Synthesis and Crystal Structure of Dimorphic Dibenzo[cde,opq]rubicene

Article abstract of DOI:10.1002/chem.201902915

Dibenzo[cde,opq]rubicene has been synthesized by an eight-step reaction sequence including an iron-mediated [2+2+1] cycloaddition and a flash vacuum pyrolysis as key steps. Two crystal modifications of the S-shaped, planar polycyclic aromatic hydrocarbon have been obtained and characterized by X-ray diffractometry.

Full text of DOI:10.1002/chem.201902915

A Journal of
Accepted Article
Title: Synthesis and Crystal Structure of Dimorphic
Dibenzo[cde,opq]rubicene
Authors: Joghee R. Suresh, Glenn Whitener, Gabriele Theumer, Dirk
J. Bröcher, Ingmar Bauer, Werner Massa, and Hans-Joachim
Knölker
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of the final Version of Record (VoR). This work is currently citable by
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To be cited as: Chem. Eur. J. 10.1002/chem.201902915
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COMMUNICATION
Synthesis and Crystal Structure of Dimorphic
Dibenzo[cde,opq]rubicene**
[
a]
[a]
[a]
[a]
Joghee R. Suresh, Glenn Whitener, Gabriele Theumer, Dirk J. Bröcher, Ingmar
[
a]
[b]
[a]
Bauer, Werner Massa, Hans-Joachim Knölker*
Abstract: Dibenzo[cde,opq]rubicene has been synthesized by an
eight-step reaction sequence including an iron-mediated [2+2+1]
cycloaddition and a flash vacuum pyrolysis as key steps. Two crystal
already become available by targeted organic synthesis.[6]
Yamamoto and coworkers described a previous synthesis of 1 by
flash vacuum pyrolysis of 7,14-diethynylacenaphtho[1,2-
modifications of the S-shaped planar polycyclic aromatic hydrocarbon
have been obtained and characterized by X-ray diffractometry.
k]fluoranthene
or
k]fluoranthene.[ They also investigated the redox properties of 1.
However, no spectroscopic details, in particular no 1H and 13
7,14-bis(1-chlorovinyl)acenaphtho[1,2-
7]
C
NMR data, have been provided. In order to get a reliable access
to this compound for further analytical investigations, we have
devised a new synthetic sequence.
Introduction
Polycyclic aromatic hydrocarbons (PAHs) consisting only of fused
aromatic rings without heteroatoms and substituents are an
intriguing class of organic compounds with unique properties.
They are formed by incomplete combustion of carbon-containing
fuels and other carbon-based compounds.[1] Thus, PAHs
represent one of the most abundant and persistent organic
pollutants which cause severe health concerns for humans, in
particular cancer.[1] Their interesting electronic and optoelectronic
properties have prompted several studies aiming for applications
in electronic devices.[2] Moreover, PAHs are considered to be
abundant in interstellar space and components of interstellar
dust.[3] Their contribution to the diffuse interstellar bands (DIBs)
has been widely discussed.[4] Dibenzo[cde,opq]rubicene (1)
Figure 1. Structures of dibenzo[cde,opq]rubicene (1) and C70 fullerene (2).
(
Figure 1) is a prominent representative of uncurved PAHs having
Results and Discussion
an S-shaped structure with C2h symmetry. In spite of the planar
structure of molecule 1, it constitutes in bent form a subunit of the
fullerene C70 (2) but not of C60. As both, C60 and C70 fullerenes,
have been identified in a planetary nebula, we assumed that 1
may also be present in interstellar space.[5] Therefore, we
performed extensive spectroscopic studies of 1 and compared the
data with those of interstellar spectra.[4d] Even though we did not
find coincidences between the spectral properties of 1 and several
interstellar phenomena, the presence in space cannot be
completely ruled out. Several bowl-shaped fragments of C70 have
The present approach to dibenzo[cde,opq]rubicene (1) is inspired
by our synthesis of corannulene (3).[ Since corannulene (3) can
be obtained by double cyclization of the bis(ethynyl)fluoranthene
8]
5
under the conditions of flash vacuum pyrolysis,
dibenzo[cde,opq]rubicene (1) should be available from
bis(ethynyl)acenaphthofluoranthene (Scheme 1). Both
cyclization precursors, 4 and 5, can be obtained from 7,9-
bis(trimethylsilyl)-8H-cyclopenta[a]acenaphthylen-8-one (6).
4
Compound 6 as a common intermediate in both syntheses can be
constructed from bis(ethynyl)naphthalene 7 and carbon monoxide
using our iron-mediated [2+2+1] cycloaddition and demetalation
protocol.[9]
[
a]
Dr. J. R. Suresh, Dr. G. Whitener, G. Theumer, Dr. D. J. Bröcher,
Dr. I. Bauer, Prof. Dr. H.-J. Knölker
Fakultät Chemie, Technische Universität Dresden
Bergstraße 66, 01069 Dresden (Germany)
https://tu-dresden.de/mn/chemie/oc/oc2
E-mail: hans-joachim.knoelker@tu-dresden.de
Prof. Dr. W. Massa
[
b]
Fachbereich Chemie, Philipps-Universität Marburg
Hans-Meerwein-Straße 4, 35043 Marburg (Germany)
Transition Metals in Organic Synthesis, Part 142. For Part 141, see:
B. Spindler, O. Kataeva, H.-J. Knölker, J. Org. Chem. 2018, 83,
*
*
15136–15143.
