Pyrazole-3(5)-diazonium salts in the synthesis of novel pyrazolo[5, 1-c][1, 2, 4]triazines

Article abstract of DOI:10.1007/s11172-009-0132-1

Coupling of pyrazole-3(5)-diazonium salts with cyclic 1, 3-dicarbonyl (active methylene) compounds followed by cyclocondensation of the resulting hetarylhydrazones gave novel pyrazolo[5, 1-c][1, 2, 4]triazines.

Full text of DOI:10.1007/s11172-009-0132-1

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 1034—1040, May, 2009
1034
Pyrazoleꢀ3(5)ꢀdiazonium salts
in the synthesis of novel pyrazolo[5,1ꢀc][1,2,4]triazines
Kh. S. Shikhaliev, V. V. Didenko, V. A. Voronkova, and D. V. Kryl´skii
Department of Chemistry, Voronezh State University,
1 Universitetskaya pl., 394006 Voronezh, Russian Federation.
Fax: +7 (473 2) 55 6890. Eꢀmail: chocd261@chem.vsu.ru
Coupling of pyrazoleꢀ3(5)ꢀdiazonium salts with cyclic 1,3ꢀdicarbonyl (active methylene)
compounds followed by cyclocondensation of the resulting hetarylhydrazones gave novel
pyrazolo[5,1ꢀc][1,2,4]triazines.
Key words: 3ꢀRꢀ4ꢀarylꢀ1Hꢀ5ꢀaminopyrazoles, pyrazolediazonium salts, cyclohexaneꢀ
1,3ꢀdione, 4ꢀhydroxyꢀ6ꢀmethylꢀ2ꢀpyrone, barbituric acid, hydrazones, pyrazolo[5,1ꢀc][1,2,4]ꢀ
triazines, diazotization, azo coupling, cyclocondensation.
The wide scope of the synthesis of fused nitrogenꢀ
containing heterocycles based on αꢀaminopyrazoles is
known to be associated with the binucleophilic nature of
the latter. Twoꢀ and threeꢀcomponent cyclization reacꢀ
tions in the series of 3(5)ꢀaminopyrazoles 1 involve the
endocyclic N atom and the exocyclic amino group.1,2
The ability to form diazonium salts 2 (Scheme 1) subꢀ
stantially extends the application area of these compounds.
synthesis of azolo[5,1ꢀc][1,2,4]triazines, structural
analogs of natural purine bases.
However, the use of cyclic βꢀdiketones and βꢀoxo
esters as azo components has not been documented,
although they have considerable synthetic potential.
Proceeding further in our investigations,6,7 we studied
azo coupling reactions of diazonium salts 2a—q with
cyclohexaneꢀ1,3ꢀdione and its derivatives 3, indaneꢀ
1,3ꢀdione (4), 4ꢀhydroxyꢀ6ꢀmethylꢀ2ꢀpyrone (5), and
barbituric acids 6 (R = H and Me) for design of pyrazoloꢀ
[5,1ꢀc][1,2,4]triazines containing various cyclic fragments.
Scheme 1
1, 2
R
Ar
1, 2
R
Ar
a
b
c
d
e
f
g
h
i
Me
Et
MeOCH2
Me
Ph
Ph
Ph
pꢀFC6H4
pꢀFC6H4
pꢀFC6H4
pꢀClC6H4
pꢀClC6H4
pꢀClC6H4
j
k
l
m
n
o
p
q
Me
Et
MeOCH2
Me
Et
Me
Et
Me
mꢀClC6H4
mꢀClC6H4
mꢀClC6H4
pꢀBrC6H4
3: R´ = R″ = H; R´ = Me, R″ = H; R´ = R″ = Me;
R´ = Ph, pꢀMeOC6H4, oꢀHOC6H4, 2,4ꢀ(MeO)2C6H3, R″ = H
6: R = H, Me
Et
pꢀBrC6H4
MeOCH2
Me
Et
pꢀMeOC6H4
pꢀMeOC6H4
oꢀMeOC6H4
Freshly prepared diazonium salts were added to a
solution of a 1,3ꢀdicarbonyl compound in the presence of
a saturated sodium acetate buffer solution.
