1-Alkyl-3-amino-5-aryl-1H-[1,2,4]triazoles: Novel synthesis via cyclization of N-Acyl-S-methylisothioureas with alkylhydrazines and their potent corticotropin-Releasing factor-1 (CRF1) receptor antagonist activities

Article abstract of DOI:10.1016/S0960-894X(01)00657-6

Cyclizations of alkylhydrazines with N-acyl-S-methylisothioureas, readily synthesized from acyl chlorides, sodium thioisocyanate, dialkylamines then methyl iodide in a one-pot reaction, gave 1-alkyl-3-dialkylamino-5-phenyltriazoles 7 as major products. The regioisomers were assigned through the use of NOE NMR experiments. While bearing a N-bis(cyclopropyl)methyl-N-propylamino group, this series of compounds shows very good binding affinity on the human CRF₁ receptor. Among them, 1-methyl-3-[N-bis(cyclopropyl)methyl-N-propylamino]-5-(2,4-dichlorophenyl)- 1H-[1,2,4]triazole 7a had the best binding affinity for the CRF₁ receptor (K_i=9 nM).

Full text of DOI:10.1016/S0960-894X(01)00657-6

Bioorganic & Medicinal Chemistry Letters 11 (2001) 3165–3168
1-Alkyl-3-amino-5-aryl-1H-[1,2,4]triazoles: Novel Synthesis Via
Cyclization of N-Acyl-S-methylisothioureas with Alkylhydrazines
and Their Potent Corticotropin-Releasing Factor-1 (CRF1)
Receptor Antagonist Activities
Chen Chen,* Raymond Dagnino, Jr., Charles Q. Huang, James R. McCarthy
and Dimitri E. Grigoriadis
Neurocrine Biosciences, Inc., 10555 Science Centre Drive, San Diego, CA 92121, USA
Received 27 August 2001; accepted 1 October 2001
Abstract—Cyclizations of alkylhydrazines with N-acyl-S-methylisothioureas, readily synthesized from acyl chlorides, sodium
thioisocyanate, dialkylamines then methyl iodide in a one-pot reaction, gave 1-alkyl-3-dialkylamino-5-phenyltriazoles 7 as major
products. The regioisomers were assigned through the use of NOE NMR experiments. While bearing a N-bis(cyclopropyl)methyl-
N-propylamino group, this series of compounds shows very good binding affinity on the human CRF1 receptor. Among them, 1-
methyl-3-[N-bis(cyclopropyl)methyl-N-propylamino]-5-(2,4-dichlorophenyl)-1H-[1,2,4]triazole 7a had the best binding affinity for
the CRF1 receptor (Ki=9 nM). # 2001 Elsevier Science Ltd. All rights reserved.
Corticotrophin-releasing factor (CRF), a 41-amino acid
peptide, is the key regulator of an organism’s response
to stress as it mediates the endocrine, autonomic, beha-
vioral and immune effects to stressful stimuli. The
activity of CRF in the pituitary is exerted through
binding and activation to the CRF1 receptor, a member
of the seven-transmembrane G protein-coupled recep-
tors, to release of ACTH and other proopiomelano-
cortin peptides.1 Prolonged activation of brain CRF
receptors is thought to be related to the psychological
effects of stress leading to anxiety and depression.
Therefore, blockage of CRF1 receptor activation has
been proposed as a novel approach for the treatment of
these psychiatric disorders.2
compounds are comprised of a core heterocyclic ring
incorporating amino, methyl and substituted aryl func-
tionalities, the prototypical weak CRF1 antagonist 3 has
a relatively simple structure.6 In an effort of searching
for more novel structures based on this simple molecule
we discovered the heterocyclic templates 1-alkyl-2-dia-
lkylamino-5-phenyltriazoles (e.g., structure 4), which
have a topographical similarity to known CRF1 recep-
tor antagonists 3 (Fig. 1).7 In this paper, we report the
discovery of a novel cyclization for 1-alkyl-3-dialkyl-
amino-5-aryltriazoles and the structure–activity rela-
tionship studies around this nucleus that led to a potent
class of CRF1 receptor antagonists.
