Benzo[4,5]imidazo[2,1-a]phthalazines: I. Substituted o- nitrophenylhydrazines in the synthesis of phthalazin-1(2H)-ones

Article abstract of DOI:10.1134/S1070428008050175

Efficient cyclization procedure was developed for 2-nitro-, 2,4-dinitro-, 2-nitro-5-chloro-, and 4,5-dichloro-2-nitrophenylhydrazines with 2-acylbenzoic acids by heating the reagents in a mixture of of concentrated sulfuric acid and ethanol. A series of n

Full text of DOI:10.1134/S1070428008050175

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 5, pp. 731−735. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.A. Kuznetsov, K.M. Shubin, A.A. Shchipalkin, F.S. Teplyakov, M.L. Petrov, 2008, published in Zhurnal Organicheskoi Khimii, 2008,
Vol. 44, No. 5, pp. 739−743.
Benzo[4,5]imidazo[2,1-a]phthalazines: I.
Substituted o-Nitrophenylhydrazines in the Synthesis
of Phthalazin-1(2H)-ones
V. A. Kuznetsov, K. M. Shubin, A. A. Shchipalkin, F. S. Teplyakov, and M. L. Petrov
St. Petersburg State Technological Institute, St. Petersburg, 190013 Russia
e-mail: mlpetrov@lti-gti.ru
Received May 18, 2007
Abstract—Efficient cyclization procedure was developed for 2-nitro-, 2,4-dinitro-, 2-nitro-5-chloro-, and 4,5-
dichloro-2-nitrophenylhydrazines with 2-acylbenzoic acids by heating the reagents in a mixture of of concentrated
sulfuric acid and ethanol. A series of new phthalazin-1-ones was obtained with a substituted 2-nitrophenyl
group in the position 2 and various substituents in the position 4.
DOI: 10.1134/S1070428008050175
Benzo[4,5]imidazo[2,1-a]phthalazine has been known
as a heterocyclic system since 1937 [1]. However up till
now only three studies were reported on the synthesis
and characteristics of these compounds. 12-Methyl-
9-trifluoromethyl-12H-benzo-[4,5]imidazo-[2,1-a]-
phthalazin-5-one described in [2] possesses a betaine
structure and therefore its properties are fundamentally
unlike those of the other known members of this series.
from the corresponding o-dinitrobenzenes and hydrazine
hydrate (Scheme 2).
Scheme 1.
R2
R1
R1
N
Only several members of this class compounds were
synthesized in [1], and their preparation was a complex
multistage process that was not of a general character.
An interesting route to 5-arylbenzo[4,5]imidazo-
[2,1-a]phthalazines was tested using o-aminophenol [3].
This procedure is far better than that used in the early
publication, although some limitations arise with respect
to the choice of the introduced substituents. Despite the
found biological activity of the target compounds no
further research was performed.
H2N
N
N
H
NO2
[H]
O
O2N
R2
R1
N
N
O
R2
H2N
Wedevelopedanewmethodofsynthesisforbenzo[4,5]-
imidazo[2,1-a]phthalazines.As already mentioned in the
preliminary communication [4] the procedure made it
possible to prepare a series of new substituted compounds
of this class and led to a simplification of the synthesis.
We plan to treat in detail the synthetic route developed
by us in a series of publications (Scheme 1).
PPA
N
N
R1
N
In this paper we consider the first stage of this
scheme: The synthesis of phthalazin-1-ones by a reac-
tion of o-nitrophenylhydrazines with o-acylbenzoic acids.
2-Nitrophenylhydrazines IIa and IIb were synthesized
R1 = H, 4-NO2, 5-Cl, 4,5-Cl2; R2 = H, Me, Ph, 4-MeC6H4,
4-ClC6H4, 4-EtC6H4, 3,4-Me2C6H3, 3,5-Me2C6H3, 2,5-
Me2C6H3.
731

KUZNETSOV et al.
