A facile access to indigodianiles

Article abstract of DOI:10.1002/jhet.5570430621

Bis-imidoylchlorides derived from oxalic acid can easily be transformed into the corresponding bis-imino benzotriazoles. The fact that benzotriazole is a well-established leaving group has been exploited for an improved synthesis of indigodianiles. Employ

Full text of DOI:10.1002/jhet.5570430621

Nov-Dec 2006
A Facile Access To Indigodianiles
1569
Christiane Kühn [1], Rainer Beckert [1]*, Manfred Friedrich [2], Helmar Görls [2]
Institute of Organic and Macromolecular Chemistry, Friedrich-Schiller-University, Humboldtstr. 10, D-07743
Jena, Germany; email: c6bera@uni-jena.de; [2] Institute of Inorganic and Analytical Chemistry, Friedrich-
Schiller-University, August-Bebel-Str. 2, D-07743 Jena, Germany
Received February 13, 2006
Ar
N
H
N
Ar
N
Bt1
N
Li, )))
R
R
Bt1
Ar
N
H
in THF
N
N
N
N
Ar
Bt1
=
Bis-imidoylchlorides derived from oxalic acid can easily be transformed into the corresponding bis-
imino benzotriazoles. The fact that benzotriazole is a well-established leaving group has been exploited for
an improved synthesis of indigodianiles. Employing metallic lithium, the benzotriazoles can be converted
in a cascade reaction into indigo bis-arylimines in yields up to 45%. Formation of the reduced form of
dimeric isocyanides is suggested as a key step.
J. Heterocyclic Chem., 43, 1569 (2006).
Introduction.
Scheme 2
Indigoid systems show increasing importance as
functional dyes due to their effective chromophoric
systems connected with their chemical and thermal
stability. A variation of the conjugated system can be
achieved, e.g., by transformation of both the carbonyl
groups of 1 into the corresponding imines 2. Indigo and
its derivatives are in the center of interest as textile dyes
and functional materials, however insufficient data is
available pertaining to imines of type 2.
Ar
N
Cl
N
Cl
Ar
3
Ar
N
C
C N Ar
Ar
N
C
C
N
Ar
Ar
4
Scheme 1
Ar
N
N
H
N
H
N
R
R
X
H
N
N
H
R
N
R
R
H
R
N
N
N
Ar
Ar
H
5
2
X
1 X = O
2 X = NAr
acid 3 [4]. Such acylderivatives are valuable building
blocks for numerous heterocyclic compounds which were
often formed via cascade reactions [5]. We could
demonstrate that by employing metallic magnesium as a
reducing agent, the bis-imidoylchlorides 3 can serve as
precursor molecules for dimeric isocyanides 4 [4]. In a
smooth reaction, diarylimines of indigo 2 as well as their
isomers, the diimines of epindolidione 5, were isolated in
low yields. Heterocumulenes of type 4 have already been
postulated as intermediates [6], however, have never been
isolated. Comparable to the corresponding oxa-analogue,
ethenedione, they should possess a triplett structure in
their ground state [7] and should therefore display the
Already during the distillation of phenylisocyanide an
intense blue-green color was observed and at first
ascribed to the phenylisocyanide [1]. Publications in the
following period [2] regarding the productive synthesis by
heating indigo and aniline together with boric acid are in
doubt. Detailed investigations of this crystalline substance
which precipitated from pure phenylisocyanide, finally
allowed the identification of the product resulting from
the condensation of indigo and aniline as indigodianile
[3].
In 1999 we reported
a formation reaction of
indigodianiles starting from bis-imidoylchlorides of oxalic

1570
C. Kühn, R. Beckert, M. Friedrich, H. Görls
Vol 43
reactivity of a biradical. Recently, indigodianiles 2 (R = F,
Ar = 4-FC6H4) have been isolated and structurally
characterized as by-products in the course of a thermic
induced oligomerization reaction of isocyanides [8].
and 2-regioisomer) product. Furthermore, the non-
symmetric bis-benzotriazole 6g (Ar1=4-CH3C6H4, Ar2=2-
BrC6H4) was prepared in this manner.
In contrast to the starting material
3 the new
bifunctional benzotriazoles of type 6 are crystalline pale-
yellow compounds which are stable against hydrolysis.
The synthesis starting from bis-imidoylchlorides 3 has
been optimized and now tolerates a great variety of
substituents. In contrast to the earlier described protocol
[10], a smaller amount of benzotriazole (2 equivalents
instead of 6) was employed.
Results and Discussion.
Not only the low yields which were obtained for 2 and
5, but also their interesting spectral properties offered us
incentives to search for better suitable starting materials
for these compounds. A promising reaction was the
replacement of both of the chlorides in bielectrophiles 3
by better leaving-groups which should minimize the
amounts of by-products due to a lower nucleophilicity.
