Fused polycyclic nitrogen-containing heterocycles: VIII. Friedel-Crafts intramolecular cyclization of 5-phenylthiazole-4-carboxylic acids - A new route to indeno[2,1-d]thiazoles

Article abstract of DOI:10.1023/B:RUJO.0000036076.65278.fe

Friedel-Crafts intramolecular cyclization in the presence of polyphosphoric acid of 2-substituted 5-phenylthiazole-4-carboxylic acids, which are obtained by alkaline hydrolysis of the corresponding esters, leads to indeno[2,1-d]thiazoles. According to the

Full text of DOI:10.1023/B:RUJO.0000036076.65278.fe

Russian Journal of Organic Chemistry, Vol. 40, No. 4, 2004, pp. 534–542. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 4, 2004,
pp. 564–571.
Original Russian Text Copyright © 2004 by Mamedov, Gubaidullin, Nurkhametova, Litvinov, Levin.
Fused Polycyclic Nitrogen-Containing
Heterocycles: VIII.* Friedel–Crafts Intramolecular Cyclization
of 5-Phenylthiazole-4-carboxylic Acids—A New Route
to Indeno[2,1-d]thiazoles
V. A. Mamedov, A. T. Gubaidullin, I. Z. Nurkhametova,
I. A. Litvinov, and Ya. A. Levin
Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center, Russian Academy of Sciences,
ul. Arbuzova 8, Kazan, 420088 Tatarstan, Russia
e-mail: mamedov@iopc.kcn.ru
Received May 6, 2002
Abstract—Friedel–Crafts intramolecular cyclization in the presence of polyphosphoric acid of 2-substituted
5-phenylthiazole-4-carboxylic acids, which are obtained by alkaline hydrolysis of the corresponding esters,
leads to indeno[2,1-d]thiazoles. According to the X-ray diffraction data, packing of their molecules in crystal is
determined mainly by intermolecular π–π contacts, regardless of the substituent nature.
Compounds of the thiazole and benzothiazole series
possess a variety of useful properties, in particular
pharmacological activity. They are widely used as vul-
canization accelerators and antioxidants [2], photo-
chromic compounds [3], and dyes, as well as in manu-
facture of polymeric materials [4]. Unlike thiazoles
and benzothiazoles, specific structural features of
indenothiazoles, arising from the existence of skeletal
isomers, make them convenient models for solving not
only practical but also theoretical problems. However,
not all theoretically possible structural isomers of
indenothiazoles, differing by mutual arrangement of
the thiazole ring and indene system, have been studied
in sufficient detail. For example, only a few published
data are available on indeno[2,1-d]thiazoles [5, 6], in
contrast to isomeric indeno[1,2-d]thiazoles for which
not only various simple synthetic procedures have
been developed but also some practical aspects have
been explored [4]. Presumably, the reason is that most
known methods for the preparation of indenothiazoles
are based on fusion of a thiazole ring to indene deriva-
tives [7–12] rather than vice versa.
Retrosynthetic approach [13, 14], which was suc-
cessfully applied by us to the synthesis of various
fused heterocyclic systems, showed that the indeno-
[2,1-d]thiazole structure could be built up from
thiazole derivatives through synthon A (Scheme 1);
equivalents of the latter are accessible 2-substituted
5-phenylthiazole-4-carboxylic acid esters [15, 16].
Scheme 1.
R
S
N
O
MeO
N
N
R
R
S
S
N3
S1
2
2
4
7
8
3a
8b
3b
8a
4a
5
6
7
6
S1
N3
A
8a
3a
7a
4
The location of the ester and phenyl groups at C4
and C5 of the thiazole ring, respectively, is spatially
favorable for their interaction. However, such inter-
action requires that at least one of these groups be
8
5
8H-Indeno[1,2-d]thiazole
4H-Indeno[2,1-d]thiazole
* For communication VII, see [1].
