Gas-phase thermolysis of condensed-1,2,4-triazines: interesting routes toward heterocyclic ring systems

Article abstract of DOI:10.1016/j.tet.2007.10.040

Gas-phase thermolysis of thieno[2,3-e][1,2,4]triazines gave benzonitrile, isothiazole, pyridazine, and thieno[2,3-d]thiazole derivatives. Similar transformation of benzo[1,2,4]triazine and phenanthro[9,10-e][1,2,4]triazine derivatives into their corresponding condensed thiazoles has been achieved by heating at 350 °C with sulfur. A mechanism for these pyrolytic transformations was proposed.

Full text of DOI:10.1016/j.tet.2007.10.040

Available online at www.sciencedirect.com
Tetrahedron 63 (2007) 12948–12953
Gas-phase thermolysis of condensed-1,2,4-triazines: interesting
routes toward heterocyclic ring systems
*
Hanan Al-Awadi, Maher R. Ibrahim, Nouria A. Al-Awadi and Yehia A. Ibrahim
Chemistry Department, Faculty of Science, Kuwait University, PO Box 5969, Safat 13060, Kuwait
Received 17 May 2007; revised 24 September 2007; accepted 11 October 2007
Available online 13 October 2007
Abstract—Gas-phase thermolysis of thieno[2,3-e][1,2,4]triazines gave benzonitrile, isothiazole, pyridazine, and thieno[2,3-d]thiazole deriv-
atives. Similar transformation of benzo[1,2,4]triazine and phenanthro[9,10-e][1,2,4]triazine derivatives into their corresponding condensed
thiazoles has been achieved by heating at 350 ꢀC with sulfur. A mechanism for these pyrolytic transformations was proposed.
Ó 2007 Published by Elsevier Ltd.
1. Introduction
In the present investigation we report our results on the py-
rolysis products of thieno[2,3-e][1,2,4]triazine 1 in order to
compare the pyrolytic behavior of this ring system with its
isomeric derivative A and the benzo analogs as well as their
synthetic potentialities.
Pyrolysis of N]N heterocyclic compounds has been shown
to start mainly by N2 loss leading to reactive diradical inter-
mediates which undergo subsequent transformation leading
to many interesting products. These pyrolytic reactions have
been reported for five-membered heterocyclic rings includ-
ing pyrazoles,1 thiadiazoles,2 triazoles,3 and tetrazoles4
and also six-membered heterocyclic rings including benzo-
triazoles,5 naphtho[1,8-de][1,2,3]triazines,6 cinnolines,7 1,2,3-
benzotriazines,8 and 1,2,4-benzotriazines.9
2. Results and discussion
Reaction products from complete gas-phase pyrolysis of
thieno[2,3-e][1,2,4]triazine 1 (Scheme 2) were obtained
at optimal reactor conditions of temperature, pressure
(0.06 mbar), and substrate residence time compatible with
>98%reactionestablishedforcompletedpyrolysisasevident
from HPLC analysis. The products of pyrolysis of 1 were sep-
arated by preparative HPLC and by column chromatography.
These products were characterized using GC–MS, LCMS,
1H, 13C NMR, and 2D NMR spectroscopy. Thus, compound
1 upon pyrolysis gave benzonitrile 2, 5-phenyl-3-cyanoiso-
thiazole 3, 5,6-diphenylpyridazine-3-carbonitrile 4, 3,4-
diphenylpyridazine5, and 2,5-diphenylthieno[2,3-d]thiazole 6.
The primary step in the pyrolysis of cinnolines,7 1,2,3-
benzotriazines,8 1,2,4-benzotriazines,9 benzotriazoles,5 and
naphtho[1,8-de][1,2,3]triazines6 involves mainly N2 elimi-
nation, yielding the corresponding diradical intermediates
which subsequently combine intramolecularly into the
corresponding condensed cyclobutenes or benzazetes, or
undergo further rearrangement or fragmentation before
yielding the final products.
Recently,10 we have shown that pyrolysis of thieno[3,2-e]-
[1,2,4]triazines A takes, in addition to nitrogen extrusion
(–N2), a different main fragmentation route by cleavage of
the N–N bond leading to reactive diradical intermediates B
and C (Scheme 1), which explains the formation of the py-
rolytic reaction products resulting from this ring system.10
N
N
S
N
1
Δ (500 °C, 0.06 mbar)
CN
CN
CN
N•
S
N
S
N
N•
S
S
N
C•
N
-N2
N-N bond cleavage
N
+
Ph
+
+
N
N
+
Ph
N
C
•
Ph
Ph
N
Ar'
S
N
Ar'
S
N
Ar'
Ar
Ph
Ph
Ar
Ar
Ph
4 (5%)
B
A
C
2 (4%)
3 (3%)
5 (8%)
6 (43%)
Scheme 1.
cyclohexene
500 °C, 0.06 mbar
100%
Keywords: Pyrolysis; Triazines; Thiazoles; Imidazoles; Heterocycles.
