Reactions of 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-2-iminocoumarins with N-nucleophiles

Article abstract of DOI:10.1023/A:1022142812756

The reaction of 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-2-iminocoumarins with N-nucleophiles was studied. This reaction gives 2-N-substituted 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-iminocourmarins. N-Nucleophiles such as arylamines, het

Full text of DOI:10.1023/A:1022142812756

Chemistry of Heterocyclic Compounds, Vol. 38, No. 11, 2002
REACTIONS OF 3-(4-ARYL-2-THIAZOLYL)-
AND 3-(2-BENZOTHIAZOLYL)-
2-IMINOCOUMARINS
WITH N-NUCLEOPHILES
N. Yu. Gorobets1, A. V. Borisov1, A. V. Silin1, V. M. Nikitchenko1, and S. N. Kovalenko2
The reaction of 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-2-iminocoumarins with N-nucleophiles
was studied. This reaction gives 2-N-substituted 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-
iminocourmarins. N-Nucleophiles such as arylamines, heterocyclic amines, and hydrazine derivatives
undergo this reaction.
Keywords: 3-(4-aryl-2-thiazolyl)-2-iminocoumarins, 3-(2-benzothiazolyl)-2-iminocoumarins, 2-imino-
coumarins, nucleophilic substitution.
The synthesis, structure, and reactivity of 2-iminocoumarins have been studied intensively in the past
decade [1-3]. Many of these compounds have found use as dyes for various purposes [4, 5] and have interesting
biological activity [6]. On the other hand, N-substituted derivatives of 2-iminocoumarins have not been studied
extensively [7-9].
Several approaches exist for the synthesis of N-substituted 2-iminocoumarins involving the reaction of
2-thiocoumarins [10], dialkylacetals of coumarins [11], and salts of 2-ethoxybenzopyrilium [8] or
2-iminocoumarins [7] with N-nucleophiles. The synthesis of N-substituted 2-iminocoumarins is most
conveniently carried out with 2-iminocoumarins as the starting reagents. We should note that some
N-substituted 2-iminocoumarin-3-carboxamides may appear as intermediates in the synthesis of various
3-hetarylcoumarins [12, 13].
In the present work, we studied the reactions of 3-(4-aryl-2-thiazolyl)- and 3-(2-benzothiazolyl)-2-
iminocoumarins with various N-nucleophiles.
The starting 3-thiazolyl-2-iminocoumarins 3a-i, 4a,b were obtained according to our previous procedure
[3] by the condensation of aldehydes 1a-e with the corresponding nitriles 2a-f in 2-propanol in the presence of
catalytic amounts of piperidine; these nitriles have an active methylene group. The reaction of these
iminocoumarins with primary amines was carried out in ethanol, butanol, and DMF in the presence of catalytic
amounts of sulfuric acid or acetic acid. The reaction of 3-thiazolyl-2-iminocoumarins 3a-i, 4a,b with
1.5-2 equivalents of N-nucleophiles 5a-q in DMF at reflux in the presence of catalytic amounts of sulfuric acid
leads to the greatest yields of the final products. This procedure gave a series of N-substituted
3-[4-(4-R2-phenyl)-2-thiazolyl]-2-iminocoumarins 6a-u:
__________________________________________________________________________________________
1 V. N. Karazin Kharkov National University, 61077 Kharkov, Ukraine; e-mail: nic@univer.charkov.ua.
2
National Pharmaceutical Academy, 61002 Kharkov, Ukraine. Translated from Khimiya Geterotsiklicheskikh
Soedinenii, No. 11, pp. 1573-1581, November, 2002.