1070-4280/04/4004-0534 © 2004 MAIK “Nauka/Interperiodica”

535
FUSED POLYCYCLIC NITROGEN-CONTAINING HETEROCYCLES: VIII.
Scheme 2.
O
O
R
S
MeO
HO
(1) KOH
(2) HCl
PPA
N
N
N
–H2O
R
R
S
S
O
Ia–Ic
IIa–IIc
IIIa–IIIc
O
H
H
O
O
O
C
C
–H2O
PPA
IIa–IIc
N
N
N
Ph
Ph
Ph
R
R
R
S
S
S
O
O
H
C
N
N
IIIa–IIIc
–H+
R
R
S
S
I–III, R = H (a), Me (b), Ph (c).
activated. In the present work we effected conversion
of 2-substituted 5-phenylthiazole-4-carboxylic acid
esters Ia–Ic into the corresponding acids and intra-
molecular cyclization of the latter through highly elec-
trophilic acyl cation which was generated in situ by the
action of polyphosphoric acid (PPA).
solution of potassium hydroxide in 2 h afforded
thiazole-4-carboxylic acids IIa–IIc. The latter were
subjected to intramolecular acylation according to
Friedel–Crafts [17] in the presence of PPA to obtain
indeno[2,1-d]thiazol-4-ones IIIa–IIIc (Scheme 2). The
structure of products IIIa–IIIc follows from the data
of IR and NMR (1H and 13C) spectroscopy (Tables 1
and 2). The IR specta of IIIa–IIIc lack absorption
Alkaline hydrolysis of methyl 5-phenylthiazole-4-
carboxylates Ia–Ic in a boiling aqueous–methanolic
Table 1. IR (mineral oil) and 1H NMR spectra [CD3OD–(CD3)2CO, 1:1] of compounds IIa–IIc and IIIa–IIIc
Comp.
no.
IR spectrum, ν, cm–1
1H NMR spectrum, δ, ppm (J, Hz)
3080, 3000–2500 (a series of bands), 1690 (C=O), 970, 7.27–7.63 m (5H, C6H5), 8.95 s (1H, thiazole)
945, 860
IIa
3050–2500 (a series of bands), 1700 br (C=O), 1580, 2.67 s (3H, CH3), 7.21–7.57 m (5H, C6H5)
1480, 1440, 1380, 1310, 1300, 1280, 1245, 1210, 1130,
980, 935
IIb
IIc
3150–2450 (a series of bands), 1690 (C=O), 1620, 1610, 7.23–8.37 m (10H, 2C6H5)
1590, 1525, 1445, 1350, 1320, 1285, 1260, 1225, 1085,
1005, 925
3070 (narrow band), 1710 (C=O), 1600, 1350, 1290, 7.30–7.51 m (4H, C6H4), 9.10 s (1H, thiazole)
1250, 1160, 1080, 980, 890, 830, 810, 755, 720
IIIa
IIIb
1705 (C=O), 1600, 1495, 1350, 1155, 1030, 860, 765, 2.75 s (3H, CH3), 7.12 d (1H, 5-H or 8-H, J = 7.63),
725
7.22 d.d.d (1H, 6-H or 7-H, J = 7.62, 7.00, 1.27),
7.36 d.d.d (1H, 7-H or 6-H, J = 7.52, 7.62, 1.28),
7.43 d (1H, 8-H or 5-H, J = 7.63)
1710 (C=O), 1600, 1355, 1160, 1085, 1035, 1015, 935, 7.30–8.05 m (7H, C6H4 + C6H5)
860
IIIc
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

536
MAMEDOV et al.
Table 2. 13C NMR spectra of indeno[2,1-d]thiazol-4-ones IIIa–IIIc (DMSO–DMSO-d6, 4:1), δC, ppm (J, Hz)
Comp.
no.
