiazine ring and thereby the whole molecule 6b. In case of molecule 14,
the electron-withdrawing action of the trifluoromethyl group is compensated by the electron-donating
action of the benzyl group. The sum of three C–N6–C angles is 356.21° indicating nearly pyramidal
configuration of the bonds around the central nitrogen atom.
Two molecules 14 related by crystallographic center of symmetry are arranged in dimers via two C–H···F
hydrogen bonds [dH···F = 2.56 Å, dC···F = 3.394 Å, <C–H···F = 146.8 ° (Figure 2a). Each molecule interacts
with neighboring three molecules with C–H··· interactions (Figure 2b). Additionally, in the crystal
structure,  interactions between the quinoline moieties of the adjacent molecules are observed. The
stacking propagates along c crystallographic axis.
Figure 3 shows crystal packing along the b axis for both crystal structures.
The trifluoromethyl group rotates very fast in molecule 6b and is coplanar with the benzene ring as the
torsion angles C13/C8/C9/C10 and C6a/C7/C8/C13 are -179.5(2)o and 179.76(18)o, respectively.
The CF3 group is disordered in molecule and was modelled using two components, whose geometry was
restrained to be the same. Restrains were also applied on anisotropic displacement parameters.
X-Ray study confirmed the right structures of 6H-8-trifluoromethylquino[3,2-b]benzo[1,4]thiazine 6b and
6H-10-trifluoromethylquino[3,2-b]benzo[1,4]thiazine 5b (concluded from the 1H NMR study) as the direct
reaction products which exist as the 6H-tautomers. The structure of 6-benzyl-10-trifluoromethylquino-
[3,2-b]benzothiazine 14 proved that the model N-benzyl reaction occurred at the thiazine nitrogen atom.
These results exclude the possibility of the reverse Smiles rearrangement and the existence of the
5H-tautomers in these conditions. Although both compounds have the same quinobenzothiazine system,
they differ in geometric data and molecule 6b is unexpectedly almost planar. The thiazine ring in molecule
14 is in boat conformation with the benzyl group in equatorial position. The planarity of the thiazine ring in
molecule 6b is the result of larger than usual the C–S–C and C–N–C angles.
EXPERIMENTAL
Melting points were determined in open capillary tubes on a Boetius melting point apparatus and were
1
uncorrected. The H NMR spectra were recorded on a Bruker AV III spectrometers at 500 MHz in

2288
HETEROCYCLES, Vol. 85, No. 9, 2012
deuteriochloroform with tetramethylsilane as the internal standard. Electron impact (EI MS) mass spectra
were run on a Finnigan MAT 95 spectrometer at 70 eV. The Ir spectra were recorded on a Shimadzu
IR-Affinity-1 FT-IR spectrophotometer.
General synthesis of 6H-8-trifluoromethylquino[3,2-b]benzo[1,4]thiazine 6b and 6H-10-trifluoro-
methylquino[3,2-b]benzo[1,4]thiazine 5b
The reaction of disulfide 2 (0.20g, 0.5 mmol) with m-trifluoromethylaniline 3a (2 mmol) in boiling
monomethyl ether of diethylene glycol (5 mL) was carried out as described previously.13 The column
chromatography separation (silica gel, CHCl3) gave two products:
o
a. 6H-8-Trifluoromethylquinobenzothiazine 6b (0.11 g, 34%), mp 225–226 C, Rf = 0.65 (Al2O3,
CH2Cl2),
o
b. 6H-10-trifluoromethylquinobenzothiazine 5b (0.09 g, 28%), mp 219–220 C, Rf = 0.58 (Al2O3,
CH2Cl2).
The same products were obtained in 28% and 22% yield in the reaction of diquinodithiin 1 with
hydrochloride of m-trifluoromethylaniline 3a in an oil bath at 200–205 oC.13
Synthesis of 6-benzyl-10-trifluoromethylquino[3,2-b]benzothiazine 14 and 6-benzyl-8-trifluorome-
thylquino[3,2-b]benzothiazine 15
To a solution of 10-trifluoromethylquinobenzothiazine 5b or 8-trifluoromethylquinobenzothiazine 6b
(0.32 g, 1 mmol) in dry DMF (10 mL) sodium hydride (0.24 g, 10 mmol, washed out from mineral oil
with hexane) was added. The reaction mixture was stirred for 1 h in room temperature. Then benzyl
chloride (0.35 mL, 3 mmol) was added and the stirring was continued for 24 h. The reaction mixture was
poured into water (40 mL) and extracted with CH2Cl2. The extract was washed with water, dried with
anhydrous sodium sulfate. The drying agent was filtered off and the solution was evaporated in vaccuo.
