Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines. Interesting routes towards heterocyclic ring systems

Article abstract of DOI:10.1016/j.tet.2004.07.076

Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines gave benzonitrile, isothiazole, pyrimidine, [1]benzothieno[2,3-d]pyrimidine and thieno[3,2-d]thiazole derivatives. A mechanism of these pyrolytic transformation was proposed. Two new and efficient syntheses of the starting thieno[3,2-e][1,2,4]triazines were reported.

Full text of DOI:10.1016/j.tet.2004.07.076

Tetrahedron 60 (2004) 9121–9130
Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines.
Interesting routes towards heterocyclic ring systems
*
Yehia A. Ibrahim, Nouria A. Al-Awadi and Maher R. Ibrahim
Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait
Received 19 January 2004; revised 5 July 2004; accepted 28 July 2004
Available online 28 August 2004
Abstract—Gas-phase thermolysis of thieno[3,2-e][1,2,4]triazines gave benzonitrile, isothiazole, pyrimidine, [1]benzothieno[2,3-d]-
pyrimidine and thieno[3,2-d]thiazole derivatives. A mechanism of these pyrolytic transformation was proposed. Two new and efficient
syntheses of the starting thieno[3,2-e][1,2,4]triazines were reported.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
diradicals which undergo several rearrangements yield-
ing mainly polycondensed aromatic and heteroaromatic
compounds.1 Rees, Storr and co-workers have
thoroughly studied the flash vacuum pyrolysis of
1,2,4-benzotriazines B and 1,2,3-benzotriazines C, as
possible routes to benzazetes.3,4 With the exception of
4-aryl-1,2,3-benzotriazine C (RZPh, p-MeOC6H4)
which could be converted pyrolytically into 2-aryl-
benzazetes D, other 1,2,3-benzotriazine and 1,2,4-
benzotriazine derivatives initially lose N2 followed by
RCN (i.e. the heterocyclic ring) and gave biphenylene E
(Scheme 1).3
Flash vacuum pyrolysis (FVP) of cinnolines1,2 A, 1,2,4-
benzotriazines3 B and 1,2,3-benzotriazines3 C has been
studied and was shown to give a direct and easy access to
many interesting compounds some of which are otherwise
difficult to obtain. The primary step in the pyrolysis of these
compounds involves mainly N2 elimination, yielding the
corresponding diradical intermediates which subsequently
combines intramolecularly into the corresponding con-
densed cyclobutenes or benzazetes, or undergo further
rearrangement or fragmentation before yielding the final
products. Thus, flash vacuum pyrolysis of cinnoline
derivatives A has been shown to lead to initial loss of
nitrogen to give diradicals which then cyclize to give
biphenylene derivatives when X, Y are condensed benzo
derivatives. Recently, we have also found that FVP of
3-acylcinnolines (XZCH and YZCCOAr) initially gave
In the present investigation we studied the pyrolysis
products of thieno[3,2-e][1,2,4]triazines 1a–d in order to
study the pyrolytic behavior of this ring system in
comparison with their benzo analogs B as well as their
synthetic potentialities.
Scheme 1.
Keywords: FVP; Triazines; Heterocycles.
* Corresponding author. Tel.: C965-9464215; fax: C965-4836127; e-mail: yehiaai@kuc01.kuniv.edu.kw
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.07.076

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Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
Scheme 2.
patible with O98% reaction established for completed
pyrolysis as evident from HPLC analysis. The products of
pyrolysis of 1a were separated by preparative HPLC and by
column chromatography. These products were character-
1
ized using GCMS, LCMS, H, 13C NMR and 2D NMR
spectroscopy. Thus, compound 1a upon pyrolysis gave
benzonitrile 2a, 3-cyano-4-phenylisothiazole 3a, 2,5-
diphenylpyrimidine 4a, 3-cyano-2,5-diphenylpyrimidine
5a, 4-cyano-2-phenyl[1]benzothieno[2,3-d]pyrimidine 6a,
2-phenyl[1]benzothieno[2,3-d]pyrimidine 7a and 3,5-
diphenylthieno[3,2-d]thiazole 8a in the percentage yields
indicated in Table 1. On the other hand, compounds 2a, 3a,
5a and 6a could only be detected upon FVP of 1a at 800 8C
and 0.02 Torr.
2. Results and discussion
Reaction products from complete gas-phase pyrolysis of
thieno[3,2-e][1,2,4]triazines 1a–d (Scheme 2) were
obtained at optimal reactor conditions of temperature,
pressure (0.06 mbar) and substrate residence time com-
Similar pyrolysis (static and FVP) of 1b–d gave the
corresponding benzonitriles 2, 4-aryl-3-cyanothiazoles 3,
2,5-diarylpyrimidines 4, 2,5-diaryl-4-cyanopyrimidines 5,
1
Table 1. Pyrolysis products of 1a–d (% yieldsa from Static, FVP) and characteristic H NMR signalb of the heterocyclic ring
Substrate
Pyrolysis products (% yields)
2
3
4
5
6
7
8
1a
Static
FVP
2a
34
51
3a
19
18
8.80
3a
17
14
8.80
3c
17
12
8.75
3c
17
13
4a
4
0
9.05
4b
10
0
9.03
4c
6
5a
13
5
9.08
5b
10
10
9.05
5c
6a
12
3
7a
4
0
9.47
7b
5
8a
12
0
7.60
8b
10
0
1H NMR
1b
2b
25
49
6b
10
4
Static
FVP
0
1H NMR
1c
9.42
7c
4
2b
23
55
6c
9
4
8c
9
0
Static
FVP
6
4
0
0
1H NMR
1d
9.04
4d
6
0
9.00
9.06
5d
6
5
9.03
9.42
7d
4
0
9.43
2b
23
54
6d
9
2
8d
9
0
Static
FVP
1H NMR
8.75
a
Yields measured by HPLC and 1H NMR spectroscopy.
Measured in CDCl3, singlet (1H) for compounds 3a,c, 5a–d, 7a–d, 8a and singlet (2H) for compounds 4a–d.
b

Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
9123
Figure 1. 1H and 13C NMR spectroscopy assignments of 3a, 5a and 8a.
2-aryl-4-cyano[1]benzothieno[2,3-d]pyrimidines 6, 2-aryl-
[1]benzothieno[2,3-d]pyrimidines
thieno[3,2-d]thiazoles 8.
8.18 correlates with C4. Other correlations could not be
clearly assigned due to overlapping signals in the 1H
NMR spectra.
7 and 2,4-diaryl-
The pyrolysates were qualitatively and quantitatively
determined by HPLC (Table 1) and by 1H NMR. The
structure of these pyrolysis products was also established by
The structure of compound 7a was confirmed by preparing
an authentic sample following the reported procedure
described for the parent ring system and its 2-methyl
derivative.5 The details of this synthesis will be published
later.
