Alternative routes to the pyrazolo[4,3-e][1,2,4]triazolo-[1,5-c]pyrimidine system

Article abstract of DOI:10.1007/s11178-005-0266-z

Formimidic acid esters derived from 1-substituted 5-aminopyrazole-4- carbonitriles reacted with carboxylic acid hydrazides on heating to give 2,7-disubstituted pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives as a result of double heterocycliza

Full text of DOI:10.1007/s11178-005-0266-z

Russian Journal of Organic Chemistry, Vol. 41, No. 6, 2005, pp. 916–921. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005,
pp. 934–938.
Original Russian Text Copyright © 2005 by Tyurin, Vorob’ev, Minyaeva, Krasnikov, Mezheritskii.
Alternative Routes to the Pyrazolo[4,3-e][1,2,4]triazolo-
[1,5-c]pyrimidine System
R. V. Tyurin, E. V. Vorob’ev, L. G. Minyaeva, V. V. Krasnikov, and V. V. Mezheritskii
Institute of Physical and Organic Chemistry, Rostov State University,
pr. Stachki 194/2, Rostov-on-Don, 344090, Russia
e-mail: mezher@ipoc.rsu.ru
Received July 6, 2004
Abstract—Formimidic acid esters derived from 1-substituted 5-aminopyrazole-4-carbonitriles reacted with
carboxylic acid hydrazides on heating to give 2,7-disubstituted pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine
derivatives as a result of double heterocyclization. The same compounds were obtained by thermal recycliza-
tion of 1-aroyl-2-(1-R-pyrazolo[3,4-d]pyrimidin-4-yl)hydrazines.
It is known that treatment of 5-aminopyrazole-4-
carbonitriles I with ethyl orthoformate gives form-
imidic acid esters II whose reactions with primary
amines are accompanied by heterocyclization to afford
pyrazolo[3,4-d]pyrimidine derivatives [1, 2]. The
products attract interest from the viewpoint of their
subsequent transformations [1–6] and exhibit a broad
spectrum of biological activity [7–11]. We anticipated
[12] that the use of carboxylic acid hydrazides as the
amine component will give rise to cascade hetero-
cyclization II → III → IV → V with formation of
a new heterocyclic system, pyrazolo[4,3-e][1,2,4]tri-
azolo[1,5-c]pyrimidine derivatives V. In fact, form-
imidic acid esters II reacted with hydrazides under
fairly severe conditions (prolonged heating in boiling
bromobenzene) to give the expected compounds V in
about 50% yield (isolated pure products). The pro-
posed transformation sequence (Scheme 1) was con-
firmed experimentally using the reaction of ester IIa
with p-methoxybenzohydrazide as an example. The
reaction was carried out under milder conditions, and
we succeeded in isolating intermediate compounds
IIIa and IVa and hence converting in a stepwise mode
amidrazone IIIa into pyrazolopyrimidine IVa, and the
latter, into the target product Va.
peak M1+· (m/z 284) which underwent cascade hetero-
cyclization with elimination of water molecule, result-
ing in formation of ion M2+· (m/z 266) corresponding to
the molecular ion of pyrazolotriazolopyrimidine Va.
Heating of amidrazone IIIa in dimethylformamide
for a short time led to closure of pyrimidine ring to
afford 4-iminopyrazolopyrimidine IVa. The IR spec-
trum of IVa lacked C≡N absorption, the carbonyl
stretching vibration frequency decreased to 1650 cm–1,
and the NH absorption pattern differed from that
observed for IIIa (3115, 3200 cm–1). Compounds IIIa
and IVa are very poorly soluble in organic solvents,
1
and we failed to record their H NMR spectra. Never-
theless, the above IR data are consistent with the
assumed structures.
