Unconventional Transformation of the Two Carbonyl Groups in 4,4′,5,5′-Tetrachloro-10 H,10′ H-[9,9′-bianthracenylidene]-10,10′-dione into Diallenes

Article abstract of DOI:10.1021/acs.orglett.0c03233

The diallene-containing compound dACl-1 was unexpectedly obtained by the unconventional transformation of two carbonyl groups in 4,4′,5,5′-tetrachloro-10H,10′H-[9,9′-bianthracenylidene]-10,10′-dione into diallenes. In addition, the two 1-triisopropylsilyl

Full text of DOI:10.1021/acs.orglett.0c03233

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Letter
Unconventional Transformation of the Two Carbonyl Groups in
4,4′,5,5′-Tetrachloro-10H,10′H‑[9,9′-bianthracenylidene]-10,10′-
dione into Diallenes
Liangliang Chen, Mingxu Du, Jianwu Tian, Wenlin Jiang, Zitong Liu,* Xisha Zhang, Guanxin Zhang,
and Deqing Zhang*
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ABSTRACT: The diallene-containing compound dACl-1 was
unexpectedly obtained by the unconventional transformation of
two carbonyl groups in 4,4′,5,5′-tetrachloro-10H,10′H-[9,9′-
bianthracenylidene]-10,10′-dione into diallenes. In addition, the
two 1-triisopropylsilyl (TIPS) groups in dACl-1 were easily
removed to yield dACl-2. The reaction mechanism was
investigated and is discussed. Moreover, both compounds are
stable under ambient conditions, and, in particular, dACl-1 is
thermally stable at 315 °C.
t was reported that the carbonyl groups in pentacene-6,13-
dione and its analogues can react with ethynyltriisopro-
pylsilane in the presence of n-butyl lithium, followed by
aromatization after the addition of SnCl2 or H3PO2,1 to form
triisopropylsilyl (TIPS)-pentacene and its derivatives (Scheme
1), which show outstanding semiconducting performances.2
transformation of the two carbonyl groups in 4,4′,5,5′-
tetrachloro-10H,10′H-[9,9′-bianthracenylidene]-10,10′-dione
(1), yielding the structurally twisting compound dACl-1 with
diallenes. (See Scheme 2.) In fact, as a unique kind of
hydrocarbon, allene contains two vertical cumulative double
bonds4 and thus is different from other aromatic hydrocarbons
with alternating single−double or single−triple bond struc-
tures.3,5 In recent years, allenes have been utilized as building
blocks for light-emitting materials.6
As shown in Scheme 2, we investigated the reaction of 1
with ethynyltriisopropylsilane in the presence of n-butyl
lithium, followed by treatment with SnCl2/HCl in the same
way as for pentacene-6,13-dione (the precursor compound for
TIPS-pentacene).1 Compound 1 was synthesized in two steps
from 1,8-dichloroanthrone (See Scheme S1) according to the
reported method.7 The reaction led to not only dACl-yne
(Scheme 2) in 21% yield as the expected product but also the
diallene compound dACl-1 in 16% yield. The molar ratio
between dACl-yne and dACl-1 was 1.32:1. Alternatively, the
reaction of 1 with ethynyltriisopropylsilane and n-butyl lithium,
followed by the addition of HCl (10%) afforded compound 2
in 49% yield. (See Scheme 3.) The further reaction of 2 with
SnCl2 and HCl (10%) yielded dACl-yne and dACl-1 in 33 and
20% yield, respectively. Under this condition, the molar ratio
I
Scheme 1. Chemical Structures of TIPS-Pentacene and
TIPS-Cl-PAH and the Conventional Synthetic Route to
TIPS-Pentacene
Consequently, more expanded polycyclic aromatic hydro-
carbons (PAHs) with 1-TIPS-acetylene groups, which endow
the good solubilities of PAHs in organic solvents, have been
synthesized and investigated.3 In our project, we aimed to
synthesize PAHs such as TIPS-Cl-PAH in Scheme 1 with 1-
TIPS-acetylene groups and electron-withdrawing −Cl groups
for the development of new semiconductors. During the
studies, we unexpectedly discovered the unconventional
Received: September 26, 2020
https://dx.doi.org/10.1021/acs.orglett.0c03233
© XXXX American Chemical Society
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Scheme 2. Synthesis of dACl-1 and dACl-2
Figure 1. Molecular structures of dACl-1 (a) and dACl-2 (b).
