Solvent and substituent effects on the electronic spectra of 3-arylazo-imidazo[1,2-b]pyrazolo[4,3-d]-pyridazines

Article abstract of DOI:10.3184/174751912X13463419012595

A series of new 3-arylazo-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b] pyrazolo[4,3-d]pyridazines was prepared via reaction of hydrazonoyl halides with 3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole. The structures of the compounds prepared were confirmed by spectral and elemental analyses. The solvatochromic and substituent effects on the absorption spectra of these azo dyes were interpreted by correlation of absorption frequencies with Kamlet-Taft and Hammett equations, respectively.

Full text of DOI:10.3184/174751912X13463419012595

JOURNAL OF CHEMICAL RESEARCH 2012
RESEARCH PAPER 615
OCTOBER, 615–618
Solvent and substituent effects on the electronic spectra of
3-arylazo-imidazo[1,2-b]pyrazolo[4,3-d]-pyridazines
Ahmad S. Shawali*, Thoraya A. Farghaly and Tarek M.S. Nawar
Department of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt
A series of new 3-arylazo-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]pyrazolo[4,3-d]pyridazines was prepared via
reaction of hydrazonoyl halides with 3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole. The structures of the com-
pounds prepared were confirmed by spectral and elemental analyses. The solvatochromic and substituent effects on
the absorption spectra of these azo dyes were interpreted by correlation of absorption frequencies with Kamlet–Taft
and Hammett equations, respectively.
Keywords: arylazoheterocycles, pyrazole, hydrazonoyl bromides, imidazo[1,2-b]pyrazolo[4,3-d]-pyridazines
Over the past five years, we have explored the utility of hydra-
zonoyl halides in the synthesis of aryl- and heteroaryl-
azo derivatives of heterocyclic compounds and studied their
azo-hydrazone tautomerism.1–8 Many such colourants have
found numerous applications including hair dyes, disperse
dyes, ink-jet inks and laser materials.9,10 In this work, a series
of 10 3-arylazo-8H-imidazo[1,2-b]pyrazolo[4,3-d]pyridazine
derivatives 5a–j were synthesised and their electronic absorp-
tion spectra have been recorded in the region 200–800 nm in
five different solvents. Our intention was to shed some light on
the effects of solvents and substituents on their absorption
spectra via the application of the Kamlet–Taft and Hammett
equations, respectively.11,12
(MS, IR, 1H NMR). Such results (see Experimental) indicated
that the products isolated from the studied reactions are the
respective tricyclic arylazo compounds 5 (Scheme 1). For
example, their IR spectra revealed the absence of the bands
due to the carbonyl and nitrile groups present in the putative
intermediates 3 and 4 (Scheme 1). The H NMR spectra of 5
exhibited a common signal assignable to the 6-methyl group in
the range δ 2.56–2.82.
To account for the formation of the products 5, it is sug-
gested, as depicted in Scheme 1, that the reactions start with
the formation of the substitution intermediates 3. The latter
undergo two successive in situ cyclisations to furnish the
respective 3-arylazo-8H-imidazo[1,2-b]pyrazolo[4,3-d]-pyri-
dazines 5 as the end products (Scheme 1).