0009-3122/02/3811-1389$27.00©2002 Plenum Publishing Corporation
1389

2
R2
R
CHO
OH
R1
R3NH2
N
N
CN
1a–e
5a–c,e–o
S
S
R1
2a–e
O
3a–i
NH
2
R
N
4
5
8
3
6
7
S
R1
2
R3
O
N
1
6a–u
N
N
S
S
1a,b
5d,e
R1
R1
N
R3
CN
O
N
O
NH
S
2f
7a,b
4a,b
1 a R1 = H, b R1 = 4-NEt2, c R1 = 4-OH, d R1 = 5-Cl, e R1 = 5,6-benzo; 2 a R2 = H, b R2 = Me, c R2 = Cl, d R2 = Br, e R2 = NO2;
3 a-c R1 = H, d-f R1 = 7-NEt2, g R1 = 7-OH, h R1 = 6-Cl, i R1 = 5,6-benzo, a R2 = H, b R2 = Me, c R2 = NO2, d R2 = Me, e R2 = Cl,
f, g R2 = Br, h R2 = Cl, i R2 = Me; 4 a R1 = H, b R1 = 7-NEt2; 5 a R3 = Ph, b R3 = o-MeC6H4, c, e R3 = p-MeC6H4,
d R3 = o-MeOC H , f R3 = m-BrC H , g R3 = p-Me NC H , h R3 = p-O NC H , i R3 = 2-thiazolyl, j R3 = -Py, k R3 = NHPh,
α
6
4
6
4
2
6
4
6
l R3 = NHCOPh, m R3 = NHCOCH2CN, n R3 = NHCOCH2Py+Cl-,2o R3 =4NHCSNH2, p R3 = NHCONH2, q R3 = OH;
6 a-i R1 = H, j-r R1 = –NEt2, s R1 = 7-OH, t R1 = 6-Cl, u R1 = 5,6-benzo; a-e R2 = H, f-h R2 = Me, i R2 = NO2, j, k R2 = Me,
l-n R2 = Cl, o-s R2 = Br, t R2 = Cl, u R2 = Me; a, l, t R3 = Ph, b, j R3 = p-Me2NC6H4, c R3 = m-BrC6H4, d, q R3 = NHPh,
e R3 = NHCOCH2Py+Cl–, f R3 = NHCOPh, g R3 = NHCOCH2CN, h R3 = NHCSNH2, i R3 = p-MeOC6H4, k R3 = p-O2NC6H4,
m R3 = 2-thiazolyl, n R3 = NHCONH , o R3 = o-MeC H , p R3 = -Py, r, u R3 = OH, s R3 = p-MeC H ;
α
7 a R1 = H, b R1 = 7-NEt2, a R3 = p6-MeOC6H4; b R3 = o-MeOC6H4
2
4
6
4
Aromatic amines of varying basicity (from p-dimethylaminoaniline to p-nitroaniline) and heterocyclic
amines such as α-aminopyridine and 2-aminothiazole readily undergo this reaction. No product was isolated in
the case of sterically hindered o-bromoaniline. The presence of other ortho substituents in the nucleophile leads
only to a slight drop in the yield of the product (Table 1). The products of condensation with such nucleophiles
as phenylhydrazine, the hydrazides of benzoic and cyanoacetic acid, Girard reagent P (1-(carbazoylmethyl)-
pyridinium chloride), thiosemicarbazide, semicarbazide, and hydroxylamine were obtained under similar
conditions. The use of acid catalysis in butanol at reflux proved more suitable for the synthesis of N-substituted
3-benzothiazolyl-2-iminocoumarins 7a and 7b.
3-Thiazolyl-2-iminocoumarins 6a-u, 7a,b are fine crystalline compounds ranging in color from light
yellow to dark red. The solubility of these products in usual organic solvents such as ethanol, acetonitrile, and
DMF ranges considerably depending on the nature of the substituents.
The electronic absorption spectra (EAS) of solutions of these products at 250-550 nm show two or more
maxima (Table 1). In the case of 2-iminocoumarins without substituents in the coumarin part (R1 = H) and
lacking strong electron-donor or strong electron-withdrawing substituents, the electronic absorption spectra are
1390

Fig. 1. Electronic absorption spectra of 6a,b,d,i (a) and 6j,k,l,q (b).
characteristic for 3-hetarylcoumarins and 3-hetaryl-2-iminocoumarins unsubstituted at the imino group such as
6a (R1 = R2 = H, R3 = Ph, Fig. 1a) and the long-wavelength maximum is found at virtually the same wavelength
(376 nm) as in the spectrum of 3-(4-phenyl-2-thiazolyl)-2-iminocoumarin (375 nm) [15].
