Aerobic oxidation of 9H-fluorenes to 9-fluorenones using mono-/multilayer graphene-supported alkaline catalyst

Article abstract of DOI:10.1002/cplu.201300123

The synthesis of 9-fluorenone derivatives has been achieved in high yield and with high purity by aerobic oxidation of 9H-fluorenes at room temperature in the presence of a graphene-supported KOH composite that acts as a catalyst in N,N-dimethylformamide. The new protocol involves very simple work-up procedures, and the solvent and the catalyst can be recycled and reused. A scaled-up preparative study employing this method was also conducted and showed its advantages of being both cost-effective and environmentally friendly, and has potential for application in industrial processes. Copyright

Full text of DOI:10.1002/cplu.201300123

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DOI: 10.1002/cplu.201300123
Aerobic Oxidation of 9H-Fluorenes to 9-Fluorenones using
Mono-/Multilayer Graphene-Supported Alkaline Catalyst
Xin Zhang,[a, b] Xuan Ji,[a] Ruifei Su,[a] Brandon L. Weeks,[b] Zhao Zhang,[a] and Songlu Deng*[c]
The synthesis of 9-fluorenone derivatives has been achieved in
high yield and with high purity by aerobic oxidation of 9H-flu-
orenes at room temperature in the presence of a graphene-
supported KOH composite that acts as a catalyst in N,N-dime-
thylformamide. The new protocol involves very simple work-up
procedures, and the solvent and the catalyst can be recycled
and reused. A scaled-up preparative study employing this
method was also conducted and showed its advantages of
being both cost-effective and environmentally friendly, and has
potential for application in industrial processes.
Introduction
The use of 9-fluorenones have applications in materials
chemistry, ranging from optical materials,[1] organic dyes,[2]
plastic additives, biomedical materials,[3] organic light emitting
materials (OLEDs),[4] and organic solar cell materials.[5] At pres-
ent, the catalytic oxidation of 9H-fluorenes is a widespread
method to produce 9-fluorenones. However, currently devel-
oped approaches require high temperature and noble-metal
catalysts in gas-phase reactions,[6] or use high-valence metal
compounds such as CrO3 and KMnO4 and strong organic oxi-
dants such as tBuOOH in liquid-phase reactions,[7] which limit
their applications in some areas such as the pharmaceutical
and biomedical fields because of toxicity concerns and separa-
tion challenges.[8] These methods are often not considered
“green” when scaled up into large scale production. Increasing
environmental awareness and economic concerns have led to
a continuous interest in developing simple and practical oxida-
tion methods that would produce desirable 9-fluorenones in
high yields.
some weakly polar substrates, such as 9H-fluorene and alkyl
9H-fluorenes, as a result of the poor dispersion of KOH in THF.
This drawback would not be ideal for the scaled-up production
of some 9-fluorenone compounds. Therefore, it is crucial to de-
velop a system with good dispersion of the alkaline catalyst for
the liquid-phase oxidation of 9H-fluorenes into 9-fluorenoenes.
Graphene, a two-dimensional (2D) structure of sp2-bonded
carbon atoms, has been widely applied in organic synthesis,
materials chemistry, and biomedicine because of its high
electric and thermal conductivities, great mechanical strength,
peculiar optical properties, and huge surface area
(ꢀ2600 m2 gÀ1).[9] Graphene has also been shown to aid in the
dispersion of catalysts in reaction systems by forming nanopar-
ticles on the graphene surfaces.[10–17] For example, graphene-
supported Pd nanoparticles showed higher activity for the
Suzuki reaction compared with conventional Pd catalysts.[11]
Graphene decorated with PtAu alloy nanoparticles had higher
electrocatalytic activity and stability than other analogous cata-
lysts such as PtAu/CB and Etek-Pt/C for formic acid oxida-
tion.[12] The AuPd bimetallic nanoparticles combined with gra-
phene indicated a superior catalytic activity in 1,3,5-triisopro-
pylbenzene (TMB) oxidation in comparison to the monometal-
lic counterparts.[13] The graphene-supported Pt nanoparticles
or Pt-on-Pd bimetallic nanodendrites could enhance the elec-
trocatalytic activity of Pt or Pd in methanol oxidation reac-
tions.[14] Hierarchically ordered macro-/mesoporous TiO2-gra-