Scheme 3
Br
C8
N1
N4
C14
N2
N
C1
C9
benzotriazole
TEA/dioxane
N
Ar1
N
N
N
N
Ar
N
N
N
N6
C2
N
3
N
N
N
Ar2
N
N
N
Ar
N8
N5
C27
6 h: Ar = 2,4,6-Me3C6H2
6 a: Ar1/Ar2 = C6H5
6 b: Ar1/Ar2 = 4-MeC6H4
6 c: Ar1/Ar2 = 4-tertBuC6H4
6 d: Ar1/Ar2 = 4-BrC6H4
6 e: Ar1/Ar2 = 3-CF3C6H4
6 f: Ar1/Ar2 = 1-naphthyl
Figure 1. ORTEP drawing of the molecule 6g [16]: Selected bond
lengths C1-C2 (1.512(8) Å), C1-N1 (1.410(8) Å), C1-N4 (1.255(7) Å),
C2-N5 (1.403(7) Å), C2-N8 (1.261(7) Å)
6 g: Ar1 = 4-MeC6H4 Ar2 = 2-BrC6H4
Benzotriazole, which is extensively applied in organic
Furthermore, an X-ray structural analysis could be
obtained from single crystals (from DMSO) of 6g, the
result of which is depicted in Figure 1. In comparison to
the starting material of type 3, this crystal structure
revealed two essential distinctions. The planes of the
amidine units N4-C1-N1 and N8-C2-N5 are considerably
twisted with approximately 80° (bis-(2,5-diisopropyl-
phenylimidoylchloride: 6° [15]). As a consequence, the
central C-C bond in 6g is slightly extended (1.512(8) Å,
3: 1.495 Å). The bond lengths between the central carbon
and the new introduced leaving groups are fundamentally
shorter (1.410(8)Å) than the carbon-chlorine bonds in
derivatives 3 (1.752 Å).
These crystal data make them promising candidates for
experiments for the generation of dimeric isocyanides.
Firstly, solutions of benzotriazoles 6a-c and 6f were
treated with n-BuLi in order to test the quality of the
leaving groups. Even at -78°C, the reaction resulted in a
deep red/brown mixture which became light brown-
yellowish for a short time during the warm-up period. On
contact with air, the color immediately changed to deep
blue and the indigodianiles of type 2 could be detected by
TLC. The isolated yields for compounds 2 were in the
range of approx. 10% and therefore somewhat higher than
synthesis, seemed to be the most promising candidate [9].
A series of imidoyl derivatives of benzotriazole has
already been shown to be a valuable precursor molecule
for the construction of new heterocyclic systems. By
means of these acyl-equivalents a great variety of
imidates and thioimidates [10], guanidines [10] as well as
ketones [11] and several heteroaromatics [12] could be
synthesized. Bis-phenylimidoyl benzotriazole 6a, for
example, is easily accessible via the reaction of oxalic
acid anilide with in-situ generated sulfinyl bis-
benzotriazole in the presence of trimethylchlorosilane
with 86% yield [10,11,13]. Due to the fact that
imidoylchlorides 3 are well-established in our group [14],
we alternatively employed their substitution reaction with
benzotriazole. Upon heating derivatives 3 with a small
excess of benzotriazole together with triethylamine under
reflux in dioxane, the bis-imidoylbenzotriazoles of type 6
are prepared in high yield.
The procedure results in the formation of 1-
benzotriazoles with a high regioselectivity (Bt1 as the
exclusive regioisomer in nearly all cases) as could be
determined via NMR spectroscopy. The 2-regioisomer
(Bt2) could be detected only for the sterically demanding
mesityl group in derivative 6h, in addition to a mixed (1-

Nov-Dec 2006
A Facile Access To Indigodianiles
1571
reported starting from 3 [4]. The halogen substituted
derivatives 6d, e were reacted similarly. In this case, only
tarry-like materials were isolated which most likely
resulted from the competition of the halogen-lithium
exchange followed by oligomerization reactions.
However, for the benzotriazole 6g a bromine-lithium
exchange in the desired position seems to be the key-step
for an ortho-cyclization to give a small amount of
indolone derivative 7 via a cascade-reaction.
Monitoring of both formation reactions by ESR-
spectroscopy displayed different radical species. Despite
well-resolved spectra with a hyperfine-structure, the
structural assignment is difficult. Spectra of different
derivatives of type 6 are nearly identical. Most likely the
radicals formed in both reaction pathways derive from
benzotriazole derivatives [18]. Taking these findings into
account, the following mechanism is proposed for the
reaction with metallic lithium. Upon step-wise cleavage
Scheme 4
n-BuLi
Ar1
a)
N
-78°C, THF
N
H
N
H
Ar1
N
N
N
N
N
N
R
R
Ar2
N
N
N
H
N
N
Li, )))
Ar2
b)
rt, THF
7
6a-c, f; g
2a-c, f
6 a: Ar1/Ar2 = C6H5
2 a: Ar1/Ar2 = C6H5
2 b: Ar1/Ar2 = 4-MeC6H4
R = H
6 b: Ar1/Ar2 = 4-MeC6H4
6 c: Ar1/Ar2 = 4-tertBuC6H4
6 f: Ar1/Ar2 = 1-naphthyl
R = Me
2 c: Ar1/Ar2 = 4-tertBuC6H4 R = tertBu
2 d: Ar1/Ar2 = 1-naphthyl
R = benz[g]
6 g: Ar1 = 4-MeC6H4 Ar2 = 2-BrC6H4
According to earlier experiments [4,17], the
benzotriazoles 6 reacted with metallic lithium under
ultrasonic irradiation. Already at the start of the reaction,
a rapid change in color of the solution from reddish brown
to finally deep green could be observed. Usually, the
reaction reached completion after 30 minutes and no
starting material could be detected by TLC. Treatment of
the mixture with methanol yielded indigodianiles 2 up to
45% as well as polymeric material. Elemental analyses
and NMR data of the deep blue-green compounds were in
agreement with the structure of dianiles of type 2.
of both benzotriazole units the dimeric isocyanides 4 were
generated. These predicted and in situ generated
intermediates are not stable enough to be detected.
