New efficient synthesis of 6,7,8,9-tetrahydro-benzothieno[2,3-d]-1,2,4- triazolo[1,5-a]pyrimidin-10(3H)-ones via a tandem aza-Wittig/heterocumulene- mediated annulation

Article abstract of DOI:10.1055/s-2005-865289

The carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aromatic isocyanates, reacted with hydrazine to give selectively 3-amino-2-arylamino-5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-ones 4. Reactions of 4 with triphenylphosphine, hexachloroethane and Et₃N produced iminophosphoranes 5. A tandem aza-Wittig reaction of iminophosphorane 5 with isocyanate, acyl chloride or CS₂ generated 6,7,8,9-tetrahydro- benzothieno[2,3-d]-1,2,4-triazolo[1,5-a]pyrimidin-10(3H)-ones 7, 9 or 11 in satisfactory yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-865289

PAPER
1601
New Efficient Synthesis of 6,7,8,9-Tetrahydro-benzothieno[2,3-d]-1,2,4-triazo-
lo[1,5-a]pyrimidin-10(3H)-ones via a Tandem Aza-Wittig/Heterocumulene-
Mediated Annulation
Tandem
A
za-Wittig/H
i
eterocu
n
m
ulene-Med
g
iated
A
nnula
-
tion Wu Ding,* Nian-Yu Huang, Hong-Wu He*
Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan,
430079, P. R. China
Fax +86(27)67862041; E-mail: ding5229@yahoo.com.cn
Received 2 December 2004; revised 10 January 2005
Here we wish to report a new efficient synthesis of various
2-substituted
Abstract: The carbodiimides 2, obtained from aza-Wittig reactions
6,7,8,9-tetrahydro-benzothieno[2,3-d]-
1,2,4-triazolo[1,5-a]pyrimidin-10(3H)-ones from easily
accessible iminophosphorane 1.
of iminophosphorane 1 with aromatic isocyanates, reacted with hy-
drazine to give selectively 3-amino-2-arylamino-5,6,7,8-tetrahy-
dro-benzothieno[2,3-d]pyrimidin-4(3H)-ones 4. Reactions of 4
with triphenylphosphine, hexachloroethane and Et3N produced im-
inophosphoranes 5. A tandem aza-Wittig reaction of iminophos-
phorane 5 with isocyanate, acyl chloride or CS2 generated 6,7,8,9-
tetrahydro-benzothieno[2,3-d]-1,2,4-triazolo[1,5-a]pyrimidin-
10(3H)-ones 7, 9 or 11 in satisfactory yields.
Iminophosphorane 119 reacted with aromatic isocyanates
to give carbodiimides 2, which were allowed to react with
hydrazine to give selectively 2-arylamino-3-amino-
5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-
ones 4 in 74–87% yields at room temperature (Scheme 1).
The formation of 4 can be rationalized in terms of an ini-
tial nucleophilic addition of hydrazine to give the guani-
dine intermediate 3 which cyclizes to give 4 across the
strong nucleophilic hydrazine group rather than the aryl-
amino one. Although 4 have been obtained from pro-
longed heating of corresponding thioureido derivatives
with hydrazine hydrate in 48–50% yields,11 our synthetic
method of 4 has the advantage of good yields, mild condi-
tion and easy separation of the product by simple filtra-
tion. Compounds 4 were further converted to novel
functionalized iminophosphoranes 5 via reaction with
triphenylphosphine, hexachloroethane and Et3N in good
yields (76–84%, Scheme 1).
Key words: aza-Wittig reaction, benzothieno[2,3-d]pyrimidin-
4(3H)-one, benzothieno[2,3-d]-1,2,4- triazolo[1,5-a]pyrimidin-
10(3H)-ones, triazole, iminophosphorane
The derivatives of thienopyrimidine are of great impor-
tance because of their remarkable biological properties.
