Efficient syntheses of new CF3-containing diazolopyrimidines

Article abstract of DOI:10.1055/s-2002-19313

A new simple and efficient way to CF₃-containing pyrimido[1,2-a]benzimidazole and pyrazolo[1,5-a]pyrimidines, by the reaction of 1,1,1-trifluoro-4-sulfonyl-but-3-ene-2,2-dioles 1a,b with aminoheterocycles is described. The influence of reaction conditions and nature of the aminoheterocycles on regiochemistry was investigated.

Full text of DOI:10.1055/s-2002-19313

PAPER
133
Efficient Syntheses of New CF3-containing Diazolopyrimidines
Efficient
S
yntheser 3
s
of
N
ew
c
CF
-
contai
a
ning Diaz
o
d
lopyrimidine
y
s
L. Krasovsky, Anton S. Hartulyari, Valentine G. Nenajdenko,* Elizabeth S. Balenkova
Department of Chemistry , Moscow State University , 119899 Moscow, Russia
Fax +7(95)9328846; E-mail: Nen@acylium.chem.msu.su
Received 1 August 2001; revised 8 October 2001
pyrrole, indole and furan.21 Also, we have recently de-
scribed a new simple and efficient regiospecific synthesis
of 2-CF3-imidazo[1,2-a]pyridines and 2-CF3-imida-
zo[1,2-a]quinolines by the reaction of sulfones 1a,b with
Abstract: A new simple and efficient way to CF3-containing py-
rimido[1,2-a]benzimidazole and pyrazolo[1,5-a]pyrimidines, by
the reaction of 1,1,1-trifluoro-4-sulfonyl-but-3-ene-2,2-dioles 1a,b
with aminoheterocycles is described. The influence of reaction con-
ditions and nature of the aminoheterocycles on regiochemistry was various 2-aminopyridines and 2-aminoquinoline.22 It was
investigated.
therefore considered that the reactivity of dioles 1a,b with
aminoazoles might result in improved regioselectivity
yielding only one regioisomer.
Key words: cycloaddition, heterocycles, pyrimido[1,2-a]benzimi-
dazole, pyrazolo[1,5-a]pyrimidines, sulfones
The reaction of 2-amino-1H-benzimidazol with sulfones
1a,b proceeds at room temperature in acetonitrile to give
the cyclic product tetrahydropyrimido[1,2-a]benzimida-
zol-2-ol 3 in high yield. We investigated the possibility of
the preparation of aromatic heterocycle 2 from the cy-
cloadduct 3. The best results were obtained under reflux
in acetic acid. In this case tandem elimination of water and
sulfinic acid take place to give cycloadduct 3 in 80% total
yield from 2-aminobenzimidazole. We also found reac-
tion conditions to perform a one-step procedure for the
preparation of 2 from 2-amino-1H-benzimidazol and sul-
fones 1a,b under reflux in water (Scheme 1).
The synthesis of condensed pyrazoles has recently been
reviewed.1,2 The development of new methods for the syn-
thesis of trifluoromethyl-substituted pyrimidines and con-
densed cyclic derivatives is a topic of current interest3–5
because of their activity as herbicides6 and plant growth
regulators.7 The substitution pattern of the azolopyrimi-
dine greatly influences the degree of activity and the mode
of action, so it is important to develop syntheses with re-
gioselective control. The reported methods for the synthe-
sis of substituted azolopyrimidines usually involve
cyclocondensation of aminoazoles with three carbon 1,3-
electrophilic fragments such as -ketoesters, -diketones,
-ketoaldehydes, enolethers, acetal esters, ketoesters8–16
or , -unsaturated carbonyl compounds.1,16–19 A limita-
tion of these approaches is the difficulty of establishing
products resulting from reaction of non-symmetrical sys-
tems with aminopyrazoles. Several new pyrazolopyrim-
idines were synthesized via the reaction of
aminopyrazoles with 3-dimethylaminopropiophenone
and tetracyanoethene.17 Some reactions involving re-
giospecific modification of initially prepared azolopyrim-
idines ring have also been developed recently.12,18
There is only a limited amount of literature on the re-
giospecific synthesis of 7- and 5-substituted azolopyrim-
idines. Therefore there is a definite need to develop new
methods for the synthesis of this class of compounds.
Scheme 1
The molecular structure of heterocycles 2 and 3 were de-
termined by spectroscopy and structure 2 was assigned by
1H NMR on the basis of the double resonance and NOE.