Supporting information and the ORCID identification number for the
author of this article can be found under
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Scheme 2. Synthesis of compound 6. Reagents and conditions: a) NaNO
equiv), H SO , KI (6.1 equiv), H O, −20 °C to 80 °C, 30 min (70%); b) TMSA
3.0 equiv), Pd(PPh Cl (2 mol%), CuI (4 mol%), NEt , RT, 12 h (95%); c)
(2.0 equiv), DME, sealed tube, 140 °C, 20 h (89%); d) (CH NO ×
2
(3.0
2
4
2
(
)
3 2
2
3
Fe(CO)
5
3 3
)
2
H
2
O (8.0 equiv), acetone, RT, 2 h (89%); e) 1. 1 M NaOH (8.4 equiv), THF,
RT, 2.5 h; 2. C 11I (16 equiv), RT, 15 min; 3. H PO , RT; 4. air, daylight,
Et O/THF, Na , Celite, RT, 3 h (91%). DME = 1,2-dimethoxyethane, TMSA
trimethylsilylacetylene.
5
H
S O
2 2 3
3
4
2
=
Cyclopentadienones have been frequently employed as
diene components in Diels–Alder reactions.[14] They can be
smoothly converted to benzene moieties by reaction with alkynes
with concomitant loss of carbon monoxide in a cheletropic
reaction. This method has been widely used for the construction
of larger PAHs.[15] Following this route, we reported the
Scheme 1. Retrosynthetic comparison between the syntheses of corannulene
(3) and dibenzo[cde,opq]rubicene (1).
At first, we synthesized intermediate 6 following our
sequence reported for the construction of corannulene (3).[8]
Thus, 1,8-diaminonaphthalene (8) was transformed into 1,8-
diiodonaphthalene (9) according to a literature protocol (Scheme
transformation
of
3,4-annulated
2,5-
bis(trimethylsilyl)cyclopentadienones into annulated benzene
derivatives by reaction with the electron-deficient dimethyl
acetylenedicarboxylate (DMDA).[16] Alternatively, benzene rings
can be formed by Diels–Alder reaction of cyclopentadienones
[
10]
2).
1,8-Bis(trimethylsilylethynyl)naphthalene (7) was obtained
in excellent yield by a double Sonogashira coupling of 9 with
monotrimethylsilylacetylene.[11] The iron-mediated [2+2+1]
cycloaddition of 7 with pentacarbonyliron was performed in 1,2-
dimethoxyethane in a sealed tube at 140 °C and led to the
[14]
with alkenes followed by decarbonylation and aromatization.
The aromatization can be achieved by dehydrogenation at higher
temperatures and/or addition of oxidizing agents like DDQ or
4
[17]
tricarbonyl(η -cyclopentadienone)iron complex 10 in 89% yield.
KMnO4.
The presence of a leaving group at the dienophile
4
[14]
For the demetalation of tricarbonyl(η -cyclopentadienone)iron
enables an aromatization by an elimination process.
This
complexes, we have developed three different methods.[12,13]
principle has been exploited for the construction of various 7,14-
disubstituted acenaphtho[1,2-k]fluoranthenes from 1-
Firstly, trimethylamine N-oxide was employed for this
purpose.[9a,12]
Thus,
reaction
of
the
tricarbonyl(η4-
haloacenaphthylene and 8H-cyclopenta[a]acenaphthylen-8-
ones.[18] We used acenaphthylenyl acetate 11 as dienophile for
the Diels–Alder reaction with the cyclopenta[a]acenaphthylen-8-
one 6 (Scheme 3). The reaction was performed at 200 °C under
neat conditions resulting in aromatization by in situ cheletropic
extrusion of carbon monoxide and elimination of acetic acid to
give acenaphtho[1,2-k]fluoranthene 12. The product proved to be
labile during column chromatography on silica gel losing the
trimethylsilyl groups by protodesilylation. Therefore, compound
12 was not purified but used directly for the subsequent
transformation. The ipso-substitution of the trimethylsilyl groups
cyclopentadienone)iron complex 10 with trimethylamine N-oxide
in acetone at room temperature provided the free
cyclopentadienone 6 in 89% yield. Another method proceeds via
a photolytically induced threefold ligand exchange reaction of
carbonyl against acetonitrile.[13a] The resulting (triacetonitrile)iron
complexes can be demetalated under very mild conditions at
−30 °C by injection of air. Finally, the tricarbonyliron fragment can
also be removed using our protocol based on a sequence of
Hieber base reaction/iodo–hydrido ligand exchange/protonation
and finally demetalation of the resulting dicarbonyl(η5-
hydroxycyclopentadienyl)iodoiron complex by air in the presence
of daylight.[13b] Using this protocol, we were able to obtain the
cyclopentadienone 6 in 91% yield.[8]
using iodine monochloride following a literature procedure[ led
19]
[20]
to the diiodide 13. Twofold Negishi coupling
trimethylsilylethynylzinc chloride
of 13 with
afforded
7,14-
bis(trimethylsilylethynyl)acenaphtho[1,2-k]fluoranthene (4). The
final twofold cyclization was achieved by flash vacuum pyrolysis
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COMMUNICATION
(
FVP).[21] This method has been frequently employed for the
X-ray analyses revealed only minor variations for the structures
1a and 1b with respect to C–C bond lengths and angles (Figure
2, Tables S1, S2). Both molecular structures are nearly perfectly
planar with mean deviations from best planes of 0.006(2) Å (1a)
and 0.016(2) Å (1b), respectively. Both modifications show
stacking of the molecules in a parallel offset way, typical for
systems with π–π interactions, and a zigzag arrangement of the
molecular layers (Figures 3, S28). The main differences between
both forms are the strength of the π–π interactions with distances
between the molecular planes of 3.414 Å (1a) and 3.474 Å (1b),
respectively, and the zigzag angles of 88.93(2) ° for 1a and
51.49(3) ° for 1b. The longitudinal axes of the molecules are
oriented in the direction of the corrugation in 1a and orthogonal to
it in 1b (Figures 3, S28). The offset shift of the molecules is in the
direction of their longitudinal axis for 1a and orthogonal to it for 1b
(Figure S29).