Immediately, the reduction with lithium forms the radical
anion A via single-electron transfer step and is stabilized
by its non-aromatic mesomeric form B. Thereafter,
common cyclization reaction (C) followed by a 1,3-
hydride shift which gives D takes place. The dimerization
reaction of this radical may furnish E which can also be
regarded as the leuco-form of the dianiles 2. Finally, on
contact with air and methanol, an oxidation/protonation-
Scheme 5
Ar
N
C
A
C
N
Ar
Ar
N
H
N
N
1,3 ~ H
R
Li
Li )))
e-
Ar
N
C
C
N
Ar
C
C
C
2 -2 LiBt
R
C
N
C
N
Bt
H
N
6
4
C
C
N
Ar
Ar
C
D
R
H
Ar
B
Ar
N
Ar
N
N
H
R
oxidation, H+
R
dimerization
-H+
N
N
N
H
R
R
N
N
Ar
Ar
E
2
leucoform

1572
C. Kühn, R. Beckert, M. Friedrich, H. Görls
Vol 43
2H), 7.55 (t, J = 7.5 Hz, 2H), 7.17-7.11 (m, 6H), 6.62-6.55 ppm
(m, 4H); 13C nmr (50 MHz, CDCl3): ꢀ 146.1 (N=C-C=N), 144.9,
142.5, 130.6, 129.6, 128.6, 125.9, 125.6, 119.9, 119.8, 114.6
(aryl) ppm; ms: m/z (DCI with H2O) 443 (100) (M++H+), 415
(10), 388 (35), 385 (45), 324 (100), 312 (28), 296 (23), 284 (10),
241 (58), 221 (80), 193 (35), 166 (10), 120 (10), 96 (35), 90
(20), 78 (30).
step produces 2. It is not obvious at which stage (A or D)
dimerization takes places to form the final products.
Other well-established one-electron transfer reagents
showed different results. Whereas sodium naphthalenide
showed no reaction with 6, lithium di-tert.-butyl-
biphenylide gave the dianiles 2, however in poorer yields.
Anal. Calcd. for C26H18N8: C, 70.58; H, 4.10; N, 25.32.
Found: C, 70.21; H, 4.05; N, 24.95.
EXPERIMENTAL
Bis-(4-tolylimidoyl-1-benzotriazole) (6b).
Reactions were monitored by tlc, carried out on 0.2 mm
Merck silica gel plates (60 F254) or Merck Aluminium sheets
This compound was obtained as pale yellow solid, 4.5 g,
(95%), mp 215°C; ir (ATR): 3029, 2918 (w) (arC-H), 1645 (m)
1
(C=N) cm-1; H nmr (250 MHz, CDCl3): ꢀ 8.38 (d, J = 8.3 Hz,
Aluminium oxide (150 F254
)
using uv light. Column
chromatography was carried out on Merck silica gel 60 (0.040 –
0.063 mm) or Merck neutral alumina 90 (0.063 – 0.0209 mm;
2H), 8.05 (d, J = 8.2 Hz, 2H), 7.59 (t, J = 7.7 Hz, 2H), 7.46 (t, J
= 7.4 Hz, 2H), 6.87 (d, J = 8.3 Hz, 4H), 6.43 (d, J = 8.3 Hz, 4H),
2.21 ppm (s, 6H); 13C nmr (63 MHz, CDCl3): ꢀ 146.3 (N=C-
C=N), 142.7, 135.7, 130.9, 129.9, 129.5, 126.2, 120.3, 120.1,
119.8, 115.1 (aryl), 21.0 (CH3) ppm; ms: m/z (DEI) 470 (7)
(M+), 413 (100), 399 (7), 324 (70), 308 (10), 268 (80), 235 (20),
207 (95), 192 (65), 180 (30), 134 (10), 117 (25), 107 (35), 91
(100), 65 (30).
1
activity V). H- and 13C-nmr spectra were obtained on a Bruker
DRX 400 or AVANCE 400, Bruker AC 250 or AVANCE 200
spectrometer. The remaining protons of the deuterated solvents
were used as internal standard. The esr spectra were recorded
with a Bruker ESP 300 E spectrometer. Melting points are
measured with a Galen III apparatus (Boëtius system) and are
uncorrected. uv/vis spectra were recorded on a UNICAM UV
500 spectrophotometer. ir: Digital Division FTS 25 from
BioRad. Ms spectra were taken from measurements on a
Finnigan MAT SAQ 710 mass spectrometer or TRIO 2000 from
FISONS. Elemental analyses were carried out in-house with an
automatic analyzer LECO CHNS 932. Crystal Structure
Determination: The intensity data for the compound was
Anal. Calcd. for C28H22N8: C, 71.47, H, 4.71, N, 23.81. Found:
C, 71.27, H, 5.00, N, 23.75.