* Corresponding author. Tel.: +965 4985546; fax: +965 4836127; e-mail:
yehiaai@kuc01.kuniv.edu.kw
Scheme 2.
0040–4020/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.tet.2007.10.040

H. Al-Awadi et al. / Tetrahedron 63 (2007) 12948–12953
12949
1
S
8
9
6
decomposition products to give compound 6. The second
route which explains the formation of the pyridazines starts
by initial C3–N4 bond cleavage to give the diradical 10
which rearranges to the cyano diradical 11. The latter com-
bines to give the intermediate 12 which aromatizes via loss
of S to give 4. The latter via thermal loss of CN and replace-
ment with H radical gives the corresponding 3,4-diphenyl-
pyridazine 5. This was substantiated by the fact that
pyrolysis of 4 in the presence of cyclohexene (as a hydrogen
source) at 500 ꢀC gave 5.
6a
3a
5
2
10
14
7
11
N
S
4
3
13 12
112.9
7.49
134.3
132.7
169.2
145.1
128.9
128.0
125.7
126.3
H
128.8
S
H
H
7.36
130.1
N
S
H
H
H
H
133.8
7.51
7.47
156.5
7.45
7.67
8.02
The third route starts by N–N cleavage to give the diradical
13 which fragments further to givebenzonitrile2 and the dira-
dical 14. The latter rearranges to the cyano diradical 15.
The latter cyclizes intramolecularly via diradicals bonding
to give 3.
Figure 1. 1H and 13C NMR spectroscopy assignment of 6. The HMBC cor-
relation showed the following proton carbon cross peaks: H6 at d 7.49 cor-
relates with C3a (at d 156.5) and C5 (at d 145.1), H13 at d 7.47 correlates with
C
11 (at d 133.8), H12 at d 7.67 correlates with C5 (at d 145.1), H8 at d 8.02
correlates with C2 (at d 169.2), and H9 at d 7.47 correlates with C7 (at
d 134.3).
Alternatively, the formation of compound 6 has been pro-
posed to take place by cycloaddition of sulfur (generated
from decomposition of some of the starting compound or
through conversion of the proposed intermediate 12 to 4)
to the starting triazine 1 followed by nitrogen extrusion
(Scheme 4). This presumption has been verified by reacting
compound 1 with sulfur (in different molar ratio) at different
temperature (extending from 500 ꢀC to 250 ꢀC) in a static
pyrolyzer. The optimum condition was found to be the use
of 1.5 equiv of sulfur and heating at 350 ꢀC. Higher temper-
atures or a higher sulfur ratio gave large amounts of decom-
position products whereas lower temperatures gave very low
Assignments of the heterocyclic ring protons and carbons of
compound 6 along with the numbering used in the NMR cor-
relations are shown in Figure 1. These assignments were
made based on H,H-COSY, HMQC, and HMBC experi-
ments.
Scheme 3 illustrates possible mechanistic routes explaining
the formation of 2–6 obtained in the present pyrolytic studies
of compound 1. The first route starts by extrusion of N2 to
give the diradical 9 which then captures sulfur from the
N
N
Ph
S
N
Ph
1
N-N bond cleavage
-N2
N•
N•
N•
N•
Ph
-PhCN
S
C•
Ph
Ph
C•
S
N
Ph
S
N
Ph
9
13
14
N
N
C•
Ph
10
N•
S
-PhCN
S
N• Ph
Ph
15
S•
S
N
Ph
Ph
N
N
S
N
C•
Ph
Ph
CN
6
S•
Ph
Ph
N
S
N
11
S
3
N
N
N
N
N
N
N
N
-S
-CN.
+H.
Ph
Ph
Ph
Ph
Ph
12
4
5
Scheme 3.
N
S
N
N
N
-N2
N
350 °C, 0.06 mbar
15 min
Ar
S
+
Ph
S
Ar
Ar
S
S
N
Ph
1 Ar = C6H5
16 Ar = p-CH3C6H4
S
N
Ph
6 Ar = C6H5 (31%)
17 Ar = p-CH3C6H4 (28%)
Scheme 4.

12950
H. Al-Awadi et al. / Tetrahedron 63 (2007) 12948–12953
Table 1. Pyrolysis conditions and reaction products
N
N
S
N
N
Ph
350 °C, 0.06 mbar
15 min
S
S
+
+
Entry
Starting
triazine
Pyrolysis
conditions
Products/yield (%)
N
Ph
Ar
18
19 (26%)
1
2
3
4
5
6
7
8
1
4
1
A
B
C
C
C
C
C
C
A
A
A
D
D
D
B
B
B
2/4, 3/3, 4/5, 5/8, 6/43
5/80
6/31a
N
N
S
N
17/28b
Ar
16
18
20
21
22
20
21
22
20
21
22
20
21
22
350 °C, 0.06 mbar
15 min
19/26c
23/68d
24/30e
20, Ar = C6H5
23, Ar = C6H5 (68%)
24, Ar = p-ClC6H4 (30%)
25, Ar = p-CH3C6H4 (35%)
25/35f
21, Ar = p-ClC6H4
9
2/38, 28/11, 29/5
26/35, 28/8, 29/3
27/36, 28/12, 29/4
2/53, 28/19, 29/6
26/43, 28/15, 29/7
27/63, 28/18, 29/9
30/58
22, Ar = p-CH3C6H4
10
11
12
13
14
15
16
17
CN
500 °C, 0.06 mbar
NC
+
+
CN
FVP/700 °C
cyclohexene
500 °C, 0.06 mbar
X
31/15
32/38
2, X = H
26, X = p-Cl
27, X = p-CH3
28
29
For conditions A, B, C, D see Section 4.
