Unusual behaviour during the route of a Japp-Klingemann reaction

Article abstract of DOI:10.1515/znb-2010-0610

Performing a standard Japp-Klingemann synthesis that involved diazotation of 2,6-dinitroaniline and reaction with pentane-2,4-dione in aqueous hydrochloric acid medium surprisingly yielded a mixture of the expected 2,6-dinitro-and the unexpected 2-chloro-6-nitro-substituted hydrazones. This mixture was isolated as solid-solution crystals containing the components in an approximate ratio of 1 to 2. Based on both, selected compounds of comparison that show the aromatic ring substituents changed in position and intermediate diazonium salts, potential causal connections of the unusual behaviour during the route of the particular Japp-Klingemann reaction were studied. X-Ray crystal structures of the relevant compounds have been determined to support the discussion.

Full text of DOI:10.1515/znb-2010-0610

Unusual Behaviour During the Route of a Japp-Klingemann Reaction
Jan Martena, Wilhelm Seichtera, Jo¨rg Waglerb, and Edwin Webera
a Institut fu¨r Organische Chemie, TU Bergakademie Freiberg, Leipziger Straße 29, 09596 Freiberg/
Sachsen, Germany
b Institut fu¨r Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Straße 29, 09596 Freiberg/
Sachsen, Germany
Reprint requests to Prof. Dr. Edwin Weber. Fax: +49 3731 39 3170.
E-mail: edwin.weber@chemie.tu-freiberg.de
Z. Naturforsch. 2010, 65b, 745 – 752; received March 4, 2010
Performing a standard Japp-Klingemann synthesis that involved diazotation of 2,6-dinitroaniline
and reaction with pentane-2,4-dione in aqueous hydrochloric acid medium surprisingly yielded a
mixture of the expected 2,6-dinitro- and the unexpected 2-chloro-6-nitro-substituted hydrazones. This
mixture was isolated as solid-solution crystals containing the components in an approximate ratio of
1 to 2. Based on both, selected compounds of comparison that show the aromatic ring substituents
changed in position and intermediate diazonium salts, potential causal connections of the unusual
behaviour during the route of the particular Japp-Klingemann reaction were studied. X-Ray crystal
structures of the relevant compounds have been determined to support the discussion.
Key words: Pentane-2,4-dione, Anilines, Diazotation, Japp-Klingemann Reaction,
X-Ray Diffraction Analysis
Introduction
for their synthesis [2, 12]. This assumption has been
fully supported lately [14 – 16], until our recent stud-
ies revealed an unusual and remarkable case when
diazotised 2,6-dinitroaniline in aqueous hydrochloric
acid plus pentane-2,4-dione were used for the reaction.
The deviation from ordinary is shown in a partial re-
placement of one of the nitro groups by a chloro sub-
stituent at the aromatic ring. In our case, both the ex-
pected dinitrohydrazone 1 as well as the unexpected
2-chloro-6-nitro-substituted hydrazone 2 (Scheme 1)
were obtained in an approximate ratio of 1 to 2 not
only in solution but also in the form of a solid-solution
as single crystals, thus asking for an explanation.
One may assume that the chloro substituent orig-
inates from the hydrochloric acid of the reaction
The coupling reaction of a 1,3-dicarbonyl com-
pound with an aromatic diazonium salt to yield a cor-
responding arylhydrazone is a well developed standard
procedure, generally known as the Japp-Klingemann
reaction [1]. It is mostly performed in acetate-buffered
methanolic solution [2]. This method has given rise to
an immense variety of arylhydrazones derived from
various arylamines and 1,3-dicarbonyl compounds
[3, 4]. In this course, the respective aniline requires a
preceeding diazotation with sodium nitrite in acidic
medium to produce the corresponding diazonium salt
[5], which is an inevitable part of the full synthetic
route of a Japp-Klingemann mode of conversion.
Arylhydrazones obtained by the Japp-Klingemann medium, but at which step of the synthesis route the
reaction are in the focus of scientific interest due to exchange could have taken place, either the diazonium
their tautomerism behaviour [6], providing a promising salt or the hydrazone level, has remained uncertain. In
tool for the design of functional materials attributed to order to clarify these facts, an extended study including
smart (resonance-assisted) [7] hydrogen bonding [8]. the X-ray diffraction analysis of single crystals con-
Furthermore, their action as antineoplastic compounds taining both compounds, 1 and 2, as a solid-solution,
[9] or chelate ligands for the complexation of transi- and the preparation and X-ray crystal structure de-
tion metal ions is of scientific interest [10 – 13]. Hence, termination of several appropriately constituted com-
arylhydrazones of this type represent a rather impor- pounds of comparison (3 – 6) (Scheme 1) were carried
tant class of compounds with the Japp-Klingemann re- out. The discussion also covers the known structure of
action being a significant and highly reliable approach compound 1, prepared by a modified procedure [15].
c
0932–0776 / 10 / 0600–0745 $ 06.00 ꢀ 2010 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
Scheme 1. Compounds studied in this paper.
