Synthesis of novel tricyclic aryltriazole-3-thione compounds

Article abstract of DOI:10.1081/SCC-200048912

A new synthetic protocol has been developed to provide entry into a series of novel tricyclic aryltriazole-3-thiones analogs. The classical reaction conditions of subjecting an arylhydrazide with thiophosgene to form the thioisocyanate intermediate and ultimately the corresponding aryltriazole-3-thione framework were not successful. However, using a combination of carbon disulfide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to form the thioisocyanate intermediate was found to produce the novel tricyclic aryltriazole-3-thiones (5, 8a-c) in good yield. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200048912

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Synthesis of Novel Tricyclic
Aryltriazole‐3‐Thione
Compounds
Cuiman Cai a , Janet S. Plummer a , David Connor a ,
Daniel D. Holsworth a & Jeremy J. Edmunds a
a Pfizer Global Research and Development, Michigan
Laboratories, Department of Chemistry, 2800
Plymouth Road, Ann Arbor, MI, 48105, USA
Version of record first published: 28 Jul 2007
To cite this article: Cuiman Cai, Janet S. Plummer, David Connor, Daniel D. Holsworth
& Jeremy J. Edmunds (2005): Synthesis of Novel Tricyclic Aryltriazole‐3‐Thione
Compounds, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:3, 349-356
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Synthetic Communicationsw, 35: 349–356, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200048912
Synthesis of Novel Tricyclic Aryltriazole-
3-Thione Compounds
Cuiman Cai, Janet S. Plummer, David Connor, Daniel D. Holsworth,
and Jeremy J. Edmunds
Pfizer Global Research and Development, Michigan Laboratories,
Department of Chemistry, Ann Arbor, MI, USA
Abstract: A new synthetic protocol has been developed to provide entry into a series of
novel tricyclic aryltriazole-3-thiones analogs. The classical reaction conditions of sub-
jecting an arylhydrazide with thiophosgene to form the thioisocyanate intermediate and
ultimately the corresponding aryltriazole-3-thione framework were not successful.
However, using a combination of carbon disulfide and 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) to form the thioisocyanate intermediate was found to produce the
novel tricyclic aryltriazole-3-thiones (5, 8a–c) in good yield.
Keywords: Aryltriazoles, thioisocyanate
INTRODUCTION
As part of a high throughput screen to discover anti-inflammatory agents and
in particular, agents that would inhibit Mac-1 (Macrophase antigen-1), a series
of aryltriazole-3-thiones compounds were identified. While initial lead
compounds were synthesized by a number of previously known procedures,[1]
a new synthetic process was needed to encompass a series of novel six- and
seven-member tricyclic aryltriazole-3-thiones (5, 8a–c) for further SAR
analysis (Scheme 1).
Received in the USA October 29, 2004
Address correspondence to Daniel D. Holsworth, Pfizer Global Research and
Development, Michigan LaboratoriesDepartment of Chemistry, 2800 Plymouth
Road, Ann Arbor, MI 48105, USA. Fax: 734-622-3909; E-mail: cuiman.cai@pfizer.
com; daniel.holsworth@pfizer.com

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C. Cai et al.
Scheme 1. Synthetic targets. Six- and seven-member tricyclic aryltriazole-3-thiones.
The first tricyclic compound synthesized in the series was 5,6-dihydro-
2H-[1,2,4]triazolo[3,4-a]isoquinoline-3-thione 5, which originated from the
known 3,4-dihydro-1-(2H)-isoquinolinone 1 (Scheme 2). Generation of the
isoquinolinethione 2 with Lawesson’s reagent followed by activation of
the thioamide by alkylation with methyl iodide afforded the intermediate
thioether 3. Generation of the corresponding hydrazino compound 4 by
subjecting thioether 3 to hydrazine proceeded in excellent yield. It should
be noted that alternative attempts to prepare the hydrazino-isoquinoline 4
via the iminochloride or iminotriflate failed due to either inefficient
Scheme 2. Preparation of 5,6-dihydro-2H-[1,2,4]triazolo[3,4a]isoquinoline-3-
thione (5).

