Synthesis of Methyl 2-arylthio-5 -aryldiazenylbenzoates by Formal [3+3]Cyclizations of 3-arylthio-1-silyloxy-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones

Article abstract of DOI:10.1080/10426507.2013.818999

The formal [3+3]cyclization of 3-arylthio-1-silyloxy-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones afforded a variety of 2-arylthio-5- aryldiazenylbenzoates.

Full text of DOI:10.1080/10426507.2013.818999

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Synthesis of Methyl 2-arylthio-5 -
aryldiazenylbenzoates by Formal
[3+3]Cyclizations of 3-arylthio-1-
silyloxy-1,3-butadienes with 2-
aryldiazenyl-3-silyloxy-2-en-1-ones
Muhammad Imran a , Inam Iqbal a , Zharylkasyn A. Abilov b & Peter
Langer a c
a Institut für Chemie , Universität Rostock , Albert-Einstein-Str. 3a,
18059 , Rostock , Germany
b Al-Farabi Kazakh National University , Al-Farabi Ave. 71, 050040 ,
Almaty , Kazakhstan
Click for updates
c Leibniz-Institut für Katalyse e. V. an der Universität Rostock ,
Albert-Einstein-Str. 29a, 18059 , Rostock , Germany
Accepted author version posted online: 12 Aug 2013.Published
online: 03 Dec 2013.
To cite this article: Muhammad Imran , Inam Iqbal , Zharylkasyn A. Abilov & Peter Langer (2014)
Synthesis of Methyl 2-arylthio-5 -aryldiazenylbenzoates by Formal [3+3]Cyclizations of 3-arylthio-1-
silyloxy-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones, Phosphorus, Sulfur, and Silicon and
the Related Elements, 189:2, 255-262, DOI: 10.1080/10426507.2013.818999
To link to this article: http://dx.doi.org/10.1080/10426507.2013.818999
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Phosphorus, Sulfur, and Silicon, 189:255–262, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2013.818999
SYNTHESIS OF METHYL 2-ARYLTHIO-5
-ARYLDIAZENYLBENZOATES BY FORMAL
[3+3]CYCLIZATIONS OF
3-ARYLTHIO-1-SILYLOXY-1,3-BUTADIENES WITH
2-ARYLDIAZENYL-3-SILYLOXY-2-EN-1-ONES
Muhammad Imran,1 Inam Iqbal,1 Zharylkasyn A. Abilov,2
and Peter Langer1,3
1Institut fu¨r Chemie, Universita¨t Rostock, Albert-Einstein-Str. 3a 18059, Rostock,
Germany
2Al-Farabi Kazakh National University, Al-Farabi Ave. 71 050040, Almaty,
Kazakhstan
3Leibniz-Institut fu¨r Katalyse e. V. an der Universita¨t Rostock, Albert-Einstein-Str.
29a 18059, Rostock, Germany
GRAPHICAL ABSTRACT
ArS
OSiMe3
R1
O
R
SAr
OR2
O
R1
R
+
OR2
TiCl4
Me3SiO
R
R
N
N
N
Ar
N
Ar
Abstract The formal [3+3]cyclization of 3-arylthio-1-silyloxy-1,3-butadienes with 2-
aryldiazenyl-3-silyloxy-2-en-1-ones afforded a variety of 2-arylthio-5-aryldiazenylbenzoates.
Keywords Azo compounds; cyclizations; diazenes; silyl enol ethers
INTRODUCTION
Diaryldiazenes are of considerable relevance as pigments and dyes.1 In addition,
they exhibit pharmacological activity, such as anti-cancer, cytotoxic, apoptosis-inducing,
antiallergic, antihistaminic, protein-binding activity.2 Diaryldiazenes are available by
Received 18 April 2013; accepted 23 May 2013.
Financial support by the State of Mecklenburg-Vorpommern (Landesgraduierten scholarship for M. I.), by
the State of Pakistan (HEC scholarship for I. I.), and by DFG-TWAS is gratefully acknowledged.