Results and Discussion
a similar nitro for chloro exchange will also occur dur-
ing the course of a corresponding Japp-Klingemann re-
Japp-Klingemann reactions and preparation of refer-
ence compounds
action if a structurally modified dinitroaniline in hy-
drochloric acid medium, such as 2,4- instead of 2,6-
dinitroaniline, is used. The findings are that the con-
stitutional isomeric dinitrohydrazone 3 (Scheme 1)
is formed in nearly quantitative yield. According to
these results, one can conclude that the position of
the two nitro substituents at the aryl ring is the im-
portant parameter for the unusual reaction behaviour
rather than their mere presence. This seems to be in
agreement with earlier findings, showing that the ef-
ficient nucleophilic substitution of a nitro group re-
quires a position of particular activation [18, 19] or
the presence of an activating reaction medium [20],
including a phase-transfer catalyst (Halex process)
[21, 22]. However, subsequent treatment of the 2,6-
dinitrophenylhydrazone 1 (alternatively prepared in
sulphuric acid medium) with 3N hydrochloric acid for
5 h at 50 ◦C did not lead to the chloro derivative 2.
This tempted us to study the corresponding diazo-
nium compounds, as the key intermediates of the reac-
tion, since the reason for the unexpected replacement
of nitro by chloro may be found at an earlier stage of
the reaction. In order to obtain stable crystals for the
structural study, the respective diazonium salts were
isolated as the corresponding tetrafluoroborates 4 and
As mentioned above, the reaction of diazotised 2,6-
dinitroaniline in aqueous 3N hydrochloric acid with
pentane-2,4-dione under standard Japp-Klingemann
conditions led to the formation of a product which
contains, according to 1H NMR analysis, the ex-
pected dinitro hydrazone 1 and another unexpected
2,6-disubstituted hydrazone in a ratio close to 1 : 2. The
latter was then shown to be the chloro-nitro-substituted
hydrazone 2 (vide infra). Without doubt, the chloro
substituent is causally connected to the hydrochloric
acid, but the way of replacement of the nitro group by
a chlorine atom has remained unclear. Hence, on avoid-
ing the chloride source by the use of sulphuric acid in-
stead of hydrochloric acid in the reaction protocol, the
mixed chloro nitro hydrazone should not appear. In-
deed, in the absence of chloride, the reaction proceeded
expectedly normal without substitution of a nitro
group, producing the hydrazone 1 in high yield [15].
The different reaction outcomes from hydrochloric
versus sulphuric acid medium suggest a nucleophilic
attack of the chloride versus the sulphate or hydrogen
sulphate ions, which is in agreement with the rather
poor nucleophilic behaviour of the latter anions [17].
Prompted by the unexpected formation of single 5 (Scheme 1). Although these compounds are suffi-
crystals containing both compounds, 1 and 2, as a ciently stable in the solid state, they vigorously decom-
solid-solution (vide infra), the question arose whether pose upon heating or in contact with various solvents
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
747
and should be handled only in small quantities and with responding atoms of the two compounds sharing iden-
caution (see Experimental Section)! For a short-time tical positions while only the nitro group N(4), O(5),
storage, the covering with a layer of tetrafluoroboric O(6) and the chlorine atom Cl(1) occupy different ones
acid is recommended.
(Fig. 1). The ratio of 1 to 2 in the crystal was found to
In a final experiment, 2,6-dinitrobenzenediazonium be 0.31 to 0.69 by refinement, close to the experimental
tetrafluoroborate (4) was treated with 3N aqueous hy- ratio of 1 to 2 in solution (vide supra).
drochloric acid, in order to probe its chemical be-
haviour under the conditions comparable to the ini-
tial Japp-Klingemann route. As a result of this treat-
ment, a clear replacement of the diazonium group by
a chlorine atom occurred, suggesting a nucleophilic
substitution reaction with loss of gaseous nitrogen
and the formation of tetrafluoroboric acid to yield
2,6-dinitrochlorobenzene (6) (Scheme 1). It seems
obvious that this conversion follows an uncatalysed
Sandmeyer-like dediazoniation reaction supported by
the electron-withdrawing nitro groups [23, 24].
Both molecules exhibit a high degree of coplanarity
with respect to the hydrazone and phenyl moieties.
