Synthesis of 2-aryl(hetaryl)-1-hydroxyimidazoles by the reaction of aliphatic 1,2-hydroxylamino oximes with aromatic and heteroaromatic aldehydes

Article abstract of DOI:10.1007/s11172-013-0169-z

A reaction of aliphatic 1,2-hydroxylamino oximes bearing the hydroxylamino group at the secondary carbon atom with aromatic and heteroaromatic aldehydes in acetic acid leads to the corresponding 1-hydroxy-2-aryl(hetaryl)-4,5- dialkylimidazoles in high yields. α-Aryl(hetaryl)-nitrones initially formed by the condensation of 1,2-hydroxylamino oximes with aldehydes are quantitatively converted to the corresponding imidazoles.

Full text of DOI:10.1007/s11172-013-0169-z

Russian Chemical Bulletin, International Edition, Vol. 62, No. 5, pp. 1232—1237, May, 2013
1232
Synthesis of 2ꢀaryl(hetaryl)ꢀ1ꢀhydroxyimidazoles by the reaction
of aliphatic 1,2ꢀhydroxylamino oximes with aromatic
and heteroaromatic aldehydes
B. A. Selivanov and A. Ya. Tikhonov
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrent´eva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 330 9752. Eꢀmail: alyatikh@nioch.nsc.ru
A reaction of aliphatic 1,2ꢀhydroxylamino oximes bearing the hydroxylamino group at the
secondary carbon atom with aromatic and heteroaromatic aldehydes in acetic acid leads to the
corresponding 1ꢀhydroxyꢀ2ꢀaryl(hetaryl)ꢀ4,5ꢀdialkylimidazoles in high yields. ꢀAryl(hetaryl)ꢀ
nitrones initially formed by the condensation of 1,2ꢀhydroxylamino oximes with aldehydes are
quantitatively converted to the corresponding imidazoles.
Key words: 1ꢀhydroxyꢀ2ꢀaryl(hetaryl)ꢀ4,5ꢀdialkylimidazoles, hydroxylamino oximes,
aromatic aldehydes, ꢀaryl(hetaryl)nitrones.
Imidazole derivatives are one of the important groups
formed upon heating in vacuo of their acyl derivatives.17
Besides, 1ꢀhydroxyꢀ5ꢀmethylꢀ2,4ꢀdiphenylimidazole was
obtained by standing of the corresponding ꢀphenylꢀ
nitrone, obtained by the condensation of alkylaromatic
1,2ꢀhydroxylamino oxime (synꢀ or antiꢀisomers) with
benzaldehyde, in ethyl alcohol saturated with HCl.18 There
were no literature data on the heterocyclization of ꢀarylꢀ
nitrones obtained by the reaction of aliphatic 1,2ꢀhydrꢀ
oxylamino oximes or their acetates with aromatic aldeꢀ
hydes.5,19—22
In the present work, we studied a possibility of the prepꢀ
aration of 1ꢀhydroxyꢀ2ꢀarylimidazoles (or tautomeric imꢀ
idazole Nꢀoxides) by the reaction of aliphatic 1,2ꢀhydrꢀ
oxylamino oximes 1—3 bearing the hydroxylamino groups
at the secondary carbon atom with aromatic and heteroarꢀ
omatic aldehydes 4 (Scheme 1). A suggestion on the posꢀ
sibility of this transformation was based on the fact that
of heterocyclic compounds possessing a wide range of bioꢀ
logical activity.1—3 Among these compounds, 1ꢀhydroxyꢀ
imidazoles are of interest due to a possibility of their use in
the synthesis of medicines,3—5 since the presence of the
1ꢀhydroxy group in the imidazole ring significantly broadꢀ
ens the possibilities of synthetic modification of imidꢀ
azole molecule.6—11 1ꢀHydroxyimidazoles are commonly
synthesized either by the reaction of 1,2ꢀdiketone moꢀ
nooximes with aldehydes and ammonia or ammonium
acetate5—7,9,12,13, or by the reduction of 2ꢀsubstituted
1ꢀhydroxyimidazole 3ꢀoxides.8,9,11,14,15 1ꢀHydroxyꢀ4,5ꢀ
dialkylimidazoles (or tautomeric imidazole Nꢀoxides) are
formed by the oxidation of the imidazole ring, as a rule, in
very low yields.1,5,16 1ꢀHydroxyimidazoles obtained by
treatment of 1ꢀhydroxyꢀ3ꢀimidazoline 3ꢀoxides with dry
HCl in ethanol are isomeric to 1ꢀhydroxyimidazoles
Scheme 1
1, 5a—i, 9a—i: R1 = R2 = Me; 2, 6a—i, 10a—i: R1—R2 = (CH2)4; 3, 7d,h, 11d,h: R1—R2 = (CH2)5
Ar = Ph (a); 4ꢀMeOC6H4 (b); 4ꢀClC6H4 (c); 4ꢀNO2C6H4 (d); 3ꢀNO2C6H4 (e); 2ꢀNO2C6H4 (f); pyridinꢀ4ꢀyl (g);
pyridinꢀ2ꢀyl (h); 4ꢀOHꢀ3ꢀMeOC6H3 (i)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1232—1237, May, 2013.
1066ꢀ5285/13/6205ꢀ1232 © 2013 Springer Science+Business Media, Inc.

2ꢀArylꢀ or 2ꢀhetarylꢀ1ꢀhydroxyimidazoles
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013
1233
the reaction of aliphatic 1,2ꢀhydroxylamino oximes with
arylglyoxals under rather mild conditions led to 2ꢀaroylꢀ
1ꢀhydroxyimidazoles through the formation of the interꢀ
mediate бꢀaroylnitrones.20
cation of the starting nitrone. The experiments perꢀ
formed have shown that the use of acetic acid for the
cyclization of nitrones to imidazole derivatives gave the
best results.