Displacement ellipsoids are drawn at the 50% probability level.
Scheme 3. Control Reactions with Compounds 1, 3, dACl-1,
and dACl-yne for the Mechanism Investigation
twisting conformation with a central symmetry. The bulky-
TIPS groups are positioned in the trans conformation. The
bond lengths of cumulative double bonds of C1−C2 and C2−
C3 are 1.297 and 1.317 Å, respectively, which are comparable
to those previously reported.4,8 Additionally, the lengths of
other carbon−carbon bonds of the two central six-membered
rings show alternating character.
The two TIPS groups in dACl-1 were removed to yield
dACl-2 in 71% yield after the reaction with tetra-n-
butylammonium fluoride (TBAF), as shown in Scheme 2.
1
The chemical structure of dACl-2 was characterized with H
NMR, 13C NMR, and high-resolution mass spectrometry
(HRMS) as well as elemental analysis. (See the Supporting
Information.) We also determined the crystal structure of
dACl-2. As shown in Figure 1 and Figure S3, dACl-2 is not
planar, although the bulky-TIPS groups are removed. This is
because of the steric hindrances due to the neighboring
benzene rings. As listed in Table S2, the bond lengths of
cumulative double bonds (C13−C15 and C15−C16) are
similar to those of dACl-1.
It is noted that both dACl-1 and dACl-2 are stable under
ambient conditions for at least 200 days. On the basis of the
thermogravimetric analysis data (Figure S4), the thermal
decomposition occurs at 315 and 141 °C for dACl-1 and
dACl-2, respectively. The differential scanning calorimetry
curves show no thermal transitions for both compounds
(Figure S4). Thus dACl-1 and dACl-2 are thermally stable
below 315 and 141 °C, respectively. Clearly, dACl-1 is more
thermally stable.
To investigate the reaction mechanism for the trans-
formation of carbonyl groups in 1 into the diallenes, we
performed the reaction of 10H,10′H-[9,9′-bianthracenyli-
dene]-10,10′-dione (3), which is structurally analogous to 1
but without −Cl groups, with ethynyltriisopropylsilane, n-butyl
lithium, and SnCl2/HCl in the same way as for 1 (Scheme 3).
Only dA-yne was obtained, but the formation of the
corresponding diallenes dA-1 was not detected. This control
experiment indicates that the four −Cl groups in 1 play a
crucial role in ushering the formation of the diallenes dACl-1.
Furthermore, dACl-1 and dACl-yne cannot be interconverted
between dACl-yne and dACl-1 was slightly enhanced to
1.63:1.
1
dACl-1 was characterized with H NMR, 13C NMR, and
high-resolution mass spectrometry (HRMS) as well as
elemental analysis. (See the Supporting Information.) These
NMR and HRMS data are in agreement with the structure of
dACl-1. Moreover, crystals of dACl-1 suitable for single-crystal
structural analysis were successfully obtained by slowly
diffusing methanol into the chloroform solution. Thus the
structure of dACl-1 was further confirmed by the crystal
structural analysis. (See the Supporting Information.) Figure 1
and Figure S2 show the molecular structure of dACl-1, and the
bond lengths are listed in Table S1. Obviously, dACl-1 shows a
B
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by separately treating with SnCl2 and HCl (10%) for >100 h.
Thus the possibility that one product (either dACl-1 or dACl-
yne) was first generated and another product (dACl-yne or
dACl-1) was transformed from it can be excluded. Moreover,
compounds 2 and 4 (see Scheme 3) with two hydroxyl and
alkynyl groups were separated after the respective reaction of 1
and 3 with n-butyl lithium and ethynyltriisopropylsilane.