1
LCMS, GCMS, H, 13C and 2D NMR.
Assignments of heterocyclic ring protons and carbons of
compounds 3a, 5a and 8a are shown in Figure 1. These
assignments were made based on H,H-COSY, HMQC and
HMBC experiments.
From Table 1 it is clear that FVP gave similar products to
those obtained from static pyrolysis except those (4, 7) in
which the cyano group has been lost (i.e. replaced by H) or a
sulfur atom is captured by the intermediates to produce the
corresponding thieno[3,2-d]thiazoles 8. This could be
explained by further fragmentation during the long
residence time during static pyrolysis (15 m at 530 8C)
compared to FVP (10 ms at 800 8C).
Figure 2 shows the numbering used in the following
NMR correlations. For compound 3a, the HMBC
correlation showed the following proton carbon cross
peaks: H5 at d 8.80 correlates with C3, C4, C7, H8 at d
7.65 correlates with C4, C10, H9 at d 7.54 correlates
with C7 and H10 at d 7.49 correlates with C8. For
compound 5a, the HMBC correlation showed the
following proton carbon cross peaks: H6 at d 9.08
correlates with C2, C4, C5, C7, C12, H9 at d 8.53
correlates with C2, C11 and H13 at d 7.66 correlates with
C5. Other correlations could not be clearly assigned due
to interference in the 1H NMR. For compound 8a, the
HMBC correlation showed the following proton carbon
cross peaks: H5 at d 7.60 correlates with C3a, C6a, C11,
H8 at d 8.08 correlates with carbons C2 and H12 at d
Scheme 3 illustrates possible mechanistic routes explain-
ing the formation of 2–8 obtained in the present
pyrolytic studies of compounds 1. The first route starts
by extrusion of N2 to give the diradicals 9 which then
capture sulfur from the decomposition products to give
compounds 8. The second route which explains the
formation of the rest of the reaction products takes
place by initial N–N bond cleavage to give the
diradicals 10 which rearrange to the cyano diradicals
11 which fragments further to give the nitriles 2 and the
Figure 2. 1H and 13C NMR signal assignments of 3a, 5a and 8a.

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Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
Scheme 3.
Scheme 4.

Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
9125
diradicals 12. The latter cyclize intramolecularly via
diradicals bonding to give 3.
spectrophotometer. 1H and 13C NMR spectra were recorded
on a Bruker DPX 400, 400 MHz super-conducting NMR
spectrometer. Mass spectra were measured on VG Auto-
spec-Q (high resolution, high performance, tri-sector
GC/MS/MS) and with LCMS using Agilent 1100 series
LC/MSD with an API-ES/APCI ionization mode. Micro-
analyses 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.
Alternatively the diradicals 11 via two intramolecular
radical cyclizations give the intermediates 14 followed by
loss of H2 to form 6. The formation of 7 might result either
from 6 via thermal loss of CN and replacement with H
radicals or from 14 via two successive 1,5-H-shift to give 15
followed by elimination of HCN.
The diradicals 11 also, combine to give the intermediate 13
which aromatizes via loss of S to give 5. The latter
presumably, via thermal loss of CN and replacement with H
radicals give the corresponding 2,5-diarylpyrimidines 4.
This presumption was substantiated by the fact that
pyrolysis of each of 5a,b in the presence of cyclohexene
(as a hydrogen source) at 530 8C gave the corresponding
2,5-diarylpyrimidines 4a,b respectively.
4.1. Pyrolysis of 1a–d: general procedures
(A) Static pyrolysis 1a–d. Each substrates (0.2 g) was
introduced in the reaction tube (1.5!12 cm Pyrex), cooled
in liquid nitrogen, sealed under vacuum (0.06 mbar) and put
in the pyrolyser for 15 min at 530 8C, a temperature that is
required for complete pyrolysis of the substrate as indicated
by preliminary HPLC study The pyrolysate was then
separated by preparative HPLC using ABZCcolumn with
a solvent mixture of acetonitrile and water (50:50 in case for
products of pyrolysis of 1a and 60:40 in case for products of
pyrolysis of 1b–d) and collected components were evapor-
ated and subjected to 1H NMR and GCMS and LCMS
studies. Also, the products were separated on column
chromatography using Merck Al-silica gel 60F254, with
EtOAC/petroleum ether (40–60) (1–15% of EtOAc) to give
successively 8 followed by 3, 5, 6, 4, 7.
The starting thienotriazines 1a–d were prepared as shown in
Scheme 4 starting from the corresponding oxazolone 16a–d
using our described method6 for the synthesis of 1a via the
Mannich bases 18a–d. Thus, the appropriate oxazolones
16a–d were converted into the corresponding 5-arylmethyl-
1,2,4-triazin-6(5H)-ones 17a–d upon treatment with hydra-
zine hydrate followed by aqueous NaOH. The latter were
then converted into their corresponding bis-Mannich basses
18a–d upon treatment with HCHO and morpholine in
methanol. Thiation of 18a–d with phosphorus pentasulfide
in pyridine gave the corresponding thieno[3,2-e][1,2,4]tia-
zines 1a–d in ca. 55% overall yields from 17a–d to 1a–d.6
In the present study also, two new more efficient methods
are described for the synthesis of 1a–d. Thus, heating 17a–d
at 100 8C with DMFDMA for 5 min gave ca. 80% of the
corresponding dimethylenamines 20a–d. Longer reaction
time led to further methylation with the formation of
1-methyl derivatives 19b. Heating 20a–d with phosphorus
pentasulfide in pyridine under reflux gave the corresponding
thieno[3,2-e][1,2,4]triazines 1a–d in ca. 85%. Alternatively,
thiation of 17a–d gave the corresponding 1,2,4-triazine-
6(1H)-thiones 21a–d. Heating the latter at 100 8C with
DMFDMA for 30 min gave ca. 90% of the corresponding
thienotriazines 1a–d.
(B) Flash vacuum pyrolysis of 1a–d. The apparatus used
was similar to the one which has been described in our
recent publications.1,7 The sample was volatilized from a
tube in a Bu¨chi Kugelrohr oven through a 30!2.5 cm
horizontal fused quartz tube. This was heated externally by a
Carbolite Eurotherm tube furnace MTF-12/38A to a
temperature of 800 8C, the temperature being monitored
by a Pt/Pt-13%Rh thermocouple situated at the center of the
furnace. The products were collected in a U-shaped trap
cooled in liquid nitrogen. The whole system was maintained
at a pressure of 10K2 Torr by an Edwards Model E2M5 high
capacity rotary oil pump, the pressure being measured by a
Pirani gauge situated between the cold trap and the pump.