We synthesized ꢀarylnitrones 5c and 6c based on comꢀ
pounds 1 and 2 and pꢀchlorobenzaldehyde 4c and studied
a possibility of their cyclization to the corresponding 2ꢀ(4ꢀ
chlorophenyl)ꢀ1ꢀhydroxyꢀ4,5ꢀdialkylimidazoles 9c and
10c. The solvents differing in chemical and solvation propꢀ
erties, but having close boiling points such as pyridine,
nꢀbutanol, toluene, acetic acid (b.p. 115.5, 117, 110.6,
and 118 C, respectively23) were used to carry out the
cyclization. The solutions of nitrones 5c and 6c were
refluxed in the listed solvents for 3 h, then the solvent was
evaporated in vacuo of a waterꢀjet pump, the residue was
analyzed by 1H NMR spectroscopy. Both nitrones apꢀ
peared to undergo no any transformations upon reflux in
pyridine and nꢀbutanol. Nitrone 5c after heating in toluꢀ
ene did not change, either, whereas heating of nitrone 6c
in toluene for 3 h resulted in obtaining a complex mixture
of products, out of which only the starting nitrone 6c,
pꢀchlorobenzaldehyde and cyclohexenꢀ3ꢀone oximes were
identified by 1H NMR spectroscopy and GLCꢀMS spectroꢀ
metry. The reaction mixtures obtained by reflux of both
nitrones 5c and 6c in acetic acid contained, according
to the 1H NMR spectroscopic data, the starting comꢀ
pounds (~30%) and the corresponding 2ꢀ(4ꢀchloroꢀ
phenyl)ꢀ1ꢀhydroxyꢀ4,5ꢀdialkylimidazoles 9c and 10c
(~70%). When the solutions of nitrones 5c and 6c in
acetic acid were reflux for a longer time (8 h), they
were virtually completely converted to the correspondꢀ
ing imidazole derivatives. Nitrones obtained from comꢀ
pound 1 and benzaldehyde 4a, pꢀnitrobenzaldehyde 4d
and vanillin 4i were refluxed in acetic acid for 8—20 h
to be virtually completely converted to the correspondꢀ
ing 1ꢀhydroxyꢀ2ꢀarylimidazoles 9a,d,i. Reflux of nitroꢀ
ne 5c in formic or trifluoroacetic acid led to the resinifiꢀ
In this connection, we studied the reaction of hydroxylꢀ
amino oximes 1—3 with aromatic and heteroaromatic
aldehydes in acetic acid in order to prepare the correꢀ
sponding imidazoles without isolation of ꢀaryl(heteroꢀ
aryl)nitrones 5—7 (see Scheme 1). Reflux of the equimoꢀ
lar amounts of the starting 1,2ꢀhydroxylamino oximes 1—3
and aldehydes 4a—i in acetic acid was carried out until the
starting aldehyde and/or nitrone were completely conꢀ
sumed (TLC monitoring). The yields of 2ꢀaryl(heteroaryl)ꢀ
1ꢀhydroxyꢀ4,5ꢀdialkylimidazoles 9a—i, 10a—i, and 11d,h
were 55—92%. The reaction of 1,2ꢀhydroxylamino oximes
1 and 2 with aldehydes containing electronꢀdonating subꢀ
stituents was slower and accompanied by the formation of
the resinꢀlike compounds.
2ꢀAryl(hetaryl)ꢀ1ꢀhydroxyimidazoles 9—11 were formꢀ
ed in the reaction of 1,2ꢀhydroxylamino oximes 1—3 with
aromatic or heteroaromatic aldehydes 4 in acetic acid as
a result of the intramolecular cyclization of nitrones 5—7
and subsequent dehydration of the intermediately formed
1ꢀhydroxyꢀ3ꢀimidazoline 3ꢀoxides 8 (see Ref. 20). Since
imidazoles 9—11 formed in the dehydration reaction of
the intermediate 1ꢀhydroxyꢀ3ꢀimidazoline 3ꢀoxides 8 are
symmetrically substituted, it is impossible to determine,
which pathway follows the dehydration: the pathway a or
the pathway b (Scheme 2). The pathway a seems the most
probable when the aryl substituent contains a rather strong
electronꢀwithdrawing group. Its presence leads to the inꢀ
crease in the acidity of the hydrogen atom at the second
carbon atom of the imidazoline ring and, therefore, to the
easy dehydration of 3ꢀimidazoline 3ꢀoxide protonated at
1ꢀhydroxy group with the formation of 4Hꢀimidazole
1ꢀoxide 12, which rapidly isomerizes to 1ꢀhydroxyimidꢀ
azole 9—11. The pathway b cannot be excluded, either:
Scheme 2

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013
Selivanov and Tikhonov
Scheme 3
initially the Nꢀoxide oxygen atom of imidazoline 8 is proꢀ
tonated, followed by the isomerization to 1,3ꢀdihydroxyꢀ
4ꢀimidazoline 13, whose dehydration can occur with inꢀ
volvement of one of the two hydroxy groups with the forꢀ
mation of isomeric imidazoles in the case if R1  R2.
In our opinion, the question which pathway follows
the dehydration of imidazoline 8 can be answered by carꢀ
rying out the reaction of unsymmetric derivatives, in parꢀ
ticular, alkylaromatic 1,2ꢀhydroxylamino oxime 14 (antiꢀ
isomer) with benzaldehyde derivative under the selected
conditions. The 1H NMR spectroscopic data showed that
the reaction of 1,2ꢀhydroxylamino oxime 14 with 4ꢀnitroꢀ
benzaldehyde 4d in refluxing acetic acid for 6 h gave
a mixture of isomeric products: 1ꢀhydroxyꢀ4ꢀmethylꢀ2ꢀ
(4ꢀnitrophenyl)ꢀ5ꢀphenylimidazole (15) and 1ꢀhydroxyꢀ
5ꢀmethylꢀ2ꢀ(4ꢀnitrophenyl)ꢀ4ꢀphenylimidazole (16) in
the ratio 1 : 2.3 (Scheme 3).
fluenced by the substituents at positions 4 and 5 of the
imidazoline ring.
In conclusion, was showed that ꢀarylꢀ and ꢀhetꢀ
arylnitrones formed in the reaction of aliphatic 1,2ꢀhydrꢀ
oxylamino oximes bearing the hydroxylamino group at
the secondary carbon atom with aromatic and heteroaroꢀ
matic aldehydes underwent cyclization upon heating in
acetic acid with the formation of the corresponding
1ꢀhydroxyꢀ2ꢀarylꢀ and 1ꢀhydroxyꢀ2ꢀhetarylꢀ4,5ꢀdialkylꢀ
imidazoles. The synthesis of 1ꢀhydroxyꢀ2ꢀarylꢀ and
1ꢀhydroxyꢀ2ꢀhetarylꢀ4,5ꢀdialkylimidazoles can be accomꢀ
plished by the reaction of the same 1,2ꢀhydroxylamino
oximes with aromatic or heteroaromatic aldehydes unꢀ
der conditions indicated above and without isolation of
ꢀaryl(hetaryl)nitrones.