construction of geodesic and planar polyarenes.[21b,21d,21g]
In agreement with Scott and Zimmermann, we observed
that free alkynylarenes and alkynylalkenes are often labile and
tend to polymerize under the conditions of FVP.[22] To circumvent
this fact, various types of masked alkynylarenes have been
[
23]
employed
chlorovinylarenes,[
such
as
2,2-dibromovinylarenes,
1-
7,24]
[25]
and 1-silyloxyvinylarenes. Zimmermann
and coworkers described the use of trimethylsilyl-protected
alkynylalkenes for the synthesis of corannulene by FVP.[22b] We
could show for the first time that trimethylsilyl-protected
alkynylarenes can be directly introduced to FVP affording
corannulene in 36% yield.[8] Thus, in the present synthesis of
dibenzo[cde,opq]rubicene (1) we employed the trimethylsilyl-
protected bis(ethynyl)acenaphthofluoranthene 4 directly for the
final cyclization step. The flash vacuum pyrolysis of compound 4
was conducted at 1000 °C in a gentle argon stream at 1 mbar.
The carrier gas served to reduce the dwell time of the starting
material in the hot pyrolysis zone to reduce decomposition.
Dibenzo[cde,opq]rubicene (1) precipitated in the cold part of the
quartz tube and was isolated in 10% yield after column
chromatography.
1a
1b
Figure 2. Molecular structure of dibenzo[cde,opq]rubicene (1) in the structural
modifications 1a and 1b. Displacement ellipsoids at the 50% probability level.
Scheme 3. Synthesis of dibenzo[cde,opq]rubicene (1). Reagents and
conditions: a) 1. 11 (1.7 equiv), 200 °C, 45 min; 2. ICl (3.0 equiv), CCl
4
, 0 °C to
RT, 16 h (48%, 2 steps); b) Me SiCCZnCl (9.9 equiv), Pd(PPh (10 mol%),
3
3 4
)
THF, reflux, 15 h (94%); c) FVP, 1000 °C, 1–1.2 mbar Ar (10%). FVP = flash
vacuum pyrolysis.
Crystals of two different modifications of 1 (1a and 1b) were
both suitable for single crystal X-ray structure determination. The
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1,8-Diiodonaphthalene (9): 1,8-Diaminonaphthalene (8) (1.00 g, 6.32
mmol) was suspended in 6.9 M sulfuric acid (12 mL) and cooled to −20 °C.
A solution of sodium nitrite (1.29 g, 18.7 mmol) in water (5 mL) was added
dropwise. During this process, the temperature must be kept below
−
15 °C. Subsequently, a solution of potassium iodide (6.42 g, 38.7 mmol)
in water (6 mL) was added at the same temperature. If required, small
amounts of sulfuric acid have to be added to avoid freezing of the solution.
The mixture was heated to 80 °C and stirred for 30 min. Then, the solution
was cooled to 0 °C and adjusted to pH 10 by addition of a concentrated
sodium hydroxide solution. The black precipitate was filtered off, ground,
and extracted five times with 10 mL of diethyl ether. The combined organic
layers were washed with 10% hydrochloric acid, a saturated aqueous
solution of sodium thiosulfate, and dilute aqueous sodium hydroxide, dried
with magnesium sulfate and concentrated in vacuum. The resulting brown
residue was recrystallized from hexane to afford compound 9 (1.68 g, 4.42
mmol, 70%) as red-brown crystals. M.p. 109–110 °C; UV (CHCl
3
): λ = 221,
2
1
1
6
2
40, 311 nm; IR (DRIFTS): ν = 3827, 3436, 3052, 2360, 2112, 1930, 1871,
800, 1700, 1595, 1555, 1534, 1489, 1432, 1418, 1363, 1348, 1318, 1249,
215, 1180, 1132, 1091, 1050, 970, 936, 907, 827, 810, 803, 768, 746,
70, 642, 607 cm−1; 1H NMR (500 MHz, CDCl
): δ = 7.07 (br t, J = 7.7 Hz,
H), 7.83 (dd, J = 8.1, 1.1 Hz, 2 H), 8.42 (dd, J = 7.3, 1.1 Hz, 2 H); 13C
): δ = 96.00 (2 C), 126.95 (2 CH), 131.03
2 CH), 132.12 (C), 135.80 (C), 144.04 (2 CH); MS (EI): m/z (%) = 380 (78,
3
NMR and DEPT (125 MHz, CDCl
(
3
+
[M] ), 253 (34), 127 (13), 126 (100), 74 (10); HRMS (EI): m/z calcd for
Figure 3. Packing of molecules in 1a (top) and 1b (bottom). View approximately
C
10
H
6
I
I
2
: 379.8559; found: 379.8564; elemental analysis calcd (%) for
: C 31.61, H 1.59; found: C 32.09, H 1.79.
along the a axes of the unit cells.
