From chrysene to double [5] Helicenes

Article abstract of DOI:10.1002/ejoc.201403341

Glyoxylic functionalization of chrysene by Friedel-Crafts acylation with ethyl chloroglyoxylate or by bromination followed by substituent exchange enables the formation of bis[5]helicene-tetracarboxylates and tetracarboxdiimides through Perkin reactions and palladium-catalyzed cyclizations. Tetrasubstituted bishelicenic dichrysenoanthracenes and dinaphthochrysenes are thus obtained from chrysene in four to six steps. In the cyclization to dinaphthochrysenes, a rearrangement of the conjugated carbon skeleton is identified as side reaction. In solution, the diimides form mixtures of M,P- and M,M/P,P-diastereomers, which equilibrate at room temperature when the helices are distant but equilibrate only upon heating when the helices are close and acting in concert. The nonplanar arene geometry allows close π-contacts in two dimensions between neighboring molecules in the crystal.

Full text of DOI:10.1002/ejoc.201403341

FULL PAPER
DOI: 10.1002/ejoc.201403341
From Chrysene to Double [5]Helicenes
Harald Bock,*[a] Stephanie Huet,[a] Pierre Dechambenoit,[b] Elizabeth A. Hillard,[a] and
Fabien Durola*[a]
Keywords: Helical structures / Donor–acceptor systems / Pi interactions / Rearrangement / Cyclization
Glyoxylic functionalization of chrysene by Friedel–Crafts
acylation with ethyl chloroglyoxylate or by bromination
followed by substituent exchange enables the formation of
bis[5]helicene-tetracarboxylates and tetracarboxdiimides
through Perkin reactions and palladium-catalyzed cycliza-
tions. Tetrasubstituted bishelicenic dichrysenoanthracenes
and dinaphthochrysenes are thus obtained from chrysene in
four to six steps. In the cyclization to dinaphthochrysenes, a
rearrangement of the conjugated carbon skeleton is iden-
tified as side reaction. In solution, the diimides form mixtures
of M,P- and M,M/P,P-diastereomers, which equilibrate at
room temperature when the helices are distant but equili-
brate only upon heating when the helices are close and act-
ing in concert. The nonplanar arene geometry allows close
π-contacts in two dimensions between neighboring mol-
ecules in the crystal.
even with the shortest alkyl ester substituents, to the extent
that crystallization may be suppressed by formation of an
anisotropic glass.[3]
Introduction
Large, highly condensed arenes with a small number of
aromatic sextets offer smaller band gaps and concordantly
longer wavelength absorption than their more sextetted iso-
mers, at the expense of reduced chemical stability, for exam-
ple against air-oxidation. This low stability can be dramati-
cally improved by the incorporation of electron-with-
drawing substituents, such as carboxylic ester and especially
dicarboximide groups. These substituents not only improve
the stability by lowering the LUMO energies, but also re-
duce the band gap with a further redshift of the absorption
edge and can improve solubility through the introduction
of alkyl chains of various lengths. The ability of alkylimide
groups to render planar arenes soluble is nevertheless lim-
ited by the size of the arene for a given number of substitu-
ents, as we experienced recently with a diperyleno-anthra-
cene bearing two long α-branched alkylimide groups, which
is soluble only on heating in chlorinated solvents.[1] The
strong coplanar aggregation of large arenes may be reduced
by the introduction of a bend or twist, as is illustrated by
the far superior solubilities of helicenes compared with their
planar phenacene isomers.[2] Even slight deviations from
planarity such as induced by a [4]helicene fragment may
give rise to good solubilities and to hindered crystallization
An interesting starting material for the construction of
nonplanar sextet-poor higher arenes is chrysene 1, which
(a) combines two sextets with three nonsextetted double
bonds, (b) contains two bay regions that are suitable for the
build-up of sterically crowded structures, and (c) may offer
a suitable regioselectivity upon double substitution in posi-
tions 6 and 12 to graft arylethylenyl substituents in appro-
priate positions for the formation of two helicenic frag-
ments in the bay regions. Alternatively, two chrysene-based
helicenic fragments in the same molecule could be gener-
ated by connecting two chrysenes monofunctionalized in
the 6-position by an arylenedivinylene bridge.
Results and Discussion
The Friedel–Crafts acylation of chrysene with ethyl
chloroglyoxylate ClCOCO2Et yields, after hydrolysis of the
obtained ethyl ester 2, chrysenyl-6-glyoxylic acid 3, which
allowed us recently to construct a chrysene-based [7]hel-
icene through glyoxylic Perkin condensation[4] with its own
reduction product chrysenyl-6-acetic acid.[5] However, nei-
ther 2 nor chrysenyl-6-acetic acid methyl ester could be
made to undergo a second acylation with ClCOCO2Et to
yield a 6,12-disubstituted product, with 2 being unreactive
and the acetic ester reacting in the 2- or 3-position.
An alternative approach to arylene-diglyoxylic esters that
we recently applied to 1,5-dibromoanthracene, which was
obtained in 80% yield, is the reaction of an arylene-dianion,
obtained from the corresponding dibromoarene, with di-
ethyl oxalate EtO2CCO2Et.[6] We therefore attempted to
transform the known 6,12-dibromochrysene 4,[7] which is
[a] Centre National de la Recherche Scientifique, Centre de
Recherche Paul Pascal,
115 avenue Schweitzer, 33600 Pessac, France
www.crpp-bordeaux.cnrs.fr
[b] Université de Bordeaux, Centre de Recherche Paul Pascal,
115 avenue Schweitzer, 33600 Pessac, France
E-mail: bock@crpp-bordeaux.cnrs.fr
durola@crpp-bordeaux.cnrs.fr;
http://www.crpp-bordeaux.cnrs.fr
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201403341.