phene composite films displayed significant enhancement of
photocatalytic activity for degrading the methylene blue com-
pared with pure mesoporous titania films.[15] Graphene-sup-
ported ruthenium- or rhodium-containing nanoparticles indi-
cated the highly catalytic activity for the hydrogenation of cy-
clohexene and benzene under organic-solvent-free condi-
tions.[16] The composites of Au, Ag–TiO2, or Pt–TiO2 with gra-
phene exhibited higher efficient catalytic activity for the
reduction of nitro compounds to amino compounds by NaBH4
than the corresponding Au, Ag, or Pt nanoparticles.[17]
Recently, a green and highly-efficient technique to synthe-
size 9-fluorenones from 9H-fluorenes has been observed
through aerobic oxidation in the presence of KOH in tetrahy-
drofuran (THF).[8] This protocol was performed under mild con-
ditions and a simple workup procedures with high yields and
purity. In addition, successful scale-up synthesis of 2,7-dibrom-
fluorenone from 2,7-dibromfluorene was performed on
a 5.0 kg scale. However, the method required a relatively large
mass of KOH as catalyst and had an unsatisfying yield for
[a] X. Zhang, X. Ji, R. Su, Prof. Z. Zhang
School of Chemistry and Chemical Engineering, Shanxi University
Taiyuan, Shanxi 030006 (P. R. China)
[b] X. Zhang, Prof. B. L. Weeks
Department of Chemical Engineering, Texas Tech University
Lubbock, TX 79409 (USA)
[c] Prof. S. Deng
Institute of Applied Chemistry, Shanxi University
Taiyuan 030006 (P. R. China)
Fax: (+86)351-7011688
In addition, graphene and functional graphene materials
could improve catalytic efficiency by activating the reactive
E-mail: dengsl@sxu.edu.cn
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substrates, stabilizing the inter-
mediates, or improving the inter-
action with the reactants to in-
crease the efficiency of molecu-
lar collision of reactants and cat-
alysts.[18,19] Graphene oxide (GO)
has been shown to improve the
aerobic
oxidation
efficiency
when it is used as the support
material, oxidant, or catalyst in
the reaction systems because it
contains abundant oxygen-con-
Figure 1. The dispersibility of KOH (50 mg) with 5% (w/w) graphite (2.5 mg) in different solvents (3 mL), including
DMF (A), THF (B), 1,4-dioxiane (C), toluene (D), ethanol (E), n-hexane (F), water (G), and NMP (H).
taining groups, which can form hydrogen bonds with sub-
strates.[18] For example, GO has been shown to improve the
bromination of phenol to give p-bromophenol.[19] The surface
reaction occurs with the adsorbed Br cation and the adsorbed
phenol on the GO surface and was observed to be faster, and
have higher efficiency and selectivity than if the same reaction
were performed in a homogeneous solution. Herein, we report
an efficient and cost-effective approach for synthesizing 9-fluo-
renones by the aerobic oxidation of 9H-fluorenes using mono-/
multilayer graphene-supported alkaline catalyst in N,N-dime-
thylformamide (DMF; Scheme 1). The results showed that the
yield of 9-fluorenones was improved when adding a few milli-
grams of graphite in DMF because it led to the formation of
a mono-/multilayer graphene-supported KOH composite. This
composite is proposed to greatly improve the dispersion and
surface areas of the alkaline catalyst in the liquid phase. The re-
of graphite and be adsorbed on the graphene surface to break
down the intermolecular forces between the layered gra-
phene; 3) mono-/multilayer graphene were exfoliated from the
graphite sheets to form the mono-/multilayer graphene-sup-
ported KOH composite and were dispersed in DMF or NMP.[20]
It has been demonstrated that the formation of mono-/multi-
layer graphene-supported KOH can improve the dissolution of
the KOH in DMF or NMP and ultimately obtain the uniformly
dispersed solution of mono-/multilayer graphene-supported
KOH composite.
Scheme 2 shows the procedure for the exfoliation of graph-
ite in DMF or NMP with KOH to obtain the mono-/multilayer
graphene-supported KOH composite. It is noted that KOH also
could contribute to the exfoliation of graphene from graphite
in other organic solvents, including THF, 1,4-dioxiane, toluene,
ethanol, and n-hexane; however, the dispersion of graphene in
these solvents is not good.[9] As a result it is likely that very
little mono-/multilayer graphene-supported KOH composite is
actually formed.