The residue was purified by column chromatography (Al2O3, CH2Cl2) to give 6-benzyl-10-trifluorome-
o
thylquino[3,2-b]benzothiazine 14 (0.18 g, 86%), mp 127–128 C (EtOH) or 6-benzyl-8-trifluoromethyl-
quino[3,2-b]benzothiazine 15 (0.17 g, 81%), mp 115–116 oC (EtOH).
1
6-benzyl-10-trifluoromethylquinobenzothiazine 14 H NMR (CDCl3) : 5.60 (s, 2H, CH2), 6.97 (d, 1H,
H7), 7.07 (t, 1H, H8), 7.23 (m, 1H, H2), 7.24 (d, 1H, H9), 7.31 (m, 3H, C6H3), 7.38 (m, 2H, C6H2), 7.51
(m, 2H, H3), 7.58 (m, 1H, H1), 7.69 (m, 1H, H4), 7.83 (s, 1H, H12). EI MS m/z: 408 (M, 63), 317
(M-CH2C6H5, 100). Ir (KBr): 1130.33, 1309.72, 1399.42 cm-1. Anal. Calcd for C23H15F3N2S: C 67.64, H
3.70, N 6.86. Found: C 67.44, H 3.83, N 6.76.
1
6-benzyl-8-trifluoromethylquinobenzothiazine 15 H NMR (CDCl3) : 5.60 (s, 2H, CH2), 6.98 (d, 1H,
H7), 7.09 (dd, 1H, H9), 7.15 (d, 1H, H10), 7.23 (m, 1H, H2), 7.31 (m, 3H, C6H3), 7.39 (m, 2H,
C6H2),7.50 (m, 2H, H3), 7.54 (m, 1H, H1), 7.70 (s, 1H, H12), 7.72 (m, 1H, H4). EI MS m/z: 408 (M, 55),
317 (M-CH2C6H5, 100). Ir (KBr): 1119.73, 1324.19, 1406.70 cm-1. Anal. Calcd for C23H15F3N2S: C 67.64,

HETEROCYCLES, Vol. 85, No. 9, 2012
2289
H 3.70, N 6.86. Found: C 67.41, H 3.85, N 6.69.
X-Ray analysis of 6H-8-trifluoromethylquino[3,2-b]benzothiazine 6b and 6-benzyl-8-trifluorome-
thylquino[3,2-b]benzothiazine 14
A. A yellow crystal of compound 6b (dimensions: 0.40 × 0.30 × 0.04 mm) was grown from
ethanol-chloroform solution at room temperature. Crystallographic data were collected at 260 K on a Stoe
IPDS diffractometer with graphite monochromated MoKα radiation (λ = 0.71073 Å). The structure was
solved by direct methods (SHELXS-86)23 and refined by full-matrix least-squares minimization based on
all unique F2 (SHELXL).24 Crystal data: C16H9F3N2S, Mr = 318.32, monoclinic, a = 7.6423 (9), b =
6.0471 (4), c = 28.940 (3) Å, β = 97.60 (1)°, space group P21/c, V = 1325.7 (2) Å3, Z = 4,  = 0.28 mm−1.
The crystal system is monoclinic but the system could be indexed using an orthorombic unit-cell with
parameters a = 7.665, b = 57.331, c = 6.054 Å. This cell is the result of a perfect superposition of two
monoclinic twins with twin law [1 0 0, 0 -1 0 ,-1 0 -1]. The twin law was included in the refinement and
the twin fraction refined to 0.53 /0.47. 7878 reflections were collected of which 2593 were independent
and 2337 reflections with I > 2σ(I) (Rint = 0.039). The structure was refined to R[F2 > 2σ(F2)] = 0.031 and
wR(F2) = 0.077. H-atoms were included in geometric positions and refined as 'riding' atoms with isotropic
thermal parameters based upon the corresponding bonding carbon atom [Uiso = 1.2Ueq].
B. A yellow crystal of compound 14 (dimensions: 0.15 × 0.20 × 0.30 mm) was grown from
ethanol-chloroform solution at room temperature. Crystallographic data were collected at 100 K on a
Kappa ApexII diffractometer with graphite monochromated MoKα radiation (λ = 0.71073 Å). The structure
was solved by direct methods (SHELXS-97)25 and refined by full-matrix least-squares minimization based
on all unique F2 (SHELXL-97).26 Crystal data: C23H15F3N2S, Mr = 3408.44, monoclinic, a = 16.7752 (6), b
= 16.2145 (7), c = 7.0434(2) Å, β = 99.971(2)°, space group P21/c, V = 1884.3 (2) Å3, Z = 4,  = 0.212 mm−1.