Experimental
Compound 16 was obtained by the reaction of 2ꢀhydrꢀ
oxyiminoꢀ1ꢀphenylpropanꢀ1ꢀone (17) with aldehyde 4d
and ammonium acetate in ethanol12 (Scheme 4).
IR spectra of compounds in KBr pellets (concentration
0.25%) were recorded on a Bruker Vector 22 FTꢀIR spectromeꢀ
ter. GLCꢀMS spectra were recorded on a Hewlett Pakard
G1800A instrument consisting of an HP 5890 series II chroꢀ
Scheme 4
1
matograph and an HP 5971 mass selective detector. H NMR
spectra were recorded on a Bruker AMꢀ400 spectrometer
(400.136 MHz), using signals of residual protons of the solvent
(DMSOꢀd6 at  2.50, CD3OD at  3.34, respectively) as referꢀ
ences. Elemental analysis was performed on a Euro EA3000
automatic elemental CHNSꢀanalyzer. Melting points were deꢀ
termined on a Mettler Toledo apparatus and were not correctꢀ
ed. The reaction progress and the purity of obtained comꢀ
pounds were monitored by TLC on Silufol UVꢀ254 plates, eluꢀ
ent chloroform—methanol (10 : 1), visualization under UV light.
All the solvents were purified according to the standard proꢀ
cedures.
Acetates of the starting 1,2ꢀhydroxylamino oximes 1—3 were
obtained according to the known procedure.24
Nꢀ(Benzylidene)ꢀNꢀ(2ꢀhydroxyiminoꢀ1ꢀmethylpropyl)amine
Nꢀoxide (5a) was obtained according to the procedure described
earlier.21 The yield was 53%, m.p. 107 C (see Ref. 21: m.p.
108—110 C).
Nꢀ(2ꢀHydroxyiminoꢀ1ꢀmethylpropyl)ꢀNꢀ(4ꢀnitrobenzylidꢀ
ene)amine Nꢀoxide (5d) was obtained according to the procedure
described earlier.21 The yield was 95%, m.p. 160 C (see Ref. 21:
m.p. 157—158 C).
Eꢀisomer of 2ꢀhydroxyaminoꢀ1ꢀphenylpropanone oxime 14
was obtained according to the procedure given in the literature.25
The formation in the reaction of a mixture of 1ꢀhydrꢀ
oxyimidazoles 15 and 16 (see Scheme 3), in our opinion,
can indicate a predominant formation of the intermediate
1,3ꢀdihydroxyꢀ4ꢀimidazoline 13 (pathway b), whose rate
of dehydration involving one of the hydroxy groups is inꢀ

2ꢀArylꢀ or 2ꢀhetarylꢀ1ꢀhydroxyimidazoles
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013
1235
2ꢀHydroxyiminoꢀ1ꢀphenylpropaneꢀ1ꢀone 17 was obtained
according to the procedure given in the literature.26
the residue contained 36% of the starting nitrone, 60% of 2ꢀ(4ꢀ
chlorophenyl)ꢀ1ꢀhydroxyꢀ4,5ꢀdimethylimidazole 9c, and 3% of
pꢀchlorobenzaldehyde.
Synthesis of Nꢀ(2ꢀhydroxyiminoalkyl)ꢀꢀarylnitrones (5c,i, 6c)
(general procedure). A solution of aromatic aldehyde (10 mmol)
in minimum methanol was added to a solution of hydroxylamino
oxime acetate (1 or 2) (11 mmol) in methanol (15 mL) with
stirring. The mixture obtained was stirred for 4 h at ~20 C
(a precipitate began to form after 10—15 min) and kept for 16 h
without stirring. A precipitate of ꢀarylnitrone 5a—i, 6a—i was
filtered off, washed with minimum cold methanol, dried in air
until the weight was constant.
Cyclization of ꢀarylnitrones (general procedure A). A soluꢀ
tion of ꢀarylnitrone (5a,c,d,i, 6c) (10 mmol) in acetic acid
(25 mL) was refluxed until the starting compound was completeꢀ
ly consumed (8—20 h), TLC monitoring. The solvent was evapꢀ
orated in vacuo of a waterꢀjet pump. The residue was dissolved in
5% aqueous hydrochloric acid (50 mL). The solution obtained
was stirred for 2 h at ~20 C with activated charcoal (2 g), filꢀ
tered through a paper filter, and washed with water (2×10 mL).
Aqueous ammonia (concentration ~25%) was added to the filꢀ
trate cooled with icy water to рH ~8. A precipitate formed
was filtered off, washed with water (4×10 mL), diethyl ether
(2×5 mL), and dried in air until the weight was constant. This
procedure was used to obtain compounds 9a,c,d,i and 10c.
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀphenylimidazole (9a). The reacꢀ
tion time was 8 h, the yield was 89%, white crystals, m.p. 115 C
(see Ref. 12: m.p. 115 C).
Nꢀ(4ꢀChlorobenzylidene)ꢀNꢀ(2ꢀhydroxyiminoꢀ1ꢀmethylpropꢀ
yl)amine Nꢀoxide (5c). The yield was 86%, white crystals, m.p.
153 C. Found (%): C, 54.36; H, 5.39; N, 11.98. C11H13ClN2O2.
Calculated (%): C, 54.89; H, 5.44; N, 11.64. IR, /cm–1: 3171,
3114, 3069, 2999, 1590, 1488, 1446, 1300, 1143, 1087, 987, 952.
1H NMR (DMSOꢀd6), : 1.51 (d, 3 H, CH—CH3, J = 6.8 Hz);
1.77 (s, 3 H, N=C—CH3); 4.91 (q, 1 H, CH—CH3, J = 6.8 Hz); 7.50
(d, 2 H, HAr(3), HAr(5), J = 8.7 Hz); 8.04 (s, 1 H, Ar—CH=N);
8.30 (d, 2 H, HAr(2), HAr(6), J = 8.7 Hz); 11.04 (s, 1 H, N—OH).