This structural feature, being a general phenomenon in
this class of compounds [14 – 16], is a known conse-
quence of the formation of an intramolecular hydro-
gen bridge within the hydrazone subunit and π con-
jugation with the aryl ring. In 1 (Fig. 1a), one of the
nitro groups is involved in a contact to the (C=O)O-
N bridging hydrogen, giving rise to a three-centre hy-
drogen contact [O(1)···H(2)···O(6)]. Resulting there-
from, this nitro group is nearly coplanar with the aryl
ring. The other nitro group of compound 1 is notice-
ably out of plane with respect to the aryl unit due to
the repulsive interference with the lone pair of elec-
trons at N(1) [15]. Thus, it is worth mentioning that
the nitro group at C(11) of compound 2 is also out of
plane, whereas the chloro substituent is neighbouring
the position of the cyclic hydrogen bridge O(1)···H–
N(2) (Fig. 1b). A further point of interest arises from a
structural comparison of compound 1 in the neat crys-
tal [15] and in the solid-solution with 2. It is demon-
strated that 1 in the two different environments shows
rather conformable molecular geometries. This refers
to the hydrogen-bridged ring system and also to the
different conformational orientation of the two nitro
groups.
X-Ray diffraction studies
X-Ray diffraction analysis of the hydrazones and the
diazonium salt intermediates were performed in order
to obtain potentially helpful information about the un-
common course of the Japp-Klingemann reaction.
Upon crystallization of the reaction product, sin-
gle crystals were obtained which contained 1 and 2 in
the form of a solid-solution. Crystals are monoclinic,
space group P21/n with Z = 4. This means that 1 and
2 are statistically disordered in the crystal, the cor-
(a)
The molecular packing in crystals of 1/2 features
a layer structure. The layers are stabilised by inter-
molecular C–H···O contacts [25, 26] involving the
aromatic carbon atom C(10) and the oxygen atom O(5)
of the hydrogen-bonded nitro group of a neighbouring
molecule. The chlorine atom of compound 2 gives rise
to a similar C–H···Cl contact. Another intermolecular
C–H···O contact referring to the dinitrophenylhydra-
zone is found between H(10) and O(1), which is also
present in the molecule of 2. The layers are stacked
to yield π···π interactions [27, 28] between the arene
rings as well as between the hydrogen-bonded hydra-
zone system and a neighbouringaromatic ring [15]. Al-
though the solid-solution composed of 1 and 2 reveals
interesting structural details, these data do not con-
tribute much to an explanation of the unusual course
(b)
Fig. 1. Molecular structures of the hydrazones 1 (a) and 2 (b)
in the solid-solution 1/2, including numbering schemes of the
non-hydrogen atoms. Displacement ellipsoids are at the 50 % of the Japp-Klingemann reaction in the case of 2,6-
probability level. Dashed lines represent hydrogen bonds.
dinitroaniline.
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
(a)
(b)
Fig. 2. Molecular structure of the hydrazone 3 with number-
ing scheme of the non-hydrogen atoms. Displacement ellip-
soids are at the 50 % probability level. Dashed lines represent
hydrogen bonds.
Irrespective of the different substitution pattern at
the phenyl group, the solid-state structure of the hydra-
zone 3 (Fig. 2) shows a high degree of correspondence
to the constitutionally isomeric hydrazone 1 in the
basic molecular geometry, including the bicyclic in-
tramolecular hydrogen-bonded ring system. However,
unlike 1, exhibiting the non-hydrogen-bonded ortho
nitro group remarkably out of the aromatic ring plane,
the para nitro group of 3 is nearly coplanar. Hence,
also this nitro group shares the resonance with the
arene unit, which is prevented in the case of 1 due
to steric interference with the lone pair of electrons of
N(1) [15]. As a result, the whole molecular geometry
of 3 (non-hydrogen atoms) features a quasi plane. The
crystalline packing mode of 3 can be described as com-
posed of hydrogen-bonded molecular strands that are
connected by weak C–H···O contacts [25, 26].
Fig. 3. Molecular structures of the diazonium salts 4 (a) and
5 (b), including numbering schemes of the non-hydrogen
atoms. Displacement ellipsoids are at the 50 % probability
level.
In the crystal structure of 2,6-dinitrobenzenedi-
azonium tetrafluoroborate (4), the nitro groups neigh-
bouring the diazonium unit are rotated considerably
out of the aryl ring plane (about 26◦). Hence, the NO2
moities detract from resonance, whereas the diazonium
moiety is almost coplanar (Fig. 3a). The packing of
4 shows a rather complex arrangement of diazonium
and tetrafluoroborate ions with B–F···N contacts [29].
Unlike 4, 2,4-dinitrobenzenediazonium tetrafluorobo-
rate (5) crystallises as a double salt (1 : 1) with sodium
tetrafluoroborate as the second component. Due to the
lower steric hindrance as compared with 4, both ni-
Fig. 4. Molecular structure of compound 6 with numbering
scheme of the non-hydrogen atoms, showing the priority po-
sition of the disordered nitro groups. Displacement ellipsoids
are at the 50 % probability level.
tably less rotated out of the aryl plane (interplanar an-
gles are 10 and 12◦). An X-ray diffraction analysis was
also performed of compound 6, revealing a molecular
structure (Fig. 4) with the two nitro groups being con-
formationally disordered in two positions of different
occupancies (85: 15 and 96 : 4).