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H. Bock, S. Huet, P. Dechambenoit, E. A. Hillard, F. Durola
FULL PAPER
conveniently obtained by bromination of 1 with Br2 in
chloroform, into the corresponding diglyoxylic ester 5 and
acid 6 via the chrysene 6,12-dianion and its reaction with
diethyl oxalate. In contrast to the anthracenylene-1,5-di-
anion, which forms in good yield with butyllithium at
–94 °C but decomposes partially at room temperature,
yields of chrysenylene-6,12-dianion improve (to give 5 in
75% yield) if, after addition of butyllithium, the reaction
mixture is warmed to room temperature. This shows that
whereas the chrysenylene-dianion is more stable once
formed due to the twofold sextet stabilization, its formation
requires harsher conditions due to the shorter distance be-
tween the two substitution positions.
The mono- and diglyoxylic acids 3 and 6 were subjected
to double Perkin condensations with 2,5-dibromopheny-
lene-1,4-diacetic acid 7[1] and 2-bromophenylacetic acid 8,
respectively, followed by same-pot fourfold esterification
with excess alkanol and 1-bromoalkane in the presence of
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to yield dibromo
phenylene-bis(chrysenylmaleic) tetrabutyl ester
9 and
chrysenylene-bis(bromophenylmaleic) tetrapropyl ester 10,
respectively, in 69 and 71% yield (Figure 1). These highly
congested yet conformationally flexible bismaleates show,
as usual,[1,5,6] extremely broadened proton NMR spectra
due to slow rotations on the measurement timescale.
The dehydrobromination of 9 in DMA at 110 °C in the
presence of catalytic palladium(II) acetate activated with
tricyclohexylphosphine[8] yielded dichrysenoanthracene
tetraester 11 in 52% yield, which had to be purified by care-
ful column chromatography and multiple recrystallizations
to eliminate traces of unidentified aromatic side products
of similar polarity. The nonplanarity of 11 is apparent in
its proton NMR spectrum: Instead of two triplets for the
oxygen-bound methylenes of the two nonequivalent butyl
chains, the spectrum shows four double triplets in the re-
gion around 4 ppm – the two hydrogen signals of each of
the two methylene groups become differentiated by the heli-
cal environment, and couple with each other (Figure 2).
The aromatic part of the spectrum of 11 shows the expected
11 signals for the 11 aromatic protons per half-molecule;
there is no doubling of the signals due to any coexistence
of two diastereomers (M,P and M,M/P,P) in solution.
The analogous double cyclization of 10 yielded naphtho-
chrysene tetraester 12[9] in significantly lower yield of 34%,
but, in this case, a relatively large amount (12%) of a
slightly more polar side product could be isolated in moder-
ate purity by careful column chromatography. Compared
with 12, this side product has the same molecular mass but
Figure 1. Synthesis of chrysene-based tetracarboxy-substituted
bis[5]helicenes. Reagents and conditions: (a) ClCOCO2Et, ZrCl4,
CH2Cl2, 25 °C, 16 h, 81%;[5] (b) Br2, CHCl3, reflux, 16 h, 74%;
(c) THF, BuLi, –94 °C to 25 °C, 4 h, then addition of EtO2CCO2Et,
–94 °C to 25 °C, 45 min, 75%; (d) NaHCO3, EtOH/H2O, reflux,
4 h, 100%; (e) NEt3, Ac2O, THF, reflux, 18 h, then addition of
ROH, RBr, DBU, reflux, 2 h, 69% (9) and 71% (10); (f) Pd-
(OAc)2, PCy3, K2CO3, DMA, 110 °C, 16 h, 52% (11) or 34% (12)
+ 12% (13); (g) Pent2CHNH2, imidazole, o-C6H4Cl2, reflux, 16 h,
74% (14) or 61% (15); Pent = n-pentyl.
1
shows a doubled set of signals in the H NMR spectrum,
with the same multiplicities and similar chemical shifts, ex-
cept for a very pronounced upfield shift for one of the four
distinct propyl chains. These data point to the side product
being the isomeric dinaphthochrysene 13, where one of the
two bromophenylmaleate substituents in 10 has migrated
from the 6-position to the 5-position on the chrysene core,
1
Figure 2. H NMR spectrum of 11 in CDCl3: region of the OCH2
protons showing four double triplets between δ = 4.4 and 3.7 ppm.
followed by cyclization onto the 6-position, leaving the spe- alene reversal puts one of the propyloxycarbonyl substit-
cific d-t-t-d 1H NMR signal pattern of the four four- uents under significant steric strain and forces it out of the
hydrogen-bearing benzene nuclei untouched. This naphth- main molecular plane, to experience the shielding influence
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From Chrysene to Double [5]Helicenes
of one of the terminal aromatic sextets of the central chrys- crop of crystals upon recrystallization, which showed only
ene moiety; this explains the strong differentiation of one of one single set of signals of one conformer in Cl2DC–CDCl2
1
the chains observed by H NMR spectroscopy. A selective at room temperature, but short heating to reflux led to the
relative upfield shift for the signals of one of the four sets appearance of a second set of signals with approximately
of propyl carbon atoms is also notable in the 13C NMR 0.3:1 intensity ratio to the main set, which corresponds to
spectrum, together with a selective relative downfield shift the ratio observed with samples from the main, more
of one of the four carbonyl carbon signals. Similar to 11, quickly precipitated recystallization crop. Changing the sol-
the oxygen-bound methylenes of the alkyl chains in 12 and vent to CD2Cl2 did not change the ratio.
13 show double triplet 1H NMR signals due to the absence
of mirror symmetry on the aromatic plane.