We report now the results of our investigation of the reac-
tion of 1,1,1-trifluoro-4-sulfonyl-but-3-ene-2,2-dioles
1a,b with 2-amino-1H-benzimidazol and aminopyra-
zoles.
To extend the scope of this reaction, we performed other
condensations of 1a,b with various aminopyrazoles as nu-
cleophiles.
In recent work we have prepared some -trifluoro-
acetylvinylsulfones by oxidation of the readily available
sulfanes.20 We have found that these alkenes 1a,b are very
powerful electrophiles, reacting with heteroarenes such as
The treatment of sulfones 1a,b with different 3-aminopy-
razoles in acetic acid under reflux gave 7-CF3 substituted
cycloadducts 4a–m accompanied by 5-trifluoromethyl
compounds 5a–m as minor isomers. The total yields of
these reactions are almost quantitative (Scheme 2). It is
worth mentioning, that in the case of aryl-substituted ami-
nopyrazoles, the reaction proceeds regiospecifically to
Synthesis 2002, No. 1, 28 12 2001. Article Identifier:
1437-210X,E;2002,0,01,0133,0137,ftx,en;Z10101SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

134
A. L. Krasovsky et al.
PAPER
form compounds 4d–m as the only regioisomer. Howev- their specificificity in anxiolytic activity, being devoid of
er, 5-alkyl-3-aminopyrazoles under these conditions gave analgesic, anticonvulsant, or muscle-relaxant properties
mixtures of the regioisomers 4a–c and 5a–c. Neverthe- common to benzodiazepines.23 Also they could be used in
less, we succeded in providing regioselective formation of cross-coupling reactions to open up the possibility for the
7-CF3 pyrazolopyrimidines of the more sterically hin- synthesis of analogues (3-position modification). Electro-
dered sulfone 1a with 5-alkyl-3-aminopyrazoles at room philic substitution of pyrazolopyrimidines are well
temperature leading to regioselective formation of the 7- known,12,15 but the treatment of these rings with iodine
CF3 substituted products. The worst ratio in the reaction monochloride afforded the corresponding 3-iodopyrazo-
with 2-amino-5-methylpyrazole was 100:3 and the pure 7- lo[1,5-a]pyrimidines in low yield.12 Thus, we initially de-
CF3 substituted isomer, can be easily obtained by recrys- veloped a mild and efficient method for the synthesis of 3-
tallization from benzene (Table 1).
amino-4-iodopyrazoles, by treatment of parent aminopy-
razoles with iodine/potassium carbonate in water at room
temperature (Scheme 3). Under these reaction conditions
a model pyrazole was iodinated in 76% yield.
Scheme 2
Scheme 3
Iodopyrazolopyrimidines are valuable compounds from
biological and pharmaceutical points of view,12,23 due to
Surprisingly, in the reaction of sulfones 1a,b with 5-(4-
bromophenyl)-4-iodo-1H-pyrazol-3-amine in acetic acid
Table 1 Yields and Regioisomeric Ratio of Cycloadducts 4 and 5
R’
R’’
Entry
Method
from 1a
from 1b
4:5 a
100:35
100:20
100:28
100:15
100:14
100:2
100:0
100:0
100:0
-
4:5 a
Yield, %
86
Yield, %
CH3
cy-Pr
t-Bu
C6H5
H
a
b
c
A
B
A
B
A
B
A
B
A
A
A
A
A
A
A
A
A
B
100 :15
100 :3
100:11
100:1
100;5
100:0
100;0
100:0
100;0
100:0
100:0
100:0
100:0
100:0
100:0
100:0
100:9
100:0
80
76
82
78
84
83
90
86
92
-
84
H
88
80
H
94
92
H
d
94
90
4-BrC6H4
2,4-diMeC6H3
4-MeC6H4
2-ClC6H4
4-MeOC6H4
4-NO2C6H4
H
H
e
f
95
H
92
H
g
h
i
92
-
-
H
92
-
-
H
92
-
-
H
j
89
-
-
C6H5
k
l
93
100/0
-
88
-
H
4-ClC6H4
2-MeC6H4
93
H
m
90
100/21
-
91
-
92
a Structure of products and ratios were determined by 1H NMR.
