Synthesis and spectroscopic properties of 4a,14a-diazoniaanthra[1,2-a] anthracene and 13a,16a-diazoniahexaphene derived from 1,7-dimethylnaphthalene

Article abstract of DOI:10.1055/s-2006-926444

An improved preparation of 1,7-dimethylnaphthalene is presented, which is used as a precursor for the synthesis of diazoniahexacyclic salts, namely, 4a,14a-diazoniaanthra[1,2-a]anthracene (3) and 13a,16a-diazoniahexaphene (7). The influence of the reaction conditions on the formation of these isomers was investigated. Notably, the selectivity of the reactions depends significantly on the acid employed in the cyclization step. Both compounds exhibit similar absorption and fluorescence emission properties. Compound 3 exhibits a remarkable photopersistence in the solid state and in air-saturated aqueous solutions. However, diazoniahexaphene 7 undergoes rapid photodegradation in solution. X-ray diffraction analysis reveals that compound 3 adopts a helicene structure in the crystalline state. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-926444

FEATURE ARTICLE
1549
Synthesis and Spectroscopic Properties of 4a,14a-Diazoniaanthra[1,2-a]an-
thracene and 13a,16a-Diazoniahexaphene Derived from 1,7-Dimethylnaph-
thalene
D
iazoniapolycycli
n
c
S
alts
f
rom
t
1,7-Dim
o
e
thylnaphth
n
alene Granzhan,a Jan W. Bats,b Heiko Ihmels*a
a
Institut für Organische Chemie II, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany
Institut für Organische Chemie und Chemische Biologie, Johann-Wolfgang-Goethe-Universität Frankfurt, Marie-Curie-Str. 11,
60439 Frankfurt am Main, Germany
b
Fax +49(271)7404052; E-mail: ihmels@chemie.uni-siegen.de
Received 23 February 2006; revised 29 March 2006
Dedicated to Professor Jochen Mattay on the occasion of his 60th birthday
was made solely on the basis of electronic absorption
Abstract: An improved preparation of 1,7-dimethylnaphthalene is
presented, which is used as a precursor for the synthesis of diazonia-
hexacyclic salts, namely, 4a,14a-diazoniaanthra[1,2-a]anthracene
(3) and 13a,16a-diazoniahexaphene (7). The influence of the reac-
spectra, although, in the latter case, the formation of the
isomeric diazoniahexaphene and diazoniahexacene could
not be excluded. We describe here our efforts towards the
tion conditions on the formation of these isomers was investigated. synthesis of 3, together with the spectroscopic properties
Notably, the selectivity of the reactions depends significantly on the
of this compound and of the isolated byproduct, namely
acid employed in the cyclization step. Both compounds exhibit sim-
13a,16a-diazoniahexaphene.
ilar absorption and fluorescence emission properties. Compound 3
exhibits a remarkable photopersistence in the solid state and in air-
saturated aqueous solutions. However, diazoniahexaphene 7 under-
2
1
3
4
goes rapid photodegradation in solution. X-ray diffraction analysis
reveals that compound 3 adopts a helicene structure in the crystal-
line state.
2 X–
X
Y
Q
Z
1: Q = Z = C, X = Y = N
2: Q = Z = N, X = Y = C
3: Q = Y = C, X = Z = N
Key words: arenes, cyclodehydration, helicenes, nitrogen hetero-
cycles, polycycles
Figure 1 The isomeric diazoniaanthra[1,2-a]anthracenes
Polyaromatic heterocyclic systems represent attractive
targets as functional materials,1 and are widely used in
bioorganic chemistry, e.g., for DNA recognition through
p–p interactions with stacked nucleic bases.2 Along these
lines, annelated derivatives of the quinolizinium ion rep-
resent an interesting class of heteroaromatic compounds
with a quaternary bridgehead nitrogen atom.3 Studies of
azonia aromatics are of particular interest since their char-
acteristic structure is found in alkaloids such as coralyne,
berberine and sempervirine, and thus constitutes a prom-
ising lead structure for DNA intercalators.4 In addition,
we have shown that the dicationic 12a,14a-diazoniapen-
taphene binds to the double-stranded DNA exclusively by
an intercalative binding mode with a high binding con-
stant, and exhibits DNA-photodamaging activity.5 More-
over, diazoniapolycyclic salts, especially hexacyclic
diazoniaanthra[1,2-a]anthracenes, are capable of selec-
tive and efficient stabilization of triple-helical DNA.6
The synthesis of 3 started from 1,7-dimethylnaphthalene
(4, Scheme 1). This compound is commercially available,
however, at a relatively high price. Moreover, reported
syntheses of 1,7-dimethylnaphthalene are rather tedious
and time-consuming. Thus, compound 4 has been pre-