For example, some thienopyrimidinones show significant
antifungal and antibacterial activities,1,2 whereas others
exhibited good anticonvulsant and angiotensin II or H1 re-
ceptor antagonistic activities.3–5 On the other hand, het-
erocycles containing 1,2,4-triazole nucleus also exhibit
various biological activities; several of them have been
used as fungicidal, bactericidal, insecticidal, antitumor
and anti-inflammatory agents.6–10 The introduction of a
triazole ring to the thienopyrimidine system is expected to
influence the biological activities significantly. In fact,
some 6,7,8,9-tetrahydro-benzothieno[2,3-d]-1,2,4-triazo-
lo[1,5-a]pyrimidin-10(3H)-ones have been reported to
display good antibacterial and anticonvulsant activi-
ties.11,12 The methods described so far for the preparation
of some representative derivatives of this ring system in-
volve either reaction of 3-amino-2-arylamino-5,6,7,8-tet-
rahydro-benzothieno[2,3-d]pyrimidin-4(3H)-ones with
triethyl orthoformate or acetic anhydride at refluxing tem-
perature,11,12 or cyclization of 3-amino-2-alkylamino-
5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-
ones with carboxylic acids or isothiocyanates.13 However,
these methods often require relatively harsh acid or the
heating at high temperature. Recently we have been inter-
ested in the synthesis of triazoloquinazolinones, thienopy-
rimidinones and imidazolinones via aza-Wittig reaction,
with the aim of evaluating their fungicidal activities.14–18
When solutions of iminophosphoranes 5 in anhydrous
CH2Cl2 were treated with aromatic isocyanate at room
temperature, the color of the reaction mixture quickly
turned red, disappearing after few minutes, and 2-aryl-
amino-6,7,8,9-tetrahydro-benzothieno[2,3-d]-1,2,4-triaz-
olo[1,5-a]pyrimidin-10(3H)-ones 7 were isolated as
crystalline solids in excellent yields (81–92%, Table 1,
Scheme 2). Presumably, the conversion of 5 into 7 in-
volves initial aza-Wittig reaction between the iminophos-
phorane 5 and the isocyanate to give a carbodiimide 6 as
highly reactive intermediate, which easily undergoes ring
closure across the arylamino group to give the otherwise
not readily available 2-arylamino substituted 6,7,8,9-tet-
rahydro-benzothieno[2,3-d]-1,2,4-triazolo[1,5-a]pyrimi-
din-10(3H)-ones 7. It is noteworthy that the reaction can
be easily carried out at room temperature under mild neu-
tral condition and the separation of 7 from the reaction
mixture was also easily carried out by simple filtration.
Iminophosphoranes 5 reacted with acyl chlorides in the
presence of Et3N in CH2Cl2 at room temperature to give 2-
substituted 6,7,8,9-tetrahydro-benzothieno[2,3-d]-1,2,4-
triazolo[1,5-a]pyrimidin-10(3H)-ones 9 in good yields
(68–83%, Table 1, Scheme 3). The formation of 9 can be
SYNTHESIS 2005, No. 10, pp 1601–1604
x
x.
x
x
.
2
0
0
5
Advanced online publication: 07.04.2005
DOI: 10.1055/s-2005-865289; Art ID: F17804SS
© Georg Thieme Verlag Stuttgart · New York

1602
M.-W. Ding et al.
PAPER
Scheme 1
viewed as an initial aza-Wittig reaction between the imi-
nophosphorane 5 and acyl chloride in presence of Et3N af-
fording the intermediate imidoyl chloride 8, which
undergoes cyclization to give 9.
Scheme 2
Table 1 Preparation of Compounds 4, 5, 7, 9 and 11
Ar1
Ar2
R
Conditions Yield (%)a
r.t./10 min 87
Scheme 3
4a
4b
5a
5b
7a
7b
7c
7d
7e
7f
Ph
4-Cl-C6H4
Ph
r.t./10 min 74
Iminophosphorane 5 reacted with CS2 in refluxing
CH2Cl2 to give 2-thioxo-6,7,8,9-tetrahydro-ben-
zothieno[2,3-d]-1,2,4-triazolo[1,5-a]pyrimidin-10(3H)-
one (11) in good yield (88%, Scheme 4, Table 1). The for-
mation of 11 can be explained by an initial aza-Wittig re-
action between the iminophosphorane 5 and CS2
affording the intermediate isothiocyanate 10, which un-
dergoes cyclization to give 11.
r.t./4 h
r.t./6 h
r.t./2 h
r.t./2 h
r.t./1 h
r.t./1 h
r.t./2 h
r.t./2 h
r.t./1 h
r.t./1 h
r.t./3 h
r.t./4 h
84
76
86
84
91
92
81
83
90
86
83
68
4-Cl-C6H4
Ph
4-Me-C6H4
3-Me-C6H4
Ph
Ph
Ph
Ph
4-Cl-C6H4
4-Me-C6H4
3-Me-C6H4
Ph
4-Cl-C6H4
4-Cl-C6H4
4-Cl-C6H4
4-Cl-C6H4
Ph
7g
7h
9a
9b
4-Cl-C6H4
Ph
Ph
Me
11
Ph
40 °C/18 h 88
a Isolated yields.