The X-ray diffraction (XRD) patterns of graphite and mono-/
multilayer graphene-supported KOH catalyst, which were sepa-
rated from the DMF solution, were first used to prove that
mono-/multilayer graphene were exfoliated from the graphite
sheets. Figure 2A shows the (002) peak in the XRD pattern of
graphite was strong and sharp; however, the (002) peak in
XRD of the mono-/multilayer graphene-supported KOH catalyst
is weak and wide, and has a slight shift to smaller diffraction
angles. The weak and wide peak indicates some graphite crys-
tals were destroyed and the degree of crystallinity decreases.
Graphene is one-atom thick and has an ideal 2D sheet struc-
ture. The isolated 2D graphene sheets don’t have the (002)
crystal structures and the XRD pattern of monolayer graphene
should not have any observable (002) peaks. Therefore, the
mono-/multilayer graphene-supported KOH composite con-
tained some multilayers of graphene. The slight shift of peak
to smaller diffraction angles indicates that the interlayer spac-
ing of multilayered graphene is increasing, which could be due
to inclusion of K ions between the layers or just an effect of
the exfoliation process. The high-resolution transmission elec-
tron microscopy (HRTEM) images demonstrate the mono-/mul-
tilayer graphene-supported KOH composite consisted of mon-
olayers or a few-layers, as shown in Figure 2B-1 and 2B-2. The
statistical AFM measurements show that the thickness of
mono-/multilayer graphene-supported KOH composite was 0.8
ꢀ3.0 nm, as shown in Figure 2C. The atomic force microscope
Scheme 1. Aerobic oxidation from 9H-fluorenes to 9-fluorenones
actions are likely to occur with the three adsorbed compo-
nents, hydroxide anion, 9H-fluorenes, and molecular oxygen
on the graphene surface, thus increasing the reaction efficien-
cy. This new protocol is valuable for the production of weakly
polar 9H-fluorenes, and the resulting products have higher
yield and purity than those produced by current methods. Fur-
thermore, a large-scale (5 kg) pilot study was carried out for
synthesizing 9-fluorenone from 9H-fluorene. This study showed
that the newly developed method has advantage for potential
application in large-scale industrial processes.
Results and Discussion
Obtaining high quality and well disperse KOH with graphene
posed the initial challenge in this study. We first examined the
effect of different solvents, including DMF, THF, 1,4-dioxiane,
toluene, ethanol, n-hexane, water, and N-methyl-2-pyrrolidone
(NMP). Figure 1 shows that KOH made a better dispersion in
DMF and NMP compared with other organic solvents when
adding 5% by weight of graphite sheets and sonicating for
60 minutes.[20] The proposed explanation is: 1) a small quantity
of KOH could dissolve in DMF or NMP and ionize to OHÀ and
K+; 2) the OHÀ and K+ may be intercalated into the interlayer
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Scheme 2. Schematic representation for the exfoliation of graphite in DMF or NMP with KOH to obtain a solution of the mono-/multilayer graphene-support-
ed KOH composite.
persed in DMF. The pH values of KOH and mono-/multilayer
graphene-supported KOH composite in DMF were also mea-
sured. The pH value of 50 mg KOH in 3 mL DMF was 9(Æ0.2),
but the pH value of mono-/multilayer graphene-supported
KOH composite (50 mg KOH and 2.5 mg graphite) in 3 mL
DMF was 13(Æ0.5), which indicates that more KOH was dis-
solved and dispersed in DMF when graphite was added.
Then, 9H-fluorene, which was chosen as a typical substrate
for the optimization of reaction conditions, was added to
these alkaline solutions. DMF and NMP were also found to be
the better solvent to promote the oxidation and the reaction
essentially gave quantitative yield of 9-fluorenone, as shown in
Table 1, entries 1–8. To pursue sustainable methods, we also
tried to use mixtures of water and THF as the solvent in the
presence of phase-transfer catalyst hexadecyl trimethylammo-
nium bromide (CTAB), tetra-n-butylammonium bromide (TBAB),
or didecyldimethylammonium bromide. Unfortunately, the dis-
persibility of KOH and graphite in these mixed solvents was
unsatisfactory and the yields of 9-fluorenone were undesirably
low (Table 1, entries 9–12). Here, we used a mixture of water
with THF rather than DMF or NMP because the THF could be
recycled easily; in contrast, DMF or NMP in water mixtures are
Figure 2. Characterization of the mono-/multilayer graphene-supported KOH
composite and graphite. A) XRD patterns of mono-/multilayer graphene-sup-
ported KOH composite and graphite. B) HRTEM images of mono-/multilayer
graphene-supported KOH composite. C) AFM images of mono-/multilayer
very difficult to recycle. Because of the lower boiling point of
DMF (152–1548C) and hence the readiness of its recycling
through vacuum distillation as compared to that of NMP (202–
2048C), the former was considered as the solvent of choice for
this aerobic oxidation.
graphene-supported KOH composite. D) UV/Vis spectrums of mono-/multi-
layer graphene-supported KOH composite and graphite.