pared in moderate yield by the intramolecular Friedel–
Crafts acylation of 4-(p-tolyl)butyric acid, followed by a
Grignard reaction of 7-methyl-1-tetralone and a subse-
quent dehydration–dehydrogenation procedure.9,10 4-(p-
Tolyl)butyric acid is, in turn, conveniently prepared in
two steps from toluene and succinic anhydride.10,11 Other
reported preparations of 4 include a six-step synthesis
from benzaldehyde via cyclization of an ylidenemalono-
dinitrile and deamination of 5-amino-1,7-dimethylnaphtha-
lene,12 as well as isomerization of the barely available 1,8-
dimethylnaphthalene with anhydrous hydrogen fluoride.13
In contrast, we have adopted the method of Leitch and co-
workers for the synthesis of substituted 2-methylnaphtha-
lenes.14 Thus, a Grignard reagent, prepared from the com-
mercially available 2-methylbenzyl bromide, was allowed
to react with 4,4-dimethoxybutan-2-one, and the interme-
diate alcohol was immediately subjected to cyclodehydra-
tion by HBr in acetic acid. This simple two-step procedure
gave 1,7-dimethylnaphthalene (4) in 38% yield. Radical
dibromination of 4 to compound 5, followed by the reac-
While two symmetrical diazoniahexacycles, 14a,16a-di-
azoniaanthra[1,2-a]anthracene (1, Figure 1)7 and 4a,10a-
diazoniaanthra[1,2-a]anthracene (2),8 have been de-
scribed several decades ago, the unsymmetrical isomer 3
was unknown. Moreover, structure assignment of 1 and 2
SYNTHESIS 2006, No. 9, pp 1549–1555
x
x
.
x
x
.2
0
0
6
Advanced online publication: 12.04.2006
DOI: 10.1055/s-2006-926444; Art ID: T02706SS
© Georg Thieme Verlag Stuttgart · New York

1550
A. Granzhan et al.
FEATURE ARTICLE
tion with two equivalents of 2-(1,3-dioxolan-2-yl)pyri- hydrous methanesulfonic acid resulted in an enhanced
dine,15 gave bispyridinium dibromide 6a, which was yield of 7 (60%, with a total yield of 85% for 3 and 7), al-
further converted into the corresponding tetrafluoroborate though the formation of the diazoniaanthra[1,2-a]an-
6b. However, the dicyclization under the conditions usu- thracene 3 could not be avoided completely. As it can be
ally employed for the synthesis of diazoniapolycycles seen from the data in Table 1, the reaction temperature has
(polyphosphoric acid, 150 °C, precipitation as tetrafluo- little effect on the isomer ratio, suggesting that the ther-
roborate salt)16 gave a mixture of the desired product 3 modynamic stability of the isomers is similar.
and the isomeric 13a,16a-diazoniahexaphene (7). Fortu-
Table 1 Influence of the Reaction Conditions on the Formation of
Dications 3 and 7
nately, laborious fractional crystallization of this mixture
from nitromethane allowed separating the isomers due to
the better solubility of salt 7.
Cyclization medi- Temp
Time
(h)
Overall
yield (%)
Ratio 3:7a
um
(°C)
150
180
120
128b
Since the condensation reactions of this type are often sus-
ceptible to the reaction parameters, such as cyclization
medium or temperature,3,17 we have investigated the reac-
tion under different conditions (Table 1). Most notably,
cyclodehydration in refluxing aqueous HBr gave com-
pound 3 exclusively, which is therefore the preferred
method of its preparation. However, the overall yield of
the cyclization product in this case is somewhat lower
(54% vs. 82–95% in case of PPA), presumably due to a
competing nucleophilic substitution of pyridinium resi-
dues with a bromide ion.16b On the contrary, the use of an-
PPA
24
95
82
85
54
37: 63
43: 57
29: 71
> 95: 5
PPA
20
MeSO3H
HBr (aq 48%)
1.5
3.5
a Determined by 1H NMR spectroscopy; estimated error 5%.
b Reflux.
Biographical Sketches
Anton Granzhan was born ceived his Diploma in 2002, degree include the synthesis
in Rubizhne, Ukraine in he joined the group of Prof. and investigations of azonia
1979. After studying at the Dr. Heiko Ihmels at the Uni- heterocycles as ligands for
National Technical Univer- versity of Siegen, Germany. higher-order DNA struc-
sity in Kiev, where he re- His studies towards the PhD tures.
Jan Willem Bats was born years as a research fellow at many. His research interests
in 1949 in the Netherlands. the State University of New are crystal structure deter-
He studied chemistry and York at Buffalo, USA. mination and phase transi-
obtained his doctoral degree Since 1977 he is a crystal- tions, polymorphism and
from Twente University of lographer at the University pseudo-symmetry in molec-
Technology. He spent two of Frankfurt am Main, Ger- ular crystals.