Synthesis of Novel Tricyclic Aryltriazole-3-Thione Compounds
351
generation of the iminochloride or ring opening of the iminotriflate to generate
the trifluoro-N-[2-(2-hydrazinocarbonyl-phenyl)-ethyl]-methanesulfonamide
upon treatment with hydrazine. Exposure of the hydrazino intermediate 4
with thiophosgene in methylene chloride 08C for 45 min followed by reflux
in trichlorobenzene for 4 h, afforded the tricyclic aryltriazole-3-thione 5 in
modest yield.
The thiomethyl analogs 6a–c were synthesized via literature methods
(see experimental). Using the same reaction conditions as for compound 4,
hydrazino analogs 7a–c were formed. Interestingly, unlike the synthesis of
compound 5 (Scheme 2), the cycloaddition between hydrazino analogs 7a–
c and thiophosgene did not produce the expected products, but rather
resulted in complex mixtures. Therefore, an alternative synthetic protocol
was devised. Carbon disulfide in the presence of DBU has shown to react
with 20-aminobenzamides to form 4-oxo-2-thio-1,2,3,4-tetrahydroquinazo-
lines via the isothiocyanate intermediate.[2] Further, a mixture of carbon
disulfide and triethylamine has been used to create thioisocyanate intermedi-
ates from primary amines.[2] Using the reaction conditions outlined by
Mizuno, Nishiguchi, and Okushi[3] with hydrazino analogs 7a–c, the pro-
duction of the desired tricyclic aryltriazole-3-thiones 8a–c were obtained in
good yield (Scheme 3).
In summary, both six- and seven-membered novel tricyclic aryltriazole-3-
thiones have been prepared. While the classical triazole-3-thione synthetic
procedure failed[4] the use of carbon disulfide and DBU greatly facilitated
Scheme 3. Synthetic protocol for the production of novel aryltriazole-3-thiones 8a–c.

352
C. Cai et al.
the formation of the desired products via the thioisocyanate intermediate.
These reaction conditions have provided the synthesis of novel tricyclic aryl-
triazole-3-thiones under mild conditions with vastly improved yields.
EXPERIMENTAL
All starting materials were obtained from commercial sources unless
otherwise specified in the experimental section. Proton NMR spectra were
obtained on a Varian Unity 400 MHz or 200 MHz spectrometer. Elemental
analyses were determined on a Perkin-Elmer model 240C instrument or
were determined by Robertson Labs. Mass spectral data were obtained on a
VG Analytical 7070 E/HF mass spectrometer using chemical ionization
conditions. Flash column chromatography was performed on silica gel 60,
230–400 mesh, purchased from Mallinckrodt.
3,4-Dihydro-1(2H)-isoquinolinone (1)
Isoquinolinone (5.3 g, 36.5 mmol) in acetic acid (100 mL) was hydrogenated
over 20% Pd/C (0.5 g) for 20 h at rt. The mixture was filtered through a
pad of celite and evaporated in vacuo. The residue was dissolved in
ethyl acetate, washed with saturated sodium bicarbonate, water, dried over
magnesium sulfate, filtered, and evaporated in vacuo to yield 1 (4.92 g,
92%). M.P. ¼ 57–598C [lit.[5] ¼ 588C]; 1H NMR (d6-DMSO, 200 MHz)
d 7.94 (brs, 1H), 7.85–7.81 (m, 1H), 7.47–7.42 (m, 1H), 7.36–7.27
(m, 2H), 3.40–3.32 (m, 2H), 2.92–2.86 (m, 2H); MS ¼ 148 (M þ 1).
3,4-Dihydro-1(2H)-isoquinolinethione (2)
To 3,4-dihydro-1 (2H)-isoquinolinone (0.44 g, 3.0 mmol) in THF (20 mL) was
added Lawesson’s reagent (0.51 g, 1.25 mmol). The solution was stirred
overnight at rt and then heated to 508C for 60 h. The solution was cooled to
rt and diluted with ethyl acetate. The organic layer was washed with
saturated sodium bicarbonate, brine, dried over magnesium sulfate, filtered,
and evaporated in vacuo. The residue was purified by column chromatography
(2% methanol/98% methylene chloride) to give 0.47 g (97%) of 2.
1
M.P. ¼ 96–978C [lit.[2] ¼ 988C]; H NMR (d6-DMSO, 200 MHz) d 10.49
(brs, 1H), 8.31 (d, J ¼ 7.69 Hz, 1H), 7.52–7.45 (m, 1H), 7.37–7.26
(m, 2H), 3.43–3.48 (m, 2H), 2.95–2.88 (m, 2H); MS ¼ 164 (M þ 1).