Address correspondence to Peter Langer, Institut fu¨r Chemie, Universita¨t Rostock, Albert-Einstein-Str. 3a,
18059 Rostock, Germany. E-mail: peter.langer@uni-rostock.de
255

256
M. IMRAN ET AL.
Table 1 Synthesis of 5a-o
2
4
5
Ar1
Ar2
% (5)a
a
a
a
a
a
a
a
b
b
b
b
b
b
b
b
a
b
c
d
e
f
g
e
f
b
c
d
g
a
h
a
b
c
d
e
4-ClC6H4
3-MeC6H4
4-EtC6H4
3-(MeO)C6H4
Ph
Ph
Ph
Ph
Ph
Ph
51
58
57
63
64
59
50
61
59
57
58
61
49
51
50
f
4-MeC6H4
Ph
Ph
g
h
i
j
k
l
m
n
o
C
10H7
Ph
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
3-MeC6H4
4-EtC6H4
3-(MeO)C6H4
C10H7
4-ClC6H4
3-FC6H4
aYields of isolated products.
electrophilic substitution reactions of benzene derivatives with aryldiazonium salts. Re-
cently, we developed an alternative strategy that is based on formal [3+3]cyclization
of 2-aryldiazenyl-3-silyloxy-2-en-1-ones with 1,3-bis(silyloxy)-1,3-butadienes.3 Other re-
searchers reported the synthesis of aryl-hetaryl-diazenes by cyclization of 2-aryldiazenyl-
1,3-diones with various dinucleophiles, such as guanidine, sulfuryl diamide, hydroxy-
lamine, hydrazines, hydrazides, and anilines.4 Herein, we wish to report, for the first
time, the synthesis of 2-arylthio-5-aryldiazenylbenzoates by cyclization of 3-arylthio-1-
silyloxy-1,3-butadienes, which can be regarded as sulfur analogs of 1,3-bis(silyloxy)-1,3-
butadienes,5,6 with 2-aryldiazenyl-3-silyloxy-2-en-1-ones.
RESULTS AND DISCUSSION
The reaction of pentane-2,4-dione with aniline and p-toluidine gave the known 2-
aryldiazenyl-1,3-diones 1a,b (Scheme 1).4 h The silylation of 1a,b gave the 2-aryldiazenyl-
3-silyloxy-2-en-1-ones 2a,b. The TiCl4 mediated cyclization of 2a,b with 3-arylthio-1-
silyloxy-1,3-butadienes 4a-g afforded the arylthio-substituted diazenes 5a-o with 50–64%
yields (Scheme 1, Table 1). Dienes 4a-g are readily available from methyl acetoacetate and
the corresponding thiophenols via enol the thioethers 3a-g (Scheme 2).5,6 The cyclization
reactions proceeded in moderate to good yields for various dienes 4. The yields of the prod-
ucts derived from dienes containing electron-rich aryl groups (e.g., Ar1 = 3-(MeO)C6H4)
are, in general, higher as compared to the yields of products derived from dienes containing
electron-poor aryl groups (e.g., Ar1 = 4-ClC6H4). This can be explained by the higher
nucleophilicity of the dienes containing electron-rich aryl groups. The yields of products
derived from dienes containing sterically hindered aryl groups (e.g., C10H7) are relatively
low.
In conclusion, we have reported formal [3+3]cyclization reactions of 3-arylthio-
1-silyloxy-1,3-butadienes with readily available 2-aryldiazenyl-3-silyloxy-2-en-1-ones.
These reactions provided a convenient approach to various methyl 2-arylthio-5-
aryldiazenylbenzoates, which are not readily available by other methods.

SYNTHESIS OF METHYL 2-ARYLTHIO-5-ARYLDIAZENYLBENZOATES
257
Scheme 1 Synthesis of 5a-o.
Scheme 2 Synthesis of 4a-g.5,6
EXPERIMENTAL SECTION
General
All solvents were dried by standard methods and all reactions were carried out under
an inert atmosphere. For 1H (CDCl3, 250 MHz) and 13C NMR (CDCl3, 63 MHz) spectra,
the deuterated solvents indicated were used. Mass spectrometric (MS) data were obtained
by electron ionization (EI, 70 eV), chemical ionization (CI, isobutane), or electrospray

258
M. IMRAN ET AL.
ionization (ESI). For preparative scale chromatography, silica gel 60 (0.063–0.200 mm,
70–230 mesh) was used.