Recovered starting 1 (30%).
H
N
a
Ar
N
b
Recovered starting 16 (35%).
Recovered starting 18 (25%).
Recovered starting 20 (15%).
Recovered starting 21 (40%).
Recovered starting 22 (46%).
c
d
e
f
30, Ar = C6H5 (58%)
31, Ar = p-ClC6H4 (15%)
32, Ar = p-CH3C6H4 (38%)
3. Conclusions
Scheme 5.
The present study offers interesting new routes toward het-
erocyclic compounds, some of which are new derivatives.
The present study also shows that thienotriazines behave dif-
ferently from the corresponding benzo analogs in the sense
that the pyrolytic liberated sulfur could undergo cycloaddi-
tion reaction to the 1,2,4-triazine ring systems, which
opened a new synthetic route to condensed thiazoles. More-
over, this study also showed the effect of the more electron
rich five-membered condensed thiophene ring on the pyro-
lytic behavior involving mechanistic pathways which are
different from their corresponding benzo analogs.
yields. This led to the exclusive formation of compound 6 to-
gether with the recovered 1. The fact that compound 1 did
not undergo pyrolysis alone below 500 ꢀC, but, in the pres-
ence of sulfur, compound 6 was formed at 350 ꢀC, indicates
that compound 6 was formed mainly, through cycloaddition
of sulfur to the starting triazine 1 followed by nitrogen extru-
sion (Scheme 4) and most probably not as postulated in
Scheme 3.
This cycloaddition of sulfur to the 1,2,4-triazine ring was
further investigated by reacting 3-phenylbenzo-1,2,4-tri-
azine 18 with sulfur under the previous conditions whereby
2-phenylbenzothiazole 19 was obtained along with benzo-
nitrile (the normal pyrolysis product obtained in absence of
sulfur in the FVP)9 (Scheme 5). Moreover, extension of
this cycloaddition of sulfur to 3-arylphenanthro[9,10-e]-
[1,2,4]triazines 20–22 led to the formation of the corre-
sponding 2-arylnaphtho[9,10-d]thiazoles 23–25. Pyrolysis
of 20–22 in absence of sulfur occurred at 700 ꢀC by FVP
and at 500 ꢀC under static conditions to give the corre-
sponding benzonitrile derivatives 2, 26, 27, biphenyl-2,20-
dicarbonitrile 28, and phenanthrene 29. The formation of
the latter could have been resulted from the addition of
two hydrogen atoms to the expected intermediate 9,10-phe-
nanthryne. The dimmer of the latter (tetrabenzobiphenyl-
ene) was only detected by its mass spectrum (MS:
m/z¼352) in the pyrolysis products (this compound is not
stable enough for purification and identification as
reported).11 On the other hand, static pyrolysis of 20–22
in the presence of cyclohexene (in an attempt to force a pos-
sible cycloaddition reaction) occurred only at 500 ꢀC and
led to the exclusive formation of the corresponding
2-aryl-1H-phenanthro[9,10-d]imidazoles 30–32, respectively
(Table 1).
4. Experimental
4.1. General
All melting points are uncorrected. IR spectra were recorded
in KBr disks on a Perkin Elmer System 2000 FT-IR spectro-
1
photometer. H and 13C NMR spectra were recorded on
a Bruker DPX 400, 400 MHz, AvanceII 600, 600 MHz
super-conducting NMR spectrometers. Mass spectra were
measured on VG Auto-spec-Q (high resolution, high perfor-
mance, tri-sector GC/MS/MS) and with LCMS using Agi-
lent 1100 series LC/MSD with an API-ES/APCI ionization
mode. Microanalyses were performed on LECO CH NS-932
Elemental Analyzer. Separation of reaction products was
performed using preparative HPLC WATER PREP 4000
series with PDA detector WATER 2996. The starting tri-
azines 1,12 16,12 18,13 and 2014 were prepared as reported.
4.2. 3-Arylphenanthro[9,10-e][1,2,4]triazines 20–23.
General procedure
To a mixture of the appropriate N-aminobenzamidine hydro-
chloride derivatives15 (12 mmol) in methanol (15 mL) was

H. Al-Awadi et al. / Tetrahedron 63 (2007) 12948–12953
12951
added with stirring at room temperature a suspension of phe-
nanthraquinone (2.1 g, 10 mmol) in methanol (10 mL), the
reaction mixture was allowed to stir at room temperature
overnight. The precipitate was then collected, washed with
ethanol, and recrystallized from the proper solvent.
