Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime ethers: XIII.* specificity of bromination of N-acetyl(aroyl)-1,4- benzoquinone monoimines

Article abstract of DOI:10.1134/S1070428011100101

6-Hydroxy-2-methyl(aryl)-1,3-benzoxazoles were synthesized by bromination of N-acetyl(aroyl)-1,4-benzoquinone monoimines. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S1070428011100101

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 10, pp. 1508–1514. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.P. Avdeenko, S.A. Konovalova, O.P. Ledeneva, O.N. Ludchenko, G.V. Palamarchuk, R.I. Zubatyuk, O.V. Shishkin, 2011,
published in Zhurnal Organicheskoi Khimii, 2011, Vol. 47, No. 10, pp. 1482–1487.
Halogenation of N-Substituted p-Quinone
Monoimines and p-Quinone Monooxime Ethers:
XIII.* Specificity of Bromination of N-Acetyl(aroyl)-
1,4-benzoquinone Monoimines
A. P. Avdeenkoa, S. A. Konovalovaa, O. P. Ledenevaa, O. N. Ludchenkoa, G. V. Palamarchukb,
R. I. Zubatyukb, and O. V. Shishkinb
a Donbass State Machine Building Academy, ul. Shkadinova 72, Kramatorsk, 84313 Ukraine
e-mail: chimist@dgma.donetsk.ua
b Institute of Single Crystals, National Academy of Sciences of Ukraine, Khar’kov, Ukraine
Received December 16, 2010
Abstract—6-Hydroxy-2-methyl(aryl)-1,3-benzoxazoles were synthesized by bromination of N-acetyl(aroyl)-
1,4-benzoquinone monoimines.
DOI: 10.1134/S1070428011100101
In the preceding communications of this series we
described in detail halogenation of N-aroyl-1,4-benzo-
quinone monoimines and their reduction products
[1–5], as well as of 4-acetylaminophenols having no
other substituents in the benzene ring [6]. Various
halogen-containing derivatives were obtained and
specificity of halogenation related to the effect of
strong electron-withdrawing substituent on the nitro-
gen atom was revealed. In particular, low stability of
intermediate cyclohexene structures [1, 2], halogena-
tion of methyl groups in the quinoid ring, and forma-
tion of 5-aroyloxycyclohex-2-ene-1,4-diones [2, 3]
were observed.
transformation of 1,4-naphthoquinone derivative in-
volved dehydrochlorination on heating with acetic
anhydride in the presence of traces of sulfuric acid [8]
(Scheme 2). In these reactions, the quinoid moiety
exerts an activating effect.
Benzoxazoles are also formed by the action of
excess bromine on 2,4-bis(acetylamino)phenol [9]
(Scheme 3). Benzoxazoles were obtained previously
by hydrochlorination of p-quinonedipivalimides
(among other products) [10] and by treatment of
p-quinonedibenzimide with sulfuric acid in benzene
[11]. The formation of benzoxazoles via hydrochlori-
nation was favored by the presence of chlorine atoms
in positions 2 and 6 of the quinoid ring [10] and by
acidic conditions [10, 11].
In keeping with published data, 2-benzoylamino-
substituted 1,3-dibromoanthraquinone having a frag-
ment similar to bromine-containing 4-aroylamino-
phenols is converted into anthroxazole via dehydro-
bromination on heating [7] (Scheme 1). Analogous
The goal of the present work was to synthesize
benzoxazoles from halogen-substituted N-acyl-1,4-
benzoquinone monoimines. In our previous studies,
Scheme 1.
Ph
O
O
Br
O
O
O
N
NHCOPh
Br
Br
* For communication XII, see [1].
1508

HALOGENATION OF N-SUBSTITUTED p-QUINONE MONOIMINES ... XIII.
1509
Scheme 2.
O
O
NHCOMe
Cl
N
O
Me
O
O
Scheme 3.
Br
OH
Br
O
Br2
O
O
Me
–H2O
N
Me
N
NHCOMe
Me
N
H
H
halogenation of various N-acetyl(aroyl)-1,4-benzo-
quinone monoimines gave only halogenated quinone
monoimines, aminophenols, cyclohexene structures,
and 5-aroyloxycyclohex-2-ene-1,4-diones [1–6],
whereas hydrohalogenation of the same substrates
afforded the corresponding 1,4-addition products [1–6,
12]. All possible steps in the hydrohalogenation proc-
ess were examined, while halogenation of N-acetyl-
(aroyl)-1,4-benzoquinone monoimines having halogen
atoms in the quinoid ring was not studied specially.