Typical Experimental Procedure for the Synthesis of 5a-o
To CH2Cl2 solutions (5 mL/mmol of 2) of 2 (276 mg, 1.0 mmol,) and 4 was added
TiCl4 (0.25 mL, 2.25 mmol,) at –78◦C. The solution was allowed to warm to 20 ◦C within
20 h. To the mixture was added aqu. HCl (10%). The organic and the aqueous layers were
separated and the latter was extracted with CH2Cl2 (3 × 20 mL). The combined organic
layers were dried (Na2SO4), filtered, and the filtrate was concentrated in vacuo. The residue
was purified by chromatography (silica gel, EtOAc/n-heptane 1:4).
Methyl 6-(4-Chlorophenyl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)
benzoate (5a). Compound 5a was obtained from 2a and 4a (471 mg, 1.5 mmol) as
1
a highly viscous oil (313.65 mg, 51%). H NMR: δ = 1.82 (s, 3H, CH3), 2.33 (s, 3H,
CH3), 3.73 (s, 3H, OCH3), 6.75–7.57 (m, 10H, ArH). 13C NMR: δ = 16.7, 23.9 (CH3),
52.0 (OCH3), 109.9 (ArCH), 113.0 (2C ArCH), 120.9 (ArCH), 126.8 (ArC), 127.8, 128.1
(2C ArCH), 129.2, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC),
194.9 (C). IR (neat): 3056 (w), 2990 (w), 2947 (w), 2920 (w), 1726 (s), 1599 (m), 1581
(w), 1516 (w), 1476 (m), 1438 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188 (m), 1151
(s), 1078 (s), 1023 (m), 999 (w), 956 (w), 852 (m), 810 (m), 738 (s), 689 (s), 579 (m), 555
(w) cm−1. GC-MS (EI, 70 eV): m/z (%): 410 (60), 241 (41), 240 (21), 239 (M+, 100), 198
(15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C22H19O2SN2Cl 410.08655, found
410.086221.
Methyl 6-(3-Methylphenyl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)
benzoate (5b). Compound 5b was obtained from 2a and 4b (441 mg, 1.5 mmol) as a
highly viscous oil (335.8 mg, 58%). 1H NMR: δ = 1.82 (s, 3H, CH3), 1.89 (s, 3H, CH3),
2.28 (s, 3H, CH3), 3.51 (s, 3H, OCH3), 6.55–7.48 (m, 10H, ArH). 13C NMR: δ = 16.7,18.3,
23.9 (CH3), 52.1 (OCH3), 109.2 (ArCH), 112.7 (2C ArCH), 120.6 (ArCH), 125.9 (ArC),
125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 164.8,
165.2 (ArC), 194.9 (C). IR (neat): 3049 (w), 2992 (w), 2949 (w), 2917 (w), 1726 (s), 1599
(m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188
(m), 1151 (s), 1078 (s), 1020 (m), 999 (w), 956 (w), 852 (m), 815 (m), 736 (s), 689 (s),
579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 386 (100), 386 (50), 366 (62), 311
(39), 240 (21), 239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for
C23H22O2SN2 390.079155, found 390.069213.
Methyl 6-(4-Ethylphenyl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)
benzoate (5c). Compound 5c was obtained from 2a and 4c (462 mg, 1.5 mmol) as
1
a highly viscous oil (345.4 mg, 57%). H NMR: δ = 1.10 (t, J = 7.5 Hz, 3H, CH3),
2.23 (s, 3H, CH3), 2.25 (s, 3H, CH3), 2.46 (q, J = 7.5 Hz, 2H, CH2CH3), 3.51 (s, 3H,
OCH3), 6.59–7.77 (m, 10H, ArH). 13C NMR: δ = 15.3, 18.3, 23.9 (CH3), 28.5 (CH2),
52.3 (OCH3), 109.2 (ArCH), 112.9 (2C ArCH), 120.6 (ArCH), 125.9 (ArC), 125.9, 127.9
(2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC),
194.9 (C). IR (neat): 3048 (w), 2999 (w), 2948 (w), 2917 (w), 1726 (s), 1599 (m), 1585
(w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1266 (s), 1257 (s), 1217 (m), 1188 (m), 1151
(s), 1078 (s), 1020 (m), 999 (w), 956 (w), 855 (m), 815 (m), 736 (s), 689 (s), 579 (m), 555
(w) cm−1. GC-MS (EI, 70 eV): m/z (%): 404 (100), 403 (19), 366 (62), 311 (39), 240 (21),
239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C24H24O2SN2
404.050701, found 404.050515.