The nonseparable impurity signals discernible in the
1H NMR spectrum of 13 might stem from the correspond-
ing doubly rearranged symmetric isomer, in which the in-
version on chrysene positions 5 and 6 is mirrored by the
same inversion on positions 11 and 12. Similar rearrange-
ments might account for the impurities in crude 11, whereas
a greater abundance of rearranged product upon double cy-
clization of 10 compared with that of 9 may be caused by
the smaller size and thus greater mobility of the migrating
group in 10. This observed rearrangement is reminiscent
of the migrations between aromatic substitution positions
observed in Pd-catalyzed Heck and Suzuki reactions.[10]
To obtain the target diimides, we treated esters 11 and
12 with excess 6-aminoundecane and imidazole in o-di-
chloroethane heated to reflux, and obtained the respectively
red and orange diimides 14 and 15 in 74 and 61% yield.
Like the esters, these imides bearing four relatively short
peripheral pentyl chains are soluble in chlorinated solvents
at room temperature and dissolve in hot butanol, which was
our solvent of choice for recrystallizations.
Figure 3. 1H NMR spectrum of 14 in Cl2DC–CDCl2 (apolar,
above) and CD2Cl2 (polar, below): region of the aromatic protons
between δ = 10.0 and 6.8 ppm, showing distinct sets of signals for
two conformers of solvent-dependent relative abundance.
In contrast to the esters, the imides show a doubling of
1
the aromatic signals in the H NMR spectrum, indicating
a coexistence of the M,P and M,M/P,P diastereomers in
solution. As the additional imide cycles can be assumed to
The two diastereomeric forms of 14 thus interconvert in
rigidify the polycyclic cores, it appears that the M–P helix solution at room temperature, whereas the two dia-
reversal in the imides is slow compared with the experimen- stereomeric forms of 15 only do so at elevated temperatures.
tal timescale. To verify that the signal doubling can be at- The two [5]helicene moieties share more carbon atoms in
tributed without ambiguity to reversible helix inversion and 15 than in 14. This allows a more independent helix reversal
not to any other irreversible isomerization, we recorded the in 14 and requires more cooperativity between the two
spectrum of 14 at various temperatures in high-boiling helices in 15 during the reversal of one of them.
Cl2DC–CDCl2, but could not observe any change of the
In the 13C NMR spectra of both 14 and 15, the two lin-
approximate 1.2:1 integral ratio between the two sets of sig- ear pentyl moieties of each swallow-tail alkylimide group
nals. However, when the solvent was changed to CDCl3 or are differentiated, giving rise to two sets of five signals. This
CD2Cl2, which, in contrast to 1,1,2,2-tetrachloroethane, is analogous to the differentiation of the two OCH2
1
possess a permanent dipole moment, the ratio was reversed hydrogen signals of each alkyl chain in the H NMR spec-
to approximately 1:1.5 in chloroform and approximately 1:2 tra of 11, 12, and 13 brought about by the nonplanarity of
in dichloromethane (Figure 3). To ensure that these dif- the polycyclic molecular cores.
ferent ratios are not caused by random variations between
Crystals of 14 of sufficient quality for crystallographic
samples, we conducted these experiments on a single sam- structure determination by X-ray diffraction could be ob-
ple, changing solvents between spectra by evaporation, and tained by crystallization from p-xylene (Figure 4). All mol-
we recorded spectra in Cl2DC–CDCl2 before and after ecules are equivalent and in meso (M,P) configuration.
those in the other solvents, which confirmed that the ratio They are arranged in loose stacks, with the chrysene units
in the same solvent is not history-dependent. This behavior of adjacent stacks interdigitated such that the densely
of 14 contrasts with the observation of a history-dependent packed chrysene blades lead to close π-orbital contact be-
behavior of 15: Here again, two complete sets of signals are tween molecules along the stacking direction as well as be-
observed, but the equilibration between the conformers is tween molecules along a direction perpendicular to the
not instantaneous upon dissolution at room temperature. stacks, via the connecting anthracene units that link two
On one occasion, we collected a small slowly formed second chrysene blades that are in contact with different neigh-
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H. Bock, S. Huet, P. Dechambenoit, E. A. Hillard, F. Durola
FULL PAPER
boring stacks. In the third dimension, these layers of bi-
dimensionally π-connected aromatic moieties are separated
by the peripheral alkyl substituents and p-xylene lattice sol-
vent molecules.
Figure 5. Absorption spectra (20 μm in CHCl3) of tetraesters 11
and 12 (dashed) and diimides 14 and 15 (continuous). Black curves:
11 and 14, gray curves: 12 and 15.
The anodic and cathodic electrochemistry of 11, 12, 14,
and 15 was evaluated by cyclic voltammetry (CV) and
differential pulse voltammetry (DPV) in dichloromethane
between +1.7 and –2.0 V vs. Ag/AgNO3. Both dinaphtho-
chrysenes 12 and 15 displayed reversible oxidation waves at
E1/2 = +1.11 V vs. the ferrocenium/ferrocene couple, with
no discernible influence of the nature of the substituents on
the oxidation potential. The dichrysenoanthracenes 11 and
14 show two oxidation waves, with little variation of the
potentials from 11 to 14 induced by the substituents. Ester
11 underwent a reversible oxidation with E1/2 = +0.92 V,
followed by a second irreversible oxidation with E1/2
=
+1.26 V. Both oxidation processes for the corresponding
imide 14 were irreversible (E1/2 = +0.97 and +1.21 V).
Scanning cathodically, both imides show two apparently
reversible reduction waves. In dinaphthochrysene 15, the re-
ductions are very close to one another, with E1/2 = –1.57
and –1.67 V, whereas the separation is better for dichry-
senoanthracene 14 at E1/2 = –1.37 and –1.64 V. The larger
peak separation, ΔE1/2, for 14 (240 mV from DPV) than in
15 (ΔE1/2 = 110 mV) suggests a better delocalization of the
radical in the one-electron reduced compound over the aro-
matic core in 14 than in 15. Reduction of the esters is con-
siderably more difficult than of the imides, with E1/2 = –1.82
for 11 and E1/2 = –2.04 for 12 (from DPV).