Under these conditions the contact time in the hot zone was
estimated to be y10 ms. The different zones of the products
collected in the U-shaped trap were analyzed by H, 13C
1
NMR, IR and GC-MS. Relative and percent yields were
determined from 1H NMR. Identity of compounds obtained
3. Conclusions
1
were confirmed by comparison of their H, 13C NMR, IR
The present study offers interesting new routes towards
heterocyclic compounds some of which are new derivatives.
The present study also shows that the thienotriazines
behaves differently from the corresponding benzo analogs.
This can be explained as due to the effect of the more
electron rich five-membered condensed thiophene ring and
its further pyrolysis affected by the cleavage of the S–C
bond. Also, comparison between FVP and static pyrolysis
demonstrates the potential synthetic applications of these
pyrolytic techniques in organic synthesis.
with data of products separated from preparative HPLC and
column chromatography.
4.2. Pyrolysis products
4.2.1. Arylnitriles 2. Benzonitrile 2a. LCMS: m/zZ104
(MC1, 100%) 1H NMR spectroscopic data identical to that
reported in the literature.8
p-Tolunitrile 2b. LCMS: m/zZ118 (MC1, 100%). 1H
NMR spectroscopic data identical to that reported in the
literature.9
4. Experimental
All melting points are uncorrected IR spectra were recorded
in KBr disks using Perkin Elmer System 2000 FT-IR
4.2.2. 3-Cyano-4-arylisothiazoles 3. 3-Cyano-4-phenyl-
isothiazole 3a. Isolated yield 17% (colorless crystals from

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Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
EtOH); [TLC, RfZ0.65, EtOAc/petroleum ether (40–60),
5:95] mp 96–98 8C. MS: m/zZ186 (MC, 100%). IR (KBr):
3079, 2235, 1652, 1577, 1480, 1447, 1379, 1326, 1307,
4.2.4. 4-Cyano-2,5-diarylpyrimidines 5. 4-Cyano-2,5-
diphenylpyrimidine 5a. Isolated yield 8% (colorless crystals
from EtOH), [TLC, RfZ0.65, EtOAc/petroleum ether
(40–60), 3:97]; mp 142–143 8C. MS: m/zZ257 (MC,
100%); LCMS: m/zZ258 (MC1). IR (KBr): 3062, 3025,
1564, 1513, 1453, 1426, 1369, 1264, 1151, 1069, 1002, 918,
873, 817, 763, 692. 1H NMR (CDCl3): d 9.08 (s, 1H), 8.53
(dd, 2H, JZ1.5, 7.2 Hz), 7.66 (dd, 2H, JZ1.5, 8 Hz), 7.64–
7.53 (m, 6H). 13C NMR (CDCl3): d 164.2 (pyrimidine C-2),
159.1 (pyrimidine CH), 139.3 (C), 136.1 (C), 135.7 (C),
135.1 (C), 132.1 (CH), 130.3 (CH), 129.6 (2CH), 129.1
(2CH), 128.8 (2CH), 128.7 (2CH), 115.7 (CN). Anal. calcd
for C17H11N3 (257.3): C 79.36; H 4.31; N 16.33. Found C
79.06; H 4.42; N 16.25.
1
1173, 1076, 978, 862, 849, 827, 759, 744, 711, 696. H
NMR (CDCl3): d 8.80 (s, 1H), 7.65 (d, 2H, JZ7.2 Hz), 7.54
(t, 1H, JZ7.2 Hz), 7.49 (t, 2H, JZ7.2 Hz). 13C NMR
(CDCl3): d 147.0, 143.5, 138.4, 129.9, 129.4, 129.3, 128.0,
113.9. Anal. calcd for C10H6N2S (186.2): C 64.49; H 3.25;
N 15.04; S; 17.22. Found C 64.77; H 3.35; N 15.05; S;
17.50.
3-Cyano-4-p-tolylisothiazole 3c. Isolated yield 15% (color-
less crystals from MtOH); mp 128–130 8C. LCMS: m/zZ
201 (MC1). IR (KBr): 3095, 2235, 1531, 1484, 1457, 1427,
1377, 1326, 1307, 1163, 977, 796, 695. 1H NMR (CDCl3): d
8.75 (s, 1H), 7.55 (d, 2H, JZ7.8 Hz), 7.33 (d, dH, JZ
7.8 Hz), 2.48 (s, 3H). Anal. calcd for C11H8N2S (200.3): C
65.97; H 4.03; N 13.99; S 16.01. Found C 66.05; H 3.98; N
14.02; S 15.99.
4-Cyano-5-phenyl-2-p-tolylpyrimidine 5b. Isolated yield
8% (colorless crystals from EtOH), [TLC, RfZ0.38,
CHCl3/petroleum ether (40–60), 30:70]; mp 190–192 8C.
MS: m/zZ271 (MC, 100%); LCMS: m/zZ272 (MC1). 1H
NMR (CDCl3): d 9.05 (s, 1H), 8.42 (d, 2H, JZ8 Hz), 7.65
(dd, 2H, JZ2, 7.6 Hz), 7.60 (m, 3H), 7.36 (d, 2H, JZ8 Hz),
2.47 (s, 3H). 13C NMR (CDCl3): d 164.1 (pyrimidine C-2),
158.9 (pyrimidine CH), 142.4 (C), 139.1 (C), 134.7 (C),
132.9 (C), 132.0 (C), 130.0 (CH), 129.8 (2CH), 129.4
(2CH), 128.8 (2CH), 128.7 (2CH), 115.6 (CN), 21.6 (CH3).
Anal. calcd for C18H13N3 (271.3): C 79.68; H 4.83; N 15.49.
Found C 79.58; H 4.63; N 15.25.
4.2.3. 2,5-Diarylpyrimidines 4. 2,5-Diphenylpyrimidine
4a. Isolated yield 4% (colorless crystals from EtOH),
[TLC, RfZ0.50, EtOAc/petroleum ether (40–60), 5:95]; mp
180–182 8C (lit.10 mp 180–182 8C). MS: m/zZ232 (MC,
1
100%); LCMS: m/zZ233 (MC1). H NMR (CDCl3): d
9.05 (s, 2H, H-4,6), 8.51 (dd, 2H, JZ8, 2 Hz), 7.66 (d, 2H,
JZ7.6 Hz), 7.58–7.45 (m, 6H). 13C NMR (CDCl3): d 163.4
(C-2), 155.2 (2CH-4,6), 137.2 (C-5), 134.5 (C), 131.7 (C),
130.8 (CH), 139.4 (2CH), 128.8 (CH), 128.5 (2CH), 128.1
(2CH), 126.8 (2CH). Anal. calcd for C16H12N2 (232.3): C
82.73; H 5.21; N 12.06. Found C 82.68; H 5.16; N 12.00.