Heiko Ihmels was born in of British Columbia, Van- terests lie in the field of or-
1966 in Varel, Germany. He couver, Canada. He joined ganic photochemistry and
received both his Diploma the University of Würzburg, photobiology, and in partic-
(1992) and his PhD (1995, Germany, in 1997, where he ular in the design of novel
with J. Belzner and A. de obtained his habilitation in fluorescence sensors, in
Meijere) from the Universi- Organic Chemistry in 2002. DNA-binding and DNA-
ty of Göttingen, Germany. Since 2003 he occupies a photodamaging properties
He enjoyed 15 months as a Chair of Organic Chemistry of organic dyes, and in sol-
postdoctoral fellow with J. at the University of Siegen, id-state photoreactions.
R. Scheffer at the University Germany. His research in-
Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York

FEATURE ARTICLE
Diazoniapolycyclic Salts from 1,7-Dimethylnaphthalene
1551
Br
O
OMe
OMe
i, ii
iii
iv
Br
Br
4
5
O
2
1
3
4
O
O
N
O
N
N
N
N
vi
N
2 Br–
–
–
2 BF4
2 BF4
7
3
6
v
–
2 BF4
Scheme 1 Reagents and conditions: (i) Mg, Et2O; (ii) HBr, AcOH, reflux, 2 h (38%); (iii) NBS, (PhCOO)2, CCl4, reflux, 4 h (49%); (iv) (1,3-
dioxolan-2-yl)pyridine, NMP, r.t., 7 d; (v) aq NaBF4 (67%); (vi) PPA, 150 °C, 24 h (95%, 3:7 = 37:63).
1
The structures of 3 and 7 were assigned by H and 13C al C–H···F contacts with H···F distances between 2.60 and
NMR spectroscopy, {15N, 1H}-correlation NMR spectros- 2.66 Å. Moreover, an intermolecular p-stacking between
copy, mass-spectrometric and elemental analyses. In par- two benzo[b]quinolizinium moieties was observed; thus,
ticular, the NOE interaction patterns for the two isomers the distance between the meso atoms of ring B of one mole-
are significantly different (Figure 2). Moreover, the struc- cule and ring E of the p-stacked neighboring molecule is
ture of 3 is firmly supported by a single-crystal X-ray dif- 3.82 Å (Figure 3). The remaining rings are separated by a
fraction analysis (Figure 3).
larger distance (ca. 3.9 Å) due to the distortion of the C/D
rings.
Similarly to the parent hydrocarbons,19 diazoniapolycy-
clic salts usually exhibit a strong absorption in the UV re-
gion of the electromagnetic spectrum, along with
characteristic fluorescence properties. Interestingly, the
absorption spectra of 3 and 7 (Figure 4, A) are, to a signif-
icant extent, similar and consist of several strong p- and
b-absorption bands in the UV region (emax = 4.68 × 104
cm–1 M–1 for 3 and 8.24 × 104 cm–1 M–1 for 7) and much
weaker a-bands in the visible region (400–500 nm). The
spectra of diazoniahexaphene 7 are red-shifted by 4–8 nm
compared to isomer 3 and consist of sharper bands than
observed for 3, presumably due to the deviation from pla-
narity in the latter case.20 Hence, electronic absorption
spectra are not appropriate to distinguish these two iso-
Figure 2 1H (straight) and 15N NMR (italics) shifts (in DMSO-d6)
and characteristic NOE effects in 7
The compound crystallizes in the monoclinic space group mers, as it has been done in the previous work.8
C2/c (Table 2) with an equal number of P- and M-enantio-
mers. Notably, the unsymmetrical cations possess a crys-
tallographic two-fold axis through the C7a–C15b bond.
As it is the case in helicene-like molecules, the cations are
twisted to avoid short intramolecular C–H···H–C contacts.
The shortest intramolecular contact distances are
H15···H16 (1.96 Å) and H15···C16 (2.47 Å). The angle
between the planes of the two quinolizinium fragments
comprises 30.7°. The C1–C2, C3–C4 and C6–C7 bond
lengths are considerably shorter than the remaining C–C
bonds. A similar bond length alternation has been ob-
served in related quinolizinium derivatives.18
Even more pronounced similarity was observed in the flu-
orescence emission spectra of 3 and 7 (Figure 4, B). Emis-
sion spectra consist of well-resolved bands, and the
emission maxima of diazoniahexaphene 7 are red-shifted
by 5–6 nm compared to isomer 3. The fluorescence quan-
tum yields in aqueous solutions are 0.38 and 0.42 for 3 and
7, respectively, and thus lay in the characteristic range of
unsubstituted diazoniapolycycles.16a
It is noteworthy that the parent hydrocarbon of 3, namely
anthra[1,2-a]anthracene, is not persistent under aerobic
conditions due to rapid oxidation and could not be puri-
fied so far.21 In contrast, salts 3 and 7 are persistent in the
solid state and in acidic or neutral aqueous solutions. In
fact, we did not observe any photoreaction upon pro-
longed irradiation of crystalline 3 with UV light
The cations are connected to the anions by intermolecular
C–H···F interactions. There are five C–H···F contacts with
H···F distances between 2.27 and 2.52 Å and six addition-
Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York