SYNTHESIS OF METHYL 2-ARYLTHIO-5-ARYLDIAZENYLBENZOATES
259
Methyl 6-(3-Methoxyphenyl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-
yl)benzoate (5d). Compound 5d was obtained from 2a and 4d (465.3 mg, 1.5 mmol) as
a highly viscous oil (383.6 mg, 63%). 1H NMR: δ = 1.98 (s, 3H, CH3), 2.28 (s, 3H, CH3),
3.49 (s, 3H, OCH3), 3.52 (s, 3H, OCH3), 6.55–7.48 (m, 10H, ArH). 13C NMR: δ = 18.3,
23.9 (CH3), 50.7 (OCH3), 52.1 (OCH3), 109.2 (ArCH), 112.7 (2C ArCH), 120.6 (ArCH),
125.9 (ArC), 125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH),
158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3048 (w), 2990 (w), 2949 (w), 2917 (w),
1726 (s), 1599 (m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s),
1217 (m), 1188 (m), 1151 (s), 1073 (s), 1020 (m), 999 (w), 956 (w), 852 (m), 815 (m), 736
(s), 689 (s), 579 (m), 557 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 406 (98), 397 (50), 366
(62), 311 (39), 240 (21), 239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI):
calcd. for C23H22O3SN2 406.078155, found 406.068217.
Methyl 6-Phenylsulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)benzoate
(5e). Compound 5e was obtained from 2a and 4e (420 mg, 1.5 mmol) as a highly viscous
1
oil (360.9 mg, 64%). H NMR: δ = 2.08 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.51 (s, 3H,
OCH3), 6.75–7.87 (m, 10H, ArH). 13C NMR: δ = 18.3, 23.9 (CH3), 51.8 (OCH3), 108.8
(ArCH), 113.0 (2C ArCH), 120.7 (ArCH), 125.9 (ArC), 125.9, 128.2 (2C ArCH), 128.9,
135.4, 135.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat):
3059 (w), 3049 (w), 2992 (w), 2949 (w), 2917 (w), 1726 (s), 1599 (m), 1585 (w), 1516
(w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188 (m), 1151 (s), 1078
(s), 1020 (m), 998 (w), 956 (w), 852 (m), 815 (m), 736 (s), 689 (s), 579 (m), 555 (w) cm−1
.
GC-MS (EI, 70 eV): m/z (%): 377 (11), 376 (M+ 100), 366 (62), 311 (39), 240 (21), 198
(15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C22H20O2SN2 376.079155, found
376.069213.
Methyl 6-(4-Methylphenyl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)
benzoate (5f). Compound 5f was obtained from 2a and 4f (441 mg, 1.5 mmol) as
1
a highly viscous oil (345.1 mg, 59%). H NMR: δ = 1.88 (s, 3H, CH3), 1.89 (s, 3H,
CH3), 2.29 (s, 3H, CH3), 3.61 (s, 3H, OCH3), 6.95–7.88 (m, 10H, ArH). 13C NMR: δ =
16.7, 18.3, 23.9 (CH3), 52.1 (OCH3), 109.2 (ArCH), 112.7 (2C ArCH), 120.6 (ArCH),
125.9 (ArC), 125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH),
158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3043 (w), 3021 (w), 2992 (w), 2949
(w), 2917 (w), 1726 (s), 1599 (m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w),
1267 (s), 1257 (s), 1217 (m), 1188 (m), 1151 (s), 1078 (s), 1020 (m), 997 (w), 956 (w),
852 (m), 815 (m), 736 (s), 689 (s), 579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z
(%): 391 (11), 390 (98), 386 (50), 366 (62), 311 (39), 240 (21), 239 (M+, 100), 198
(15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C23H22O2SN2 390.079155, found
390.069213.
Methyl 6-(Napth-2-yl)sulfanyl-2,4-dimethyl-3-(2-phenyldiazen-1-yl)ben-
zoate (5g). Compound 5g was obtained from 2a and 4g (495 mg, 1.5 mmol) as a highly
viscous oil (319.5 mg, 50%). 1H NMR: δ = 2.08 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.51 (s,
3H, OCH3), 6.98–7.84 (m, 13H, ArH). 13C NMR: δ = 18.3, 23.9 (CH3), 51.8 (OCH3),
108.8, 111.4 (ArCH), 113.0 (2C ArCH), 120.7 (ArCH), 125.9 (2C ArC), 125.9, 128.2 (2C
ArCH), 128.9, 129.4 (ArCH), 134.2, 135.4, 135.7 (ArC), 141.9, 142.7 (ArCH), 158.3,
162.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3059 (w), 3049 (w), 2992 (w), 2949 (w),
2917 (w), 1726 (s), 1599 (m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s),
1257 (s), 1217 (m), 1188 (m), 1151 (s), 1078 (s), 1020 (m), 998 (w), 956 (w), 852 (m),
815 (m), 736 (s), 689 (s), 579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 463 (11),

