Reactions with hydrazonoyl halides 581: Synthesis of 2,3-dihydro-1,3,4- thiadiazoles and 5-arylazothiazoles

Article abstract of DOI:10.1080/10426500701734190

1,3,4-Thiadiazolines containing a chromone moiety and 5-{1-[4-substituted- 5-phenyldiazenyl)(1,3-thiazol-2-yl]-5-phenyl-2-pyrazolin-3-yl)} -4-methoxybenzo[b]-furan-6-ol were synthetic from hydrazonoyl halide and alkyl carbodithioates and 5-[1-aminothiomethoxy)-5-phenyl-2-pyrazolin-3-yl)]-4- methoxybenzo[b]furan-6-ol, respectively. All structures of the newly synthesized compounds were elucidated by elemental analysis, spectral data, and alternative synthesis methods whenever possible. Copyright Taylor & Francis Group, LLC.

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Reactions with Hydrazonoyl
Halides 58: Synthesis of 2,3-
Dihydro-1,3,4-thiadiazoles and
5-Arylazothiazoles
Abdou O. Abdelhamid a , Zeineb H. Ismail b & Anhar
Abdel-Aziem b
a Department of Chemistry, Faculty of Science, Cairo
University, Giza, Egypt
b Department of Chemistry, Faculty of Science (Girls
Branch), Al-Azhar University, Cairo, Egypt
Version of record first published: 24 Jun 2008
To cite this article: Abdou O. Abdelhamid, Zeineb H. Ismail & Anhar Abdel-Aziem
(2008): Reactions with Hydrazonoyl Halides 58: Synthesis of 2,3-Dihydro-1,3,4-
thiadiazoles and 5-Arylazothiazoles, Phosphorus, Sulfur, and Silicon and the Related
Elements, 183:7, 1735-1745
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Phosphorus, Sulfur, and Silicon, 183:1735–1745, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701734190
Reactions with Hydrazonoyl Halides 581: Synthesis of
2,3-Dihydro-1,3,4-thiadiazoles and 5-Arylazothiazoles
Abdou O. Abdelhamid,1 Zeineb H. Ismail,2
and Anhar Abdel-Aziem2
1Department of Chemistry, Faculty of Science, Cairo University,
Giza, Egypt
2Department of Chemistry, Faculty of Science (Girls Branch),
Al-Azhar University, Cairo, Egypt
1,3,4-Thiadiazolines containing a chromone moiety and 5-{1-[4-substituted-5-
phenyldiazenyl)(1,3-thiazol-2-yl]-5-phenyl-2-pyrazolin-3-yl)}-4-methoxybenzo[b]-
furan-6-ol were synthetic from hydrazonoyl halide and alkyl carbodithioates and
5-[1-aminothiomethoxy)-5-phenyl-2-pyrazolin-3-yl)]-4-methoxybenzo[b]furan-6-ol,
respectively. All structures of the newly synthesized compounds were elucidated
by elemental analysis, spectral data, and alternative synthesis methods whenever
possible.
Keywords 1,3,4-Thiadiazolines; chromones; hydrazonoyl halides; pyrazolines; thiazoles
INTRODUCTION
It is well known that chromones, 1,3,4-thidiazoles, and thiazoles pos-
sess pronounced biological activity. Thus, some chromone derivatives
possess remarkable vasodilator activity,2,3 and apasmolytic activity,4,5
and some other derivatives were useful as bronchodilators.6 In contin-
uation of an interest in the chemistry of thiadiazole systems, we report
some new heterocyclic systems, containing a chromone nucleus—a com-
bination that are expected to possess high biological activity.
RESULTS AND DISCUSSION
Treatment of visnaginone7 (1), 1-(6-hydroxy-4-methoxybenzo[b]furan-
5-yl)ethan-1-one, with the appropriate alkyl hydrazinecarbodithioate8,9
Received 17 July 2007; accepted 1 Septmeber 2007.