These findings suggest a small effect for substituent R3 = Ph on the absorption of the coumarin
chromophore. On the other hand, the absorption spectrum is considerably altered upon the introduction of
electron-donor substituents (R3 = p-Me2NC6H4 in 6b and R3 = NHPh in 6d). The strong bathochromic shift of
the long-wavelength maximum (δ = 59 nm for 6b and 72 nm for 6d) indicates conjugation in the new
chromophore system with significant participation of substituent R3 in the imino group (Fig. 1a). The effect of
substituent R2 is pronounced only in the case of R2 = NO2 in 6i. The hypsochromic shift of the long-wavelength
absorption band (23 nm) and significant change in the overall shape of the spectrum in this case demonstrate the
possible effect of substituent R2 on the electronic structure of the chromophore system. The introduction of a
strongly electron-donating N,N-dimethylamino group at C(7) in the coumarin system (R1 = NEt2) leads to a
change in the electronic spectrum characteristic for 3-thiazolylcoumarins with an increase in intensity and a
significant bathochromic shift of the long-wavelength band (72 nm, Fig. 1b for 6l) in comparison with
unsubstituted coumarins. Variation in the electronic nature of substituent R3 significantly affects the shape of
the spectrum (R3 = p-Me2NC6H4 in 6j, R3 = NHPh in 6q, and R3 = pO2NC6H4 in 6k, Fig. 1b), while the position
of the maximum of the long-wavelength band is not as strongly affected.
The IR spectra of all the compounds synthesized show a strong band for vibration of the C=N bond in
the iminolactone group of the coumarin system at 1596-1708 cm-1. Bands for the C=C bonds of the aromatic and
heteroaromatic systems appear at 1502-1613 cm-1. The bands at 1555-1708 cm-1 for 6e-g,n correspond to
vibrations of the C=O bonds in the hydrazide group. Weak bands for the vibrations of the C–H alkyl bonds of
substituents R2 and R3 are found at 2785-2910 cm-1. Medium-intensity bands characteristic for the diethylamino
group are seen for the 7-N,N-diethylamino derivatives at 2962-2675 cm-1. Weak bands for the vibrations of the
aromatic and heteroaromatic C–H bonds appear at 3046-3117 cm-1. The bands for the vibrations of the OH and
NH groups appear at 3150-3462 cm-1. The rather low frequencies of several NH groups in 6f (3192 cm-1) and 6h
(3150 cm-1) suggest formation of strong hydrogen bonds in these compounds in the solid state (Table 1).
1
The H NMR spectra given in Table 2 for 6g and 6e show signals for the minor isomeric form, which
probably result from E,Z-isomerism of the C=N bond. While the singlet for the coumarin 8-H proton is at higher
field than the doublet for the 6-H proton in all the spectra of the N,N-diethylamino derivatives, the reverse
sequence is found for 6q (R3 = NHPh) and 6n (R3 = NHCONH2), probably as a consequence of the formation of
N–H···O intramolecular hydrogen bonds in these compounds.
