N-amino derivatives of condensed imidazole systems

Article abstract of DOI:10.1023/B:COHC.0000008260.31382.77

The previously unknown 1-amino- and 3-aminonaphtho[1,2-d]imidazoles, 1-aminonaphtho[2,3-d]-imidazole, 1-aminophenanthro[9,10-d]imidazole and the N-amino-N′-methylimidazolium picrates corresponding to them have been obtained by direct amination of a series of condensed imidazoles with O-picrylhydroxylamine. An X-ray structural investigation of 1-amino-3-methylnaphtho[1,2-d]-imidazolium picrate showed that, in difference to 1-aminobenzimidazolium salts, a conformation exists in it in which the hydrogen atoms of the N-NH₂ group are directed to the side of the meso carbon atom.

Full text of DOI:10.1023/B:COHC.0000008260.31382.77

Chemistry of Heterocyclic Compounds, Vol. 39, No. 9, 2003
N-AMINO DERIVATIVES OF
CONDENSED IMIDAZOLE SYSTEMS
M. G. Koroleva1, O. V. Dyablo1, A. F. Pozharskii1, and Z. A. Starikova2
The previously unknown 1-amino- and 3-aminonaphtho[1,2-d]imidazoles, 1-aminonaphtho[2,3-d]-
imidazole, 1-aminophenanthro[9,10-d]imidazole and the N-amino-N'-methylimidazolium picrates
corresponding to them have been obtained by direct amination of a series of condensed imidazoles with
O-picrylhydroxylamine. An X-ray structural investigation of 1-amino-3-methylnaphtho[1,2-d]-
imidazolium picrate showed that, in difference to 1-aminobenzimidazolium salts, a conformation
exists in it in which the hydrogen atoms of the N–NH2 group are directed to the side of the meso carbon
atom.
Keywords: N-aminoazoles, O-picrylhydroxylamine, conformations of the N-amino group, X-ray
structural analysis, electrophilic amination.
It is known that the amino group in N-amino azoles is in a pyramidal configuration (sp3-hybridization of
the nitrogen atom) and several types of conformation are shown for it differing in the deflection angle relative to
the N–(NH2) bond [1,2]. For example, in 1-aminobenzimidazole derivatives the amino group is usually folded in
such a way that the unshared electron pair of the nitrogen atom lies exactly in the plane of the cyclic system and
may be turned either towards the -carbon atom (conformation 1A) or in the direction of the benzene ring (1B).
µ
It was shown by X-ray structural analysis that in the solid form both for 1-aminobenzimidazole itself [2] and for
its quaternary salts 2a,b [3] conformation 1A exists which is presumably stabilized by electrostatic attraction
between the unshared pair of electrons of the amino group and the strongly positive hydrogen atom at position 2
of the imidazole ring. It is interesting that a similar conformation was also discovered in the crystals of 9-amino-
1-methylxanthine (3) [4] and 1-aminoperimidine (4) [5].
R
N
N
N
_
+
Cl
N
N
N
N
N
N
H
H
H
H
H
2a,b
H
1A
1B
2 a R = Me, b R = NH2
__________________________________________________________________________________________
1
Rostov State University, Rostov-on-Don 344090, Russia; e-mail: ODyablo@chimfak.rsu.ru.
2 A. N. Nesmeyanov Institute of Organoelement Compounds, Moscow 117813, Russia. Translated from
Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1324-1335, September, 2003. Original article submitted
December 13, 2001.
0009-3122/03/3909-1161$25.00©2003 Plenum Publishing Corporation
1161

↔
There is little reliable information on the 1A
1B equilibrium in solution. However it was established
with the aid of dipole moments that in solution form 1A is predominant [6]. As far as we know, only in crystals
of 1-amino-2-(1-cyano-1-ethoxycarbonylmethylene)-3-methylbenzimidazoline (5) was the opposite orientation
of the NH protons established, due to the formation of an intramolecular hydrogen bond [7].
H
H
O
N
O
Me
O
N
N
N
C–OEt
N
C
N
N
N
C
N
Me
N
N
H
N
H
H
H
H
4
5
3
N
Me
Me
N
N
N
N
N
H
O=C
O
N
H
6
7
The configuration of the amino group is clearly changed in N-amino azoles containing electron-
withdrawing substituents, such as CHO and NO, at the exocyclic nitrogen atom. In 1-formylaminoindazole (6)
[8] and 2-methyl-1-(nitrosomethylamino)benzimidazole (7) [9] the nitrogen atom of the substituted amino group
is completely flattened (sp2-hybridization) while the formamido- and nitrosomethylamino groups are disposed
almost perpendicular to the plane of the aromatic system.