For SAR purposes, we required a general synthetic
method for 3-dialkylamino-5-aryltriazoles 7 that would
be amenable to rapid preparation 0of a large number of
Recent discovery of nonpeptide antagonists for CRF1
receptor has demonstrated the success of this endeavor
because several small molecules have been reported to
have good CRF1 receptor antagonistic activity.3 For
example, pyrrolo[2,3-d]pyrimidine (1, antalarmin)4 and
anilinopyrimidine (2, NBI 27914)5 show good binding
affinity as well as in vivo activity (Fig. 1). While all these
0
analogues.8 While the N-acyl-N,N -dialkylthioureas are
well known and readily prepared from the correspond-
ing acid chlorides, sodium or ammonium thioisocyanate
and dialkylamines,9 to our knowledge, neither their
cyclization with alkylhydrazines,10 nor conversion to the
corresponding S-methylisothioureas is well documented
0
(Table 1).11 We found that treatment of N-acyl-N,N0-
dialkylthioureas 9 with methyl iodide and sodium car-
0
*Corresponding author. Tel.: +1-858-658-7600; fax: +1-858-658-
7619; e-mail: cchen@neurocrine.com
bonate in acetone gave the desired N-acyl-N0N, -dialkyl-
0960-894X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00657-6

3166
C. Chen et al. / Bioorg. Med. Chem. Lett. 11 (2001) 3165–3168
S-methylisothioureas 10 in quantitative yields. The iso-
thioureas 10 were then subjected to a cyclization with
hydrazine in refluxing dioxane to give the 3-dialkyl-
amino-5-aryl-1H-[1,2,4]triazoles 11 in good yields.12
When alkylhydrazines were used in the cyclization
reactions, 1-alkyl-3-dialkylamino-5-aryl-1H-[1,2,4]tria-
zoles 7 were obtained as the major products, although,
in some cases, the isomeric 1-alkyl-3-aryl-5-dialkyl-
amino-1H-[1,2,4]triazoles 12 and the corresponding des-
methyl product 11 were also isolated as minor products.
The mechanism for the formation of 11 from the alkyl-
hydrazine is not clear, we speculated that the extra
amount of alkylhydrazine in the reaction mixture
attacks the alkyl group of the triazole 7 or 12 and deal-
kylated the product. This hypothesis, however, could
not be confirmed since refluxing pure 7c with methyl-
hydrazine in dioxane did not give detectable amount of
11c by mass spectrometry. The synthesis of the desired
triazoles 7 is outlined in Scheme 1. Attempts to cyclize
10 with phenylhydrazine under similar conditions was
not successful. Formation of 10 could also be accom-
plished from the relevant acid chloride and amine in a
one-pot reaction. Thus, sequential treatment of a solu-
tion of sodium thiocyanate in acetone with an acid
chloride, a secondary amine, then methyl iodide and
sodium carbonate gave 10 in very good to excellent
yields after a simple workup and purification.13
Alkylation of the 3-dialkylamino-5-aryl-1H-[1,2,4]tria-
zoles 11 with alkyl halides in the presence of sodium
hydride in dry THF afforded two regioisomers 7 and 12,
which were separated by chromatography on silica
gel.14 The regioisomer 1-alkyl-3-dialkylamino-5-aryl-
1H-[1,2,4]triazole 7 was always the major product. The
structures of these two regioisomers 7 and 12 were
assigned based on NMR analysis and confirmed by
NOE NMR experiments (Fig. 2).
The CRF1 receptor binding assay was performed with
cloned human CRF1 receptors expressed in CHO-cells
using [125I]o-CRF as the labeled ligand in a manner
similar to the previously reported protocol5 and the
results are summarized in Table 2. The phenotypic
compound in this series was the 1-methyl-3-{N-bis(cyclo-
propyl)methyl-N-propylamino}-5-(2,4-dichlorophenyl)-
1H-[1,2,4]triazole 7a, which was found to have good
binding affinity for hCRF1 receptor (Ki=9 nM).
Removal of the 1-methyl group resulted in almost 250-
fold loss of activity (11a, 2.4 mM). Replacement of the
1-methyl with a larger group such as ethyl or allyl (7b
and 7c, Ki=80 nM and inhibition=77% at 10 mM,
respectively) reduced the activity. Similar results were
Figure 1. Compounds 1 and 2 have been reported as potent CRF1 antagonists.
Table 1. Synthesis of N,N-dialkyl-N0-benzoyl-S-methylisothioureas 10 and their cyclizations with hydrazine and alkylhydrazines to triazoles 7 and
11
Entry
Ar
R2
Yielda
R3
Yieldb
7 or 11
10
(%)
87
(%)
1
2
3
4
5
6
7
2,4-Dichlorophenyl
2,4-Dichlorophenyl
Bis(cyclopropane)methyl
Propyl
10a
H
Me
H
Me
11a
7a
11c
7e
7q
11b
7g
90
65
43c
35d
44
78
52
56
50
72
46e
10b
10c
92
91
HOCH2CH2
2,4,6-Trimethylphenyl
Bis(cyclopropane)methyl
H
Me
8
9
10
11
CF3CH2
Me
H
Me
7i
7n
11d
7r
2-Methoxy-4-chlorophenyl
6-Methoxynaphthyl
Bis(cyclopropane)methyl
Cyclopropanemethyl
10d
10e
85
99
aSee a typical procedure in ref 12.