Further details on the crystal structures are available
tro groups of the diazonium cation (Fig. 3b) are no- (see notes at the end of the paper for availability).
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
749
Conclusions
nucleophilic substitution by chloride. Nevertheless it is
an established fact that under particular circumstances
reactions following a Japp-Klingemann route can take
a course different from the normal case, such as shown
here.
Although the well-known Japp-Klingemann synthe-
sis [1], following the standard reaction protocol, usu-
ally produces the intended hydrazones [2 – 4], excep-
tions from this rule can occur. Such an exceptional
case is met with the Japp-Klingemann reaction of di- Experimental Section
azotised 2,6-dinitroaniline with pentane-2,4-dione in
NMR spectra (internal standard TMS) were recorded us-
aqueous hydrochloric acid, yielding aside from the ex-
pected 2,6-dinitrophenylhydrazone1 also the 2-chloro-
6-nitro derivative 2. These two compounds are capa-
ble of replacing each other in a crystal packing giving
rise to a solid-solution crystal. Since neither the reac-
tion using a mononitro-substituted arenediazoniumsalt
[14, 15] nor that with the constitutionally isomeric 2,4-
ing a Bruker Avance DPX 400 instrument. IR spectroscopy
was carried out on an FT-IR 510 Nicolet spectrometer. GC-
MS were determined with a Hewlett-Packard 5890 (Series
II/MS 5989A) spectrometer. The elemental analyses were
obtained using a Heraeus CHN rapid analyser. Organic sol-
vents were purified by standard procedures [37]. Anilines,
pentane-2,4-dione and tetrafluoroboric acid were purchased
dinitrobenzenediazonium salt produced a correspond- from Fluka.
ing chloro for nitro exchanged hydrazone but almost
quantitative yields of the intended hydrazones, the con-
clusion is that both the number and the position of
the nitro substituents are decisive factors. Moreover,
because a subsequently performed vigorous treatment
of the 2,6-dinitro-substituted hydrazone with 3N hy-
drochloric acid did not indicate any transformation
from 1 to 2, it must be assumed that the reason for
the exchange should be found at an earlier stage of the
reaction before the hydrazone is formed, i. e. the step
involving the diazonium salt. Supporting references in
the literature [30 – 32] show aromatic nitro substituents
to be good leaving groups (as nitrite) in the replace-
ment by halogen and other nucleophiles, dependent
on the temperature and the reaction time [30, 33 – 35].
This is a potential line of reasoning to explain the re-
sult of the experiment in general. It is also known that
aromatic nitro groups, being restrained due to the steric
demand of neighbouring substituents and thus rotated
out of the aromatic plane, are more easily replaced than
nitro groups in conjugation with the aromatic system
[36]. This observation is in agreement with the X-ray
structural data of the diazonium salts, showing the 2,6-
and the 2,4-dinitro derivatives with considerably high
and notably less rotation of the nitro groups out of the
aryl plane, respectively. However, since we were un-
able to isolate a chloro for nitro-substituted by-product
on reaction of the 2,6-dinitrobenzenediazonium cation
with 3N hydrochloric acid, the true path of the ex-
change reaction is not yet totally clear and requires
further more detailed investigation. For example, one
such investigation should analyse the potential pres-
ence of an arenediazotate which could add intramolec-
3-[(2,6-Dinitrophenyl)hydrazono]pentane-2,4-dione (1)
A solution of the diazonium salt, prepared from 2,6-di-
nitroaniline (3.66 g, 20.0 mmol) in conc. sulphuric acid
(20 mL) and saturated sodium nitrite (1.38 g, 20.0 mmol)
in distilled water at −5 ◦C, was added to a stirred mix-
ture of sodium acetate (7.50 g, 91.5 mmol), sodium hydr-
oxide (1.02 g, 25.0 mmol) and pentane-2,4-dione (2 mL,
1.90 g, 19.0 mmol) in methanol (160 mL) and distilled wa-
ter (160 mL). Stirring was continued for 1 h at r. t. The
crude product was collected by filtration and crystallised
from ethanol to yield 1 (4.83 g, 82 %) as yellow crystals,
m. p. 153 – 155 ◦C. Spectroscopic data correspond to the lit-
erature data [15].