NH2
N
N
N
N
N
N
N
N
NH2
NH2
NH2
10
11
8
9
The aim of the present work was to investigate the conformations of the amino group in
N-aminoimidazoles condensed with naphthalene 8-10 and phenanthrene 11 systems. It may be assumed that in
some of these compounds, particularly 10 and 11, the conformation of the NH2 group for steric reasons will be
closer to type 1B, i.e. different from 1-aminobenzimidazole.
Regretably, due to the poor solubility of the initial imidazoles in aqueous and aqueous alcoholic
solutions of alkali their amination with hydroxylamine O-sulfate was unsuccessful. Consequently as aminating
agent we used O-picrylhydroxylamine which is less available but capable of working in nonaqueous media [10].
The amination of phenanthro[9,10-d]imidazole (12) was carried out in DMF solution at room temperature. A
twofold excess of the initial imidazole was put into the reaction since half of it is consumed to form picrate 14.
The amine was not isolated, the reaction mixture was treated with benzaldehyde and the resulting Schiff's base
13 was purified by column chromatography. The yield was 37%. Hydrolytic decomposition of 13 on boiling in
conc. HCl gave 1-aminophenanthro[9,10-d]imidazole (11) in 94% yield.
1162

1) NH2OPic, DMF,
20 oC
N
N
N
.
PicOH
+
2) PhCHO, ∆
N
H
N
H
N
N
CHPh
13
11
14
12
1) conc. HCl, ∆
2) NH4OH
The amination of naphtho[1,2-d]imidazole (15) with subsequent boiling of the reaction mixture with
benzaldehyde leads to the formation of the isomeric 1-benzylideneamino- (17) and 3-benzylidene-
aminonaphtho[1,2-d]imidazoles (18). Their yields were 8 and 49% respectively, which is very close to the ratio
of the similar isomers on methylation of naphtho[1,2-d]imidazole [11]. The hydrolysis of azomethines 17 and 18
proceeds smoothly and gives amines 10 and 9 in good yield.
N
N
1) NH2OPic, DMF, 20 oC
.
PicOH
+
N
H
N
H
2) PhCHO, ∆
16
15
N
N
CHPh
N
N
+
+
N
N
CHPh
18
17
10
1) conc. HCl, ∆
2) NH4OH
1) conc. HCl, ∆
2) NH4OH
9
Naphtho[2,3-d]imidazole (19) is aminated by O-picrylhydroxylamine somewhat worse. The yield of
azomethine 20 did not exceed 31%. Subsequent boiling in conc. HCl gives 1-aminonaphtho[2,3-d]imidazole (8).
1) NH2OPic,
N
N
DMF, 20 oC
N
.
PicOH
+
2) PhCHO, ∆
N
H
N
H
N
N
CHPh
21
19
20
HCl, ∆
15 min
H
N
_
+
Cl
8
N
NH2
22
1163

N-Methyl derivatives of imidazoles are aminated by O-picrylhydroxylamine at room temperature in a
mixture of chloroform and acetonitrile with the formation of N-aminoimidazolium salts 23-26. Yields were
84-99%.
NH2
N
NH2
_
N
_
+
+
PicO
PicO
N
N
Me
Me
24
23
Me
N
NH2
N
_
_
+
X
X
+
N
N
NH2
Me
25a,b
26a,b
25, 26 a X = PicO, b X = Cl
Analysis of the 1H NMR spectra of the amines obtained enabled some opinions to be expressed on their
predominant conformation in solution. As is seen from Table 1 the chemical shifts of the 2-H proton in bases 1,
8-11 (8.12-8.35 ppm) and imidazolium salts 23-26 (9.61-9.87 ppm) were little changed. On the other hand the
position of the signal of the NH2 group protons varied within very wide limits, from 6.13 for
1-aminobenzimidazole to 6.69 and 6.73 ppm respectively for 1-aminonaphtho[1,2-d]imidazole and
1-aminophenanthro[9,10-d]imidazole. The particularly significant displacement towards low field of the δNH2
signal in the case of the latter two substances is logically explained in our opinion by the fact that in them the
NH2 protons undergo the effect of the diamagnetic field from the side of two benzene rings, while for all the
remaining amines only one benzene ring exerts such an effect. This indirectly points in favor of the existence of
conformation 1A, since in conformations of type 1B the NH2 group protons if covered by the magnetic force
lines of the ring current are unimportant. It is also impossible to exclude however the mobile equilibrium
between both forms with a predominance of form 1A. Regretably, there is no information up to the present on
the size of the barrier to amino group rotation about the N–N bond in N-amino azoles, without which it is
1
difficult to make an unequivocal choice in favor of one or the other possibility. The data of H NMR
spectroscopy for the N-aminoimidazolium salts obtained may also be interpreted in favor of the predominance
of conformation 1A in solution.