Bis-(4-tertbutylphenylimidoyl-1-benzotriazole) (6c).
This compound was obtained as pale yellow solid, 5 g (90%),
mp 209°C; ir (ATR): 3034 (w) (arC-H), 1654 (m) (C=N) cm-1;
1H nmr (250 MHz, CDCl3): ꢀ 8.45 (d, J = 8.3 Hz, 2H), 8.13 (d, J
= 8.2 Hz, 2H), 7.67 (t, J = 7.5 Hz, 2H), 7.54 (t, J = 7.2 Hz, 2H),
7.13 (d, J = 8.5 Hz, 4H), 6.51 (d, J = 8.5 Hz, 4H), 1.29 ppm (s,
18H); 13C nmr (63 MHz, CDCl3): ꢀ 149.2 (N=C-C=N), 146.2,
142.5, 142.3, 131.0, 129.7, 126.1, 125.7, 120.1, 119.9, 115.0
(aryl), 34.4 (Cquat), 31.3 (CH3) ppm; ms: m/z (DEI) 554 (1) (M+),
525 (0.5), 497 (60), 193 (70), 144 (80), 116 (90), 57 (100).
Anal. Calcd. for C34H34N8: C, 73.62; H, 6.18; N, 20.20.
Found: C, 73.97; H, 6.47; N, 20.05.
collected on
a Nonius KappaCCD diffractometer, using
graphite-monochromated Mo-Kꢀ radiation. Data were corrected
for Lorentz and polarization effects, but not for absorption [19,20].
The structure was solved by direct methods (SHELXS [21]) and
refined by full-matrix least squares techniques against Fo2
(SHELXL-97 [22]). All hydrogen atoms were included at
calculated positions with fixed thermal parameters. All non-
hydrogen atoms were refined anisotropically [22]. XP (SIEMENS
Analytical X-ray Instruments, Inc.) was used for structure
representations.
Bis-(1-naphthylimidoyl-1-benzotriazole) (6f).
The bis-imidoylchlorides 3a-h and 3f were synthesized
according to literature [23]. Other reagents were commercially
available and were used without further purification. All
solvents were of reagent grade and were dried and distilled
before use using standard techniques.
This compound was obtained as pale yellow solid, 4.6 g,
(86%), mp 276°C; ir (ATR): 3053 (w) (arC-H), 1666 (m) (C=N)
cm-1; 1H nmr (250 MHz, CDCl3): ꢀ 8.57 (d, J = 8.2 Hz, 2H), 8.21
(d, J = 8.3 Hz, 2H), 7.77-7.56 (m, 4H), 7.37-7.25 (m, 4H), 7.08-
7.02 (m, 4H), 6.85-6.81 ppm (m, 6H); 13C nmr (50 MHz,
CDCl3): ꢀ 146.1 (N=C-C=N), 142.5, 141.6, 133.0, 130.8, 129.8,
128.6, 126.7, 126.2, 126.0, 125.5, 124.8, 124.6, 121.7, 119.8,
114.7, 112.6 (aryl) ppm; ms: m/z (DEI) 542 (0.3) (M+), 519
(0.2), 485 (20), 396 (10), 344 (10), 243 (60), 216 (75), 153
(100), 127 (60).
General Procedure for Bis-(imidoylbenzotriazoles) of Oxalic
acid.
Bis-(arylimidoylchlorides) 3a-h, 10 mmol, triethylamine, 30
mmol and 1H-benzotriazole, 25 mmol, were heated under reflux
in 80 ml of dioxane for several hours (maximum 72 hours) and
the progress of the reaction was monitored by tlc (silicagel,
toluene). The precipitate was filtered off. The solvent was
removed in vacuo and the residue was recrystallised from
ethanol/methylenchloride to give pure derivatives 6a-h (yields
75-95%).
Anal. Calcd. for C34H22N8: C, 75.26; H, 4.09; N, 20.65.
Found: C, 75.39; H, 4.14; N, 19.10.
Bis-(3-trifluoromethylphenylimidoyl-1-benzotriazole) (6e).
This compound was obtained as pale yellow crystals, 4.7g
(81%), mp 145°C; ir (ATR): 1661 (m) (C=N) cm-1; 1H nmr (250
MHz, CDCl3): ꢀ 8.40 (d, J = 8.2 Hz, 2H), 8.18 (d, J = 8.2 Hz,
2H), 7.71 (t, J = 7.7 Hz, 2H), 7.59 (t, J = 7.7 Hz, 2H), 7.41 (d, J
= 7.9 Hz, 2H), 7.30 (t, J = 7.8 Hz, 2H), 6.83 (d, J = 7.9 Hz, 2H),
6.74 ppm (s, 2H); 13C nmr (63 MHz, CDCl3): 146.5 (N=C-C=N),
145.4, 143.8, 131.8 (q, JCF = 33 Hz) (C-CF3), 130.7, 130.5,
129.9, 126.8, 123.4 (q, JCF = 273 Hz) (CF3), 122.9, 120.5, 117.9,
Bis-(phenylimidoyl-1-benzotriazole) (6a).