We next examined the effect of the amount of KOH and
graphite (Table 1, entries 13–21). The optimal conditions were
1.0 equivalent of KOH (the molar quantity for 9H-fluorene) as
the catalyst and using 2.5% (the mass quality for KOH) of
graphite as a support (Table 1, entry 22). Here, the KOH used
was only half of that used previously.[8] The reaction yield was
98%, and we did not need to use organic solvents for the fur-
ther purification of 9-fluorenone. Therefore, adding a small
amount of graphite in the reaction system improved the yield
by 7% (compare entry 15 with entry 22) but may also provide
a more cost-effective oxidation method in industrial produc-
tion. We also used carbon black and zeolites as supports; how-
ever, the yield was not improved (Table 1, entries 22 and 23).
Furthermore, when only graphite or reduced graphene oxide
(AFM) images also showed that the graphene surface was not
smooth, which indicates there were some KOH molecules on
the graphene surface. As shown in Figure 2D, the UV/Vis spec-
tra of graphite and mono-/multilayer graphene-supported KOH
composite all exhibited a typical absorption band at 266 nm.
However, the absorbance of mono-/multilayer graphene-sup-
ported KOH composite was ten times stronger than graphite
in DMF at the same concentration, which indicates that
mono-/multilayer graphene sheets were dispersed in DMF in
the presence of KOH. In addition, the peak of mono-/multilayer
graphene-supported KOH composite was wider and smoother,
which demonstrates that the composite was uniformly dis-
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cleavage of the peroxy bond and the formation of
a carbonyl group (Scheme 3). In addition, graphene
can absorb some small molecules or ions, such as
oxygen, aromatic compounds, and OHÀ, onto its sur-
face.[23] When 9H-fluorene interacts with graphene, it
can potentially be adsorbed on the graphene surface
and then reacted with the adsorbed OHÀ to form flu-
orenyl anion intermediate. The formed fluorenyl
anion intermediate reacts with oxygen, leading to
the formation of the fluorenylperoxy anion intermedi-
ate. Then the fluorenylperoxy anion intermediate fur-
ther reacts with an OHÀ to cause the cleavage of the
peroxy bond to form the carbonyl group. Therefore,
the reactions likely occurred with the adsorbed hy-
droxide anion and the adsorbed 9H-fluorenes and
the adsorbed molecular oxygen on the graphene sur-
face therefore increasing the reaction efficiency.[19]
While pure oxygen would have increased the reac-
tion rate, air was used in this study because of eco-
nomic reasons.
Table 1. Effect of different amounts of base, graphite, and solvents on the yield for
the aerobic oxidation of 9H-fluorene.[a]
Entry Base (mmol) Support (mg)
Solvent (mL)
Yield [%]
1
2
3
4
5
6
7
8
KOH (7.5)
KOH (7.5)
KOH (7.5)
KOH(7.5)
KOH(7.5)
KOH(7.5)
KOH (7.5)
KOH (7.5)
KOH(7.5)
KOH (7.5)
KOH (7.5)
KOH (7.5)
KOH (2.5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
KOH (5)
–
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (21)
graphite (0)
graphite (1)
graphite (2)
graphite (3)
graphite (5)
graphite (7)
graphite (10)
carbon black (7)
zeolite (10)
DMF (15)
THF (15)
98
85
45
20
32
<5
31
98
35
42
38
45
68
98
91
91
93
94
97
98
98
92
91
0
1,4-dioxane (15)
toluene (15)
EtOH (15)
n-hexane (15)
H2O (15)
NMP (15)
9
H2O/THF(1:1, v/v; 15)
H2O/THF(1:1, v/v; 15)
H2O/THF(1:1, v/v; 15)
H2O/THF(1:1, v/v; 15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
DMF (15)
10[b]
11[c]
12[d]
13
14
15
16
17
18
19
20
21
22
23
24
25
In addition, we conducted a scale-up preparation
of 9-fluorenone from 9H-fluorene based on the
above optimized conditions. The reaction conditions
and relevant processing parameters of 5.00 kg of 9H-
fluorene in a glass reactor (100 L) were optimized
and the final yield reached 97%. The purity of the
crude product was higher than 98%, thus demon-
strating the practical advantages of this oxidation
method for large scale synthesis of 9-fluorenones.