MeOCH2
Like aromatic diazonium salts, pyrazoleꢀ3(5)ꢀdiazoꢀ
Reactions of cyclohexaneꢀ1,3ꢀdione, dimedone, and
its analogs 3 with pyrazolediazonium salts are shown in
Scheme 2. The azo coupling gives brightly colored
hydrazones 8. In addition, azo compounds of the types 7 and
7A are known4,8,9 to be intermediates in similar reactions.
nium salts react with active methylene dicarbonyl comꢀ
pounds (e.g., aliphatic βꢀdiketones and βꢀoxo esters) and
active methylene nitriles.3—5 These coupling reactions have
been described in detail and underlie the traditional
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1008—1013, May, 2009.
1066ꢀ5285/09/5805ꢀ1034 © 2009 Springer Science+Business Media, Inc.

Novel pyrazolo[5,1ꢀc][1,2,4]triazines
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1035
Scheme 2
Scheme 3
9
R
R´
R″
Ar
a
b
c
d
e
f
g
h
i
Et
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
Ph
Me
Me
Me
Me
Me
pꢀClꢀC6H4
mꢀClꢀC6H4
oꢀMeOC6H4
pꢀMeOC6H4
pꢀMeOC6H4
Ph
Ph
pꢀBrC6H4
Ph
MeOCH2 Me
MeOCH2 Ph
Me
Et
Ph
j
oꢀHOC6H4
10a—f. Obviously, the dehydrogenation passes through
the formation of enol 9A (Scheme 4).
The presumed structures of products 10 were conꢀ
firmed by mass spectra containing a peak of a characterisꢀ
Scheme 4
The resulting pyrazolylhydrazones undergo intramoꢀ
lecular cyclization even in their attempted purification or
during measurements of their melting points; in some
cases, their intramolecular cyclization occurs spontaneꢀ
ously at 40—50 °C (monitoring by TLC). Because of this,
they cannot be identified by spectroscopic methods. We
tried several preparative methods of heterocyclocondensaꢀ
tion: (1) a roomꢀtemperature reaction in 45% H2SO4,
(2) reflux in glacial acetic acid with anhydrous sodium
acetate, (3) reflux in toluene with water removal (in the
presence of acetic acid), and (4) heating at 130—140 °C
in polyphosphoric acid.
The first approach proved to be most suitable because
of high yields and minor resinification.
The reactions gave 8,9ꢀdihydropyrazolo[5,1ꢀc][1,2,4]ꢀ
benzotriazinꢀ6(7H)ꢀones 9a—j (Scheme 3).
The 1H NMR spectra of the compounds obtained show
signals for the protons of the cyclohexanone ring at δ
2.70—3.70 but contain no signals for the “acidic” protons
(NH and OH).
When refluxed in DMF or DMF—xylene or when
heated in DMSO (in some cases, even during recrystalliꢀ
zation), pyrazolotriazines 9 obtained from cyclohexaneꢀ
1,3ꢀdione and some of its 5ꢀmonosubstituted derivatives
undergo dehydrogenation leading to the fully aromatized
tricyclic system pyrazolo[5,1ꢀc][1,2,4]benzotriazinꢀ6ꢀols
10
R
R´
Ar
a
b
c
d
e
f
Me
MeOCH2
Me
2,4ꢀ(MeO)2C6H3
H
2,4ꢀ(MeO)2C6H3
oꢀHOC6H4
pꢀMeOC6H4
Ph
Ph
Ph
pꢀClC6H4
Ph
Ph
pꢀFC6H4
Me
Me
Me

1036
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Shikhaliev et al.
tic ion with the mass number [M(9) – 2], where M(9) is
the mass number of the corresponding ketone 9.
the target products 6Hꢀindeno[1,2ꢀe]pyrazolo[5,1ꢀc][1,2,4]ꢀ
triazinꢀ6ꢀones 12a,b.