Scheme 4
Synthesis 2005, No. 10, 1601–1604 © Thieme Stuttgart · New York

PAPER
Tandem Aza-Wittig/Heterocumulene-Mediated Annulation
1603
1H NMR (400 MHz, CDCl3): d = 9.52 (s, 1 H, NH), 7.77–7.26 (m,
19 H, ArH), 2.67–2.60 (m, 4 H, 2 × CH2), 1.76–1.67 (m, 4 H, 2 ×
CH2).
In summary, we have developed an efficient synthesis of
2-substituted
6,7,8,9-tetrahydro-benzothieno[2,3-d]-
1,2,4-triazolo[1,5-a]pyrimidin-10(3H)-ones via aza-Wit-
tig reactions. This method utilizes easily accessible start-
ing material and allows mild reaction conditions,
straightforward product isolation and good yields. We
think that the synthetic approach discussed here in many
cases favorably compares with other existing methods.
MS: m/z (%) = 608 (7) [M+], 606 (20) [M+], 278 (31), 262 (100), 183
(93), 108 (34).
Anal. Calcd for C34H28ClN4OPS: C, 67.27; H, 4.65; N, 9.23. Found:
C, 67.03; H, 4.40; N, 9.31.
2-Arylamino-6,7,8,9-tetrahydrobenzothieno[2,3-d]-1,2,4-triaz-
olo[1,5-a]pyrimidin-10(3H)-ones 7; General Procedure
To a solution of iminophosphorane 5 (2 mmol) in anhyd CH2Cl2 (15
mL) was added aromatic isocyanate (2 mmol) under N2 at r.t. The
color of the reaction mixture became red, then decolorized after few
minutes. The colorless solution was stirred at r.t. for 1–2 h. The
white precipitated solid was collected by filtration and recrystal-
lized from CH2Cl2–EtOH to give 7 as a crystalline solid.
Melting points are uncorrected. MS were measured on a Finnigan
Trace MS spectrometer. IR spectra were recorded on a PE-983 in-
frared spectrometer as KBr pellets with absorption in cm–1. NMR
spectra were recorded in CDCl3 on a Varian Mercury 400 spectro-
meter and resonances are given in ppm (d) relative to TMS. Elemen-
tary analyses were taken on a Vario EL III elementary analysis
instrument.
7a
White crystals; mp 279–280 °C.
3-Amino-5,6,7,8-tetrahydrobenzothieno[2,3-d]pyrimidin-
4(3H)-ones 4; General Procedure
IR (KBr): 3258 (NH), 1664 (C=O), 1578, 1401 cm–1.
To a solution of iminophosphorane 119 (2.42 g, 5 mmol) in anhyd
CH2Cl2 (15 mL) was added aromatic isocyanate (5 mmol) under N2
at r.t. After the reaction mixture was allowed to stand for 6–12 h at
0–5 °C, the solvent was removed under reduced pressure and Et2O–
petroleum ether (1:2, 20 mL) was added to precipitate triphe-
nylphosphine oxide. The reaction mixture was filtered and the sol-
vent was removed to give carbodiimide 2, which was used directly
without further purification. To the solution of 2 prepared above in
EtOH (15 mL) was added hydrazine hydrate (0.35 g, 6 mmol, 85%)
in EtOH (5 mL). The mixture was stirred for 10 min at r.t. and fil-
tered to give 3-amino-2-arylamino-5,6,7,8-tetrahydro-benzo-
thieno[2,3-d]pyrimidin-4(3H)-ones 4.
1H NMR (400 MHz, CDCl3): d = 7.62–7.05 (m, 9 H, ArH), 6.47 (s,
1 H, NH), 3.09–2.70 (m, 4 H, 2 × CH2), 2.27 (s, 3 H, CH3), 1.92–
1.80 (m, 4 H, 2 × CH2).