The UV-Vis absorption spectra of the dyes prepared 5a–j
were recorded over the range 200–800 nm using a series of
five solvents of different polarities at a concentration of 1 ×
10−6 mol L−1. Each of the dyes gave two absorption bands in
all of the solvents employed. The results are summarised in
Table 1. As shown, each compound exhibits an intense absorp-
tion band in the region 400–450 nm. Such data indicate that the
electronic absorption spectra of compounds 5 are typical of
azo chromophores.8,18,19
1
Results and discussion
The required hydrazonoyl bromides 2a–j13–16 and 3-hydra-
zonoacetyl-4-cyano-1,5-diphenylpyrazole 117 were prepared
as previously reported. When equimolar quantities of 1 and
each of the hydrazonoyl bromides 2 were refluxed in 1,4-
dioxane in the presence of triethylamine, a single product was
obtained in each case as evidenced by TLC analysis of the
crude product. The structures of the compounds prepared were
elucidated on the basis of their microanalyses and spectral data
Scheme 1
* Correspondent. E-mail: as_shawali@mail.com

616 JOURNAL OF CHEMICAL RESEARCH 2012
Table 1 Electronic absorption spectral data of compounds 5a–j in various solvents
Compd
Solvent/λmax (log ε)
Acetonitrile
Ethanol
1,4-Dioxane
Chloroform
Methanol
5a
5b
5c
5d
5e
5f
405(4.14); 306 (4.22)
405(3.94); 302 (4.60)
405(4.29); 304 (4.35)
412(4.34); 305 (4.01)
412(4.41); 304 (4.03)
412(4.23); 305 (4.13)
415(4.04); 312 (4.20)
417(4.27); 304 (4.05)
427(4.19); 307 (3.95)
441(4.46); 303 (4.21)
405 (4.13); 299 (4.50)
404 (3.71); 290 (5.22)
405 (4.25); 301 (4.50)
413 (4.35); 300 (4.42)
412 (4.36); 299 (4.42)
412 (4.18); 293 (4.26)
422 (4.06); 300 (4.51)
417 (4.25); 290 (4.53)
426 (4.15); 296 (4.36)
441 (4.46); 292 (4.53)
410 (4.08); 298 (4.62)
423 (3.57); 300 (4.53)
409 (4.30); 298 (4.59)
416 (4.16); 298 (4.61)
415 (4.37); 294 (4.42)
416 (4.21); 288 (4.57)
425 (4.04); 288 (4.61)
401 (4.33); 300 (5.20)
401 (4.34); 228 (5.60)
399 (4.51); 228 (5.69)
411 (4.15); 230 (5.22)
410 (4.41); 300 (4.67)
411 (4.20); 300 (4.71)
415 (3.89); 300 (4.52)
405 (4.13); 303 (4.48)
400 (3.50); 296 (4.28)
405 (4.26); 300 (4.49)
413 (4.30); 300 (4.45)
411 (4.40); 300 (4.41)
412 (4.18); 300 (4.26)
422 (4.03); 300 (4.54)
5g
5h
5i
420 (4.28); 292 (4.60) 416 (4.27); 268 (5.04)) 416 (4.26); 300 (4.25)
429 (4.13); 298 (4.34)
448 (4.43); 288 (4.58)
428 (3.82); 300 (4.21)
438 (4.55), 348 (4.60)
425 (4.11); 303 (4.20)
440 (4.47); 306 (4.31)
5j
As shown in Table 1, the absorption bands for all of the
compounds 5 suffer small solvent shifts, a behaviour which is
expected for local electronic transitions corresponding to π–π*
transitions. The highest bathochromic shift was obseved in
methanol for all compounds. In addition, the visible spectra of
the compounds having electron withdrawing substituents such
as 5d–j exhibit large bathochromic shift in all solvents used
(Table 1).
The effect of solvent polarity and hydrogen bonding on
absorption spectra of the studied compounds 5 were examined
by means of the linear solvation energy relation (LSER)
namely Kamlet–Taft equation [Eqn (1)].11,12
parameters π*, β and α. The degree of success of Eqn (1) is
shown in Fig. 1 by means of a plot of υmax calculated versus
υmax observed in 1,4-dioxane (Table 4). Furthermore, as the
coefficients of the solvent parameters measure the relative
susceptibilities of the solvent-dependent solute property
namely the absorption frequencies to the solvent parameters, it
is clear that the negative sign of the α-coefficient indicates a
bathochromic shift and the positive sign of the β-coefficient
indicates a hypsochromic shift. The percentage contributions
of solvatochromic parameters for the azo dyes 5 are depicted
in Table 5. As shown for almost all compounds, most of the
solvatochromism is due to the solvent polarity and basicity
rather than the solvent acidity.