The physicochemical characteristics and mass spectra
of compounds 9a—j, 10a—f, and 12a,b are given in Table 1;
their 1H NMR spectra are presented in Table 2.
A reaction of pyrazolediazonium salt 2a with 4ꢀhydroxyꢀ
6ꢀmethylꢀ2ꢀpyrone (5) occurred somewhat differently.
Cyclocondensation of the resulting hydrazone 13 did not
yield the expected pyrazolotriazine 14. The 1H NMR and
mass spectra of the product, as well as elemental analysis
data, provide evidence for structure 15 (Scheme 6). Obviꢀ
ously, an acidic medium (dilute H2SO4 or glacial acetic
1
The H NMR spectra of compounds 10 show a charꢀ
acteristic set of signals: a broadened signal at δ ~11.50
(aromatic OH group) and multiplets at δ 7.20—7.50 due
to the aromatic protons of the fused benzene ring.
With indaneꢀ1,3ꢀdione (4) as an active methylene
component for azo coupling, the reaction gives the correꢀ
sponding hydrazones 11a,b in a similar way (Scheme 5).
High enolization of this reagent, as in the case of dimedone,
favors not only its easy coupling with diazonium salts but
also cyclocondensation of the reaction intermediates into
Table 1. Yields, melting points, elemental analysis data, and mass spectra of pyrazolo[5,1ꢀc][1,2,4]ꢀ
triazines 9a—j, 10a—f, and 12a,b
Comꢀ Yield* (%)
pound (method of
synthesis)
M.p./°С
Found
Calculated
Molecular
formula
MS**,
m/z
(%)
C
H
N
9a
82 (А),
80 (B),
65 (D)
80 (А),
71 (B)
75 (А)
122—124
71.02
71.23
6.44
6.29
17.57
17.49
C19H20N4O
321/320.4
9b
229—231
197—199
207—209
185—187
238—240
157—159
182—184
248—250
165—167
188—190
170—172
201—203
255—257
207—209
205—207
290—292
>300
63.69
63.44
63.70
63.44
68.09
67.84
68.12
67.84
67.33
67.07
67.30
67.07
72.12
71.86
60.76
60.98
72.09
71.86
69.52
69.89
66.91
66.66
64.27
64.50
72.00
71.73
72.53
72.24
71.56
71.34
73.36
73.07
73.80
73.61
4.80
5.03
4.86
5.03
5.70
5.99
5.72
5.99
5.40
5.63
5.38
5.63
5.03
5.24
4.14
3.95
5.01
5.24
5.00
4.89
4.30
4.61
4.58
4.29
4.16
4.38
4.40
4.74
3.90
4.08
3.60
3.87
3.15
4.32
16.28
16.44
16.29
16.44
16.58
16.66
16.58
16.66
17.28
17.38
17.27
17.38
14.40
14.57
13.03
12.93
14.49
14.57
13.70
13.58
18.16
18.29
12.70
12.54
15.08
15.21
14.59
14.65
15.01
15.13
17.80
17.94
17.07
17.17
C18H17ClN4O
C18H17ClN4O
C19H20N4O2
C19H20N4O2
C18H18N4O2
C18H18N4O2
C23H20N4O2
C22H17BrN4O
C23H20N4O2
C24H20N4O3
C17H14N4O2
341/340.8
341/340.8
336/336.4
336/336.4
323/322.4
323/322.4
384/384.4
433/433.3
384/384.4
412/412.4
306/306.3
9c
9d
68.5 (А),
63(B)
72.5 (А)
9e
9f
69 (А),
48 (B)
63.5 (B)
9g
9h
76 (B)
71 (А)
9i
9j
58 (А),
45.5 (C)
70.5
10a
10b
10c
10d
10e
10f
12a
12b
63
55
62
73
60
C24H19ClN4O3 447/446.9
C22H16N4O2
C23H18N4O2
C22H15FN4O
C19H12N4O
C20H14N4O
369/368.4
382/382.4
370/370.4
312/312.3
326/326.4
73 (А),
65 (B)
79 (А),
75 (B)
* For the recrystallized product.