This compound was obtained as pale yellow solid, 3.9 g,
(88%), mp 187°C (87°C [13]); ir (ATR): 3060, 3033 (w) (arC-
H), 1650 (m) (C=N) cm-1; 1H nmr (200 MHz, CDCl3): ꢀ 8.46 (d,
J = 8.2 Hz, 2H), 8.15 (d, J = 8.4 Hz, 2H), 7.68 (t, J = 7.5 Hz,

Nov-Dec 2006
A Facile Access To Indigodianiles
1573
114.8 (aryl) ppm; ms: m/z (DEI) 578 (0.3), 521 (25), 261 (50),
145 (70), 90 (100).
Anal. Calcd. for C28H16F6N8: C, 58.14; H, 2.79; N, 19.37.
Found: C, 57.90; H, 2.75; N, 19.08.
nmr (250 MHz, CDCl3): ꢀ 8.08 (d, J = 7.5 Hz, 4H), 7.54-7.44
(m, 4H), 6.67 (s, 4H), 2.27 (s, 6H), 1.72 ppm (s, br, 12H); 13C
nmr (63 MHz, CDCl3): ꢀ 145.9 (N=C-C=N), 140.2, 134.6,
131.3, 129.6, 129.0, 128.7, 125,8, 120.1, 114.5 (aryl), 20.6 (2-
CH3), 18.0 (4-CH3) ppm; ms: m/z (DEI) 526 (0.1) (M+), 455
(10), 380 (20), 235 (40), 220 (100), 130 (35).
Bis-(4-bromophenylimidoyl-1-benzotriazole) (6d).
This compound was obtained as pale yellow solid, 4.6 g,
(77%), mp 230°C; ir (ATR): 3067 (w) (arC-H), 1650 (m) (C=N)
cm-1; 1H nmr (250 MHz, CDCl3): ꢀ 8.33 (d, J = 8.3 Hz, 2H), 8.07
(d, J = 8.2 Hz, 2H), 7.62 (t, J = 7.7 Hz, 2H), 7.49 (t, J = 7.7 Hz,
Anal. Calcd. for C32H30N8: C, 72.98; H, 5.74; N, 21.28.
Found: C, 72.30; H, 5.70; N, 21.00.
General Procedure for the Synthesis of Indigodianiles.
2H), 7.22 (d, J = 8.7 Hz, 4H), 6.41 ppm (d, J = 8.7 Hz, 4H); 13
C
a) With n-BuLi.
nmr (63 MHz, CDCl3): ꢀ 146.3 (N=C-C=N), 144.1, 143.1,
132.1, 130.7, 130.3, 126.6, 122.0, 120.3, 119.6, 114.9 (aryl)
ppm; ms: m/z (DEI) 600 (1) (M+), 543 (10), 454 (3), 389 (10),
273 (35), 192 (100), 157 (40), 90 (80).
Anal. Calcd. for C26H16Br2N8: C, 52.02; H, 2.69; N, 18.67; Br,
26.62. Found: C, 52.25; H, 2.81; N, 18.39; Br, 26.18.
To a degassed solution of benzotriazole 6 (0.5 mmol) in dried
THF was added dropwise n-butyllithium (2.5 M in hexane) (1
mmol) at -78°C. The solution instantly became deeply red. After
stirring for 30min at -78°C the solution was allowed to warm up.
The color turned into brownish-green. Finally the solution was
filtered, whereby in the presence of oxygen the color turned to
deep blue-green. Evaporation of the solvent gave crude product
which was immediately purified by column chromatography on
alumina (toluene). The yields were all in the range of 10-20%.
N1-(2-Bromophenyl)-N2-4-tolyl-oxalo diimidoyl dibenzotriazol
(6g).
3g was prepared starting from ethyl(2-bromophenyl-
amino)oxoacetate [24] that was heated at reflux with 4-
toluidine in xylene for several days to give the N1-(2-
bromophenyl)-N2-4-tolyloxalamide [25]. The latter was
chlorinated following the general protocol [23] for
imidoylchlorides (in toluene with phosphorus penta-
chloride) to give the N1-(2-Bromo-phenyl)-N2-4-tolyl-
oxalodiimidoyl dichloride [26].
b) With Li granulate.
To a degassed solution of benzotriazole 6 (0.5 mmol) in dried
THF was added lithium granulate (5 mmol) and the mixture was
irradiated with ultra sound for about 30min. The progress of the
reaction was monitored by tlc unless no benzotriazole 6 was
there. After adding dropwise methanol, filtration on air
followed. The solution was evaporated and the residue was
purified by column chromatography (alumina, toluene).
This compound (6g) was obtained as pale yellow crystals, 4.4
g (82%), mp 232°C; ir (ATR): 3058 (w) (arC-H), 1650 (m)
1
(C=N) cm-1; H nmr (250 MHz, DMSO-d6): ꢀ 8.55 (d, J = 8.3
3,3'-Bis-[phenylimino]-1,3,1',3'-tetrahydro-[2,2']biindolylidene
(2a).