Dehydration of iminopyrimidine IVa with closure
of triazole ring (IVa → Va) was effected by prolonged
heating in boiling bromobenzene. In the IR spectrum
of compound Va dispersed in mineral oil we observed
a fairly strong absorption band at 1650 cm–1, whose
origin is difficult to interpret. The structure of Va was
1
confirmed by other spectral methods. Its H NMR
spectrum contained a three-proton singlet due to the
methoxy group (δ 3.85 ppm), two two-proton doublet
from the aromatic protons of the 2-p-methoxyphenyl
substituent (δ 7.1 and 8.2 ppm), a sharp singlet at
δ 9.5 ppm due to 5-H (C2 in the pyrimidine ring), and
two broadened signals from protons in the pyrazole
ring (δ 8.6 and 14.4 ppm); broadening of the latter
signals is likely to result from prototropic transforma-
tions in the pyrazole ring. The most abundant peak in
the mass spectrum of Va was that of the molecular ion
Amidrazone IIIa was readily obtained by heating
imidic ester IIa with p-methoxybenzohydrazide in
alcohol. The IR spectrum of IIIa contained absorption
bands due to stretching vibrations of the cyano
(2200 cm–1), carbonyl (1675 cm–1), amidine (1650 cm–1),
and imino groups (3060, 3330, 3355 cm–1). Compound
IIIa showed in the mass spectrum the molecular ion
1070-4280/05/4106-0916 © 2005 Pleiades Publishing, Inc.

ALTERNATIVE ROUTES TO THE PYRAZOLO[4,3-e][1,2,4]TRIAZOLO-...
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Scheme 1.
CN
CN
CN
CH(OEt)3
R'CONHNH2
NHNHCOR'
N
N
N
NH2
N
CHOEt
N
N
R
N
R
N
R
Ia–Ii
IIa, IIb, IId, IIf, IIh
IIIa
R'
N
NH
N
NHCOR'
N
N
N
N
–H2O
N
N
N
N
R
R
IVa
Va–Vi
Cl
N
NHNHCOR'
IVa
(1) HCONH2
(2) SOCl2
N
R'CONHNH2
N
N
N
N
Ia–Ii
N
N
R'
N
N
N
R
R
N
N
VIb–VIi
VIIb–VIIi
N
R
VIII
R = H, R' = 4-MeOC6H4 (a); R = Me, R' = Ph (b), 4-MeOC6H4 (c); R = PhCH2, R' = Ph (d), 4-MeOC6H4 (e); R = Ph,
R' = 4-MeOC6H4 (f), 4-ClC6H4OCH2 (g); R = 4-MeC6H4, R' = Ph (h), 4-MeC6H4 (i).
M2+· with m/z 266; its subsequent fragmentation gives
ions F1 (m/z 251) and F2 (m/z 223) via successive eli-
mination of H3C· radical and CO molecule (Scheme 2).
The spectral parameters of the other pyrazolo[4,3-e]-
[1,2,4]triazolo[1,5-c]pyrimidines Vb–Vi did not con-
tradict the assumed structure.
xylic acid hydrazides. As a result, we isolated pre-
viously unknown 4-acylhydrazinopyrazolo[3,4-d]pyri-
midines VII.
1
According to the H NMR data, compounds VII in
DMSO-d6 at 20°C exist in the amino rather than imino
form: the spectra contained two broadened one-proton
doublets in the region δ 9.5–11.0 ppm. In the spectrum
recorded at elevated temperature, considerable broad-
ening of signals from protons of the 4-hydrazino sub-
stituent was observed, and the patterns in the regions
corresponding to aromatic protons and functional
groups became simpler due to rupture of intramolec-
We also made an attempt to synthesize pyrazolo-
[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines VIII which
are isomeric to V; they differ from V by the mode of
junction of the triazole and pyrimidine rings. For this
purpose, chloro derivatives VI prepared by the known
scheme [3, 4] were brought into reaction with carbo-
Scheme 2.
O
N
N
N
N
M2+
N
N
·
·
–H3C
–CO
N
N
N
N
N
N
H
H
Va, m/z 266
F1, m/z 251
F2, m/z 223
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 6 2005

TYURIN et al.
918
Scheme 3.
O
N
R
O
R
N
N
NH2
N
NHNHCOR
N
H
H
R
N
N
N
N
OH
NH2
N
N
N
A
B
C
D
R
R
N
N
N
O
N
NH2
N
N
N
E
F
ular hydrogen bonds and acceleration of tautomeric
and exchange processes.
regarded as the reverse to the known base-catalyzed
Dimroth rearrangement [1]. Presumably, the rearrange-
ment VII → V includes consecutive migration of
proton and the acyl group (B → C) in the amidrazone
fragment. Cleavage of the N–N bond in 1-acyl-1-
hetarylhydrazine C gives intimate ion pair D consist-
ing of resonance-stabilized anion and amino cation,
which is then converted into N-amino derivative E.