732
Scheme 2.
of the same reagents mixture in 98% H2SO4 resulted
in a very fast reaction. However under these conditions
also formed an impurity, and the increased temperature
and prolonged process resulted in its fast accumulation
and in reduction in the yield of the target product. The
impurity is likely of acid character, it is insoluble in water
at neutral and acid pH values, but it dissolves at alkaline
pH giving a solution of saturated violet color. To ensure a
more stable and reproducible process we used a mixture of
sulfuric acid with ethanol. Therewith the boiling point of
the mixture can be easily adjusted by the components ratio
within the range 90–160°C. The optimum temperature
range proved to be 100–120°C corresponding to the
boiling point of the mixture 98% sulfuric acid–ethanol,
1:2. The reaction carried out in this mixture resulted in
cyclization of 2-nitro-5-chlorophenylhydrazine (IIa) with
o-acylbenzoic acids in good yields.
H2N
HN
O2N
O2N
Cl
R
Cl
R
H2N NH2
O2N
I , Ib
II , IIb
R = H (a), Cl (b).
Compounds IIa and IIb can be obtained by a direct
nucleophilic substitution of the nitro group in compounds
Ia and Ib with hydrazine hydrate [5, 6]. Under the
conditions we chose the reaction proceeded exclusively
selectively and with a good yield. We also used in the
cyclization commercial nitrophenylhydrazines: 2-nitro-
(IIc) and 2,4-dinitrophenylhydrazine (IId).
The synthesis of phthalazin-1-ones from o-nitro-
phenylhydrazines and o-acylbenzoic acids was only
perfunctory investigated [7–10]. The main difficulty
consists in the high stability against cyclization of the
intermediately formed hydrazone iriginating from the
accumulation of electron-withdrawing substituents in the
aromatic ring of the hydrazine [7].Although several ways
of performing this reaction were previously described the
behavior of 2-nitro-5-chlorophenylhydrazine (IIa) in the
process was not studied.
The efficiency of the developed procedure was tested
on a number of 2-nitrophenylhydrazines. Introducing into
the reaction hydrazines IIb–IId led to the formation in
good yields of the corresponding phthalazin-1(2H)-
ones V.
The composition and structure of newly synthesized
compounds was confirmed by elemental analysis, IR
1
and H NMR spectra. For instance, the IR spectrum
of compound IVa in the region 1670 cm–1 contained
stretching vibrations bands of the carbinyl group in the
position 1 of the phthalazine ring. In the region 1604 cm–1
the band of stretching vibrations of the endocyclic C=N
bond was observed. The symmetric and antisymmetric
stretching vibrations of NO2 group gave rise to bands at
1526 and 1350 cm–1.
It turned out that the reported procedures did not give
plausible results with this compound. In particular, on
boiling the mixture of o-acylbenzoic acid and hydrazine
IIa in ethanol (or in ethanol containing anhydrous HCl)
the phthalazin-1-one formed very slowly. Therewith the
reaction mixture contained a considerable amount of the
intermediately formed hydrazone. In contrast, the heating
Scheme 3.
R3
R2
R3
R3
O
H2N
HN
R2
H
R2
R1
N
R1
COOH
III IIIi
H2SO4, EtOH
_
N
N
N
R1
O2N
O2N
COOH
O
O2N
_
_
_
II IId
IV IVd, V Vd
II, R1 = H, R2 = Cl (a), R1 = R2 = Cl (b), R1 = R2 = H (c), R1 = NO2, R2 = H (d); III, R3 = Me (a), R3 = H (b), R3= Ph (c),
R3 = 4-Me–C6H4 (d), R3 = 4-Cl–C6H4 (e), R3 = 4-Et–C6H4 (f), R3 = 3,4-Me2–C6H3 (g), R3 = 3,5-Me2–C6H3 (h), R3 = 2,5-
Me2–C6H3 (i); IV, R1 = H, R2 = Cl, R3= Me (a), R1 = H, R2 = Cl, R3 = H (b), R1 = H, R2 = Cl, R3= Ph (c), R1 = H, R2 =
Cl, R3 = 4-Me–C6H4 (e), R1 = H, R2 = Cl, R3= 4-Cl–C6H4; (f), R1 = H, R2 = Cl, R3= 4-Et–C6H4 (g), R1 = H, R2 = Cl, R3 =
3,4-Me2–C6H3 (d), R1 = H, R2 = Cl, R3 = 3,5-Me2–C6H3 (h), R1 = H, R2 = Cl, R3= 2,5-Me2–C6H3 (i), V, R1 = R2 = Cl, R3 =
Me (a), R1 = R2 = H, R3 = Me (b), R1 = R2 = H, R3 = 4-Cl-C6H4, R1 = NO2 (c), R2 = H, R3 = Me (d).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 5 2008

BENZO[4,5]IMIDAZO[2,1-a]PHTHALAZINES: I.