Pyrex), cooled in liquid nitrogen, sealed, and pyrolyzed as
described for compound 1 for 15 min at 500 ꢀC. The product
showed by HPLC, H NMR, LCMS the formation of com-
pounds 5 and 30–32, respectively.
1
Condition C: pyrolysis of 1,2,4-trizines in the presence of
sulfur. Each of the triazines 1, 16, 18, 20–22 (0.25 g), and
sulfur (1.5 mol equiv) was introduced in the reaction tube
(1.5ꢁ12 cm Pyrex), cooled in liquid nitrogen, sealed under
vacuum (0.06 mbar), and placed in the pyrolyzer for
15 min at 350 ꢀC, a temperature that is required for obtain-
ing the optimum yield of the corresponding thiazole deriva-
tives. After cooling the reaction tube, the product was
extracted with CDCl3 and analyzed by 1H NMR and
GC–MS and LCMS. The pure products were separated on
4.2.1. 3-Phenylphenanthro[9,10-e][1,2,4]triazine (20).
Yellow needles from ethanol, yield 50%, mp 185–186 ꢀC
(lit.14 mp 187 ꢀC). LCMS: m/z¼308 (M+1). 1H NMR
(CDCl3) d 9.53 (d, 1H, J¼7.6 Hz), 9.46 (d, 1H, J¼7.6 Hz),
8.89 (dd, 2H, J¼7.6, 1.6 Hz), 8.66 (dd, 2H, J¼7.6,
1.6 Hz), 7.92 (t, 1H, J¼7.7 Hz), 7.86 (m, 2H), 7.66–7.47
(m, 4H).
4.2.2. 3-p-Chlorophenylphenanthro[9,10-e][1,2,4]tri-
azine (21). Yellow needles from DMF, yield 64%, mp
235–237 ꢀC. LCMS: m/z¼342 (M+1), 343 (M+2). MS:
m/z¼341 (M+, 15%), 312 (60%), 176 (100%). IR: 3292,
3070, 2850, 1603, 1503, 1399, 1366, 1298, 1066, 1094,
1012, 820, 760. 1H NMR (CDCl3) d 9.53 (d, 1H,
J¼7.6 Hz), 9.45 (d, 1H, J¼8.0 Hz), 8.84 (d, 2H,
J¼8.4 Hz), 8.66 (t, 2H, J¼6.9 Hz), 7.96 (t, 1H, J¼7.6 Hz),
7.93–7.82 (m, 3H), 7.63 (d, 2H, J¼8.4 Hz). 13C NMR
(DMSO-d6) d 160.7 (C), 145.7 (C), 143.6 (C), 137.7 (C),
135.2 (C), 134.7 (C), 134.1 (CH), 132.3 (CH), 131.9 (C),
130.8 (2CH), 130.4 (2CH), 130.1 (CH), 129.7 (CH), 128.3
(C), 128.0 (C), 127.3 (CH), 125.1 (CH), 125.0 (2CH).
Anal. Calcd for C21H12ClN3 (341.8): C 73.80; H 3.54; N
12.29. Found: C 73.88; H 3.68; N 12.27.
column chromatography using Merck Al-silica gel 60F254
with EtOAc/pet. ether (40–60) (1–15% of EtOAc).
,
Condition D: flash vacuum pyrolysis. The apparatus used
was similar to the one which has been described in our recent
publications.5,6,7a The sample was volatilized from a tube in
a Buchi Kugelrohr oven through a 30ꢁ2.5 cm horizontal
fused quartz tube. This was heated externally by a Carbolite
Eurotherm tube furnace MTF-12/38A to a temperature of
700 ꢀC, the temperature being monitored by Pt/Pt-13%Rh
thermocouple situated at the center of the furnace. The prod-
ucts were collected in a U-shaped trap and cooled in liquid
nitrogen. The whole system was maintained at a pressure
of 10ꢂ2 Torr by an Edwards Model E2M5 high capacity ro-
tary oil pump, the pressure being measured by a Pirani gage
situated between the cold trap and pump. Under these condi-
tions the contact time in the hot zone was estimated to be
10 ms. The different zones of the product collected in the
4.2.3. 3-p-Tolylphenanthro[9,10-e][1,2,4]triazine (22).
Yellow needles from DMF, yield 56%, mp 187–189 ꢀC.
MS: m/z¼321 (M+, 15%), 293 (90%), 176 (100%). IR:
3067, 3014, 2858, 1607, 1504, 1488, 1404, 1366, 1299,
1
U-shaped trap were analyzed by H, 13C NMR, IR, and
1
1063, 1034, 817, 758. H NMR (CDCl3) d 9.52 (dd, 1H,
GC–MS. Relative and percent yields were determined
from NMR.
J¼7.6, 1.6 Hz), 9.45 (d, 1H, J¼7.6 Hz), 8.77 (d, 2H,
J¼8.2 Hz), 8.63 (m, 2H), 7.94 (t, 1H, J¼7.6 Hz), 7.91–
7.79 (m, 3H), 7.46 (d, 2H, J¼8.2 Hz), 2.53 (s, 3H, CH3).