MS: m/z (%) = 427 (100) [M+], 399 (61), 294 (69), 214 (40), 77 (71).
Anal. Calcd for C24H21N5OS: C, 67.43; H, 4.95; N, 16.38. Found:
C, 67.62; H, 4.81; N, 16.59.
7b
White crystals; mp >300 °C.
IR (KBr): 3248 (NH), 1673 (C=O), 1568, 1494 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.66–6.81 (m, 9 H, ArH), 6.46 (s,
1 H, NH), 3.08–2.69 (m, 4 H, 2 × CH2), 2.26 (s, 3 H, CH3), 1.92–
1.80 (m, 4 H, 2 × CH2).
4a
White crystals; mp 227–229 °C (Lit.11 mp 230–232 °C).
MS: m/z (%) = 427 (100) [M+], 399 (78), 294 (76), 214 (44), 77 (79).
4b
White crystals; mp 253–254 °C (Lit.11 mp 254–256 °C).
Anal. Calcd for C24H21N5OS: C, 67.43; H, 4.95; N, 16.38. Found:
C, 67.58; H, 5.12; N, 16.15.
N-(2-Arylamino-5,6,7,8-tetrahydrobenzothieno[2,3-d]pyrimi-
din-4(3H)-on-3-yl)iminotriphenylphosphoranes 5; General
Procedure
7c
White crystals; mp 282–283 °C.
To a mixture of 4 (8 mmol), PPh3 (3.14 g, 12 mmol) and C2Cl6 (2.84
g, 12 mmol) in anhyd CH2Cl2 (40 mL), Et3N was added dropwise
(2.42 g, 24 mmol) at r.t. The color of the reaction mixture quickly
turned to yellow. After stirring for 4–6 h, the solvent was removed
under reduced pressure and the residue was recrystallized from
EtOH to give iminophosphoranes 5.
IR (KBr): 3244 (NH), 1673 (C=O), 1574, 1477 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.70–7.06 (m, 10 H, ArH), 6.31
(s, 1 H, NH), 3.11–2.71 (m, 4 H, 2 × CH2), 1.94–1.80 (m, 4 H, 2 ×
CH2).
MS: m/z (%) = 413 (100) [M+], 385 (73), 294 (69), 207 (42), 77 (84).
Anal. Calcd for C23H19N5OS: C, 66.81; H, 4.63; N, 16.94. Found:
C, 66.65; H, 4.47; N, 17.18.
5a
White crystals; mp 279–280 °C.
IR (KBr): 3284 (NH), 1649 (C=O), 1539, 1110 cm–1.
7d
White crystals; mp 257–259 °C.
1H NMR (400 MHz, CDCl3): d = 9.50 (s, 1 H, NH), 7.78–7.02 (m,
20 H, ArH), 2.67–2.60 (m, 4 H, 2 × CH2), 1.78–1.65 (m, 4 H, 2 ×
CH2).
IR (KBr): 3415 (NH), 1681 (C=O), 1577, 1476 cm–1.
1H NMR (400 MHz, CDCl3/TFA): d = 7.74–7.24 (m, 9 H, ArH),
6.39 (s, 1 H, NH), 3.01–2.73 (m, 4 H, 2 × CH2), 1.93–1.80 (m, 4 H,
2 × CH2).
MS: m/z (%) = 572 (65) [M+], 312 (19), 262 (100), 183 (99), 108
(76).
MS: m/z (%) = 449 (35) [M+], 447 (100) [M+], 419 (54), 294 (55),
152 (26), 77 (72).
Anal. Calcd for C34H29N4OPS: C, 71.31; H, 5.10; N, 9.78. Found:
C, 71.21; H, 5.26; N, 9.88.
Anal. Calcd for C23H18ClN5OS: C, 61.67; H, 4.05; N, 15.63. Found:
C, 61.72; H, 4.24; N, 15.41.
5b
White crystals; mp 241–242 °C.
IR (KBr): 3244 (NH), 1648 (C=O), 1541, 1113 cm–1.
7e
White crystals; mp 189–190 °C.
IR (KBr): 3258 (NH), 1666 (C=O), 1574, 1476 cm–1.
Synthesis 2005, No. 10, 1601–1604 © Thieme Stuttgart · New York

1604
M.-W. Ding et al.