From the first reduction and oxidation potentials and
E1/2(Fc+/Fc) = –4.80 eV, lowest unoccupied molecular orb-
ital energies ELUMO of –2.98 (11), –2.76 (12), –3.43 (14),
and –3.23 (15) eV and highest occupied molecular orbital
energies EHOMO of –5.72 (11), –5.91 (12), –5.77 (14), and
–5.91 (15) eV are obtained, which yield electrochemical
band gaps of 2.74 (11), 3.15 (12), 2.34 (14), and 2.68 (15) eV.
These band gaps are slightly larger than the optical band
gaps inferred from the absorption spectra, implying exciton
binding energies of 0.26 to 0.34 eV.
Figure 4. Crystallographic structure of 14. Top, left: Single mol-
ecule of 14, thermal ellipsoids are depicted at the 50% level. Top,
right: View along the stacking direction showing the arrangement
in π-connected layers separated by alkyl regions. Lattice p-xylene
molecules are omitted for clarity. Bottom: Portion of the crystal
structure showing the packing of the diimide, forming layers by π-
stacking; close carbon–carbon contacts are depicted by green and
blue dashed lines, with C–C distances as short as ca. 3.286(4) and
3.387(4) Å (blue) and 3.399(4) Å (green); weak C–H···O hydrogen
bonds are also present with dC–O = 3.392(4) Å (orange dashed
lines). C black, H white, N blue, O red.
The absorption spectra of tetraesters 11 (yellow) and 12
(pale-yellow) and the diimides 14 (red) and 15 (orange) tes-
tify to the usual decrease in optical band gap from ester
to corresponding imide. The shifts of absorption edge (11:
500 nm/2.48 eV, 12: 440 nm/2.82 eV, 14: 620 nm/2.00 eV, 15:
530 nm/2.34 eV in dilute chloroform solution, Figure 5)
from 11 to 14 and from 12 to 15 are notably of identical
absolute energy value (–0.48 eV), corresponding to relative
reductions of the band gap energy by about one fifth and
one sixth, respectively. The proportionally greater band gap
reduction from 11 to 14 is in line with our previously re-
Conclusions
Polycyclic aromatic tetraalkyl esters and dialkylimides in-
ported findings that changes of the electron-withdrawing corporating two [5]helicene fragments are accessible from
substitution at central a,h-diannellated anthracene bridges chrysene in five or six steps through double Perkin reactions
are particularly influential on the band gap of polycyclic of chrysenylglyoxylic or chrysenylenediglyoxylic acids with
arenes.[1,6]
dibromophenylenediacetic or bromophenylacetic acids fol-
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From Chrysene to Double [5]Helicenes
146.1 g/mol, 78 mmol) was quickly added. After 15 min more at
–94 °C, the cooling bath was removed and stirring was continued
for 30 min at room temperature. CH2Cl2 (100 mL) was added, fol-
lowed by 1 m hydrochloric acid (50 mL), the phases were separated,
the aqueous phase was extracted with CH2Cl2 (2ϫ 50 mL), and
the combined organic phases were dried with sodium sulfate and
concentrated. Cold methanol (500 mL) was added while stirring,
and the precipitated product was filtered off and purified by col-
umn chromatography on silica (CH2Cl2) and recrystallized from
lowed by Pd-catalyzed dehydrobrominations. From the Pd-
catalyzed cyclization of doubly bromophenylmaleate-substi-
tuted chrysene, a rearranged side product could be isolated
in which one of the substituents has migrated to an adjacent
position on the chrysene core before cyclizing. The helicenic
aromatic environment leads to a remarkable diastereotopic
differentiation of the alkyl substituents in the NMR spectra
both in the esters and in the imides, and to the formation
of an equilibrium between M,P and M,M/P,P helix dia-
ethanol, yield 2.40 g (428.4 g/mol, 5.6 mmol, 75%); thin, yellow
1
stereomers of the imides in solution. The relative abun- needles; m.p. 187–189 °C. H NMR (400 MHz, CDCl3): δ = 9.19
(s, 2 H), 8.92 (dd, J = 8, 1 Hz, 2 H), 8.68 (dd, J = 8, 1 Hz, 2 H),
7.82 (dt, J = 1, 8 Hz, 2 H), 7.77 (dt, J = 1, 8 Hz, 2 H), 4.59 (q, J
= 7 Hz, 4 H), 1.51 (t, J = 7 Hz, 6 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 188.7, 164.1, 131.4, 131.1, 129.6, 129.1, 128.9, 128.8,
128.7, 126.5, 123.2, 63.1, 14.5 ppm. FD-HRMS: m/z calcd. for
C26H20O6 [M]+ 428.1260; found 428.1272.