Nꢀ(4ꢀHydroxyꢀ3ꢀmethoxybenzylidene)ꢀNꢀ(2ꢀhydroxyiminoꢀ
1ꢀmethylpropyl)amine Nꢀoxide (5i). The yield was 87%, white
crystals, m.p. 158 C. Found (%): C, 52.79; H, 6.62; N, 10.89.
C12H16N2O4•H2O. Calculated (%): C, 53.33; H, 6.71; N, 10.36.
IR, /cm–1: 3519, 2844, 2785, 1601, 1587, 1516, 1407, 1287,
2ꢀ(4ꢀChlorophenyl)ꢀ1ꢀhydroxyꢀ4,5ꢀdimethylimidazole (9c).
The reaction time was 8 h, the yield was 92%, white crystals,
m.p. 138 C (see Ref. 13: m.p. 201—202 C). Found (%): C, 59.59;
H, 4.96; N, 12.54. C11H11ClN2O. Calculated (%): C, 59.33;
H, 4.98; N, 12.58. IR, /cm–1: 3095, 2926, 2850, 1650, 1540,
1
1493, 1387, 1296, 1094, 832, 751. H NMR (CD3OD), : 2.21
1
1169, 1142, 1034, 945. H NMR (DMSOꢀd6), : 1.49 (d, 3 H,
(s, 3 H, CH3); 2.27 (s, 3 H, CH3); 7.52 (m, 2 H, HAr(3), HAr(5));
CH—CH3, J = 6.6 Hz); 1.77 (s, 3 H, N=C—CH3); 3.77 (s, 3 H,
OCH3); 4.80 (q, 1 H, CH—CH3, J = 6.6 Hz); 6.82 (d, 1 H,
HAr(5), J = 8.3 Hz); 7.56 (dd, 1 H, HAr(6), J = 1.9 Hz, J = 8.3 Hz);
7.79 (s, 1 H, Ar—CH=N); 8.19 (d, 1 H, HAr(2), J = 1.9 Hz);
9.61 (s, 1 H, Ar—OH); 10.97 (s, 1 H, N—OH).
8.18 (m, 2 H, HAr(2), HAr(6)).
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(4ꢀnitrophenyl)imidazole (9d).
The reaction time was 8 h, the yield was 79%, bright yellow
crystals, m.p. 220 C (with decomp.) (see Ref. 13: m.p. 221—223 C).
Found (%): C, 56.58; H, 4.62; N, 17.95. C11H11N3O3. Calculatꢀ
ed (%): C, 56.65; H, 4.75; N, 18.02. IR, /cm–1: 3432, 1640,
1595, 1515, 1462, 1344, 1327, 1286, 1091, 855, 752. H NMR
(DMSOꢀd6), : 2.09 (s, 3 H, CH3); 2.11 (s, 3 H, CH3); 8.26
(m, 4 H, Ar—H); 12.32 (br.s, 1 H, N—OH).
Nꢀ(4ꢀChlorobenzylidene)ꢀNꢀ(2ꢀhydroxyiminocyclohexyl)ꢀ
amine Nꢀoxide (6c). The yield was 75%, fluffy white crystals, m.p.
158 C. Found (%): C, 58.39; H, 5.55; N, 10.64. C13H15ClN2O2.
Calculated (%): C, 58.54; H, 5.67; N, 10.50. IR, /cm–1: 3254,
1
1
2948, 2865, 1588, 1576, 1485, 1454, 1158, 1089, 943. H NMR
1ꢀHydroxyꢀ2ꢀ(4ꢀhydroxyꢀ3ꢀmethoxyphenyl)ꢀ4,5ꢀdimethylꢀ
imidazole (9i). The reaction time was 20 h, the yield was 77%,
white crystals, m.p. 245 C (with decomp.) (see Ref. 13: m.p.
258—259 C). Found (%): C, 61.22; H, 6.13; N, 12.04. C12H14N2O3.
Calculated (%): C, 61.53; H, 6.02; N, 11.96. IR, /cm–1: 3427,
2962, 2924, 1649, 1551, 1506, 1462, 1440, 1280, 1225, 1095,
(DMSOꢀd6), : 1.56, 1.93, 2.28, 2.44, 2.72 (all m, 8 H, cycloꢀ
hexane ring); 4.80 (dd, 1 H, NCH—CH2, J = 5.0 Hz, J = 7.5 Hz);
7.48 (d, 2 H, HAr(3), HAr(5), J = 8.8 Hz); 7.88 (s, 1 H,
Ar—CH=N); 8.29 (d, 2 H, HAr(2), HAr(6), J = 8.8 Hz); 11.00
(s, 1 H, N—OH).
1
Selection of solvents for cyclization of ꢀarylnitrones. A soluꢀ
tion of compound 6c (0.5 mmol) in toluene (10 mL) was refluxed
for 3 h. The solvent was evaporated in vacuo of a waterꢀjet pump.
According to the 1H NMR spectroscopic and GLCꢀMS spectroꢀ
metric data, the residue contained 45% of the starting nitrone,
15% of paraꢀchlorobenzaldehyde oxime, 22% of cyclohexenꢀ3ꢀ
one oxime, and a number of unidentified compounds.
A solution of compound 6c (0.5 mmol) in acetic acid (10 mL)
was refluxed for 3 h. The solvent was evaporated in vacuo of
a waterꢀjet pump. According to the 1H NMR spectroscopic data,
the residue contained 32% of the starting nitrone and 66% of
2ꢀ(4ꢀchlorophenyl)ꢀ1ꢀhydroxyꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10c).
1038, 820, 735. H NMR (DMSOꢀd6), : 2.03 (s, 3 H, CH3);
2.07 (s, 3 H, CH3); 3.77 (s, 3 H, OCH3); 6.79 (d, 1 H, HAr(5),
J = 8.4 Hz); 7.53 (br.s, 1 H, HAr(6)); 7.68 (br.s, 1 H, HAr(2));
9.27 (br.s, 1 H, Ar—OH); 11.80 (br.s, 1 H, N—OH).
