A stable enol from a 6-substituted benzanthrone and its unexpected behaviour under acidic conditions

Article abstract of DOI:10.3762/bjoc.5.31

Treatment of benzanthrone (1) with biphenyl-2-yl lithium leads to the surprisingly stable enol 4, which is converted by dehydrogenation into the benzanthrone derivative 7. Under acidic conditions 4 isomerises to the spiro compound 11 and the bicyclo[4.3.1

Full text of DOI:10.3762/bjoc.5.31

A stable enol from a 6-substituted benzanthrone and
its unexpected behaviour under acidic conditions
Marc Debeaux1, Kai Brandhorst2, Peter G. Jones3, Henning Hopf2,
Jörg Grunenberg2, Wolfgang Kowalsky1 and Hans-Hermann Johannes*,1
Full Research Paper
Open Access
Address:
Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
1Labor für Elektrooptik am Institut für Hochfrequenztechnik,
Technische Universität Braunschweig, Bienroder Weg 94, 38106
Braunschweig, Germany, 2Institut für Organische Chemie,
Technische Universität Braunschweig, Hagenring 30, 38106
Braunschweig, Germany and 3Institut für Anorganische und
Analytische Chemie, Technische Universität Braunschweig,
Hagenring 30, 38106 Braunschweig, Germany
doi:10.3762/bjoc.5.31
Received: 29 April 2009
Accepted: 19 May 2009
Published: 16 June 2009
Associate Editor: J. Murphy
Email:
© 2009 Debeaux et al; licensee Beilstein-Institut.
License and terms: see end of document.
Hans-Hermann Johannes* - h2.johannes@ihf.tu-bs.de
* Corresponding author
Keywords:
consecutive reactions; intramolecular cyclization; molecular
modelling; spiro compounds; X-ray structural analysis
Abstract
Treatment of benzanthrone (1) with biphenyl-2-yl lithium leads to the surprisingly stable enol 4, which is converted by dehydrogen-
ation into the benzanthrone derivative 7. Under acidic conditions 4 isomerises to the spiro compound 11 and the
bicyclo[4.3.1]decane derivative 12. Furthermore, the formation of 7 and the hydrogenated compound 13 is observed. A mechanism
for the formation of the reaction products is proposed and supported by DFT calculations.
Introduction
Compounds for optoelectronic applications with electrolumin- The reaction of 1 with various organometallic reagents was
escent (e.g. organic light-emitting diodes, OLEDs) or light- studied by Allen in the 1970s [3]. It was shown that an attack of
harvesting properties (e.g. organic solar cells) are receiving phenylmagnesium chloride or phenyl sodium after 1,4-addition
more and more attention [1]. In this respect benzanthrone (1), leads to the 6-substituted benzanthrone derivative 3 (Scheme 1).
with its luminescent and photosensitizing properties, is an inter- On changing the solvent from ether-benzene to tetrahydrofuran
esting candidate for the construction of these systems. Recently, the ketone could also be isolated in high yields, but additionally
aminobenzanthrone derivatives have been shown to be efficient a labile enol was produced that was hard to separate. To this
emitters for OLED applications [2]. In these devices, the benz- compound, obviously an intermediate in the addition process,
anthrone moiety acts as an electron accepting group, whereas the authors assigned structure 2, a compound that under the
the diarylamine group functions as an electron donor.
reaction condition is dehydrogenated to 3.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Scheme 1: Behaviour of benzanthrone (1) towards phenylmagnesium chloride (a), phenyl lithium (b), and biphenyl-2-yl lithium (c).
Here, we present the first isolable enol derived from a benzan- throne was treated with phenyl lithium [3]. The yield of 4 was
throne and the unexpected behaviour of this adduct under acidic not improved by addition of a copper(I) salt in catalytic
conditions.
amounts [4]. This procedure should have favoured the ratio of a
1,4- to a 1,2-addition product [5].
Results and Discussion
Syntheses
The enol 4 is stable as a solid and also in deuterated dimethyl
Benzanthrone (1) was treated with biphenyl-2-yl lithium sulfoxide, since an NMR solution in this solvent was unchanged
(Scheme 1). After work-up and chromatography the surpris- after one week. In contrast, a solution of 4 in chloroform
ingly stable enol 4 was obtained in 56% yield. However, no showed quantitative conversion to the 6-substituted benzan-
formation of the tertiary alcohol 5 could be observed, a throne 7 after approximately one week; a process that was
compound type which is produced (derivative 6) when benzan- subsequently monitored by 1H NMR spectroscopy (Figure 1) in
Figure 1: 1H NMR spectra (200 MHz) of 4 in CDCl3 solution and time dependence.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Scheme 2: Proposed mechanism for the formation of 4 and its oxidation to 7.