The mechanism of the latter stage is analogous to
N-amination of nitrogen-containing heterocycles with
hydroxylamine–sulfuric acid [13]. Dehydration of
intermediate E gives final product F (Scheme 2).
Dehydration of hydrazides VII occurred under very
severe conditions, on heating above their melting
1
points. The H NMR spectra of the dehydration prod-
ucts were fully identical to those of compounds V.
Structure V (rather than VIII) was proved by the X-ray
diffraction data for the product obtained from hydra-
zide VIIg (see figure). The geometric parameters of
molecule Vg indicate essential conjugation in the
tricyclic system. However, all formally double bonds
(C2–N2 1.318, C3–N3 1.322, C5–N5 1.324, C7–N4
1.301 Å) are slightly shorter than formally single
bonds (C2–N3 1.360, C3–N2 1.375, C6–N4 1.362, C6–N6
1.361, C7–N2 1.375 Å). The tricyclic system is planar,
the C14–C19 benzene ring is turned through a dihedral
angle of 34.86(4)°, the O1 atom deviates from the
plane by 0.40 Å, and the C8–C13 is turned through
an angle of 20.57(5)° with respect to the plane of the
fused heterocyclic skeleton.
EXPERIMENTAL
The IR spectra were recorded on a Specord 71IR
spectrometer from samples dispersed in mineral oil.
1
The H NMR spectra were measured on a Unity-300
instrument (300 MHz) from solutions in DMSO-d6
using HMDS as internal reference. The mass spectra
(electron impact, 70 eV) were obtained on a Kratos
mass spectrometer with direct sample admission into
the ion source (control voltage 1.75 kV).
Thus the observed heterocyclization of hydrazides
VII is accompanied by rearrangement which can be
C9
C18
C7
C10
C11
C17
C16
C19
C14
N4
N2
C3
N1
C2
O1
C1
Cl1
C8
C13
C6
N6
C15
C4
C12
N3
N5
C5
Structure of the molecule of 2-(4-chlorophenoxy)-7-phenyl-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (Vg) according to the
X-ray diffraction data.
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ALTERNATIVE ROUTES TO THE PYRAZOLO[4,3-e][1,2,4]TRIAZOLO-...
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X-Ray analysis of compound Vg was performed on
a Bruker SMART CCD area detector at 120 K (λMoKα
irradiation, 2θmax = 58.00°). Total of 12416 reflections
were measured from a 0.50×0.40×0.07-mm single
crystal (colorless plates); C19H13ClN6O (M 376.80).
Monoclinic crystals with the following unit cell pa-
rameters (120 K): a = 19.047(7), b = 12.206(5), c =
7.226(3) Å; β = 93.292(8)°; V = 1677(1) Å3; space
group P21/c; Z = 4, dcalc = 1.492 g/cm3. Averaging of
equivalent reflections gave 4436 independent reflec-
tions (Rint = 0.0531) which were used in the structure
solution and refinement. Absorption (μ = 0.252 mm–1)
was not taken into account, and the parameters Tmax
and Tmin (0.862 and 0.123, respectively) were calculat-
ed using SADABS program. The structure was solved
by the direct method. All non-hydrogen atoms were
localized from the difference synthesis of electron
density, and their positions were refined with respect to
F2hkl in anisotropic approximation. All hydrogen atoms
were localized from the geometry considerations and
were taken into account in the refinement using the
rider model with U(H) = 1.2U(C), where U(C) is the
equivalent temperature factor of the carbon atom to
which the corresponding hydrogen atom is attached.
The final divergence factors were R1 = 0.0576 [calcu-
lated with respect to Fhkl from 3549 reflections with
I > 2σ(I)] and wR2 = 0.1693 (calculated with respect
to F2hkl from all 4436 reflections); GOOF = 1.046;
244 refined parameters. All calculations were perform-
ed using SHELXTL PLUS 5 software package [14].