Address correspondence to Abdou O. Abdelhamid, Department of Chemistry, Faculty
of Science, Cairo University, Giza 12613, Egypt. E-mail: abdelhamid45@gmail.com
1735

1736
A. O. Abdelhamid et al.
SCHEME 1
2a,b in 2-propanol gave 5-(2-aza-1-methyl-2-{[(substituted) thioxo-
methyl]amino}vinyl)-4-methoxybenzo-[b]furan-6-ols 3a and 3b,
respectively (Scheme 1). Structures 3 were confirmed by elemen-
tal analyses, spectral data and chemical transformations. Thus,
C-ethoxycarbonyl-N-phenylhydrazonoyl chloride (4a) reacted with
methyl carbodithioate 3a in ethanol containing triethylamine to
afford ethyl 2-[1,2-diaza-3-(6-hydroxy-4-methoxybenzo[b]furan-5-
yl)but-2-enylidene]-3-phenyl-1,3,4-thiadiazoline-5-carboxylate
(8a).
Structures 8 were established by elemental analyses, spectral data,
and alternative syntheses. Thus, ethyl 2-hydrazono-3-phenyl-1,3,4-
thidiazoline-5-carboxylate10 (9) reacted with visnaginone 1 in ethanol
to give a product identical in all aspects (m.p., mixed m.p. and spectra)
with 8a. In addition, benzyl carbodithioate 3b reacted with 4a in
ethanolic triethylamine to give 8a.
In the light of the foregoing results, the mechanism outlined in
Scheme 1 seems to be the most plausible pathway for the formation
of 8 from the reaction of the 4 with 3a or 3b. The reaction involves

Reactions with Hydrazonoyl Halides 58
1737
initial formation of thiohydrazonate 5, which undergoes intermolecu-
lar cyclization as soon as it is formed to yield the intermediate 6 or
via 1,3-dipolar cycloaddition of nitrilimine 7 ( prepared in situ from
4 with triethylamine) to the C S double bond of 3. The formations
of 5 and 6 are similar to the reaction of hydrazonoyl chloride with 1-
phenyl-1,4-dihydrotetrazole-5-thione11 and 5-phenyl-1,3,4-thiadiazole-
2(3H)-thione.12 Compound 6 was converted to 8 by elimination of alkyl
mercaptan. Analogously, the appropriate 3a, b reacted with the ap-
propriate 4b–d in ethanolic triethyamine to afford 2,3-dihydro-1,3,4-
thiadiazoles 8b–d, respectively.
Similarly, treatment of the appropriate of 6-{2-aza-2-[(substitu-
ted thioxomethyl)amino]vinyl}-7-hydroxy-5-methoxy-2-methyl-4H-
chromen-4-ones 11a, b, which was prepared from 7-hydroxy-5-
methoxy-2-methyl-4-oxo-4H-chromene-6-carbaldehyde13 (10) with the
appropriate 2a, b in 2-propanol followed by the appropriate hydra-
zonoyl halides 4a–e, gave 6-[2,3-diaza-3-(5-substituted-3-phenyl(1,3,4-
thiadiazolin-2-ylidene)prop-1-enyl]-7-hydroxy-5-methoxy-2-methyl-
4H-chromen-4-ones 12a-e, respectively (Scheme 2). Structures 12
were confirmed by elemental analyses, spectral data, and alternative
syntheses.