dances of the diastereomers as detected by NMR spectro-
scopic analysis shift dynamically with solvent polarity at
room temperature in dichrysenoanthracene-diimide 14,
where the two helical moieties are more distant and inver-
sion of one helix can be assumed to only weakly effect the
other, whereas equilibration necessitates heating in dinaph-
thochrysene-diimide 15, where the two helices are more
closely intertwined and helix inversion can be supposed to
be more concerted and thus less free. The nonplanarity of
the bishelicenic esters and imides renders them soluble in
chlorinated solvents at room temperature even with rather
short alkyl substituents, and the combination of imide sub-
stituents with an extended, rather sextet-poor π-electron
system leads in 14 to a particularly broad absorption spec-
trum covering the visible wavelength region up to 620 nm,
Chrysenylene-6,12-diglyoxylic Acid (6): Diethyl chrysenylene-6,12-
diglyoxylate 5 (4.28 g, 428.4 g/mol, 10 mmol) was suspended in eth-
anol (200 mL), a solution of sodium hydrogen carbonate (20 g) in
water (400 mL) was added, and the mixture was stirred and heated
to reflux for 4 h. The resulting mostly homogeneous solution was
freed from a small quantity of insolubles by filtration and poured
into 2% aqueous hydrochloric acid (1 L). The gelatinous precipi-
tate was filtered off, washed with a small quantity of water and
allowed to dry in air. The orange solid product (4.17 g, quantitative
yield) was used without further purification, m.p. Ͼ 300 °C. 1H
associated with a small optical band gap of 2.00 eV. The NMR (400 MHz, [D6]DMSO): δ = 9.35 (s, 2 H), 8.96 (d, J = 8 Hz,
2 H), 8.71 (d, J = 8 Hz, 2 H), 7.95 (t, J = 8 Hz, 2 H), 7.89 (t, J
= 8 Hz, 2 H) ppm (no discrete acid proton detected). 13C NMR
(100 MHz, [D6]DMSO): δ = 191.5, 166.7, 131.5, 130.4, 128.7,
128.6, 128.3, 128.1, 127.1, 125.6, 123.5 ppm. FD-HRMS: m/z
calcd. for C22H12O6 [M]+ 372.0634; found 372.0644.
crystal packing of 14 is remarkable by its bidimensional dis-
tribution of π-contacts, which is made possible by the
twisted aromatic core; in contrast to many planar alkyl-
decorated large arenes that tend to form unidimensional π-
stacks surrounded by alkyl peripheries, 14 forms 2D layers
of closely packed arene moieties separated by layers of alkyl Tetrabutyl 2,5-Dibromo-1,4-phenylenebis[(6-chrysenyl)maleate] (9):
Chrysenyl-6-glyoxylic acid 3[5] (4.80 g, 300.3 g/mol, 16 mmol), 2,5-
chains. The combination of this exceptional bidimensional
electronic contact with acceptor-type behavior and moder-
ate band gap could be of interest for application in organic
dibromophenylene-1,4-diacetic acid 7[1] (2.64 g, 352.0 g/mol,
7.5 mmol), triethylamine (7.5 g, 101.2 g/mol, 74 mmol), and acetic
anhydride (10 g, 102.1 g/mol, 0.1 mol) were stirred in THF
electronics.
(150 mL) and heated to reflux under exclusion of moisture for 18 h.
Then 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 25 g, 152.2 g/mol,
0.16 mol), butanol (50 g, 74.1 g/mol, 0.67 mol), and 1-bromobutane
Experimental Section
(50 g, 137.0 g/mol, 0.36 mol) were added and heating to reflux was
6,12-Dibromochrysene (4):[7] Chrysene (1, 12.3 g, 228.3 g/mol,
continued for 2 h. Chloroform (500 mL) and 10% aqueous HCl
(300 mL) were added, the phases were separated, and the organic
phase was dried with sodium sulfate and concentrated. The residue
was purified by recrystallization from butanol, purified by column
chromatography on silica (CHCl3), and again recrystallized from
butanol, yield 5.93 g (1141.0 g/mol, 5.2 mmol, 69%); pale-yellow
solid; m.p. 173–177 °C. 1H NMR (400 MHz, CDCl3): δ = 8.80–
6.60 (several broad overlapping peaks, 24 H), 4.40–3.15 (3 broad
overlapping peaks, 8 H), 1.90–0.30 (several broad overlapping
peaks, 28 H) ppm. The strong signal broadening due to slow rota-
tions, evident from the 1H NMR spectrum, did not allow the re-
cording of a meaningful 13C NMR spectrum. FD-HRMS: m/z
calcd. for C66H60Br2O8 [M]+ 1140.2634; found 1140.2725.