The recovery of the mono-/multilayer graphene-sup-
graphite (7)
reduced graphene oxide (7) DMF (15)
–
0
[a] Reaction conditions: the reactions were performed with 5 mmol (0.832 g) of 9H-flu-
orene in the presence of the base, graphite (carbon black, zeolite, or reduced gra-
phene oxide), and the solvent as indicated for 16 h at RT in air. [b] CTAB (5 mmol%)
was used as the phase-transfer catalyst. [c] TBAB (5 mmol%) was used as the phase-
transfer catalyst. [d] Didecyldimethylammonium bromide (5 mmol%) was used as the
phase-transfer catalyst.
were used (without adding KOH), no product could be detect-
ed (Table 1, entries 24 and 25). These results indicated that the
graphene only acts as the support—it cannot catalyze the oxi-
dation reactions.
It is possible that higher temperatures could accelerate the
reaction; however, it would also consume more energy. As
a result, the reaction was performed at room temperature. The
final workup procedures involved simple filtering to remove
the mono-/multilayer graphene-supported KOH composite and
the filtrate was concentrated -under reduced pressure- to
obtain the crude product. The crude product was washed with
water three times and then dried to make sure there were no
water soluble salts or base incorporated in the product. The
workup procedures also allowed for the recycling of mono-/
multilayer graphene-supported KOH catalyst and DMF. The
purity of product was analyzed by HPLC methods.[21] We also
performed the oxidation reactions of 9H-fluorene under
oxygen or argon atmosphere and found that the reactions
went to completion much faster (within 10 h) under an oxygen
environment whereas under an argon atmosphere no product
could be detected. These results further proved the aerobic ox-
idation mechanism:[8,22] for the formation of 9-fluorenone from
reaction of the fluorenyl anion with molecular oxygen presum-
ably involves abstraction of a proton from the benzylic site of
the fluorenylperoxy anion intermediate by OH, leading to the
Scheme 3. Proposed mechanisms for the formation of 9-fluorenone from
9H-fluorene
ported KOH catalyst and DMF were 79% and 85%, respective-
ly. We also performed the scale-up preparation using the re-
claimed mono-/multilayer graphene-supported KOH catalyst
and DMF. After five cycles, the final yield was still around 97%
and the purity was also higher than 98%.
To expand the scope of this newly-developed oxidation
method, we explored the oxidation of other common 9H-fluo-
renes. As can be seen from the results shown in Table 2, all re-
actions that were tested gave the corresponding 9-fluorenone
derivatives in >93% yield.
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Table 2. Air oxidation of 9H-fluorenes 1a–1p.[a]
Entry
1
Substrate
Time [h]
16
Product
Yield [%]
98
Entry
9
Substrate
Time [h]
Product
Yield [%]
1a
1b
2a
2b
1i
1j
10
16
2i
2j
98
94
2
8
98
10
3
4
1c
8
2c
98
96
11
12
1k
1l
24
24
2k
2l
96
95
1d
16
2d
5
6
7
1e
1 f
1g
16
8
2e
2 f
2g
97
98
96
13
14
1m
1n
24
24
32
2m
2n
2o
95
94
94
10
15[b] 1o
8
1h
8
2h
98
16[c] 1p
36
2p
93
[a] Reaction conditions: 9H-fluorenes (5 mmol) and solution of mono-/multilayer graphene-supported KOH composite (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL). [b] Using a solution of mono-/multilayer graphene-supported KOH composite (KOH 0.560 g, 10 mmol; graphite 14 mg; DMF 25 mL). [c] Using a solution of
mono-/multilayer graphene-supported KOH composite (KOH 0.840 g, 15 mmol; graphite 21 mg; DMF 35 mL). All reactions were performed at room temperature.
Preparation of the mono-/multilayer graphene-supported
KOH composite
Conclusion
The Mono-/multilayer graphene-supported KOH composite was
prepared as describe previously.[20] Briefly, the natural graphite
sheets were exfoliated with KOH in organic solvents by a tip soni-
cator (Bandelin Sonoplus) for 1 hour to form a solution of mono-/
multilayer graphene-supported KOH composite. During the sonica-
tion, the samples were cooled to 08C using an ice/water bath.