C
10
H
6
2
1
(
,8-Bis(2-trimethylsilylethynyl)naphthalene (7): 1,8-Diiodonaphthalene
9) (1.00 g, 2.63 mmol) was dissolved in triethylamine (10 mL) followed by
the addition of trimethylsilylacetylene (1.09 mL, 775 mg, 7.89 mmol). The
mixture was stirred for 10 min at RT and then
Conclusion
We have developed a straightforward eight-step-synthesis of
dibenzo[cde,opq]rubicene (1). Key steps are the iron-mediated
bis(triphenylphosphane)palladium dichloride (37.0 mg, 0.053 mmol) and
copper(I) iodide (20.0 mg, 0.105 mmol) were added. After 12 h of stirring
at RT, diethyl ether (20 mL) was added. The organic solution was washed
successively with saturated aqueous solutions of NH
NaCl (20 mL each). The combined aqueous layers were extracted with
diethyl ether (20 mL). The combined organic layers were dried (MgSO
[
2+2+1] cycloaddition and
a
flash vacuum pyrolysis.
Dibenzo[cde,opq]rubicene (1) crystallized in two modifications
containing almost identical molecular structures in different
packing modes.
4 3
Cl, NaHCO , and
4
)
and the solvent was evaporated. Purification of the residue by column
Experimental Section
chromatography (silica gel, pentane) afforded compound 7 (800 mg, 2.50
mmol, 95%) as red-black oil. UV (CHCl
3
): λ = 221, 240, 271, 330, 345 nm;
General: All reactions were carried out in oven-dried glassware using
anhydrous solvents under an argon atmosphere, unless stated otherwise.
Dichloromethane and tetrahydrofuran were dried using
IR (DRIFTS): ν = 3314, 3058, 2959, 2899, 2143, 1939, 1565, 1502, 1426,
1
7
7
=
407, 1370, 1351, 1262, 1249, 1162, 1121, 1030, 1009, 856, 827, 765,
09, 651, 627, 614 cm−1. 1H NMR (400 MHz, CDCl
): δ = 0.33 (s, 18 H),
.39 (dd, J = 8.0, 7.3 Hz, 2 H), 7.77 (dd, J = 8.3, 1.1 Hz, 2 H), 7.81 (dd, J
7.2, 1.1 Hz, 2 H); 13C NMR and DEPT (100 MHz, CDCl
): δ = 0.16 (6
), 103.00 (2 C), 105.38 (2 C), 120.64 (2 C), 125.36 (2 CH), 129.76 (2
a solvent
3
purification system (MBraun-SPS). TLC was performed with TLC plates
from Merck (60 F254) using UV light for visualization. Melting points were
measured on the melting point apparatuses Büchi Type 535 or
Gallenkamp MPD 350, respectively. Ultraviolet spectra were recorded on
a PerkinElmer 25 UV/Vis spectrometer. IR spectra were recorded on
Bruker IFS 88 FT-IR or Thermo Nicolet Avatar 360 FT-IR spectrometers
using the DRIFTS (Diffuse Reflectance Infrared Fourier Transform
Spectroscopy) or ATR (Attenuated Total Reflectance) method,
respectively. NMR spectra were recorded on Bruker AM 400, DRX 500,
and Avance III 600 spectrometers. Chemical shifts δ are reported in parts
per million with the solvent signal as internal standard. Standard
abbreviations were used to denote the multiplicities of the signals. Mass
spectra (nominal masses) and high-resolution mass spectra were
recorded on Finnigan MAT-90 and MAT-95 spectrometers (electron
impact, 70 eV). Mass spectra with nominal masses were also obtained by
GC-MS coupling using an Agilent Technologies 6890 N GC System
equipped with a 5973 Mass Selective Detector (electron impact, 70 eV).
Elemental analyses were measured on Heraeus CHN-Rapid or
EuroVector EuroEA3000 elemental analyzers. X-ray analysis: Data
collection on area detector system IPDS-II (Stoe). Structures solved with
3
CH
3
CH), 130.34 (C), 133.79 (C), 136.90 (2 CH); MS (EI): m/z (%) = 320 (100,
+
[
M] ), 305 (29), 288 (12), 286 (25), 284 (12), 248 (44), 234 (18), 233 (90),
217 (37), 205 (13), 189 (15), 126 (17), 73 (75); HRMS (EI): m/z calcd for
20
C H24Si
2
: 320.1417; found: 320.1427.
4
Tricarbonyl -7,9-bis(trimethylsilyl)-8H-
cyclopentaaacenaphthylen-8-oneiron (10): 1,8-Bis(2-trimethylsilyl-
ethynyl)naphthalene (7) (1.72 g, 5.37 mmol), pentacarbonyliron (1.42 mL,
2
.06 g, 10.5 mmol) and 1,2-dimethoxyethane (25 mL) were heated in a
sealed tube (borosilicate glass Schott Duran 50, 15×2.4 cm, wall thickness
.8 mm) at 140 °C for 20 h. After evaporation of the solvent, the crude
1
product was purified by column chromatography (silica gel, hexane/ethyl
acetate, 10:1). The iron complex 10 (2.34 g, 4.79 mmol, 89%) was
obtained as yellow crystals. M.p. 188–189 °C (dec.); UV (CHCl
3
): λ = 231,
3
1
1
7
14 nm; IR (DRIFTS): ν = 3421, 3060, 2957, 2901, 2058, 2009, 1995,
987, 1966, 1955, 1819, 1744, 1632, 1599, 1487, 1432, 1371, 1348, 1293,
248, 1212, 1199, 1187, 1155, 1060, 1045, 964, 911, 846, 828, 778, 765,
direct methods (SIR2002)[26] and refined with SHELXL2018/3[27]
.