Regretably we did not succeed in growing crystals of amines 8-11 suitable for X-ray structural analysis.
However such crystals were obtained for 1-amino-3-methylnaphtho[1,2-d]imidazolium picrate (25a). On the
basis of the investigations carried out (see Fig. 1 and Tables 2-5) it is possible to draw the following
conclusions.
1. The naphthoimidazole fragment in salt 25a is practically planar.
2. The nitrogen atom of the N-amino group is in the sp3-hybridized state (sum of the valence angles at
the amine nitrogen is 324.4°).
3. A conformation of type 1B stabilized by hydrogen bonds with the picrate anion (Fig. 1) has been
detected for the first time for N-aminoimidazolium salts in the crystals of compound 25a. One of the NH
protons forms a bifurcated bond with the ortho-nitro group and the phenolic oxygen (this is the most stable
1164

TABLE 1. Data of 1H NMR Spectroscopy of the Compounds Synthesized
Chemical shifts, δ, ppm (J, Hz)*
Com-
pound
N–CH3 N–NH2 H(2)
CH=N
Other protons
1*2
2*2
8
—
4.04
—
6.13
6.92
6.22
8.07
9.71
8.35
—
—
—
—
—
7.40 (2H, m, 6-, 7-Н); 7.99 (1H, s, 9-H);
8.03 (2Н, m, 5-, 8-Н); 8.18 (1Н, s, 4-Н)
—
6.34
8.15
—
7.48 (1H, m, 8-Н); 7.61 (1Н, m, 7-Н);
7.74 (2Н, m, 6-, 9-Н); 8.00 (1Н, d, J54 = 8.0, 5-Н);
8.45 (1Н, d, J45 = 8.1, 4-Н)
9
—
6.69
8.12
—
7.60 (4H, m, 6-, 7-, 8-, 9-Н);
8.00 (1Н, d, J54 = 8.0, 5-Н);
9.08 (1Н, d, J45 = 8.1, 4-Н)
10
—
—
6.75
—
8.12
8.97
—
7.65 (4Н, m, 5-, 6-, 9-, 10-Н); 8.51 (1Н, m, 11-Н);
11
13
8.83 (2Н, m, 7-, 8-Н); 9.22 (1Н, d, J45 = 7.5, 4-Н)
9.30
7.70 (7H, m, 3'-, 4'-, 5'-, 5-, 6-, 9-, 10-Н);
8.09 (2Н, m, 2'-, 6'-Н); 8.59 (1Н, m., 11-Н);
8.88 (2Н, m, 7-, 8-Н); 9.09 (1Н, m, 4-Н)
—
–
—
–
8.53
9.07
8.56
9.87
9.70
8.87
9.30
8.89
—
7.52 (4H, m, 2'-, 3'-, 5'-, 6'-Н); 7.67 (1Н, m, 4'-H);
7.84 (2Н, m, 7-, 8-Н); 7.96 (3Н, m, 5-, 6-, 9-Н);
8.66 (1Н, d, J45 = 8.1, 4-Н)
17
18
20
23
24
7.58 (4H, m, 2'-, 3'-, 5'-, 6'-H); 7.68 (1Н, m, 4'-H);
7.95 (4Н, m, 6-, 7-, 8-, 9-Н); 8.21 (1H, d,
J
54 = 8.2, 5-H); 8.51 (1Н, d, J45 = 8.1, 4-Н)
–
–
7.46 (2H, m, 3'-, 5'-Н); 7.52 (3Н, m, 2'-, 4'-, 6'-Н);
7.98 (4Н, m, 5-, 6-, 7-, 8-Н); 8.19 (1Н, s, 9-Н),
8.30 (1Н, s, 4-Н)
4.11
4.47
6.98
7.06
7.66 (2Н, m, 6-, 7-H); 8.23 (2Н, m, 5-, 8-Н);
8.44 (1Н, s, 4-Н); 8.56 (1Н, s, 3-Н);
8.57 (2Н, s, 3'-, 5'-Н)
—
7.83 (2Н, m, 7-, 8-Н); 7.96 (1Н, d, J67 = 9.0, 6-Н);
8.21 (1Н, d, J45 = 9.0, 5-Н);