bSee a typical procedure in ref 13.
c3-Methylthio-5-(2,4-dichlorophenyl)-1H-[1,2,4]triazole (48%) was also isolated.
d1-Methyl-3-methylthio-5-(2,4-dichlorophenyl)-1H-[1,2,4]triazole (42%) was also isolated.
eIsomeric 1-methyl-3-(6-methoxynaphthyl)-5-(N-cyclopropylmethyl-N-propylamino)-1H-[1,2,4]triazole 12b isolated in 28% yield.

C. Chen et al. / Bioorg. Med. Chem. Lett. 11 (2001) 3165–3168
3167
Scheme 1. Reagents and conditions: (a) NaSCN/Me2CO; (b) R1R2NH/THF; (c) MeI/Na2CO3/THF; (d) NH2NH2/EtOH, reflux; (e) R3NHNH2/
EtOH, reflux; (f) R3X/NaH/THF.
Figure 2. NOE was observed between 1-methyl and ortho-proton of phenyl group for 7a, and between 1-methyl and N-methine group for 12a.
Chemical shift of ortho-proton of 12a phenyl was more downfield due to extra deshielding effect from the triazole ring.
Table 2. Triazoles 7 and 11 and their hCRF1 receptor binding data
Compd
X
R2
R3
Ki (nM)
7a
7b
7c
7d
7e
2,4-Cl
2,4-Cl
2,4-Cl
2,4-Cl
2,4-Cl
2,4-Cl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Cyclopropanemethyl
Propyl
Me
Et
9.0 (ꢁ2.0)
80 (ꢁ14)
77%a
>10,000
2600
3400
Allyl
Me
Me
Me
Me
Et
CF3CH2
Allyl
Me
Me
Me
Me
Me
Me
H
7f
2-MeOPh
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
11a
11b
12a
2,4,6-Me
2,4,6-Me
2,4,6-Me
2,4,6-Me
2,4-Me
2-Me-4-Br
2-Me-4-Cl
2-MeO-4-Cl
4-Cl
2,4-Cl-5-F
2,4-Cl
2,4,6-Me
2,4-Cl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
Bis(cyclopropane)methyl
120 (ꢁ76)
310
1500
2200
72
10 (ꢁ8)
22 (ꢁ4)
26 (ꢁ15)
33 (ꢁ5)
15 (ꢁ13)
2400
H
Me
3200
>10,000
aPercentage of inhibition at 10 mM.
obtained from the 2,4,6-trimethylphenyl analogues (7g–7j
and 11b). Replacement of the important bis(cyclopro-
pyl)methyl group with either cyclopropylmethyl, propyl
or 2-methoxyphenyl group15 greatly decreased activity
to micromolar range (7d, 7e and 7f, Kiꢀ10 mM, 2.6 and
3.4 mM, respectively).
receptor, much less active than 7a. Removal of 6-methyl
from 2,4,6-trimethylphenyl of 7g actually led to almost
2-fold increase in binding affinity (7k, Ki=72 nM).
Replacement of the 4-methyl with a bromine or chlorine
atom of the 2,4,6-trimethylphenyl triazole 7g resulted in
over 7- or 3-fold increase in binding activity (7l and 7m,
Ki=10 and 22 nM, respectively). Removal or replace-
ment of the 2-chlorine of compound 7a with a methoxy
group afforded compounds 7o or 7n, which was about
3-fold less active. Finally, introducing a fluorine atom at
Next, the effect of the substitution on the phenyl ring
was examined. The 2,4,6-trimethylanalogue 7g was
found to have a Ki of 120 nM affinity for the CRF1

3168
C. Chen et al. / Bioorg. Med. Chem. Lett. 11 (2001) 3165–3168
5-position of 2,4-dichlorophenyl group of 7a had little
effect on binding activity (7q, Ki=14 nM). While 7a
showed very good binding affinity, its regioisomer 12a
had no activity at all. Compounds 7q, 7r, 11c, 11d, and
12b (Table 1) were also inactive at 10 mM concentration.
From these SAR data we conclude that the bis(cyclo-
propyl)methyl group on the 3-aminotriazole is required
for high CRF1 activity, and the small methyl group at 1-
position of the triazole core is also very important.
11. Fazylov, S. D.; Gazaliev, A. M.; Zhivotova, T. S.; Zhur-
inov, M. Z. Russ. J. Gen. Chem. 1999, 65, 841.