As shown in Table 6, the absorption spectra of the com-
pounds 5a–j in a given solvent depend upon the nature of the
substituents. For example, in methanol compounds 5 exhibit
bathochromic shifts (∆λmax) whose magnitude depends on the
nature of the substituent present. In order to rationalise these
results, the λmax values of the series 5a–j were correlated to
Hammett constants. In such a correlation, the enhanced
substituent constants σ –(X) were used for the para-substituents
as they are in direct conjugation with the azo chromophore.
ΰ = υ° + sπ* + bβ+ aα
(1)
where π* is the measure of solvent dipolarity/polarisabilty, β is
the scale of the solvent hydrogen bond acceptor (HBA), basic-
ities, α is the scale of the solvent hydrogen-bond donor (HBD)
acidities and υ° is the regression value of the solute property in
the reference solvent cyclohexane. The regression coefficients
s, b and a in Eqn (1) measure the relative susceptibilities of the
solvent-dependent solute property (absorption frequencies) to
the indicated solvent parameters. The values of the solvent
parameters are given in Table 2.
The results of multiple linear regression analysis of the
data by Eqn (1), are given in Table 3. As shown, the values
(0.988–0.784) of the correlation coefficient (r) indicate that the
absorption frequencies for the azo compounds 5a–j in the
selected solvents show satisfactory correlation with the solvent
Table 4 Experimental and calculated values of υmax of
compounds 5a–j in 1,4-dioxane
Compound
υmax Calcd (1013) Hz
υmax exptl.(1013) Hz
5a
5b
5c
5d
5e
5f
73.94
73.95
73.83
72.66
72.82
72.82
71.1
71.96
70.45
67.88
74.17
74.26
74.07
72.73
72.9
Table 2 Solvent parameters13
Solvent
π*
β
α
72.9
Ethanol
0.54
0.55
0.58
0.60
0.75
0.77
0.37
0.0
0.62
0.31
0.83
0.0
0.44
0.93
0.19
5g
5h
5i
71.17
72.03
70.42
68.03
1,4-Dioxane
Chloroform
Methanol
Acetonitrile
5j
Table 3 Regression fits to solvatochromic parameters [Eqn (1)]a,b
Compd
Equation
5a
5b
5c
5d
5e
5f
υmax = (72.380 + 1.78π* + 1.582β – 0.028α)1013
υmax = (66.383 + 9.71π* + 6.003β – 1.855α)1013
r = 0.787; s = 0.749
r = 0.948; s = 1.034
υmax = (71.872 + 2.552π* + 1.485β + 0.339α)1013 r = 0.784; s = 0.813
υmax = (71.612 + 1.099π* + 1.197β – 0.195α)1013 r = 0.935; s = 0.233
υmax = (71.47 + 1.672π* + 1.150β – 0.222α)1013
υmax = (71.53 + 1.438π* + 1.355β – 0.448α)1013
υmax = (70.03 + 0.571π* + 2.052β + 0.625α)1013
υmax = (70.69 + 1.563π* + 1.126β – 0.289α)1013
υmax = (69.13 + 1.821π* + 0.879β – 0.638α)1013
r = 0.9067; s = 0.280
r = 0.933; s = 0.255
r = 0.988; s = 0.231
r = 0.938; s = 0.211
r = 0.975; s = 0.125
5g
5h
5i
5j
υmax = (65.683 + 2.753π* + 1.869β – 0.345α)1013 r = 0.902; s = 0.469
a r, Correlation coefficient; b s, standard error of the estimate.