54 mmol) was suspended in chloroform (300 mL), bromine
(5.8 mL, 3.1 g/mL, 18.0 g, 159.8 g/mol, 113 mmol) in chloroform
(100 mL) was added dropwise, and the heterogeneous mixture was
heated to reflux for 16 h. After cooling to room temperature, meth-
anol (300 mL) was added to complete the precipitation, the product
was filtered off, rinsed with methanol and recrystallized from tolu-
ene (1.5 L), yield 15.3 g (386.1 g/mol, 40 mmol, 74%); white need-
les; m.p. 275–282 °C (with simultaneous sublimation) [ref.[7] 260 °C
(dec.)]. 1H NMR (400 MHz, CDCl3): δ = 9.00 (s, 2 H), 8.71 (d,
7.5 Hz, 2 H), 8.43 (d, 7.5 Hz, 2 H), 7.78 (t, 7.5 Hz, 2 H), 7.75 (t,
7.5 Hz, 2 H) ppm.
Diethyl Chrysenylene-6,12-diglyoxylate (5): To a stirred suspension
of finely powdered 6,12-dibromochrysene 4 (3.00 g, 386.1 g/mol,
7.8 mmol) in anhydrous THF (250 mL) under argon, a solution
Tetrapropyl 6,12-Chrysenylenebis[(2-bromophenyl)maleate] (10):
Crude diacid 6 (4.17 g, 10 mmol), 2-bromophenylacetic acid 8
of butyllithium (2.5 m in hexane, 12.5 mL, 31.3 mmol) was added (5.38 g, 215.0 g/mol, 25 mmol), triethylamine (10 g, 101.2 g/mol,
dropwise at –94 °C (acetone–liquid nitrogen cooling bath), and the
mixture was stirred for 3 h under slow warming to room tempera-
ture. After 1 h more at room temperature, the mixture was cooled
again to –94 °C, and diethyl oxalate (10.6 mL, 1.077 g/mL, 11.4 g,
0.10 mol), and acetic anhydride (13 g, 102.1 g/mol, 0.13 mol) were
stirred in THF (150 mL) and heated to reflux under exclusion of
moisture for 18 h. Then 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU,
40 g, 152.2 g/mol, 0.26 mol), propanol (60 g, 60.1 g/mol, 1.0 mol),
Eur. J. Org. Chem. 2015, 1033–1039
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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H. Bock, S. Huet, P. Dechambenoit, E. A. Hillard, F. Durola
FULL PAPER
and 1-bromopropane (60 g, 123.0 g/mol, 0.5 mol) were added and
heating to reflux was continued for 2 h. CHCl3 (700 mL) and 10%
aqueous HCl (400 mL) were added, the phases were separated, and
the organic phase was dried with sodium sulfate and concentrated.
The viscous liquid residue crystallized slowly upon addition of
methanol while stirring. The solid product was filtered off and puri-
fied by column chromatography on silica (CHCl3) and another
crystallization was conducted by adding methanol while stirring to
the liquid, yield 6.61 g (934.7 g/mol, 7.1 mmol, 71%); off-white so-
tains small inseparable amounts of presumably the doubly re-
arranged isomer.
Compound 12: Semiamorphous solid without a clear melting point.
1H NMR (400 MHz, CD2Cl2): δ = 8.58 (d, J = 8 Hz, 2 H), 8.17
(d, J = 8 Hz, 2 H), 8.08 (d, J = 8 Hz, 2 H), 7.87 (d, J = 8 Hz, 2
H), 7.63 (t, J = 8 Hz, 2 H),7.42 (t, J = 8 Hz, 2 H), 7.39 (t, J =
8 Hz, 2 H), 7.25 (t, J = 8 Hz, 2 H), 4.57 (dt, J = 11, 7 Hz, 2 H),
4.51 (dt, J = 11, 7 Hz, 2 H), 3.39 (dt, J = 11, 7 Hz, 2 H), 3.25 (dt,
J = 11, 7 Hz, 2 H), 1.87 (sext, J = 7 Hz, 4 H), 1.78 (sext, J = 7 Hz,
4 H), 1.06 (t, J = 7 Hz, 6 H), 0.92 (t, J = 7 Hz, 6 H) ppm. 13C
NMR (100 MHz, CD2Cl2): δ = 170.6, 168.9, 133.5, 133.2, 131.2,
130.8, 130.7, 129.2, 128.7, 128.4, 128.1, 127.7, 127.54, 127.52,
127.45, 127.3, 126.5, 126.3, 68.60, 68.58, 22.6, 22.2, 10.9, 10.7 ppm.
FD-HRMS: m/z calcd. for C50H44O8 [M]+ 772.3036; found
772.3029.
1
lid; m.p. 225–229 °C. H NMR (400 MHz, CDCl3): δ = 8.65–8.47
(broad, 4 H), 8.24 (d, J = 8 Hz, 2 H), 7.80–7.50 (broad, 4 H), 7.45–
7.28 (broad, 2 H), 7.05–6.87 (broad, 2 H), 6.87–6.72 (m, 4 H), 4.21
(t, J = 7 Hz, 4 H), 4.25–4.07 (broad, 4 H), 1.68 (sext, J = 7 Hz, 4
H), 1.70–1.50 (2 broad overlapping peaks, 4 H), 0.88 (t, J = 7 Hz,
6 H), 0.87–0.67 (2 broad overlapping peaks) ppm. The strong signal
broadening due to slow rotations, evident from the 1H NMR spec-
trum, did not allow the recording of a meaningful 13C NMR spec-
trum. FD-HRMS: m/z calcd. for C50H46Br2O8 [M]+ 934.1539;
found 934.1537.
Compound 13: Semiamorphous solid without a clear melting point.
1H NMR (400 MHz, CD2Cl2): δ = 9.24 (d, J = 8 Hz, 1 H), 8.76
(d, J = 8 Hz, 1 H), 8.65 (d, J = 8 Hz, 1 H), 8.21 (d, J = 8 Hz, 1
H), 8.14 (d, J = 8 Hz, 2 H), 8.07 (d, J = 8 Hz, 1 H), 7.91 (d, J =
8 Hz, 1 H), 7.88 (t, J = 8 Hz, 1 H), 7.79 (t, J = 8 Hz, 1 H), 7.63 (t,
J = 8 Hz, 1 H), 7.51 (t, J = 8 Hz, 1 H), 7.49 (t, J = 8 Hz, 1 H),
7.46 (t, J = 8 Hz, 1 H), 7.43 (t, J = 8 Hz, 1 H), 7.31 (t, J = 8 Hz,
1 H), 4.54 (dt, J = 11, 7 Hz, 1 H), 4.49–4.35 (m, 3 H), 4.31 (dt, J
= 11, 7 Hz, 1 H), 4.25 (dt, J = 11, 7 Hz, 1 H), 3.70 (dt, J = 11,
7 Hz, 1 H), 3.21 (dt, J = 11, 7 Hz, 1 H), 1.87 (sext, J = 7 Hz, 2 H),
1.77 (sext, J = 7 Hz, 2 H), 1.70 (sext, J = 7 Hz, 2 H), 1.12 (sext, J
= 7 Hz, 2 H), 1.06 (t, J = 7 Hz, 3 H), 0.96 (t, J = 7 Hz, 3 H), 0.89
(t, J = 7 Hz, 3 H), 0.44 (t, J = 7 Hz, 3 H) ppm. 13C NMR
(100 MHz, CD2Cl2): δ = 170.9, 169.2, 169.0, 168.8, 134.8, 134.0,
133.3, 133.0, 132.8, 131.3, 131.0, 130.9, 130.8, 130.1, 129.6, 129.3,
129.2, 129.1, 128.5, 128.3, 128.24, 128.19, 128.02, 127.99, 127.95,
127.86, 127.7, 127.6, 127.51, 127.45, 127.39, 127.0, 126.7, 126.3,
126.2, 123.6, 68.57, 68.53, 68.46, 67.8, 22.6, 22.4, 22.2, 21.8, 10.91,
10.89, 10.83, 10.2 ppm. FD-HRMS: m/z calcd. for C50H44O8 [M]+
772.3036; found 772.3040.