PAPER
2-Thioxo-6,7,8,9-tetrahydro-benzothieno[2,3-d]-1,2,4-triazo-
lo[1,5-a]pyrimidin-10(3H)-one (11)
To a solution of iminophosphorane 5 (3 mmol) in anhyd CH2Cl2 (15
mL) was added excess CS2 (3 mL) under N2 at r.t. After the reaction
mixture was refluxed for 18 h, the white precipitated solid was col-
lected by filtration to give 11.
1H NMR (400 MHz, CDCl3/TFA): d = 7.67–7.04 (m, 8 H, ArH),
6.41 (s, 1 H, NH), 2.97–2.72 (m, 4 H, 2 × CH2), 2.26 (s, 3 H, CH3),
1.94–1.80 (m, 4 H, 2 × CH2).
MS: m/z (%) = 463 (38) [M+], 461 (100) [M+], 433 (39), 328 (20),
131 (29), 91 (58).
Anal. Calcd for C24H20ClN5OS: C, 62.40; H, 4.36; N, 15.16. Found:
C, 62.63; H, 4.28; N, 15.04.
White crystals; mp 294–296 °C.
IR (KBr): 3423 (NH), 1656 (C=O), 1467, 1318, 1207 cm–1.
7f
White crystals; mp 250–251 °C.
1H NMR (400 MHz, CDCl3/TFA): d = 9.69 (s, 1 H, NH), 7.70–7.46
(m, 5 H, ArH), 3.12–2.68 (m, 4 H, 2 × CH2), 1.94–1.80 (m, 4 H,
2 × CH2).
IR (KBr): 3294 (NH), 1660 (C=O), 1576, 1475 cm–1.
1H NMR (400 MHz, CDCl3/TFA): d = 7.69–6.94 (m, 8 H, ArH),
6.36 (s, 1 H, NH), 3.00–2.74 (m, 4 H, 2 × CH2), 2.28 (s, 3 H, CH3),
1.93–1.80 (m, 4 H, 2 × CH2).
MS: m/z (%) = 354 (49) [M+], 326 (10), 293 (10), 146 (11), 40 (100).
Anal. Calcd for C17H14N4OS2: C, 57.61; H, 3.98; N, 15.81. Found:
C, 57.45; H, 4.15; N, 15.73.
MS: m/z (%) = 463 (20) [M+], 461 (54) [M+], 433 (22), 328 (19), 132
(28), 91 (100).
Acknowledgment
Anal. Calcd for C24H20ClN5OS: C, 62.40; H, 4.36; N, 15.16. Found:
C, 62.51; H, 4.45; N, 15.12.
We gratefully acknowledge financial support of this work by the
National Key Project for Basic Research (2003CB114400,
2003CB114406) and the National Natural Science Foundation of
China (Project No. 20372023 and 20102001).
7g
White crystals; mp >300 °C.
IR (KBr): 3262 (NH), 1674 (C=O), 1573, 1475 cm–1.
1H NMR (400 MHz, CDCl3/TFA): d = 7.70–7.15 (m, 9 H, ArH),
6.44 (s, 1 H, NH), 3.00–2.74 (m, 4 H, 2 × CH2), 1.94–1.80 (m, 4 H,
2 × CH2).
References
(1) Walter, H. WO 9911631, 1999; Chem. Abstr. 1999, 130,
237580e.
(2) Aboulwafa, O. M.; Ismail, K. A.; Koreish, E. A. Farmaco
1992, 47, 631.
MS: m/z (%) = 449 (21) [M+], 447 (57) [M+], 419 (22), 328 (18), 118
(37), 77 (100).
Anal. Calcd for C23H18ClN5OS: C, 61.67; H, 4.05; N, 15.63. Found:
C, 61.74; H, 4.24; N, 15.57.
(3) Santagati, M.; Modica, M.; Santagati, A.; Russo, F.;
Spampinato, S. Pharmazie 1996, 51, 7.
(4) Taguchi, M.; Ota, T.; Hatayama, K. WO 9303040, 1993;
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Eur. J. Med. Chem. 2000, 35, 351.
7h
White crystals; mp >300 °C.
IR (KBr): 3254 (NH), 1667 (C=O), 1571, 1475 cm–1.