1391

TABLE 1. Characteristics of 6a-u, 7a,b
Com-
Empirical
formula
Found N %
Calculated N, %
3
UV spectrum (ethanol), λ, nm
(ε·10-3, l/mol·cm)*
Yield,
%
7
——————
mp, °С
IR spectrum, ν, cm-1
pound
1
2
4
5
6
C24H16N2OS
C26H21N3OS
C24H15BrN2OS
C24H17N3OS
7.40
7.36
176-177
230-232
172-173
245-246
238-239
250-252
>300
1557, 1588; 1646; 3087
255 (34.2); 376 (17.2)
242 (28.7); 268 (27.3); 435 (7.8)
256 (37.2); 376 (19.1)
274 (34.8); 351 (11.5); 448 (7.3)
385 (14.5)
65
82
59
87
83
78
90
86
63
72
25
90
63
6a
6b
6c
6d
6e
6f
9.89
1553,1599; 1642; 2785; 3101
9.92
6.06
6.10
1558, 1585,1600; 1653; 3048
10.67
1509, 1580; 1596; 3098; 3378
10.63
C25H19ClN4O2S
C26H19N3O2S
C22H16N4O2S
C20H16N4OS2
C25H17N3O4S
C31H32N4OS
C29H26N4O3S
C28H24ClN3OS
C25H21ClN4OS2
11.69
11.80
1600; 1638; 1691; 3065; 3430
9.63
1511, 1594; 1638; 1655; 2925; 3100; 3192
1602; 1645; 1683; 2911, 2934; 3065, 3100; 3404
1500, 1592; 1635; 2910; 3105; 3150, 3265, 3425
1503, 1598; 1655; 2830; 2991, 3061
264 (36.8); 382 (16.3)
386 (16.2)
9.60
14.07
13.99
6g
6h
6i
14.32
248-250
264-266
195-197
250-251
248-249
234-235
221 (26.0); 270 (34.0); 390 (14.2)
227 (19.1); 298 (14.5); 353 (15.0)
14.27
9.19
9.23
10.95
1510, 1592, 1610; 1652; 2805, 2910, 2975; 3075, 3117 255 (30.9); 324 (18.3); 451 (29.2)
6j
11.01
11.08
10.97
1502, 1559, 1584; 1634; 2872, 2962; 3079
1511, 1585, 1606; 1658; 2923, 2976; 3080
1511, 1579; 1640; 2920, 2965; 3072, 3108
229 (30.7); 461 (13.5)
6k
6l
8.62
256 (30.9); 337 (9.5); 448 (36.2)
8.65
11.39
11.36
230 (23.5); 287 (19.9); 357 (21.6);
474 (34.1)
6m

TABLE 1 (continued)
1
2
3
4
5
6
7
C23H22ClN5O2S
C29H26BrN3OS
C27H23BrN4OS
C28H25BrN4OS
C22H20BrN3O2S
C25H17BrN2O2S
C24H14Cl2N2OS
C23H16N2O2S
14.93
14.97
265-266
192-193
227-228
243-244
268-269
245-247
230-232
238-239
180-181
1583, 1603; 1640; 1708; 2924, 2970; 3108; 3392, 3462 260 (32.6); 324 (6.6); 451 (31.5)
81
64
66
95
50
70
68
72
81
6n
6o
6p
6q
6r
6s
7.83
1512, 1590, 1611; 1666; 2926, 2965
1582, 1613; 1658; 2924, 2965; 3091
1506, 1588, 1602; 1630; 2920, 2965; 3092; 3365
1508, 1587, 1603; 1641; 2923, 2968; 3112; 3302
1568, 1598; 1650; 2905; 3095; 3292
1562, 1591; 1643; 3090
265 (27.3); 336 (5.4); 441 (36.8)
268 (29.2); 338 (8.7); 446 (40.0)
270 (31.4); 389 (11.1); 452 (26.1)
251 (31.8); 313 (7.7); 433 (34.0)
269 (37.2); 394 (20.1)
7.72
10.45
10.54
10.25
10.27
8.87
8.93
5.78
5.72
6.21
6.23
385 (16.4)
6t
7.25
1512, 1565, 1582; 1685; 2911; 3059, 3102; 3426
1563, 1590; 1651; 2834; 3046
252 (93.6); 411 (30.3)
6u
7a
7.29
C23H16N2O2S
7.21
7.29
266 (19.1); 291 (22.1); 325 (18.7);
398 (10.7)
C27H25N3O2S
9.19
244-246
1515,1582,1610; 1668; 2821, 2921, 2966; 3055
295 (14.7); 453 (42.8)
59
7b
9.22
_______
* UV spectra of compounds 6c,f,l,q,s and 7a taken in MeCN solution, for compounds 6e,g,t – in DMF solution.

TABLE 2. 1H NMR Spectra of 6a-u, 7a,b
Chemical shifts δ, ppm
Com-
4-Н
5-Н
СН arom
pound
СН coumarin
СН arom. in R3
СН aliphat.