C2
C3a
C4
C4a
C5 or C8
159.05 d
(J = 219.6)
155.12 br.s
184.29 br.s
135.26 d.d.d.d
(J = 8.9, 8.2, 1.5, 1.2)
138.88 d.d (J = 163.9, 7.4),
129.76 d.d (J = 65.9, 6.7)
IIIa
171.10 q
(J = 7.5)
155.21 br.s
157.74 s
184.30 d
(J = 5.7)
135.88 d.d.d
(J = 7.7, 7.6, 1.1)
129.51 d.d (J = 165.1, 6.8),
134.73 d.d (J = 163.1, 6.8)
IIIb
IIIc
173.09 d.d.d
(J = 5.2, 4.0, 1.3)
185.58 br.d
(J = 2.9)
136.83 d.d.d
(J = 7.8, 7.6, 1.6)
136.07 d.d (J = 164.5, 6.9),
130.99 d.d (J = 165.3, 7.1)
Comp.
no.
C6 or C7
C8a
C8b
Substituent
–
123.58 d.br.d (J = 164.5, 8.4),
134.42 m
156.46 d
IIIa
121.83 d.d.d (J = 165.58, 8.1, 1.5)
(J = 14.8)
133.90 d.d
(J = 7.1, 7.0)
155.22 s
19.39 q (J = 130.57)
IIIb
123.98 d.d (J = 164.2, 8.6),
121.22 d.d (J = 166.2, 8.6)
124.63 d.d.d (J = 164.5, 7.3, 1.1),
122.76 d.d.d (J = 166.7, 7.1, 1.2)
135.35 d.d.d
(J = 6.8, 6.6, 1.4) (J = 4.3)
155.72 d
134.04 m (Ci), 127.68 d.m (Co, J = 160.6),
130.55 d.d.d (Cm, J = 133.8, 6.8, 6.1),
132.25 d.d.d (Cp, J = 162.4, 7.4, 7.5)
IIIc
Table 3. Conditions of X-ray diffraction experiments and principal crystallographic parameters of compounds IIIa–IIIc
Parameter
IIIa
IIIb
IIIc
Color
Brown
Orange
Red
Crystal habit, mm
Prismatic
Prismatic
Rhombic
0.5×0.23×0.18
0.25×0.25×0.25
0.6×0.45×0.35
Formula
Molecular weight
Crystal system
Space group
a, Å
C10H5NOS
187.22
Monoclinic
C2/c
C11H7NOS
201.25
Rhombic
Pbca
C16H9NOS
263.32
Monoclinic
P21/a
11.094(5)
08.639(5)
17.286(8)
98.78(2)
1637.3
8
13.213(2)
08.156(5)
17.355(5)
90.00
1870.3
8
12.146(4)
13.606(6)
15.962(6)
112.35(3)
2440.3
8
b, Å
c, Å
β, deg
V, Å3
Z
d
calc, g/cm3
1.52
1.43
1.43
F(000)
768
832
1088
θ
max, deg
71.31
30.444
1584
74.11
27.018
1947
56.85
Absorption coefficient, cm–1
Total number of reflections
Number of reflections with F2 ≥ 3σ(F2)
Divergence factor R, %
wR, %
22.090
2767
1370
1433
2596
3.8
3.5
6.1
4.8
5.0
9.9
Fitting parameter S
1.9
1.8
4.4
Number of refined parameters
138
155
415
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

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FUSED POLYCYCLIC NITROGEN-CONTAINING HETEROCYCLES: VIII.