Benzoxazoles XVa and XVb were also obtained by
bromination of 4-aroylimino-2,6-di-tert-butyl-5,5,6-tri-
chlorocyclohex-2-en-1-ones XIVa and XIVb under
similar conditions (Scheme 5). Compounds XIVa and
XIVb are chlorination products of N-aroyl-2,6-di-tert-
butyl-1,4-benzoquinone imines [5]. It should be em-
phasized that only one tert-butyl group was present in
molecules XV. Analogous replacement of tert-butyl
group was observed previously in the chlorination of
4-aroylamino-2,6-di-tert-butylphenols [5] and in the
reaction of 2,6-di-tert-butyl-1,4-benzoquinone 4-oxime
with S2Cl2 in the presence of ethyl(diisopropyl)amine
and N-chlorosuccinimide in tetrahydrofuran [13].
In this work we performed halogenation of various
N-acetyl(aroyl)-1,4-benzoquinone monoimines con-
taining one to three halogen atoms in the quinoid ring.
N-Acetyl(aroyl)-1,4-benzoquinone monoimines I–VII
having one free ortho position with respect to the C=N
carbon atom reacted with bromine at a molar ratio of
1:5 in chloroform to give benzoxazoles VIII–XIII
(Scheme 4). Bromination of the same compounds in
other solvents (dimethylformamide, acetic acid, or
dimethylformamide–acetic acid mixture) at different
reactant ratios resulted in halogenation of the quinoid
ring or did not occur (initial quinone monoimines were
recovered from the reaction mixtures), regardless of
the conditions.
The structure of benzoxazole derivatives VIII–
XIII and XV was proved by their elemental analyses
and IR and 1H and 13C NMR spectra. The IR spectra of
these compounds contained absorption bands typical of
C=N (1610 cm–1) and OH groups (3500 cm–1), while
no absorption bands assignable to carbonyl stretching
vibration bands were observed (1630–1655 cm–1). The
1
hydroxy proton resonated in the H NMR spectra as
a broadened singlet at δ 5.83–6.20 ppm, the methyl
proton signal was displaced considerably downfield
(δ 2.48–3.22 ppm) relative to the corresponding signal
Scheme 4.
O
OH
6
R1
R3
R2
R1
O
R3
R2
5
Br2, CHCl3
7
4
7a
3a
2
N
N
XC(O)
X
Ia, Ib, IIa, IIb, IIf, IIIa, IIIb, IVb, IVc, IVf
Va, Vb, Vd, Vg, VIa–VIe, VIg, VIIa–VIIe, VIIg
VIIIa, VIIIb, IXa, IXb, IXf, Xa, Xb, XIb, XIc
XIf, XIIa–XIIe, XIIg, XIIIa–XIIIe, XIIIg
I, VIII, R1 = Me, R2 = R3 = Cl; II, IX, R1 = Me, R2 = R3 = Br; III, X, R1 = R3 = Cl, R2 = Me; IV, XI, R2 = Me, R1 = R3 = Br; V, R1 =
i-Pr, R2 = Me, R3 = H; VI, XII, R1 = i-Pr, R2 = Me, R3 = Cl; VII, XIII, R1 = i-Pr, R2 = Me, R3 = Br; X = Ph (a), 4-MeC6H4 (b),
4-ClC6H4 (c), 4-O2NC6H4 (d), 3-O2NC6H4 (e), 4-Br-3-MeOC6H3 (f), Me (g).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011

AVDEENKO et al.
carbon atom in the ortho position with respect to the
1510
Scheme 5.
Bu-t
O
N
second C=N carbon atom possessing a partial positive
charge. However, the reaction mixture in the bromina-
tion of quinone monoimines I–VII contains no
protons. It is known that halogenation of N-substituted
1,4-benzoquinone monoimines involves formation of
intermediate halonium ion or carbocation [4, 15].
Bromination of quinone monoimines in the presence of
LiCl occurs at the ortho position with respect to the
carbonyl carbon atom [15]. Taking into account the
above stated, we presumed that bromination of qui-
none monoimines I–VII in chloroform involves initial
formation of bromonium ion A which can be converted
into tautomer B and carbocation C; the latter tends to
undergo intramolecular cyclization to give interme-
diate D rather than to take up bromide ion (Scheme 6).