4-Cyano-2-phenyl-5-p-tolylpyrimidine 5c. Isolated yield 6%
(colorless crystals from EtOH), [TLC, RfZ0.43, CHCl3/
petroleum ether (40–60), 30:70]; mp 195–197 8C. MS:
m/zZ271 (MC, 100%); LCMS: m/zZ272 (MC1). 1H
NMR (CDCl3): d 9.06 (s, 1H), 8.52 (dd, 2H, JZ1.6, 8 Hz),
7.56 (m, 5H), 7.41 (d, 2H, JZ8 Hz), 2.48 (s, 3H). 13C NMR
(CDCl3): d 164.1 (pyrimidine C-2), 158.9 (pyrimidine CH),
142.4 (C), 139.1 (C), 134.7 (C), 132.9 (C), 132.0 (C), 130.0
(CH), 129.8 (2CH), 129.4 (2CH), 128.8 (2CH), 128.7
(2CH), 115.6 (CN), 21.6 (CH3). Anal. calcd for C18H13N3
(271.3): C 79.68; H 4.83; N 15.49. Found C 79.70; H 4.65;
N 15.35.
5-Phenyl-2-p-tolylpyrimidine 4b. Isolated yield 4% (color-
less crystals from EtOH), [TLC, RfZ0.43, CHCl3/
petroleum ether (40–60), 1:1]; mp 205–207 8C. MS: m/zZ
246 (MC, 100%); LCMS: m/zZ247 (MC1). 1H NMR
(CDCl3): d 9.03 (s, 2H, H-4,6), 8.39 (d, 2H, JZ8 Hz), 7.65
(d, 2H, JZ7.6 Hz), 7.55 (t, 2H, JZ7.6 Hz), 7.48 (t, 1H, JZ
7.6 Hz), 7.35 (d, 2H, JZ8 Hz), 2.46 (s, 3H). Anal. calcd for
C17H14N2 (246.3): C 82.90; H 5.73; N 11.37. Found C
82.75; H 5.56; N 11.50.
4-Cyano-2,5-di-p-tolylpyrimidine 5d. Isolated yield 4%
(colorless crystals from EtOH), [TLC, RfZ0.49, EtOAc/
petroleum ether (40–60), 1:9]; mp 160–162 8C. LCMS:
2-Phenyl-5-p-tolylpyrimidine 4c. Isolated yield 5% (color-
less crystals from EtOH). [TLC, RfZ0.48, CHCl3/
petroleum ether (40–60), 1:1)]; mp 218–220 8C. MS:
m/zZ246 (MC, 100%); LCMS: m/zZ247 (MC1). 1H
NMR (CDCl3): d 9.04 (s, 2H, H-4,6), 8.50 (d, 2H, JZ
7.8 Hz), 7.54 (m, 5H), 7.36 (d, 2H, JZ7.8 Hz), 2.46 (s, 3H).
Anal. calcd for C17H14N2 (246.3): C 82.90; H 5.73; N 11.37.
Found C 82.81; H 5.62; N 11.43.
1
m/zZ286 (MC1). H NMR (CDCl3): d 9.03 (s, 1H), 8.41
(d, 2H, JZ8 Hz), 8.52 (d, 2H, JZ8 Hz), 7.40 (d, 2H, JZ
7.8 Hz), 7.33 (d, 2H, JZ7.8 Hz), 2.46 (s, 6H).). Anal. calcd
for C19H15N3 (285.3): C 79.98; H 5.30; N 14.73. Found C
79.70; H 5.40; N 14.95.
4.2.5. 4-Cyano-2-aryl[1]benzothieno[2,3-d]pyrimidines
6. 4-Cyano-2-phenyl[1]benzothieno[2,3-d]pyrimidine 6a.
Isolated yield 8% (pale yellow crystals from EtOH),
[TLC, RfZ0.42, AcOEt/petroleum ether (40–60), 4:96];
mp 210–211 8C. MS: m/zZ287 (MC, 100%); LCMS m/zZ
288 (MC1). 1H NMR (CDCl3): d 8.81 (dd, 1H, JZ2,
6.8 Hz), 8.62 (dd, 2H, JZ1.6, 7.6 Hz), 8.00 (dd, 1H, JZ2,
7.6 Hz), 7.70 (m, 2H), 7.58 (m, 3H). 13C NMR (CDCl3): d
172.7, 161.6, 137.9, 135.7, 132.7, 131.8, 130.0, 128.9,
128.8, 128.5, 126.6, 125.7, 124.3, 123.3, 115.6. Anal. calcd
for C17H9N3S (287.4): C 71.06; H 3.16; N 14.62, S 11.16.
Found: C 71.08; H 3.10; N 14.63; S 11.25.
2,5-Di-p-tolylpyrimidine 4d. Isolated yield 4% (colorless
crystals from EtOH), [TLC, RfZ0.54, EtOAc/petroleum
ether (40–60), 1:9]; mp 213–215 8C. LCMS: m/zZ261
(MC1). IR: 3030, 2954, 2916, 2851, 1578, 1529, 1431,
1377, 1107, 1044, 813, 786, 755. 1H NMR (CDCl3): d 9.01
(s, 2H, H-4,6), 8.38 (d, 2H, JZ8 Hz), 7.54 (d, 2H, JZ8 Hz),
7.36 (d, 2H, JZ8 Hz), 7.34 (d, 2H, JZ8 Hz), 2.47, (s, 3H),
2.46 (s, 3H). 13C NMR (CDCl3): d 21.6, 21.5, 126.6, 128.0,
128.7, 129.7, 130.1, 131.3, 134.4, 138.8, 141.1, 154.9,
158.8. Anal. calcd for C18H16N2 (260.3): C 83.05; H 6.19; N
10.76. Found C 82.95; H 6.08; N 10.59.

Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
9127
4-Cyano-2-p-tolyl[1]benzothieno[2,3-d]pyrimidine 6b.
Isolated yield 8% (pale yellow crystals from EtOH), mp
234–236 8C. MS: m/zZ301 (MC, 80%); LCMS m/zZ302
(CDCl3): d 170.8, 159.3, 134.2, 134.0, 132.6, 130.9, 130.5,
129.0, 128.7, 127.8, 127.2, 126.7, 123.6. Anal. calcd for
C17H11NS2 (293.4): C 69.59; H 3.78; N 4.77; S 21.86.
Found: C 69.81; H 4.02; N 4.45; S 21.88.