N-(4-Imino-4,5-dihydro-1H-pyrazolo[3,4-d]pyri-
midin-5-yl)-p-methoxybenzamide (IVa). A suspen-
sion of 60 mg (0.21 mmol) of compound IIIa in 2 ml
of DMF was heated to the boiling point. The mixture
became homogeneous, and, after 10 min, a solid pre-
cipitated. The product was filtered off and washed with
hexane. Yield 50 mg (0.17 mmol, 92%), mp 345°C.
IR spectrum, ν, cm–1: 3200, 3115, 1650. Found, %:
C 55.12; H 4.35; N 29.71. C13H12N6O2. Calculated, %:
C 54.92; H 4.23; N 29.58.
2-(4-Methoxyphenyl)-7H-pyrazolo[4,3-e]tri-
azolo[1,5-c]pyrimidine (Va). A suspension of 100 mg
(0.35 mol) of compound IVa in 2 ml of bromobenzene
was heated for 10 h under reflux. The mixture was
cooled, and the colorless precipitate was filtered off.
Yield 60 mg (0.225 mmol, 64%), mp 274–275°C. IR
1
spectrum, ν, cm–1: 3167, 3100, 1650. H NMR spec-
trum, δ, ppm: 3.85 s (3H), 7.1 d (2H), 8.2 d (2H),
8.6 br.s (1H), 14.4 br.s (1H). Found, %: C 58.78;
H 3.83; N 31.46. m/z 266 [M]+. C13H10N6O. Calcu-
lated, %: C 58.65; H 3.76; N 31.58.
2,7-Disubstituted 7H-pyrazolo[4,3-e][1,2,4]tri-
azolo[1,5-c]pyrimidines Vb–Vi. a. A mixture of equi-
molar amounts of compound IIb, IId, or IIh and the
corresponding carboxylic acid hydrazide in bromoben-
zene was heated for 5–10 h at the boiling point. The
mixture was cooled, and the precipitate was filtered off
and recrystallized from DMF.
b. Pyrazolo[3,4-d]pyrimidine VIIb–VIIi was heat-
ed at the meting point until water vapor no longer
evolved. After cooling, the product solidified and was
recrystallized from DMF.
Initial 5-aminopyrazole-4-carbonitriles I were syn-
thesized by reaction of ethoxymethylenemalonodi-
nitrile with hydrazine hydrate or the corresponding
monosubstituted hydrazines according to the procedure
reported in [4]. Compounds I were converted into
formimidic acid esters II by the action of triethyl
orthoformate as described in [2]. Chloropyrazolo-
pyrimidines VI were prepared by the procedure
described in [3, 4].
7-Methyl-2-phenyl-7H-pyrazolo[4,3-e][1,2,4]tri-
azolo[1,5-c]pyrimidine (Vb). Yield 45 (a), 75% (b),
1
mp 245–247°C. H NMR spectrum, δ, ppm: 4.2 s (3H),
7.5–8.3 m (5H), 8.4 s (1H), 9.1 s (1H). Found, %:
C 62.3; H 4.0; N 33.75. C13H10N6. Calculated, %:
C 62.4; H 4.0; N 33.6.
2-(4-Methoxyphenyl)-7-methyl-7H-pyrazolo-
[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (Vc). Yield 39
(a), 65% (b), mp 241–242°C. H NMR spectrum, δ,
ppm: 3.9 s (3H), 4.2 s (3H), 7.0–8.0 m (4H), 8.4 s
(1H), 9.1 s (1H). Found, %: C 60.3; H 4.1; N 29.9.
C14H12N6O. Calculated, %: C 60.04; H 4.3; N 30.0.
N'-(4-Cyano-1H-pyrazol-5-yliminomethyl)-4-
methoxybenzohydrazide (IIIa). A solution of 83 mg
(0.5 mmol) of p-methoxybenzohydrazide in 1 ml of
ethanol was added to a solution of 82 mg (0.5 mmol)
of ester IIa in 2 ml of ethanol. The mixture was kept
for 1 h at room temperature, and the precipitate was
filtered off and washed with alcohol and water. Yield
60 mg (0.21 mmol, 42.3%), mp 304–306°C. IR spec-
trum, ν, cm–1: 3555, 3330, 3060, 2200, 1673, 1650.