Whereas the treatment of 4 with SnCl2 and HCl (10%)
yielded only dA-yne in 87% yield (see Scheme 3), the further
reaction of 2 with SnCl2 and HCl (10%) afforded both dACl-
yne and dACl-1 in 33 and 20% yield, respectively.
Consequently, it can be concluded that dACl-yne and dACl-
1 should be simultaneously formed from 2 with different
reaction mechanisms under the same reaction conditions.
On the basis of the fact that the −Cl groups in 2 promote
the formation of the diallenes dACl-1, we proposed the
reaction mechanism, as depicted in Scheme 4. First, the
pentyl-containing diallenes were successfully obtained in 11,
13, and 9% yield, respectively, under the same conditions as for
ethynyltriisopropylsilane. Similarly, the corresponding diyne
compounds were also simultaneously obtained. However, the
reactions with either ethynylbenzene or 1-ethynyl-4-fluoro-
benzene yielded only the respective diyne compounds.
Alternatively, we found that the reaction yield of dACl-1
increased to 23% when the reaction mixture of 1 and
ethynyltriisopropylsilane in the presence of n-butyl lithium
was treated with NaH2PO2·H2O/NaI/acetic acid (Scheme S3)
instead of SnCl2/HCl.1b,3a
The solutions of both dACl-1 and dACl-2 show absorptions
at 296/352 and 285/337 nm in the UV region. (See Figure 2.)
Scheme 4. Proposed Mechanism for the Formation of Di-
allenes dACl-1
coordination of hydroxyl groups of tertiary propargylic alcohols
in 2 with SnCl2 to form a complex 59 makes the tin complexes
negative and nucleophilic. Then, the electron-rich tin
complexes can react with the alkynyl carbon atoms (close to
−TIPS groups), which become more electrophilic owing to the
presence of the electron-withdrawing −Cl groups in the
neighbors. Consequently, propargylic groups were isomerized
to allenes,10 followed by the presence of HCl, yielding the
diallenes dACl-1.
Additionally, short interatomic contacts O···H (2.159 Å)
and O···Cl (2.837 and 2.909 Å) were observed in compound 2
(Figure S5). It is noted that similar weak noncovalent
interactions of O···Cl were previously reported.11 Such weak
interactions may stabilize the intermediate complex 5 (see
Scheme 4), which may promote the reaction of tin atoms with
the alkynyl carbon atoms to form diallenes dACl-1. The
alternative reaction pathway is the direct elimination of
dichloro(hydroxy)tin(IV) groups in 5, leading to dACl-yne,
as previously reported.12
Figure 2. UV−vis absorption and fluorescence spectra of dACl-1 (a)
and dACl-2 (b) in solutions (10−5 M in CHCl3) and solid states.
This is consistent with the fact that molecules of both dACl-1
and dACl-2 are rather twisting. As depicted in Figure S6, the
central six-membered rings that are linked to the diallenes are
not planar, and the two benzene rings (fused with the central
six-membered rings) with −Cl groups form dihedral angles of
130.8 and 133.7°, respectively, for dACl-1 and dACl-2.