1
(MC1). H NMR (CDCl3): d 8.50 (dd, 1H, JZ1.6, 8 Hz),
8.41 (d, 2H, JZ8 Hz), 8.23 (dd, 2H, JZ1.6, 8 Hz), 7.91 (dd,
1H, JZ1.6, 8 Hz), 7.36 (d, 2H, JZ8 Hz), 2.47 (s, 3H). Anal.
calcd for C18H11N3S (301.4): C 71.74; H 3.68; N 13.94; S
10.64. Found: C 71.88; H 3.57; N 14.03; S 10.75.
2-p-Tolyl-6-phenylthieno[3,2-d]thiazole 8b. LCMS m/zZ
308 (MC1).
3.6-p-Tolyl-2-phenylthieno[3,2-d]thiazole 8c. LCMS m/zZ
308 (MC1).
4-Cyano-7-methyl-2-phenyl[1]benzothieno[2,3-d]pyrimi-
dine 6c. Isolated yield 7% (pale yellow crystals from EtOH),
mp 246–248 8C. LCMS m/zZ302 (MC1). 1H NMR
(CDCl3): d 8.67 (s, 1H), 8.46 (dd, 2H, JZ1.6, 7.9 Hz),
7.95 (m, 5H), 2.48 (s, 3H). Anal. calcd for C18H11N3S
(301.4): C 71.74; H 3.68; N 13.94; S 10.64. Found: C 71.69;
H 3.75; N 14.10; S 10.61.
2,6-Di-p-Tolylthieno[3,2-d]thiazole 8d. LCMS m/zZ322
(MC1).
4.3. Pyrolysis of 5a,b with cyclohexene
A mixture each of 5a,b (30 mg) and cyclohexene (0.1 ml),
cooled in liquid nitrogen, sealed and pyrolysed as described
for compounds 1 for 15 min at 530 8C. The products showed
by HPLC, 1H NMR, LCMS the formation of the
corresponding compounds 4a,b, respectively, in approxi-
mately 80%.
4-Cyano-7-methyl-2-p-tolyl[1]benzothieno[2,3-d]pyrimi-
dine 6d. LCMS m/zZ302 (MC1).
4.2.6. 2-Aryl[1]benzothieno[2,3-d]pyrimidines 7. 2-
Phenyl[1]benzothieno[2,3-d]pyrimidine 7a. Isolated yield
4% (colorless crystals from EtOH), [TLC, RfZ0.38,
AcOEt/petroleum ether (40–60), 4:96]; mp 196–198 8C.
MS: m/zZ262 (MC, 60%); LCMS m/zZ263 (MC, 100%).
1H NMR (CDCl3): d 9.47 (s, 1H), 8.59 (dd, 2H, JZ1.7,
7.5 Hz), 8.24 (dd, 1H, JZ2, 7.5 Hz), 7.90 (dd, 1H, JZ1.8,
7.6 Hz), 7.59–7.54 (m, 5H). 13C NMR (CDCl3): d 170.8,
161.9, 149.3, 137.4, 137.3, 131.1, 130.9, 128.7, 128.5,
128.3, 125.7, 125.4, 123.3, 122.0. Anal. calcd for
C16H10N2S (262.3): C 73.26; H 3.84; N 10.68; S 12.22.
Found: C 73.58; H 3.65; N 10.41; S 12.32.
4.4. 3-Aryl-5-arylmethyl-1,2,4-triazin-6(1H)-ones 17a–d:
general procedure
To a stirred suspension of each of 16a–d11 (10 mmol) in
methanol (20 ml) was added at room temperature hydrazine
hydrate (80%, 1 ml). The mixture was kept stirring for 2 h
(the yellow starting compounds 16a–d completely dissolved
after that time and white crystals precipitated). Aqueous
NaOH solution (4%, 50 ml) was added and the mixture was
heated under reflux for 5 min. After cooling the mixture was
acidified with acetic acid and the precipitate was collected
and recrystallized from ethanol to give the corresponding
products 17a–d.
2-p-Tolyl[1]benzothieno[2,3-d]pyrimidine 7b. Isolated
yield 4% (colorless crystals from EtOH), mp 222–224 8C.
LCMS m/zZ277 (MC1). 1H NMR (CDCl3): d 9.45 (s, 1H),
8.49 (d, 2H, JZ8 Hz), 8.23 (dd, 1H, JZ2, 7.8 Hz), 7.95 (dd,
1H, JZ1.8, 7.8 Hz), 7.57 (m, 2H), 7.36 (d, 2H, JZ7.8 Hz),
2.47 (s, 3H). Anal. calcd for C17H12N2S (276.4): C 73.88; H
4.38; N 10.14; S 11.60. Found: C 73.76; H 4.53; N 10.15; S
11.48.
4.4.1. Compound 17a. Yield 85%. Pale yellow crystals, mp
178–180 8C (lit.12,13 180 8C).
4.4.2. Compound 17b. Yield 85%. Pale yellow crystals, mp
197–198 8C. MS: m/zZ277 (MC, 100%). IR: 3314, 3203,
3133, 3065, 3013, 2865, 1654, 1588, 1564, 1273, 1179,
1129, 925, 828, 737, 697, 668. 1H NMR (CDCl3): d 2.42 (s,
3H), 4.29 (s, 2H), 7.23–7.30 (m, 3H), 7.35 (t, 2H, JZ
7.6 Hz), 7.47 (d, 2H, JZ7.6 Hz), 8.03 (d, 2H, JZ8 Hz),
11.28 (br, 1H). Anal. calcd for C17H15N3O (277.3): C 73.63;
H 5.45; N 15.15. Found: C 73.57; H 5.49; N 15.35.
7-Methyl-2-phenyl[1]benzothieno[2,3-d]pyrimidine 7c. Iso-
lated yield 4% (colorless crystals from EtOH), mp 230–
232 8C. LCMS m/zZ277 (MC1). 1H NMR (CDCl3): d 9.40
(s, 1H), 8.57 (dd, 2H, JZ1.6, 8 Hz), 8.11 (d, 1H, JZ8 Hz),
7.75 (s, 1H), 7.51 (m, 3H), 8.10 (d, 1H, JZ8.4 Hz), 2.57 (s,
3H). 13C NMR (CDCl3): d 170.6, 162.3, 149.4, 137.3, 137.2,
131.1, 130.8, 129.1, 128.7, 128.4, 127.2, 125.7, 123.3,
121.8, 21.9. Anal. calcd for C17H12N2S (276.4): C 73.88; H
4.38; N 10.14; S 11.60. Found: C 73.80; H 4.45; N 10.21; S
11.38.