O
OMe
O
O
RS(S)CHNN
OHC
HO
+
H2NNHC(S)SR
2
HO
O
CH3
CH3
11
+ 4 (7)
O
O
10
N
S
2,11a, R = CH3
b, R = CH2C6H5
a, R’ = COC2H5
b, R’ = COCH3
c, R’ = COC6H5
d, R’ = CONHC6
N
R’
N
N
HO
12
CH3
Ph
H
5
SCHEME 2
Treatment of the appropriate of 3-{2-aza-2-[(substituted thioxo-
methyl)mino]-vinyl}5-methoxyfurano[3,2-g]-4H-chromen-4-one 14a,b,
which was prepared from 5-methoxy-4-oxofurano[3,2-g]-4H-chromene-
3-carbaldehyde,14 and the appropriate 2a,b followed by with
the appropriate hydrazonoyl halides 4a-c, afforded 3-[2,3-diaza-
3-(5- substituted 3-methyl(1,3,4-thiadiazolin-2-ylidene))prop-1-
enyl]-5-methoxyfurano [3,2-g]-4H-chromen-4-ones 15a–c, respectively
(Scheme 3).

1738
A. O. Abdelhamid et al.
OMe
13
OMe
O
O
O
O
H
CHO
SR
N
N
+
H2NHNC:(S)SR
2
S
O
O
14
S
+ 4
N
R'
a, R' = COC2H5
b, R' = COCH3
c, R' = COC6H5
OMe O
2,14a, R = CH3
b, R = CH2C6H5
N
N
N
Ph
O
O
15
SCHEME 3
2,4-Dimethoxybenzaldehyde (16) reacted with the appropriate
alkyl hydrazinecarbodithioate 2a, b in 2-propanol to give {[-1-aza-2-
(2,4-dimethoxy)vinyl]amino}substituted thiomethane-1-thiones 17a, b
(Scheme 4).
CHO
H
OMe
SR
N
N
+
H2NHNC:(S)SR
2
S
MeO
+ 4
OMe
17
S
OMe
16
R'
N
N
N
N
a, R' = COC2H5
b, R' = COCH3
c, R' = COC6H5
Ph
2,17a, R = CH3
b, R = CH2C6H5
MeO
OMe
18
SCHEME 4
Structures 17 were confirmed by elemental analyses, spectral
data, alternative syntheses, and chemical transportation. Hydrazonoyl
chloride 4a reacted with 17a or 17b in ethanolic triethylamine
to give ethyl 2-[1,2-diaza-3-(dimethoxyphenyl)orop-2-enylidine]-3-
phenyl-1,3,4-thiadiazoline-5-carboxylate (18a). Analogously, each 17a
and 17b reacted with the appropriate hydrazonoyl halides 4b, c to af-
ford 1,3,4-thiadiazolines 18b and 18c, respectively.
Finally, treatment of 1-(6-hydroxy-4-methoxybenzo[b]furan-5-yl)-
3-phenylprop-2-en-1-one13 (19) with thiosemicarbazide in boiling
acetic acid to give 5-[1-aminothiomethoxy)-5-phenyl-2-pyrazolin-
3-yl)]-4-methoxybenzo[b]furan-6-ol (20) (Scheme 5). Compound 20

Reactions with Hydrazonoyl Halides 58
1739
CSNH2
N
OMe
19
OMe
N
Ph
COCH=CHPh
AcOH
H2NNHCSNH2
+
O
OH
O
OH
20
N=N-C6H5
R'
a, R' = COCH3
b, R' = COC6H5
+ 4
Ph
S
N
PhCOCH2Br
S
N
N
OMe
21
N
N
OMe
N
+
-
Ph
PhN2Cl
Ph
O
OH
O
OH
22
SCHEME 5
reacted with the appropriate hydrazonoyl halides 4c and 4d in
boiling chloroform (or ethanol) containing triethylamine to give 5-1-[4-
substituted-5-phenyldiazenyl)(1,3-thiazol-2-yl]-5-phenyl-2-pyrazolin-
3-yl)-4-methoxybenzo[b]-furan-6-ols 21a, and 21b, respectively.
Structures 21 were confirmed by elemental analyses, spectral
data, and alternative syntheses. Thus, benzenediazonium chlo-
ride reacted with 4-methoxy-5-[5-phenyl-1-(4-phenyl(1,3-thiazol-2-
yl)]benzo[b]furan-6-ol (22) in pyridine to give a product identical in
all aspects (m.p., mixed m.p., and spectra) with 21b.