Prototropic rearrangement and elimination of bromine
cation yields final benzoxazole derivative. In polar
protic solvents favoring polarization of bromine mole-
cule and protonation of initial quinone monoimine,
addition of bromide ion to cation C is more advan-
tageous, and quinone monoimines and aminophenols
containing additional bromine atoms are formed. Thus
the mechanism of formation of benzoxazoles VIII–
XIII and XV differs from those proposed in [7–11].
Bu-t
OH
Cl
t-Bu
O
N
Br2
Cl
X
Cl
Cl
Cl
XC(O)
XIVa, XIVb
XVa, XVb
X = Ph (a), 4-MeC6H4 (b).
of aminophenols, and no aromatic proton signal was
present.
The molecular structure of 5-bromo-6-hydroxy-7-
isopropyl-4-methyl-2-(4-nitrophenyl)-1,3-benzoxazol-
6-ol (XIIId) was unambiguously determined by X-ray
analysis (see figure). All non-hydrogen atoms in mole-
cule XIIId in crystal (except for methyl carbon atoms
in the isopropyl substituent) lie in one plane. Such
conformation is stabilized by attractive intramolecular
interactions O2···H8A 2.33 Å (the sum of the van der
Waals radii is 2.46 Å [14]), Br1···H7A 2.85 (3.13 Å),
and Br1···H2A (2.56 Å), which may be regarded as
very weak intramolecular hydrogen bonds, taking into
account small angles ∠C8H8AO2 111°, ∠C7H7ABr1
105°, and ∠O2H2ABr1 126°. The same factor is respon-
sible for orientation of the isopropyl group which is
turned so that the C8–H8A bond is coplanar to the bicy-
clic fragment (torsion angle C3C2C8H8A is equal to 0°).
Benzoxazoles were obtained mainly by bromination
of quinone monoimines in which only one meta posi-
tion in the quinoid ring was free. As shown previously,
halogenation of N-substituted 1,4-benzoquinone
monoimines follows different paths including halogen
addition at the double C=C bond in the quinoid ring,
dehydrohalogenation, hydrohalogenation, prototropic
rearrangement, and electrophilic substitution, so that
It was presumed previously [10] that the formation
of benzoxazoles in the hydrochlorination of p-quinone-
dipivalimides is the result of protonation of the nitro-
gen atom and subsequent ring closure involving the
Scheme 6.
O
O
O
R1
R1
Br
R3
R2
R1
Br
R3
R2
R3
R2
Br
H
H
X
H
X
N
N
X
N
δ+
δ+
O
Oδ–
Oδ–
A
B
C
R1
Br R1
H
O
OH
R3
O
N
O
N
–Br+
X
X
R3
R2
R2
D
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011

HALOGENATION OF N-SUBSTITUTED p-QUINONE MONOIMINES ... XIII.
the reaction mixtures are complex multicomponent
1511
C9A
systems [1–6, 15–17]. As the number of halogen atoms
in the quinoid ring increases, further addition of halo-
gen or hydrogen halide becomes more difficult, and
more severe conditions are necessary [1–3, 12, 16, 17].
In the bromination of N-acetyl(aroyl)-1,4-benzoqui-
none monoimines having two or more unoccupied
positions in the quinoid ring, first addition of bromine
molecule and subsequent dehydrohalogenation inevi-
tably produce some amount of hydrogen bromide. As
a result, further halogenation or hydrohalogenation of
the quinoid ring becomes more favorable than ring
closure through the oxygen atom.
C8
C2
O2
C9
C1
O1
C3
C4
C16
C17
O3
C11
Br1
C15
C12
C13
C6
C5
C7
N2
O4
N1
C14
Structure of the molecule of 5-bromo-7-isopropyl-4-methyl-
2-(4-nitrophenyl)-1,3-benzoxazol-6-ol (XIIId) according to
the X-ray diffraction data.
EXPERIMENTAL
The H and 13C NMR spectra were measured from
1
solutions in CDCl3 on a Varian VXR-300 spectrometer
(300 and 75.4 MHz, respectively) using tetramethyl-
silane as reference. The IR spectra were recorded in
KBr on a UR-20 spectrometer. The reaction mixtures
were analyzed by TLC on Silufol UV-254 plates. Spots
were applied from solutions in chloroform, benzene–
hexane (10:1) was used as eluent, and components
were detected under UV light.
Initial quinone monoimines Ia, Ib, IIa, IIb, IIIa,
IIIb, IVb, IVc [1], IIf, IVf [20], Vg, VIg, VIIg [12],
Va, Vb, Vd, VIa–VIe, VIIa–VIIe [3], XIVa, and
XIVb [5] were synthesized according to known meth-
ods; their properties were consistent with published
data.