260
M. IMRAN ET AL.
462 (M+ 100), 366 (66), 311 (56), 240 (21), 198 (15), 197 (26), 165 (6), 91 (4). HRMS
(EI): calcd. for C26H22O2SN2 426.0756155, found 426.069211.
Methyl
6-Phenylsulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)diazen-1-
yl]benzoate
(5h). Compound 5h was obtained from 2b and 4e (465 mg, 1.5 mmol) as a highly viscous
oil (384.3 mg, 61%). 1H NMR: δ = 2.0 (s, 3H, CH3), 2.12 (s, 3H, CH3), 2.28 (s, 3H, CH3),
3.51 (s, 3H, OCH3), 6.79–7.98 (m, 10H, ArH). 13C NMR: δ = 16.7,18.3, 23.9 (CH3),
52.1 (OCH3), 109.2 (ArCH), 112.7 (2C ArCH), 120.6 (ArCH), 125.9 (ArC), 125.9, 127.9
(2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC),
194.9 (C). IR (neat): 3048 (w), 2917 (w), 1726 (s), 1599 (m), 1585 (w), 1516 (w), 1476
(m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188 (m), 1151 (s), 1078 (s), 1020
(m), 999 (w), 956 (w), 852 (m), 815 (m), 736 (s), 689 (s), 579 (m), 555 (w) cm−1. GC-MS
(EI, 70 eV): m/z (%): 421 (12), 420 (87), 386 (50), 366 (62), 311 (39), 240 (21), 239
(M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C24H24O3SN2
420.069155, found 420.056213.
Methyl 6-(4-Methylphenyl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)di
azen-1-yl]benzoate (5i). Compound 5i was obtained from 2b and 4f (441 mg, 1.5 mmol)
1
as a highly viscous oil (357.5 mg, 59%). H NMR: δ = 2.01 (s, 3H, CH3), 2.08 (s, 3H,
CH3), 2.22 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.55 (s, 3H, OCH3), 6.79–7.98 (m, 9H,
ArH). 13C NMR: δ = 16.7, 18.3, 21.5, 23.9 (CH3), 52.7 (OCH3), 112.7 (2C ArCH), 120.6
(ArCH), 125.9 (ArC), 125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9, 142.7
(ArCH), 156.9, 158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3066 (w), 2909 (w), 1726
(s), 1599 (m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217
(m), 1188 (m), 1151 (s), 1078 (s), 1020 (m), 999 (w), 956 (w), 852 (m), 815 (m), 736 (s),
689 (s), 579 (m), 553 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 405 (9), 404 (90), 386 (50),
366 (62), 311 (39), 240 (21), 239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS
(EI): calcd. for C24H24O2SN2 404.069155, found 404.056210.
Methyl 6-(3-Methylphenyl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)di
azen-1-yl]benzoate (5j). Compound 5j was obtained from 2b and 4b (441 mg,
1.5 mmol) as a highly viscous oil (345.4 mg, 57%). 1H NMR: δ = 2.03 (s, 3H, CH3), 2.08
(s, 3H, CH3), 2.22 (s, 3H, CH3), 2.29 (s, 3H, CH3), 3.51 (s, 3H, OCH3), 6.74–7.91 (m,
9H, ArH). 13C NMR: δ = 16.6,18.3, 21.5, 23.9 (CH3), 52.7 (OCH3), 112.7 (2C ArCH),
120.6 (ArCH), 125.9 (ArC), 125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 141.9,
142.7 (ArCH), 156.9, 158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3066 (w), 2909
(w), 1726 (s), 1599 (m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257
(s), 1217 (m), 1188 (m), 1151 (s), 1078 (s), 1020 (m), 999 (w), 956 (w), 852 (m), 815 (m),
736 (s), 689 (s), 579 (m), 553 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 405 (11), 404 (96),
386 (50), 366 (62), 311 (39), 240 (21), 239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4).