Hz, 1H), 8.41 (d, J = 8.3 Hz, 1H), 8.32 (d, J = 8.3 Hz, 2H), 7.86
(q, J = 7.5 Hz, 2H), 7.70 (t, J = 7.5 Hz, 2H), 7.59 (d, J = 7.8 Hz,
1H), 7.23 (t, J = 7.5 Hz, 1H), 7.14 (t, J = 7.5 Hz, 1H), 6.99 (d, J
= 8.1 Hz, 2H), 6.80 (d, J = 7.5 Hz, 1H), 6.33 (d, J = 8.2 Hz, 2H),
2.22 ppm (s, 3H); 13C nmr (63 MHz, DMSO-d6): ꢀ 145.63
(C=N), 145.59 (C=N), 142.8, 142.5, 142.1, 141.8, 141.7, 141.5,
136.1, 135.9, 133.0, 131.2, 131.1, 131.0, 130.0, 129.6, 128.6,
128.4, 127.2, 127.0, 120.4, 120.0, 119.2, 118.5, 114.3, 114.2
(aryl), 20.5 (CH3) ppm; ms: m/z (DEI) 535 (0.1) (M+), 479 (5),
413 (20), 399 (80), 308 (45), 207 (60), 192 (100).
This compound was obtained as dark blue solid, 93 mg
(45%), mp 284°C; ir (ATR): 3303 (w) (N-H), 3060 (w) (arC-H),
1665 (m) (C=N) cm-1; uv/vis (CHCl3) ꢁ (logꢂ) 285 (4.4), 342
1
(4.0), 361 (4.0), 596 (4.1), 657 (3.9), 730 (2.4); H nmr (250
MHz, THF-d8): ꢀ 10.2 (s, br), 7.43-6.61 (m, 18H); 13C nmr (63
MHz, THF-d8): ꢀ 148.2 (C=N), 146.0 (C=C), 128.5, 127.1,
122.6, 121.6, 118.5, 117.2, 116.8, 113.2, 112.5 (aryl) ppm; ms:
m/z (DEI) 412 (M+) (100), 335 (40), 320 (70), 218 (20), 206
(30), 178 (30), 77 (70).
Anal. Calcd. for C27H19BrN8: C, 60.57; H, 3.58; N, 20.93.
Found: C, 61.12; H, 3.83; N, 20.98.
Anal. Calcd. for C28H20N4: C, 81.53; H, 4.89; N, 13.58.
Found: C, 81.16; H, 4.45; N, 13.23.
Crystal Data for 6g [16].
Compound 6g has C27H19BrN8, Mr = 535.41 gmol-1, colorless
prism, size 0.04 x 0.04 x 0.03 mm3, orthorhombic, space group
Pbca, a = 15.3324(5), b = 15.5069(5), c = 20.4728(7) Å, V =
4867.6(3) Å3 , T= -90 °C, Z = 8, ꢀcalcd. = 1.461 gcm-3, μ (Mo-Kꢁ)
= 17.22 cm-1, F(000) = 2176, 31297 reflections in h(-19/17), k(-
20/19), l(-26/26), measured in the range 2.12° ꢂ ꢃ ꢂ 27.48°,
5,5'-Dimethyl-3,3'-bis-[4-tolylimino]-1,3,1',3'-tetrahydro[2,2']bi-
indolylidene (2b).
This compound was obtained as dark blue solid, 94 mg
(40%), mp 298°C; ir (ATR): 3374 (m) (N-H), 3052, 3021 (m)
(arC-H), 1615 (m) (C=N) cm-1; uv/vis (CHCl3) ꢁ (logꢂ) 289
1
(4.4), 353 (4.0), 624 (4.0), 673 (4.0), 745 (3.8); H nmr (250
completeness ꢃ
=
99.9 %, 5572 independent reflections,
Rint = 0.088, 3307 reflections with Fo > 4ꢄ(Fo), 326 parameters,
0 restraints, R1obs = 0.096, wR2obs = 0.264, R1all = 0.153, wR2
max
MHz, CD2Cl2): ꢀ 9.73 (br, s, 2H), 7.15 (d, J = 8.0 Hz, 4H), 7.09
(d, J = 8.0 Hz, 2H), 7.02-6.98 (m, 6H), 6.75 (s, 2H), 2.32 (s,
6H), 2.10 ppm (s, 6H); 13C nmr (63 MHz, CD2Cl2): ꢀ 146.7
(C=N), 142.6 (C=C), 132.3, 130.0, 129.2, 128.3, 123.1, 118.1,
117.7, 113.8 (aryl), 19.6, 19.3 (CH3) ppm; ms: m/z (DEI) 468
(M+) (100), 377 (40), 362 (80), 348 (15), 234 (20), 91 (30), 65
(20).
=
all
0.295, GOOF = 1.093, largest difference peak and hole: 1.233 / -
1.442 e Å-3.
Bis-(2,4,6-trimethylphenylimidoyl-2-benzotriazole) (6h).
This compound was obtained as yellow crystals, 2.4 g (46%)
after column chromatography (silica gel, CHCl3), mp 228°C; ir
(ATR): 2960, 2920, 2855 (w) (arC-H), 1669 (m) (C=N) cm-1; 1H
Anal. Calcd. for C32H28N4: C, 82.02; H, 6.02; N, 11.96.
Found: C, 81.81; H, 5.84; N, 11.71.