4-Chloro-N-(3-chloro-5-isopropyl-2-methyl-4-
oxocyclohexa-2,5-dien-1-ylidene)benzamide (VIc).
1
X-Ray analysis of compound XIIId. Monoclinic
crystals, C17H15BrN2O4, with the following unit cell
parameters (293 K): a = 9.152(3), b = 6.942(2), c =
13.572(3) Å; β = 100.23(3); V = 848.6(4) Å3; MR =
391.22; Z = 2; space group P21/m; dcalc = 1.531 g/cm3;
μ(MoKα) = 2.445 mm–1; F(000) = 396. The unit cell
parameters and intensities of 24 333 reflections
(2622 independent reflections, Rint = 0.029) were
measured on an Xcalibur 3 automatic four-circle dif-
fractometer (MoKα irradiation, CCD detector, graphite
monochromator, ω- and φ-scanning, 2θmax = 60°).
Empirical absorption corrections (multiscan) were
Yield 88%, mp 114–116°C. H NMR spectrum, δ,
ppm: 1.05 d [6H, CH(CH3)2, J = 6.9 Hz], 2.42 s (3H,
2-Me), 3.00–3.09 m (1H, 5-CH), 6.59 d (1H, 6-H, J =
0.9 Hz), 7.48–7.85 d.d (4H, C6H4, J = 9.0 Hz). Found,
%: Cl 20.77, 20.95; N 3.84, 4.11. C17H15Cl2NO2. Cal-
culated, %: Cl 21.09; N 4.17.
N-(3-Chloro-5-isopropyl-2-methyl-4-oxocyclo-
hexa-2,5-dien-1-ylidene)-3-nitrobenzamide (VIe).
1
Yield 75%, mp 144–145°C. H NMR spectrum, δ,
ppm: 1.07 d [6H, CH(CH3)2, J = 6.9 Hz], 2.46 s (3H,
2-Me), 3.00–3.11 m (1H, 5-CH), 6.64 d (1H, 6-H, J =
0.9 Hz), 7.74 t (1H, 5′-H), 8.26–8.28 d.d (1H, 6′-H,
applied using CrysAlis RED software [18]; Tmin
=
3
4
3J = 7.8 Hz), 8.47–8.50 d.d (1H, 4′-H, J = 9.0, J =
0.62, Tmax = 0.78. The structure was solved by the
direct method using SHELX97 [19]. The positions of
hydrogen atoms were determined by difference syn-
thesis of electron density and were refined according to
the riding model (Uiso = nUeq; n = 1.5 for methyl and
hydroxy groups, n = 1.2 for other hydrogen atoms).
The structure was refined with respect to F2 by the
full-matrix least-squares procedure in anisotropic ap-
proximation for non-hydrogen atoms until wR2 = 0.069
for 1875 reflections [R1 = 0.031 for 1684 reflections
with F > 4σ(F), S = 0.99]. The coordinates of atoms,
geometric parameters of the molecule, and crystallo-
graphic data were deposited to the Cambridge Crystal-
lographic Data Centre (entry no. CCDC 801257).
4
0.9 Hz), 8.73 d (1H, 2′-H, J = 3.9 Hz). Found, %:
Cl 23.95, 24.20; N 4.55, 4.75. C17H15ClN2O4. Calcu-
lated, %: Cl 10.22; N 8.08.
N-(3-Bromo-5-isopropyl-2-methyl-4-oxocyclo-
hexa-2,5-dien-1-ylidene)-4-chlorobenzamide (VIIc).
1
Yield 83%, mp 111–112°C. H NMR spectrum, δ,
ppm: 1.06 d [6H, CH(CH3)2, J = 6.9 Hz], 2.47 s (3H,
2-Me), 2.98–3.11 m (1H, 5-CH), 6.58 d (1H, 6-H, J =
1.5 Hz), 7.48–7.84 d.d (4H, C6H4, J = 8.7 Hz). Found,
%: Br 20.67, 20.85; N 3.48, 3.69. C17H15BrClNO2.
Calculated, %: Br 20.99; N 3.68.
N-(3-Bromo-5-isopropyl-2-methyl-4-oxocyclo-
hexa-2,5-dien-1-ylidene)-3-nitrobenzamide (VIIe).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011

AVDEENKO et al.