NH, OH
8
coumarin thiazole
at thiazole C(4)
5
1
2
3
4
6
7
8.68
7.88
7.18 (1Н, d, 8-H);
7.23 (1Н, t, 4-H);
7.10 (1Н, t, 4-H);
—
2.94 (6Н, s, CH3Ar)
—
—
6a
6b
6c
6d
6e
6f
7.38-7.46 (2Н, m, 6-, 7-H); 7.26-7.38 (4Н, m, 2-, 3-, 5-, 6-H)
7.68 (1Н, d, 5-H)
7.26-7.38 (4Н, m, 2-, 3-, 5-, 6-H)
8.63
8.80
8.23
8.63
8.48
8.23
8.10
8.18
8.24
8.08
7.23-7.61 (1Н, d, 8-H);
7.23-7.61
6.80 (2Н, d, 3-, 5-H);
8.11 (2Н, d, 2-, 6-H)
—
7.23-7.61 (2Н, m, 6-, 7-H); (5Н, m, 2-, 3-, 4-, 5-, 6-H)
7.81 (1Н, d, 5-H)
6.55 (1Н, d, 8-H);
7.15-7.58
8.08 (1Н, s, 2-H);
—
7.15-7.58 (2Н, m, 6-, 7-H); (5Н, m, 2-, 3-, 4-,5-,6-H)
7.80 (1Н, d, 5-H)
7.15-7.58 (3Н, m, 4-, 5-, 6-H);
7.25 (1Н, d, 8-H);
7.19 (1Н, t, 4-H);
6.75 (1Н, t, 4-H);
—
9.60 (1Н, s, NH)
11.90 (1Н, s, NH)
11.08 (1Н, s, NH)
11.35 (1Н, s, NH)
7.40-7.50 (2Н, m, 6-, 7-H); 7.29-7.38 (4Н, m, 2-, 3-, 5-, 6-H)
7.29-7.38 (4Н, m, 2-, 6-, 5-, 3-H)
7.62 (1Н, d, 5-H)
7.20-7.45 (1Н, m, 8-H);
7.48-7.70 (2Н, m, 6-, 7-H);
7.8 (1Н, d, 5-H)
7.20-7.45 (2Н, m, 3-, 5-H);
8.02 (2Н, d, 2-, 6-H);
7.62 (1Н, s, 4-H)
8.25 (2Н, m, 3-, 5-H);
8.45 (1H, t, 4-H);
6.20 (2Н, s, CH2)
2.35 (3Н, s, CH3)
9.22 (2Н, d, 2-, 6-H)
7.20-7.32 (1Н, m, 8-H);
7.20-7.32 (2Н, m, 3-, 5-H);
7.38-7.60 (3Н, m, 4-, 3-, 5-H);
7.38-7.60 (2Н, m, 6-, 7-H); 7.85-7.98 (2Н, m, 2-, 6-H)
7.69 (1Н, d, 5-H)
7.85-7.98 (2Н, m, 2-, 6-H)
8.49
8.46
8.23
8.09
7.33-7.61 (3Н, m, 6-, 7-, 8-H) 7.32 (2Н, d, 3-, 5-H);
—
—
2.38 (3Н, s, CH3);
4.30 (2Н, s, CH2)
2.40 (3Н, s, CH3Ar)
6g
6h
7.77 (1Н, d, 5-H)
7.27 (1Н, d, 8-H);
7.98 (2Н, d, 2-, 6-H)
7.24 (2Н, d, 3-, 5-H);
7.05 (1Н, s, NH);
8.48 (1Н, s, NH);
10.30 (1Н, br. s,
NH) (diffuse)
7.45-7.56 (2Н, m, 6-, 7-H); 7.94 (2Н, d, 2-, 6-H)
7.71 (1Н, d, 5-H)
8.68
8.43
8.44
7.62
7.21-7.32 (2Н, m, 6-, 8-H);
7.48 (1Н, t, 7-H);
8.24 (2Н, d, 2-, 6-H);
8.33 (2Н, d, 3-, 5-H)
6.96 (2Н, d, 3-, 5-H);
7.44 (2Н, d, 2-, 6-H)
3.80 (3Н, s, CH3Ar);
—
6i
6j
7.77 (1Н, d, 5-H)
6.34 (1Н, s, 8-H);
6.53 (1Н, d, 6-H);
7.36 (1Н, d, 5-H)
7.53 (2Н, d, 3-, 5-H);
7.90 (2Н, d, 2-, 6-H)
6.72 (2Н, d, 3-, 5-H);
7.43 (2Н, d, 2-, 6-H)
1.21 (6Н, t, CH3СН2);
2.41 (3Н, s, CH3Ar);
3.00 (6Н, s, 2CH3Ar);
3.48 (4Н, q, CH2СН3)
—
8.70
7.87
6.34 (1Н, s, 8-H);
6.67 (1Н, d, 6-H);
7.55 (1Н, d, 5-H)