733
1
Let us examine a characteristic H NMR spectrun
by an example of 4-(4-methylphenyl)-2-(2-nitro-5-
chlorophenyl)phthalazin-1(2H)-one (IVd) (DMSO-d6).
Alongside a singlet of a methyl group at 2.43 ppm there
are two doublets in the region 7.3–7.6 ppm corresponding
to a para-substituted phenyl in the position 4 of the
phthalazinone. The spin system of the 2-(2-nitrophenyl)
ring gives rise to three well-resolved signals: a doublet
H6’ with a coupling constant of 1.9 Hz at 7.97 ppm,
substituents in the position 2 we demonstrated that the
cyclization in a mixture of concentrated sulfuric acid–
ethanol was a simple laboratory procedure giving high
yields of the target products.
EXPERIMENTAL
Melting points were measured on a Boёtius heating
1
block. H and 13C NMR spectra were registered on a
4
'
spectrometer Bruker AMX-400 (400 MHz) using as
internal references the signals of residual protons (1H)
and carbon nuclei (13C) of deuterated solvents. IR
spectra were recorded on a spectrometer Shimadzu FTIR
8400S from pellets with KBr. The reaction progress was
monitored by TLC on Silufol UV-254 plates (development
under UV-irradiation).All solvents used in the study were
purified by standard procedures [11].
a doublet of doublets H , J =8.7 and 1.9 Hz, at 7.77 ppm,
3
'
and a doublet H , J 8.7 Hz, at 8.17 ppm. In its turn the spin
system of the phthalazinone ring is also represented by
three signals: one-proton multiplets at 7.81 and 8.42 ppm,
and a two-proton multiplet in the region 7.90–8.01 ppm.
An interesting feature of the spectra of these compounds
is the location of one proton signal of the phthalazinone
ring in an uncommonly weak field. Although the ortho-
nitro group in the benzene ring is known to possess a
strong deshielding effect the chemical shift of H proton
is by 0.25 ppm smaller than that of the phthalazinone
proton. Therewith this feature is characteristic of virtually
all 2-(2-nitrophenyl)phthalazin-1-one save 2-(2-nitro-5-
chlorophenyl)- and 2-(2,4-dinitrophenyl)-4-methyl-1,2-
dihydro-1-phthalazinones (IVb and Vd). In the spectrum
of compound IVb the most downfield signal is that of H4
proton of phthalazinone, and in the spectrum of Vd the
combined effect of two nitro groups in the side phenyl
2-Nitro-5-chlorophenylhydrazine (IIa). To a solu-
tion of 100 g (0.495 mol) of 1,2-dinitro-4-chlorobenzene
in 800 ml of ethanol was added at stirring 60 g
(1.20 mol) of hydrazine hydrate. The solution turned
dark-red, and gas liberation started. The reaction mixture
was stirred at room temperature for 1 h, and gradual
crystallization occurred in theis period. Then the solution
was filtered, the precipitate was washed on the filter with
ethanol (3×100 ml) and dried in air. Yield 61 g (62%), red
crystals, mp 137–139°C. 1H NMR spectrum (CDCl3), δ,
ppm: 3.81 s (NH2), 6.62 d (H4, JHH 9.0 Hz), 7.69 s (H6),
8.04 d (H3, JHH 9.0 Hz), 8.92 s (NH).
3
'
3
'
5
'
ring transfers the signals of protons H and H to the
region 8.7–8.8 ppm.
The most downfield proton signal of the phthalazinone
is apparently that of the proton in the position 8 of the
heterocycle as has been proved by an experiment with
a lanthanide shift-reagent, Eu(fod)3 complex. Inasmuch
as the most favorable for complexing the shift-reagent in
this case is the carbonyl group of the phthalazinone, it is
presumable that the strongest change in the chemical shift
should suffer the signal of the proton in the position 8.