44, 722, 703, 637, 608 cm−1; 1H NMR (400 MHz, CDCl
3
): δ = 0.52 (s, 18
H), 7.64 (br t, J = 7.6 Hz, 2 H), 7.93 (d, J = 8.3 Hz, 2 H), 7.96 (d, J = 7.1
Hz, 2 H); 13C NMR and DEPT (100 MHz, CDCl
): δ = 0.09 (6 CH ), 69.53
3
3
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COMMUNICATION
(
2 C), 110.34 (C), 123.91 (2 CH), 128.14 (2 CH), 128.45 (2 CH), 130.58 (2
500 MHz): δ = 2.39 (s, 3 H), 6.93 (s, 1 H), 7.49 (t, J = 7.5 Hz, 1 H), 7.54 (t,
J = 7.5 Hz, 1 H), 7.58 (d, J = 6.8 Hz, 1 H), 7.67 (d, J = 6.9 Hz, 1H), 7.74
C), 132.50 (2 C), 136.01 (C), 183.00 (C), 208.43 (3 C); MS (EI): m/z (%) =
+
(d, J = 8.3 Hz, 1 H), 7.83 (d, J = 8.1 Hz, 1 H); 13C NMR and DEPT (CDCl
125 MHz): δ = 21.27 (CH ), 112.96 (CH), 121.80 (CH), 124.16 (CH),
4
3
4
88 (11, [M] ), 460 (15), 433 (23), 432 (69), 405 (34), 404 (100), 376 (14),
3
,
33 (15), 317 (15), 73 (15); HRMS (EI): m/z calcd for C24
88.0563; found: 488.0541; elemental analysis calcd (%) for
Si : C 59.01, H 4.95; found: C 59.06, H 5.00.
4
H24FeO Si
2
:
3
124.87 (C), 126.64 (CH), 127.23 (CH), 127.71 (C), 127.97 (CH), 128.26
C
24
H
24FeO
4
2
(CH), 133.54 (C), 136.54 (C), 150.96 (C), 168.16 (C); MS (EI): m/z (%) =
+
2
10 (6, [M] ), 168 (100), 139 (49), 113 (5).
7,9-Bis(trimethylsilyl)-8H-cyclopenta[a]acenaphthylen-8-one (6):
7,14-Diiodoacenaphtho[1,2-k]fluoranthene (13): Cyclopenta[a]ace-
naphthylen-8-one 6 (800 mg, 2.29 mmol) and acenaphthylene 11 (800 mg,
3.81 mmol) were stirred at 200 °C for 45 min. After cooling, the mixture
was treated with diethyl ether (100 mL). The solid was filtered off and
washed with diethyl ether to give 520 mg (1.10 mmol) of 7,14-
bis(trimethylsilyl)acenaphtho[1,2-k]fluoranthene (12) as a dark brown solid
of which a sample of 470 mg was used for the next transformation without
further purification. A solution of iodine monochloride (490 mg, 3.02 mmol)
in carbon tetrachloride (50 mL) was added to a solution of 7,14-
bis(trimethylsilyl)acenaphtho[1,2-k]fluoranthene (12) (470 mg, 0.998
mmol) in carbon tetrachloride (100 mL) at 0 °C within 5 min. The mixture
was stirred at room temperature for 16 h and then washed successively
By demetalation with trimethylamine N-oxide (Scheme 2, step d):
Tricarbonyl-[η -7,9-bis(trimethylsilyl)-8H-cyclopenta[a]acenaphthylen-8-
one]iron (10) (359 mg, 0.735 mmol) and trimethylamine N-oxide dihydrate
4
(653 mg, 5.88 mmol) were dissolved in acetone and stirred at room
temperature for 2 h. After filtration through a short pad of silica gel and
removal of the solvent, the crude product was purified by column
chromatography (silica gel, n-hexane). Compound 6 (229 mg, 0.657 mmol,
89%) was obtained as dark red crystals.
Demetalation via Hieber base reaction (Scheme 2, step e): Tricarbonyl4-
7,9-bis(trimethylsilyl)-8H-cyclopentaaacenaphthylen-8-oneiron
(10)
with saturated aqueous solutions of Na
aqueous layers were extracted with dichloromethane. The combined
organic layers were dried over MgSO . Evaporation of the solvent afforded
compound 13 (580 mg, 1.00 mmol, 48%, two steps) as a brown solid. M.p.
2 2 3 3
S O , NaHCO , and NaCl. The
(200 mg, 0.409 mmol) was dissolved in tetrahydrofuran (10 mL) and a 1 M
aqueous solution of sodium hydroxide (3.44 mL, 3.44 mmol) was added.