Synthesis 2002, No. 1, 133–137 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Efficient Syntheses of New CF3-containing Diazolopyrimidines
135
4-(Methylsulfonyl)-2-(trifluoromethyl)-1,2,3,4-tetrahydropyri-
mido[1,2-a]benz-imidazol-2-ol (3)
To a solution of vinylsulfone 1b (1 mmol) in CH3CN (7 mL) 1H-
benzimidazol-2-amine (1 mmol) was added. The mixture was
stirred 12 h at r.t. The precipitate was filtered off, washed with
CH3CN (2 3 mL) and dried in the air.
under reflux only iodine free pyrazolopyrimidine 4e was
obtained in good yield instead of the expected product 4n.
At room temperature in the presence of sodium acetate the
formation of a mixture of 4n and 4e was observed. Under
neutral conditions - in water - the corresponding iodine
product was successfully prepared in good yields
(Scheme 4). This is due to the electrophilic substitution of
iodine by hydrogen under acidic conditions.
Preparation of 2 from 3
4-(Methylsulfonyl)-2-(trifluoromethyl)-1,2,3,4-tetrahydropyrimi-
do[1,2-a]benz-imidazol-2-ol (3) (1 mmol) was dissolved in glacial
HOAc (10 mL). The mixture was stirred for 1 h under reflux. The
solvent was evaporated under reduced pressure. The residue was
chromatographed with CH2Cl2.
(Trifluoromethyl)pyrazolo[1,5-a]pyrimidine 4; General
Procedure
To a solution of vinylsulfone 1a,b (1 mmol) in HOAc (20 mL) the
corresponding 1H-pyrazol-3-amine (1 mmol) was added. The mix-
ture was stirred for an appropriate time under reflux (method A) or
at r.t. (method B). The solvent was evaporated under reduced pres-
sure and the residue chromatographed with CH2Cl2.
Scheme 4
5-(4-Bromophenyl)-4-iodo-1H-pyrazol-3-amine
To a solution of 3-amino-5-(4-bromophenyl)-1H-pyrazol (1 mmol)
in H2O (20 mL) iodine (1.1 mmol) and K2CO3 (1.1 equiv) were add-
ed. The mixture was stirred at room temperature for 24 h. The
brown precipitate formed was filtered off, washed with H2O (2 20
mL), dried on air and the residue was chromatographed with
CH2Cl2.
The reaction was found to be equivually facile for the syn-
thesis of 2-, 3- and 2,3-disubstituted-7-(trifluorometh-
yl)pyrazolo[1,5-a]pyrimidine, when the corresponding
aminopyrazoles were reacted with sulfones 1a,b under
analogous reaction conditions.
All results are in good agreement with literature data1,17
that is, the ring nitrogen in aminopyrazoles is the most ba-
sic and the most hindered site in the molecule. Thus, the
endocyclic nitrogen of azoles attacks the less hindered and
most electrophilic carbonyl group of sulfones 1a,b.
2-(4-Bromophenyl)-3-iodo-5-(trifluoromethyl)pyrazolo[1,5-
a]pyrimidine (4n)
To a solution of vinylsulfone 1a,b (1 mmol) in H2O (20 mL) 3-ami-
no-5-(4-bromophenyl)-4-iodo-1H-pyrazol (1 mmol) was added.
The mixture was stirred under reflux 24 h. The precipitate formed
was filtered off, dried on air, and chromatographed with CH2Cl2.
In summary, sulfones 1a,b were shown to be excellent
1,3-bielectrophiles in their reaction with benzaminoimi-
dazole and aminopyrazoles affording a one-stage synthe-
sis of various diazolopyrimidine derivatives. A novel
method for the preparation of iodine-substituted pyrazol-
opyrimidines for the synthesis of CF3-containing azolopy-
rimidines was elaborated. The advantages of this novel
method are the simple experimental layout, environmen-
tal friendly conditions, reasonable reaction times, re-
giospecific formation of target products and high yields
(Table 2).
Acknowledgement
Financial support from Russian Fundamental Investigation Found-
ation (Grants 00-03-32763a and 00-03-32760) is gratefully ack-
nowledged.
References
(1) Elnagdi, M. N.; Elmoghayar, M. R. H.; Elgemeie, G. E. H.In
Advances in Heterocyclic Chemistry, Vol. 41; Katritzky, A.
R., Ed.; Academic Press: New York, 1987, 320.
(2) (a) Elnagdi, M. N.; Elmoghayar, M. R. H.; Sadek, K. U .In
Advances in Heterocyclic Chemistry, Vol. 48; Katritzky, A.
R., Ed.; Academic Press: New York, 1990, 219.