Synthesis of Novel Tricyclic Aryltriazole-3-Thione Compounds
3,4-Dihydro-1-(methylthio)-isoquinoline (3)
353
To 3,4-dihydro-1 (2H)-Isoquinolinone (0.30 g, 1.84 mmol) in methylene
chloride (5 mL) was added methyl iodide (0.34 mL, 5.51 mmol), and the
solution was stirred overnight at rt. The solvent was evaporated in vacuo
and the resultant residue diluted with ethyl acetate. The organic layer was
washed with saturated sodium bicarbonate, water, dried over magnesium
sulfate, filtered, and evaporated in vacuo to afford 0.28 g (92%) of 3 hydroio-
dide. M.P. ¼ 98–1008C [lit.[2] ¼ 998C]; 1H NMR (CDCl3, 200 MHz) d 7.68–
7.63 (m, 1H), 7.36–7.17 (m, 3H), 3.79–3.76 (m, 2H), 2.78–2.70 (m, 2H),
2.45 (s, 3H); MS ¼ 178 (M þ 1).
3,4-Dihydro-1-(hydroazino)-isoquinoline (4)
To 3,4-dihydro-1-(methylthio)-isoquinoline (0.80 g, 4.52 mmol) in aceto-
nitrile (10 mL) was added hydrazine [Caution! Highly toxic. Use in a good
fume hood] (1.5 mL, 47.7 mmol) and the solution heated at reflux for 1.5 h.
The solution was cooled and concentrated in vacuo. The residue was triturated
with hexane to give 0.82 g (92%) of 4. M.P. ¼ 56–588C [lit.[6] ¼ 55–578C];
1H NMR (CDCl3, 200 MHz): d 8.05–8.00 (m, 1H), 7.36–7.19 (m, 3H), 4.53
(brs, 3H), 3.52–3.46 (m, 2H), 2.96–2.90 (m, 2H); MS ¼ 162 (M þ 1).
5,6-Dihydro-2H-[1,2,4]triazolo[3,4-a]isoquinoline-3-thione (5)
To thiophosgene [Caution! Highly toxic. Use in a good fume hood] (0.34 ml,
4.47 mmol) in methylene chloride (5 mL) was added drop-wise to a solution
consisting of 3,4-dihydro-1-(hydroazino)-isoquinoline (0.48 g, 2.98 mmol)
in methylene chloride (5 mL) and triethylamine (1.25 mL, 8.94 mmol) at
08C over a period of 45 min. The solvent was removed and trichlorobenzene
(25 mL) added. The solution was refluxed for 4 h, and then the mixture
reduced to a residue in vacuo. Methylene chloride was added and the
organic layer washed with water. The product was extracted into 0.5 N
NaOH and upon addition of 10% acetic acid, a precipitate formed. The
precipitate was collected and purified by column chromatography (1 : 1
ethyl acetate/hexane) to provide 0.19 g (30%) of 5. M.P. ¼ 200–2018C;
1H NMR (d6-DMSO, 400 MHz) d 13.76 (s, 1H), 7.775 (d, J ¼ 7 Hz, 1H),
7.40 (m, 3H), 3.98 (t, J ¼ 8 Hz, 2H), 3.13 (t, J ¼ 8 Hz, 2H); 13C NMR
(d6-DMSO, 100 MHz) d 166.17, 147.85, 135.27, 131.72, 129.38, 128.22,
124.29, 122.91, 39.20, 27.54; MS ¼ 204 (M þ 1); Anal. Calcd. for
C10H9N3S1: C, 59.09; H, 4.46; N, 20.67; found: C, 59.39; H, 4.63; N, 20.67.