1512
1
Yield 68%, mp 149.5–151°C. H NMR spectrum
(DMSO-d6), δ, ppm: 1.07 d [6H, CH(CH3)2, J =
6.9 Hz], 2.50 s (3H, 2-Me), 3.02–3.14 m (1H, 5-CH),
6.63 d (1H, 6-H, J = 0.9 Hz), 7.74 t (1H, 5′-H), 8.25–
8.7 Hz). Found, %: Br 50.28, 50.43; N 2.79, 3.06.
C15H10Br3NO3. Calculated, %: Br 50.36; N 2.94.
5,7-Dichloro-4-methyl-2-phenyl-1,3-benzoxazol-
1
6-ol (Xa). Yield 68%, mp 152–153.5°C. H NMR
3
8.28 d.d (1H, 6′-H, J = 7.8 Hz), 8.47–8.50 d.d (1H,
spectrum, δ, ppm: 2.68 s (3H, 4-Me), 6.02 br.s (1H,
OH), 7.53–8.28 m (5H, Ph). Found, %: Cl 23.95,
24.20; N 4.55, 4.75. C14H9Cl2NO2. Calculated, %:
Cl 24.11; N 4.76.
3
4
4
4′-H, J = 9.0, J = 1.2 Hz), 8.73 d (1H, 2′-H, J =
3.6 Hz). Found, %: Br 20.47, 20.65; N 7.38, 7.59.
C17H15BrN2O4. Calculated, %: Br 20.42; N 7.16.
6-Hydroxy-2-methyl(aryl)-1,3-benzoxazoles
VIII–XIII and XV (general procedure). A solution of
2 mmol of quinone imine I–VII or cyclohexenone
XIV in 3 ml of chloroform was heated to 45°C, and
2 ml of a solution of bromine in chloroform was added
dropwise under stirring until a substrate-to-bromine
ratio of 1:5. The mixture was left to stand for 24 h
until complete evaporation, and the precipitate was
filtered off, washed with a small amount of acetic acid,
and recrystallized from acetic acid.
5,7-Dichloro-4-methyl-2-(4-methylphenyl)-1,3-
benzoxazol-6-ol (Xb). Yield 76%, mp 169.5–170°C.
1H NMR spectrum, δ, ppm: 2.46 s (3H, MeC6H4),
2.70 s (3H, 4-Me), 6.02 br.s (1H, OH), 7.33–8.19 d.d
(4H, C6H4, J = 7.2 Hz). Found, %: Cl 22.77, 22.95;
N 4.61, 4.83. C15H11Cl2NO2. Calculated, %: Cl 23.01;
N 4.55.
5,7-Dibromo-4-methyl-2-(4-methylphenyl)-1,3-
benzoxazol-6-ol (XІb). Yield 83%, mp 127.5–
1
128.5°C. H NMR spectrum, δ, ppm: 2.49 s (3H,
4,5-Dichloro-7-methyl-2-phenyl-1,3-benzoxazol-
6-ol (VIIIa). Yield 84%, mp 150.5–151.5°C. 1H NMR
spectrum, δ, ppm: 2.50 s (3H, 7-Me), 5.87 br.s (1H,
OH), 7.50–8.28 m (5H, Ph). Found, %: Cl 23.86,
24.15; N 4.37, 4.60. C14H9Cl2NO2. Calculated, %:
Cl 24.11; N 4.76.
MeC6H4), 2.88 s (3H, 4-Me), 6.20 br.s (1H, OH),
7.43–8.45 d.d (4H, C6H4, J = 7.2 Hz). Found, %:
Br 40.25, 40.51; N 3.28, 3.56. C15H11Br2NO2. Calcu-
lated, %: Br 40.25; N 3.53.
5,7-Dibromo-2-(4-chlorophenyl)-4-methyl-1,3-
benzoxazol-6-ol (XІc). Yield 84%, mp 210–212°C.
1H NMR spectrum, δ, ppm: 2.68 s (3H, 4-Me),
6.08 br.s (1H, OH), 7.50–8.18 d.d (4H, C6H4, J =
9.0 Hz). Found, %: Br+Cl 46.48, 46.72; N 3.08, 3.25.
C14H8Br2ClNO2. Calculated, %: Br+Cl 46.77; N 3.36.