CDCl3. This conversion is much slower when the CDCl3 is spectrometry (the “ortho-effect” see [6]). Next, the enol 4 was
filtered through an alumina plug before use. The reaction treated deliberately under acidic conditions by heating it with
constitutes a formal dehydrogenation of 4 (Scheme 2).
phosphoric acid in toluene under reflux. Silica gel was added to
the two-phase mixture in order to effect a better contact
As shown in Scheme 2, we propose that the formation of 4 and between the layers. The progress of the reaction was monitored
7 starts as a 1,4-addition process as discussed above via the by TLC, which indicated that, surprisingly, three different new
enolate 8 as an intermediate. From this, the enol 4 is generated compounds were produced besides 7 (21% yield). After work-
under the influence of the added acid. Further protonation up and chromatography, these new products were identified as
provides the oxonium ion 9 which is set up for a retro-[2+4]- 11, 12, and 13 (Scheme 3). The ketone 7 itself is stable under
cycloaddition (see transition state 10) to lose hydrogen and these reaction conditions.
finally become deprotonated to yield the isolated 7. Since at this
stage of our study we were not interested in mechanistic invest- Spiro compound 11 (11% yield) was characterised by NMR
igations we did not look for the production of hydrogen. spectroscopy, mass spectrometry and single crystal X-ray crys-
Considering the small amount of substrate we were working tallography (see below). The 1H NMR spectrum (600 MHz) of
with (0.7 mM concn of 4) and the slow process of the conver- 11 shows two aliphatic triplets at δ = 2.16 and 3.42 ppm
sion, it is not surprising that we could not see any gas forma- (J = 6.2 Hz) which are assigned to the four methylene protons.
tion (hydrogen bubbles). However, what makes this rationalisa- In the 13C NMR spectrum (151 MHz) the corresponding carbon
tion attractive is the production of both an aromatic system as atoms cause signals at 28.4 and 37.3 ppm, respectively. The
well as a carbonyl group, so the process is thermodynamically spiro carbon atom is represented by a singlet at 53.4 ppm. All
favourable. Furthermore, the formation of quinomethides from other spectroscopic data correspond to expectations and are
ortho-substituted phenols is a well known phenomenon in mass recorded in the Experimental section.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Scheme 3: Conversion of the enol 4 under acidic conditions and reaction products.
Compound 12 was characterised by NMR spectroscopy and The formation of these three new compounds can be explained
mass spectrometry. The proton signals at δ = 2.61 and 2.84 ppm as follows. For the production of 11 and 12 we propose the
(400 MHz) with a geminal coupling constant of 13.5 Hz corres- mechanism summarised in Scheme 4 [8].
pond to the protons of the methylene bridge. The bridgehead
protons arise as a multiplet at 4.70–4.76 ppm. NMR data of the Both 11 and 12 have the same molecular mass as the starting
aliphatic protons correlate well with the data for 1,6-dihydro- material 4, so the processes leading to these two products are
1,6-methanobenzo[d]cyclooctene, a compound with a similar isomerisations. The protonation that initiates the rearrange-
carbon framework described by Banciu and co-workers [7].
ments can take place at C-4 or C-5 of the starting material 4. In
the former case the secondary cation 14 results, which by
Compound 13 was characterised by NMR spectroscopy, mass proton loss is converted into hydrocarbon 15; in other words, 4
spectrometry and by single crystal X-ray crystallography (see has undergone an acid-catalyzed allylic rearrangement.
below). The mass spectrum of compound 13 shows a signal Renewed protonation leads to the tertiary cation 16, which by
with m/z = 386, which exceeds the molar mass of the starting an internal Friedel-Crafts alkylation provides the spiro
material 4 by 2 Da. The ethylene moiety is represented in two compound 11. Alternatively, protonation of 4 at C-5 generates
groups of multiplets in the 1H NMR spectrum (400 MHz; the benzylic cation 17, which by intramolecular electrophilic
δ = 1.68–1.77 and 2.79–2.84 ppm).
attack leads to the bicyclo[4.3.1]decane derivative 12.
Scheme 4: Proposed mechanism for the formation of spiro compound 11 and bicyclo[4.3.1]decane derivative 12.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Finally, the formation of 13 is a formal hydrogenation of the
starting material 4. In the absence of a catalytically active layer
that promotes a hydrogen-transfer reduction [9,10], we propose
an acid-catalysed hydride transfer of the type reported by
Carlson and Hill [11]. Thereby, a carbenium ion such as 14, 16
or 17 (only the case of 16 is discussed in the following) can
abstract hydride from another molecule that itself forms a stable
cation (Scheme 5).
Table 1: Gas phase electronic energies/enthalpies for intermediates
generated along the proposed reaction pathway. All values are given
in kcal mol−1.