13C NMR (DMSO-d6) d 166.4, 150.1, 148.2, 147.6, 139.2,
138.7, 138.2, 136.8, 136.4, 135.6, 134.7, 134.4, 133.8,
133.2, 132.8, 132.0, 131.8, 129.6, 128.8, 27.0. Anal. Calcd
for C22H15N3 (321.4): C 82.22; H 4.70; N 13.07. Found: C
82.10; H 4.67; N 13.04.
4.4. Pyrolysis products
1
4.4.1. Benzonitrile (2). LCMS: m/z¼104 (M+1). H NMR
spectroscopic data identical to that reported in the litera-
ture.16
4.4.2. 3-Cyano-5-phenylisothiazole (3). White needles
from pet. ether (40–60) (TLC, Rf¼0.74, EtOAc/pet. ether
40–60 1:19), mp 90–92 ꢀC. MS: m/z¼186. IR: 3080,
2236, 1595, 1478, 1447, 1380, 1308, 1283, 1075, 977,
4.3. Pyrolysis reaction conditions: general procedures
Condition A: compound 1 (0.2 g) was introduced in the re-
action tube (1.5ꢁ12 cm Pyrex), cooled in liquid nitrogen,
sealed under vacuum (0.06 mbar), and placed in the pyro-
lyzer for 15 min at 500 ꢀC, a temperature that is required
for complete pyrolysis of the substrate as indicated by a pre-
liminary HPLC study. The pyrolyzate was then separated by
preparative HPLC using an ABZ+column with a solvent
mixture of acetonitrile and water (50:50) and the collected
1
852, 827, 760, 696. H NMR (CDCl3) d 8.03 (s, 1H), 7.88
(d, 2H, J¼7.5 Hz), 7.74 (t, 1H, J¼7.5 Hz), 7.54 (d, 2H,
J¼7.6 Hz). Anal. Calcd for C10H6N2S (186.2): C 64.49; H
3.25; N 15.04; S 17.22. Found: C 64.78; H 3.20; N 14.88;
S 17.16.
4.4.3. 3-Cyano-5,6-diphenylpyridazine (4). Colorless nee-
dles from ethanol (TLC, Rf¼0.48, EtOAc/pet. ether 40–60
1:19), mp 138–142 ꢀC. MS: m/z¼257 (M+, 100%). IR:
2949, 2922, 2220, 1729, 1565, 1528, 1459, 1375, 1347,
1260, 1074, 1027, 876, 802, 750. 1H NMR (CDCl3) d 8.62
(dd, 2H, J¼7.4, 1.5 Hz), 8.26 (dd, 2H, J¼7.4, 1.5 Hz),
7.93 (s, 1H), 7.64–7.54 (m, 6H). 13C NMR (CDCl3)
d 116.8 (CN), 118.0 (CH), 128.0 (2CH), 129.3 (2CH),
129.4 (2CH), 129.9 (2CH), 132.5 (CH), 132.9 (CH), 135.7
(C), 136.7 (C), 142.9 (C), 148.8 (C), 166.5 (C). Anal. Calcd
1
fractions were evaporated and subjected to H NMR and
GC–MS and LCMS studies. Also, the products were sepa-
rated on column chromatography using Merck Al-silica
gel 60 F254, with EtOAc/pet. ether (40–60) (1–15% of
EtOAc) to give successively 6 followed by 3, 5, and 4.
Condition B: pyrolysis of 4 and 20–22 with cyclohexene. A
mixture of each of 4 and 20–22 (1.0 mmol) and cyclohexene
(2 mmol) was introduced in the reaction tube (1.5ꢁ12 cm

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H. Al-Awadi et al. / Tetrahedron 63 (2007) 12948–12953
for C17H11N3 (257.3): C 79.36; H 4.31; N 16.33. Found: C
79.25; H 4.16; N 16.20.
Calcd for C21H13NS (311.4): C 81.00; H 4.21; N 4.50; S
10.30. Found: C 80.88; H 4.21; N 4.58; S 10.11.
4.4.4. 3,4-Diphenylpyridazine (5). Colorless needles from
ethanol (TLC, Rf¼0.65, EtOAc/pet. ether 40–60 1:19), mp
105–106 ꢀC (lit.17 mp 106–107 ꢀC). MS: m/z¼232 (M+,
100%). IR: 3031, 1549, 1421, 1378, 1347, 1165, 1069,
1023, 837, 745, 687. 1H NMR (CDCl3) d 8.87 (d, 1H,
J¼5.2 Hz), 8.63 (dd, 2H, J¼7.8, 1.2 Hz), 8.26 (dd, 2H,
J¼7.8, 1.2 Hz), 7.61 (d, 1H, J¼5.2 Hz), 7.55 (m, 6H). 13C
NMR (CDCl3) d 115.1 (CH), 127.8 (2CH), 128.9 (2CH),
129.1 (2CH), 129.5 (2CH), 131.3 (CH), 131.6 (CH), 137.5
(C), 138.4 (C), 158.5 (CH), 164.5 (C), 165.2 (C). Anal.