(b) Elnagdi, M. N.; Taha, N. H.; Abd, E. l. A. l. l. F. M.;
Abdel-Motaleb, R. M.; Mahmoud, F. F. Coll. Czech. Chem.
Commun. 1988, 53, 1089.
(3) Bouillon, J.-P.; Janousek, Z.; Viehe, H. G.; Tinant, P.;
Declercq, J.-P. J. Chem. Soc., Perkin Trans. 1. 1995, 2907.
(4) Kawase, M.; Hirabayashi, M.; Saito, S.; Yamamoto, K.
Tetrahedron Lett. 1999, 40, 2541.
(5) Balicki, R.; Nantka-Namirski, P. Pol. J. Chem. 1980, 54,
2175.
(6) Rempfler, H.; Duerr, D. EP 337944, 1989; Chem. Abstr.,
1990, 112, 139043r.
(7) Rempfler, H.; Duerr, D.; Thummel, R. C. EP 337943, 1989;
Chem. Abstr., 1990, 112, 139044s.
Melting points were determined in sealed capillaries and are uncor-
rected. NMR spectra were recorded on Varian VXR-400 spectrom-
eter with TMS as an internal standard. The IR spectra were obtained
with UR-20 spectrometer as films. Column chromatography was
performed on silica gel (63–200 mesh, Merck). All solvents used
were dried and distilled according to standard procedures. Silica gel
Merck 60 and Merck 60F254 plates were used for conventional and
analytical (TLC) chromatography, respectively.
2-(Trifluoromethyl)pyrimido[1,2-a]benzimidazole (2)
To a solution of vinylsulfone 1a,b (1 mmol) in H2O (20 mL) 1H-
benzimidazol-2-amine (1 mmol) was added. The mixture was
stirred 4 h under reflux. The precipitate was filtered off, washed
with H2O, and the residue was chromatographed with CH2Cl2.
(8) Bajwa, J. S.; Sykes, P. J. J. Chem. Soc. Perkin Trans. 1.
1979, 3085; and references cited therein.
Synthesis 2002, No. 1, 133–137 ISSN 0039-7881 © Thieme Stuttgart · New York

136
A. L. Krasovsky et al.
PAPER
Table 2 Analytical Data for Compounds 2
1H NMR (DMSO-d6/TMS) , J (Hz)a,b,c
5
13C NMR (DMSO-d6/TMS) , J (Hz)a
mp, °C
2: 7.44 (d, 1 H, J = 7.0, CH-3), 7.50 (dd, 1 H, J = 7.1, 8.4, CH-7), 7.62 2: 108.2 111.3, 124.4 (q, J = 286.6, CF3), 125.6, 127.4,
(dd, 1 H, J = 7.1, 8.3, CH-8), 7.92 (d, 1 H, J = 8.3, CH-9) , 8.34 (d, 1 131.6, 133.4, 142.2, 142.4, 147.9, 164.2 (q, J = 40.1, CF3)
H, J = 8.4, CH-6), 9.68 (d, 1 H, J = 7.0, CH-4)
290–292
3: 2.91 (dd, 1 H, J = 7.0, 15.9, CH2), 3.18 (s, 3 H, CH3), 3.22 (br d, 1 3: 28.2, 40.8, 69.3, 79.8 (q, J = 37.3 Hz, C–OH), 113.4,
H, J = 15.9, CH2), 6.03 (br d, 1 H, J = 7.0, CH), 7.45–7.50 (m, 2 H, 114.1, 123.8 (q, J = 385.4, CF3), 126.0, 127.2, 129.6, 129.9,
244–246
Oil
Ar), 7.60–7.64 (m, 1 H, Ar), 7.69–7.73 (m, 1 H, Ar)
147.3
4a: 2.48 (s, 3 H, CH3), 6.62 (s, 1 H, CH-9), 7.19 (d, 1 H, J = 4.1, CH- 4a (major isomer): 14.8, 98.4, 105.5, 120.3 (q, J = 274.7,