2ꢀ(4ꢀChlorophenyl)ꢀ1ꢀhydroxyꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10c). The reaction time was 10 h, the yield was 89%,
white crystals, m.p. 221 C. Found (%): C, 62.05; H, 5.26;
N, 11.15. C13H13ClN2O. Calculated (%): C, 62.78; H, 5.27;
N, 11.26. IR, /cm–1: 2938, 2854, 1651, 1540, 1496, 1391, 1359,
1
1298, 1093, 1013, 830, 796, 750. H NMR (DMSOꢀd6), : 1.73
(br.s, 4 H, CH2—CH2); 2.45 (br.s, 4 H, C=C—CH2); 7.46 (d, 2 H,
HAr(3), HAr(5), J = 8.7 Hz); 8.03 (br.s, 2 H, HAr(2), HAr(6));
11.86 (br.s, 1 H, N—OH).
A solution of compound 5c (0.5 mmol) in toluene (10 mL)
(pyridine, nꢀbutanol) was refluxed for 3 h. The solvent was evapꢀ
orated in vacuo of a waterꢀjet pump. According to the 1H NMR
spectroscopic data, the residue was the starting nitrone 5c.
A solution of compound 5c (0.5 mmol) in acetic acid (10 mL)
was refluxed for 3 h. The solvent was evaporated in vacuo of
a waterꢀjet pump. According to the 1H NMR spectroscopic data,
Reaction of 1,2ꢀhydroxyamino oxime acetates 1—3 with aroꢀ
matic (heteroaromatic) aldehydes (general procedure B). A soluꢀ
tion of 1,2ꢀhydroxylamino oxime 1—3 (10 mmol) and aromatic
(heteroaromatic) (10 mmol) aldehyde 4a—i in acetic acid
(25 mL) was refluxed until the starting compounds were comꢀ
pletely consumed (8—20 h), TLC monitoring. The solvent was
evaporated in vacuo of a waterꢀjet pump. The residue was disꢀ

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013
Selivanov and Tikhonov
solved in 5% aq. hydrochloric acid (50 mL) with slight heating
(below 50 C). The solution obtained was stirred for 2 h at ~20 C
with activated charcoal (3 g). The charcoal was filtered off
through a paper filter, washed with water on the filter (2×10 mL).
Aqueous ammonia (concentration ~25%) was added to the filꢀ
trate cooled with icy water to рH ~8. A precipitate formed
was filtered off, washed with water (4×10 mL), diethyl ether
(2×5 mL), and dried in air until the weight was constant.
This procedure was used to obtain 1ꢀhydroxyimidazole deꢀ
rivatives 9a—i, 10a—i, 11d,h.
J = 7.8 Hz, J = 1.4 Hz); 8.57 (d, 1 H, HРу(6), J = 4.8 Hz); 9.05
(br.s, 1 H, HРу(3)); 12.62 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ2ꢀ(4ꢀhydroxyꢀ3ꢀmethoxyphenyl)ꢀ4,5ꢀdimethylimꢀ
idazole (9i). The reaction time was 20 h, the yield was 78%.
1ꢀHydroxyꢀ2ꢀphenylꢀ4,5,6,7ꢀtetrahydrobenzimidazole (10a).
The reaction time was 10 h, the yield was 73%, white crystals, m.p.
119 C. Found (%): C, 72.56; H, 6.36; N, 13.33. C13H14N2O.
Calculated (%): C, 72.87; H, 6.59; N, 13.07. IR, /cm–1: 3070,
2942, 2856, 2767, 2686, 1652, 1602, 1540, 1500, 1442, 1359, 1298,
1213, 794, 760, 749, 687. 1H NMR (CD3OD), : 1.91 (br.s, 4 H,
CH2—CH2); 2.65 (br.s, 4 H, C=C—CH2); 7.52 (m, 3 H, HAr(3),
HAr(4), HAr(5)); 8.20 (d, 2 H, HAr(2), HAr(6), J = 7.0 Hz).
1ꢀHydroxyꢀ2ꢀ(4ꢀmethoxyphenyl)ꢀ4,5,6,7ꢀtetrahydrobenzꢀ
imidazole (10b). The reaction time was 18 h, the yield was 55%,
white crystals, m.p. 186 C. Found (%): C, 64.19; H, 6.80;
N, 10.64. C14H16N2O2•H2O. Calculated (%): C, 64.10; H, 6.92;
N, 10.68. IR, /cm–1: 2934, 2852, 2835, 1655, 1611, 1552, 1506,
1464, 1440, 1300, 1256, 1186, 1042, 830, 746. 1H NMR (CD3OD),
: 1.89 (br.s, 4 H, CH2—CH2); 2.62 (br.s, 4 H, C=C—CH2);
3.88 (s, 3 H, O—CH3); 7.07 (d, 2 H, HAr(3), HAr(5), J = 8.7 Hz);
8.14 (d, 2 H, HAr(2), HAr(6), J = 8.7 Hz).
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀphenylimidazole (9a). The reacꢀ
tion time was 8 h, the yield was 86%.
1ꢀHydroxyꢀ2ꢀ(4ꢀmethoxyphenyl)ꢀ4,5ꢀdimethylimidazole (9b).
The reaction time was 20 h, the yield was 55%, white crystals, m.p.
114 C. Found (%): C, 60.89; H, 6.94; N, 11.76. C12H14N2O2•
•H2O. Calculated (%): C, 61.00; H, 6.83; N, 11.86. IR, /cm–1
:
3066, 2922, 2840, 1653, 1614, 1554, 1504, 1464, 1302, 1255,
1180, 1034, 832, 750. 1H NMR (CD3OD), : 2.21 (s, 3 H,
CH3); 2.25 (s, 3 H, CH3); 3.88 (s, 3 H, O—CH3); 7.07 (d, 2 H,
HAr(3), HAr(5), J = 8.9 Hz); 8.14 (d, 2 H, HAr(2), HAr(6)),
J = 8.9 Hz).
2ꢀ(4ꢀChlorophenyl)ꢀ1ꢀhydroxyꢀ4,5ꢀdimethylimidazole (9c).
The reaction time was 12 h, the yield was 88%.
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(4ꢀnitrophenyl)imidazole (9d).
The reaction time was 10 h, the yield was 90%.
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(3ꢀnitrophenyl)imidazole (9e).