Table 4. Coordinates of atoms in the molecule of indeno[2,1-d]thiazol-4-one (IIIa), equivalent isotropic temperature factors
3
3
of non-hydrogen atoms B = 4/3 Σ Σ(aiaj)B(i, j) (Å2), and isotropic temperature factors of hydrogen atoms (Å2)
i = 1 j = 1
Atom
S1
O4
N3
C2
C3a
C4
C4a
C5
x
y
z
B
Atom
C7
C8a
C8b
C8
H2
H5
H6
H7
H8
x
y
z
B
–0.08864(4) 0.14384(5) 0.66384(2) 4.737(9)
–0.0087(2) 0.2941(2) 0.37663(9) 4.71(4)
–0.0917(1) 0.3043(2) 0.51189(8) 3.35(3)
–0.1222(1) 0.2725(2) 0.59642(8) 3.44(3)
–0.0148(2) 0.2330(2) 0.45180(9) 4.15(3)
–0.3019(1)
–0.2425(2)
–0.1883(2)
–0.2046(1)
–0.2342(2)
–0.1590(1)
–0.1513(2)
–0.0756(2)
0.6005(2) 0.58042(8) 5.18(3)
0.3629(2) 0.71035(8) 4.39(3)
0.2428(2) 0.73438(9) 4.79(4)
0.3791(2) 0.63143(8) 3.57(3)
0.4900(2) 0.57172(8) 3.67(3)
0.4355(2) 0.49676(8) 3.48(3)
0.4970(2) 0.42291(9) 4.28(3)
–0.195(2)
–0.188(2)
–0.074(2)
–0.036(2)
–0.028(2)
0.205(2)
0.595(2)
0.468(2)
0.244(2)
0.150(2)
0.788(1)
0.415(1)
0.3132(9)
0.335(1)
0.4574(9)
6.0(4)
6.5(5)
6.0(4)
5.8(4)
4.1(4)
C6
0.4235(2) 0.3619(1)
4.88(4)
Table 5. Coordinates of atoms in the molecule of 2-methylindeno[2,1-d]thiazol-4-one (IIIb), equivalent isotropic temperature
3
3
factors of non-hydrogen atoms B = 4/3 Σ Σ(aiaj)B(i, j) (Å2), and isotropic temperature factors of hydrogen atoms (Å2)
i = 1 j = 1
Atom
S1
O4
N3
C2
C3a 0.6205(1)
C4a 0.6184(1)
C4
C5
C6
C7
C8
x
y
z
B
Atom
C8a
C8b
C9
H5
H6
H7
H8
H91
H92
H93
x
y
z
B
0.63525(4) –0.20488(5) –0.08240(3) 3.350(9)
0.6293(1) –0.0961(2) –0.0138(1) 2.94(3)
0.6301(1) –0.0042(2) –0.0566(1) 2.93(3)
0.6236(2) –0.2711(3) –0.2418(1) 4.59(5)
0.6001(1)
0.6177(1)
0.6248(1)
–0.3855(2) –0.13747(8) 5.06(3)
–0.0126(2) –0.19060(9) 3.52(3)
–0.1453(2) –0.1792(1)
–0.0911(2) –0.1208(1)
–0.2600(2) –0.0104(1)
–0.2650(2) –0.0970(1)
–0.3856(2) –0.0423(1)
–0.3481(3) –0.1201(1)
–0.1878(3) –0.1438(1)
–0.0585(3) –0.0906(1)
3.40(4)
3.03(3)
3.14(3)
3.37(3)
3.94(4)
4.46(5)
4.21(4)
3.77(4)
0.603(1)
0.615(1)
0.634(1)
0.643(1)
0.674(2)
0.571(2)
0.628(2)
–0.496(4) –0.023(1)
–0.430(2) –0.156(1)
–0.172(3) –0.192(1)
–0.053(3) –0.108(1)
–0.329(3) –0.239(2)
–0.328(3) –0.236(2)
7.8(6)
4.7(5)
5.1(5)
4.2(5)
8.1(6)
9.1(7)
0.6116(1)
0.6143(2)
0.6212(2)
0.6313(2)
0.6360(1)
–0.217(5) –0.290(3) 15(1)
bands typical of free (3560–3500 cm–1) or associated
hydroxy group (2700–2500 cm–1) in carboxylic acids,
while the carbonyl absorption band is displaced by
~20 cm–1 toward higher frequencies (usually, from
and some geometric parameters of molecules IIIa–IIIc
are given in Tables 3–7. The molecular structures with
atom numbering are shown in Figs. 1–3. Compounds
IIIa (Fig. 1) and IIIb (Fig. 2) give rise, respectively, to
1
1690 to 1710 cm–1) (Table 1). In the H NMR spectra
O4
we observed no multiplet signals typical of protons in
unsubstituted phenyl group, but multiplets correspond-
ing to a four-spin ABCD system appear in the region
δ 7.0–7.6 ppm (Table 1). The number of carbon signals
in the 13C NMR spectra of compounds IIIa–IIIc
is greater by two than in the spectra of the initial
acids, and the carbonyl carbon signal shifts downfield
(δC ~ 185 ppm; Table 2).