4,5-Dichloro-7-methyl-2-(4-methylphenyl)-1,3-
benzoxazol-6-ol (VIIIb). Yield 76%, mp 179–
1
180.5°C. H NMR spectrum, δ, ppm: 2.44 s (3H,
MeC6H4), 2.48 s (3H, 7-Me), 5.88 br.s (1H, OH),
7.32–8.16 d.d (4H, C6H4, J = 7.8 Hz). Found, %:
Cl 23.07, 23.35; N 4.61, 4.88. C15H11Cl2NO2. Calculat-
ed, %: Cl 23.01; N 4.55.
5,7-Dibromo-2-(4-bromo-3-methoxyphenyl)-4-
methyl-1,3-benzoxazol-6-ol (XIf). Yield 78%,
1
mp 180.5–182°C. H NMR spectrum, δ, ppm: 2.71 s
4,5-Dibromo-7-methyl-2-phenyl-1,3-benzoxazol-
6-ol (IXa). Yield 71%, mp 181–182°C. 1H NMR spec-
trum, δ, ppm: 2.49 s (3H, 7-Me), 5.84 br.s (1H, OH),
7.52–8.28 m (5H, Ph). Found, %: Br 41.57, 41.82;
N 3.00, 3.26. C14H9Br2NO2. Calculated, %: Br 41.72;
N 3.36.
(3H, 4-Me), 3.89 s (3H, MeO), 6.12 br.s (1H, OH),
3
4
6.93–6.95 d.d (1H, 6′-H, J = 8.0, J = 3.3 Hz), 7.59 d
(1H, 2′-H, 4J = 3.3 Hz), 7.65 d (1H, 5′-H, J = 9.0 Hz).
Found, %: Br 50. 41, 50. 62; N 2. 93, 3. 17.
C15H10Br3NO3. Calculated, %: Br 50.36; N 2.94.
5-Chloro-7-isopropyl-4-methyl-2-phenyl-1,3-
benzoxazol-6-ol (XIIa). Yield 81%, mp 209–210°C.
1H NMR spectrum, δ, ppm: 1.50 d (6H, CHMe2, J =
9.0 Hz), 2.81 s (3H, 4-Me), 3.57–3.73 m (1H, 7-CH),
5.91 br.s (1H, OH), 7.59–8.44 m (5H, Ph). Found, %:
Cl 11.77, 11.93; N 4.80, 5.06. C17H16ClNO2. Calcu-
lated, %: Cl 11.75; N 4.64.
4,5-Dibromo-7-methyl-2-(4-methylphenyl)-1,3-
benzoxazol-6-ol (IXb). Yield 77%, mp 158.5–160°C.
1H NMR spectrum, δ, ppm: 2.44 s (3H, MeC6H4),
2.49 s (3H, 7-Me), 5.83 br.s (1H, OH), 7.36–8.18 d.d
(4H, C6H4, J = 8.1 Hz). Found, %: Br 40.07, 40.26;
N 3.51, 3.82. C15H11Br2NO2. Calculated, %: Br 40.25;
N 3.53.
4,5-Dibromo-2-(4-bromo-3-methoxyphenyl)-
5-Chloro-7-isopropyl-4-methyl-2-(4-methylphe-
7-methyl-1,3-benzoxazol-6-ol (IXf). Yield 81%,
mp 189–190°C. H NMR spectrum, δ, ppm: 2.49 s
nyl)-1,3-benzoxazol-6-ol (XIIb). Yield 69%, mp 192–
193.5°C. H NMR spectrum, δ, ppm: 1.48 d (6H,
1
1
(3H, 7-Me), 3.89 s (3H, MeO), 5.87 br.s (1H, OH),
6.93–6.96 d.d (1H, 6′-H, J = 8.7, J = 3.0 Hz),
7.61 br.s (1H, 2′-H, 4J = 3.0 Hz), 7.63 d (1H, 5′-H, J =
CHMe2, J = 6.9 Hz), 2.46 s (3H, MeC6H4), 2.76 s (3H,
4-Me), 3.61–3.70 m (1H, 7-CH), 5.88 br.s (1H, OH),
7.37–8.27 d.d (4H, C6H4, J = 7.2 Hz). Found, %:
3
4
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011

HALOGENATION OF N-SUBSTITUTED p-QUINONE MONOIMINES ... XIII.
1513
Cl 11.05, 11.23; N 4.50, 4.79. C18H18ClNO2. Calcu-
lated, %: Cl 11.23; N 4.44.