The mixture was vigorously stirred for 2.5 h at room temperature and then
4
1-iodopentane (0.85 mL, 1.29 g, 6.52 mmol) were added causing a rapid
3
1
55–360 °C (dec.); IR (ATR): ν = 3049, 2920, 2844, 1457, 1425, 1345,
color change to brown. After 15 min the mixture was acidified with conc.
phosphoric acid (0.85 mL, 16.2 mmol), extracted with diethyl ether, dried
229, 1179, 1107, 1047, 954, 905, 818, 761, 687, 629, 577, 537 cm−1; 1H
NMR (500 MHz, 1,1,2,2-tetrachloroethane-d
Hz, 4 H), 8.03 (d, J = 8.2 Hz, 4 H), 9.39 (d, J = 7.3 Hz, 4 H); 13C NMR and
DEPT (125 MHz, 1,1,2,2-tetrachloroethane-d , 80 °C): δ = 87.30 (2 C),
2
, 80 °C): δ = 7.84 (t, J = 7.7
2 4
(Na SO ), and filtered through a short pad of silica gel. The resulting
solution was diluted with diethyl ether to give a total volume of 250 mL.
Sodium thiosulfate pentahydrate (175 mg, 0.705 mmol) and Celite (175
mg) were added and the mixture gently stirred for 3 h at room temperature
in the presence of daylight and air. After filtration though a short pad of
silica gel and removal of the solvent, the crude product was purified by
column chromatography (silica gel, n-hexane). Compound 6 (130 mg,
2
1
1
3
24.88 (4 CH), 127.14 (4 CH), 128.39 (4 CH), 129.79 (2 C), 133.46 (2 C),
36.65 (4 C), 142.14 (4 C); MS (EI): m/z (%) = 578 (100, [M] ), 452 (11),
24 (68), 322 (13), 289 (10), 162 (27), 161 (14); elemental analysis calcd
+
12
(%) for C26H I
2
: C 54.01, H 2.09; found: C 53.68, H 2.22.
0.373 mmol, 91%) was obtained as dark red crystals.
7,14-Bis(trimethylsilylethynyl)acenaphtho[1,2-k]fluoranthene
(4):
Butyllithium (3.60 mL, 1.6 M in hexane, 5.76 mmol) was slowly added to a
solution of trimethylsilylacetylene (540 mg, 5.50 mmol) in dry
tetrahydrofuran (13 mL) at −78 °C. The mixture was stirred at −78 °C for
40 min and then warmed to 0 °C. A solution of zinc chloride (7.86 mL, 0.7
M in THF, 5.50 mmol) was added and the mixture was stirred for 3 h at
0 °C. The resulting solution of trimethylsilylethynylzinc chloride was slowly
M.p. 182–183 °C (dec.); UV (CHCl
3
): λ = 224, 250, 285, 344, 353, 363,
3
1
1
83, 486 nm; IR (DRIFTS): ν = 3346, 3058, 2958, 2898, 2493, 1928, 1872,
792, 1682, 1618, 1604, 1560, 1486, 1411, 1353, 1245, 1211, 1180, 1141,
098, 1067, 1045, 1000, 968, 847, 771, 731, 698, 635 cm−1; 1H NMR (500
3
MHz, CDCl ): δ = 0.41 (s, 18 H), 7.63 (br t, J = 7.7 Hz, 2 H), 7.84 (d, J =
.1 Hz, 2 H), 7.85 (d, J = 8.2 Hz, 2 H); 13C NMR and DEPT (125 MHz,
7
added to
a solution of diiodide 13 (320 mg, 0.553 mmol) and
CDCl
3 3
): δ = −0.42 (6 CH ), 122.32 (2 CH), 125.27 (2 C), 127.33 (2 CH),
tetrakis(triphenylphosphine)palladium (66.0 mg, 0.057 mmol) in dry
tetrahydrofuran (13 mL) at 0 °C. The mixture was heated at reflux for 15 h.
After cooling to room temperature the mixture was filtered through a short
pad of Celite. The crude product obtained after removal of the solvent was
purified by column chromatography (basic alumina, activity grade 4,
petroleum ether/dichloromethane, 20:1) to provide compound 4 (270 mg,
1
28.39 (2 CH), 131.99 (C), 132,02 (2 C), 144.35 (C), 169.15 (2 C), 212.74
+
(C); MS (EI): m/z (%) = 348 (100, [M] ), 334 (19), 333 (66), 332 (15), 331
(42), 317 (18), 275 (10), 217 (14), 216 (14), 215 (11), 159 (10), 133 (37),
117 (19), 73 (48); HRMS (EI): m/z calcd for C21
2
H24OSi : 348.1366; found:
348.1379; elemental analysis calcd (%) for C21
2
H24OSi : C 72.36, H 6.94;
found: C 72.34, H 7.11.