** Found/calculated.

Novel pyrazolo[5,1ꢀc][1,2,4]triazines
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1037
Scheme 5
molecule gives poorly soluble 7ꢀmethylꢀ4ꢀ(2ꢀoxopropyl)ꢀ
8ꢀphenylpyrazolo[5,1ꢀc][1,2,4]triazineꢀ3ꢀcarboxylic acid (15).
1
The H NMR spectrum of compound 15 shows douꢀ
blets at δ 3.05 and 3.24 for two methylene protons and an
unusual highꢀfield signal (δ 8.28) for the carboxyl proton.
Apparently, this upfield shift can be associated with the
magnetic anisotropy effect of the keto group.
Coupling of diazonium salt 2a with barbituric acids 6
gave brightly colored linear products in high yields
1
(Scheme 7). According to their H NMR spectra, they
exist as azo enols 17a,b rather than hydrazones 16a,b.
A single lowꢀfield signal at δ 14.40—14.60 was assigned8,10
to the NH proton of the pyrazole ring. A signal for the OH
group at δ 3.50—4.00 is greatly broadened because of
proton exchange.
In an attempted synthesis of pyrazolotriazines 18,
we obtained the following results. Heterocyclization
of 1,3ꢀdimethylꢀ5ꢀ[(3ꢀmethylꢀ4ꢀphenylꢀ1Hꢀpyrazolꢀ
5ꢀyl)diazenyl]pyrimidineꢀ2,4,6ꢀtrione (17b) failed under
various conditions. Such a behavior is due to the inertness
of amide carbonyl in cyclocondensation reactions. Howꢀ
ever, heating of azo compound 17a in polyphosphoric
acid (PPA) at 130—140 °C for many hours afforded the
11, 12: R = Me (a), Et (b)
acid with anhydrous sodium acetate) promotes recyclizaꢀ
tion of the lactone ring. Subsequent addition of a water
Table 2. 1H NMR spectra of pyrazolo[5,1ꢀc][1,2,4]triazines 9a—j, 10a—f, and 12a,b
Comꢀ
pound
δ
(J/Hz)
9a
1.18 (s, 6 H, 2 Me); 2.40 (t, 3 H, CH3CH2, J = 7.4); 2.75 (s, 2 H, CH2); 3.05 (q, 2 H, CH3CH2,
J = 7.7); 3.47 (s, 2 H, CH2); 7.44 (t, 1 H, H arom., J = 7.1); 7.58 (t, 2 H, H arom., J = 7.8);
7.88 (d, 2 H, H arom., J = 7.8)
9b
9с
9d
9e
9f
1.25 (s, 6 H, 2 Me); 2.72 (s, 3 H, Me); 2.78, 3.44 (both s, 2 H each, CH2); 7.51, 7.87
(both d, 2 H each, H arom., J = 8.3)
1.25 (s, 6 H, 2 Me); 2.71 (s, 3 H, Me); 2.80, 3.39 (both s, 2 H each, CH2); 7.08 (d, 1 H, H arom.,
J = 8.1); 7.26 (s, 1 H, H arom.); 7.45 (d, 1 H, H arom., J = 8.0); 8.00 (t, 1 H, H arom., J = 7.8)
1.24 (s, 6 H, 2 Me); 2.71 (s, 3 H, Me); 2.84, 3.70 (both s, 2 H each, CH2); 3.80 (s, 3 H, МеО);
7.02—7.17, 7.35—7.52 (both m, 2 H each, H arom.)