ΔE0
ΔH298
ΔG298
4 + H+ → 9
−193.95
204.64
−193.82
206.37
−193.96
196.59
9 → 7 + H2 + H+
4 → 7 + H2
10.69
12.56
2.62
4 + H+ → 14
14 → 15 + H+
15 + H+ → 16
16 → 11 + H+
−194.38
194.29
−223.59
206.49
−194.52
194.45
−223.35
205.75
−194.32
194.17
−224.97
208.77
4 → 11
−17.19
−17.68
−16.34
4 + H+ → 17
−212.87
206.32
−212.63
205.19
−214.39
209.39
17 → 12 + H+
Scheme 5: Proposed mechanism for the formation of 13.
4 → 12
−6.55
−7.45
−5.00
4 + H+ → 14
14 → 15 + H+
15 + H+ → 16
16 + H− → 13
H2 → H+ + H−
4 → 18 + H−
18 → 7 + H+
−194.38
194.29
−223.59
−207.23
407.16
187.61
230.24
−194.52
194.45
−223.35
−208.68
406.57
188.95
230.17
−194.32
194.17
−224.97
−200.75
408.09
180.77
229.94
In order to make the above mechanistic speculations more than
simple “electron pushing”, we decided to apply the following
computational methods.
Reaction mechanisms by computational
methods
The gas phase global minima of the relevant molecules 4, 7 and
9–18 were obtained by first applying an extended conforma-
tional analysis using the OPLS2005 force field [12] together
with a Monte Carlo torsional sampling as implemented in the
4 + H2 → 13
−23.75
−25.54
−17.78
Macromodel 9.5 program [13]. Each lowest energy conforma- 193.95 kcal mol−1. This may trigger a H2 abstraction in a
tion of 4, 7 and 9–18, respectively, was then optimised by concerted manner, followed by a proton abstraction, which
applying density functional theory. The M05-2X hybrid func- demands 204.64 kcal mol−1. The net transformation 4 → 7 + H2
tional [14] was employed, and all atoms were described by a is slightly endothermal (10.69 kcal mol−1), thus the driving
standard triple zeta all electron basis set augmented with one set force of the ketone formation is the generation of dihydrogen.
of polarization functions (6-311G(d,p)). After the relevant
stationary points were localised on the energy surface, they The protonation of 4 at C-4 results in the secondary ion 14
were further characterised as minima states by normal mode which releases 194.38 kcal mol−1. The proton loss of 14 to form
analysis based on the analytical energy second derivatives. 15 costs 194.29 kcal mol−1. Further protonation of 15
Enthalpic and entropic contributions were estimated from the (−223.59 kcal mol−1) generates the cation 16, which can easily
partition functions calculated at room temperature (298 K) undergo an internal electrophilic substitution to form the spiro
under a pressure of 1 atm using Boltzmann thermostatistics and compound 11 (206.49 kcal mol−1). This results in an overall
the rigid rotor harmonic oscillator approximation as imple- exothermicity of 17.19 kcal mol−1 for the reaction 4 → 11.
mented in the Gaussian03 set of programs [15]. Table 1
summarises the reaction energies/enthalpies of the different In order to explain the formation of the bicyclo[4.3.1]decane
reaction steps. Although all calculations were carried out in the derivative 12 the enol 4 is protonated first at C-5 which releases
gas phase, it can be assumed that solvation effects will not 212.87 kcal mol−1. The benzyl cation thus generated can
counterbalance such high energetic differences.
undergo a similar electrophilic substitution to produce the final
product 12 at an effort of 206.32 kcal mol−1, resulting in an
The proposed reaction pathway from 4 to 7 proceeds via a overall exothermicity of −6.55 kcal mol−1 for the reaction 4 →
protonation of the OH group to form 9, releasing 12.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Scheme 6: Proposed mechanism for the formation of 18 as a hydride source and further conversion to 7.
The formation of 13 can be explained by addition of a hydride
species. Although the reaction takes place under acidic condi-
tions, the reaction of 4 to 18 for example (Scheme 6) can
deliver H− at a cost of 187.61 kcal mol−1 while the addition of a
hydride to 16 releases 207.23 kcal mol−1. The cation 18 can
then undergo a proton abstraction to form the ketone 7
(230.24 kcal mol−1). The reaction 4 → 7 + H2 and 4 + H2 → 13
can thus be seen as essentially coupled and in sum exothermic
(−13.06 kcal mol−1).
X-Ray structural analyses
Figure 3: Packing diagram of compound 7 viewed parallel to b;
hydrogen bonds C-H···O are indicated by dashed lines.