8.26 (1Н, d, J98 = 8.0, 9-Н); 8.59 (2Н, s, 3'-, 5'-Н);
8.64 (1Н, d, J45 = 9.0, 4-Н)
4.14
4.17
7.38
7.50
9.61
9.75
—
—
7.79 (2Н, m, 7-, 8-Н); 8.10 (3Н, m, 5-, 6-, 9-Н);
25a
25b
8.56 (2Н, s, 3'-, 5'-Н); 9.12 (1Н, d, J45 = 8.1, 4-Н)
7.81 (2H, m, 6-, 7-Н); 8.12 (2Н, m, 8-, 9-Н);
8.24 (1Н, d, J54 = 8.4, 5-Н);
9.16 (1Н, d, J45 = 8.4, 4-Н)
4.50
7.48
9.67
—
7.87 (4Н, m, 5-, 6-, 9-, 10-Н); 8.63 (1Н, m, 4-Н);
26b
9.02 (2Н, m, 7-, 8-Н), 9.35 (1Н, m, 11-Н)
_______
* The 1H NMR spectra were taken in CDCl3 (compounds 17 and 20) and in
DMSO-d6 (remaining compounds).
*2 Data were taken from [3] and are given for comparison.
hydrogen bond with a distance of 2.13 Å), while the second NH proton forms a second hydrogen bond with the
para-nitro group of another picrate anion. It is interesting that forked hydrogen bonds also exist between the 2-H
of the imidazolium ring and the phenolate oxygen and the second ortho-nitro group. It remains unclear whether
the existence of conformation 1B for salt 25a is a consequence of the impossibility of the existence of form 1A
due to steric obstacles from the side of the 10-H atom or is the result of the energetically more beneficial
formation of a cation–anion pair. The existence of 1-amino-3-methylbenzimidazolium picrate in the solid state
as form 1A [12] points indirectly in favor of the first hypothesis.
1165

Fig. 1. Crystallographic numbering of atoms and molecular structure of compound 25a.
TABLE 2. Crystallographic Data for Compound 25a.
Empirical formula
Molecular weight
Unit cell type
C18H14N6O7
426.35
Triclinic
a = 8.366(13) Å; α = 78.04(9) deg.
b = 9.869(12) Å; β = 84.34(12) deg.
c = 11.355(12) Å; 74.39(12) deg.
882.4(19)
2, 1.605
0.127
Unit cell parameters
Unit cell volume, Å3
Z, calculated density, mg/m3
Absorption coefficient, mm-1
Crystal dimensions
0.45 × 0.30 × 0.25
Rhombohedron, bright yellow
1.84-30.21
Type and color
Range of θ, deg
Completeness of data obtained, %
Method of refinement
98.8
2
Full matrix least squares for Fhkl
Number of independent reflections
Number of parameters refined
Final R factors [for 3241 reflections with I > 2σ(I)]
Final R factors for all independent reflections
5016 (Rint = 0.0262)
336
R1 = 0.0593, wR2 = 0.1467
R1 = 0.0819, wR2 = 0.1613
TABLE 3. Coordinates of Atoms and Equivalent Isotropic Factors (Ueq) and
Isotropic Factors (Uiso) for Hydrogen Atoms in the 25a Molecule
Atom
1
x
2