JOURNAL OF CHEMICAL RESEARCH 2012 617
Table 5 Percentage contribution of solventochromic
parametersa
Compd
Pπ*(%)
Pβ (%)
Pα (%)
5a
5b
5c
5d
5e
5f
52.50
55.28
58.31
44.10
54.92
44.36
17.59
52.48
54.54
55.42
46.66
34.15
33.93
48.04
37.77
41.8
63.16
37.8
26.33
37.62
0.826
10.55
7.76
7.85
7.29
13.82
19.24
9.71
5g
5h
5i
19.11
6.95
5j
a Pi (%) = i (100)/[s + b + a].
–
Fig. 2 Relation between λmax and σ
methanol (data from Table 6)
for compounds 5a–j in
(X)
JEOL JNM-LA400 for 400 MHz FT NMR Spectrometers. Mass
spectra were recorded on a GCMS-QP 1000 EX Shimadzu and
GCMS 5988-A HP spectrometers. Electronic absorption spectra were
recorded on Perkin-Elmer Lambada 40 spectrophotometer. Elemental
analyses were carried out at the Microanalytical Laboratory of
Cairo University, Giza, Egypt. The hydrazonoyl bromides 213−16 and
3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole 1.17
Reaction of compounds 1 with hydrazonoyl bromides (2): To a mix-
ture of 3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole (1) (0.75 g,
2.5 mmol) and the appropriate hydrazonoyl bromide (2) (2.5 mmol) in
1,4-dioxane (20 mL) was added triethylamine (0.35 mL). The mixture
was refluxed for 10 h, then cooled. The solution was poured onto ice.
The solid produced was collected by filtration and crystallised from
the appropriate solvent to give the corresponding compound 5.
3-[4-Methoxyphenylazo]-6-methyl-2,8,9-triphenyl-8H-imidazo-
[1,2-b]pyrazolo[4,3-d]pyridazine (5a): Brown solid, (0.76 g, 64%),
m.p. 214–216 °C (ethanol). 1H NMR (DMSO-d6, 400 MHz) δ 2.74 (s,
3H, CH3), 3.83 (s, 3H, OCH3), 7.35–7.64 (m, 15H, ArH), 7.81 (d,
J = 8.0 Hz, 2H, ArH), 8.12 (d, J = 8.0 Hz, 2H, ArH); IR (KBr) νmax
3066, 2931, 2835, 1593, 1496 cm−1. MS m/z (%) 535 (M+, 7), 377
(15), 97 (28), 84 (28), 77 (28), 73 (44), 72 (39), 55 (100). Anal. Calcd
for C33H25N7O (535.21): C, 74.0; H, 4.70; N, 18.31. Found: C, 74.08;
H, 4.81; N, 18.07%.
Fig. 1 The plot of υmax observed against υmax calculated from
Eqn (1) for compound 5 in different solvents (data from
Table 4).
Table 6 Substituent effects on electronic absorption spectra
of compounds 5a–j in methanol
a
−
Compound
λmax
X
∆ λmax
σX
6-Methyl-3-[4-methylphenylazo]-2,8,9-triphenyl-8H-imidazo[1,2-b]
pyrazolo[4,3-d]pyridazine (5b): Red solid, (0.65 g, 55%), m.p. 96–
98 °C (1,4-dioxane-ethanol). H NMR (DMSO-d6, 500 MHz) δ 2.05
5a
5b
5c
5d
5e
5f
401
401
399
411
410
411
415
416
428
438
4-MeO
4-Me
H
+2
+2
0.0
+12
+11
+12
+16
+17
+29
+39
–0.27
–0.17
0.0
0.23
0.37
0.39
0.68
0.71
0.84
1.28
1
(s, 3H, CH3), 2.79 (s, 3H, CH3), 7.0 (d, J = 8.0 Hz, 2H, ArH), 7.67–
7.36 (m, 15H, ArH), 7.94 (d, J = 8.0 Hz, 2H, ArH); IR (KBr) νmax
3055, 2916, 2854, 1600, 1492, 1438, 1369, 1326 cm−1. MS m/z (%)
519 (M+, 31), 518 (33), 416 (38), 376 (36), 361 (47), 106 (43), 105
(38), 91 (51), 77 (100). Anal. Calcd for C33H25N7 (519.22): C, 76.28;
H, 4.85; N, 18.87. Found: C, 76.41; H, 5.04; N, 18.67%.