4.4.3. Compound 17c. Yield 90%. Pale yellow crystals, mp
208–210 8C. MS: m/zZ277 (MC, 100%), LCMS m/zZ278
(MC1). IR: 3311, 3201, 3128, 3019, 2968, 2865, 1657,
1
1591, 1568, 1465, 1272, 1125, 923, 793, 696. H NMR
7-Methyl-2-p-tolyl[1]benzothieno[2,3-d]pyrimidine 7d.
LCMS m/zZ291 (MC1).
(CDCl3): d 2.41 (s, 3H), 4.26 (s, 2H), 7.16 (d, 2H, JZ
7.6 Hz), 7.36 (d, 2H, JZ8 Hz), 7.38–7.48 (m, 3H), 8.16 (d,
2H, JZ7.6 Hz), 11.46 (br, 1H). Anal. calcd for C17H15N3O
(277.3): C 73.63; H 5.45; N 15.15. Found: C 73.60; H 5.50;
N 15.21.
4.2.7. 2,6-Diarylthieno[3,2-d]thiazoles: 8. 2,6-Di-
phenylthieno[3,2-d]thiazole 8a. Isolated yield 9% (colorless
crystals from EtOH), [TLC, RfZ0.85, AcOEt/petroleum
ether (40–60), 3:97]; mp 160–162 8C. MS: m/zZ293 (MC,
100%); LCMS m/zZ294 (MC1). 1H NMR (CDCl3): d 8.18
(d, 2H, JZ7.6 Hz), 8.08 (dd, 2H, JZ1.6, 7.6 Hz), 7.60 (s,
1H), 7.54–7.46 (m, 5H), 7.40 (t, 1H, JZ7.6 Hz). 13C NMR
4.4.4. Compound 17d. Yield 85%. Pale yellow crystals, mp
220–222 8C. MS: m/zZ291. IR: 3204, 3134, 3016, 2895,
1657, 1589, 1564, 1514, 1273, 1179, 922, 829, 669. H
1
NMR (CDCl3): d 2.34, 2.42 (2s, 6H), 4.25 (s, 2H), 7.15 (d,

9128
Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
2H, JZ8 Hz), 7.27 (d, 2H, JZ7.6 Hz), 7.37 (d, 2H, JZ
7.6 Hz), 8.04 (d, 2H, JZ8 Hz), 11.53 (br, 1H). Anal. calcd
for C18H17N3O (291.4): C 74.21; H 5.88; N 14.42. Found: C
74.37; H 6.08; N 14.67.
and adding EtOH (5 ml), the precipitate was collected and
recrystallized to give the corresponding products 20a–d.
4.6.1. Compound 20a. Yield 85%. Yellow crystals (DMF),
mp 250–252 8C. IR: 3184, 3138, 3023, 2918, 1643, 1588,
1466, 1417, 1383, 1274, 1190, 1169, 942, 875, 776, 701.
MS: m/zZ318 (MC, 100%). 1H NMR (CDCl3): d 2.83 (br,
6H, NMe2), 7.28–7.35 (m, 5H), 7.36 (m, 3H), 7.84 (d, 2H,
JZ7.6 Hz), 9.53 (s, 1H), 10.99 (br, 1H). 13C NMR (CDCl3):
d 34.7 (NCH3), 125.6 (C), 126.5 (CH), 126.7 (2CH), 127.7
(2CH), 128.1 (2CH), 129.2 (CH), 135.5 (C), 137.8 (C),
149.6 (C), 153.2 (CH), 155.4 (C), 159.2 (C). Anal. calcd for
C19H18N4O (318.4): C 71.68; H 5.70; N 17.60. Found: C
71.54; H 5.65; N 17.56.
4.5. 3-Aryl-5-[(1-aryl-2-morpholino)ethyl]-1-
morpholinomethyl-1,2,4-triazin-6(1H)-ones (Mannich
bases) 18a–d. General procedure
To a stirred cold (5 8C) solution of each of 17a–d (2 mmol)
in methanol (20 ml) was added formaldehyde (2 ml) and
morpholine (2 ml). Stirring was continued at 5 8C for 2 h
and then at room temperature overnight. The solid
precipitated was collected and recrystallized from ethanol
to give the corresponding Mannich products 18a–d.
4.6.2. Compound 20b. Yield 85%. Yellow crystals (DMF),
mp 260–262 8C. IR: 3184, 3142, 2921, 1642, 1591, 1465,
1383, 1174, 1113, 940, 872, 828. 1H NMR (CDCl3): d 2.33
(s, 3H, ArMe), 2.84 (br, 6H, NMe2), 7.09 (d, 2H, JZ8 Hz),
7.29 (m, 3H), 7.41 (d, 2H, JZ7.8 Hz), 7.68 (d, 2H, JZ
7.6 Hz), 9.48 (s, 1H), 10.18 (br, 1H, NH). Anal. calcd for
C20H20N4O (332.4): C 72.27; H 6.06; N 16.85. Found: C
72.03; H 6.10; N 16.80.
4.5.1. Compound 18a. Yield 85%. Canary yellow crystals
mp 148 8C (lit.6 148 8C).
4.5.2. Compound 18b. Yield 85%. Canary yellow crystals
mp 165–167 8C. MS: m/zZ475 (MC, 100%). 1H NMR
(CDCl3): d 2.45 (s, 3H, ArMe), 2.48 (m, 2H), 2.65 (m, 2H),
2.78 (t, 4H, JZ4.5 Hz), 2.84 (dd, 1H, JZ12.5, 4.5 Hz), 3.57
(m, 5H), 3.68 (t, 4H, JZ4.5 Hz), 4.93 (d, 1H, JZ12.8 Hz),
5.05 (m, 1H), 5.11 (d, 1H, JZ12.8 Hz), 7.24–7.34 (m, 5H),
7.47 (d, 2H, JZ7.8 Hz), 8.09 (d, 2H, JZ8 Hz). 13C NMR
(CDCl3): d 21.5, 44.0, 50.6, 53.9, 62.5, 66.9 (2CH2), 72.2,
126.4, 127.4, 128.7, 128.8, 129.8, 131.4, 138.3, 140.4,
146.7, 154.6, 171.1. Anal. calcd for C27H33N5O3 (475.6): C
68.19; H 6.99; N 14.73. Found: C 68.11; H 7.06; N 14.78.
4.6.3. Compound 20c. Yield 85%. Yellow crystals (DMF),
mp 280–282 8C. MS: m/zZ332 (MC, 100%). IR: 3184,
3140, 3025, 2965, 1645, 1589, 1465, 1383, 1280, 1188,
1110, 937, 875, 792, 700. 1H NMR (CDCl3): d 2.44 (s, 3H,
ArMe), 2.79 (br, 6H, NMe2), 7.09 (m, 4H), 7.30 (m, 3H),
7.83 (d, 2H, JZ8 Hz), 9.51 (s, 1H), 10.23 (br, 1H, NH).