0
2
7
.520 mmol, 94%) as a yellow solid. M.p. 351–352 °C; IR (ATR): ν = 3049,
956, 2148, 1435, 1427, 1246, 1191, 1139, 1036, 983, 877, 837, 821, 768,
Acenaphthylen-1-yl acetate (11): Butyllithium (5.10 mL, 1.58 M in
hexane, 8.06 mmol) was slowly added to a solution of diisopropylamine
55, 704, 635 cm–1; 1H NMR (500 MHz, CDCl
3
): δ = 0.52 (s, 18 H), 7.71
(
dd, J = 7.3, 7.9 Hz, 4 H), 7.92 (d, J = 8.1 Hz, 4 H), 8.73 (d, J = 7.0 Hz, 4
H); 13C NMR and DEPT (125 MHz, CDCl
): δ = 0.03 (6 CH ), 102.55 (2 C),
05.39 (2 C), 112.98 (2 C), 123.65 (4 CH), 127.40 (4 CH), 127.89 (4 CH),
(1.30 mL, 936 mg, 9.25 mmol) in tetrahydrofuran (10 mL) at −78 °C. The
3
3
mixture was stirred for 15 min at this temperature. solution of
commercially available acenaphthylen-1-one (1.00 g, 5.95 mmol) in
tetrahydrofuran (20 mL) was slowly added and stirring was continued at
A
1
1
5
29.47 (2 C), 132.96 (2 C), 135.48 (4 C), 139.10 (4 C); MS (EI): m/z (%) =
+
18 (100, [M] ), 487 (6), 429 (5), 422 (6), 416 (7), 415 (11), 413 (6), 73
−
78 °C for 2 h. After warming to 0 °C, acetic anhydride (0.800 mL, 864 mg,
2
(12); elemental analysis calcd (%) for C36H30Si : C 83.34, H 5.83; found: C
8.46 mmol) was added. The mixture was allowed to warm to room
83.38, H 5.73.
temperature and stirred for 14 h. After addition of water and
dichloromethane, the layers were separated and the aqueous layer was
extracted three times with dichloromethane. The combined organic layers
were dried (MgSO ) and the solvent evaporated. Purification by column
4
chromatography (silica gel, petroleum ether/diethyl ether, 20:1), provided
Dibenzo[cde,opq]rubicene (1): The apparatus for flash vacuum pyrolysis
FVP)[21] consisted of a quartz tube (100 × 4 cm o.d.) connected to a
(
cooling trap (liquid nitrogen) and a vacuum pump on the one end and an
argon supply on the other. The quartz tube was inserted into two quartz
tube furnaces, a sublimation oven (30 × 5 cm i.d.) on the side of the argon
supply and a pyrolysis oven (40 × 7 cm i.d.) on the side of the cooling trap.
compound 11 (800 mg, 3.81 mmol, 64%) as a yellow solid. M.p. 46 °C; IR
(
1
ATR): ν = 3043, 1760, 1744, 1521, 1479, 1464, 1429, 1371, 1304, 1190,
129, 1072, 1012, 876, 829, 758, 707, 663, 588 cm−1; 1H NMR (CDCl
,
3
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COMMUNICATION
Korsh, A. Shen, K. Aliano, T. Davenport, Breast Care 2015, 10,
316–318.
7
,14-Bis(trimethylsilylethynyl)acenaphtho[1,2-k]fluoranthene (4) (270 mg,
0.520 mmol) was given into a porcelain boat which was placed in a quartz
tube in the center of the sublimation oven. At the start of the pyrolysis
experiment, the system was evacuated to 5 · 10−3 mbar. Then, the argon
supply was opened to adjust a gentle flow of argon up to a final pressure
of 1–1.2 mbar. The pyrolysis oven was turned on and equilibrated at
[
2]
a) X. Feng, W. Pisula, K. Müllen, Pure Appl. Chem. 2009, 81, 2203–
2
224; b) W. Pisula, X. Feng, K. Müllen, Chem. Mater. 2011, 23,
54–567; c) X. Guo, M. Baumgarten, K. Müllen, Prog. Polym. Sci.
5
1000 °C. Then the sublimation oven was heated to 380 °C. The sample
2013, 38, 1832–1908.
was kept at this temperature for 4 h and then at 420 °C for another 2 h.
The product precipitated at the cold part of the quartz tube. Subsequently,
the tube was cooled to room temperature, vented, opened, and the product
was dissolved in dichloromethane. Evaporation of the solvent provided
[3]
[4]
a) M. Frenklach, E. D. Feigelson, Astrophys. J. 1989, 341, 372–384;
b) I. Cherchneff, Y. H. Le Teuff, P. M. Williams, A. G. G. M. Tielens,
Astron. Astrophys. 2000, 357, 572–580; c) A. G. G. M. Tielens,
Annu. Rev. Astron. Astrophys. 2008, 46, 289–337.
1
00 mg of crude product. Column chromatography (silica gel,
pentane/dichloromethane, 15:1) afforded dibenzo[cde,opq]rubicene (1)
20.0 mg, 0.053 mmol, 10%) as a dark red solid. M.p. >370 °C; UV (CHCl ):
λ = 283, 316, 342, 425, 449 nm; IR (ATR): ν = 3031, 1633, 1552, 1456,
a) F. Salama, Proc. Int. Astron. Union 2008, 4, 357–366; b) L.
Verstraete, EAS Publ. Ser. 2011, 46, 415–426; c) M. Steglich, J.
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J. P. Maier, Y. Carpentier, G. Rouillé, M. Steglich, C. Jäger, T.
Henning, F. Huisken, J. Oomens, O. Pirali, A. G. G. M. Tielens, H.
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Mutschke, T. Giesen, C. Jäger), Wiley-VCH, Weinheim, 2015, pp.