1552
A. Granzhan et al.
FEATURE ARTICLE
Figure 4 Absorption (A) and normalized fluorescence emission (B,
l
ex = 368 nm) spectra of salts 3 (solid lines) and 7 (dashed lines) in
water
Figure 3 (A) Molecular structure of 3 in the solid state (The non-H
atoms are shown with 50% probability ellipsoids.); (B) Crystal
packing of 3 viewed down the b-axis
(lL = 350 nm), which is surprising considering the favor-
able intercationic distances (vide supra). It is noteworthy
that the distance between the aromatic ring planes in pho-
toreactive acridizinium salts usually constitutes 3.8–
3.9 Å.18a In contrast, in air-saturated aqueous solution
both diazoniapolycycles undergo photodegradation,
whereas salt 3 shows much higher photopersistence than
isomer 7 (Figure 5). Thus, estimated half-life times at
these conditions (see experimental section) are
250 minutes and 37 minutes for 3 and 7, respectively.
Figure 5 Relative decline of absorption during photodegradation of
3 (filled circles and solid lines) and 7 (open circles and dashed lines)
in air-saturated aqueous solutions (see experimental section for de-
tails)
In summary, we have described the synthesis and spectro-
scopic properties of two isomeric diazoniahexacycles 3
and 7, derived from 1,7-dimethylnaphthalene (4). In the
course of our studies, we have developed a significantly
Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York

FEATURE ARTICLE
Diazoniapolycyclic Salts from 1,7-Dimethylnaphthalene
1553
moval of the solvent in vacuo, the residual oil was vacuum-distilled
(14–15 mbar), collecting the fraction boiling at 125–130 °C.
ized diazonia derivative of hexaphene. Spectrophoto- Colorless liquid; yield 17.8 g (38%); nD20 1.6056 (Lit.10 1.6068).
improved approach for the synthesis of precursor 4. Nota-
bly, compound 7 is the first isolated and fully character-
1H NMR (400 MHz, CDCl3): d = 2.59 (s, 3 H), 2.71 (s, 3 H), 7.32–
7.37 (complex m, 3 H), 7.70 (d, 3J = 7.1 Hz, 1 H), 7.77–7.80 (com-
plex m, 2 H).
13C NMR (100 MHz, CDCl3): d = 19.6 (CH3), 22.3 (CH3), 123.4
(CH), 124.8 (CH), 126.3 (CH), 126.8 (CH), 127.9 (CH), 128.5
(CH), 131.9 (Cq), 132.9 (Cq), 133.7 (Cq), 135.5 (Cq).
metric and spectrofluorimetric properties of the new com-
pounds have been investigated and found to be rather sim-
ilar. Further investigation of these intriguing compounds,
in particular studies of their interactions with nucleic ac-
ids, is in progress.
All commercially available chemicals were reagent grade and used
without further purification. Solvents were purified and dried ac-
cording to standard procedures. The melting points were measured
with a melting-point apparatus (Büchi 510K) and are uncorrected.
Mass spectra (ESI in the positive-ion mode) were recorded with a
Finnigan LCQ Deca instrument (source voltage 6 kV). NMR spec-
tra were measured on a Brucker Avance 400 (1H: 400 MHz,
13C: 100 MHz) spectrometer at 20 °C; chemical shifts are given in
ppm (d) values (internal standard TMS). Elemental microanalyses
of all new compounds were performed at a HEKAtech EuroEA
combustion analyzer by Mr. H. Bodenstedt (Institut für Organische
Chemie, Universität Siegen). UV-visible spectra were recorded on
a Varian Cary 100 double-beam spectrophotometer; corrected
steady-state emission spectra were recorded on a Varian Cary
Eclipse fluorescence spectrometer. All spectrophotometric mea-
surements were performed in quartz sample cells at 20 °C, using
spectral grade solvents (Fluka). Working solutions were freshly pre-
pared by dilution of stock solutions (1 × 10–3 M in MeCN). If not
stated otherwise, the solution concentrations were 20 mM for ab-
sorption spectroscopy and 5 mM for fluorescence spectroscopy.
Spectrophotometer slit widths were kept at 2 nm for absorption
spectroscopy and at 2.5 nm for fluorescence spectroscopy. The rel-
ative fluorescence quantum yields were determined by the standard
method22 with Coumarin 1 (Aldrich, FF = 0.73 in EtOH)23 as a ref-
erence; refractive indices of the solvents were taken into account.