Calcd for C16H12N2 (232.3): C 82.73; H 5.21; N 12.06.
Found: C 82.65; H 5.16; N 12.00.
4.4.9. 2-p-Chlorophenylphenanthro[9,10-d]thiazole (24).
Yellow plates from ethanol, mp 218–220 ꢀC. Rf¼0.60
(EtOAc/pet. ether 60–80 1:8). LCMS: m/z¼346 (M+1),
347 (M+2). IR: 3435, 3232, 3043, 2907, 1632, 1592, 1461,
1
1393, 1161, 973, 821, 750. H NMR (CDCl3) d 8.97 (dd,
1H, J¼7.6, 1.6 Hz), 8.76 (dd, 2H, J¼7.8, 1.6 Hz), 8.19 (d,
2H, J¼8.4 Hz), 8.07 (dd, 1H, J¼7.6, 1.6 Hz), 7.78–7.66
(m, 4H), 7.53 (d, 2H, J¼8.4 Hz). 13C NMR (CDCl3)
d 166.6 (C), 145.4 (C), 138.2 (C), 134.7 (C), 134.4 (C),
133.0 (CH), 131.6 (C), 131.3 (CH), 130.2 (2CH), 129.7
(2CH), 129.2 (CH), 128.6 (CH), 128.4 (C), 128.2 (C),
128.0 (C), 127.0 (CH), 125.4 (CH), 123.6 (CH), 123.5
(CH). Anal. Calcd for C21H12NSCl (345.8): C 72.93; H
3.50; N 4.05; S 9.27. Found: C 72.88; H 3.41; N 4.00; S 9.21.
4.4.5. 2,5-Diphenylthieno[2,3-d]thiazole (6). Yellow plates
from acetonitrile (TLC, Rf¼0.80, EtOAc/pet. ether 40–60
1:19), mp 235–236 ꢀC. MS: m/z¼293 (M+, 100%). IR:
3053, 2922, 1628, 1595, 1507, 1454, 1301, 1220, 998,
4.4.10. 2-p-Tolylphenanthro[9,10-d]thiazole (25). Yellow
plates from ethanol, mp 210–212 ꢀC. Rf¼0.68 (EtOAc/pet.
ether 60–80 1:9). LCMS: m/z¼326 (M+1). MS: m/z¼325
(M+, 70%), 307 (80%), 293 (30%). IR: 3224, 3045, 2920,
2882, 1723, 1601, 1493, 1467, 1378, 1257, 1113, 1060,
906, 807, 749. 1H NMR (CDCl3) d 8.99 (d, 1H,
J¼7.5 Hz), 8.74 (m, 2H), 8.14 (d, 2H, J¼8.4 Hz), 8.07 (m,
1H), 7.76 (m, 2H), 7.69 (m, 2H), 7.36 (d, 2H, J¼8.4 Hz),
2.45 (s, 3H). 13C NMR (CDCl3) d 161.6 (C), 145.4 (C),
143.4 (C), 142.8 (C), 134.5 (C), 133.9 (C, CH), 133.5 (C),
132.1 (2CH), 131.7 (CH), 130.9 (CH), 130.0 (2CH), 129.6
(C), 129.0 (C), 128.5 (CH), 128.1 (CH), 127.2 (CH), 124.9
(2CH), 22.2 (CH3). Anal. Calcd for C22H15NS (325.4): C
81.20; H 4.65; N 4.30; S 9.85. Found: C 81.08; H 4.48; N
4.30; S 9.81.
1
813, 750, 684. H NMR (CDCl3) d 8.02 (dd, 2H, J¼7.8,
1.4 Hz), 7.67 (d, 2H, J¼7.6 Hz), 7.52 (m, 1H), 7.49 (s,
1H), 7.47 (m, 2H), 7.45 (t, 2H, J¼7.7 Hz), 7.36 (t, 1H,
J¼7.4 Hz). 13C NMR (CDCl3) d 112.9 (CH), 125.7 (2CH),
126.3 (2CH), 128.0 (CH), 128.8 (2CH), 128.9 (2CH),
130.1 (CH), 132.7 (C), 133.8 (C), 134.3 (C), 145.1 (C),
156.5 (C), 169.2 (C). Anal. Calcd for C17H11N2S (293.4):
C 69.59; H 3.78; N 4.77; S 21.86. Found: C 69.45; H 3.36;
N 4.56; S 22.00.
4.4.6. 2-Phenyl-6-p-tolylthieno[3,2-d]thiazole (17). Yellow
plates from ethanol, mp 280–282 ꢀC. LCMS: m/z¼308
(M+1). MS: m/z¼307 (M+, 100%), 154 (10%), 115 (10%).