7.23 (2Н, d, 3-, 5-H);
7.94 (2Н, d, 2-, 6-H)
7.45 (2Н, d, 2-, 6-H);
8.25 (2Н, d, 3-, 5-H)
1.15 (6Н, t, CH3СН2);
2.35 (3Н, s, CH3Ar);
3.40 (4Н, q, CH2CH3)
—
6k

TABLE 2 (continued)
1
2
3
4
5
6
7
8
8.61
8.03
6.32 (1Н, s, 8-H);
6.64 (1Н, d, 6-H);
7.58 (1Н, d, 5-H)
7.49 (2Н, d, 3-, 5-H);
8.13 (2Н, d, 2-, 6-H)
7.12 (1Н, t, 4-H); 7.35 (2Н, d,
2-, 6-H); 7.40 (2Н, t, 3-, 5-H);
1.19 (6Н, t, CH3CH2);
3.45 (4Н, q, CH2CH3)
—
6l
8.78
8.31
8.59
8.72
8.13
8.17
8.65
8.72
8.91
8.06
8.18
7.97
8.41
8.10
8.12
8.05
8.17
8.09
6.67 (1Н, s, 8-H);
6.84 (1Н, d, 6-H);
7.73 (1Н, d, 5-H)
6.61 (1Н, d, 6-H);
6.78 (1Н, s, 8-H);
7.47 (1Н, d, 5-H)
6.18 (1Н, s, 8-H);
6.60 (1Н, d, 6-H);
7.49 (1Н, d, 5-H)
6.22 (1Н, s, 8-H);
6.64 (1Н, d, 6-H);
7.49 (1Н, d, 5-H)
6.57 (1Н, d, 6-H);
6.68 (1Н, s, 8-H);
7.42 (1Н, d, 5-H)
6.44 (1Н, s, 8-H);
6.55 (1Н, d, 6-H);
7.42 (1Н, d, 5-H)
6.55 (1Н, s, 8-H);
6.71 (1Н, d, 6-H);
7.52 (1Н, d, 5-H)
7.21 (1Н, d, 8-H);
7.47 (1Н, d, 7-H);
7.84 (1Н, d, 5-H)
7.48 (2Н, d, 3-, 5-H);
7.67 (2Н, d, 2-, 6-H)
7.40 (1Н, d, 4-H); 8.14 (1Н, d, 5-H)
1.22 (6Н, t, CH3CH2);
3.53 (4Н, q, CH2CH3)
—
6m
6n
6o
6p
6q
6r
6s
7.52 (2Н, d, 3-, 5-H);
8.16 (2Н, d, 2-, 6-H)
—
1.21 (6Н, t, CH3CH2);
3.45 (4Н, q, CH2CH3)
6.22 (2Н, s, NH2);
9.44 (1Н, s, NH)
7.59 (2Н, d, 3-, 5-H);
8.03 (2Н, d, 2-, 6-H)
6.95-7.28 (4Н, m, 3-, 4-, 5-, 6-H)
1.19 (6Н, t, CH3CH2);
2.28 (3Н, s, CH3Ar);
3.41 (4Н, q, CH2CH3)
1.22 (6Н, t, CH3CH2);
3.46 (4Н, q, CH2CH3)
—
7.58 (2Н, d, 3-, 5-H);
7.98 (2Н, d, 2-, 6-H)
7.15 (2Н, m, 4-, 6-H);
—
7.72 (1Н, t, 5-H); 7.81 (1Н, s, 3-H)
7.65 (2Н, d, 3-, 5-H);
8.02 (2Н, d, 2-, 6-H)
6.76 (1Н, t, 4-H);
1.20 (6Н, t, CH3CH2);
4.45 (4Н, q, CH2CH3)
9.21 (1Н, s, NH)
10.48 (1Н, s, ОН)
10.4 (1Н, s, ОН)
—
7.15-7.38 (4Н, m, 2-, 6-, 5-, 3-H)
7.64 (2Н, d, 3-, 5-H);
8.01 (2Н, d, 2-, 6-H)
—
1.13 (6Н, t, CH3CH2);
3.41 (4Н, q, CH2CH3)
7.58 (2Н, d, 3-, 5-H);
8.02 (2Н, d, 2-, 6-H)
7.15 (2Н, d, 3-, 5-H);
7.25 (2Н, d, 2-, 6-H)
2.43 (3Н, s, CH3Ar)
7.45 (2Н, d, 3-, 5-H);
8.10 (2Н, d, 2-, 6-H)
7.15 (1Н, t, 4-H);
—
—
6t
7.31-7.41 (4Н, m, 2-, 6-, 3-, 5-H)
7.47 (1Н, d, 10-H);
7.30 (2Н, d, 3-, 5-H);
—
10.63 (1Н, s, ОН)
6u
7.64 (1Н, d, 5-H);
7.87-8.15 (2Н, m, 6-, 8-H)
7.74 (1Н, t, 7-H);
7.87-8.15 (2Н, m, 6-, 8-H);