2-Nitro-4,5-dichlorophenylhydrazine (IIb) was
similarly prepared from 50 g (0.211 mol) of 1,2-di-
nitro-4,5-dichlorobenzene and 27 g (0.450 mol) of
hydrazine hydrate. Yield of crude substance 38.5 g.After
recrystallization from ethanola yield 34.25 g (73%), red
crystals, mp 175–177°C. 1H NMR spectrum (DMSO-d6),
δ, ppm: 4.55 s (NH2), 7.83 s (ArH), 8.08 s (ArH), 9.13 s
(NH).
The experiment with 2-(2-nitro-5-chlorophenyl)-4-
methyl-1,2-dihydrophthalazin-1-one (IVa) in CDCl3
showed that at the growing concentration of Eu(fod)3
the proton signal at 8.48 ppm displaced downfield by
more than 0.5 ppm. Based on the findings obtained we
attributed this downfield signal to H8 proton both in this
and the other analogous compounds.
2-(2-Nitrophenyl)phthalazin-1(2H)-ones IV and V.
A solution of 0.060 mol of 2-acylbenzoic acid and 0.057
mol of an appropriate hydrazine was heated at reflux in a
mixture of of 80 ml of ethanol and 40 ml of 96% sulfuric
acid. On completion of the reaction (TLC monitoring)
the mixture was poured on 300 g of crushed ice, the
precipitate was filtered off, ground with 5% aqueous
NaOH and filtered off again, then it was thoroughly
washed with water, dried, and recrystallized.
The developed method of the synthesis of phthalazin-
1(2H)-ones is more efficientthan those previously applied
[7–10]. By examples of preparation of compounds of this
series with versatile substituents including alkyl, aryl,
or hydrogen in the position 4 and various 2-nitrophenyl
4-Methyl-2-(2-nitro-5-chlorophenyl)-1,2-dihydro-
phthalazin-1(2H)-one (IVa). A mixture of 9.8 g of
2-acetylbenzoic acid (IIIa) and 10.7 g of 2-nitro-5-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 5 2008

KUZNETSOV et al.
734
chlorophenylhydrazine (IIa) was boiled for 1 h. Yield
12.6 g (70%), mp 168–170°C (chloroform–ethanol).
IR spectrum, ν, cm–1: 1670, 1604, 1527, 1350, 1334,
δ, ppm: 7.61 d (H° 4-ClC6H4, J 7.9 Hz), 7.69 d (Hm
4-ClC6H4, J 7.9 Hz), 7.75–7.83 m (H5,4'), 7.94–8.04 m
(H6,7,6'), 8.18 d (H , J 8.8 Hz), 8.42 m (H ). Found, %:
C 58.24; H 2.70; N 10.40. C20H11Cl2N3O3. Calculated ,
%: C 58.27; H 2.69; N 10.19.
3
8
'
1
1326, 1172, 1142, 773, 753, 690. H NMR spectrum
4
'
(CDCl3), δ, ppm: 2.64 s (CH3), 7.52 d (H , J 8.6 Hz),
6
'
5–7
3
'
7.70 s (H ), 7.78–7.94 m (H ), 8.04 d (H , J 8.6 Hz),
8.48 d (H8, J 7.8 Hz). Found, %: C 57.10; H 3.12;
N 13.49. C15H10ClN3O3. Calculated , %: C 57.07; H 3.19;
N 13.31.