IR: 3056, 3024, 2954, 2918, 2850, 1633, 1523, 1456, 1303,
1220, 1120, 999, 912, 877, 804, 756, 686. 1H NMR
(CDCl3) d 8.02 (dd, 2H, J¼8.0, 1.6 Hz), 8.57 (d, 2H,
J¼7.8 Hz), 7.52–7.46 (m, 3H), 7.44 (s, 1H), 7.25 (d, 2H,
J¼7.8 Hz), 2.42 (s, 3H). 13C NMR (CDCl3) d 148.8 (C),
145.4 (C), 139.4 (C), 138.2 (C), 134.0 (C), 132.7 (C), 131.7
(C), 130.1 (CH), 129.8 (2CH), 129.0 (2CH), 126.4 (2CH),
125.7 (2CH), 112.6 (CH), 21.2 (CH3). Anal. Calcd for
C18H13N3S2 (307.1): C 70.32; H 4.26; N 4.56; S 20.86.
Found: C 70.28; H 4.41; N 4.38; S 20.71.
4.4.11. p-Chlorobenzonitrile (26). LCMS: m/z¼137
1
(M+1). H NMR (CDCl3) d 7.49 (d, 2H, J¼8.4 Hz), 7.63
(d, 2H, J¼8.4 Hz).19
4.4.12. p-Tolylbenzonitrile (27). MS: m/z¼117 (M+,
1
100%). H NMR (CDCl3) d 7.29 (d, 2H, J¼8.0 Hz), 7.56
(d, 2H, J¼8.0 Hz).20
4.4.13. Biphenyl-2,20-dicarbonitrile (28). Colorless nee-
dles from ethanol, mp 170–172 ꢀC (lit.21 mp 173–174 ꢀC).
LCMS: m/z¼205 (M+1). MS: m/z¼204 (M+, 100%). IR:
3061, 2969, 2916, 2229, 1663, 1566, 1489, 1449, 1394,
4.4.7. 2-Phenylbenzothiazole (19). Yellow plates from eth-
anol, mp 113–114 ꢀC (lit.18 mp 112–113 ꢀC). LCMS:
1
1
m/z¼212 (M+1). H NMR (CDCl3) d 8.13 (m, 2H), 8.09
1334, 1230, 1115, 1056, 889, 760, 695. H NMR (CDCl3)
d 7.85 (m, 2H), 7.77 (dt, 2H, J¼7.8, 1.4 Hz), 7.62–7.52
(d, 1H, J¼8.0 Hz), 7.93 (d, 1H, J¼8.0 Hz), 7.52 (m, 4H),
7.41 (t, 1H, J¼7.4 Hz).
(m, 4H).
4.4.8. 2-Phenylphenanthro[9,10-d]thiazole (23). Yellow
plates from pet. ether 60–80, mp 150–152 ꢀC. Rf¼0.46
(EtOAc/pet. ether 60–80 1:9). LCMS: m/z¼312 (M+1).
MS: m/z¼311 (100%), 208 (30%), 156 (15%). IR: 3322,
3236, 3081, 2945, 1723, 1653, 1562, 1418, 1317, 1199,
4.4.14. Phenanthrene (29). Colorless needles from pet.
ether (40–60), mp 98–100 ꢀC (lit.22 mp 100 ꢀC). MS:
1
m/z¼178 (M+, 100%). H NMR (CDCl3) d 8.72 (d, 2H,
J¼8.2 Hz), 7.92 (dd, 2H, J¼7.8, 1.5 Hz), 7.77 (s, 2H),
7.69 (t, 2H, J¼7.8 Hz), 7.61 (t, 2H, J¼7.8 Hz). 13C NMR
(CDCl3) d 122.6 (CH), 126.6 (CH), 126.9 (CH), 128.6
(CH), 129.2 (CH), 130.3 (C), 132.0 (C).
1
972, 941, 741. H NMR (CDCl3) d 8.99 (dd, 1H, J¼7.6,
1.4 Hz), 8.75 (dd, 1H, J¼7.8, 1.6 Hz), 8.72 (d, 1H,
J¼8.2 Hz), 8.25(d, 2H, J¼7.6 Hz), 8.08 (dd, 1H, J¼8.2,
1.6 Hz), 7.77 (m, 2H), 7.69 (m, 2H), 7.57–7.52 (m, 3H).
13C NMR (CDCl3) d 166.6 (C), 149.7 (C), 133.9 (2C),
130.8 (C), 130.6 (CH), 129.9 (2C), 129.1 (2CH), 128.3
(C), 127.4 (2CH), 127.2 (2CH), 126.9 (CH), 126.7 (CH),
126.1 (CH), 124.9 (CH), 123.8 (CH), 123.1 (CH). Anal.
4.4.15. 2-Phenyl-1H-phenanthro[9,10-d]imidazole (30).
Yellow needles from acetonitrile, mp 322–324 ꢀC (lit.14
mp 325 ꢀC). LCMS: m/z¼295 (M+1). IR (KBr): 3432,
1
3119, 1611, 1455, 1440, 751, 735. H NMR (DMSO-d6)
d 13.53 (br s, 1H, NH), 8.87 (m, 2H), 8.58 (dd, 2H, J¼8.2,

H. Al-Awadi et al. / Tetrahedron 63 (2007) 12948–12953
12953
1219; (d) MacBride, J. A. H. J. Chem. Soc., Chem. Commun.