3-[(2,6-Dinitrophenyl)hydrazono]pentane-2,4-dione (1) and
3-[(2-chloro-6-nitrophenyl)-hydrazono]pentane-2,4-dione
(2)
The same procedure as above applies, except for the cus-
tomary use of aqueous 3N hydrochloric acid (40 mL) instead
of sulphuric acid. Recrystallization from toluene yielded a
solid-solution of 1 and 2 in a 32 : 68 ratio as yellow crystals
(total yield 70 %), m. p. 178 – 180 ◦C. – 1H NMR (400 MHz,
CDCl3): δ = 2.34 and 2.61 (m, 12 H, CH3CO), 7.26 (d, 1 H,
Ar-H), 7.36 (d, 1 H, Ar-H), 8.18 (d, 2 H, Ar-H), 8.36 (m,
2 H, Ar-H), 15.17 (s, 2 H, NH) ppm. – 13C NMR (100 MHz,
CDCl3): δ = 26.3, 31.7, 123.0, 124.9, 130.1, 131.9, 137.6,
140.5, 197.0, 198.7 ppm. – MS (GC-MS): m/z = 294 (calcd.
294.06 for C11H10N4O6, [M]+), m/z = 284 [M+H]+ (calcd.
283.04 for C11H10ClN3O4 [M]+).
3-[(2,4-Dinitrophenyl)hydrazono]pentane-2,4-dione (3)
The same procedure as above with hydrochloric acid in-
ularly to the tilted nitro group and thus facilitate the stead of sulphuric acid applies. 2,4-Dinitroaniline was used
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
Table 1. Crystal data and numbers pertinent to data collection and refinement of 1/2 – 6.
Compound
1/2
3
4
5
6
Empirical formula
Formula weight, g mol−1
Crystal system
C11H10ClN4O4
297.68
monoclinic
P21/n
11.0580(3)
8.0282(2)
14.0430(4)
90
102.493(2)
90
C11H10N4O6
294.23
monoclinic
P21/n
4.8914(6)
17.676(3)
14.564(2)
90
94.364(6)
90
C6H3BF4N4O4
281.93
hexagonal
P63/m
12.0112(2)
12.0112(2)
11.8193(5)
90
90
120
1476.71(7)
6
1.90
C6H3B2F8NaN4O4
391.71
trigonal
R3c
20.0892(4)
20.0892(4)
13.9635(8)
90
90
120
4880.3(3)
6
1.95
C6H3ClN2O4
202.55
monoclinic
C2/c
13.223(4)
9.565(2)
13.479(4)
90
109.945(9)
90
Space group
˚
a, A
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
3
˚
V, A
1217.16(6)
4
1.62
1255.6(3)
4
1.56
1602.6(8)
8
1.68
Z
Dc, Mg m−3
Temperature, K
200(2)
40860 / 33.5
100.0
4775 / 0.0284
198
3849
0.0384 / 0.1104
0.0505 / 0.1173
0.410 / −0.186
153(2)
13425 / 22.0
99.8
1541 / 0.0539
196
1155
0.0367 / 0.0939
0.0582 / 0.1183
0.188 / −0.220
90(2)
64535 / 45.0
99.9
4201 / 0.0265
103
3706
0.0307 / 0.0912
0.0367 / 0.0963
0.839 / −0.736
93(2)
34374 / 35.0
99.8
2387 / 0.0267
205
2291
0.0326 / 0.0848
0.0344 / 0.0865
0.531 / −0.346
296(2)
7934 / 29.0
99.8
2125 / 0.0203
130
1527
0.0442 / 0.1231
0.0631 / 0.1314
0.199 / −0.280
Measured reflections / θmax, deg
Completeness, %
Unique reflections / Rint
Refined parameters
Reflections [I ≥ 2 σ(I)]
R1 / wR2 [I ≥ 2 σ(I)]
R1 / wR2 (all da−ta3)
˚
∆ρmax/min, e A
instead of 2,6-dinitroaniline. Recrystallization from ethanol preventing an NMR analysis. Warning! Cautious handling
yielded 3 (5.80 g, 98 %) as yellow crystals, m. p. 208 – 210 ◦C of this compound in small quantities is strongly advised!
(lit. [38]: 211 ◦C). – 1H NMR (400 MHz, CDCl3): δ = 2.63
and 2.71 (s, 6 H, CH3CO), 8.28 (d, 3J = 9.6 Hz, 1 H, Ar-H),
8.53 (d, 3J = 9.6 Hz, 1H, Ar-H), 9.22 (s, 1 H, Ar-H), 15.43
(s, 1 H, NH) ppm. – 13C NMR (100 MHz, CDCl3): δ = 26.8,
31.8, 117.9, 122.9, 129.9, 134.1, 138.5, 142.7, 142.9, 196.6,
197.6 ppm. – IR (KBr): ν = 3291, 1685, 1653, 1612, 1492,
1358 – 1342, 743 cm−1. – MS (GC-MS): m/z = 294 (calcd.
294.06 for C11H10N4O6 [M]+). – Analysis C11H10N4O6
(294.22): calcd. C 44.90, H 3.43, N 19.04; found C 44.95,
H 3.41, N 19.04.