y
3
z
4
Ueq/Uiso
5
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
0.2537(2)
0.4819(2)
0.5676(2)
-0.1328(2)
-0.0851(2)
-0.1191(2)
0.1248(2)
0.7274(1)
0.8881(2)
0.8464(1)
0.6256(1)
0.7452(2)
0.9350(1)
0.9692(1)
-0.1365(1)
-0.1429(1)
0.0382(1)
0.0300(1)
-0.1472(1)
0.3218(1)
0.3390(1)
29(1)
39(1)
32(1)
31(1)
34(1)
31(1)
29(1)
1166

TABLE 3 (continued)
1
2
3
4
5
N(1)
0.5448(2)
0.2999(2)
0.1372(2)
0.4593(2)
-0.0667(2)
0.0270(2)
0.4006(2)
0.6862(2)
0.5368(2)
0.6584(2)
0.6167(2)
0.4573(2)
0.4181(2)
0.2673(2)
0.1457(2)
0.1783(2)
0.3335(2)
0.3818(2)
0.2003(2)
0.2946(2)
0.2421(2)
0.0835(2)
-0.0188(2)
0.0382(2)
0.3740(20)
0.7880(30)
0.7210(30)
0.6590(30)
0.0690(30)
0.1420(30)
0.7650(30)
0.6960(30)
0.5030(30)
0.2380(30)
0.0410(30)
0.0920(30)
0.3190(20)
-0.1380(30)
0.7973(2)
0.7520(2)
0.7434(2)
0.8596(2)
0.7119(2)
0.9330(2)
0.8082(2)
0.8448(2)
0.7299(2)
0.6920(2)
0.6244(2)
0.5919(2)
0.5222(2)
0.4915(2)
0.5281(2)
0.5943(2)
0.6285(2)
0.6997(2)
0.7815(2)
0.8465(2)
0.8930(2)
0.8850(2)
0.8266(2)
0.97784(2)
0.8480(20)
0.7550(30)
0.9070(30)
0.8790(30)
0.8280(30)
0.7210(30)
0.7170(20)
0.5930(20)
0.4980(20)
0.4450(20)
0.5060(20)
0.6190(20)
0.9360(19)
0.8220(20)
-0.4373(1)
-0.4218(1)
-0.3765(2)
-0.0330(1)
-0.0380(1)
0.2836(1)
-0.3732(2)
-0.4096(2)
-0.5319(2)
-0.6230(2)
-0.7031(2)
-0.6968(2)
-0.7833(2)
-0.7792(2)
-0.6867(2)
-0.6000(2)
-0.6041(1)
-0.5218(1)
-0.0460(2)
0.0162(1)
23(1)
22(1)
27(1)
27(1)
24(1)
23(1)
24(1)
29(1)
22(1)
25(1)
26(1)
24(1)
28(1)
30(1)
28(1)
25(1)
21(1)
20(1)
22(1)
21(1)
21(1)
21(1)
21(1)
21(1)
23(5)
63(8)
51(7)
56(7)
37(6)
47(7)
32(5)
36(6)
40(6)
33(5)
30(5)
32(5)
20(4)
32(5)
N(2)
N(3)
N(4)
N(5)
N(6)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
H(1)
H(2A)
H(2B)
H(2C)
H(1N3)
H(2N3)
H(4)
H(5)
H(7)
H(8)
H(9)
H(10)
H(15)
H(17)
0.1224(2)
0.1728(1)
0.1184(2)
0.0144(1)
-0.3048(17)
-0.3890(20)
-0.4780(20)
-0.3430(20)
-0.3999(19)
-0.2950(20)
-0.6226(17)
-0.7627(19)
-0.8470(20)
-0.8461(18)
-0.6813(18)
-0.5309(19)
0.1635(16)
0.1601(18)
TABLE 4. Some Bond Lengths (l) and Valence Angles (ω) in the 25a Molecule
Bond
1
l, Å
2
Angle
3
ω, deg
4
O(1)–C(13)
O(2)–N(4)
O(3)–N(4)
O(4)–N(5)
O(5)–N(5)
O(6)–N(6)
O(7)–N(6)
N(1)–C(1)
1.244(2)
1.229(2)
1.236(3)
1.234(2)
1.230(2)
1.252(3)
1.243(2)
1.336(3)
O(4)–N(5)–C(18)
O(7)–N(6)–O(6)
O(7)–N(6)–C(16)
O(6)–N(6)–C(16)
N(1)–C(1)–N(2)
N(1)–C(1)–H(1)
N(2)–C(1)–H(1)
N(1)–C(3)–C(12)