2-(2-Nitro-5-chlorophenyl)-4-(4-ethylphenyl)-1,2-
dihydrophthalazin-1(2H)-one (IVf). A mixture of
15.2 g of 2-(4-ethylbenzoyl)benzoic acid (IIIf) and
10.7 g of 2-nitro-5-chlorophenylhydrazine (IIa) was
boiled for 1.5 h. Yield 8.1 g (35%), mp 218–220°C
2-(2-Nitro-5-chlorophenyl)-1,2-dihydrophtha-
lazin-1(2H)-one (IVb). A mixture of 9.0 g of 2-formyl-
benzoic acid (IIIb) and 10.7 g of 2-nitro-5-chloro-
phenylhydrazine (IIa) was boiled for 1 h. Yield
7.7 g (45%), mp 175–177°C (chloroform–ethanol). IR
spectrum, ν, cm–1: 1663, 1595, 1525, 1343, 752. 1H NMR
1
(chloroform–ethanol). H NMR spectrum (DMSO-d6),
δ, ppm: 1.24 t (CH2CH3, J 7.4 Hz), 2.69 q (CH2CH3,
J 7.4 Hz), 7.42 d (Hm 4-EtC6H4, J 7.4 Hz), 7.57 d (H°
4-EtC6H4, J 7.4 Hz), 7.79–7.88 m (H5,4'), 7.96–8.11 m
3
8
(H6,7,6'), 8.21 d (H , J 8.6 Hz), 8.41 m (H ). Found:
C 65.00; H 3.87; N 10.57. C22H16ClN3O3. Calculated ,
%: C 65.11; H 3.97; N 10.35.
'
4
'
spectrum (DMSO-d6), δ, ppm: 7.75 d.d (H , J 8.8 and
6
7
'
2.1 Hz), 7.84 d (H , J 2.1 Hz), 7.91 m (H ), 7.97–8.05 m
5,6
3
'
8
(H ), 8.16 d (H , J 8.8 Hz), 8.31 d (H , J 7.6 Hz), 8.58 s
(H4). Found, %: C 55.59; H 2.53; N 14.15. C14H8ClN3O3.
Calculated , %: C 55.74; H 2.67; N 13.93.
4-(3,4-Dimethylphenyl)-2-(2-nitro-5-chloro-
phenyl)-1,2-dihydrophthalazin-1(2H)-one (IVg).
A mixture of 15.2 g of 2-(3,4-dimethylbenzoyl)benzoic
acid (IIIg) and 10.7 g of 2-nitro-5-chlorophenylhydrazine
(IIa) was boiled for 1.5 h. Yield 8.6 g (37%), mp 238–
240°C (chloroform–ethanol). 1H NMR spectrum (DMSO-
d6), δ, ppm: 2.31 s (2Me), 7.30–7.44 m (Me2C6H3 ),
2-(2-Nitro-5-chlorophenyl)-4-phenyl-1,2-dihydro-
phthalazin-1(2H)-one (IVc). A mixture of 13.6 g of
2-benzoylbenzoic acid (IIIc) and 10.7 g of 2-nitro-5-
chloro-phenylhydrazine (IIa) was boiled for 1 h. Yield
12.4 g (58%), mp 137–139°C (chloroform–ethanol). IR
spectrum, ν, cm–1: 1672, 1599, 1587, 1536, 1472, 1348,
6,7,6
3
'
7.78–7.87 m (H5,4'), 7.94–8.10 m (H '), 8.20 d (H ,
J 8.8 Hz), 8.39 m (H8). Found: C 64.97; H 3.81; N 10.56.
C22H16ClN3O3. Calculated ,%:C65.11; H 3.97; N 10.35.
1
1326, 1137, 739, 692. H NMR spectrum (DMSO-d6),
δ, ppm: 7.53–7.69 m (4-phenyl), 7.75–7.84 m (H5,4'),
4-(2,4-Dimethylphenyl)-2-(2-nitro-5-chloro-
phenyl)-1,2-dihydrophthalazin-1(2H)-one (IVh).
A mixture of 15.2 g of 2-(2,4-dimethylbenzoyl)benzoic
acid (IIIh) and 10.7 g of 2-nitro-5-chlorophenylhydrazine
(IIa) was boiled for 1.5 h. Yield 8.8 g (38%), mp
3
8
7.92–8.04 m (H6,7,6'), 8.19 d (H , J 8.8 Hz), 8.42 m (H ).
Found, %: C 63.51; H 3.23; N 11.35. C20H12ClN3O3.
Calculated , %: C 63.59; H 3.20; N 11.12.