5: Yield 4.90 g (81 %) of a yellow solid (dec. > 200 ◦C).
Warning! Decomposition hazards and precautionary advice
as before!
2,6-Dinitrochlorobenzene (6)
To 2,6-dinitrobenzenediazonium tetrafluoroborate (4)
(1.00 g, 5.10 mmol) was added 3N aqueous hydrochloric
acid (10 mL) under vigorous stirring at −5 ◦C. The mixture
◦
was allowed to warm up to r. t., slowly heated to 50 C and
stirred for 1 h at this temperature. The precipitate was col-
lected, washed twice with water (100 mL) and crystallised
from ethanol ◦to yield 6 (0.49 g, 47 %) as a colourless solid,
Preparation of 2,6-dinitrobenzenediazonium tetrafluoro-
borate (4) and 2,4-dinitrobenzenediazonium tetrafluoro-
borate (5)
1
m. p. 87 – 88 C (dec.) [39]. – H NMR data correspond to
the lit. data [40]. – 13C NMR (100 MHz, [D6]DMSO): δ =
General procedure
121.0, 130.1, 131.5, 148.9 ppm.
To a stirred and cooled (−5 ◦C) suspension of the respec-
tive dinitroaniline (3.66 g, 20.0 mmol) in tetrafluoroboric
acid (50 mL, 48 %) was added dropwise during 20 min an
ice-cooled solution of sodium nitrite (1.38 g, 20.0 mmol) in
distilled water (10 mL). The precipitate formed was collected
and washed with tetrafluoroboric acid (2 × 5 mL), ethanol
(2 × 10 mL) and diethyl ether (2 × 10 mL), in this sequence.
Data of the individual compounds are specified below.
X-Ray structure determinations
Single crystals of compounds 1/2, 3 and 6 suitable for
X-ray diffraction studies were obtained by slow evaporation
of solutions in ethanol. Crystals of compounds 4 and 5 were
obtained from the cooled mother liquor of the reactions after
3 d storage at 4 ◦C.
The reflection data were collected on a Bruker X8 APEX
4: Yield 5.20 g (92 %) of a yellow solid which decom- II diffractometer with graphite-monochromatised MoKα ra-
◦
˚
poses under violent explosion when heated above 200 C. diation (λ = 0.71073 A) using ω and ϕ scans. Reflections
Decomposition does also occur in contact with CDCl3, were corrected for background, Lorentz and polarisation ef-
D3COD, [D8]toluene, [D6]benzene, [D6]DMSO and D2O fects. Preliminary structure models were derived by applica-
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J. Marten et al. · Unusual Behaviour During the Route of a Japp-Klingemann Reaction
751
tion of Direct Methods [41] and were refined by full-matrix Supplementary information
least-squares calculations based on F2 for all reflections [42].
All C-bound hydrogen atoms were included in the model in
idealised positions (riding model), N-bound hydrogen atoms
were found by analysis of the residual electron density and
refined without bond length restraints.
CCDC 722411 (1/2), 722412 (3), 722413 (4), 722414
(5), and 722415 (6) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre
In 1/2 also the nitro group N(4), O(5), O(6) and the chlo- via www.ccdc.cam.ac.uk/data request/cif.
rine atom Cl(1) could be refined with anisotropic displace-
Further details on the crystal structures, including tables
ment parameters, but EADP constraints [42] were applied to of structure parameters and geometric parameters for non-co-
N(4) and Cl(1) while the sum of their respective refined oc- valent contacts as well as illustrations of the crystal packings
cupancies was constrained to be 1.0.
The crystal data and experimental parameters are sum-
marised in Table 1.
are available as Supplementary Information (online only):
www.znaturforsch.com/ab/v65b/c65b.htm.
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S1
Unusual Behaviour During the Route of a Japp-Klingemann
Reaction
Jan Marten,a Wilhelm Seichter,a Jörg Wagler,b and Edwin Webera
a
Institut für Organische Chemie, TU Bergakademie Freiberg, Leipziger Straße 29, D-09596
Freiberg/Sachsen, Germany
b
Institut für Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Straße 29, D-
09596 Freiberg/Sachsen, Germany
Supporting Information
Table S1.
Table S2.
Table S3.
Table S4.
Figure S1.
Structure parameters of compounds 1–3.
Geometric parameters for non-covalent contacts in compounds 1–3.
Structure parameters of compounds 4–6.
Geometric parameters for intermolecular contacts in compounds 4–6.
Packing illustration for the solid solution 1/2 (arbitrary choice of 1 vs. 2).
Heteroatoms are shaded; hydrogen bond type contacts are represented by
dashed lines.
Figure S2.
Figure S3.
Packing structure of the hydrazone 3. Heteroatoms are shaded; hydrogen bond
type contacts are represented by dashed lines.