Tetrabutyl Dichryseno[7,6-a;7,6-h]anthracene-7,8,20,21-tetracarb-
oxylate (11): Tetrabutyl 2,5-dibromo-1,4-phenylenebis[(6-chrysenyl)-
maleate] 9 (1.14 g, 1141.0 g/mol, 1 mmol), palladium(II) acetate
(0.09 g, 224.5 g/mol, 0.4 mmol), tricyclohexylphosphine (0.20 g,
280.4 g/mol, 0.7 mmol), and potassium carbonate (1.38 g, 138.2 g/
mol, 10 mmol) were stirred in dimethylacetamide (DMA, 20 mL)
under argon at 110 °C for 16 h. CHCl3 (100 mL) was added, the
solids were filtered off, the solvents were evaporated (rotary evapo-
rator with boiling water bath, 12 mbar), and the residue was puri-
fied by column chromatography on silica (CHCl3) and threefold
recrystallization from butanol, yield 0.51 g (979.2 g/mol,
0.52 mmol, 52%); yellow, semiamorphous solid without clear melt-
1
ing-point. H NMR (400 MHz, CDCl3): δ = 9.08 (s, 2 H), 8.77 (d,
J = 9 Hz, 2 H), 8.76 (d, J = 8 Hz, 2 H), 8.43 (d, J = 8 Hz, 2 H),
8.19 (d, J = 9 Hz, 2 H), 8.05 (d, J = 8 Hz, 2 H), 8.04 (d, J = 8 Hz,
2 H), 7.65 (t, J = 8 Hz, 2 H), 7.59 (t, J = 8 Hz, 2 H), 7.53 (t, J =
8 Hz, 2 H), 7.36 (t, J = 8 Hz, 2 H), 4.36 (dt, J = 11, 7 Hz, 2 H),
4.21 (dt, J = 11, 7 Hz, 2 H), 3.89 (dt, J = 11, 7 Hz, 2 H), 3.74 (dt,
J = 11, 7 Hz, 2 H), 1.62–1.52 (m, 4 H), 1.47–1.37 (m, 4 H), 1.36–
1.14 (m, 8 H), 0.89 (t, J = 7 Hz, 6 H), 0.79 (t, J = 7 Hz, 6 H) ppm.
13C NMR (100 MHz, [D6]DMSO): δ = 169.6, 167.8, 133.1, 132.0,
131.2, 130.7, 129.94, 129.90, 129.8, 129.6, 129.4, 128.3, 128.0,
127.6, 127.24, 127.19, 126.8, 126.7, 126.3, 125.7, 125.0, 124.7,
123.9, 120.9, 66.5, 66.3, 30.4, 30.3, 19.3, 19.2, 14.0, 13.8 ppm. FD-
HRMS: m/z calcd. for C66H58O8 [M]+ 978.4132; found 978.4137.
N,NЈ-Bis(1-pentylhexyl) Dichryseno[7,6-a;7,6-h]anthracene-7,8:20,21-
tetracarboxdiimide (14): Tetraester 11 (143 mg, 979.2 g/mol,
0.15 mmol), 6-aminoundecane (0.3 g, 171.3 g/mol, 1.75 mmol),
imidazole (4 g), and o-dichlorobenzene (6 g) were stirred and
heated to reflux under argon for 16 h. The mixture was dissolved
in CHCl3, washed with 5% aqueous hydrochloric acid, and concen-
trated. The product was precipitated by adding methanol, filtered
off, and purified by column chromatography on silica (CHCl3) and
recrystallized from p-xylene, whereby crystals suitable for X-ray
crystallographic structure determination were obtained, yield
111 mg (1025.3 g/mol, 0.11 mmol, 74%); red crystals; m.p.
Ͼ 300 °C. 1H NMR [400 MHz, (CDCl2)2, mixture of two conform-
Tetrapropyl
Dinaphtho[1,2-g;1,2-p]chrysene-9,10,19,20-tetracarb-
oxylate (12) and Tetrapropyl Dinaphtho[2,1-g;1,2-p]chrysene-
5,6,11,12-tetracarboxylate (13): Tetrapropyl 6,12-chrysenyl-
enebis[(2-bromophenyl)maleate] 10 (1.87 g, 934.7 g/mol, 2 mmol), ers of approximately equal abundance, 1 H = one H in one of the
palladium(II) acetate (0.18 g, 224.5 g/mol, 0.8 mmol), tricyclohex-
ylphosphine (0.40 g, 280.4 g/mol, 1.4 mmol), and potassium carb-
onate (2.76 g, 138.2 g/mol, 20 mmol) were stirred in dimethylacet-
conformers]: δ = 9.97 (s, 2 H), 9.92 (s, 2 H), 9.22 (d, J = 8 Hz, 2
H), 9.05 (d, J = 8 Hz, 2 H), 8.88–8.80 (m, 8 H), 8.36 (d, J = 9 Hz,
2 H), 8.32 (d, J = 9 Hz, 2 H), 8.21 (d, J = 9 Hz, 2 H), 8.17 (d, J =
amide (DMA, 40 mL) under argon at 110 °C for 16 h. CHCl3 8 Hz, 2 H), 8.09 (d, J = 8 Hz, 2 H), 7.88–7.78 (m, 8 H), 7.73 (t, J
(200 mL) was added, the solids were filtered off, the solvents were = 8 Hz, 2 H), 7.57 (t, J = 8 Hz, 2 H), 7.46 (t, J = 8 Hz, 2 H), 7.28
evaporated (rotary evaporator with boiling water bath, 12 mbar), (t, J = 8 Hz, 2 H), 7.04 (t, J = 8 Hz, 2 H), 4.19 (broad, 4 H), 2.04
and the residue was purified by column chromatography on silica
(CHCl3). The main product 12 was recrystallized from butanol,
yield 524 mg (772.9 g/mol, 0.68 mmol, 34%) as a pale-yellow solid.