Anal. calcd for C20H20N4O (332.4): C 72.27; H 6.06; N
16.85. Found: C 72.22; H 6.08; N 16.86.
4.5.3. Compound 18c. Yield 85%. Canary yellow crystals
mp 160–162 8C. MS: m/zZ475 (MC, 100%). 1H NMR
(CDCl3): d 2.32 (s, 3H, ArMe), 2.48 (m, 2H), 2.65 (m, 2H),
2.78 (t, 4H, JZ4.5 Hz), 2.84 (dd, 1H, JZ12.5, 4.5 Hz), 3.59
(m, 5H), 3.70 (t, 4H, JZ4.5 Hz), 4.93 (d, 1H, JZ12.8 Hz),
5.01 (m, 1H), 5.12 (d, 1H, JZ12.8 Hz), 7.14 (d, 2H, JZ
7.6 Hz), 7.36 (d, 2H, JZ8 Hz), 7.50 (m, 3H), 8.20 (dd, 2H,
JZ8, 1.6 Hz). 13C NMR (CDCl3): d 21.1, 43.6, 50.6, 53.9,
62.4, 66.9 (2CH2), 72.3, 126.7, 128.5, 128.7, 129.4, 130.1,
134.2, 135.2, 137.3, 146.5, 154.6, 171.4. Anal. calcd for
C27H33N5O3 (475.6): C 68.19; H 6.99; N 14.73. Found: C
68.00; H 6.98; N 14.73.
4.6.4. Compound 20d. Yield 85%. Yellow crystals (MeCN/
ETOH), mp 286–288 8C. IR: 3182, 3024, 2967, 1648, 1591,
1465, 1419, 1329, 1280, 1189, 1110, 875, 791, 702. H
1
NMR (CDCl3): d 2.33, 2.43 (2s, 6H, 2ArMe), 2.86 (br, 6H,
NMe2), 7.11 (d, 2H, JZ7.6 Hz), 7.17 (m, 4H), 7.69 (d, 2H,
JZ7.6 Hz), 9.47 (s, 1H), 10.19 (br, 1H, NH). Anal. calcd for
C21H22N4O (346.4): C 72.81; H 6.40; N 16.17. Found: C
72.65; H 6.35; N 16.18.
4.7. 5-(2-Dimethylamino-1-arylvinyl)-3-p-tolyl-1-
methyl-1,2,4-triazin-6(1H)-ones 19b
4.5.4. Compound 18d. Yield 85%. Canary yellow crystals
mp 140–142 8C. MS: m/zZ489 (MC, 100%). 1H NMR
(CDCl3): d 2.32, 2.45 (2s, 6H, ArMe), 2.45 (m, 2H), 2.65
(m, 2H), 2.78 (m, 5H), 3.61 (m, 9H), 4.91 (d, 1H, JZ
12.8 Hz), 5.00 (m, 1H), 5.11 (d, 1H, JZ12.8 Hz), 7.13 (d,
2H, JZ7.6 Hz), 7.30 (d, 2H, JZ7.6 Hz), 7.36 (d, 2H, JZ
7.6 Hz), 8.09 (d, 2H, JZ7.6 Hz). 13C NMR (and DEPT)
(CDCl3): d 21.0 (CH3), 21.5 (CH3), 43.6 (CH), 50.6 (CH2),
53.9 (CH2), 62.4 (CH), 66.9 (2CH2), 72.2 (CH2), 126.7
(2CH), 128.6 (2CH), 129.3 (2CH), 129.4 (2CH), 131.7 (C),
135.3 (C), 137.1 (C), 140.1 (C), 146.7 (C), 154.6 (C), 171.2
(C). Anal. calcd for C28H35N5O3 (489.6): C 68.69; H 7.21;
N 14.30. Found: C 68.57; H 7.34; N 14.11.
A mixture of 17b (1 mmol) and DMFDMA (1 ml) was
heated at 100 8C (steam bath) for 1 h. After cooling and
adding EtOH (5 ml), the precipitate was collected and
recrystallized from EtOH to give yellow crystals of 19b,
yield 86%, mp 168–170 8C. IR: 3055, 3029, 2920, 1637,
1
1586, 1479, 1456, 1379, 1255, 1174, 952, 827, 707. H
NMR (CDCl3): d 2.33 (s, 3H), 2.82 (br, 6H, Me2N), 3.78 (s,
3H), 7.09 (d, 2H, JZ7.8 Hz), 7.28 (m, 3H), 7.38 (t, 2H, JZ
7.8 Hz), 7.71 (d, 2H, JZ7.8 Hz) 9.45 (s, 1H). Anal. calcd
for C21H22N4O (346.4): C 72.81; H 6.40; N 16.17. Found: C
72.73; H 6.50; N 16.16.
4.8. 3-Aryl-5-arylmethyl-1,2,4-triazine-6(1H)-thiones
21a–d. General procedure
4.6. 5-(2-Dimethylamino-1-arylvinyl)-3-aryl-1,2,4-
triazin-6(1H)-ones 20a–d. General procedure
A solution of each of 17a–d (2 mmol) and phosphorus
pentasulfide (0.7 g, 3 mmol) in anhydrous pyridine (15 ml)
was heated under reflux for 3 h. After cooling the precipitate
A mixture of each of 17a–d (1 mmol) and DMFDMA (1 ml)
was heated at 100 8C (steam bath) for 5 min. After cooling

Y. A. Ibrahim et al. / Tetrahedron 60 (2004) 9121–9130
9129
was collected and recrystallized from ethanol to give the
corresponding 1,2,4-triazine-6(1H)-thiones 21a–c.
(C). Anal. calcd for C18H13N3S (303.4): C 71.26; H 4.32; N
13.85; S 10.57. Found: C 71.00; H 4.43; N 14.01; S 10.54.
4.8.1. Compound 21a. Mp 190 8C (lit.14 190 8C).
4.9.3. Compound 1c. Yellowish green crystals (DMF), mp
198–200 8C LCMS m/zZ304 (MC1). IR: 3072, 2916,
2859, 1627, 1503, 1467, 1335, 1173, 821, 696. H NMR
1
4.8.2. Compound 21b. Yield 85%. Yellow crystals, mp
208–210 8C. MS: m/zZ293 (MC, 100%). 1H NMR
(CDCl3): d 2.43 (s, 3H), 4.55 (s, 2H), 7.27–7.37 (m, 5H),
7.49 (d, 2H, JZ7.2 Hz), 8.03 (d, 2H, JZ7.6 Hz), 12.00 (br,
1H). Anal. calcd for C17H15N3S (293.4): C 69.60; H 5.15; N
14.32, S 10.93. Found: C 69.59; H 5.15; N 14.55; S 11.04.