Biological Activity
The tested microorganisms were gram-positive bacteria [Staphylococ-
cus aureus(ATCC25923) and Streptococcus pyrogenes (ATCC19615)],
gram negative bacteria [Pseudomonas Phaseolicola (GSPB 2828) and
Pseudomonas Fluorescens (S 97)] and some fungal pathogens (Fusar-
ium oxysporum and Aspergillus funigatus). The tested compounds were
dissolved N,N-dimethylformamide, which possessed no inhibition activ-
ity, to concentrations of 2 mg/1 mL and 1 mg/1 mL. The test was per-
formed on medium potato dextrose agar (PDA) which contained infusion
200 g of potato, 6 g of dextrose, and 15 g of agar. Uniform size filter pa-
per disks (3 disks per compound) were impregnated by an equal volume
(10 µ) from the specific concentration of dissolved tested compounds and
carefully placed on inoculated agar surface. After incubation for 36 h

1740

Reactions with Hydrazonoyl Halides 58
1741
at 27◦C, in the case of bacteria and 48 h at 24◦C, in the case of fungi
inhibition of the organisms was evidenced by a clear zone surrounding
each disk the zone was measured and used to calculate mean inhibition
zones.15
In general, all tested compounds possessed inhibitory spatiality of
selected the growth of gram positive and gram negative bacteria. In ad-
dition, the tested compounds showed a high inhibition towards Candida
albicans (Fungus) and Aspergills flvus (Fungus).
EXPERIMENTAL
All melting points were uncorrected. IR spectra were recorded (KBr
disc) on a Shimadzu FT-IR 8201 PC Spectrophotometer. 1H-NMR spec-
tra were recorded in CDCl3 or (CD3)3SO on a Varian Gemini 200 MHz
Spectrometer, and chemical shifts were expressed in δ units using TMS
as an internal reference. Elemental analyses were carried out at the
Microanalytical Center, Cairo University, Giza, Egypt. Hydrazonoyl
halides 4a–d were prepared as previously reported in literature.16−19
Synthesis of Alkyl Carbodithioates [3(a,b), 11(a,b), 14,
and 17(a,b)]
A mixture of the appropriate of 1, 10, 13, 14 (5 mmol), and the appro-
priate alkyl hydraziocarbodithioates 2a and 2b (5 mmol) in 2-propanol
(20 mL) was stirred at room temperature for 2 h. The resulting solid
was collected and recrystallized to give [3(a,b), 11(a,b), 14, and 17(a,b)],
respectively (Tables II and III).
Synthesis of 1,3,4-Thiadiazolines (8, 12)a–d, 15a–c, and 18a–c
Method A
Triethylamine [0.5 g (0.75 ml), 5 mmol] was added dropwise with
stirring to a mixture of the appropriate alkyl carbodithioates [3(a,b),
11(a,b), 14, and 17(a,b)], and the appropriate hydrazonoyl halides 4a–d
(5 mmol) in ethanol (20 mL). The resulting solid, which formed after 30
min, was collected and crystallized from the proper solvent to afford the
corresponding thiadiazolines (8, 12)a–d, 15a–c, and 18a–c, respectively
(Tables II and III).
Method B
A mixture of 1,3,4-thiadiazoline 9a (1.32 g, 5 mmol) and the appro-
priate 1, 10, 13, and 16 in 2-propanol (20 mL) was heated for 10 min and
then cooled. The resulting solid was collected and recrystallized from

1742
A. O. Abdelhamid et al.
TABLE II Characterization Data of the Newly Synthesized
Compounds
Calcd./found (%)
Comp.
No
Mp.◦C
(solvent)
Color
yield (%)
Mol. formula
(mol. wt.)