The slightly more polar secondary product 13 formed a gel when
a hot butanol solution of the compound was cooled to room tem-
perature or below, but could nevertheless be separated from the
butanol by vacuum filtration followed by drying in vacuo, yield
182 mg (772.9 g/mol, 0.24 mmol, 12%); pale-yellow solid that con-
(broad, 8 H), 1.70 (broad, 8 H), 1.30 (broad, 48 H), 0.88 (m, 24
H) ppm. 13C NMR (100 MHz, CDCl3, mixture of two conformers):
δ = 169.94, 169.90, 168.8, 168.7, 134.0, 133.7, 133.3, 133.1, 132.7,
132.1, 131.5, 131.42, 131.36, 131.25, 131.0, 130.9, 130.8, 130.3,
130.2, 129.7, 129.2, 129.1, 128.9, 128.8, 128.7, 128.6, 128.2, 128.0,
127.4, 127.3, 127.2, 126.8, 126.5, 126.3, 125.73, 125.68, 125.57,
125.4, 123.7, 123.5, 123.4, 123.1, 120.6, 120.5, 52.8, 52.7, 32.9, 32.8,
32.7, 32.5, 31.9, 31.8, 31.72, 31.68, 26.7, 26.6, 26.5, 22.84, 22.78,
1038
www.eurjoc.org
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 1033–1039

From Chrysene to Double [5]Helicenes
22.72, 14.3 ppm. FD-HRMS: m/z calcd. for C72H68N2O4 [M]+
1024.5179; found 1024.5195.
01) and Coordenação de Aperfeiçoamento de Pessoal de Nível
Superior–Comité Français d’Evaluation de la Coopération Uni-
versitaire et Scientifique avec le Brésil (CAPES-COFECUB) (pro-
ject number Ph-C 803-14) grants.
N,NЈ-Bis(1-pentylhexyl) Dinaphtho[1,2-g;1,2-p]chrysene-9,10:19,20-
tetracarboxdiimide (15): Tetraester 12 (428 mg, 772.9 g/mol,
0.55 mmol), 6-aminoundecane (0.65 g, 171.3 g/mol, 3.8 mmol),
imidazole (6 g), and o-dichlorobenzene (9 g) were stirred and
heated to reflux under argon for 16 h. The mixture was dissolved
in CHCl3, washed with 5% aqueous hydrochloric acid, and concen-
trated. The product was precipitated by adding methanol, filtered
off, and purified by column chromatography on silica (CHCl3) and
recrystallized from a 1:3 mixture of butanol and ethanol, yield
295 mg (875.1 g/mol, 0.34 mmol, 61%); orange semiamorphous so-
lid without a clear melting point. 1H NMR [400 MHz, (CDCl2)2,
main conformer]: δ = 9.39 (d, J = 8 Hz, 2 H), 9.05 (d, J = 8 Hz, 2
H), 8.68 (d, J = 8 Hz, 2 H), 7.82 (d, J = 8 Hz, 2 H), 7.77 (t, J =
8 Hz, 2 H), 7.55 (t, J = 8 Hz, 2 H), 7.53 (t, J = 8 Hz, 2 H), 7.38 (t,
J = 8 Hz, 2 H), 4.39 (tt, J = 10, 5 Hz, 2 H), 2.21 (broad, 4 H), 1.85
(broad, 4 H), 1.34 (broad, 24 h), 0.89 (m, 12 H) ppm. 13C NMR
(100 MHz, CDCl3, main conformer): δ = 170.0, 169.8, 133.8, 133.3,
131.3, 130.81, 130.77, 130.6, 129.7, 129.1, 128.5, 128.3, 127.8,
127.5, 127.0, 126.8, 126.4, 126.1, 125.6, 53.0, 33.0, 32.8, 31.9, 31.8,
26.83, 26.77, 22.82, 22.76, 14.28, 14.25 ppm. FD-HRMS: m/z
calcd. for C60H62N2O4 [M]+ 874.4710; found 874.4721.
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2015, 1028–1032, preceding article.
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[9] We address compounds 12, 13, and 15 as dinaphthochrysenes
purely because this reflects the synthetic approach. Com-
pounds 12 and 15 may also be considered chrysenochrysenes,
and 13 may be regarded as a tribenzopicene.
[10] M. A. Campo, H. Zhang, T. Yao, A. Ibdah, R. D. McCulla,
Q. Huang, J. Zhao, W. S. Jenks, R. C. Larock, J. Am. Chem.
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Supporting Information (see footnote on the first page of this arti-
cle): Crystallographic data of 14, electrochemical data, 1H and
13C NMR spectra.
Acknowledgments
The authors are grateful to Marli Ferreira for assistance in the
synthesis of compound 11. This research was financed partially by
Agence Nationale de la Recherche (ANR) (project 13-JS07-0009-
Received: October 13, 2014
Published Online: December 22, 2014
Eur. J. Org. Chem. 2015, 1033–1039
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1039