The reaction time was 10 h, the yield was 78%, yellow crystals, m.p.
189 C. Found (%): C, 52.11; H, 5.13; N, 16.58. C11H11N3O3•
2ꢀ(4ꢀChlorophenyl)ꢀ1ꢀhydroxyꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10c). The reaction time was 12 h, the yield was 87%.
1ꢀHydroxyꢀ2ꢀ(4ꢀnitrophenyl)ꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10d). The reaction time was 6 h, the yield was 79%, bright
yellow crystals, m.p. 244 C. Found (%): C, 60.28; H, 5.08; N, 16.20.
C13H13N3O3. Calculated (%): C, 60.22; H, 5.05; N, 16.21. IR,
/cm–1: 2944, 1645, 1598, 1519, 1437, 1337, 856. 1H NMR
(DMSOꢀd6), : 1.75 (br.s, 4 H, CH2—CH2); 2.46 (br.s, 4 H,
C=C—CH2); 8.26 (m, 4 H, Ar—H); 12.33 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ2ꢀ(3ꢀnitrophenyl)ꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10e). The reaction time was 6 h, the yield was 93%, light
yellow crystals, m.p. 230 C. Found (%): C, 59.78; H, 5.03;
N, 16.28. C13H13N3O3. Calculated (%): C, 60.22; H, 5.05;
N, 16.21. IR, /cm–1: 3110, 2949, 1691, 1649, 1538, 1349, 1303,
743. 1H NMR (DMSOꢀd6), : 1.72 (br.s, 4 H, CH2—CH2); 2.46
(m, 4 H, C=C—CH2); 7.65 (t, 1 H, HAr(5), J = 8.0 Hz); 8.04
(dd, 1 H, HAr(4), J = 1.6 Hz, J = 8.0 Hz); 8.30 (d, 1 H, HAr(6),
J = 8.0 Hz); 8.68 (br.s, 1 H, HAr(2)); 12.67 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ2ꢀ(2ꢀnitrophenyl)ꢀ4,5,6,7ꢀtetrahydrobenzimidꢀ
azole (10f). The reaction time was 10 h, the yield was 60%,
bright yellow crystals, m.p. 263 C. Found (%): C, 60.45; H, 5.07;
N, 16.29. C13H13N3O3. Calculated (%): C, 60.22; H, 5.05;
N, 16.21. IR, /cm–1: 3435, 2940, 2856, 1611, 1574, 1530, 1356,
•H2O. Calculated (%): C, 52.59; H, 5.22; N, 16.72. IR, /cm–1
:
1
3421, 1646, 1546, 1525, 1348, 1306. H NMR (DMSOꢀd6), :
2.08 (s, 3 H, CH3); 2.10 (s, 3 H, CH3); 7.69 (t, 1 H, HAr(5),
J = 8.2 Hz); 8.14 (dd, 1 H, HAr(4), J = 1.9 Hz, J = 8.2 Hz); 8.38
(br.s, 1 H, HAr(6), HAr(2)); 8.72 (br.s, 1 H, HAr(2), HAr(6));
12.33 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(2ꢀnitrophenyl)imidazole (9f).
The reaction time was 12 h, the yield was 69%, light yellow
crystals, m.p. 234 C (see Ref. 13: m.p. 243—245 C). Found (%):
C, 56.96; H, 4.88; N, 18.11. C11H11N3O3. Calculated (%):
C, 56.65; H, 4.75; N, 18.02. IR, /cm–1: 3435, 3085, 2926, 2886,
1613, 1530, 1353, 857, 788, 711. 1H NMR (DMSOꢀd6), : 2.03
(s, 3 H, CH3); 2.06 (s, 3 H, CH3); 7.63 (t, 1 H, HAr(4), J = 7.9 Hz);
7.70 (br.s, 1 H, HAr(6), J = 7.3 Hz); 7.77 (dd, 1 H, HAr(5),
J = 7.3 Hz, J = 7.9 Hz); 7.96 (d, 1 H, HAr(3), J = 7.9 Hz); 11.67
(br.s, 1 H, N—OH).
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(pyridinꢀ4ꢀyl)imidazole (9g). The
reaction time was 10 h, the yield was 61%, white crystals, m.p.
150 C (see Ref. 13: m.p. 187—190 C). Found (%): C, 63.36;
H, 5.82; N, 22.26. C10H11N3O. Calculated (%): C, 63.48;
H, 5.86; N, 22.21. IR, /cm–1: 1648, 1604, 1552, 1542, 1410,
1295, 1228, 1001, 825, 816, 757. 1H NMR (DMSOꢀd6), : 2.06
(s, 3 H, CH3); 2.09 (s, 3 H, CH3); 7.95 (d, 2 H, HРу(2), HРу(6),
J = 5.3 Hz); 8.56 (d, 2 H, HРу(3), HРу(5), J = 5.3 Hz); 12.01
(br.s, 1 H, N—OH).
1ꢀHydroxyꢀ4,5ꢀdimethylꢀ2ꢀ(pyridinꢀ2ꢀyl)imidazole (9h). The
reaction time was 18 h, the yield was 90%, white crystals, m.p.
164 C. Found (%): C, 62.00; H, 5.90; N, 21.38. C10H11N3O•
•0.25H2O. Calculated (%): C, 62.00; H, 5.98; N, 21.69. IR,
/cm–1: 3377, 3046, 2921, 2857, 1639, 1589, 1525, 1492, 1447,
1310, 1231, 1154, 1116, 991, 815, 795, 744. 1H NMR (DMSOꢀd6),
: 2.06 (s, 3 H, CH3); 2.15 (s, 3 H, CH3); 7.32 (ddd, 1 H, HPy(5),
J = 1.4 Hz, J = 4.8 Hz, J = 7.8 Hz); 7.88 (dt, 1 H, HРу(4),
1
1304, 859, 785, 714. H NMR (DMSOꢀd6), : 1.73 (br.s, 4 H,
CH2—CH2); 2.46 (br.s, 4 H, C=C—CH2); 7.62 (dd, 1 H, HAr(4),
J = 7.7 Hz, J = 8.1 Hz); 7.75 (m, 2 H, HAr(5), HAr(6); 7.96
(d, 1 H, HAr(3), J = 8.1 Hz); 11.63 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ2ꢀ(pyridinꢀ4ꢀyl)ꢀ4,5,6,7ꢀtetrahydrobenzimidazole
(10g). The reaction time was 24 h, the yield was 90%, white
crystals, m.p. 203 C. Found (%): C, 64.48; H, 6.08; N, 18.34.