1.22 (s, 6 H, 2 Me); 2.70 (s, 3 H, Me); 2.72, 3.77 (both s, 2 H each, CH2); 3.85 (s, 3 H, МеО);
7.09, 7.76 (both d, 2 H each, H arom., J = 8.5)
1.25 (d, 3 H, Me, J = 6.2); 2.58 (d, 2 H, CH2, J = 6.9); 2.69 (s, 3 H, Me); 2.77 (s, 1 H, CH);
3.15, 3.79 (both q, 1 H each, CH, J = 6.7); 3.85 (s, 3 H, МеО); 7.10, 7.77 (both d, 2 H each, H arom., J = 8.5)
1.24 (d, 3 H, Me, J = 6.2); 2.63 (d, 2 H, CH2, J = 6.7); 2.82 (s, 1 H, CH); 3.16 (q, 1 H, CH,
J = 6.7); 3.49 (s, 3 H, MeОСH2); 3.79 (q, 1 H, CH, J = 6.7); 4.76 (s, 2 H, MeОСH2);
7.39—7.58 (m, 3 H, H arom.); 7.95 (d, 2 H, H arom., J = 7.8)
9g
9h
9i
2.83 (m, 1 H, CH); 2.89 (s, 3 H, MeОСH2); 3.34, 4.45 (both d, 2 H each, CH, J = 6.8);
4.73 (s, 2 H, MeОСH2); 7.40—8.00 (m, 10 H, H arom.)
2.69 (s, 3 H, Me); 2.73 (d, 2 H, CH2, J = 6.7); 2.82 (d, 1 H, CH, J = 6.8); 3.15 (q, 1 H, CH, J = 18.0);
3.70 (q, 1 H, CH, J = 18.1); 7.45—7.56 (m, 7 H, H arom.); 7.89 (d, 2 H, H arom., J = 7.3)
1.40 (t, 3 H, CH3CH2, J = 6.5); 2.90 (m, 1 H, CH); 3.09 (q, 2 H, CH3CH2, J = 7.8); 3.66—4.00
(m, 4 H, CH2); 6.80—7.80 (m, 9 H, H arom.); 9.55 (s, 1 H, ОH)
9j
10a
10b
10c
10d
10е
10f
2.68 (s, 3 H, Ме); 3.75, 3.83 (both s, 3 H each, МеО); 6.89—7.82 (m, 10 H, H arom.); 11.60 (br.s, 1 H, ОH)
3.50 (s, 3 H, МеО); 4.75 (s, 2 H, СH2); 7.12—8.01 (m, 8 H, H arom.); 11.49 (br.s, 1 H, ОH)
2.69 (s, 3 H, Ме); 3.77, 3.85 (both s, 3 H each, МеО); 6.78—7.93 (m, 9 H, H arom.); 11.45 (s, 1 H, ОH)
2.71 (s, 3 H, Ме); 6.76—7.82 (m, 11 H, H arom.); 9.52 (s, 1 H, C6H4ОH); 11.40 (br.s, 1 H, ОH)
2.40 (s, 3 H, Ме); 3.81 (s, 3 H, МеО); 6.98—7.90 (m, 11 H, H arom.); 11.55 (br.s, 1 H, ОH)
2.70 (s, 3 H, Ме); 7.40–7.85 (m, H arom.); 11.69 (br.s, 1 H, ОH)
12a
12b
2.80 (s, 3 H, Ме); 7.48—8.36 (m, 9 H, H arom.)
1.34 (t, 3 H, CH3CH2, J = 7.5); 2.81 (q, 2 H, CH3CH2, J = 7.8); 7.45—8.49 (m, 9 H, H arom.)

1038
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Shikhaliev et al.
Scheme 6
Scheme 7
PPA, 6 h
target product 2ꢀhydroxyꢀ8ꢀmethylꢀ7ꢀphenylꢀ3,4ꢀdihydroꢀ
PPA stands for polyphosphoric acid
16, 17: R = H (a), Me (b)
pyrazolo[5,1ꢀc]pyrimido[4,5ꢀe][1,2,4]triazinꢀ4ꢀone (18a).