6), 8.51 (d, 1 H, J = 4.1, CH-5)
CF3), 134.4 (q, J = 36.4, C-CF3), 136.5, 148.4, 157.5
5a: 2.47 (s, 3 H, CH3), 6.61 (s, 1 H, CH-9), 7.12 (d, 1 H, J = 7.3 Hz,
CH-6), 8.85 (d, 1 H, J = 7.3, CH-7)
4b: 0.90–0.97 (m, 2 H, CH2), 1.06–1.11 (m, 2 H, CH2), 2.14–2.21 (m, 4b (major isomer): 9.9, 10.1, 94.4, 105.2, 119.9 (q, J =
2 H, CH–cyPr), 6.45 (s, 1 H, CH-9), 7.01 (d, 1 H, J = 4.3, CH-6), 8.45 274.7, CF3), 134.3 (q, J = 36.1, C-CF3), 148.3, 151.1, 164.2
(d, 1 H, J = 4.3, CH-5)
72–74
5b: 0.90–0.97 (m, 2 H, CH2), 1.06–1.11 (m, 2 H, CH2), 2.14–2.21 (m,
2 H, CH–cyPr), 6.50 (s, 1 H, CH-9), 6.98 (d, 1 H, J = 7.2, CH-6), 8.68
(d, 1 H, J = 7.2, CH-7)
4c: 1.41 (s, 9 H, 3 CH3), 6.70 (s, 1 H, CH-9), 7.03 (d, 1 H, J = 4.2, 4c (major isomer): 29.7, 32.4, 93.8, 104.6, 119.9 (q, J =
131–133
152–153
CH-6), 8.48 (d, 1 H, J = 4.2, CH-5)
274.1 Hz, CF3), 133.3 (q, J = 36.5 Hz, C–CF3), 147.9, 150.4,
5c: 1.41 (s, 9 H, 3 CH3), 6.75 (s, 1 H, CH-9), 7.00 (d, 1 H, J = 7.1, 169.4
CH-6), 8.82 (d, 1 H, J = 7.1, CH-7)
4d: 7.25 (s, 1 H, CH-9), 7.31 (d, 1 H, J = 4.3 Hz, CH-6), 7.46 (t, 1 H, 4d: 96.2, 108.5, 121.7 (q, J = 274.0, CF3), 128.3, 130.7,
J = 7.2, Ph), 7.52 (t, 2 H, J = 7.2, Ph), 8.04 (d, 2 H, J = 4.3, Ph), 8.61 131.3, 134.0, 138.0 (q, J = 36.8, C-CF3), 150.9, 152.9, 158.6
(d, 1 H, J = 4.3, CH-5)
4e: 7.22 (s, 1 H, CH-9), 7.32 (d, 1 H, J = 4.2, CH-6), 7.64 (d, 2 H, J = 4e: 95.7, 108.1, 121.9 (q, J = 274.1, CF3), 124.0, 128.7,
150–151
108–109
8.4, Ar), 7.92 (d, 2 H, J = 8.4, Ar), 8.61 (d, 1 H, J = 4.2, CH-5)
129.1, 133.0, 136.2 (q, J = 37.0, C-CF3), 150.2, 151.9, 163.7
4f: 2.31 (s, 3 H, CH3), 2.49 (s, 3 H, CH3), 7.01 (s, 1 H, CH-9), 7.08 (d, 4f: 21.3, 21.6, 98.8, 108.0, 121.5 (q, J = 274.0 Hz, CF3),
1 H, J = 7.9, Ar), 7.12 (br. s, 1 H, Ar), 7.24 (d, 1 H, J = 4.3, CH-6), 128.4, 130.6, 131.4, 133.6, 134.6 (q, J = 37.1, C–CF3),
7.56 (d, 1 H, J = 7.9, Ar), 8.56 (d, 1 H, J = 4.3, CH-5)
138.2, 140.9, 150.5, 151.9, 159.3
4g: 2.39 (s, 3 H, CH3), 7.19 (s, 1 H, CH-9), 7.28 (d, 1 H, J = 4.3, CH- 4g: 21.4, 95.8, 108.2, 121.6 (q, J = 274.1, CF3), 128.0, 130.9, 134–136
6), 7.32 (d, 2 H, J = 8.0, Ar), 7.92 (d, 2 H, J = 8.0, Ar), 8.58 (d, 1 H, 131.3, 135.5 (q, J = 36.4, C–CF3), 141.4, 150.8, 152.8, 158.5
J = 4.3, CH-5)
4h: 7.37 (s, 1 H, CH-9), 7.38 (d, 1 H, J = 4.2, CH-6), 7.45 (m, 2 H,
4h: 98.8, 108.2, 120.9 (q, J = 274.1, CF3), 128.2, 131.4,
106–108