(6) Onodera, J.; Sato, S.; Kumazawa, S.; Ito, A.; Saishoji, S.;
Niizeki, Y. JP 96127568, 1996; Chem. Abstr. 1996, 125,
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Swami, S.; Ray, S. J.; Richardson, K.; Troke, P. F. Bioorg.
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1H NMR (400 MHz, CDCl3/TFA): d = 7.70–7.27 (m, 8 H, ArH),
6.32 (s, 1 H, NH), 3.02–2.74 (m, 4 H, 2 × CH2), 1.92–1.80 (m, 4 H,
2 × CH2).
MS: m/z (%) = 485 (11) [M+], 483 (53) [M+], 481 (81) [M+], 453
(40), 328 (39), 152 (74), 111 (100).
(8) Ulusoy, N.; Gursoy, A.; Otuk, G. Farmaco 2001, 56, 947.
(9) Hegde, V. B.; Bis, S. J.; Heo, E. C.; Hamilton, C. T.;
Johnson, P. L.; Karr, L. L.; Martin, T. P.; Neese, P. A.; Orr,
N.; Tisdell, F. E.; Yap, M. C. H.; Zhu, Y. US 20020019370,
2002; Chem. Abstr. 2002, 136, 146541.
Anal. Calcd for C23H17Cl2N5OS: C, 57.27; H, 3.55; N, 14.52.
Found: C, 57.14; H, 3.39; N, 14.64.
6,7,8,9-Tetrahydrobenzothieno[2,3-d]-1,2,4-triazolo[1,5-a]pyri-
midin-10(3H)-ones 9; General Procedure
(10) Palaska, E.; Sahin, G.; Kelicen, P.; Durlu, N. T.; Altinok, G.
Farmaco 2002, 57, 101.
(11) El-Sherbeny, M. A.; El-Ashmawy, M. B.; El-Subbagh, H. I.;
El-Emam, A. A.; Badria, F. A. Eur. J. Med. Chem. 1995, 30,
445.
To a solution of iminophosphorane 5 (2 mmol) in anhyd CH2Cl2 (15
mL) were added acyl chloride (2 mmol) and Et3N (0.20 g, 2 mmol)
under N2 at r.t. The solution was stirred at r.t. for 2–4 h. The white
precipitated ammonium salt was separated by filtration and the fil-
trate was concentrated to dryness. The residue was recrystallized
from CH2Cl2–EtOH to give 9 as a crystalline solid.
(12) Santagati, M.; Modica, M.; Santagati, A.; Russo, F.;
Spampinato, S. Pharmazie 1996, 51, 7.
(13) Pathak, U. S.; Rathod, I. S.; Jain, K. S.; Laddha, N. S.;
Kolhe, K. S. Indian J. Chem., Sect B: Org. Chem. Incl. Med.
Chem. 1997, 36, 566.
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8366.
9a
White crystals; mp >300 °C.
IR (KBr): 1689 (C=O), 1585, 1473, 1399 cm–1.
1H NMR (400 MHz, CDCl3/TFA): d = 7.65–7.36 (m, 10 H, ArH),
3.07–2.77 (m, 4 H, 2 × CH2), 1.95–1.80 (m, 4 H, 2 × CH2).
(15) Ding, M. W.; Chen, Y. F.; Huang, N. Y. Eur. J. Org. Chem.
2004, 3872.
MS: m/z (%) = 398 (100) [M+], 370 (40), 294 (8), 103 (13), 77 (43).
(16) Ding, M. W.; Yang, S. J.; Zhu, J. Synthesis 2004, 75.
(17) Ding, M. W.; Fu, B. Q.; Cheng, L. Synthesis 2004, 1067.
(18) Ding, M. W.; Sun, Y.; Liu, Z. J. Synth. Commun. 2003, 33,
1267.
(19) Wamhoff, H.; Herrmann, S.; Stolben, S.; Nieger, M.
Tetrahedron 1993, 49, 581.
Anal. Calcd for C23H18N4OS: C, 69.33; H, 4.55; N, 14.06. Found:
C, 69.14; H, 4.48; N, 14.23.
9b
White crystals; mp 279–280 °C (Lit.11 mp 281–283 °C).
Synthesis 2005, No. 10, 1601–1604 © Thieme Stuttgart · New York