The molecule of compound 7 is shown in Figure 2. Bond
lengths and angles may be regarded as normal; the bond length
C10-O of 1.223(2) Å clearly indicates a double bond. The main
ring system C1-C17 is planar (rmsd 0.040 Å), whereby the O The main ring system (including the oxygen atom, but
atom lies 0.27 Å out of the plane and the ring C18-23 subtends excluding C5 and C6) is reasonably planar, with a rmsd of
an interplanar angle of 67.5°. The packing is mainly character- 0.074 Å; the rings C18-23 and C19-24 are essentially coplanar
ised by the weak C-H···O interactions from H12, H27 and H28, (interplanar angle 3.9°). Despite the presence of the hydroxyl
each with H···O 2.60 Å, forming via inversion and z translation group, there are no classical hydrogen bonds; instead, the OH
operators a chain of molecules parallel to c (Figure 3).
hydrogen is directed towards the ring centroid of C18-23
(H···centroid 2.74 Å, angle 163°). The packing involves two
Figure 2: Ellipsoid representation (50% level) of compound 7 in the
crystal.
The molecule of compound 11 is shown in Figure 4. The bond
length C10-O1 of 1.375(1) Å is consistent with a single bond,
and the hydroxy hydrogen atom was located and freely refined.
Figure 4: Ellipsoid representation (50% level) of compound 11 in the
crystal.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
short H···π contacts, H22···centroid (C1-4,9,17) 2.56 Å and subtends an angle of 88.4(1)° with the plane so defined; the
H28···centroid (C18-23) 2.74 Å, both via the glide operator, rings C18-23 and C24-29 subtend an angle of 64.0(1)°. The
resulting in chains of molecules parallel to c (Figure 5).
extended packing (Figure 7) involves the hydrogen bonds
H2···O1 2.61 Å and H29···π(C18-23) 2.55 Å; the overall effect
is to form strongly corrugated layers perpendicular to the z axis.
Figure 5: Packing diagram of compound 11 viewed perpendicular to
the bc plane; hydrogen bonds C-H···π are indicated by dashed lines.
Compound 13 crystallizes with one molecule of deuterated
DMSO; the formula unit is shown in Figure 6. The DMSO is
well-ordered and is involved in a classical hydrogen bond
O1-H01···O2 from the hydroxyl group, with H···O 0.87(2),
O···O 2.655(1) Å, O-H···O 174(2)°. The DMSO methyl
deuterium D99A forms a short H···π contact of 2.54 Å to the
centre of the ring C18-23. The bond length C10-O1 of 1.369(1)
Å is consistent with a single bond, and the hydroxy hydrogen
was located and freely refined. The ring system C1-C17, less
C6, is planar to within an rmsd. of 0.055 Å, and the ring C18-23
Figure 7: Packing diagram of compound 13 viewed parallel to c;
DMSO molecules (including their hydrogen bonds) are represented by
thick bonds. Hydrogen bonds C-H···O and C-H···π are indicated by thin
dashed lines. The interactions D99A···π (see text) are omitted for
clarity, but their positions are implicit (on the opposite side of the ring
from the C-H···π interaction already drawn).
Experimental
General
Melting points: Stuart Melting Point SMP3 apparatus, uncorr. –
Elemental analyses: Vario EL Elemental Analysis Instrument
(Elementar Co.). – IR: Bruker Tensor 27 spectrometer with a
Diamond ATR sampling element. – UV/Vis: Varian Cary 100
Bio as solutions in spectroscopic grade solvents. – NMR:
Bruker DPX-400 and AV2-600 spectrometers; 1H chemical
shifts were recorded relative to tetramethylsilane (TMS) as
internal standard and 13C measurements are referred to the
corresponding NMR solvent signal. All J values are in Hertz
and are rounded to the nearest 0.1 Hz. – MS: Thermofinnigan
MAT95. – TLC: SiO2 plates (Polygram SIL G/UV 254). – All
compounds were purified by flash chromatography on Kies-
elgel 60 (Fluka). All reagents, unless otherwise specified, were
obtained from Aldrich, Acros and Fluka and used as received.
All solvents were purified before use. All reactions were
performed under nitrogen atmosphere. Dry solvents stored over
molecular sieve were purchased from Fluka.