(CDCl3): d 2.48 (s, 3H), 7.40 (d, 2H, JZ7.8 Hz), 7.58 (m,
3H), 8.01 (d, 2H, JZ8 Hz), 8.30 (s, 1H) 8.69 (dd, 2H, JZ2,
7.8 Hz). 13C NMR (CDCl3): d 21.4 (CH3), 127.8 (2CH),
128.4 (2CH), 128.9 (2CH), 129.4 (C), 129.8 (2CH), 131.3
(CH), 134.1 (CH), 134.3 (C), 135.4 (C), 138.8 (C), 149.6
(C), 160.1 (C), 160.7 (C). Anal. calcd for C18H13N3S
(303.4): C 71.26; H 4.32; N 13.85; S 10.57. Found: C 71.30;
H 4.34; N 13.71; S 10.80.
4.8.3. Compound 21c. Yield 80%. Yellow crystals, mp
218–220 8C. MS: m/zZ293 (MC, 100%). 1H NMR
(CDCl3): d 2.35 (s, 3H), 4.51 (s, 2H), 7.16 (d, 2H, JZ
7.2 Hz), 7.39 (d, 2H, JZ7.2 Hz), 7.48 (m, 3H), 8.16 (d, 2H,
JZ7 Hz), 12.00 (br, 1H). Anal. calcd for C17H15N3S
(293.4): C 69.60; H 5.15; N 14.32; S 10.93. Found: C
69.61; H 5.08; N 14.50; S 10.75.
4.9.4. Compound 1d. Yellowish green crystals (MeCN),
mp 202–204 8C MS: m/zZ317 (MC, 100%); LCMS m/zZ
318 (MC1). 1H NMR (CDCl3): d 2.48, 2.49 (2s, 6H, ArMe),
7.38 (d, 2H, JZ8 Hz), 7.39 (d, 2H, JZ8 Hz), 7.99 (d, 2H,
JZ8 Hz), 8.27 (s, 1H) 8.58 (d, 2H, JZ8 Hz). 13C NMR
(CDCl3): d 21.4, 21.6 (2CH3), 127.8 (2CH), 128.4 (2CH),
129.3 (C), 129.4 (2CH), 129.7 (2CH), 132.5 (C), 134.3
(CH), 138.8 (C), 141.8 (C), 149.8 (C), 153.2 (C), 160.2 (C),
160.4 (C). Anal. calcd for C19H15N3S (317.4): C 71.90; H
4.76; N 13.24; S 10.10. Found: C 71.69; H 4.91; N 13.30; S
10.08.
4.8.4. Compound 21d. Yield 80%. Yellow crystals, mp
230–232 8C. MS: m/zZ307 (MC, 100%). 1H NMR
(CDCl3): d 2.35, 2.43 (2s, 6H), 4.50 (s, 2H), 7.15 (d, 2H,
JZ7.6 Hz), 7.28 (d, 2H, JZ7.6 Hz), 7.38 (d, 2H, JZ
7.6 Hz), 8.05 (d, 2H, JZ7.6 Hz), 12.23 (br, 1H). Anal. calcd
for C18H17N3S (307.4): C 70.33; H 5.57; N 13.67; S 10.43.
Found: C 70.30; H 5.55; N 13.93; S 10.43.
4.9. Thieno[3,2-e][1,2,4]triazines 1a–d. General
procedure
Acknowledgements
The support of the University of Kuwait received through
research grant no. SC06/01 and the facilities of ANALAB
and SAF (grants no. GS01/01, GS02/01, GS03/01) are
gratefully acknowledged.
Method A. A solution of each of 18a–d (2 mmol) and
phosphorus pentasulfide (0.7 g, 3 mmol) in pyridine (10 ml)
was heated under reflux for 3 h. After cooling the precipitate
was collected and recrystallized from the proper solvent to
give the corresponding products 1a–d in 60–70% yields.
Method B. A solution of each of 20a–d (1 mmol) and
phosphorus pentasulfide (0.34 g, 1.5 mmol) in pyridine
(10 ml) was heated under reflux for 2 h. After cooling the
precipitate was collected and recrystallized from the proper
solvent to give the corresponding products 1a–d in ca. 85%
yields.
References and notes
1. Ibrahim, Y. A.; Al-Awadi, N. A.; Kaul, K. Tetrahedron 2001,
57, 7377–7381.
2. (a) Brown, R. F. C. Pyrolytic Methods in Organic Chemistry;
Academic: New York, 1980; pp 212–213. (b) MacBride,
J. A. H. J. Chem. Soc. Chem. Commun. 1972, 1219–1220.
(c) MacBride, J. A. H. J. Chem. Soc. Chem. Commun. 1974,
359–360. (d) Chambers, R. D.; Clark, D. T.; Holmes,
T. F.; Musgrave, W. R. K.; Ritchie, I. J. Chem. Soc. Perkin
Trans. 1 1974, 114–125. (e) Barton, J. W.; Walker, R. B.
Tetrahedron Lett. 1975, 569–572. (f) Barton, J. W.; Walker,
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Method C. A mixture of each of 21a–d (1 mmol) and
DMFDMA (1 ml) was heated under reflux for 0.5 h. After
cooling and triturating with ethanol the precipitate was
collected and recrystallized from the proper solvent to give
the corresponding products 1a–d in ca. 90% yields.
4.9.1. Compound 1a. Yellowish green crystals (EtOH), mp
198–200 8C (lit.6 mp 198 8C).
4.9.2. Compound 1b. Yellowish green crystals (EtOH), mp
203–205 8C LCMS m/zZ304 (MC1). IR: 3067, 2909,
2851, 1609, 1531, 1497, 1444, 1331, 1177, 1119, 799, 724,
1
690. H NMR (CDCl3): d 2.43 (s, 3H), 7.39 (d, 2H, JZ
8 Hz), 7.50 (t, 1H, JZ7.7 Hz), 7.59 (t, 2H, JZ7.7 Hz), 8.11
(d, 2H, JZ7.7 Hz), 8.33 (s, 1H), 8.59 (d, 2H, JZ8 Hz). 13C
NMR (CDCl3): d 21.6, 128.0 (2CH), 128.4 (2CH), 128.7
(CH), 128.9 (2CH), 129.7 (2CH), 132.3 (C), 132.4 (C),
134.2 (C), 134.8 (C), 141.7 (C), 150.3 (C), 160.4 (C), 160.6

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