354
C. Cai et al.
(4,5-Dihydro-3H-2-benzazepin-1-yl)-hydrazine (7a)
1-Methylsulfanyl-2,3,4,5-tetrahydro-1H-benzo[C]azepine [6a,[7] 0.82 g,
4.29 mmol] in acetonitrile (10 mL) was added hydrazine [Caution! Highly
toxic. Use in a good fume hood] (1.0 mL, 31.8 mmol). The solution was
heated at reflux for 1.5 h and then cooled to rt. A precipitate formed upon
cooling, which was collected and crystallized from acetonitrile to provide
1
0.62 g (83%) of 7a, which was used immediately in the next step. H NMR
(d6-DMSO, 200 MHz) d 7.41–7.36 (m, 1H), 7.27–7.12 (m, 3H), 4.72 (brs,
1H), 3.34 (brs, 2H), 2.96–2.90 (m, 2H), 2.74–2.67 (m, 2H), 1.84–1.71
(m, 2H); MS ¼ 176 (M þ 1).
(2,3-Dihydro-1,4-benzoxazepin-5-yl)-hydrazine (7b)
To 5-Methylsulfanyl-2,3-dihydro-1,4-benzoxazepine [6b,[4] 1.62g, 8.28mmol]
in acetonitrile (20 mL) was added hydrazine [Caution! Highly toxic. Use in a
good fume hood] (5 mL). The solution was heated at reflux for 1 h, cooled to
rt, and an additional 3 mL of hydrazine was added. The mixture was heated
at reflux for an additional 5 h and then at rt overnight. The mixture was
subjected to column chromatography (85 : 15 CH2Cl2/10% NH4OH in
EtOH) to provide 0.73 g (50%) of 7b, which was used immediately in the
1
next step. H NMR (d6-DMSO, 400 MHz) d 8.41 (dd, J ¼ 7.95, 1.69 Hz,
1H), 7.36 (ddd, J ¼ 7.95, 6.99, 1.69 Hz, 1H), 7.15 (dd, J ¼ 7.95, 8.20 Hz,
1H), 7.07 (d, J ¼ 8.19 Hz, 1H), 4.45 (m, 2H), 4.34 (m, 2H); MS ¼ 178 (M þ 1).
(6,7-Dihydro-5-thia-8-aza-benzocyclohepten-9-yl)-hydrazine (7c)
9-Methylsulfanyl-6,7-dihydro-5-thia-8-aza-benzocycloheptene [6c,[8] 0.37 g,
1.74 mmol] in acetonitrile (15 mL) was added hydrazine [Caution! Highly
toxic. Use in a good fume hood] (5 mL) and 4 Angstrom molecular sieves.
The solution was heated at reflux for 6 h, cooled to rt, and an additional
7 mL of hydrazine was added. The mixture was stirred at rt overnight. The
reaction mixture was concentrated in vacuo and the residue was subjected
to column chromatography (85 : 15 CH2Cl2: 10% NH4OH/EtOH) to yield
1
0.16 g (48%) of 7c, which was used immediately in the next step. H NMR
(d6-DMSO, 400 MHz) d 7.45–7.30 (m, 4H), 6.00 (s, 1H), 4.85 (brs, 2H),
3.21–3.15 (m, 2H), 2.97–2.92 (m, 2H); MS ¼ 194 (M þ 1).
2,4,5,6-Tetrahydro-1,2,3a-triaza-benzo[e]azulene-3-thione (8a)
To a solution of DMF (3.5 mL) carbon disulfide [Caution! Highly toxic. Use in
a good fume hood] (2.1 mL, 34.2 mmol) and DBU (0.26 ml, 1.71 mmol) was