6-Methyl-3-phenylazo-2,8,9-triphenyl-8H-imidazo[1,2-b]pyra-
zolo-[4,3-d]pyridazine (5c):16 Dark orange crystals (0.85 g, 67%),
m.p. 230–232 °C (1,4-dioxane). 1H NMR (DMSO-d6, 300 MHz)
δ 2.56 (s, 3H, CH3), 7.43–8.22 (m, 20H, ArH); IR (KBr) νmax 1595,
1537, 1492 cm−1. 13C NMR (DMSO-d6, 300 MHz) δ 17.6,109.1,
114.0,120.6, 120.7,121.8, 125.6, 126.2, 127.0, 128.1, 128.2, 128.8,
129.1, 129.2, 129.3, 129.4, 129.5, 130.3, 133.3, 138.2, 138.9, 148.0,
150.1, 153.5. MS m/z (%) 505 (M, 19), 504 (18), 476 (11), 252 (3),
180 (7), 77 (100). Anal. Calcd for C32H23N7 (505.57): C, 76.02; H,
4.59; N, 19.39. Found: C, 76.11; H, 4.42; N, 19.25%.
4-Cl
3-Cl
3-Br
5g
5h
5i
4-EtOOC
3-NO2
4-Ac
5j
4-NO2
a ∆ λmax = λmax (5) – λmax (5c).
The results of such a correlation are shown in Fig. 2. The
equation of the regression line is :
λmax (X) = 403.1 + 24.23 σ –
(X)
with correlation coefficient r = 0.952 and standard deviation
s = 3.99. This finding indicates that in the π–π* transition of
the azo chromophore, the negative charge is largely localised
on the N-atom adjacent to the benzene ring bearing the
substituent.
3-[4-Chlorophenylazo]-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]-
pyrazolo[4,3-d]pyridazine (5d): Red solid, (0.78 g, 66%), m.p. 232–
234 °C (1,4-dioxane-ethanol). 1H NMR (DMSO-d6, 500 MHz) δ 2.72
(s, 3H, CH3), 7.38–7.61 (m, 15H, ArH), 7.76 (d, J = 8.0 Hz, 2H, ArH),
8.12 (d, J = 8.0 Hz, 2H, ArH); IR (KBr) νmax 3058, 1631, 1596, 1488,
1373, 1323 cm−1. MS m/z (%) 541 (M++2, 17), 540 (M++1, 29),
539 (M+, 52), 538 (56), 537 (42), 416 (36), 415 (23), 400 (18),
270 (16), 180 (23), 127 (23), 111 (22), 77 (100). Anal. Calcd for
C32H22ClN7(539.02): C, 71.17; H, 4.11; N, 18.16. Found: C, 7099; H,
4.32; N, 18.43%.
Experimental
Melting points were determined on a Gallenkamp apparatus. IR spec-
tra were recorded in potassium bromide using Perkin-Elmer FTIR
1
1650 and Pye-Unicam SP300 IR spectrophotometers. The H NMR
3-[3-Chlorophenylazo]-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]
pyrazolo[4,3-d]pyridazine (5e): Red solid, (0.81 g, 69%), m.p. 156–
158 °C (1,4-dioxane-ethanol). 1H NMR (DMSO-d6, 500 MHz) δ 2.80
spectra were recorded in DMSO-d6 on a Varian Mercury VXR-300
1
spectrometer (300 MHz for H NMR), JEOL – ECA 500 MHz or

618 JOURNAL OF CHEMICAL RESEARCH 2012
(s, 3H, CH3), 7.47–7.79 (m, 19H, ArH); IR (KBr) νmax 3062, 2912,
2854, 1631, 1596, 1488, 1369, 1326 cm−1. MS m/z (%) 541 (M++2, 4),
540 (M++1, 15), 539 (M+, 28), 539 (45), 538 (41), 537 (38), 510 (37),
509 (28), 416 (21), 400 (18), 270 (20), 180 (29), 111 (20), 77 (100).