CHMe2, J = 6.9 Hz), 2.71 br.s (3H, 4-Me), 3.60–
3.71 m (1H, 7-CH), 6.12 br.s (1H, OH), 7.51– 8.22 d.d
(4H, C6H4, J = 6.6 Hz). Found, %: Br+Cl 30.10,
30.38; N 3.55, 3.79. C17H15BrClNO2. Calculated, %:
Br+Cl 30.30; N 3.68.
5-Chloro-2-(4-chlorophenyl)-7-isopropyl-4-meth-
yl-1,3-benzoxazol-6-ol (XIIc). Yield 90%, mp 162–
1
164°C. H NMR spectrum, δ, ppm: 1.48 d (6H,
CHMe2, J = 7.8 Hz), 2.68 s (3H, 4-Me), 3.59–3.67 m
(1H, 7-CH), 5.98 br.s (1H, OH), 7.51–8.21 d.d (4H,
C6H4, J = 7.8 Hz). Found, %: Cl 21.10, 21.29; N 4.25,
4.39. C17H15Cl2NO2. Calculated, %: Cl 21.09; N 4.17.
5-Bromo-7-isopropyl-4-methyl-2-(4-nitro-
phenyl)-1,3-benzoxazol-6-ol (XIIId). Yield 85%,
1
mp 230–231°C. H NMR spectrum, δ, ppm: 1.49 d
(6H, CHMe2, J = 7.2 Hz), 2.69 s (3H, 4-Me), 3.62–
3.71 m (1H, 7-CH), 5.90 br.s (1H, OH), 8.37 s (4H,
C6H4). 13C NMR spectrum, δC, ppm: 17.71 (4-Me),
21.73 (Me2CH), 26.93 (CHMe2), 111.68 (C5), 116.41
(C7), 124.27 (C2′, C6′), 128.11 (C3′, C5′), 128.26 (C4),
132.90 (C1′), 135.71 (C3a), 148.06 (C6), 149.20 (C4′),
149.39 (C7a), 159.41 (C2). Found, %: Br 20.34, 20.51;
N 6.97, 7.33. C17H15BrN2O4. Calculated, %: Br 20.42;
N 7.16.
5-Chloro-7-isopropyl-4-methyl-2-(4-nitrophe-
nyl)-1,3-benzoxazol-6-ol (XIId). Yield 73%, mp 229–
1
230°C. H NMR spectrum, δ, ppm: 1.49 d (6H,
CHMe2, J = 6.9 Hz), 2.67 s (3H, 4-Me), 3.61–3.71 m
(1H, 7-CH), 6.08 br.s (1H, OH), 8.38 s (4H, C6H4).
Found, %: Cl 10. 06, 10. 34; N 7. 92, 8. 15.
C17H15ClN2O4. Calculated, %: Cl 10.22; N 8.08.
5-Chloro-7-isopropyl-4-methyl-2-(3-nitrophe-
5-Bromo-7-isopropyl-4-methyl-2-(3-nitro-
nyl)-1,3-benzoxazol-6-ol (XIIe). Yield 73%, mp 229–
230°C. H NMR spectrum, δ, ppm: 1.49 d (6H,
1
phenyl)-1,3-benzoxazol-6-ol (XIIIe). Yield 77%,
1
mp 192–194°C. H NMR spectrum, δ, ppm: 1.50 d
CHMe2, J = 7.5 Hz), 2.68 s (3H, 4-Me), 3.62–3.73 m
(1H, 7-CH), 5.98 br.s (1H, OH), 7.72 t (1H, 5′-H),
(6H, CHMe2, J = 7.5 Hz), 2.70 s (3H, 4-Me), 3.63–
3
3.72 m (1H, 7-CH), 6.15 br.s (1H, OH), 7.72 t (1H,
8.35–8.38 d.d (1H, 6′-H, J = 7.9 Hz), 8.57 d (1H,
3
3
4
5′-H), 8.35–8.38 d.d (1H, 6′-H, J = 9.0 Hz), 8.56 d
4′-H, J = 7.8 Hz), 9.03 q (1H, 2′-H, J = 3.3 Hz).
Found, %: Cl 10. 26, 10. 53; N 8. 24, 8. 57.
C17H15ClN2O4. Calculated, %: Cl 10.22; N 8.08.
(1H, 4′-H, 3J = 7.5 Hz), 9.03 q (1H, 2′-H, 4J = 3.6 Hz).
Found, %: Br 20. 15, 20. 39; N 6. 88, 7. 14.
C17H15BrN2O4. Calculated, %: Br 20.42; N 7.16.