Found, %: C 54.71; H 4.35; N 29.63. m/z 284 [M]+.
C13H12N6O2. Calculated, %: C 54.92; H 4.23; N 29.58.
M 284.
1
7-Benzyl-2-phenyl-7H-pyrazolo[4,3-e][1,2,4]tri-
azolo[1,5-c]pyrimidine (Vd). Yield 42 (a), 65% (b),
1
mp 276–278°C. H NMR spectrum, δ, ppm: 5.7 s (2H),
7.3–8.3 m (10H), 8.4 s (1H), 9.1 s (1H). Found, %:
C 69.5; H 4.15; N 25.8. C19H14N6. Calculated, %:
C 69.944; H 4.3; N 25.77.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 6 2005

TYURIN et al.
920
(1H). Found, %: C 56.48; H 4.91; N 28.31.
C14H14N6O2. Calculated, %: C 56.37; H 4.70; N 28.19.
7-Benzyl-(4-methoxyphenyl)-7H-pyrazolo[4,3-e]-
[1,2,4]triazolo[1,5-c]pyrimidine (Ve). Yield 54 (a),
1
76% (b), mp 207–208°C. H NMR spectrum, δ, ppm:
N'-(1-Benzyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl)-
benzohydrazide (VIId). Yield 73%, mp 229–230°C.
1H NMR spectrum, δ, ppm: 5.5 s (2H), 7.2–8.0 m
(10H), 8.12 s (1H), 8.38 s (1H), 11.5 d (1H), 12.5 br.s
(1H). Found, %: C 66.41; H 4.72; N 24.36.
C19H16N6O. Calculated, %: C 66.28; H 4.65; N 24.42.
3.9 s (3H), 5.7 s (2H), 7.0–7.4 m (9H), 8.4 s (1H), 9.2 s
(1H). Found, %: C 67.5; H 4.2; N 23.59. C20H16N6O.
Calculated, %: C 67.42; H 4.49; N 23.6.
2-(4-Methoxyphenyl)-7-phenyl-7H-pyrazolo-
[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (Vf). Yield 43
1
(a), 72% (b), mp 232–233°C. H NMR spectrum, δ,
N'-(1-Benzyl-1H-pyrazolo[3,4-d]pyrimidin-
4-yl)-p-methoxybenzohydrazide (VIIe). Yield 78%,
mp 216–217°C. 1H NMR spectrum, δ, ppm: 3.8 s (3H),
5.6 d (2H), 7.1–8.5 m (12H), 11.1 s (1H). Found, %:
C 64.53; H 4.68; N 22.72. C20H18N6O2. Calculated, %:
C 64.17; H 4.81; N 22.46.
ppm: 7.4–8.4 m (12H), 8.6 s (1H), 9.2 s (1H). Found,
%: C 66.5; H 4.1; N 24.6. C19H14N6O. Calculated, %:
C 66.66; H 4.03; N 24.56.0.
2-(4-Chlorophenoxy)-7-phenyl-7H-pyrazolo-
[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (Vg). Yield 58
1
(a), 70% (b), mp 188–190°C. H NMR spectrum, δ,
N'-(1-Phenyl-1H-pyrazolo[3,4-d]pyrimidin-
4-yl)-p-methoxybenzohydrazide (VIIf). Yield 69%,
mp 231–233°C. 1H NMR spectrum, δ, ppm: 3.9 s (3H),
7.0–8.6 m (11H), 9.8–11.6 br.m (2H). Found, %:
C 63.27; H 4.51; N 23.15. C19H16N6O2. Calculated, %:
C 63.34; H 4.45; N 23.33. M 360.
ppm: 5.4 s (2H), 7.0–8.2 m (9H), 8.5 s (1H), 9.2 s
(1H). Found, %: C 60.72; H 3.56; Cl 9.62; N 22.46.
C19H13ClN6O. Calculated, %: C 60.56; H 3.45; Cl 9.43;
N 22.31.