'
2-(2-Nitro-5-chlorophenyl)-4-(4-tolyl)-1,2-
dihydrophthalazin-1(2H)-one (IVd). A mixture of
14.4 g of 2-(4-methylbenzoyl)benzoic acid (IIId) and
10.7 g of 2-nitro-5-chlorophenylhydrazine (IIa) was
boiled for 1 h. Yield 13.4 g (60%), mp 184–186°C
1
204–206°C (chloroform–ethanol). H NMR spectrum
(DMSO-d6), δ, ppm: 2.09 s (4-CH3), 2.37 s (2-CH3),
5
4
'
7.14–7.25 m (Me2C6H3), 7.32 m (H ), 7.83 d.d (H , J 8.8
6,7
6
'
and 2.0 Hz), 7.92–8.01 m (H ), 8.04 d (H , J 2.0 Hz),
1
3
8
'
(chloroform–ethanol). H NMR spectrum (DMSO-d6),
8.21 d (H , J 8.8 Hz), 8.40 m (H ). Found, %: C 65.10;
H 3.89; N 10.52. C22H16ClN3O3. Calculated , %: C 65.11;
H 3.97; N 10.35.
δ, ppm: 2.43 s (CH3), 7.36 d (Hm Tol, J 7.9 Hz), 7.52 d
4
'
(H° Tol, J 7.9 Hz), 7.77 d.d (H , J 8.7 and 1.9 Hz),
7.81 m (H5), 7.90–8.01 m (H6,7), 7.97 d (H6’, J 1.9 Hz),
4-(2,5-Dimethylphenyl)-2-(2-nitro-5-chloro-
phenyl)-1,2-dihydrophthalazin-1(2H)-one (IVi).
A mixture of 15.2 g of 2-(2,5-dimethylbenzoyl)benzoic
acid (IIIi) and 10.7 g of 2-nitro-5-chlorophenylhydrazine
(IIa) was boiled for 1.5 h. Yield 10.9 g (47%), mp
3
'
8
8.17 d (H , J 8.7 Hz), 8.42 m (H ). Found, %: C 64.24;
H 3.48; N 10.92. C21H14ClN3O3. Calculated , %: C 64.38;
H 3.60; N 10.72.
2-(2-Nitro-5-chlorophenyl)-4-(4-chlorophenyl)-
1,2-dihydrophthalazin-1(2H)-one (IVe). A mixture
of 15.6 g of 2-(4-chlorobenzoyl)benzoic acid (IIIe)
and 10.7 g of 2-nitro-5-chlorophenylhydrazine (IIa)
was boiled for 1 h. Yield 12.4 g (53%), mp 190–192°C
1
205–207°C (chloroform–ethanol). H NMR spectrum
(DMSO-d6), δ, ppm: 2.13 s (5-CH3), 2.38 s (2-CH3),
5
4
'
7.12–7.24 m (Me2C6H3), 7.37 m (H ), 7.77 d.d (H ,
6
'
J 8.9 and 2.2 Hz), 7.83 d (H , J 2.2 Hz), 7.86–7.93 m
(H ), 8.15 d (H , J 8.9 Hz), 8.42 m (H ). Found, %:
1
6,7
3
'
8
(chloroform–ethanol). H NMR spectrum (DMSO-d6),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 5 2008

BENZO[4,5]IMIDAZO[2,1-a]PHTHALAZINES: I.
735
benzoic acid (IIIa) and 11.4 g of 2,4-dinitrophenyl-
hydrazine (IId) was boiled for 1.5 h in a mixture
of 40 ml of ethanol and 40 ml of 96% sulfuric acid.
Yield 9.9 g (54%), mp 244–246°C (DMF). IR spectrum,
ν, cm–1: 3073, 1671, 1608, 1540, 1530, 1350, 1337, 773.
1H NMR spectrum (DMSO-d6), δ, ppm: 2.66 s (CH3),
C 65.07; H 3.91; N 10.54. C22H16ClN3O3. Calculated, %:
C 65.11; H 3.97; N 10.35.
2-(4,5-Dichloro-2-nitrophenyl)-4-methyl-1,2-di-
hydrophthalazin-1(2H)-one (Va). A mixture of 9.8 g
of 2-acetylbenzoic acid (IIIa) and 12.7 g of 2-nitro-5-
chlorophenylhydrazine (IIb) was boiled for 1 h. Yield
12.4 g (62%), mp 205–207°C (chloroform–ethanol).