5-Chloro-7-isopropyl-2,4-dimethyl-1,3-benzoxa-
zol-6-ol (XIIg). Yield 60%, mp 175.5–177°C. 1H NMR
spectrum, δ, ppm: 1.43 d (6H, CHMe2, J = 6.9 Hz),
2.83 s (3H, 2-Me), 3.22 s (3H, 4-Me), 3.57–3.69 m
(1H, 7-CH), 6.17 br.s (1H, OH). Found, %: Cl 14.65,
14.88; N 5.84, 6.03. C12H14ClNO2. Calculated, %:
Cl 14.79; N 5.84.
5-Bromo-7-isopropyl-2,4-dimethyl-1,3-benzoxa-
zol-6-ol (XIIIg). Yield 59%, mp 138.5–140°C.
1H NMR spectrum, δ, ppm: 1.43 d (6H, CHMe2, J =
7.2 Hz), 2.84 br.s (3H, 2-Me), 3.14 br.s (3H, 4-Me),
3.58–3.66 m (1H, 7-CH), 6.10 br.s (1H, OH). Found,
%: Br 28.19, 28.47; N 5.03, 5.26. C12H14BrNO2. Cal-
culated, %: Br 28.12; N 4.93.
5-Bromo-7-isopropyl-4-methyl-2-phenyl-1,3-
benzoxazol-6-ol (XIIIa). Yield 74%, mp 156–
157.5°C. H NMR spectrum, δ, ppm: 1.52 d (6H,
7-tert-Butyl-4,5-dichloro-2-phenyl-1,3-benzoxa-
zol-6-ol (XVa). Yield 68%, mp 189–190°C. H NMR
1
1
CHMe2, J = 6.6 Hz), 3.02 br.s (3H, 4-Me), 3.65–
3.75 m (1H, 7-CH), 6.12 br.s (1H, OH), 7.68–8.75 m
(5H, Ph). Found, %: Br 22.89, 23.17; N 4.15, 4.26.
C17H16BrNO2. Calculated, %: Br 23.08; N 4.05.
spectrum, δ, ppm: 1.67 s (9H, t-Bu), 6.12 br.s (1H,
OH), 7.52–8.23 m (5H, Ph). Found, %: Cl 21.19,
21.37; N 4.06, 4.58. C17H15Cl2NO2. Calculated, %:
Cl 21.09; N 4.17.
5-Bromo-7-isopropyl-4-methyl-2-(4-methyl-
7-tert-Butyl-4,5-dichloro-2-(4-methylphenyl)-1,3-
benzoxazol-6-ol (XVb). Yield 63%, mp 173–174°C.
1H NMR spectrum, δ, ppm: 1.66 s (9H, t-Bu), 2.45 s
(3H, MeC6H4), 6.11 br.s (1H, OH), 7.32–8.12 d.d (4H,
C6H4, J = 7.8 Hz). 13C NMR spectrum, δC, ppm: 21.58
(Me), 30.37 [C(CH3)3], 36.41 [C(CH3)3], 117.60 (C6),
119.53 (C4), 119.63 (C5), 123.77 (C7), 127.39 (C3′, C5′),
129.36 (C2′, C6′), 134.58 (C3a), 141.92 (C1′), 147.99
(C4′), 148.06 (C7a), 162.75 (C2). Found, %: Cl 20.37,
20.55; N 4.16, 4.39. C18H17Cl2NO2. Calculated, %:
Cl 20.24; N 4.00.
phenyl)-1,3-benzoxazol-6-ol (XIIIb). Yield 72%,
1
mp 163.5–165°C. H NMR spectrum, δ, ppm: 1.48 d
(6H, CHMe2, J = 6.6 Hz), 2.50 br.s (3H, MeC6H4),
2.91 br.s (3H, 4-Me), 3.64–3.73 m (1H, 7-CH),
6.17 br.s (1H, OH), 7.44–8.48 d.d (4H, C6H4, J =
7.8 Hz). Found, %: Br 22.19, 22.38; N 3.56, 3.74.
C18H18BrNO2. Calculated, %: Br 22.18; N 3.89.
5-Bromo-2-(4-chlorophenyl)-7-isopropyl-4-meth-
yl-1,3-benzoxazol-6-ol (XIIIc). Yield 81%, mp 168.5–
1
169.5°C. H NMR spectrum, δ, ppm: 1.47 d (6H,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 10 2011

AVDEENKO et al.
10. Adams, R. and Stewart, J.M., J. Am. Chem. Soc., 1952,
1514
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