12. Typical procedure: Amixture of N-bis(cyclopropyl)methyl
-N-propyl-N0-2,4,6-trimethylbenzoyl-S-methylisothiourea (10c,
124 mg, 0.33 mmol) and hydrazine (8 drops, excess) in dioxane
(10 mL) was heated at reflux for 16 h. The mixture was con-
centrated in vacuo and the product was purified by chroma-
tography on silica gel with 1:5 ethyl acetate/hexanes to give 3-
[N-bis(cyclopropyl)methyl-N-propylamino]-5-(2,4,6-trimethyl-
phenyl-1H-[1,2,4]triazole (11b, 88 mg, 78% yield) as a color-
less solid. 1H NMR (TMS/CDCl3) d 0.35 (m, 6H), 0.58 (m,
2H), 0.89 (t, J=7.6 Hz, 3H), 1.08 (m, 2H), 1.75 (m, 2H), 2.10
(s, 6H), 2.26 (s, 3H), 3.06 (t, J=7.2 Hz, 1H), 3.30 (t, J=6.8
Hz, 2H), 6.82 (s, 2H). MS (EI) m/e 339 (M+H). Anal. for
C21H30N4 (338.49): calcd C%, 74.51; H%, 8.93; N%, 16.55.
Found C%, 74.89; H%, 9.12; N%, 16.25.
In summary,
a series of 1-methyl-3-[N-bis(cyclo-
propyl)methyl-N-propylamino]-5-aryl-1H-[1,2,4]triazoles
exemplified by 7a, 7l, and 7p were synthesized through a
novel cyclization of N,N-dialkyl-N0-benzoyl-S-methyl-
isothioureas with methylhydrazine. Moreover, com-
pounds from this series were found to have good
binding affinity for the CRF1 receptor. The results of
the SAR study suggest that the bis(cyclopropyl)methyl
group on the 3-amino functionality of the triazole core
structure is important for high CRF1 receptor binding
affinity. From these studies a number of 3-dialkyl-
amino-5-aryltriazoles having high binding affinity for
the CRF1 receptor were characterized. Further studies
detailing the SAR and the consequences of their
antagonist effects towards the CRF1 receptor in vitro
and in vivo will be reported elsewhere.
13. Typical procedure: Asolution of sodium isothiocyanate
(480 mg, 6 mmol) in acetone (20 mL) was added dropwise into
a solution of 2,4,6-trimethylbenzoyl chloride (910 mg, 5
mmol), which was made fresh from the corresponding acid
and oxallyl chloride in THF. Awhite suspension formed
immediately. This mixture was heated to reflux for 10 min and
N-bis(cyclopropyl)methyl-N-propylamine (765 mg, 5 mmol)
was added. The mixture was refluxed for 1 h before MeI (1.7 g,
12 mmol) and sodium carbonate (640 mg, 6 mmol) were
introduced. The yellowish suspension was refluxed for another
3 h, cooled to room temperature, and filtered through a silica
gel pad with ethyl acetate (ꢂ100 mL). The filter was con-
centrated in vacuo to give N-bis(cyclopropyl)methyl-N-propyl-
N0-2,4,6-trimethylbenzoyl-S-methylisothiourea 10c as a yel-
lowish oil (1.86 g, quantitative), which was crystallized from
1
ether–hexanes to give a white solid. H NMR (TMS/CDCl3)
References and Notes
d 0.45 (m, 5H), 0.68 (m, 2H), 0.96 (m, 4H), 1.95 (m, 2H), 2.26
(s, 3H), 2.41 (s, 6H), 2.59 (s, 3H), 3.61 (t, J=7.4 Hz, 2H), 6.82
(s, 2H). MS (EI) m/e 373 (M+H). Anal. for C22H32N2OS
(372.57): calcd C, 70.92; H, 8.66; N, 7.52. Found C, 71.21; H,
8.73; N, 7.36.
14. Typical procedure of alkylation: Asolution of 3-(2-
dichlorophenyl)-5-(N-propyl-N-bis(cyclopropyl)methylamino)-1H-
[1,2,4]triazole (81 mg, 0.22 mmol) in dry THF was treated with
NaH (44 mg) at room temperature for 20 min, followed by
MeI (140 mg). The mixture was stirred for 2 h and TLC indi-
cated two products (1:4, EtOAc/hexanes), which was sepa-
rated by chromatography on silica gel.
1. Dieterich, K. D.; Lehnert, H.; De Souza, E. B. Endocrinol.
Diabetes 1998, 105, 65.
2. Heit, S. O.; Michael, J.; Plotsky, P.; Nemeroff, C. B.
Neuroscientist 1997, 3, 186.