1974, 359; (e) Chambers, R. D.; Clark, D. T.; Holmes, T. F.;
Musgrave, W. R. K.; Ritchie, I. J. Chem. Soc., Perkin Trans.
1 1974, 114; (f) Barton, J. W.; Walker, R. B. Tetrahedron
Lett. 1975, 569; (g) Barton, J. W.; Walker, R. B. Tetrahedron
Lett. 1978, 1005; (h) Kanoktanoporn, S.; MacBride, J. A. H.
Tetrahedron Lett. 1977, 1817; (i) Kilcoyne, J. P.; MacBride,
J. A. H.; Muir, M.; Write, P. M. J. Chem. Res., Synop. 1990,
6; Kilcoyne, J. P.; MacBride, J. A. H.; Muir, M.; Write, P. M.
J. Chem. Res., Miniprint 1990, 215; (j) Adams, D. B.;
Kilcoyne, J. P.; MacBride, J. A. H.; Muir, M. J. Chem. Res.,
Synop. 1990, 172; Adams, D. B.; Kilcoyne, J. P.; MacBride,
J. A. H.; Muir, M. J. Chem. Res., Miniprint 1990, 1301; (k)
Shepherd, M. K. J. Chem. Soc., Perkin Trans. 1 1994, 1055;
(l) Wilcox, C. F., Jr.; Lassila, K. R.; Kang, S. J. Org. Chem.
1988, 53, 4333; (m) Coates, W. G. Pyridazines and Their
Condensed Derivatives; Katritzky, A. R., Rees, C. W.,
Scriven, F. V., Eds.; Comprehensive Heterocyclic Chemistry
II; Pergamon: London, 1996; Vol. 6, p 87.
1.5 Hz), 8.32 (d, 2H, J¼7.4 Hz), 7.73 (m, 2H), 7.67–7.59 (m,
4H), 7.50 (t, 1H, J¼7.4). Anal. Calcd for C21H14N2 (294.4):
C 85.69; H 5.23; N 9.08. Found: C 85.58; H 5.18; N 9.00.
4.4.16. 2-p-Chlorophenyl-1H-phenanthro[9,10-d]imid-
azole (31). LCMS: m/z¼328 (M+1), 329 (M+2).
4.4.17. 2-p-Tolyl-1H-phenanthro[9,10-d]imidazole (32).
Yellow needles from DMF, mp 328–330 ꢀC. LCMS:
m/z¼309 (M+1). IR: 3326, 3148, 3060, 2956, 1705, 1614,
1483, 1457, 1359, 1280, 1127, 755, 725. 1H NMR
(DMSO-d6) d 13.39 (br s, 1H, NH), 8.86 (m, 2H), 8.56
(dd, 2H, J¼8.0, 1.6 Hz), 8.21 (d, 2H, J¼8.0 Hz), 7.76–7.61
(m, 4H), 7.43 (d, 2H, J¼8.0 Hz), 2.41 (s, 3H). 13C NMR
(CDCl3) d 161.1 (C), 142.8 (C), 142.2 (C), 133.9 (C),
133.3 (CH), 132.9 (CH), 131.5 (CH), 131.1 (C), 130.3
(2CH), 130.2 (C), 129.3 (CH), 129.0 (CH), 128.5 (C,
2CH), 127.9 (C), 127.5 (C), 126.6 (CH), 124.6 (CH), 124.3
(2CH), 21.6 (CH3). Anal. Calcd for C22H16N2 (308.4): C
85.69; H 5.23; N 9.08. Found: C 85.58; H 5.18; N 9.00.
8. (a) Adgar, B. M.; Keating, M.; Rees, C. W.; Storr, R. C.
J. Chem. Soc., Perkin Trans. 1 1975, 41; (b) Werstiuk, N. H.;
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9. (a) Adgar, B. M.; Rees, C. W.; Storr, R. C. J. Chem. Soc., Perkin
Trans. 1 1975, 45; (b) Riedl, Z.; Hajos, G.; Pelaez, W. J.;
Moyano, E. J.; Yranzo, G. I. Tetrahedron 2003, 59, 851.
10. Ibrahim, Y. A.; Al-Awadi, N. A.; Ibrahim, M. R. Tetrahedron
2004, 60, 9121.
Acknowledgements
The support of the University of Kuwait received through
research grant no. SC04/05 and the facilities of ANALAB
and SAF (grants no. GS01/01, GS01/03, GS03/01) are grate-
fully acknowledged.
11. Vogler, H.; Ege, G. J. Am. Chem. Soc. 1977, 99, 4599 and ref-
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12. Abdel-Hady, S. A.; Badawy, M. A.; Kadry, A. M.; Ibrahim,
Y. A. Sulfur Lett. 1988, 8, 153.
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