C
H
N
S
3a
3b
133–135
EtOH
170–172
EtOH
180–181
EtOH
170–172
EtOH
120–121
EtOH
184–185
EtOH
280–182
AcOH
>300
AcOH
230–132
AcOH
180–183
EtOH
>300
AcOH
190–192
EtOH
230–232
AcOH
240–242
AcOH
280–282
AcOH
255–256
AcOH
170–171
EtOH
180–181
AcOH
260–261
AcOH
230–232
AcOH
220–222
EtOH
180–182
EtOH
White
75
White
80
Yellow
80
Yellow
80
Orange
75
Yellow
80
Pale yellow
90
Pale yellow
90
Yellow
85
Yellow
85
Yellow
85
Yellow
85
Pale yellow
95
Pale yellow
95
Yellow
85
Orange
95
C13H14N2O3S2
31.38
50.30
50.03
59.04
59.10
58.41
58.21
59.70
59.60
64.45
64.54
62.51
62.31
49.69
49.72
57.93
57.72
57.49
57.32
58.66
58.44
63.27
63.42
61.47
61.23
51.71
51.52
58.77
58.66
55.99
56.21
64.36
64.63
48.96
48.85
58.24
58.14
59.67
60.00
64.85
64.75
62.28
62.32
66.12
66.22
69.45
69.25
74.09
74.24
4.55
4.45
4.69
4.85
4.45
4.35
4.24
4.23
4.16
4.25
4.32
4.52
4.17
4.12
4.38
4.27
4.19
3.91
4.02
4.23
3.93
4.20
4.01
3.88
3.47
3.74
3.70
3.50
3.50
3.70
3.47
3.64
5.22
5.11
4.88
4.52
4.74
4.52
4.53
4.35
4.40
4.32
4.35
4.36
4.23
4.32
4.54
4.45
9.02
8.95
7.24
20.65
20.56
16.59
16.32
7.08
6.89
7.58
7.85
6.61
6.42
6.41
6.23
18.95
18.85
15.47
15.32
6.67
6.72
7.12
7.21
6.25
6.45
6.07
5.86
18.41
18.32
6.54
6.45
6.96
7.12
6.14
6.43
23.74
23.54
7.78
7.95
8.38
8.52
7.21
7.45
8.74
8.62
6.30
6.20
5.61
5.81
7.61
7.52
C
19H18N2O3S2
386.48
7.15
8a
C
22H20N4O5S
452.37
12.38
12.31
13.26
13.20
11.56
11.65
14.02
14.24
8.28
8b
C
21H18N4O4S
422.45
8c
C
C
26H20N4O4S
484.53
26H21N5O4S
499.63
8d
11a
11b
12a
12b
12c
12d
14
C
C
14H14N2O4S2
338.39
20H18N2O4S2
414.29
8.32
6.76
6.54
C
23H20N4O6S
480.49
11.66
11.42
12.43
12.34
10.93
11.12
13.27
13.58
8.04
C
22H18N4O5S
450.46
C
C
27H20N4O5S
512.53
27H21N5O5S
527.55
C
15H12N2O4S2
348.40
8.12
15a
15b
15c
17a
18a
18b
18c
20
C24H18N4O6S
490.50
C23H16N4O5S
460.47
C28H18N4O5S
522.54
11.42
11.32
12.17
12.00
10.72
10.52
10.36
10.25
13.58
13.32
14.65
14.56
12.60
12.35
11.46
11.32
13.77
13.66
12.27
12.52
9.97
Pale yellow
90
Yellow
85
Orange
85
Red
80
Yellow
70
Red
80
C
11H14N2O2S2
270.36
C
20H20N4O4S
412.46
C19H18N4O3S
382.44
C24H20N4O3S
444.50
C19H16N3O3S
366.41
C28H22N5O3S
508.57
21a
21b
22
260–261
AcOH
238–240
EtOH
Red
80
Yellow
80
C
33H24N5O3S
570.64
C26H19N3OS
421.52
9.78

Reactions with Hydrazonoyl Halides 58
1743
TABLE III 1H NMR Spectra
Comp. No
1H NMR Spectra
3a
1H NMR: δ = 2.44 (s, 3H), 2.69 (s, 3H), 4.09 (s, 3H), 6.72–7.50 (m, 3H),
9.95 (s, br., 1H), 10.15 (s, 1H).