Ar), 7.57 (m, 1 H, Ar), 7.92 (m, 1 H, Ar), 8.65 (d, 1 H, J = 4.2, CH-5) 131.5, 132.0, 132.2, 133.3, 134.0 (q, J = 36.7, C–CF3),
150.1, 150.9, 155.1
4i: 3.82 (s, 3 H, CH3), 6.99 (d, 2 H, J = 7.5, Ar), 7.14 (s, 1 H, CH-9), 4i: 56.3, 94.8, 107.9, 116.0, 121.2 (q, J = 274.1 Hz, CF3),
7.29 (d, 1 H, J = 4.3, CH-6), 7.92 (d, 2 H, J = 7.5, Ar), 8.58 (d, 1 H, J 125.8, 129.8, 139.7 (q, J = 36.9 Hz, C–CF3), 150.3, 151.4,
150–152
= 4.3, CH-5)
159.0, 163.0
4j: 7.52 (s, 1 H, CH-9), 7.61 (d, 1 H, J = 5.0 Hz, CH-6), 8.23 (d, 2 H, 4j: 104.4, 108.2, 121.4 (q, J = 274.3, CF3), 129.8, 132.2,
J = 8.5, Ar), 8.29 (d, 2 H, J = 8.5, Ar), 8.90 (d, 1 H, J = 5.0, CH-5) 138.5, 140.7 (q, J = 36.5, C–CF3), 145.9, 151.6, 159.9, 163.4
289-290
158–160
4k: 7.33 (t, 1 H, J = 7.4, Ph), 7.38 (d, 1 H, J = 4.1 Hz, CH-6), 7.48 (t, 4k: 105.7, 108.5, 121.5 (q, J = 274.1, CF3), 126.3, 126.6,
2 H, J = 7.2, Ph), 8.08 (d, 2 H, J = 7.5, Ph), 8.65 (s, 1 H, CH-8), 8.71 129.7, 132.1, 140.0 (q, J = 36.7, C–CF3), 145.3, 151.0, 151.6
(d, 1 H, J = 4.1 Hz, CH-5)
4l: 7.41 (d, 1 H, J = 4.2 Hz, CH-6), 7.48 (d, 2 H, J = 8.4, Ar), 8.09 (d, 4l: 105.0, 108.4, 121.4 (q, J = 274.2, CF3), 128.9, 129.9,
198–200
2 H, J = 8.4, Ar), 8.66 (s, 1 H, CH-8), 8.75 (d, 1 H, J = 4.2, CH-5)
132.0, 135.8, 139.2 (q, J = 37.0, C–CF3), 144.2, 150.4, 156.7
4m: 2.33 (s, 3 H, CH3), 7.26–7.49 (m, 5 H, Ar, CH-6), 8.38 (s, 1 H, 4m (major isomer): 20.9, 108.6, 112.2, 121.0 (q, J = 274.1 101–103
CH-8), 8.65 (d, 1 H, J = 4.3, CH-5) Hz, CF3), 127.4, 129.4, 132.0, 132.5, 132.9, 133.0, 138.0 (q,
5m: 2.33 (s, 3 H, CH3), 7.26–7.49 (m, 5 H, Ar, CH-6), 8.41 (s, 1 H, J = 37.1 Hz, C–CF3), 138.9, 146.8, 150.6
CH-8), 9.07 (d, 1 H, J = 7.3, CH-5)
4n: 7.40 (d, 1 H, J = 4.1, CH-6), 7.65 (d, 2 H, J = 8.5, Ar), 7.93 (d, 2 4n: 62.8, 105.1, 119.9 (q, J = 274.2, CF3), 120.4, 125.7,
138–140
H, J = 8.5, Ar), 8.67 (d, 1 H, J = 4.1, CH-5)
129.0, 133.4, 136.7 (q, J = 36.9, C–CF3), 145.2, 150.4, 156.2
a a–c in CDCl3, d–h, k, m in CD3CN, i, j, l, n in CD3CN–CF3COOH, (95:5).
b Satisfactory microanalyses were obtained: C, 0.28; H, 0.25.
c IR (film, cm–1) for 3: 3240 (br. s, OH), 1381 (s, SO2).
Synthesis 2002, No. 1, 133–137 ISSN 0039-7881 © Thieme Stuttgart · New York

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Efficient Syntheses of New CF3-containing Diazolopyrimidines
137
(9) Reiter, J.; Pongo, L.; Dyortsak, P. Tetrahedron 1987, 43,
(17) Elnagdi, M. H.; Erian, A. W. Bull. Chem. Soc. Jpn. 1990, 63,
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