1H NMR spectrum (DMSO-d6), δ, ppm: 2.64 s (CH3),
7.92 m (ArH), 8.00–8.09 m (H5–7, 6'), 8.34 d (H8,
7
5,6
6
'
7.94 m (H ), 8.00–8.06 m (H ), 8.09 d (H , J 8.9 Hz),
8
5
'
8.36 d (H , J 7.5 Hz), 8.72 d.d (H , J 8.9 and 1.8 Hz),
8.81 d (H3', J 1.8 Hz). Found, %: C 55.05; H 3.00; N 17.34.
C15H10N4O5. Calculated , %: C 55.22; H 3.09; N 17.17.
3
'
J 7.7 Hz), 8.41 C (H ). Found, %: C 51.39; H 2.39;
N 11.97. C15H9Cl2N3O3. Calculated , %: C 51.45; H 2.59;
N 12.00.
REFERENCES
4-Methyl-2-(2-nitrophenyl)-1,2-dihydrophtha-
lazin-1(2H)-one (Vb). A mixture of 9.8 g of 2-acetyl-
benzoic acid (IIIa) and 8.8 g of 2-nitrophenylhydrazine
(IIc) was boiled for 1.5 h. Yield 9.6 g (60%), mp 195–
197°C (chloroform–ethanol). IR spectrum, ν, cm–1: 1668,
1. Rowe, F.M., Adams, D.A.W., Peters, A.T., and Gil-
lam, J.M., J. Chem. Soc., 1937, p. 90.
2. King, F.,D., J. Chem. Soc., Perkin Trans. I, 1988,
p. 3381.
3. Razvi, M. and Ramalingam, T., Indian, J. Chem. B, 1992,
vol. 31, p. 788.
4. Kuznetsov, V.A., Shubin, K.M., and Petrov, M.L., Zh. Org.
Khim., 2004, vol. 40, p. 1746.
1
1533, 1356, 1340, 1175, 777, 687. H NMR spectrum
(DMSO-d6), δ, ppm: 2.62 s (CH3), 7.62–8.02 m
3
8
(H5–7, 4 –6'), 8.10 d (H , J 7.9 Hz), 8.32 d (H , J 7.5 Hz).
Found, %: C 63.81; H 3.82; N 15.14. C15H11N3O3.
Calculated , %: C 64.05; H 3.94; N 14.94.
'
'
5. Maaskant, L. and Deliddo, F., Gazz. Chim. Ital., 1933,
vol. 63, p. 612.
2-(2-Nitrophenyl)-4-(4-chlorophenyl)-1,2-dihydro-
phthalazin-1(2H)-one (Vc). A mixture of 15.6 g of
2-(4-chlorobenzoyl)benzoic acid (IIIe) and 8.7 g of
2-nitrophenylhydrazine (IIc) was boiled for 1 h. Yield
6.0 g (55%), mp 167–169°C (ethanol). 1H NMR spectrum
6. Lindley, J.M., McRobbie, I.M., Meth-Cohn, O., and
Suschitzky, H., J. Chem. Soc., Perkin Trans. I, 1980, p. 982.
7. Yakovlev, S.V. and Pavlova, L.A. , Zh. Org. Khim., 1988,
vol. 24, p. 2433.
8. Runti, C. and Galimberti, S., Ann. Chim. (Rome), 1957,
vol. 47, p. 250.
9. Morgan, D.O., Ollis, W.D., and Stanforth, S.P., Tetrahedron,
2000, vol. 56, p. 5523.
10. Rowe, F.M. and Osborn, W. A., J. Chem. Soc., 1947, p. 829.
11. Gordon, A.J. and Ford, R.A., The Chemist’s Companion,
New York: Wiley, 1972.
(DMSO-d6), δ, ppm: 7.52–8.01 m [H5–7, 4 –6', 4-(4-
'
3
'
chlorophenyl)], 8.09 d.d (H , J 8.0 and 1.2 Hz), 8.43 m
(H8). Found, %: C 63.41; H 3.29; N 11.33. C20H12ClN3O3.
Calculated , %: C 63.59; H 3.20; N 11.12.
2-(2,4-Dinitrophenyl)-4-methyl-1,2-dihydrophtha-
lazin-1(2H)-one (Vd). A mixture of 9.9 g of acetyl-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 5 2008