HRMS (EI): calcd. for C24H24O2SN2 404.069155, found 404.056216.
Methyl 6-(4-Ethylphenyl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)di
azen-1-yl]benzoate (5k). Compound 5k was obtained from 2b and 4c (462 mg,
1
1.5 mmol) as a highly viscous oil (363.6 mg, 58%). H NMR: δ = 1.10 (t, J = 7.5 Hz,
3H, CH3), 2.19 (s, 3H, CH3), 2.23 (s, 3H, CH3), 2.25 (s, 3H, CH3), 2.46 (q, J = 7.5 Hz,
2H, CH2CH3), 3.51 (s, 3H, OCH3), 6.69–7.89 (m, 9H, ArH). 13C NMR: δ = 15.3, 16.9,
18.3, 23.9 (CH3), 28.5 (CH2), 52.3 (OCH3), 109.2 (ArCH), 112.9 (2C ArCH), 120.6
(ArCH), 125.9 (ArC), 125.9, 127.9 (2C ArCH), 129.1, 134.5, 134.7 (ArC), 138.5 (2ArC),
141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC), 194.9 (C). IR (neat): 3049 (w), 2999 (w),

SYNTHESIS OF METHYL 2-ARYLTHIO-5-ARYLDIAZENYLBENZOATES
261
2948 (w), 2917 (w), 1720 (s), 1599 (m), 1585 (w), 1515 (w), 1476 (m), 1437 (s), 1378
(w), 1266 (s), 1257 (s), 1217 (m), 1188 (m), 1151 (s), 1078 (s), 1020 (m), 999 (w), 956
(w), 855 (m), 815 (m), 736 (s), 689 (s), 579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z
(%): 418 (100), 417 (19), 366 (62), 311 (39), 240 (21), 239 (M+, 100), 198 (15), 197 (26),
165 (6), 91 (4). HRMS (EI): calcd. for C25H26O2SN2 418.050701, found 418.050515.
Methyl 6-(3-Methoxyphenyl)sulfanyl-2,4-dımethyl-3-[2-(4-methylphenyl)
diazen-1-yl]benzoate (5l). Compound 5l was obtained from 2b and 4d (465.3 mg,
1
1.5 mmol) as a highly viscous oil (384.3 mg, 61%). H NMR: δ = 1.92 (s, 3H, CH3),
1.98 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.50 (s, 3H, OCH3), 3.51 (s, 3H, OCH3), 6.55–7.48
(m, 9H, ArH). 13C NMR: δ = 16.7, 18.3, 23.9 (CH3), 50.7 (OCH3), 52.1 (OCH3), 109.2
(ArCH), 112.7 (2C ArCH), 118.6, 120.6 (ArCH), 125.9 (ArC), 125.9, 127.9 (ArCH),
129.1, (ArC), 134.5, 134.7 (2ArC), 141.9, 142.7 (ArCH), 158.3, 164.8, 165.2 (ArC), 194.9
(C). IR (neat): 3049 (w), 2990 (w), 2949 (w), 2917 (w), 1726 (s), 1599 (m), 1585 (w),
1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188 (m), 1151 (s),
1073 (s), 1020 (m), 999 (w), 956 (w), 852 (m), 815 (m), 736 (s), 689 (s), 579 (m), 557
(w) cm−1. GC-MS (EI, 70 eV): m/z (%): 420 (98), 397 (50), 366 (62), 311 (39), 240 (21),
239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C24H24O3SN2
420.078155, found 420.06821.
Methyl 6-(Napth-2-yl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)diaz
en-1-yl]benzoate (5m). Compound 5m was obtained from 2b and 4g (495 mg,
1
1.5 mmol) as a highly viscous oil (323.4 mg, 49%). H NMR: δ = 1.91 (s, 3H, CH3),
2.08 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.51 (s, 3H, OCH3), 6.98–7.74 (m, 12H, ArH). 13
C
NMR: δ = 18.3, 20.2, 23.9 (CH3), 52.7 (OCH3), 110.2, 111.4 (ArCH), 113.0 (2C ArCH),
120.7 (ArCH), 125.9 (2C ArC), 125.9, 126.8 (2C ArCH), 127.8, 128.9, 129.4 (ArCH),
133.2, 134.2, 135.4, 135.7 (ArC), 141.9, 142.7 (ArCH), 158.3, 162.3, 164.8, 165.2 (ArC),
194.9 (C). IR (neat): 3059 (w), 3049 (w), 2992 (w), 2949 (w), 2917 (w), 1726 (s), 1599
(m), 1585 (w), 1516 (w), 1476 (m), 1437 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m), 1188
(m), 1151 (s), 1078 (s), 1020 (m), 998 (w), 956 (w) 852 (m), 815 (m), 736 (s), 689 (s), 579
(m), 557 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 441 (11), 440 (M+ 100), 366 (66), 311
(56), 240 (21), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd. for C27H24O2SN2
440.0756155, found 440.069211.