The molecular and crystalline structures of pure
indenothiazole IIIa, 2-methylindenothiazole IIIb, and
2-phenylindenothiazole IIIc were examined by the
X-ray diffraction method. The coordinates of atoms
C4
C5
C41
C3
N3
C6
C7
C2
C81
C82
C8
S1
Fig. 1. Structure of the molecule of indeno[2,1-d]thiazol-4-
one (IIIa) in crystal.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

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MAMEDOV et al.
Table 6. Coordinates of atoms in the molecule of 2-phenylindeno[2,1-d]thiazole (IIIc), equivalent isotropic temperature
3
3
factors of non-hydrogen atoms B = 4/3 Σ Σ (ai aj)B(i, j) (Å2), and isotropic temperature factors of hydrogen atoms (Å2)
i = 1 j = 1
Atom
S1A
S1B
x
y
z
B
Atom
x
y
z
B
–0.49530(7)
–0.15591(7)
–0.2716(2)
–0.2037(2)
–0.0550(2)
–0.3639(2)
–0.0578(2)
–0.4400(2)
–0.3482(2)
–0.0639(2)
–0.1676(2)
–0.2737(3)
–0.1618(3)
–0.2576(3)
–0.0898(3)
–0.3020(3)
–0.0322(3)
–0.3814(3)
–0.4256(3)
–0.0846(2)
–0.4786(2)
–0.1023(2)
0.48917(6) 0.33273(5) 3.73(2) C13A
0.49242(6) 0.16660(6) 3.65(2) C13B
–0.6018(3)
–0.2652(3)
–0.5645(2)
–0.2245(3)
–0.1117(2)
–0.2999(2)
–0.3838(2)
–0.0137(2)
–0.4106(2)
–0.0353(2)
–0.186(2)
–0.249(2)
–0.115(2)
–0.286(2)
–0.078(2)
–0.403(2)
–0.487(2)
–0.166(2)
–0.373(2)
–0.062(2)
–0.442(2)
–0.018(2)
–0.213(2)
–0.579(2)
–0.346(2)
–0.661(2)
–0.289(2)
–0.600(2)
0.8080(3) 0.3558(2) 4.00(8)
0.8084(3) 0.1787(2) 4.37(9)
0.7115(2) 0.3502(2) 3.74(8)
0.7126(2) 0.1706(2) 3.92(8)
0.2988(2) 0.0823(2) 3.03(7)
0.2843(2) 0.3916(2) 3.60(8)
0.3012(2) 0.3520(2) 3.24(7)
0.3094(2) 0.1258(2) 3.22(7)
0.4068(2) 0.3610(2) 3.15(7)
0.4154(2) 0.1283(2) 3.21(7)
O4B
O4A
N3B
N3A
C2B
C2A
C3A
C3B
C4B
C4A
C5B
C5A
C6B
C6A
C7B
C7A
C8A
C8B
C9A
C9B
0.4154(2)
0.3928(2)
0.5673(2)
0.5511(2)
0.5932(2)
0.5811(2)
0.4533(2)
0.4667(2)
0.3982(2)
0.3784(2)
0.2068(2)
0.1896(2)
0.1248(2)
0.1133(2)
0.1370(3)
0.1289(2)
0.2233(3)
0.2285(2)
0.6854(2)
0.6930(2)
0.7570(2)
0.7714(3)
0.8527(3)
0.8672(2)
0.8795(2)
0.8851(2)
0.0155(2)
0.4638(2)
0.0835(2)
0.4175(2)
0.1227(2)
0.3828(2)
0.4037(2)
0.0874(2)
0.0551(2)
0.4267(2)
0.0703(2)
0.3966(2)
0.1022(2)
0.3603(2)
0.1441(2)
0.3211(3)
0.3163(2)
0.1555(2)
0.3852(2)
0.1317(2)
0.4216(2)
0.1023(2)
0.4248(2)
0.1097(2)
0.3911(2)
0.1487(2)
5.09(6) C14A
5.64(6) C14B
3.58(6) C41B
3.49(6) C41A
3.28(7) C81A
3.23(7) C81B
2.92(7) C82A
3.10(7) C82B
3.60(8) H5A