2-Phenyl-7-p-tolyl-7H-pyrazolo[4,3-e][1,2,4]tri-
azolo[1,5-c]pyrimidine (Vh). Yield 38 (a), 66% (b),
2-(4-Chlorophenoxy)-N'-(1-phenyl-1H-pyrazolo-
[3,4-d]pyrimidin-4-yl)acetohydrazide (VIIg). Yield
86%, mp 217–218°C. 1H NMR spectrum, δ, ppm: 5.5 s
(2H), 6.8–8.5 m (11H), 11.5–11.7 br.d (2H). Found, %:
C 60.72; H 3.56; Cl 9.62; N 22.46. C19H13ClN6O. Cal-
culated, %: C 60.56; H 3.45; Cl 9.43; N 22.31.
1
mp 282°C. H NMR spectrum, δ, ppm: 2.4 s (3H), 7.4–
8.4 m (9H), 8.6 s (1H), 9.2 s (1H). Found, %: C 70.15;
H 4.16; N 25.91. C19H14N6. Calculated, %: C 69.94;
H 4.29; N 25.77.
2,7-Di-p-tolyl-7H-pyrazolo[4,3-e][1,2,4]triazolo-
[1,5-c]pyrimidine (Vi). Yield 56 (a), 71% (b),
N'-(1-p-Tolyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl]-
benzohydrazide (VIIh). Yield 88.7%, mp 262–263°C.
1H NMR spectrum, δ, ppm: 2.5 s (3H), 7.2–8.2 m
(11H), 10.0–11.1 m (2H). Found, %: C 66.41; H 4.70;
N 24.65. C19H16N6O. Calculated, %: C 66.28; H 4.65;
N 24.42. M 344.
1
mp 310°C. H NMR spectrum, δ, ppm: 2.4 s (6H), 7.3–
8.2 m (8H), 8.6 s (1H), 9.2 s (1H). Found, %: C 70.72;
H 4.83; N 24.93. C20H16N6. Calculated, %: C 70.59;
H 4.71; N 24.71.
Compounds VIIb–VIIi (general procedure). A sus-
pension of equimolar amounts of compound VI and
the corresponding carboxylic acid hydrazide in alcohol
was heated for 0.5–1 h under reflux. The mixture grad-
ually became homogeneous, and then a solid precip-
itated. The mixture was cooled, and the precipitate was
filtered off, washed with alcohol and water, and recrys-
tallized from DMF.
4-Methyl-N'-(1-p-tolyl-1H-pyrazolo[3,4-d]pyri-
midin-4-yl)benzohydrazide (VIIi). Yield 89.5%,
1
mp 273–274°C. H NMR spectrum, δ, ppm: 2.4 s
(6H), 7.3–8.4 m (10H), 9.8–10.9 m (2H). Found, %:
C 67.00; H 5.23; N 23.61. C20H18N6O. Calculated, %:
C 67.04; H 5.03; N 24.46.
REFERENCES
N'-(1-Methyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl)-
benzohydrazide (VIIb). Yield 69%, mp 244–245°C.
1H NMR spectrum, δ, ppm: 3.95 s (3H), 7.4–8.2 m
(6H), 9.8–11.0 br.m (2H). Found, %: C 58.42; H 4.54;
N 31.26. C13H12N6O. Calculated, %: C 58.21; H 4.48;
N 31.34.
1. Taylor, E.C. and McKillop, A., Advances in Organic
Chemistry, New York: Wiley, 1970, vol. 7.
2. Taylor, E.C. and Loeffler, R.K., J. Am. Chem. Soc., 1960,
vol. 82, p. 3147.
3. Robins, R.K., J. Am. Chem. Soc., 1956, vol. 78, p. 784.
4. Cheng, C.C. and Robins, R.K., J. Org. Chem., 1956,
vol. 21, p. 1240.
5. Cheng, C.C. and Robins, R.K., J. Org. Chem., 1958,
vol. 23, p. 191.
N'-(1-Methyl-1H-pyrazolo[3,4-d]pyrimidin-
4-yl)-p-methoxybenzohydrazide (VIIc). Yield 78%,
mp 226–228°C. 1H NMR spectrum, δ, ppm: 3.8 s (3H),
3.9 s (3H), 7–8.5 m (6H), 11–11.2 d (1H), 12.2 br.s
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921
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