Methyl 6-(4-Chlorophenyl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)di
azen-1-yl]benzoate (5n). Compound 5n was obtained from 2b and 4a (471 mg,
1
1.5 mmol) as a highly viscous oil (324.3 mg, 51%). H NMR: δ = 1.82 (s, 3H, CH3),
2.26 (s, 3H, CH3), 2.33 (s, 3H, CH3), 3.73 (s, 3H, OCH3), 6.75–7.59 (m, 9H, ArH). 13C
NMR: δ = 16.7, 19.5, 23.9 (CH3), 52.0 (OCH3), 109.7, 113.0 115.5 (ArCH), 126.8 (ArC),
127.8, 128.1 (2C ArCH), 129.2, 134.5, 134.7, 140.1 (ArC), 141.9, 142.7 (ArCH), 164.8,
165.2 (2C ArC), 194.9 (C). IR (neat): 3049 (w), 2980 (w), 2947 (w), 2920 (w), 1726 (s),
1599 (m), 1581 (w), 1516 (w), 1476 (m), 1438 (s), 1378 (w), 1267 (s), 1257 (s), 1217 (m),
1188 (m), 1151 (s), 1078 (s), 1023 (m), 999 (w), 956 (w), 852 (m), 810 (m), 738 (s), 689
(s), 579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 426 (41), 424 (60), 412 (41),
398 (40), 240 (21), 239 (M+, 100), 198 (15), 197 (26), 165 (6), 91 (4). HRMS (EI): calcd.
for C23H21O2SN2Cl 424.08655, found 424.086221.
Methyl 6-(3-Fluorophenyl)sulfanyl-2,4-dimethyl-3-[2-(4-methylphenyl)di
azen-1-yl]benzoate (5o). Compound 5o was obtained from 2b and 4h (445 mg,
1
1.5 mmol) as a highly viscous oil (306.4 mg, 50%). H NMR: δ = 1.92 (s, 3H, CH3),
2.30 (s, 3H, CH3), 2.39 (s, 3H, CH3), 3.83 (s, 3H, OCH3), 6.75–7.99 (m, 9H, ArH). 13C

262
M. IMRAN ET AL.
NMR: δ = 16.7, 19.5, 23.9 (CH3), 52.0 (OCH3), 109.7, 113.0, 115.5 (ArCH), 126.8 (ArC),
127.8, 128.1 (2C ArCH), 129.2, 134.5, 134.7, 140.1 (ArC), 141.9, 142.7 (ArCH), 164.8,
165.2 (2C ArC), 194.9 (C). IR (neat): 3059 (w), 2990 (w), 2947 (w), 2920 (w), 1726 (s),
1599 (m), 1581 (w), 1516 (w), 1476 (m), 1438 (s), 1378 (w), 1267 (s), 1257 (s), 1217
(m), 1188 (m), 1151 (s), 1078 (s), 1023 (m), 999 (w), 956 (w), 852 (m), 810 (m), 738 (s),
689 (s), 579 (m), 555 (w) cm−1. GC-MS (EI, 70 eV): m/z (%): 409 (41), 408 (23), 398
(40), 240 (21), 239 (M+, 100), 198 (45), 199 (28), 169 (6), 95 (4). HRMS (EI): calcd. for
C23H21O2SN2F 409.07655, found 409.06221.
REFERENCES
1. (a) Hunger, K. (ed.). Industrial Dyes, Wiley: New York, 2002. (b) Deichmann, U. Flu¨chten,
Mitmachen, Vergessen, Wiley-VCH: Weinheim, 2001. (c) Sainsbury, M. Aromatenchemie, VCH:
Weinheim, 1995.