Packing structure of the diazonium salt 4. Heteroatoms are shaded. Non-
covalent interactions are represented by dashed lines. The shaded areas indicate
the N···F contacts around a tetrafluoroborate anion.
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S2
Figure S4.
Figure S5.
Packing excerpt of the double salt 5 · NaBF4. Heteroatoms are shaded (Na as a
filled circle). Non-covalent interactions are represented by thin and dashed
lines, except for C-H bond. The tetrafluoroborate anions are illustrated with
disordered positions.
Packing illustration of compound 6. Heteroatoms are shaded; non-covalent
contacts are represented by dashed lines.
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S3
Table S1.
Structure parameters of compounds 1–3.
Compound
1 [15]
1/2
3
Bond lengths / Å
N(1)-N(2)
N(1)-C(3)
N(2)-C(6)
C(2)-C(3)
C(3)-C(4)
C(2)-O(1)
C(4)-O(2)
1.333(2)
1.307(2)
1.386(2)
1.495(2)
1.498(2)
1.226(2)
1.216(2)
1.325(1)
1.312(1)
1.387(1)
1.489(2)
1.495(2)
1.225(1)
1.214(2)
1.337(3)
1.305(3)
1.385(3)
1.501(4)
1.493(4)
1.230(3)
1.216(3)
Bond angles / °
C(3)-N(1)-N(2)
N(1)-N(2)-C(6)
N(1)-C(3)-C(2)
N(1)-C(3)-C(4)
C(2)-C(3)-C(4)
C(3)-C(2)-O(1)
C(3)-C(4)-O(2)
120.0(1)
118.8(1)
124.9(1)
114.0(1)
121.2(1)
119.2(2)
119.7(2)
119.8(1)
121.1(1)
123.8(1)
113.7(1)
122.5(1)
119.1(1)
121.0(1)
120.4(2)
118.7(2)
124.0(2)
113.7(2)
122.2(2)
118.5(2)
120.1(2)
Torsion angles / °
O(1)-C(2)-C(3)-N(1)
C(2)-C(3)-N(1)-N(2)
C(3)-N(1)-N(2)-C(6)
C(2)-C(3)-C(4)-O(2)
14.1(3)
-6.0(3)
177.3(2)
26.6(3)
8.2(2)
2.2(2)
-176.3(1)
-15.9(2)
12.4(4)
0.2(4)
-178.2(2)
-12.6(4)
Interplanar angles / °
pla(1)[a] · · ·pla(2)[b]
pla(1)[a] · · ·pla(3)[c]
pla(1)[a] · · ·pla(4)[d]
17.72(18)
67.04 (8)
8.70 (9 )
8.44
-
-
9.61
-
-
Least-squares plane through [a] C(6)-C(7)-C(8)-C(9)-C(10)-C(11), [b] H(2)-N(2)-N(1)-C(3)-C(2)-O(1),
[c] N(3)-O(3)-O(4), [d] N(4)-O(5)-O(6).
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S4
Table S2. Geometric parameters for non-covalent contacts in compounds 1–3.
Symmetry
Bond length / Å
Angle / °
D-H···A
Interaction
D-H
D···H
H···A
1 [15]
N(2)-H(2)···O(1)
N(2)-H(2)···O(5)
C(1)-H(1B)···O(2)
C(1)-H(1A)···O(4)
C(5)-H(5A)···O(3)
C(1)-H(1A)···O(6)
C(5)-H(5C)···O(6)
x, y, z
x, y, z
0.79
0.79
0.98
0.98
0.98
0.98
0.98
2.597(2)
2.605(2)
3.411(2)
3.123(2)
3.578(2)
3.323(2)
3.423(2)
2.01
2.01
2.57
2.64
2.63
2.53
2.46
130.9
130.4
143.2
139.3
163.1
138.2
167.6
x, 1-y, 0.5+z
1+x, y, z
x, 1-y, -0.5+z
0.5+x, 0.5-y, 0.5+z
-0.5+x, 0.5-y, -0.5+z
1/2
N(2)-H(2)···O(1)
N(2)-H(2)···O(5)
C(10)-H(10)···O(5)
C(10)-H(10)···O(1)
C(9)-H(9)···O(4)
C(10)-H(10)···Cl(1)
x, y, z
x, y, z
-2-x, 1-y, -z
-0.5+x, 1.5-y, -0.5+z
1.5-x, 0.5+y, -1.5-z
0.5+x, 0.5+y, 0.5+z
0.86
0.86
0.93
0.93
0.93
0.93
2.539
2.606
3.305
3.387
3.316
3.825
1.84
1.99
2.43
2.61
2.65
3.10
135.9
127.3
172.9
106.8
113.7
150.0
3
N(2)-H(2)···O(1)
N(2)-H(2)···O(3)
C(1)-H(1A)···O(6)
C(5)-H(5A)···O(2)
C(10)-H(10)···O(1)
x, y, z
x, y, z
2+x, 0.5-y, 0.5+z
-1+x, y, z
-1+x, 0.5-y,-0.5+z
0.95
0.95
0.98
0.98
0.95
2.568
2.619
3.440
3.396
3.298
1.88
1.93
2.59
2.48
2.39
128
128
145
155
160
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S5
Table S3.