118.16(16)
122.64(17)
118.96(17)
118.40(17)
110.25(18)
124.9(12)
124.9(12)
107.55(18)
1167

TABLE 4 (continued)
1
2
3
4
N(1)–C(3)
N(1)–C(2)
N(2)–C(1)
N(2)–C(12)
N(2)–N(3)
N(3)–H(1N3)
N(3)–H(2N3)
N(4)–C(14)
N(5)–C(18)
N(6)–C(16)
C(1)–H(1)
C(3)–C(12)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(6)–C(11)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
C(13)–C(14)
C(13)–C(18)
C(14)–C(15)
C(15)–C(16)
C(15)–H(15)
C(16)–C(17)
C(17)–C(18)
1.391(3)
1.467(3)
1.338(3)
1.387(3)
1.425(3)
0.88(2)
N(1)–C(3)–C(4)
129.24(17)
105.86(17)
131.96(16)
124.25(17)
123.52(18)
112.12(17)
124.09(17)
116.58(17)
119.29(17)
118.97(18)
118.96(17)
119.67(17)
117.54(17)
125.10(17)
117.29(17)
107.55(17)
125.59(18)
126.83(17)
108.78(17)
125.69(17)
125.51(16)
107.5(14)
N(2)–C(12)–C(3)
N(2)–C(12)–C(11)
O(1)–C(13)–C(14)
O(1)–C(13)–C(18)
C(14)–C(13)–C(18)
C(15)–C(14)–C(13)
C(15)–C(14)–N(4)
C(13)–C(14)–N(4)
C(14)–C(15)–C(16)
C(17)–C(16)–N(6)
C(15)–C(16)–N(6)
C(17)–C(18)–N(5)
C(17)–C(18)–C(13)
N(5)–C(18)–C(13)
C(1)–N(1)–C(3)
0.91(3)
1.463(3)
1.459(3)
1.428(3)
0.92(2)
1.396(3)
1.412(3)
1.354(3)
1.445(3)
1.419(3)
1.432(3)
1.369(3)
1.420(3)
1.373(3)
1.421(3)
1.425(3)
1.450(3)
1.463(3)
1.369(3)
1.408(3)
1.049(19)
1.401(3)
1.360(3)
C(1)–N(1)–C(2)
C(3)–N(1)–C(2)
C(1)–N(2)–C(12)
C(1)–N(2)–N(3)
C(12)–N(2)–N(3)
N(2)–N(3)–H(1N3)
N(2)–N(3)–H(2N3)
H(1N3)–N(3)–H(2N3)
O(2)–N(4)–O(3)
105.9(15)
111(2)
123.03(18)
118.54(18)
118.38(17)
123.49(17)
118.35(16)
O(2)–N(4)–C(14)
O(3)–N(4)–C(14)
O(5)–N(5)–O(4)
O(5)–N(5)–C(18)
TABLE 5. Hydrogen Bonds for Compound 25a
D–H···A
D–H, Å
0.88(2)
H···A, Å
2.39(3)
DHA, deg.
146(2)
D···A, Å
3.162(4)
N(3)–H(1)N(3)···О(7)
[-x, -y + 2, -z]
N(3)–H(2)N(3)···O(1)
N(3)–H(2)N(3)···O(5)
C(1)–H(1)···O(1)
C(1)–H(1)···O(2)
O(5)···H(2)N(3)···O(1)
O(1)···H(1)···O(2)
0.91(3)
0.91(3)
0.92(2)
0.92(2)
76.3(8)
74.3(6)
70.0(8)
2.13(3)
2.41(3)
2.33(2)
2.27(2)
149(2)
128(2)
119(1)
144(2)
2.943(4)
3.047(5)
2.891(4)
3.068(4)
2.805(3)
2.778(3)
H(2)N(3)···O(1)···H(1)
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker 250 (250 MHz) spectrometer, and the IR spectra on a
Specord IR 75 spectrometer in nujol. A check on the course of reactions was effected by TLC on Al2O3
(Brockmann activity grade IV-V), eluent was chloroform, and visualization with iodine vapor. Melting points
were measured in sealed glass capillaries on a PTP instrument and are uncorrected.