3.96(8) H5B
3.86(8) H6B
4.17(8) H6A
4.16(8) H7B
4.78(9) H7A
4.18(9) H8A
4.80(9) H8B
4.07(8) H10A
3.59(8) H10B
3.11(7) H11A
3.24(7) H11B
3.57(7) H12B
3.78(8) H12A
4.52(8) H13B
4.24(9) H13A
4.08(8) H14B
4.64(9) H14A
0.182(2)
0.201(2)
0.055(2)
0.060(2)
0.077(2)
0.073(2)
0.232(2)
0.242(2)
0.747(2)
0.756(2)
0.888(2)
0.917(2)
0.947(2)
0.939(2)
0.818(2)
0.825(2)
0.659(2)
0.641(2)
0.411(2)
0.045(2)
0.098(2)
0.369(1)
0.170(1)
0.298(2)
0.296(2)
0.176(2)
0.443(1)
0.077(1)
0.440(1)
0.079(2)
0.154(1)
0.391(2)
0.199(2)
0.338(2)
0.191(2)
0.320(2)
6.2(8)
2.7(5)
5.6(7)
2.6(5)
2.6(5)
5.2(7)
3.2(6)
3.5(6)
3.1(6)
2.9(6)
1.9(5)
3.6(6)
2.7(6)
5.8(8)
5.5(8)
2.6(6)
5.0(7)
5.4(8)
C10A –0.4299(2)
C10B –0.0239(2)
C11A –0.4678(3)
C11B –0.0663(3)
C12A –0.5531(3)
C12B –0.1858(3)
monoclinic and rhombic crystals with similar param-
eters; the independent parts of their unit cells contain
a single independent molecule. The indenothiazole
ring systems in molecules IIIa–IIIc are planar within
the experimental error [0.02(2) Å]. Crystals of
2-phenyl-substituted indenothiazole IIIc are charac-
terized by the presence of two independent molecules
in the asymmetric part of a unit cell (Fig. 3). The
phenyl groups in both molecules are almost coplanar to
the indenothiazole plane [the dihedral angle between
the indenothiazole fragment and the phenyl ring is
2.7(1)° in both molecules]. Despite similar conforma-
tions, an appreciable redistribution of bond lengths in
the indenothiazole fragments is observed, which con-
siderably exceeds the experimental error (Table 5).
Packing of molecules IIIa–IIIc in crystal is deter-
mined by weak intermolecular C–H · · · O, C–H · · · S,
and π–π interactions. The O2 atom in unsubstituted
indenothiazole IIIa is involved in a short contact
with the H2' proton of the neighboring molecule:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

539
FUSED POLYCYCLIC NITROGEN-CONTAINING HETEROCYCLES: VIII.
d(H1···O20) 1.6278 Å, ∠(O1H1O20) 172.76° (symmetry
O4
operation 1/2 – x, 1/2 + y, 1/2 – z), which gives rise to
formation of zigzag chains (Fig. 4). Contiguous mole-
cules in the chain form separate mutually orthogonal
stacks via π–π interactions (dihedral angles between
the planes of the adjacent molecules in a stack are
equal to 0°, and the shortest distance between these
planes varies from 4.06 to 4.48 Å).