3b
8a
8b
1H NMR: δ = 2.64 (s, 3H), 4.0 (s, 3H), 4.13 (s, 2H), 6.72–7.50 (m, 8H), 9.95
(s, br., 1H), 10.15 (s, 1H).
1H NMR: δ = 1.44 (t, 3H), 2.61 (s, 3H), 4.05 (s, 3H), 4.44 (q, 2H), 6.82–8.06
(m, 8H), 11.45 (s, 1H).
1H NMR: δ = 2.29 (s, 3H), 2.61 (s, 3H), 4.05 (s, 3H), 6.70–8.06 (m, 8H),
12.16 (s, 1H).
8c
8d
11a
1H NMR: δ = 2.61 (s, 3H), 4.05 (s, 3H), 6.70–8.06 (m, 13H), 12.16 (s, 1H).
1H NMR: δ = 2.61 (s, 3H), 4.05 (s, 3H), 6.70–8.06 (m, 9H), 12.16 (s, 1H).
1H NMR: δ = 2.29 (s, 3H), 2.59 (s, 3H), 3.83 (s, 3H), 6.03 (s, 1H), 6.79
(s, 1H), 8.74 (s, 1H), 11.41 (s, 1H), 13.50 (s, 1H).
11b
12a
12b
12c
12d
14
1H NMR: δ = 2.59 (s, 3H), 3.83 (s, 3H), 4.21 (s, 1H), 6.03 (s, 1H), 6.79
(s, 1H), 8.74 (s, 1H), 11.41 (s, 1H), 13.50 (s, 1H).
1H NMR: δ = 1.45 (t, 3H), 2.30 (s, 3H), 3.95 (s, 3H), 5.99 (s, 1H), 6.73
(s, 1H), 7.25–7.94 (m, 5H), 8.90 (s, 1H), 12.12 (s, 1H).
1H NMR: δ = 2.30 (s, 3H), 2.64 (s, 3H), 3.94 (s, 3H), 5.99 (s, 1H), 6.72
(s, 1H), 7.41–7.99 (m, 5H), 8.89 (s, 1H), 12.10 (s, 1H).
1H NMR: δ = 2.64 (s, 3H), 3.94 (s, 3H), 5.99 (s, 1H), 6.72 (s, 1H), 7.41–7.99
(m, 10H), 8.89 (s, 1H), 12.10 (s, 1H).
1H NMR: δ = 2.64 (s, 3H), 3.94 (s, 3H), 5.99 (s, 1H), 6.72 (s, 1H), 7.41–7.99
(m, 10H), 8.89 (s, 1H), 11.45 (s, 1H), 12.10 (s, 1H).
1H NMR: δ = 2.73 (s, 3H), 4.12 (s, 3H), 6.78 (s, 1H), 7.33 (s, 1H), 8.10 (s,
1H), 8.37 (s, 1H), 8.75 (s, 1H), 10.06 (s, 1H), 13.35 (s, 1H).
1H NMR: δ = 1.42 (t, 3H), 4.19 (s, 3H), 4.47 (q, 2H), 7.04 (s, 1H), 7.26–7.61
(m, 7H), 8.51–8.66 (d, 1H).
15a
15b
1H NMR: δ = 2.58 (s, 3H), 4.11 (s, 3H), 7.397.61 (m, 8H), 8.41 (s, 1H), 8.63
(s, 1H).
15c
17a
1H NMR: δ = 4.11 (s, 3H), 7.397.61 (m, 8H), 8.41 (s, 1H), 8.63 (s, 1H).