Synthesis of Novel Tricyclic Aryltriazole-3-Thione Compounds
355
added 7a (0.30 g, 1.71 mmol). The solution was refluxed for 40 min, cooled to
rt, and diluted with ethyl acetate. The organic layer was washed with saturated
sodium bicarbonate, water, dried with magnesium sulfate, filtered, and evap-
orated in vacuo. The residue was purified by column chromatography (1 : 1
ethyl acetate/hexane) to yield 0.17 g (45%) of 8a. M.P. ¼ 144–1458C;
1H NMR (d6-DMSO, 400 MHz) d 13.90 (brs, 1H), 7.65–7.63 (m, 1H),
7.50–7.46 (m, 1H), 7.42–7.37 (m, 2H), 3.89 (t, J ¼ 8 Hz, 2H), 2.69
(t, J ¼ 4 Hz, 2H), 2.13 (q, J ¼ 8 Hz, 2H); 13C NMR (d6-DMSO, 100 MHz) d
166.98, 152.59, 139.77, 131.75, 130.73, 128.66, 127.86, 109.99, 41.94,
30.54, 28.58; MS ¼ 218 (M þ 1); Anal. Calcd. for C11H11N3S1: C, 60.80;
H, 5.10; N, 19.34; found: C, 60.97; H, 5.10; N, 20.18.
4,5-Dihydro-2H-6-oxa-1,2,3a-triaza-benzo[e]azulene-3-thione (8b)
To a solution of DMF (1.8 mL), carbon disulfide [Caution! Highly toxic. Use
in a good fume hood] (1.8 mL, 29.6 mmol) and DBU (0.22 mL, 1.68 mmol)
was added drop-wise to a solution of 7b (0.26 g, 1.48 mmol) in DMF
(3.5 mL). The mixture was heated at reflux for 2.5 h, then cooled to room
temperature, acidified with 1N HCL, and allowed to sit at rt. A precipitate
formed after 1 hr. Purification of the crude compound by column chromato-
graphy (10% CH3OH/CHCl3) afforded 0.17 g (52%) of 8b. M.P. ¼ 245–
1
2508C (decomp); H NMR (d6-DMSO, 400 MHz) d 13.98 (brs, 1H), 8.105
(dd, J ¼ 4, 8 Hz, 1H), 7.37 (dddd, J ¼ 4, 8, 12, 16 Hz, 1H), 7.10 (dddd,
J ¼ 4, 8, 12, 16 Hz, 1H), 7.04 (dd, J ¼ 4, 8 Hz, 1H), 4.45 (m, 2H), 4.25
(m, 2H); 13C NMR (d6-DMSO, 100 MHz) d 167.61, 157.29, 149.29, 132.62,
129.14, 123.28, 121.71, 114.30, 68.94, 48.64; MS ¼ 220 (M þ1); Anal.
Calcd. for C10H9N3O5: C, 54.78; H, 4.14; N, 19.16; found: C, 54.88; H,
4.10; N, 19.18.
4,5-Dihydro-2H-6-thia-1,2,3a-traza-benzo[e]azulene-3-thione (8c)
To a solution of DMF (1 mL), carbon disulfide [Caution! Highly toxic. Use
in a good fume hood] (1 mL, 16.6 mmol) and DBU (0.12 mL, 0.83 mmol)
was added drop-wise to a solution of 7c (0.16 g, 0.83 mmol) in DMF. The
mixture was heated to reflux for 25 min. After cooling to rt, the solution
was acidified with 1N HCL and stirred for 30 min to yield a orange sticky
solid. The solid was subjected to column chromatography (1 : 1 ethyl
1
acetate/hexane) to afford 0.13 g (68%) of 8c. M.P. ¼ 193–1968C; H NMR
(d6-DMSO, 400 MHz) d 7.71–7.66 (m, 2H), 7.56–7.52 (m, 2H), 4.13
(t, J ¼ 4 Hz, 2H), 3.34 (t, J ¼ 4 Hz, 2H); 13C NMR (d6-DMSO, 100 MHz) d
166.90, 152.23, 135.21, 132.49, 132.04, 131.46, 130.60, 129.98, 42.18,
35.79; MS ¼ 236 (M þ 1); Anal. Calcd for C10H9N3S2: C, 51.04; H, 3.85;
N, 17.86; found: C, 50.77; H, 4.05; N, 17.51.

356
C. Cai et al.
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