(
3
1
7
7
419, 1324, 1256, 1215, 1188, 1163, 1135, 1016, 957, 933, 903, 859, 821,
66, 731, 625, 590, 556 cm–1; 1H NMR (600 MHz, CDCl
): δ = 7.77 (t, J =
.4 Hz, 2 H, H-4), 7.97 (d, J = 8.0 Hz, 2 H, H-5), 7.97 (d, J = 8.6 Hz, 2 H,
3
H-14), 8.01 (d, J = 8.5 Hz, 2 H, H-13), 8.09 (d, J = 8.7 Hz, 2 H, H-1), 8.46
(
(
(
d, J = 6.8 Hz, 2 H, H-3), 8.56 (d, J = 8.8 Hz, 2 H, H-2); 13C NMR and DEPT
150 MHz, CDCl ): δ = 125.13 (C-2), 125.52 (C-14), 125.61 (C-3), 127.02
C-5), 127.11 (C-13), 127.29 (C-1), 128.87 (C-4) (chemical shifts derived
3
from the HSQC spectrum, assignment achieved by COSY, NOESY,
+
HSQC, HMBC measurements); MS (EI): m/z (%) = 347 (100, [M] ), 372
(
39), 370 (18), 368 (6), 221 (8), 204 (17), 186 (32), 59 (10); HRMS (EI):
m/z calcd for C30 14: 374.1096; found: 374.1084. Detailed IR and UV/Vis
spectroscopic studies of 1 have been published by us previously.
H
[
4d]
1
3–108.
J. Cami, J. Bernard-Salas, E. Peeters, S. E. Malek, Science 2010,
29, 1180–1182.
Crystallization afforded two different modifications of 1 which were
analyzed by X-ray diffractometry.
[
5]
3
14, M = 374.41 g mol‒1, crystal size: 0.50
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Chem. Int. Ed. 2013, 52, 1289–1293; Angew. Chem. 2013, 125,
Crystallographic data for 1a: C30
H
3

4
ρ
2
1
0.07  0.03 mm , monoclinic, space group P2
1
/n, a = 9.1654 (18) Å, b =
3
.8663 (6) Å, c = 19.186 (4) Å, β = 93.268 (16)°, V = 854.3 (3) Å , Z = 2,
calcd = 1.455 g/cm , μ = 0.08 mm‒1, λ = 0.71073 Å, T = 100 K, θ range:
.1‒25.0°, reflections collected: 6309, independent: 1508 (Rint = 0.091),
1327–1331; b) M.-K. Chen, H.-J. Hsin, T.-C. Wu, B.-Y. Kang, Y.-W.
3
Lee, M.-Y. Kuo, Y.-T. Wu, Chem. Eur. J. 2014, 20, 598–608; c) J.
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58 parameters. The structure was solved by direct methods and refined
2
by full-matrix least-squares on F ; final R indices [I > 2σ(I)]: R
1
= 0.048,
wR
917204 contains the supplementary crystallographic data for this
2
= 0.111; maximal residual electron density: 0.20 e Å–3. CCDC
1
structure. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
1
559; e) J.-L. Huang, B. Rao, M. P. Kumar, H.-F. Lu, I. Chao, C.-H.
Lin, Org. Lett. 2019, 21, 2504–2508; f) Y. Zou, W. Zeng, T. Y.
Gopalakrishna, Y. Han, Q. Jiang, J. Wu, J. Am. Chem. Soc. 2019,
141, 7266–7270.
14, M = 374.41 g mol‒1, crystal size: 0.50
Crystallographic data for 1b: C30
H
3

3
ρ
1
1
0.15  0.02 mm , monoclinic, space group P2
1
/c, a = 14.198 (3) Å, b =
3
.8562 (5) Å, c = 16.196 (4) Å, β = 106.75 (2)°, V = 849.1 (3) Å , Z = 2,
calcd = 1.464 g/cm , μ = 0.08 mm‒1, λ = 0.71073 Å, T = 100 K, θ range:
.5‒25.0°, reflections collected: 3572, independent: 1491 (Rint = 0.072),
[7]
M. Matsuda, H. Matsubara, M. Sato, S. Okamoto, K. Yamamoto,
Chem. Lett. 1996, 25, 157–158.
3
[
8]
H.-J. Knölker, A. Braier, D. J. Bröcher, P. G. Jones, H. Piotrowski,
Tetrahedron Lett. 1999, 40, 8075–8078.
57 parameters. The structure was solved by direct methods and refined
2
by full-matrix least-squares on F ; final R indices [I > 2σ(I)]: R
1
= 0.049,
wR
2
= 0.124; maximal residual electron density: 0.15 e Å–3. CCDC
[9]
a) H.-J. Knölker, J. Heber, C. H. Mahler, Synlett 1992, 1002–1004;
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Appl. Chem. 2001, 73, 1075–1086.
1917209 contains the supplementary crystallographic data for this
structure. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Keywords: Polycyclic aromatic hydrocarbons • cycloadditions •
flash vacuum pyrolysis • X-ray diffraction • polymorphism
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Chemistry - A European Journal
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COMMUNICATION
COMMUNICATION
An uncurved C30 fragment of C70
fullerene: Dibenzo[cde,opq]rubicene
as a fragment of C70 fullerene was
synthesized using an iron-mediated
J. R. Suresh, G. Whitener, G. Theumer,
D. J. Bröcher, I. Bauer, W. Massa, H.-J.
Knölker*
[
2+2+1] cycloaddition und flash
Page No. – Page No.
vacuum pyrolysis. Two structural
modifications were obtained showing
perfectly planar single molecules in
different packing modes.
Synthesis and Crystal Structure of
Dimorphic Dibenzo[cde,opq]rubicene
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