8.45 (1Н, d, 9-H)
8.77
8.64
—
—
7.23-7.31 (1Н, m, 8-H);
7.46-7.57 (2Н, m, 6-, 7-H);
7.82 (1Н, d, 5-H)
7.23-7.31 (1Н, m, 5-H);
7.44 (1Н, t, 6-H);
6.97 (2Н, d, 3-, 5-H);
3.77 (3Н, s, CH3Ar)
—
—
7a
7b
7.46-7.57 (2Н, m, 2-, 6-H)
8.02 (1Н, d, 7-H); 8.09 (1Н, d, 4-H)
6.15 (1Н, s, 8-H);
7.27 (1Н, t, 5-H);
6.86-6.98 (2Н, m, 5-, 4-H);
7.00-7.08 (2Н, m, 2-, 6-H)
1.19 (6Н, t, CH3CH2);
3.40 (4Н, q, CH2CH3);
3.82 (3Н, s, CH3Ar)
6.52 (1Н, d, 6-H);
7.35-7.45 (1Н, m, 5-H)
7.35-7.45 (1Н, m , 6-H);
7.84-7.92 (2Н, m, 7-, 4-H)

Our study has shown that 2-imino-3-thiazolylcoumarins react with N-nucleophiles under acid catalysis
conditions to give N-substituted 3-thiazolyl-2-iminocoumarins.
EXPERIMENTAL
The electronic absorption spectra were taken on a Hitachi U-3210 spectrophotometer. The IR spectra
1
were taken for KBr pellets on a Specord IR-75 spectrometer at from 400 to 4000 cm-1. The H NMR spectra
were taken on a Bruker 300 spectrometer at 300 MHz in DMSO-d6 with TMS as the internal standard. The
purity of all the compounds was checked by thin-layer chromatography on 200×200-mm Silufol plates using 1:2
ethyl acetate–toluene as the eluent.
The physicochemical and spectral indices of 6 and 7 are given in Tables 1 and 2.
N-Substituted 2-Imino-3-[4-(4-R2-phenyl)-2-thiazolyl)]coumarins 6a-u (General Method). A
sample of 2-iminocoumarin (3 mmol) was dissolved in DMF (10 ml) and amino compound (4.5-6.0 mmol) and
10% H2SO4 (3-5 drops) in methanol were added. The mixture was heated at reflux for 15-20 min. After cooling,
the solution was diluted with a 10-fold volume of methanol. The precipitate was filtered off and recrystallized
from a suitable solvent (toluene or acetonitrile).
N-Substituted 3-Benzothiazolyl-2-iminocoumarins 7a and 7b (General Method). A sample of
2-iminocoumarin (3 mmol) was dissolved in a minimal amount of hot butanol and substituted aniline
(4.5-6 mmol) along with 2-3 drops 10% H2SO4 in methanol was added. The mixture was heated at reflux for
30-90 min. After cooling, the precipitate formed was filtered off and recrystallized from a suitable solvent
(butanol or acetonitrile).
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