1
The H NMR spectrum of pyrazolotriazine 18a conꢀ
The formation of compound 18a is also evident from
mass spectra and elemental analysis data.
Apparently, the cyclization of azo compound 17a is
possible because of the formation of additional lactim
tains no signal for the pyrazole NH fragment but shows a
higherꢀfield signal for an analogous proton in the pyrimiꢀ
dine ring (δ 11.80). A strongly broadened signal for water
at δ 3.30—3.80 suggests the presence of a hydroxy group.
Table 3. Yields, melting points, elemental analysis data, and mass and 1H NMR spectra of compounds 15, 17a,b, and 18a
Comꢀ Yield (%) M.p.
pound (method of /°С
synthesis)
Found
Calculated
Molecular
formula
MS*,
m/z
δ
(%)
(J/Hz)
C
H
N
15
49 (А),
187 62.20 4.45 17.92 C16H14N4O3 310
1.92, 2.59 (both s, 3 H each, Me); 3.05 (d, 1 H, СH2,
43 (B)** (deꢀ 61.93 4.55 18.06
/310.3 J = 8.9); 3.24 (d, 1 H, СH2, J = 8.5); 7.43 (t, 1 H,
H arom., J = 7.0); 7.55 (t, 2 H, H arom., J = 7.8);
7.78 (d, 2 H, H arom., J = 7.7); 8.28 (s, 1 H, СООH)
2.28 (s, 3 H, Me); 7.33 (m, 3 H, H arom.); 7.45 (m,
/312.3 2 H, H arom.); 12.38, 12.55 (both s, 1 H each, NH);
14.49 (s, 1 H, NH)
comp.)
17a
93
>300 54.09 3.60 26.80 C14H12N6O3 312
53.85 3.87 26.91
17b
18a
90
67
>300 56.19 4.90 24.81 C16H16N6O3 340
56.47 4.74 24.69 /340.3 H arom.); 7.47 (m, 2 H, H arom.); 14.45 (s, 1 H, NH)
>300 57.39 3.29 28.42 C14H10N6O2 294 2.70 (s, 3 H, Ме); 7.50 (s, 3 H, H arom.);
57.14 3.43 28.56 /294.3 7.88 (s, 2 H, H arom.); 11.79 (s, 1 H, NH)
2.28, 3.12, 3.20 (all s, 3 H each, Ме); 7.37 (m, 3 H,
* Found/calculated.
** For the product recrystallized from AcOH.

Novel pyrazolo[5,1ꢀc][1,2,4]triazines
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1039
Scheme 8
pleted, the mixture was poured into water (300 mL). The preꢀ
cipitates of products that formed were filtered off, washed with
water to pH 7, and recrystallized from AcOH—toluene (1 : 2).
General procedure B. A mixture of a hydrazone (0.01 mol)
with an equal mass amount of anhydrous sodium acetate was
refluxed in acetic acid (20—30 mL) for 10—15 min. The product
was isolated as described under general procedure A.
General procedure C. A solution of a hydrazone (0.01 mol)
was refluxed with a Dean—Stark trap in a mixture of toluene
(20 mL) and acetic acid (5 mL) until liberation of water ceased.
The mixture was cooled and the product was filtered off and
recrystallized.
tautomer 19, which is precluded for compound 17b
General procedure D. A mixture of equal mass amounts of a
hydrazone and polyphosphoric acid was heated at 130—140 °C
for 5—6 h. The product was isolated as described under general
procedure A.
2ꢀRꢀ3ꢀPhenylꢀ6Hꢀindeno[1,2ꢀe]pyrazolo[5,1ꢀc][1,2,4]triazinꢀ
6ꢀones 12a,b and 7ꢀmethylꢀ4ꢀ(2ꢀoxopropyl)ꢀ8ꢀphenylpyrazoloꢀ
[5,1ꢀc][1,2,4]triazineꢀ3ꢀcarboxylic acid (15) were obtained
according to procedures A and B.