Figure 6: Ellipsoid representation (50% level) of compound 13 (d6-
DMSO solvate) in the crystal. Hydrogen bonds (see text) are not drawn
explicitly.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
6-(Biphenyl-2-yl)-6H-benzo[de]anthracen-7-ol (4)
1437 (m), 1404 (m), 1286 (w), 1239 (w), 1208 (m), 1184 (w),
To a solution of 2-bromobiphenyl (2.00 g, 8.58 mmol) in dry 1160 (m), 1096 (w), 1077 (w), 964 (m), 925 (m), 894 (w), 808
THF (20 mL) a 1.6 M solution of n-butyl lithium in n-hexane (w), 752 (vs), 734 (s), 679 (m), 572 (m), 553 (m), 537
(6.4 mL, 10.3 mmol) was added drop wise at −80 °C. After 1 h (m) cm−1. UV (acetonitrile): λmax (log ε) = 196 (4.70), 210
of stirring at the same temperature, the solution was added to a (4.77), 260 (4.70), 304 (4.08), 345 (3.17), 362 (3.18) nm.
suspension of benzanthrone (1) (1.98 g, 8.58 mmol) in dry THF 1H NMR (600 MHz, CDCl3): δ = 2.16 (t, J = 6.2 Hz, 2 H,
(20 mL). The brownish mixture was stirred for 2.5 h under CH2), 3.42 (t, J = 6.2 Hz, 2 H, CH2), 4.59 (s, 1 H, OH),
reflux before allowing to cool to room temperature. A further 7.27–7.32 (m, 4 H), 7.45–7.75 (m, 5 H), 7.62 (ddd, J = 7.7, 6.9,
16 h of stirring was followed by quenching with a saturated 1.4 Hz, 1 H), 7.93 (ddd, J = 7.7, 0.9, 0.9 Hz, 2 H), 8.05 (dd,
aqueous solution of ammonium chloride (200 mL). After J = 8.3, 1.0 Hz, 1 H), 8.64 (dd, J = 8.2, 1.5 Hz, 1 H), 8.68 (d,
extraction with CHCl3 (3 × 100 mL) the combined organic J = 8.4 Hz, 1 H) ppm. 13C NMR (151 MHz, CDCl3): δ = 28.4
phases were dried (MgSO4) and the solvents were evaporated. (t), 37.3 (t), 53.4 (s), 112.5 (s), 121.0 (d), 121.3 (d), 122.4 (d),
The brown crude product was purified by flash chromato- 122.9 (d), 123.5 (d), 125.0 (d), 125.9 (s), 126.4 (d), 126.7 (d),
graphy (CH2Cl2/n-hexane, 1:1, v/v; Rf = 0.66) to give 1.89 g 126.9 (d), 127.0 (s), 128.3 (s), 128.4 (s), 130.0 (s), 130.8 (s),
(56%) of the enol 4 as a light-yellow solid with mp 235 °C. IR: 133.9 (s), 138.9 (s), 146.4 (s), 150.4 (s) ppm. m/z (%) = 384
= 3555 (w), 3063 (w), 3021 (w), 1593 (w), 1493 (w), 1473 (100) [M]+, 307 (63). HRMS: calcd. for C29H20O 384.151415
(w), 1457 (w), 1410 (w), 1331 (w), 1270 (w), 1202 (m), 1157 [M]+; found 384.15170. C29H20O (384.47): calcd. C 90.60,
(w), 1096 (w), 1042 (w), 1007 (w), 982 (w), 922 (w), 896 (w), H 5.24; found C 90.17, H 5.15. Second Fraction: 57 mg (11%)
836 (w), 821 (m), 742 (vs), 705 (s) cm−1. UV (acetonitrile): of 13 as a colourless solid with mp 210 °C (single crystals were
λmax (log ε) = 204 (4.82), 229 (4.66), 256 (4.39), 268 (4.44), grown from d6-DMSO). IR:
= 3554 (w), 3061 (w), 3021 (w),
286 (4.31), 319 (3.92), 332 (4.05), 347 (3.97), 378 (3.33) nm. 2939 (w), 2921 (w), 2856 (w), 1599 (w), 1474 (w), 1460 (w),
1H NMR (400 MHz, d6−DMSO): δ = 5.56 (br. d, J = 4.7 Hz, 1440 (w), 1414 (w), 1322 (w), 1267 (w), 1208 (m), 1162 (w),
1 H), 5.95 (dd, J = 9.6, 4.8 Hz, 1 H), 6.60 (dd, J = 9.7, 1.6 Hz, 1009 (w), 925 (w), 754 (vs), 738 (s), 706 (s), 663 (w), 616 (w),
1 H), 6.75 (br. d, J = 7.9 Hz, 1 H), 7.05 (ddd, J = 7.9, 6.8, 597 (w), 545 (w) cm−1. UV (acetonitrile): λmax (log ε) = 195
2.1 Hz, 1 H), 7.13–7.20 (m, 2 H), 7.31 (br. d, J = 6.9 Hz, 1 H), (4.83), 259 (4.65), 307 (3.99), 347 (3.11), 363 (3.11) nm.