C12H13N3O•0.5H2O. Calculated (%): C, 64.27; H, 6.29; N, 18.74.
IR, /cm–1: 2936, 2847, 1598, 1550, 1440, 1406, 1354, 1208,
829, 798, 755. 1H NMR (CD3OD), : 1.91 (br.s, 4 H, CH2—CH2);
2.65 (br.s, 4 H, C=C—CH2); 8.20 (d, 2 H, HPy(2), HPy(6),
J = 6.0 Hz); 8.65 (d, 2 H, HРу(3), HРу(5), J = 6.0 Hz).
1ꢀHydroxyꢀ2ꢀ(pyridinꢀ2ꢀyl)ꢀ4,5,6,7ꢀtetrahydrobenzimidazole
(10h). The reaction time was 18 h, the yield was 79%, white
crystals, m.p. 170 C. Found (%): C, 67.14; H, 6.29; N, 19.54.
C12H13N3O. Calculated (%): C, 66.96; H, 6.09; N, 19.52. IR,
/cm–1: 3051, 2940, 2924, 2852, 1631, 1588, 1517, 1488, 1441,

2ꢀArylꢀ or 2ꢀhetarylꢀ1ꢀhydroxyimidazoles
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013
1237
1
1298, 1101, 791, 733, 660. H NMR (CD3OD), : 1.90 (br.s,
References
4 H, CH2—CH2); 2.67 (br.s, 4 H, C=C—CH2); 7.38 (ddd, 1 H,
HPy(5), J = 1.1 Hz, J = 4.8 Hz, J = 7.8 Hz); 7.93 (dt, 1 H,
HPy(4), J = 7.8 Hz, J = 1.1 Hz); 8.64 (d, 1 H, HРу(6), J = 4.8 Hz);
8.88 (d, 1 H, HPy(3), J = 7.8 Hz).
1. M. R. Grimmett, in Comprehensive Heterocyclic Chemistry.
The Structure, Reactions, Synthesis and Uses of Heterocyclic
Compounds, Eds A. R. Katritzky, C. W. Rees, Pergamon
Press, Oxford—New York—Toronto—Sydney—Paris—Frankꢀ
furt, 1984, vol. 5, p. 405.
2. G. S. Shaimardanova, R. A. Kamburg, R. P. Evstigneeva,
N. V. Sergeeva, Khim. Farm. Zh., 1992, 26, No. 3, 31 [Pharm.
Chem. J. (Engl. Transl.), 1992, 26, No. 3].
3. M. Boiani, M. Gonzalez, MiniꢀRev. Med. Chem., 2005, 5, 409.
4. L. M. Junker, J. Clardy, Antimicrob. Agents Chemother., 2007,
51, 3582.
5. G. V. Nikitina, M. S. Pevzner, Chem. Heterocycl. Compd.
(Engl. Transl.), 1993, 127 [Khim. Geterotsikl. Soedin., 1993, 147].
6. R. Breslow, S. Chung, Tetrahedron Lett., 1989, 30, 4353.
7. (a) J. F. Callahan, J. L. Burgess, J. A. Fornwald, J. Med.
Chem., 2002, 45, 999; (b) S. A. Layfer, H.ꢀG. Striegel, G. K.
Wagner, J. Med. Chem., 2002, 45, 4695.
1ꢀHydroxyꢀ2ꢀ(4ꢀhydroxyꢀ3ꢀmethoxyphenyl)ꢀ4,5,6,7ꢀtetraꢀ
hydrobenzimidazole (10i). The reaction time was 24 h, the yield
was 85%, white crystals, m.p. 241 C. Found (%): C, 64.45;
H, 6.29; N, 10.54. C14H16N2O3. Calculated (%): C, 64.60; H, 6.20;
N, 10.76. IR, /cm–1: 2944, 2856, 1651, 1547, 1508, 1280, 1227,
1141, 1041, 764. 1H NMR (DMSOꢀd6), : 1.70 (br.s, 4 H,
CH2—CH2); 2.42 (br.s, 4 H, C=C—CH2); 3.76 (s, 3 H, OCH3);
6.78 (d, 1 H, HAr(5), J = 8.0 Hz); 7.50 (br.s, 1 H, HAr(2), HAr(6));
7.62 (br.s, 1 H, HAr(2), HAr(6)); 9.34 (br.s, 1 H, Ar—OH); 11.94
(br.s, 1 H, N—OH).
1ꢀHydroxyꢀ2ꢀ(4ꢀnitrophenyl)ꢀ4,5ꢀpentamethyleneimidazole
(11d). The reaction time was 8 h, the yield was 89%, dark yellow
crystals, m.p. 218 C. Found (%): C, 61.06; H, 5.45; N, 14.86.
C14H15N3O3. Calculated (%): C, 61.53; H, 5.53; N, 15.38. IR,
/cm–1: 2929, 2853, 1635, 1597, 1518, 1449, 1340, 1109, 853.
1H NMR (DMSOꢀd6), : 1.66 (br.s, 4 H, CH2—CH2); 1.77
(br.s, 2 H, CH2), 2.65 (m, 4 H, C=C—CH2); 8.26 (m, 4 H, Ar—H);
12.10 (br.s, 1 H, N—OH).
8. B. L. Eriksen, P. Vedso, S. Morel, M. Begtrup, J. Org. Chem.,
1998, 63, 12.
9. K. Akagane, F. J. Allan, G. G. Allan, T. Friberg, S. O.
Muircheartaigh, J. B. Thomson, Bull. Chem. Soc. Jpn, 1969,
42, 3204; Chem. Abstr., 1972, 77, 126496z.
1ꢀHydroxyꢀ2ꢀ(pyridinꢀ2ꢀyl)ꢀ4,5ꢀpentamethyleneimidazole
(11h). The reaction time was 16 h, the yield was 63%, white
crystals, m.p. 171 C. Found (%): C, 62.82; H, 6.81; N, 16.98.