C4
C5
C3
N3
C41
C6
C2
C9
C82
C81
C7
C8
S1
Fig. 2. Structure of the molecule of 2-methylindeno[2,1-d]-
thiazol-4-one (IIIb) in crystal.
For compound IIIb in crystal we did not reveal
appreciable intermolecular contacts like C–H···X
which could fit formal criteria accepted in PLATON
[17]. Presumably, crystal packing of this compound is
determined mainly by π–π contacts between electronic
systems of the aromatic rings. In this case, layers
parallel to the y0z crystallographic plane are formed
(Fig. 5), and molecules IIIb belonging to the neigh-
boring layers give rise to zigzag stacks. The dihedral
angle between the planes of molecules in stacks varies
in the range from 0 to 10°, and the interplanar distance,
from 2.91 to 3.65 Å.
1–16.4°/min with respect to θ. No drop in the intensity
of three control reflections was observed during data
acquisition. Empirical correction for absorption was
introduced for compounds IIIa (µCu = 30.444 cm–1)
and IIIb (µCu = 27.018 cm–1). The structures were
solved by the direct method using SIR program [18]
and were refined by the full-matrix least-squares
procedure; function to be minimized Σw(|Fo| – |Fc|)2;
extinction was not taken into account; weight scheme
4F0 /[σ(I)2 + (0.04F0 )]2. The positions of hydrogen
atoms were determined from the difference synthesis
of electron density and were refined in isotropic
approximation at the final stage. The coordinates of
atoms and their temperature factors are listed in
Tables 3–5. The calculations were performed on
an Alpha Station 200 computer using MolEN software
package [19]. Graphical representations of molecular
2
2
Phenyl-substituted indenothiazole IIIc is also
characterized by the existence of only π–π contacts in
crystal: each of the two independent molecules gives
rise to dimers [the dihedral angle between the mole-
cular planes is 0°, and the distance between the planes
is 3.41(2) Å]. Insofar as the planes of independent
molecules A and B form an angle of 57.7(2)°, alter-
nating layers of molecules A and B in crystal are
arranged parallel to each other, and molecules within
a layer are arranged in an inclined mode (Fig. 6).
Table 7. Selected bond lengths (d, Å) in molecules of com-
pounds IIIa–IIIc
IIIc
Bond
IIIa
IIIb
EXPERIMENTAL
A
B
S1–C2
C2–N3
N3–C3
C3–C4
C3–C82
C4–C41
1.740(2) 1.755(2)
1.299(2) 1.307(2)
1.372(2) 1.370(2)
1.482(2) 1.482(3)
1.371(2) 1.365(2)
1.506(2) 1.507(3)
1.750(3)
1.309(4)
1.350(4)
1.498(5)
1.354(5)
1.480(5)
1.406(5)
1.401(5)
1.392(5)
1.352(6)
1.404(5)
1.388(5)
1.469(4)
1.694(3)
1.776(3)
1.320(3
1.377(4)
1.492(4)
1.330(4)
1.502(4)
1.420(4)
1.373(4)
1.389(4)
1.385(4)
1.379(5)
1.367(4)
1.464(4)
1.714(3)
The melting points were determined on a Boetius
device. The IR spectra were recorded on a UR-20
spectrometer from samples dispersed in mineral oil.