1,7-Bis(bromomethyl)naphthalene (5)
To a boiling solution of 1,7-dimethylnaphthalene (4; 6.25 g,
40.0 mmol) in CCl4 (150 mL), a mixture of NBS (15.0 g,
84.0 mmol) and benzoyl peroxide (0.10 g) was added in several
portions within 30 min. After completion of the addition, the reac-
tion mixture was heated under reflux for further 3.5 h and cooled to
r.t. The mixture was filtered and the residue was washed with
CH2Cl2 (5 × 20 mL). The filtrate was evaporated in vacuo; the resi-
due was completely dissolved in CH2Cl2 (ca. 200 mL) and washed
with ice-cold H2O (3 × 50 mL). The organic layer was dried
(Na2SO4) and the solvent removed in vacuo to give a pale-yellow
residue (11.9 g). The raw product was recrystallized from CHCl3–
n-hexane (1:1) yielding the product in form of fine colorless nee-
dles.
Yield: 6.10 g (49%); mp 129–130 °C (Lit.25 132 °C); Rf = 0.57
(SiO2; n-hexane–EtOAc, 8:2).
1H NMR (400 MHz, CDCl3): d = 4.72 (s, 2 H, C7-CH2Br), 4.95 (s,
2 H, C1-CH2Br), 7.42 (dd, 3J = 8.1 Hz, 3J = 8.3 Hz, 1 H, 3-H),
7.55–7.57 (complex m, 2 H, 2-H, 6-H), 7.82 (d, 3J = 8.3 Hz, 1 H, 4-
H), 7.88 (d, 3J = 8.3 Hz, 1 H, 5-H), 8.12 (s, 1 H, 8-H).
13C NMR (100 MHz, CDCl3): d = 31.6 (CH2Br), 34.3 (CH2Br),
123.9 (CH), 126.3 (CH), 127.4 (CH), 128.5 (CH), 129.7 (CH),
129.9 (CH), 131.1 (Cq), 133.6 (Cq), 133.9 (Cq), 136.1 (Cq).
1,7-Bis{[1-(1,3-dioxolan-2-yl)pyridinium]methyl}naphthalene
Dibromide (6a) and 1,7-Bis{[1-(1,3-dioxolan-2-yl)pyridini-
um]methyl}naphthalene Bis(tetrafluoroborate) (6b)
To a solution of 1,7-bis(bromomethyl)naphthalene (5; 3.14 g,
10.0 mmol) in N-methyl-2-pyrrolidone (10 mL), 2-(1,3-dioxolan-2-
yl)pyridine15 (3.63 g, 24.0 mmol) was added. The reaction mixture
was stirred for 7 d under moisture protection and then poured into
EtOAc (250 mL). The precipitate was separated, washed several
times with EtOAc and anhyd Et2O, and dried in vacuo (P2O5) to give
dibromide salt 6a as a white hygroscopic solid.
1,7-Dimethylnaphthalene (4)
2-Methylbenzylmagnesium bromide was prepared by dropwise ad-
dition of 2-methylbenzyl bromide (58.6 g, 42.5 mL, 317 mmol),
dissolved in anhyd Et2O (200 mL), to Mg turnings (9.20 g,
380 mmol), suspended in anhyd Et2O (50 mL). After the addition
was complete (1.5 h), the reaction mixture was heated under reflux
for 30 min and cooled to r.t. A solution of acetylacetaldehyde di-
methyl acetal (40.2 g, 304 mmol) in anhyd Et2O (65 mL) was added
dropwise within 30 min under vigorous stirring, whereas a clammy,
voluminous pale-yellow precipitate has formed. After the addition
was complete, the reaction mixture was heated under reflux for
15 h, during which the precipitate became orange-red. After cool-
ing, the reaction mixture was poured onto a mixture of ice (125 g)
and sat. NH4Cl solution (190 mL). The solid mass from the reaction
flask was triturated and also transferred into an aq NH4Cl–Et2O
mixture, and the latter was stirred until almost all solid material was
dissolved. The emulsion was filtered through a paper filter and
transferred into a separatory funnel. The organic layer was separat-
ed. The aqueous layer was extracted with Et2O (3 × 130 mL), and
organic layers were combined, washed with H2O (100 mL), brine
(150 mL) and were dried (Na2SO4). Removal of the solvent in vac-
uo gave crude 4,4-dimethoxy-2-methyl-1-(2-tolyl)butan-2-ol as
yellow oil (55.2 g; purity by 1H NMR spectroscopy 90%).24 The lat-
ter was dissolved in AcOH (320 mL), and 48% aq HBr (250 mL)
was added. The reaction mixture was stirred at 105–110 °C (weak
reflux) for 2 h. After cooling to 50 °C, a part of the solvent (ca.
250 mL) was evaporated in vacuo (50 mbar, 50–60 °C), and the
black residue was poured onto ice (320 g). The mixture was extract-
ed with CH2Cl2 (3 × 250 mL), and the combined organic layers
were washed with H2O (100 mL) and dried (Na2SO4). After re-
A portion of it (3.08 g, 5.00 mmol) was dissolved in H2O (5 mL)
and treated with a solution of NaBF4 (2.2 g, 20 mmol) in water
(3 mL). The emulsion was gently heated until a clear solution was
obtained. Upon slow cooling to 4 °C, a crystalline solid precipitat-
ed. It was separated, washed with plenty of cold water, and dried in
vacuo (P2O5), to give bis(tetrafluoroborate) 6b as a white microc-
rystalline solid.