7.40–7.47 (m, 2 H), 7.56 (br. dd, J = 7.5, 7.5 Hz, 2 H), 1H NMR (400 MHz, d6-DMSO): δ = 1.68–1.77 (m, 2 H),
7.60–7.72 (m, 4 H), 8.23–8.26 (m, 1 H), 8.59 (br. d, J = 8.7 Hz, 2.79–2.84 (m, 2 H), 5.27–5.32 (m, 1 H), 6.47 (d, J = 7.7 Hz,
1 H), 8.80 (dd, J = 7.7, 1.9 Hz, 1 H), 9.39 ppm (s, 1 H, OH). 1 H), 6.97–7.03 (m, 1 H), 7.15–7.20 (m, 2 H), 7.38 (dd, J = 7.0,
13C NMR (101 MHz, d6−DMSO): δ = 117.3 (s), 122.0 (d), 0.9 Hz, 1 H), 7.41–7.47 (m, 2 H), 7.55 (dd, J = 7.4, 7.4 Hz,
122.3 (d), 123.2 (d), 124.1 (d), 124.5 (d), 124.7 (d), 124.9 (s), 2 H), 7.61–7.72 (m, 4 H), 8.23–8.30 (m, 1 H), 8.66 (d,
125.7 (d), 126.0 (s), 126.3 (d), 126.4 (d), 127.0 (d), 127.3 (d), J = 7.7 Hz, 1 H), 8.84 (dd, J = 7.4, 2.2 Hz, 1 H), 9.27 (s, 1 H,
127.7 (d), 127.9 (s), 128.0 (d), 128.2 (d), 129.3 (d), 129.4 (d), OH) ppm. 13C NMR (101 MHz, d6-DMSO): δ = 25.0 (t), 27.2
129.6 (s), 129.8 (s), 130.9 (d), 139.9 (s), 141.6 (s), 143.9 (s), (t), 34.7 (d), 117.9 (s), 121.0 (d), 122.2 (d), 123.2 (d), 123.4 (d),
147.7 ppm (s) [16]. MS (EI, 70 eV): m/z (%) = 384 (61) [M]+, 125.7 (d), 125.7 (s), 126.2 (d), 126.3 (d), 126.3 (d), 126.3 (s),
305 (100), 231 (23). C29H20O (384.47): calcd. C 90.60, H 5.24; 126.6 (d), 127.0 (d), 127.7 (d), 128.3 (d), 129.2 (d), 130.0 (s),
found C 90.32, H 5.19.
130.1 (s), 130.2 (d), 134.3 (s), 141.2 (s), 141.8 (s), 142.7 (s),
145.9 (s) ppm. MS (EI, 70 eV): m/z (%) = 386 (56) [M]+, 231
(100), 232 (68). C29H22O (386.48): calcd. C 90.12, H 5.74;
found C 90.27, H 5.81. Third Fraction: 47 mg (9%) of 12 as a
6-(Biphenyl-2-yl)-7H-benzo[de]anthracen-7-one (7),
4,5-Dihydrospiro[benzo[de]anthracene-6,9′-fluoren]-
7-ol (11), Bicyclo[4.3.1]decane derivative 12, and
6-(Biphenyl-2-yl)-5,6-dihydro-4H-
colourless solid with mp 221 °C. IR:
= 3563 (m), 3055 (w),
3022 (w), 2925 (w), 2863 (w), 1597 (w), 1492 (w), 1441 (w),
1422 (w), 1377 (w), 1324 (w), 1265 (w), 1226 (m), 1195 (w),
benzo[de]anthracen-7-ol (13)
The enol 4 (500 mg, 1.30 mmol) was dissolved in warm toluene 1160 (w), 974 (w), 961 (w), 946 (w), 839 (w), 764 (m), 746
(20 mL). Phosphoric acid (0.5 mL) and silica gel (1.0 g) were (vs), 654 (w), 618 (w), 598 (m), 559 (m) cm−1. UV (acetoni-
added and the mixture was stirred vigorously under reflux for trile): λmax (log ε) = 215 (4.76), 259 (4.67), 316 (4.04), 349
1 d. The solvent was removed and the crude product was frac- (3.17), 366 (3.17) nm. 1H NMR (400 MHz, CDCl3): δ = 2.61
tioned by flash chromatography (CH2Cl2/n-hexane, 1:1, v/v; (ddd, J = 13.5, 2.8, 1.2 Hz, 1 H), 2.84 (ddd, J = 13.5, 7.0,
Rf = 0.73, 0.62, 0.51, 0.36). First fraction: 57 mg (11%) of 11 4.1 Hz, 1 H), 4.70–4.76 (m, 2 H), 6.05 (s, 1 H, OH), 7.03–7.11
as a colourless microcrystalline solid with mp 228 °C (single (m, 2 H), 7.33–7.38 (m, 2 H), 7.39–7.47 (m, 3 H), 7.50–7.58
crystals were grown from CDCl3). IR:
= 3473 (m), 3060 (w), (m, 2 H), 7.60 (d, J = 6.9 Hz, 1 H), 7.63–7.66 (m, 1 H),
3033 (w), 2924 (w), 2892 (w), 2849 (w), 1592 (m), 1493 (w), 7.79–7.76 (m, 1 H), 8.17–8.20 (m, 1 H), 8.37 (dd, J = 8.4,
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
0.8 Hz, 1 H), 8.50–8.53 (m, 1 H) ppm. 13C NMR (101 MHz,
CDCl3): δ = 31.3 (t), 41.3 (d), 46.2 (d), 114.8 (s), 120.7 (d),
121.9 (d), 122.6 (d), 123.9 (d), 124.3 (d), 126.0 (s), 126.2 (d),
126.3 (s), 126.4 (d), 126.6 (d), 127.1 (d), 127.8 (d), 127.9 (d),
128.4 (s), 128.5 (d), 130.5 (s), 131.6 (d), 131.8 (d), 134.1 (d),
136.1 (s), 138.7 (s), 140.9 (s), 141.1 (s), 144.3 (s), 147.6 (s)
ppm. MS (EI, 70 eV): m/z (%) = 384 (100) [M]+, 231 (45).