1
The H NMR spectra of acids IIa–IIc were obtained
on a Varian T-60 instrument (60.0 MHz), and of
indenothiazoles IIIa–IIIc, on a Bruker MW-250
spectrometer (250.132 MHz). The 13C NMR spectra
were measured on a Bruker MSL-400 spectrometer at
100.6 MHz.
C41–C81 1.403(2) 1.408(2)
C41–C5
C5–C6
C6–C7
C7–C8
C8–C81
1.373(2) 1.375(3)
1.396(2) 1.386(3)
1.387(3) 1.377(3)
1.395(2) 1.402(3)
1.385(2) 1.372(3)
X-Ray diffraction experiments were performed
using an Enraf–Nonius CAD-4 automatic four-circle
diffractometer (20°C, λCuKα 1.5418 Å, graphite mono-
chromator). The principal crystallographic parameters
and experimental conditions are given in Table 3.
ω-Scanning for compound IIIc and ω/2θ-scanning for
IIIa and IIIb were applied; variable scan rate,
C81–C82 1.474(2) 1.470(3)
C82–S1
1.693(2) 1.698(2)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

540
MAMEDOV et al.
O4B
C10B
C4B
N3B
C11B
C3B
C11A
C10A
C14A
C5B
O4A
N3A
C9B
C2B
C4A
C3A
C9A
C2A
C41B
C82B
C5A
C41A
C12A
C12B
C13B
C81B
C6B
C7B
C6A
C13A
C82A S1A
C81A
C14B
C8B
C7A
C8A
S1B
Fig. 3. Structure of two independent molecules A and B of 2-phenylindeno[2,1-d]thiazol-4-one (IIIc) in crystal.
Fig. 4. Hydrogen bond system in the crystalline structure of indeno[2,1-d]thiazol-4-one (IIIa).
a
b
c
0
Fig. 5. Molecular stacks of compound IIIb in crystal. View along the 0y axis.
structures were obtained, and intermolecular inter-
actions were analyzed, using PLATON software [20].
5-Phenylthiazole-4-carboxylic acid (IIa). Methyl
5-phenylthiazole-4-carboxylate (Ia), 2.19 g, was added
to 15 ml of a 10% aqueous–methanolic solution of
0.56 g of potassium hydroxide, and the mixture was
heated for 2 h under reflux. The solvent was
evaporated, 10 ml of water was added to the residue,
and the mixture was acidified with dilute hydrochloric
acid under vigorous stirring. The precipitate was
filtered off, dried in air, and recrystallized from
2-propanol. Yield 1.85 g (92%), mp 185–186°C.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 4 2004

541
FUSED POLYCYCLIC NITROGEN-CONTAINING HETEROCYCLES: VIII.
160°C. Found, %: C 63.98; H 2.75; N 7.53; S 17.00.
C10H5NOS. Calculated, %: C 64.17; H 2.67; N 7.49;
S 17.11.
a
2-Methylindeno[2,1-d]thiazol-4-one (IIIb) was
synthesized from acid IIb as described above for
compound IIIa. Yield 63%, mp 122–125°C. Found,
%: C 65.60; H 3.59; N 7.05; S 15.79. C11H7NOS.
Calculated, %: C 65.67; H 3.48; N 6.97; S 15.92.
2-Phenylindeno[2,1-d]thiazol-4-one (IIIc) was
synthesized from acid IIc as described above for
compound IIIa. Yield 70%, mp 160–161°C. Found,
%: C 72.89; H 3.30; N 5.32; S 12.20. C16H9NOS.
Calculated, %: C 73.00; H 3.42; N 5.39; S 12.33.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
nos. 03-03-32865 and 02-03-32280).
0
b
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N 6.48; S 14.56. C11H9NO2S. Calculated, %: C 60.27;
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synthesized in a similar way from ester Ic. Yield 86%,
mp 129–133°C. Found, %: C 68.30; H 3.84; N 5.10;
S 11.48. C16H11NO2S. Calculated, %: C 68.33; H 3.91;
N 4.98; S 11.39.
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thiazolecarboxylic acid IIa was added, and the mixture
was heated for 1.5 h at 100–140°C, cooled, and diluted
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crystallized from toluene. Yield 1.3 g (70%), mp 157–
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