Yield: 2.10 g (67%); mp 120–121 °C (H2O).
1H NMR (400 MHz, DMSO-d6): d = 4.11–4.15 [complex m, 8 H,
CH(OCH2)2], 6.16 (s, 2 H, CH2N+), 6.40 (s, 2 H, CH2N+), 6.47 [s,
1 H, CH(OCH2)2], 6.50 [s, 1 H, CH(OCH2)2], 7.19 (d, 3J = 7.1 Hz,
1 H, Ar-H), 7.58–7.64 (complex m, 2 H, Ar-H), 7.87 (s, 1 H, Ar-H),
3
8.10–8.21 (complex m, 4 H, Ar-H), 8.33 (d, J = 7.9 Hz, 1 H, Ar-
3
H), 8.41 (d, J = 7.9 Hz, 1 H, Ar-H), 8.72–8.78 (complex m, 3 H,
Ar-H), 9.04 (d, 3J = 5.9 Hz, 1 H, Ar-H).
13C NMR (100 MHz, DMSO-d6): d = 57.9 (CH2N+), 60.2 (CH2N+),
65.7 [4 C, CH(OCH2)2], 97.1 [CH(OCH2)2], 97.2 [CH(OCH2)2],
123.0 (CH), 126.1 (2 CH), 126.3 (CH), 126.8 (CH), 128.1 (CH),
128.6 (CH), 128.8 (CH), 129.0 (Cq), 129.8 (CH), 129.9 (Cq), 130.2
Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York

1554
A. Granzhan et al.
FEATURE ARTICLE
(CH), 132.4 (Cq), 133.2 (Cq), 146.5 (CH), 147.2 (CH), 124.3 (CH),
147.4 (CH), 151.9 (Cq), 152.1 (Cq).
Table 2 Crystallographic Data for Compound 3
Parameter
Value
Anal. Calcd for C28H28B2F8N2O4 (630.1): C, 53.37; H, 4.48;
N, 4.45. Found: C, 53.49; H, 4.55; N, 4.50.
Molecular formula
Temperature (K)
Wavelength (Å)
Space group
C24H16B2F8N2
159(2)
4a,14a-Diazoniaanthra[1,2-a]anthracene Bis(tetrafluoro-
borate) (3)
0.71073
A solution of the dibromide 6a (0.50 g, 0.81 mmol) in 48% aq HBr
(4.0 mL) was stirred under reflux for 3.5 h. After cooling to 80 °C,
a solution of NaBF4 (0.50 g, 4.54 mmol) in H2O (4 mL) was added,
while a yellow precipitate was formed. After cooling to 4 °C, the
precipitate was collected, washed with H2O (2 × 5 mL) and acetone
(2 × 5 mL) and dried in vacuo.
C2/c (No. 15)
a = 18.083(5) Å
b = 9.4536(18) Å
c = 12.1006(19) Å
b = 90.37(2)°
2068.5(7)
Unit cell dimensions
Yield: 0.22 g (54%); recrystallization from acidified (1 drop HBF4)
MeCN–H2O afforded well-shaped pale-yellow prisms, mp
>340 °C.
1H NMR (400 MHz, DMSO-d6): d = 8.20–8.27 (complex m, 2 H,
Volume (Å3)
3-H, 13-H), 8.36–8.42 (complex m, 2 H, 2-H, 12-H), 8.55 (d,
3
3J = 8.8 Hz, 1 H, 7-H), 8.64 (d, J = 8.8 Hz, 1 H, 8-H), 8.68–8.73
Z
4
(complex m, 2 H, 6-H, 9-H), 8.79 (d, 3J = 8.8 Hz, 1 H, 11-H), 8.83
(d, 3J = 8.8 Hz, 1 H, 1-H), 9.47 (s, 1 H, 10-H), 9.51 (d, 3J = 6.9 Hz,
Calculated density (g cm–3)
Absorption coefficient (mm–1)
F(000)
1.625
3
1 H, 4-H), 9.77 (d, J = 6.9 Hz, 1 H, 14-H), 10.46 (s, 1 H, 16-H),
0.145
10.60 (s, 1 H, 5-H), 11.30 (s, 1 H, 15-H).
13C NMR (100 MHz, DMSO-d6): d = 122.5 (Cq), 122.6 (Cq), 123.0
(CH, C-13), 123.6 (CH, C-3), 125.0 (CH, C-10), 125.7 (CH, C-16),
126.2 (Cq), 126.8 (CH, C-11), 128.0 (CH, C-1), 129.6 (CH, C-6),
130.6 (CH, C-9), 131.7 (Cq), 131.8 (CH, C-7), 133.1 (CH, C-13),
133.8 (CH, C-3), 134.8 (CH, C-4), 135.0 (CH, C-8), 136.0 (Cq),
136.2 (CH, C-14), 137.0 (Cq), 138.2 (Cq), 138.7 (Cq), 139.1 (2 CH,
C-15, C-16).