1168

TABLE 6. Data of Elemental Analysis of the Synthesized Compounds
Found, %
——————
Com-
pound
Empirical
formula
Calculated, %
C
H
N
C11H9N3
72.00
72.11
4.90
4.95
22.70
22.93
8
C11H9N3
72.22
4.98
22.85
9
72.11
4.95
22.93
C19H11N3
72.25
72.11
4.87
4.95
22.99
22.93
10
C15H11N3
77.02
4.77
18.24
11
77.23
4.75
18.01
C22H15N3
82.07
82.22
4.81
4.70
13.25
13.07
13
C18H13N3
79.51
4.79
15.40
17
79.68
4.82
15.49
C18H13N3
79.51
79.68
4.79
4.82
15.40
15.49
18
C18H13N3
79.63
4.72
15.30
20
79.68
4.82
15.49
C18H14N6O7
C18H14N6O7
C18H14N6O7
С22H16 N6O7
C12H12ClN3
C16H14ClN3
50.78
50.71
3.20
3.31
26.42
26.26
23
50.58
3.42
26.39
24
50.71
3.31
26.26
50.63
50.71
3.40
3.31
26.14
26.26
25а
26а
25b*
26b*2
55.41
3.13
17.84
55.47
3.39
17.64
61.42
61.67
5.03
5.18
17.77
17.98
67.65
4.87
14.69
67.72
4.97
14.81
_______
*Found, %: Cl 15.30. Calculated, %: Cl 15.17.
*2 Found, %: Cl 12.28. Calculated, %: Cl 12.49.
The starting materials were synthesized by the following methods: O-picrylhydroxylamine [10],
phenanthro[9,10-d]imidazole (12) [13], naphtho[1,2-d]imidazole (15) [14], naphtho[2,3-d]imidazole (19) [15],
1-methylnaphtho- and 3-methylnaphtho[1,2-d]imidazoles [11], 1-methylnaphtho[2,3-d]imidazole [16], and 1-
methylphenanthro[9,10-d]imidazole [17].
d
X-ray Structural Investigation of 1-Amino-3-methylnaphtho[1,2- ]imidazolium Picrate (25a).
Bright yellow crystals of 25a were obtained by recrystallization from methanol. The experimental set
(10319 reflections) was obtained on a Bruker SMART 1000 CCD area detector diffractometer at 110 K.
Processing of the data was carried out with SAINT [18] and SADABS [19] programs.
The structure was solved by the direct method, all the nonhydrogen atoms were localized in difference
syntheses of electron density and were refined in an anisotropic approach. All the hydrogen atoms were
localized and refined in an isotropic approach. All calculations were carried out with the SHELXTL PLUS 5 set
of programs [20].
The structure has been deposited in the Cambridge Bank of Structural Data (Cambridge
Crystallographic Data Centre), registration number CCDC 174548.
N-Benzylideneaminoimidazoles (General Procedure). O-Picrylhydroxylamine (0.363 g, 1.5 mmol) in
DMF (20 ml) was added during 5 min to a solution of the appropriate imidazole (3 mmol) in DMF (16 ml) at
20°C. The mixture was stirred for 1 h, then benzaldehyde (0.3 ml, 3 mmol) was added, and the mixture boiled
for 1 h. The solvent was distilled off under reduced pressure to dryness, CHCl3 (7 ml) was added to the residue,
and yellow crystals of the picrate of the corresponding heterocycle were filtered off.
1169

d
Yellow needles; mp 305-308°C (DMF–butanol, 3:1).
Phenanthro[9,10- ]imidazole Picrate (14).
Yield 0.55 g (82%).
Naphtho[1,2-d]imidazole Picrate (16). Yellow needles; mp 210°C (ethanol). Yield 0.298 g (50%).
Naphtho[2,3-d]imidazole Picrate (21). Yellow needles; mp 145-148°C (ethanol). Yield 0.297 g (50%).
The chloroform solution was chromatographed on a column of Al2O3, eluent was chloroform (in the
case of compound 13 a mixture of CHCl3–EtOH, 3:1).
d
The fraction with Rf 0.7 was taken. Light
1-Benzylideneaminophenanthro[9,10- ]imidazole (13).
brown crystals; mp 300-302°C (DMF–butanol, 3:1). Yield 0.178 g (37%).
d
The chloroform solution was passed
1-and 3-Benzylideneaminonaphtho[1,2- ]imidazoles (17, 18).
through a column of Al2O3, two fractions were collected. The first (Rf 0.74) was compound 17. Colorless
crystals; mp 189-191°C (butanol). Yield 0.2 g (49%). The second fraction (Rf 0.7) was compound 18. Colorless
crystals; mp 198-200°C (butanol). Yield 0.033 g (8%).
d
The fraction with Rf 0.6 was collected. Light
1-Benzylideneaminonaphtho[2,3- ]imidazole (20).
brown crystals; mp 140°C (water–ethanol, 1:1). Yield 0.126 g (31%).
N-Aminoimidazoles (General Method). A suspension of the appropriate azomethine (0.5 mmol) in
conc. HCl (10 ml) was boiled for 1 h 30 min. Activated carbon was added and the mixture boiled a further
5 min. After separating the carbon the filtrate was neutralized with concentrated ammonia solution to pH 8-9.