Therefore, the π-electrons are not well conjugated. In the
solid states, the absorptions of dACl-1 and dACl-2 are slightly
red-shifted to 302/364 and 298/356 nm, respectively. This
agrees with the observation that there are no intermolecular
π−π interactions within the crystal lattices of dACl-1 and
dACl-2. (See Figure S7.) However, short interatomic contacts,
C−H···Cl (2.807 and 2.904 Å) and TIPS-H···H-TIPS (2.337
Å) for dACl-1 and Cl···Cl (3.426 Å), allene H···H (2.069 Å),
and phenyl H···H (2.258 Å) for dACl-2, are present in their
crystal lattices. On the basis of the onset absorptions of their
solids, the optical band gaps of dACl-1 and dACl-2 were
estimated to be 2.88 and 2.91 eV, respectively. As shown in
Figure 2, dACl-1 and dACl-2 are emissive in solutions and
solid states. The solution of dACl-1 shows emission at 436 nm
We further investigated other monosubstituted acetylenes,
such as ethynyltrimethylsilane, ethynyltriethylsilane, hept-1-
yne, ethynylbenzene, and 1-ethynyl-4-fluorobenzene, to expand
the reaction scope. As shown in Scheme S2, trimethylsilane-
containing diallenes, triethylsilane-containing diallenes, and
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with a quantum yield of 18.4%, whereas the emission emerges
at 448/477 nm for the solid sample of dACl-1 with a quantum
yield of 11.1%. In comparison, dACl-2 show emissions at 430
and 490 nm, respectively, in solution and solid state, with the
respective emission quantum yields of 10.5 and 13.2%.
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China; University of
Chinese Academy of Sciences, Beijing 100049, P. R. China
Mingxu Du − Beijing National Laboratory for Molecular
Sciences, CAS Key Laboratory of Organic Solids, CAS Center of
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China
We report the unconventional transformation of two
carbonyl groups in 4,4′,5,5′-tetrachloro-10H,10′H-[9,9′-bian-
thracenylidene]-10,10′-dione into diallenes, yielding dACl-1
with diallenes apart from the expected product dACl-yne with
two triisopropylsilylethynyl groups after the reaction with
ethynyltriisopropylsilane in the presence of n-butyl lithium,
followed by treatment with SnCl2/HCl. Interestingly, the bulky
triisopropylsilyl groups in dACl-1 can be removed to form
dACl-2. The structures of both dACl-1 and dACl-2 are
confirmed by single-crystal structural analysis. The control
experimental results reveal that the −Cl groups in 1 promote
the transformation of the carbonyl groups into the diallenes.
Moreover, the mechanism for the formation of dACl-1 was
proposed. Both dACl-1 and dACl-2 are stable under ambient
conditions, and, in particular, dACl-1 is thermally stable at 315
°C. Although molecules of dACl-1 and dACl-2 are rather
twisting, they are emissive in solutions and solid states. Thus
they are potentially useful as light-emitting materials for
organic light-emitting diodes and fluorescence probes.
Jianwu Tian − Beijing National Laboratory for Molecular
Sciences, CAS Key Laboratory of Organic Solids, CAS Center of
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China; University of
Chinese Academy of Sciences, Beijing 100049, P. R. China
Wenlin Jiang − Beijing National Laboratory for Molecular
Sciences, CAS Key Laboratory of Organic Solids, CAS Center of
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China; University of
Chinese Academy of Sciences, Beijing 100049, P. R. China
Xisha Zhang − Beijing National Laboratory for Molecular
Sciences, CAS Key Laboratory of Organic Solids, CAS Center of
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China; University of
Chinese Academy of Sciences, Beijing 100049, P. R. China
Guanxin Zhang − Beijing National Laboratory for Molecular
Sciences, CAS Key Laboratory of Organic Solids, CAS Center of
Excellence in Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, P. R. China;
ASSOCIATED CONTENT
* Supporting Information
■
orcid.org/0000-0002-1417-6985
sı
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c03233
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c03233.
Materials and characterization techniques, synthesis and
characterizations of correlated compounds, X-ray
analysis data for dACl-1 and dACl-2, TGA and DSC,
Author Contributions
The manuscript was written through contributions of all
authors.
1
and H NMR and 13C NMR spectra (PDF)
Notes
Accession Codes
The authors declare no competing financial interest.
CCDC 1992164, 1992167, 1997017, and 2031825 contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.
uk, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
1223 336033.
ACKNOWLEDGMENTS
■
We acknowledge the financial support of the National Key
R & D P r o g ra m o f C h i na ( 2 0 18 Y F E 0 20 0 70 0 ,
2017YFA0204701) and the NSFC (21661132006, 21790360,
61890943).
AUTHOR INFORMATION
Corresponding Authors
REFERENCES
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