1024
Crystal size
0.60 × 0.28 × 0.14 mm
2.25 £ q £ 32.59
–26 £ h £ 26
–14 £ k £ 13
–18 £ l £ 17
14494/3519
0.0580
Measured q range
Limiting indices
15N NMR (HMBC, DMSO-d6): d = 204.9 (1 N, N-4a), 205.8 (1 N,
N-14a).
MS (ESI+): m/z (%) = 166 (5) [M]2+, 331 (100) [M – H]+, 419 (53)
[M + BF4]+, 925 (12) [2 M + 3 BF4]+.
Reflections collected/unique
Rint
Anal. Calcd for C24H16B2F8N2 (506.0): C, 56.97; H, 3.19; N, 5.54.
Found: C, 57.14; H, 3.10; N, 5.53.
Data/restrains/parameters
Goodness of fit on F2
R values [I2 ≥ 2s(I)]
R values (all data)
3519/0/164
X-Ray Crystal Structure Analysis of 3
The single crystal X-ray measurements were performed with a SIE-
MENS SMART CCD diffractometer at a temperature of about
–115 °C. Repeatedly measured reflections remained stable. No ab-
sorption correction was made. The structure was determined by di-
rect methods using program SHELXS-9726a and refined on F2
values using program SHELXL-97.26b
1.028
R1 = 0.0472, wR2 = 0.1069
R1 = 0.0876, wR2 = 0.1252
0.385 and –0.294 e Å–3
Final Fourier residuals
Since the molecules are statistically distributed about a crystallo-
graphic two-fold axis, the atoms labeled N4a and C14a (Figure 3)
were both refined as split atoms (0.5 C and 0.5 N). A refinement of
an ordered structure in the lower-symmetric space group Cc did not
significantly improve the R-values and lead to serious correlation
problems.
itate was collected, washed with H2O (2 × 10 mL) and acetone
(2 × 10 mL) and dried in vacuo, giving 1.53 g (95%) of a mixture of
3 (37%; 1H NMR-spectroscopically) and 7 (63%) as a yellow pow-
der.
The hydrogen atoms were geometrically positioned and con-
strained. The non-hydrogen atoms were refined with anisotropic
thermal parameters. Crystal data and structure refinement details
are given in Table 2; supplementary crystallographic data are avail-
able at request.27
Fractional crystallization from MeNO2 (3-fold) afforded almost
pure 3 (less soluble compound). The mother liquor, containing ca.
92% (1H NMR-spectroscopically) of 7, was evaporated and the res-
idue recrystallized from MeCN–H2O, giving pure 7 as brown mi-
crocrystalline solid.
13a,16a-Diazoniahexaphene Bis(tetrafluoroborate) (7)
Bis(tetrafluoroborate) 6b (2.00 g, 3.17 mmol) in polyphosphoric
acid (20 g) was heated under Ar atmosphere to 150 °C, and the re-
action mixture was stirred at this temperature for 24 h. After cooling
to about 100 °C, H2O (30 mL) was carefully added and the mixture
was stirred at this temperature for 30 min for hydrolysis of the PPA.
The mixture was cooled to r.t. and treated with a solution of NaBF4
(3.30 g, 30 mmol) in H2O (5 mL). After cooling to 4 °C, the precip-
Yield: 85 mg; mp >340 °C.
1H NMR (400 MHz, DMSO-d6): d = 8.09–8.11 (complex m,
3J = 9.5 Hz 2 H, 6-H, 12-H), 8.17 (dd, 3J = 7.3 Hz, 3J = 8.5 Hz, 1 H,
11-H), 8.23 (dd, 3J = 6.8 Hz, 1 H, 2-H), 8.37 (d, 3J = 9.4 Hz, 1 H, 7-
H), 8.43 (dd, 3J = 7.8 Hz, 3J = 8.3 Hz, 1 H, 3-H), 8.71 (d,
3J = 8.6 Hz, 2 H, 4-H, 10-H), 9.06 (s, 1 H, 5-H), 9.08 (s, 1 H, 8-H),
Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York

FEATURE ARTICLE
Diazoniapolycyclic Salts from 1,7-Dimethylnaphthalene
1555
9.44 (d, 3J = 6.8 Hz, 1 H, 1-H), 9.51 (s, 1 H, 9-H), 9.61 (d, 3J = 7.0
Hz, 1 H, 13-H), 9.97 (s, 1 H, 15-H), 10.63 (s, 1 H, 14-H), 11.10 (s,
1 H, 16-H).
13C NMR (100 MHz, DMSO-d6): d = 122.7 (CH, C-12), 123.8 (CH,
C-2), 124.2 (Cq), 124.3 (Cq), 124.5 (CH, C-5), 125.0 (CH, C-15),
125.4 (CH, C-9), 127.0 (CH, C-4 or C-10), 127.1 (CH, C-4 or C-
10), 128.2 (CH, C-8), 128.3 (CH, C-6), 128.6 (Cq), 131.3 (CH, C-
11), 133.6 (Cq), 134.7 (CH, C-13), 135.1 (CH, C-7), 135.2 (CH, C-
16), 135.5 (Cq), 135.9 (CH, C-3), 136.4 (CH, C-1), 136.9 (Cq),
137.7 (Cq), 140.9 (Cq), 141.6 (CH, C-14).