1574
C. Kühn, R. Beckert, M. Friedrich, H. Görls
Vol 43
[7] G. Maier, H. P. Reisenauer, B. Röther, J. Eckwert, Liebigs
Ann. Chem., 303 (1996).
[8] J. C. A. Boeyens, L. M. Cook, Y. Ding, M. A. Fernandes, D.
H. Reid, Org. Biomol. Chem., 1, 2168 (2003).
[9] A. R. Katritzky, B. V. Rogovoy, Chem. Eur. J., 9, 4586
(2003); A. R. Katritzky, J. Heterocyclic Chem., 36, 1501 (1999); A. R.
Katritzky, X. Lan, J. Z. Yang, O. V. Denisko, Chem. Rev., 98, 409
(1998).
[10] A. R. Katritzky, C. V. Stevens, G.-F. Zhang, J. Jiang, N. De
Kimpe, Heterocycles, 40, 231 (1995).
[11] A. R. Katritzky, S. Rachwal, R. J. Offerman, Z. Najzarek, A.
K. Yagoub, Y. Zhang, Chem. Ber., 123, 1545 (1990).
[12] A. R. Katritzky, B. Yang, R. Abonia, B. Insuasty, J. Chem.
Res. Synop., 540 (1996); A. R. Katritzky, T.-B. Huang, M. V. Voronkov,
J. Org. Chem., 65, 8069 (2000).
[13] A. R. Katritzky, T.-B. Huang, P. J. Steel, J. Org. Chem., 66,
5601 (2001).
[14] D. Lindauer, R. Beckert, M. Döring, P. Fehling, H. Görls, J.
Prak. Chem., 337, 143 (1995).
5,5'-Di-tert-butyl-3,3'-bis-[4-tert-butyl-phenylimino]-1,3,1',3'-
tetrahydro-[2,2']biindolylidene (2c).
This compound was obtained as dark blue solid, 110 mg
(35%), mp 305°C; ir (ATR): 3367 (w) (N-H); 3038 (w) (arC-H),
1615 (m) (C=N) cm-1; uv/vis (CHCl3) ꢀ (logꢁ) 292 (4.3), 353
(3.9), 604 (4.0), 670 (3.9), 740 (2.8); 1H nmr (200 MHz, CDCl3):
ꢂ 7.46 (d, J = 8 Hz, 4H), 7.33-7.13 (m, 10H), 6.83 (s, 2H), 1.40
(s, 18H), 1.13 ppm (s, 18H); 13C nmr (50 MHz, CDCl3): ꢂ 147.6
(C=N), 146.8 (C=C), 144.8, 143.1, 128.7, 127.9, 125.6, 121.3,
119.4, 118.3, 113.9 (aryl), 34.1, 34.05 (Cquat), 31.2, 30.9 (CH3)
ppm; ms: m/z (DEI) 636 (M+) (25), 318 (M+/2) (100), 303 (50),
134 (25), 57 (25).
Anal. Calcd. for C44H52N4: C, 82.97; H, 8.23; N, 8.80. Found:
C, 82.59; H, 8.11; N, 8.45.
3,3'-Bis-[naphthalen-1-ylimino]-1,3,1',3'-tetrahydro[2,2']bi[benz-
[g]indolylidene] (2d).
[15] D. Lindauer, R. Beckert, T. Billert, M. Döring, H. Görls, J.
Prakt. Chem., 337, 508 (1995).
This compound was obtained as dark purple solid, 92 mg
(31%), mp 258°C (decomp.); ir (ATR): 3347 (w) (N-H), 3049
(w) (arC-H), 1658 (w) (C=N) cm-1; uv/vis (DMF) ꢀ (logꢁ) 285
(4.6), 336 (4.1), 514 (3.8); 1H nmr (250 MHz, DMSO-d6): ꢂ 10.5
(s, 2H), 7.61-7.43 (m, 14H), 7.26-7.14 ppm (m, 12H); ms: m/z
(DEI) 612 (100) (M+), 485 (10), 470 (20), 396 (15), 306 (10),
143 (20), 28 (100).
[16] CCDC 296002 (6g) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or deposit@ccdc.cam.ac.uk).
[17] H. t. Dieck, B. Bruder, K.-D. Franz, Chem. Ber., 116, 136
(1983).
Anal. Calcd. for C44H28N4: C, 86.25; H, 4.61; N, 9.14. Found:
C, 85.95; H, 4.25; N, 8.90.
[18] A. R. Katritzky, B. Yang, N. S. Dalal, J. Org. Chem., 63,
1467 (1998).
[2,2-Di-n-butyl-1,2-dihydro-indol-(3)-ylidene]-4-tolyl-amine (7).
[19] COLLECT, Data Collection Software; Nonius B.V.,
Netherlands, (1998).