24702 reflections were collected of which 3208 were independent and 2503 reflections with I > 2σ(I) (Rint =
0.042). The structure was refined to R[F2 > 2σ(F2)] = 0.049 and wR(F2) = 0.100. H-atoms were included in
geometric positions and refined as 'riding' atoms with isotropic thermal parameters based upon the
corresponding bonding carbon atom [Uiso = 1.2Ueq].
ACKNOWLEDGEMENTS
The work is supported by the National Centre of Science (grant N N405 101739).
REFERENCES (AND NOTES)
† Part CXXVIII in the series of Azinyl Sulfides.
1. R. R. Gupta and M. Kumar, ‘Synthesis, properties and reactions of phenothiazines’, in R. R. Gupta
(Eds.) ‘Phenothiazines and 1,4-Benzothiazines – Chemical and Biological Aspects’. Elsevier, 1988,

2290
HETEROCYCLES, Vol. 85, No. 9, 2012
p. 1.
2. N. Motohashi, M. Kawase, S. Saito, and H. Sakagami, Curr. Drug Targets, 2000, 1, 237.
3. N. Motohashi, M. Kawase, K. Satoh, and H. Sakagami, Curr. Drug Targets, 2006, 7, 1055.
4. K. Pluta, B. Morak-Młodawska, and M. Jeleń, Eur. J. Med. Chem., 2011, 46, 3179.
5. J. J. Aaron, M. D. Gaye Seye, S. Trajkovska, and N. Motohashi, ‘Bioactive Phenothiazines and
Benzo[a]phenothiazines: spectroscopic studies and biological and biomedical properties and
applications’, Top Heterocycl. Chem., Springer-Verlag, Berlin, 2009, 16, 153.
6. A. Dasgupta, S. G. Dastridara, Y. Shirataki, and N. Motohashi, ‘Antibacterial activity of artificial
phenothiazines and isoflavones from plants’, Top Heterocycl. Chem., Springer-Verlag, Berlin, 2008,
15, 67.
7. B. Morak and K. Pluta, Heterocycles, 2007, 71, 1347.
8. M. Jeleń and K. Pluta, Heterocycles, 2008, 75, 859.
9. B. Morak-Młodawska and K. Pluta, Heterocycles, 2009, 78, 1289.
10. M. Zimecki, J. Artym, M. Kocięba, K. Pluta, B. Morak-Młodawska, and M. Jeleń, Cell. Mol. Biol.
Lett., 2009, 14, 622.
11. K. Pluta, M. Jeleń, B. Morak-Młodawska, M. Zimecki, J. Artym, and M. Kocięba, Pharmacol.
Reports, 2010, 62, 319.
12. B. Morak-Młodawska, K. Suwińska, K. Pluta, and M. Jeleń, J. Mol. Struct., 2012, 1015, 94.
13. M. Jeleń and K. Pluta, Heterocycles, 2009, 78, 2325.
14. T. Itoh, Y. Tomii, T. Noitoh, M. Yamamura, I. Ishikawa, N. Kawahara, Y. Mizuno, and H. Ogura,
Chem. Pharm. Bull., 1989, 37, 2197.
15. K. Pluta, B. Morak-Młodawska, and M. Jeleń, J. Heterocycl. Chem., 2009, 46, 355.
16. W. Schindler and J. Peterli, U. S. Patent 3,010,961, 1961.
17. G. Riedel and W. Deuschel, British Patent 971,048, 1964.
18. K. Pluta, M. Jeleń, M. Zimecki, B. Morak-Młodawska, J. Artym, and M. Kocięba, Polish Patent
Appl. P-398835, 2012.
19. R. L. Luck, K. Li, and D. K. Bates, Acta Cryst., 2003, E59, o302.
20. S. Yoshida, K. Kozawa, N. Sato, and T. Uchida, Bull. Chem. Soc. Jpn., 1994, 67, 2017.
21. K. Pluta, M. Nowak, and K. Suwińska, J. Chem. Cryst., 2000, 30, 479.
22. M. Nowak, K. Pluta, K. Suwińska, and L. Straver, J. Heterocycl. Chem., 2007, 44, 543.
23. G. M. Sheldrick, SHELS-86, Program for crystal solution, University of Göttingen, Germany.
24. G. M. Sheldrick, SHELSXL, Acta Cryst., 2008, A64, 112.
25. G. M. Sheldrick, SHELS-97, Acta Cryst., 1990, A46, 467.
26. G. M. Sheldrick, SHELX97. Programs for Crystal Structure Analysis (Release 97-2). University of
Göttingen, 1997, Germany.