C13H15N3O•H2O. Calculated (%): C, 63.14; H, 6.93; N, 16.99.
IR, /cm–1: 3050, 2919, 2846, 1626, 1588, 1521, 1486, 1437,
1248, 1051, 790. 1H NMR (DMSOꢀd6), : 1.62 (m, 4 H,
CH2—CH2); 1.74 (m, 2 H, CH2); 2.67 (m, 4 H, C=C—CH2);
7.31 (ddd, 1 H, HРу(5), J = 1.5 Hz, J = 4.6 Hz, J = 7.7 Hz); 7.87
(dt, 1 H, HРу(4), J = 7.7 Hz, J = 1.5 Hz); 8.55 (d, 1 H, HРу(6),
J = 4.6 Hz); 8.99 (br.s, 1 H, HРу(3)); 12.73 (br.s, 1 H, N—OH).
1ꢀHydroxyꢀ4ꢀmethylꢀ2ꢀ(4ꢀnitrophenyl)ꢀ5ꢀphenylimidazole
(15) and 1ꢀhydroxyꢀ5ꢀmethylꢀ2ꢀ(4ꢀnitrophenyl)ꢀ4ꢀphenylimidaꢀ
zole (16) were obtained as a mixture of isomers (ratio 15 : 16 =
10. S. Havez, M. Begtrup, P. Vedso, K. Andersen, T. Ruhland,
Synthesis, 2001, 909.
11. G. Laus, J. Stadlwiezer, W. Klotzer, Synthesis, 1989, 773.
12. Pat. FRG 2254474; Chem. Abstr., 1973, 79, 42506g.
13. K. Akagane, G. G. Allan, C. S. Chopra, T. Friberg, T. Matꢀ
tila, S. Omuircheartaigh, J. B. Thomson, Suomen Kemiꢀ
stilehti, 1972, 45B, 223; Chem. Abstr., 1972, 77, 126496z.
14. A. Tanaka, K. Ito, S. Nishino, Y. Motoyama, H. Takasugi,
Chem. Pharm. Bull., 1992, 40, 3206.
15. K. Akagane, G. G. Allan, Chem. Ind. (London), 1974, 38.
16. M. Begtrup, P. Vedso, J. Chem. Soc., Perkin Trans. 1, 1995, 243.
17. L. B. Volodarsky, A. N. Lisack, V. A. Koptyug, Tetrahedron
Lett., 1965, 1565.
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(Engl. Transl.), 1967, 713 [Khim. Geterotsikl. Soedin., 1967, 904].
19. Yu. G. Putsykin, L. B. Volodarskii, Izv. Sib. Otd. Akad. Nauk
SSSR, Ser. Khim. Nauk (Engl. Transl.), 1969, No. 4, 86.
20. S. A. Amitina, A. Ya. Tikhonov, I. A. Grigor´ev, Yu. V. Gatiꢀ
lov, B. A. Selivanov, Chem. Heterocycl. Compd. (Engl. Transl.),
2009, 691 [Khim. Geterotsikl. Soedin., 2009, 868].
21. Yu. G. Putsykin, L. B. Volodarskii, Izv. Sib. Otd. Akad. Nauk.
SSSR, Ser. Khim. Nauk (Engl. Transl.), 1968, No. 4, 101.
22. L. B. Volodarskii, Yu. G. Putsykin, Zh. Org. Khim., 1967, 3,
1686 [J. Org. Chem. USSR (Engl. Transl.), 1967, 3].
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New York—London—Sydney—Toronto, 1972, p. 11.
24. L. N. Grigor´eva, L. B. Volodarskii, A. Ya. Tikhonov, Izv.
Sib. Otd. Akad. Nauk. SSSR, Ser. Khim. Nauk (Engl. Transl.),
1989, No. 3, 125.
1
= 1 : 2.3 according to the H NMR spectroscopic data) by the
reaction of compound 14 with aldehyde 4d according to the
procedure given above. The yield of the mixture of compounds
15 and 16 was 70%. The 1H NMR spectrum of the predominant
1
isomer 16 is given below. H NMR spectrum of the minor isoꢀ
mer of imidazole 15 (DMSOꢀd6), : 2.27 (s, 3 H, CH3); 7.51
(t, 2 H, HAr(3), HAr(5), J = 7.6 Hz); 7.61 (d, 2 H, HAr(2), HAr(6)),
J = 7.6 Hz); other signals are overlapped with the strong signals
of the predominant isomer.
1ꢀHydroxyꢀ5ꢀmethylꢀ2ꢀ(4ꢀnitrophenyl)ꢀ4ꢀphenylimidazole
(16). A mixture of compound 17 (1.63 g, 10 mmol), aldehyde 4d
(1.51 g, 10 mmol), and ammonium acetate (1.54 g, 20 mmol)
was refluxed for 2 h in ethanol (40 mL). The solvent was evapoꢀ
rated in vacuo, the residue was triturated with water (50 mL).
A precipitate was filtered off, washed with water (3×10 mL),
dried in air until the weight was constant. The yield was 2.06 g
(70%). Yellow crystals, m.p. 211 C. Found (%): C, 61.71;
H, 4.90; N, 13.04. C16H13N3O3• H2O. Calculated (%): C, 61.34;
H, 4.83; N, 13.41. IR, /cm–1: 1595, 1526, 1348, 1333, 1209,
853. 1H NMR (DMSOꢀd6), : 2.44 (s, 3 H, CH3); 7.28 (t, 1 H,
HAr(4), J = 7.6 Hz); 7.43 (t, 2 H, HAr(3), HAr(5), J = 7.6 Hz);
7.73 (d, 2 H, HAr(2), HAr(6), J = 7.6 Hz); 8.31 (m, 2 H, HAr(2),
HAr(6)); 8.38 (m, 2 H, HAr(3), HAr(5)); 12.30 (br.s, 1 H, N—OH).
25. L. B. Volodarskii, V. A. Koptyug, A. N. Lysak, J. Org. Chem.
USSR (Engl. Transl.), 1966, 2, 110 [Zh. Org. Khim., 1966,
2, 114].
26. US Pat. 2248035; Chem. Abstr., 1941, 35, 6265.
The authors are grateful to S. A. Amitina for the help
in carrying out some experiments.
Received December 14, 2011;
in revised form February 18, 2013