(10) Bailey, A. S.; Bryant, K. C.; Hancock, R. A.; Morrell, S. H.;
Smith, J. C. J. Inst. Petroleum 1947, 33, 503.
(11) (a) Horning, E. C.; Reisner, D. B. J. Am. Chem. Soc. 1949,
71, 1036. (b) Mogilaiah, K.; Vasudeva Reddy, N.; Randheer
Reddy, G. Synth. Commun. 2003, 33, 3109. (c) Mahmoodi,
N. O.; Jazayri, M. Synth. Commun. 2001, 31, 1467.
(12) Sepiol, J. Synthesis 1983, 559.
(13) Suld, G.; Stuart, A. P. J. Org. Chem. 1964, 29, 2939.
(14) (a) Wolinska-Mocydlarz, J.; Canonne, P.; Leitch, L. C.
Synthesis 1974, 566. (b) Terfort, A.; Görls, H.; Brunner, H.
Synthesis 1997, 79.
(15) Bradsher, C. K.; Parham, J. C. J. Org. Chem. 1963, 28, 83.
(16) (a) Granzhan, A.; Ihmels, H.; Mikhlina, K.; Deiseroth, H.-J.;
Mikus, H. Eur. J. Org. Chem. 2005, 4098. (b) Krapcho, A.
P.; Cadamuro, S. A. J. Heterocycl. Chem. 2004, 41, 291.
(17) (a) Bradsher, C. K. Chem. Rev. 1987, 87, 1277.
(b) Bradsher, C. K. In Comprehensive Heterocyclic
Chemistry; Katritzky, A. R.; Reeds, C. W., Eds.; Pergamon:
Oxford, 1984, Vol. 2, 525–579.
15N NMR (HMBC, DMSO-d6): d = 205.4 (1 N, N-16a), 206.0 (1 N,
N-13a).
MS (ESI+): m/z (%) = 331 (100) [M – H]+, 351 (29) [M + F]+, 419
(10) [M + BF4]+, 925 (6) [2 M + 3 BF4]+.
Anal. Calcd for C24H16B2F8N2 (506.0): C, 56.97; H, 3.19; N, 5.54.
Found: C, 56.71; H, 3.43; N, 5.57.
Photodegradation of Salts 3 and 7 in Solution
(18) (a) Ihmels, H.; Leusser, D.; Pfeiffer, M.; Stalke, D. J. Org.
Chem. 1999, 64, 5715. (b) Ihmels, H.; Mohrschladt, C. J.;
Schmitt, A.; Bressanini, M.; Leusser, D.; Stalke, D. Eur. J.
Org. Chem. 2002, 2624. (c) Maassarani, F.; Pfeffer, M.; Le
Borgne, G. Organometallics 1990, 9, 3003. (d) Sato, K.;
Arai, S.; Yamagishi, T.; Tanase, T. Acta Crystallogr., Sect.
C: Cryst. Struct. Commun. 2001, 57, 174.
Solutions of salts 3 and 7 in deionized, air-equilibrated water
(100 mM) were placed into quartz reduced-path spectrophotometric
cells (pathlength 2 mm; side area 3.33 cm2) and irradiated in a Ray-
onet photoreactor (lL = 350 nm, irradiance IL = 7.2 mW cm–2) for
1 h. UV/Vis absorption spectra were determined in 5-to-10-min in-
tervals.
(19) (a) Birks, J. B. Photophysics of Aromatic Molecules; Wiley-
Interscience: London, 1970. (b) Clar, E.; Wallenstein, H.;
Avenarius, R. Chem. Ber. 1929, 62, 950. (c) Clar, E. Chem.
Ber. 1940, 73, 81.
(20) Berlman, I. B. J. Phys. Chem. 1970, 74, 3085.
(21) (a) Harvey, R. G. Polycyclic Aromatic Hydrocarbons;
Wiley-VCH: New York, 1997. (b) Laarhoven, W. H.;
Cuppen, T. J.; Nivard, R. J. F. Tetrahedron 1970, 26, 4865.
(22) (a) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75,
991. (b) Valeur, B. Molecular Fluorescence: Principles and
Applications; Wiley-VCH: Weinheim, 2002.
Acknowledgment
This work was generously financed by the Deutsche Forschungsge-
meinschaft.
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Synthesis 2006, No. 9, 1549–1555 © Thieme Stuttgart · New York