HRMS: calcd. for C29H20O 384.15142 [M]+; found 384.15113.
C29H20O (384.47): calcd. C 90.60, H 5.24; found C 90.42,
H 5.32. Fourth Fraction: 105 mg (21%) of 7 as a yellow solid
with mp 197 °C (single crystals were grown from CH2Cl2/n-
Table 2: Details of X-ray structure analyses.
Compound
7
11
13 × (CD3)2SO
Formula
Mr
C29H18O
382.43
C29H20O
384.45
C31H22D6O2S
476.66
Habit
yellow
tablet
colourless
prism
colourless
prism
Crystal
0.2 × 0.05 × 0.5 × 0.22 × 0.44 × 0.36 ×
size/mm
0.02
0.18
0.2
Radiation
λ/ Å
Cu Kα
1.54184
Mo Kα
0.71073
Mo Kα
0.71073
orthorhombic
Pccn
Crystal system monoclinic monoclinic
hexane, 1:1, v/v). IR:
= 3056 (w), 3015 (w), 1645 (s), 1597
Space group
P21/c
P21/c
(m), 1558 (m), 1478 (m), 1463 (m), 1372 (w), 1349 (m), 1294
(m), 1264 (m), 1216 (w), 1173 (w), 1144 (w), 1072 (w), 1026
(w), 1007 (w), 939 (m), 919 (w), 898 (w), 846 (m), 828 (m),
780 (w), 750 (vs), 702 (s), 667 (m), 609 (w), 588 (m), 564 (w),
538 (m) cm−1. UV (acetonitrile): λmax (log ε) = 205 (4.86), 232
(4.67), 256 (4.51), 362 (3.92), 385 (3.95) nm. 1H NMR
(400 MHz, CDCl3): δ = 6.90–6.97 (m, 3 H), 7.11–7.14 (m,
2 H), 7.17–7.23 (m, 2 H), 7.36 (ddd, J = 7.4, 7,4, 1.6 Hz,1 H),
7.39–7.44 (m, 2 H), 7.47 (dd, J = 7.7, 1.6 Hz, 1 H), 7.58 (dd,
J = 7.9, 7.5 Hz, 1 H), 7.62 (ddd, J = 7.5, 7.5, 1.5 Hz, 1 H), 7.84
(dd, J = 7.9, 0.8 Hz, 1 H), 7.86 (d, J = 8.4 Hz, 1 H), 8.22 (br. d,
J = 8.0 Hz, 1 H), 8.23 (dd, J = 7.9, 1.5 Hz, 1 H), 8.39 (dd,
J = 7.1, 0.8 Hz, 1 H) ppm. 13C NMR (101 MHz, CDCl3):
δ = 122.6 (d), 124.2 (d), 126.2 (d), 126.4 (d), 126.5 (s), 127.3
(d), 127.4 (d), 127.7 (d), 128.1 (d), 128.1 (d), 128.5 (s), 128.9
(d), 129.5 (d), 130.1 (d), 130.1 (d), 131.6 (d), 132.1 (s), 132.2
(s), 132.9 (d), 133.3 (d), 135.5 (s), 139.5 (s), 141.5 (s), 142.4
(s), 146.8 (s), 184.2 (s) ppm [16]. MS (EI, 70 eV): m/z
(%) = 382 (31) [M]+, 305 (100). C29H18O (382.45): calcd.
C 91.07, H 4.74; found C 91.28, 4.74.