The solid base was filtered off, and washed with water (1-2 ml).
d
Yield 0.046 g (50%). Colorless crystals; mp 167-170°C
1-Aminonaphtho[2,3- ]imidazole (8).
(ethanol). IR spectrum, ν, cm-1: 3100, 3150 (NH2).
d
Yield 0.055 g (60%). Colorless crystals; mp 185-187°C
3-Aminonaphtho[1,2- ]imidazole (9).
(benzene–ethanol, 2:1). IR spectrum, ν, cm-1: 3359, 3106 (NH2). Mass spectrum, m/z (Irel, %): 183 (100) [M]+,
168 (23) [M-NH]+, 155 (37) [M-N2]+, 140 (26) [M-HCN-NH2]+, 128 (16), 113 (12), 101 (7), 77 (6), 59 (6),
44 (23).
d
Yield 0.07 g (77%). Colorless crystals; mp 225-227°C
1-Aminonaphtho[1,2- ]imidazole (10).
(butanol). IR spectrum, ν, cm-1: 3332, 3146 (NH2).
d
Yield 0.11 g (94%). Colorless crystals; mp 280-283°C
1-Aminophenanthro[9,10- ]imidazole (11).
(DMF–butanol, 3:1). IR spectrum, ν, cm-1: 3293, 3106 (NH2).
d
A suspension of compound
1-Aminonaphtho[2,3- ]imidazolium Chloride (22).
20
(0.054 g,
0.2 mmol) in conc. HCl (3 ml) was boiled for 15 min. The mixture was evaporated to dryness on a boiling water
bath. Dark green crystals of chloride 22 were obtained. Yield 0.033 g (75%); mp 120-122°C (ethanol–benzene,
3:1). IR spectrum, ν, cm-1: 3386, 3186 (NH2), 2700 (NH+). Mass spectrum, m/z (Irel, %): 183 (100) [M-HCl]+,
168 (40) [M-HCl-NH]+, 155 (50) [M-HCl-N2]+, 140 (63), 127 (39), 113 (22), 101 (11), 77 (16), 44 (15).
N-Amino-N'-methylimidazolium Picrates (General Method). A solution of O-picrylhydroxylamine
(0.268 g, 1.1 mmol) in CH3CN (3 ml) was added with stirring to a solution of the appropriate
N-methylimidazole (1 mmol) in CHCl3 (10 ml). The mixture was stirred for 2 h. The yellow solid of compound
27-30 was filtered off, washed with CHCl3 (5 ml), and crystallized from DMF–butanol, 3:1.
d
Yield 0.422 g (99%). Yellow crystals;
Yield 0.383 g (90%). Yellow crystals;
Yield 0.388 g (91%). Yellow crystals;
1-Amino-3-methylnaphtho[2,3- ]imidazolium Picrate (23).
mp 228-229°C. IR spectrum, ν, cm-1: 3359, 3239 (NH2).
d
3-Amino-1-methylnaphtho[1,2- ]imidazolium Picrate (24).
mp 225-226°C. IR spectrum, ν, cm-1: 3333, 3173 (NH2).
d
1-Amino-3-methylnaphtho[1,2- ]imidazolium Picrate (25a).
mp 210-213°C. IR spectrum, ν, cm-1: 3332, 3186 (NH2).
d
Yield 0.4 g (84%). Yellow
1-Amino-3-methylphenanthro[9,19- ]imidazolium Picrate (26a).
crystals; mp 225-227°C. IR spectrum, ν, cm-1: 3352, 3186 (NH2).
1170

N-Amino-N'-methylimidazolium Chlorides (General Method). A suspension of compound 25a or
26a (0.3 mmol) in conc. HCl (2 ml) was evaporated on a boiling water bath. The residue was treated with ether
(3 × 10 ml), each time filtering off the undissolved solid chloride of 25b or 26b. 1-Amino-3-
d
(0.035 g, 50%) was obtained as colorless crystals;
methylnaphtho[1,2- ]imidazolium chloride (25b)
mp 244-245°C (DMF–butanol, 3:1) or 1-amino-3-methylphenanthro[9,10-d]imidazolium chloride (26b)
(0.043 g, 50%) as colorless crystals; mp 254-255°C (DMF–butanol, 3:1).
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1171