2. (a) Baures, P. W.; Peterson, S. A.; Kelly, J. W. Bioorg. Med. Chem. 1998, 6, 1389–1401.
(b) Irvine, J. D.; Takahashi, L.; Lockhart, K.; Cheong, J.; Tolan, J. W.; Selick, H. E.; Grove,
J. R. J. Pharm. Sci. 1999, 88, 28–33. (c) Pruzanski, W.; Stefanski, E.; Vadas, P.; Ramamurthy,
N. S. Biochem. Pharm. 1997, 53, 1901-1907. (d) Hibi, S.; Okamoto, Y.; Tagami, K.; Numata,
H.; Kobayashi, N.; Shinoda, M.; Kawahara, T.; Murakami, M.; Oketani, K.; Inoue, T.; Shibata,
H.; Yamatsu, I. J. Med. Chem. 1994, 37, 3062-3070. (e) Pellicciari, R.; Garzon-Aburbeh, A.;
Natalini, B.; Marinozzi, M.; Clerici, C.; Gentili, G.; Morelli, A. J. Med. Chem. 1993, 36, 4201-
4207. (f) Brown, J. P.; McGarraugh, G. V.; Parkinson, T. M.; Wingard, R. E., Jr.; Onderdonk, A.
B. J. Med. Chem. 1983, 26, 1300-1307.
3. Hefner, J.; Langer, P. Tetrahedron Lett. 2008, 49, 2262-2264.
4. (a) Brown, H.; Kipp, H. Cancer Res. 1970, 30, 2089-2090. (b) Liang, E.; Proudfoot, J.; Yazdanian,
M. Pharm. Res. 2000, 17, 1168-1174. (c) Lee, E. H.; Kim, H. M. Pharmacology. 1998, 56, 223-
229. (d) Liptay, S.; Fulda, S.; Schanbacher, M.; Bourteele, S.; Ferri, K. F.; Kroemer, G.; Adler,
G.; Debatin, K. M.; Schmid, R. M. Br. J. Pharmacol. 2002, 137, 608-620. (e) Korpimaki, T.;
Hagren, V.; Brockmann, E. C.; Tuomola, M. Anal. Chem. 2004, 76, 3091-3098. (f) Matsson, P.;
Bergstroem, C. A. S.; Nagahara, N.; Tavelin, S.; Norinder, U.; Artursson, P. J. Med. Chem. 2005,
48, 604-613. (g) Irvine, J. D.; Takahashi, L.; Lockhart, K.; Cheong, J.; Tolan, J. W. J. Pharm.
Sci. 1999, 88, 28-33. (h) Kimura, I.; Kawasaki, M.; Nagahama, S.; Matsuda, A.; Kataoka, M.;
Kokuba, Y. Arzneim. Forsch. 1998, 48, 1091-1096. (i) Pruzanski, W.; Stefanski, E.; Vadas,
P.; Ramamurthy, N. S. Biochem. Pharmacol. 1997, 53, 1901-1907. (j) Hibi, S.; Okamoto, Y.;
Tagami, K.; Numata, H.; Kobayashi, N. J. Med. Chem. 1994, 37, 3062-3070. (k) Pellicciari,
R.; Garzon-Aburbeh, A.; Natalini, B.; Marinozzi, M.; Clerici, C. J. Med. Chem. 1993, 36, 4201-
4207. (l) Brown, J. P.; McGarraugh, G. V.; Parkinson, T. M.; Wingard, R. E.; Onderdonk, A. B.
J. Med. Chem. 1983, 26, 1300-1307.
5. (a) Feist, H.; Langer, P. Synthesis 2007, 327-347 (review on [3+3]cyclization reactions).
(b) Langer, P. Synthesis 2002, 441-459 (review on 1,3-bis(trimethylsilyloxy)-1,3-dienes in
general).
6. (a) Imran, M.; Iqbal, I.; Rasool, N.; Fischer, C.; Langer, P. Tetrahedron 2009, 65, 8794-8801.
(b) Iqbal, I.; Imran, M.; Langer, P. Synthesis 2009, 2430-2434. (c) Iqbal, I.; Langer, P. Synlett
2009, 1477-1479. (d) Iqbal, I.; Imran, M.; Villinger, A.; Langer, P. Synthesis 2009, 297-305.
7. Nawaz, M.; Sher, M.; Langer, P. Synlett 2010, 2383-2391 (Review).