Anal. Calcd for C32H22ClN7(539.02): C, 71.17; H, 4.11; N, 18.16.
Found: C, 71.30; H, 4.03; N, 17.98%.
3-[3-Bromophenylazo]-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]-
pyrazolo[4,3-d]pyridazine (5f): Red solid, (0.69 g, 59%), mp. 178-
180 °C (1,4-dioxane-ethanol). 1H NMR (DMSO-d6, 500 MHz) δ 2.80
(s, 3H, CH3), 7.44-7.91 (m, 19H, ArH); IR (KBr) νmax 3058, 2854,
1593, 1535, 1489, 1435, 1369, 1323, 1254 cm−1. MS m/z (%) 585
(M++2, 22), 584 (M++1, 22), 583 (M+, 22), 401 (22), 283 (22), 248
(22), 147 (41), 122 (37), 117 (48), 116 (33), 113 (37), 104 (48), 101
(33), 99 (41), 98 (37), 94 (48), 92 (56), 89 (41), 86 (67), 79 (44), 78
(37), 77 (63), 60 (100). Anal. Calcd for C32H22BrN7 (583.47): C, 65.76;
H, 3.79; N, 16.78. Found: C, 65.85; H,4.03; N, 16.94%.
6-Methyl-3-[4-nitrophenylazo]-2,8,9-triphenyl-8H-imidazo[1,2-b]-
pyrazolo[4,3-d]pyridazine (5j): Red solid, (0.86 g, 73%), m.p. 272–
274 °C (1,4-dioxane-ethanol). 1H NMR (DMSO-d6, 500 MHz) δ 2.80
(s, 3H, CH3), 7.20-8.40 (m, 19H, ArH); IR (KBr) νmax 3063, 2851,
1632, 1593, 1504, 1435, 1377, 1327, 1254 cm−1. MS m/z (%) 550 (M+,
34), 549 (40), 549 (57), 548 (49), 476 (26), 416 (60), 415 (40), 195
(31), 180 (37), 138 (51), 105 (37), 92 (60), 77 (100). Anal. Calcd for
C32H22N8O2(550.57): C, 69.81; H, 4.03; N, 20.35. Found: C, 70.06; H,
4.12; N, 20.59%.
Received 16 April 2012; accepted 16 August 2012
Paper 1201267 doi: 10.3184/174751912X13463419012595
Published online: 28 September 2012
References
1
2
A.S. Shawali and T.A. Farghaly, Tetrahedron, 2009, 65, 644.
A.S. Shawali, M.A. Mosselhi, F.M.A. Altalbawy and T.A. Farghaly,
Tetrahedron, 2008, 64, 5524.
3-[4-Ethoxycarbonylphenylazo]-6-methyl-2,8,9-triphenyl-8H-
imidazo[1,2-b]pyrazolo[4,3-d]pyridazine (5g): Red solid, (087 g,
1
3
4
5
A.S. Shawali, S.M. Sherif, T.A. Farghaly and M.A.A. Darwish, Afinidad,
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74%), m.p. 193–195 °C (1,4-dioxane-ethanol). H NMR (DMSO-d6,
400 MHz) δ 0.97 (t, J = 7.0 Hz, 3H, CH3), 2.75 (s, 3H, CH3), 4.68
(q, J = 7.0 Hz, 2H, CH2), 7.12 (d, J = 8.0 Hz, 2H, ArH), 7.34–7.96 (m,
15H, ArH), 8.08 (d, J = 8.0 Hz, 2H, ArH); IR (KBr) νmax 3062, 2923,
2808, 1725, 1596, 1539, 1373, 1323, 1249 cm−1. MS m/z (%) 577 (M+,
10), 576 (11), 301 (43), 131 (46), 120 (75), 105 (57), 104 (46), 91
(32), 90 (39), 77 (46), 75 (32), 60 (100), 59 (54). Anal. Calcd for
C35H27N7O2 (577.63): C, 72.78; H, 4.71; N, 16.97. Found: C, 72.56; H,
4.66; N, 17.03%.