This compound was obtained (following procedure a) as
yellow solid, 140mg (42%), mp 145°C (decomp.); ir (ATR):
3253 (w) (N-H), 3022 (w) (arC-H), 1638 (m) (C=N) cm-1; uv/vis
(CHCl3) ꢀ (logꢁ) 263 (3.9), 379 (3.7); 1H nmr (400 MHz,
CDCl3): ꢂ 7.13 (m, 3H), 6.76 (d, 7.6 Hz, 2H), 6.71-6.69 (m, 1H),
6.40-6.31 (m, 2H), 4.2 (br, s, 1H), 2.40 (s, 3H), 1.84 (m, 2H),
1.65 (m, 2H), 1.24 (m, 8H), 0.86 ppm (m, 6H); 13C nmr (63
[20] Z. Otwinowski
& W. Minor, „Processing of X-Ray
Diffraction Data Collected in Oscillation Mode“, in Methods in
Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited
by C.W. Carter & R.M. Weet, pp. 307-326, Academic Press, (1997).
[21] G.M. Sheldrick, Acta Crystallogr. Sect. A, 46, 467 (1990).
[22] G.M. Sheldrick, SHELXL-97, University of Göttingen,
Germany, (1997).
[23] R. Bauer, Chem. Ber., 40, 2653 (1907).
MHz, CDCl3): ꢂ 172.1 (C=N), 156.2 (N=C-C), 148.9 (Cindol
-
[24] Ethyl (2-bromophenylamino)oxoacetate (This compound was
obtained as colorless oil; 1H nmr (250 MHz, DMSO-d6): ꢂ 10.23 (s, 1H),
7.77-7.68 (m, 2H), 7.45-7.39 (m, 1H), 7.23-7.19 (m, 1H), 4.30 (q, J =
7.1Hz, 2H), 1.31 ppm (t, J = 7.1Hz, 3H); 13C nmr (63 MHz, DMSO-d6):
ꢂ 160.2, 155.3, 134.7, 132.7, 129.1, 128.3, 125.7, 117.7, 62.6, 13.7 ppm.
Anal. Calcd. for C10H10BrNO3: C, 44.14; H, 3.70; Br, 29.37; N, 5.15; O,
17.64; Found: C, 44.23; H, 3.49; Br, 29.47; N, 5.08.)
NH), 132.4 (Cquat), 131.4 (Cquat), 128.9 (indol-CH), 128.0 (Cquat),
118.8 (tolyl-CH), 117.8 (indol-CH), 116.1 (indol-CH), 109.9
(tolyl-CH), 67.8 (Cspiro), 39.3, 24.4, 22.1 (butyl-CH2), 20.4 (tolyl-
CH3), 13.1 (butyl-CH3) ppm; ms: m/z (DEI) 334 (M+) (5), 291,
278 (100), 235 (50), 219 (25), 186 (15), 91 (30), 41 (40).
Anal. Calcd. for C23H30N2: C, 82.59; H, 9.04; N, 8.37. Found:
C, 82.22; H, 8.72; N, 8.09.
[25] N1-(2-Bromophenyl)-N2-4-tolyloxalamide (This compound
was obtained as white solid, mp: 177°C; ir (ATR): 3282 (m) (N-H),
3033 (w) (arC-H), 1664 (s) (C=O); 1H nmr (250 MHz, DMSO-d6): ꢂ
10.71 (br, s, 1H), 10.31 (br, s, 1H), 7.99 (d, J = 10 Hz, 1H), 7.76-7.70
(m, 3H), 7.46 (t, J = 7.5Hz, 1H), 7.22-7.15 (m, 3H), 2.27 ppm (s, 3H);
13C nmr (63 MHz, DMSO-d6): ꢂ 158.4, 158.1, 157.8, 135.1, 133.9,
132.7, 129.1, 128.5, 127.3, 124.0, 120.5, 120.3, 116.4, 20.5 ppm. Anal.
Calcd. for C15H13BrN2O2: C, 54.07; H, 3.93; Br, 23.98; N, 8.41; O, 9.60;
Found: C, 54.65; H, 4.05; Br, 23.48; N, 8.30.).
REFERENCES AND NOTES
[1] A. W. Hofmann, Liebigs Ann. Chem., 144, 114 (1867).
[2] E. Grandmougin, E. Dessoulavy, Chem. Ber., 42, 3638
(1909).
[3] C. Grundmann, Chem. Ber., 91, 1380 (1958).
[4] M. Wenzel, F. Lehmann, R. Beckert, W. Günther, H. Görls,
Monatshefte Chem., 130, 1373 (1999).
[5] P. Langer, M. Döring, Eur. J. Org. Chem., 221 (2002) and
cited herein; C. Käpplinger, R. Beckert, W. Imhof, J. Prakt. Chem., 340,
323 (1998).
[6] H. J. Bestmann, G. Schmid, E. Wilhelm, Angew. Chem., 92,
134 (1980).
[26] N1-(2-Bromo-phenyl)-N2-4-tolyl-oxalodiimidoyl dichloride
(This compound was obtained after recrystallisation from n-heptane as
1
yellow needles, mp: 63°C; H nmr (250 MHz, CDCl3): ꢂ 7.56-6.91 (m,
8H), 2.31 ppm (s, 3H); 13C nmr (63 MHz, DMSO-d6): ꢂ 145.4, 142.7,
137.5, 133.1, 129.6, 128.7, 127.9, 127.2, 122.4, 120.1, 114.1, 21.2 ppm.
Anal. Calcd. for C15H11BrCl2N2: C, 48.68; H, 3.00; Br, 21.59; Cl, 19.16;
N, 7.57; Found: C, 48.94; H, 3.45; N, 7.16.).