3. For a recent review, see: Grigoriadis, D. E.; Haddach, M.;
Ling, N.; Saunders, J. Curr. Med. Chem. 2001, 1, 63.
4. Chen, Y. L.; Mansbach, R. S.; Winter, S. M.; Brooks, E.;
Collins, J.; Corman, M. L.; Dunaiskis, A. R.; Faraci, W. S.;
Gallaschun, R. J.; Schmidt, A.; Schulz, D. W. J. Med. Chem.
1997, 40, 1749.
5. Chen, C.; Dagnino, R., Jr.; De Souza, E. B.; Grigoriadis,
D. E.; Huang, C. Q.; Kim, K. I.; Liu, Z.; Moran, T.; Webb,
T. R.; Whitten, J. P.; Xie, Y. F.; McCarthy, J. R. J. Med.
Chem. 1996, 39, 4358.
6. Abreu, M. E.; Rzwszotarski, W.; Kyle, D. J.; Hiner, R. L.
U.S. Patent 5,063,245, 1991.
1-Methyl-3-(N-propyl-N-bis(cyclopropyl)methylamino)-5-
(2,4-dichlorophenyl)-1H-[1,2,4]triazole (7a). Major product as
a colorless solid. 1H NMR (TMS/CDCl3) d 0.40 (m, 6H), 0.60
(m, 2H), 0.99 (t, J=7.2 Hz, 3H), 1.15 (m, 2H), 1.82 (m, 2H),
3.06 (t, 1H), 3.40 (m, 2H), 3.60 (s, 3H), 7.35 (d, J=7.5 Hz,
1H), 7.40 (d, J=7.5 Hz, 1H), 7.56 (s, 1H); MS (IS) m/z 379
(M+H). Anal. for C19H24Cl2N4 (379.33): calcd C%, 60.16;
H%, 6.38; N%, 14.77. Found C%, 60.23; H%, 6.59; N%,
14.54. 1-Methyl-3-(2,4-dichlorophenyl)-5-(N-propyl-N-bis(cy-
clopropyl)methylamino)-1H-[1,2,4]triazole (12a). Minor pro-
duct as a colorless solid. 1H NMR(TMS/CDCl3) d 0.17 (m,
2H), 0.26 (m, 2H), 0.46 (m, 2H), 0.55 (m, 2H), 0.91 (t, J=7.2
Hz, 3H), 1.06 (m, 2H), 1.46 (tq, J=7.2, 7.2 Hz, 2H), 1.93 (t,
J=8.6 Hz, 1H), 3.35 (t, J=7.2 Hz, 2H), 3.76 (s, 3H), 7.28 (dd,
J=1.9, 8.2 Hz, 1H), 7.47 (d, J=1.9 Hz, 1H), 7.73 (d, J=8.2
Hz, 1H); MS (IS) m/z 380 (M+H). Anal. for C19H24Cl2N4
(379.33): calcd C, 60.16; H, 6.38; N, 14.77. Found C, 60.45; H,
6.57; N, 14.39.
7. Part of this work was reported: Chen, C.; Dagnino, R., Jr.;
Huang, C.; Wilcoxen, K.; Xie, M.; Grigoriadis, D. E.; DeSo-
uza, E. B.; McCarthy, J. R. Abstracts of Papers, Part 2, 218th
American Chemical Society National Meeting, New Orlean,
LA, August 22–26, 1999; American Chemical Society:
Washington, DC, 1999; MEDI 113.
8. Cyclization of N-(morpholino-thiocarbonyl)benzimide-
chloride with methylhydrazine in refluxing methanol gave 1-
methyl-3-morpholino-5-phenyl-1,2,4-triazole in 36% yield.
Weber, G.; Hartung, J.; Beyer, L. Z. Chem. 1986, 26, 70.
9. (a) Scozzafava, A.; Supuran, C. T. J. Med. Chem. 2000, 43,
1858. (b) Rolfs, A.; Liebscher, J. J. Org. Chem. 1997, 62, 3480.
10. Cyclization of N,N-diethyl-N0-benzoylthiourea with
hydrazine gave diethyl-(5-phenyl-1H-[1,2,4]triazol-3-yl)-amine
in low yield, Whitefield, L. L.; Papadopoulos, P. J. Heterocycl.
Chem. 1981, 18, 1197.
15. Aclose analogue, 2-( N-quinolin-5-yl-N-propyl)-4-(2,4-
dichlorophenyl)-5-methylthiazole (SR95577) was reported to
have a IC50 of 80 nM, species not reported). Wermuth, C. G.
J. Heterocycl. Chem. 1998, 35, 1091.