Structure parameters of compounds 4–6.
Compound
4
5
6
Bond lengths / Å
N(1)-N(2)
N(2)-C(1)
C(2)-N(3)
N(3)-O(1)
N(3)-O(2)
C(1)-C(2)
B(1)-F(1-4)
C(2)-N(1)
C(6)-N(2)
N(1)-O(1)
N(2)-O(3)
N(1)-O(2)
N(2)-O(4)
1.098(1)
1.394(1)
1.464(1)
1.220(1)
1.221(1)
1.395(1)
1.372(2)-1.422(2)
-
-
-
-
-
-
1.093(2)
1.409(2)
1.461(2)
1.228(2)
1.219(2)
1.398(2)
1.362(3)-1.406(3)
-
-
-
-
-
-
-
-
-
-
-
-
-
1.476(2)
1.469(2)
1.229(2)
1.215(3)
1.193(2)
1.223(3)
Bond angles / °
N(1)-N(2)-C(1)
N(2)-C(1)-C(2)
C(1)-C(2)-N(3)
C(2)-N(3)-O(1)
C(2)-N(3)-O(2)
178.9(1)
119.9(1)
120.7(1)
117.2(1)
117.0(1)
175.4(2)
120.5(1)
122.0(1)
116.8(1)
117.5(1)
-
-
-
-
-
Torsion angles / °
N(2)-C(1)-C(2)-N(3)
C(1)-C(2)-N(3)-O(1)
C(1)-C(2)-N(3)-O(2)
C(3)-C(2)-N(3)-O(1)
-1.76(6)
6.6(2)
10.1(2)
-170.4(1)
-168.1(1)
-
-
-
-
154.38(4)
152.89(4)
-26.43(5)
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S6
Table S4.
Interaction
Geometric parameters for intermolecular contacts in compounds 4–6.
Symmetry
Bond length / Å
C-H / [B-F]
Angle / °
H···O,F / [F···F,N]
C-O,F / [B···F,N]
C-H···O,F / [B-F···F,N]
4
C(3)-H(3)···O(1)
C(3)-H(3)···O(2)
C(3)-H(3)···F(1)
B(1)-F(1)···F(1)
B(1)-F(1)···N(1)
1-x, 1-y, -0.5+z
1+x, y, 0.5-z
-x+y, -x, z
1-x+y, 1-x, z
x-y, x, -0.5+z
0.95
0.95
0.95
1.40 [B(1)-F(1)]
1.40 [B(1)-F(1)]
2.54
2.94
2.57
3.066
3.247
3.494
3.329 [B(1)···F(1)]
4.121 [B(1)···N(2)]
115
100
164
4.013 [B(1)-F(1)···F(1)]
2.889 [B(1)-F(1)···N(1)]
109.2 [B(1)-F(1)···F(1)]
145.7 [B(1)-F(1)···N(1)]
5
C(3)-H(3)···O(4)
C(5)-H(5)···F(2)
C(6)-H(6)···F(1)
1/3-x+y, 2/3-x, -1/3+z
x, x-y, 0.5+z
-x+y, y, 0.5+z
0.95
0.95
0.95
2.46
2.38
2.33
3.400
3.234
3.222
173
149
157
6
C(4)-H(4)···O(3)
C(5)-H(5)···O(1)
0.5-x, 0.5+y, 0.5-z
0.5+x, 1.5+y, 0.5+z
0.93
0.93
2.59
2.55
3.361
3.313
141.0
147.7

S7
Figure S1.
Packing illustration of the solid solution 1/2 (arbitrary choice of 1 vs. 2).
Heteroatoms are shaded; hydrogen bond type contacts are represented by
dashed lines.
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S8
Figure S2.
Packing structure of the hydrazone 3. Heteroatoms are shaded; hydrogen bond
type contacts are represented by dashed lines.
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S9
Figure S3.
Packing structure of the diazonium salt 4. Heteroatoms are shaded. Non-
covalent interactions are represented by dashed lines. The shaded areas indicate
the N···F contacts around a tetrafluoroborate anion.
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S10
Figure S4.
Packing exerpt of the double salt 5. NaBF4. Heteroatoms are shaded (Na as a
filled circle). Non-covalent interactions are represented by thin and dashed
lines, except for C-H bonds. The tetrafluoroborate anions are illustrated with
disordered positons.
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S11
Figure S5.
Paking illustration of compound 6. Heteroatoms are shaded; non-covalent
contacts are represented by dashed lines.
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