6-Methyl-3-[3-nitrophenylazo]-2,8,9-triphenyl-8H-imidazo[1,2-b]-
pyrazolo[4,3-d]pyridazine (5h): Red solid, (0.82 g, 70%), m.p. 226–
228 °C (1,4-dioxane-ethanol). 1H NMR (DMSO-d6, 500 MHz) δ 2.82
(s, 3H, CH3), 7.49–8.30 (m, 19H, ArH); IR (KBr) νmax 3059, 2851,
1632, 1597, 1524, 1485, 1439, 1323, 1258 cm−1. MS m/z (%) 552
(M++2, 29), 167 (29), 150 (33), 149 (52), 132 (29), 121 (43), 83 (67),
71 (81), 57 (100). Anal. Calcd for C32H22N8O2 (550.57): C, 69.81; H,
4.03; N, 20.35. Found: C, 69.67; H, 4.22; N, 20.25%.
6
7
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2006, 1, 531.
A.S. Shawali and M.A.N. Mosselhi, J. Heterocycl. Chem., 2003, 40, 725.
10 A.S. Shawali, M.H. Abdelkader and F.M.A. Altalbawy, Tetrahedron, 2002,
58, 2875.
11 M.J. Kamlet, J.M. Abboud and R.W. Taft, Prog. Phys. Org. Chem., 1981,
13, 485.
12 M.J. Kamlet, J.L.M. Abboud, M.H. Abraham and R.W. Taft, J. Org. Chem.,
1983, 48, 2877.
13 A.S. Shawali and A.O. Abdelhamid, Bull. Chem. Soc. Jpn., 1976, 49, 321.
14 A.S. Shawali, M.H. AbdelKader and F.A. Altalbawy, Tetrahedron, 2002,
3-[4-Acetylphenylazo]-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]-
pyrazolo[4,3-d]pyridazine (5i): Orange solid, (0.91 g, 77%), m.p.
130–132 °C (ethanol). 1H NMR (DMSO-d6, 400 MHz) δ 2.38 (s, 3H,
CH3), 2.64 (s, 3H, CH3), 7.35–7.75 (m, 15H, ArH), 7.72 (d, J = 8.0 Hz,
2H, ArH), 8.09 (d, J = 8.0 Hz, 2H, ArH); IR (KBr) νmax 3067, 2974,
2882, 1690, 1663, 1597, 1493, 1373, 1326, 1254 cm−1. MS m/z (%)
548 (M++1, 4), 547 (M+, 6), 416 (33), 404 (53), 389 (78), 120 (48),
105 (60), 77 (100). Anal. Calcd for C34H25N7O (547.61) C, 74.57; H,
4.60; N, 17.90. Found: C, 74.52; H, 4.35; N, 17.72%.
58, 2875.
15 A.S. Shawali, A.O. Abdelhamid, H.M. Hassaneen and C. Parkanyi,
Phosphorus, Sulfur Silicon, 1981, 12, 377.
16 A.O. Abdelhamid, A.M. Negm and I.M. Abbas, J. Prakt. Chem., 1989, 331,
31.
17 T.A. Farghaly and A.S. Shawali, Tetrahedron, 2010, 66, 2700.
18 A.S. Shawali, M.M. Zayed and T.A. Farghaly, J. Heterocycl. Chem., 2005,
42, 185.
19 A.S. Shawali, S.A. Khattab and A.M. Farag; J. Chem. Eng. Data, 1977, 22,
104.

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