(Scheme 8).
1
The physicochemical characteristics and H NMR
spectra of products 15, 17a,b, and 18a are given in Table 3.
To sum up, our efficient syntheses of novel pyrazoloꢀ
[5,1ꢀc][1,2,4]triazines 9a—j, 10a—f, 12a,b, 15, and 18a
demonstrated that cyclic 1,3ꢀdicarbonyl compounds are
promising azo components in reactions with pyrazoleꢀ
diazonium salts. These reactions under optimized condiꢀ
tions provide a convenient route to pyrazolotriazines fused
with alicyclic, aromatic, and heterocyclic fragments.
2ꢀHydroxyꢀ8ꢀmethylꢀ7ꢀphenylꢀ3,4ꢀdihydropyrazolo[5,1ꢀc]ꢀ
pyrimido[4,5ꢀe][1,2,4]triazinꢀ4ꢀone (18a) was obtained as
described under general procedure D.
2ꢀRꢀ8ꢀR´ꢀ3ꢀArylpyrazolo[5,1ꢀc][1,2,4]benzotriazinꢀ6ꢀols
10a—f (general procedure). A solution of ketone 9 in a small
amount of DMF, DMF—xylene, or DMSO was refluxed for
5—15 min. The reaction mixture was cooled and the crystals
that formed were filtered off, washed with isopropyl alcohol,
and recrystallized from DMF—xylene (1 : 3).
Experimental
The reagents and products were identified, and the reaction
mixtures were qualitatively analyzed during the reactions, by
TLC on Silufol UVꢀ254 plates (Merck). Individual solvents (light
petroleum, chloroform, ethyl acetate, and isopropyl alcohol)
and their mixtures in various ratios were used as eluents; spots
were visualized under UV light or in the iodine vapor. 1H NMR
spectra were recorded on a Bruker ACꢀ300 instrument (300 MHz)
in DMSOꢀd6 with Me4Si as the internal standard. Mass spectra
were recorded on an LKBꢀ9000 spectrometer (direct inlet probe,
ionizing energy 70 eV). Elemental analysis was carried out on a
Carlo Erba NA 1500 instrument.
3ꢀRꢀ4ꢀArylꢀ1Hꢀ5ꢀaminopyrazoles were prepared according
to a known procedure.11 5ꢀMonosubstituted cyclohexaneꢀ
1,3ꢀdiones12 and 4ꢀhydroxyꢀ6ꢀmethylꢀ2ꢀpyrone13 were prepared
as described earlier. The other chemicals and solvents (ACROS
Organics, Aldrich, Lancaster, and VEKTON) were used without
additional purification.
Pyrazolylhydrazones 8, 11a,b, and 13 and azo compounds
17a,b (general procedure). A mixture of 3(5)ꢀaminopyrazole 1
(0.03 mol), water (10 mL), and HCl (d = 1.19 g mL–1; 0.09 mol)
was cooled to 0 °C. Aqueous NaNO2 (0.03 mol) was added with
stirring at such a rate as to prevent a temperature rise. The
mixture was kept at 0 °C for 10 min and added in portions to a
solution of azo components 3, 4, 5, or 6 (0.03 mol), THF (20 mL),
and acetic acid or their mixture with a saturated aqueous soluꢀ
tion of sodium acetate (10 g per every 0.01 mol of compound 1).
The reaction mixture was continuously stirred for several hours.
The precipitate of hydrazone that formed was filtered off, washed
with water and cold isopropyl alcohol, and dried at 20—30 °C.
The yields were 75—92%.
This work was financially supported by the
Russian Foundation for Basic Research (Project
No. 08ꢀ03ꢀ9902 r_ofi).
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Received September 11, 2007;
in revised form September 8, 2008