1H NMR: δ = 2.67 (s, 3H), 3.86 (s, 6H), 6.44 (s, 1H), 6.53–6.57 (d, 1H),
7.90–7.95 (d, 1H), 8.22 (s, 1H), 10.26 (s, 1H).
18a
18b
18c
20
1H NMR: δ = 1.44 (t, 3H), 3.84 (s, 6H), 6.43–6.58 (m, 2H), 7.27–7.50 (m,
3H), 7.97–8.01 (m, 3H), 8.78 (s, 1H).
1H NMR: δ = 2.67 (s, 3H), 3.88 (s, 6H), 6.43–6.59 (m, 2H), 7.30–7.53 (m,
3H), 7.98–8.08 (m, 3H), 8.74 (s, 1H).
1H NMR: δ = 3.88 (s, 6H), 6.43–6.59 (m, 2H), 7.30–7.53 (m, 8H),
7.98V8.08 (m, 3H), 8.74 (s, 1H).
1H NMR: δ = 3.88 (s, 3H), 3.46 (dd, 1H, J = 18.1, 5.8 Hz, CH2 (pyraz), 3.82
((dd, 1H, J = 18.1, 12.2 Hz, CH2 (pyraz)), 3.76 (s, 3H), 4.14 ((dd, 1H, J =
12.2, 5.8 Hz, CH2 (pyraz)), 6.84–7.51 (m, 7H), 8.57 (s, 1H), 10.60 (s, 1H).
1H NMR: δ = 2.54 (s, 3H), 3.46 (dd, 1H, J = 18.1, 5.8 Hz, CH2 (pyraz), 3.82
((dd, 1H, J = 18.1, 12.2 Hz, CH2 (pyraz)), 4.03 (s, 3H), 4.14 ((dd, 1H, J =
12.2, 5.8 Hz, CH2 (pyraz)), 6.86–7.43 (m, 13H), 11.05 (s, 1H).
21b

1744
A. O. Abdelhamid et al.
acetic acid to give (8, 12)a–d, 15a–c, and 18a–c, respectively (Tables II
and III).
Synthesis of Pyrazolines 20
A mixture of 5-[1-aminothiomethoxy)-5-phenyl-2-pyrazolin-3-yl)]-4-
methoxybenzo[b]furan-6-ol (19) (2.94 g, 10 mmol), thiosemicarbazide
(0.91 g, 10 mmol) and acetic acid (20 mL) was heated for 6 h. The
resulting solid was collected and recrystallized from ethanol to give
pyrazoline 20 (Tables II and III).
Synthesis of 4-Methoxy-5-[5-phenyl-1-(4-phenyl(1,3-thiazol-2-
yl)]benzo[b]furan-6-ol (22)
A mixture of 20 (1.8 g, 5 mmol) and phenacyl bromide (0.99 g, 5 mmol)
in ethanol was heated for 3 h. The resulting solid was collected and
recrystallized from ethanol to give 22 (Tables I and II).
5-{1-[4-Substituted-5-phenyldiazenyl)(1,3-thiazol-2-yl]-5-
phenyl-2-pyrazolin-3-yl)}-4-methoxybenzo[b]furan-6-ols 21a,
21b
Method A
A mixture of 20 (1.9 g, 5 mmol), the appropriate hydrazonoyl halides
4c,d (5 mmol), and triethylamine (0.75 mL, 5 mmol) in chloroform
(20 mL) was heated for 10 hrs. The solvent was evaporated under re-
duce pressure, and the resulting solid was collected and recrystallized
from the proper solvent to give 21a and 21b, respectively (Tables II and
III).
Method B
Benzenediazonium chloride (5 mmol) was added dropwise to a cold
solution of 22 (2.1 g, 5 mmol) in pyridine (25 mL) at 0–5◦C while stirring.
The reaction mixture was stirred for 3 h at 0–5◦C, and the resulting
solid was collected and recrystallized from acetic acid to give product
identical in all aspects (mp, mixed mp, and spectra) with 21b.
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