Cell constants:
a/Å
12.1176(4) 12.4948(8)
18.8136(6) 13.8777(9)
13.6065(4)
b/Å
19.9929(6)
c/Å
9.6914(4)
90
12.1737(8)
90
17.4749(6)
α/°
90
90
β/°
104.113(4) 115.461(4)
γ/°
90
1914.94
4
90
1905.9
4
90
V/Å3
4753.8
8
Z
Dx/Mg m−3
μ/mm−1
F(000)
T/°C
1.327
0.61
800
1.340
0.08
808
1.332
0.16
1968
−90
−170
142
−140
61
2θmax
Completeness
61
97% to
135°
99.8% to
60°
99.1% to 60°
No. of
reflections:
measured
independent
Rint
21722
3534
0.039
271
29136
5804
0.045
275
77542
7094
0.035
313
Parameters
wR(F2, all refl.)
R(F, >4σ(F))
S
0.107
0.041
1.02
0.128
0.044
1.03
0.094
0.037
0.92
X-Ray structure determinations
Numerical details are presented in Table 2. Data collection:
Crystals were mounted in inert oil on glass fibres and trans-
ferred to the cold gas stream of the diffractometer (Oxford
Diffraction Nova O for 7 and Bruker SMART 1000 CCDC for
11 and 13). Crystals of compound 13 shattered at lower temper-
atures and were therefore measured at −90 °C. For 7 and 13, an
absorption correction based on multiple scans was performed.
Structure refinement: The structures were refined anisotropic-
ally against F2 using the program SHELXL-97 [17]. The
hydroxy hydrogens of 11 and 13 were refined freely; other H
atoms were included using a riding model.
max. Δρ/e Å−3
0.19
0.48
0.29
Supporting Information
Supporting Information features copies of 1H and
13C NMR spectra of compounds 4, 7, 11–13.
Supporting Information File 1
NMR spectra of compounds 4, 7, 11–13.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-5-31-S1.pdf]
Complete crystallographic data (excluding structure factors)
have been deposited at the Cambridge Crystallographic Data
Centre under the numbers CCDC 705268 (7), 705269 (11) and
716351 (13).
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Beilstein Journal of Organic Chemistry 2009, 5, No. 31.
Acknowledgments
We thank the Deutsches Zentrum für Luft und Raumfahrt e.V.
(DLR) and the Bundesministerium für Bildung und Forschung
(BMBF 01 BD 0687) for financial support.
References
1. Forrest, S. R.; Thompson, M. E. Chem. Rev. 2007, 107, 923–925.
doi:10.1021/cr0501590
2. Yu, M.-X.; Chang, L.-C.; Lin, C.-H.; Duan, J.-P.; Wu, F.-I.; Chen, I.-C.;
Cheng, C.-H. Adv. Funct. Mater. 2007, 17, 369–378.
doi:10.1002/adfm.200600730
3. Allen, C. F. H. Can. J. Chem. 1973, 51, 382–387.
4. The analogous procedure for the preparation of 4 (Experimental
section) involved the additional use of 5 mol% CuCl (42 mg, 430 µmol).
5. Rossiter, B. E.; Swingle, N. M. Chem. Rev. 1992, 92, 771–806.
doi:10.1021/cr00013a002
6. Johnstone, R. A. W. Mass Spectrometry for Organic Chemists;
Cambridge University Press, 1972; pp 95 ff.
7. Banciu, M. D.; Olteanu, E.; Drăghici, C.; Petride, A.; Dănilă, M.
J. Anal. Appl. Pyrolysis 1996, 37, 151–160.
doi:10.1016/0165-2370(96)00940-0
8. We thank a referee for suggesting this approach.
9. Brieger, G.; Nestrick, T. J. Chem. Rev. 1974, 74, 567–580.
doi:10.1021/cr60291a003
10.Johnstone, R. A. W.; Wilby, A. H.; Entwistle, I. D.
Chem. Rev. 1985, 85, 129–170. doi:10.1021/cr00066a003
11.Carlson, R. M.; Hill, R. K. J. Org. Chem. 1969, 34, 4178–4180.
doi:10.1021/jo01264a099
12.Jorgensen, W. L.; Tirado-Rives, J.
Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 6665–6670.
doi:10.1073/pnas.0408037102
13.Schrödinger, MacroModel version 9.5; LLC: New York, NY, 2007.
14.Zhao, Y.; Truhlar, D. G. Acc. Chem. Res. 2008, 41, 157–167.
doi:10.1021/ar700111a
15.Gaussian 03, Revision E.01; Gaussian, Inc.: Wallingford, CT, 2004.
16.One signal assigning a quaternary carbon atom is hidden in the
spectrum.
17.Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
doi:10.1107/S0108767307043930
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