In summary, we have developed a more efficient and cost-ef-
fective approach to synthesize 9-fluorenones from 9H-fluo-
renes using a mono-/multilayer graphene-supported KOH com-
posite as the catalyst and DMF as the solvent. Graphene mate-
rials in the oxidation system played a role in increasing the effi-
ciency of molecular collision of absorbed KOH, 9H-fluorenes,
and oxygen on a large surface. Moreover, the catalyst and the
solvent can be recycled and reused. Also, a scale-up prepara-
tion of 9-fluorenone from 9H-fluorene employing this method
was achieved and displayed the advantages of high yield, high
purity, and environmental sustainability.
Characterization
High-resolution transmission electron microscopy (HRTEM)
analysis
The mono-/multilayer graphene-supported KOH composite sam-
ples for HRTEM (JEOL-2100) observation were prepared by placing
drops of the diluted mono-/multilayer graphene-supported KOH
composite suspension onto a carbon-coated copper grid (Ultrathin
Carbon Film on Holey Carbon Support Film, 400 mesh, Copper, Ted
Pella, Inc.), which was then dried under ambient conditions prior
to being introduced into the TEM chamber. The samples were ana-
lyzed by using an acceleration voltage of 200 kV.
Experimental Section
Materials
Graphite, carbon black, zeolite (particle size<45 mm), and other or-
ganic reagents were purchased from Sigma–Aldrich, TCI, or Alfa
Aesar. 2,7-Dibromo-7-nitro-9H-fluorene and 2,7-bis(diphenylamino)-
9H-fluorene were synthesized by using published procedures to
give product with purify greater than 98%.[24,25] All other inorganic
reagents and organic solvents were purchased from Tianjin Chemi-
cal Co. All chemicals were analytical grade and used as received.
X-ray diffraction (XRD) analysis
The XRD pattern of the graphite and mono-/multilayer graphene-
supported KOH composite sample was measured using an X-ray
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diffractometer (X’Pert PRO, PANAlytical). The samples were ana-
lyzed from 5 to 708 (2q).
used as the oxidation source. The reaction mixture was filtered to
remove the mono-/multilayer graphene-supported KOH composite
and the filtrate was concentrated under reduced pressure to
obtain the crude products. The solvents and the removed mono-/
multilayer graphene-supported KOH composite could be recycled
and reused. The crude products were washed with water (3ꢁ
100 mL), dried, and purified (as outlined below) to give the final
products.
Atomic force microscope (AFM) analysis
The thickness of the mono-/multilayer graphene-supported KOH
composite sample was obtained with a Nanoscope IIIa multimode
AFM (Veeco, Santa Barbara, CA) operating in tapping mode. The
AFM tip (Tetra15/Au/15, Nanotechnology LLC.) is a silicon cantilever
with Au conductive coating, with the resonant frequency 200
ꢀ400 kHz and force constant 20~75 NmÀ1. All images were col-
lected at a scan rate of 0.25 Hz with a driving frequency of 325 kHz
(256ꢁ256 lines scan-). The samples were made by placing drops of
the diluted mono-/multilayer graphene-supported KOH composite
suspension onto a silicon substrates (1 cmꢁ1 cm), and the solvent
was then dried by using a spincoater with 3000 rpm for 3 minutes.
Polished silicon wafers were purchased from Nova Electronic Mate-
rials Ltd. The diced silicon substrates were cleaned by a solution
containing 5 parts NH4OH (20%), 1 part H2O2 (30% solution), and
1 part deionized water and heated to 50ꢀ708C for 3 hours, rinsed
with deionized water and dried at 708C under N2. The substrates
were stored in desiccators prior to use.[26]
Synthesis of 9-fluorenone (2a)
Application of the general procedure to 9H-fluorene (1a; 0.831 g,
5 mmol) and mono-/multilayer graphene-supported KOH compo-
site solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF 15 mL) af-
forded compound 2a (0.883 g, 98%) as a yellow solid: m.p. 83–
1
848C (lit. 83–858C);[27] IR (KBr): 1714 cmÀ1 (C=O); H NMR (300 MHz,
258C, CDCl3, TMS): d=7.66 (d, J=7.2 Hz, 2H), 7.46–7.49 (m, 4H),
7.29 ppm (d, J=7.0 Hz, 2H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS):
d=194.2, 144.8, 135.2, 134.6, 129.5, 124.7, 120.9 ppm; elemental
analysis calcd (%) for C13H8O: C 86.65, H 4.47; found: C 86.78,
H 4.49.
Synthesis of 2-bromo-9-fluorenone (2b)
Ultraviolet/visible (UV/Vis) spectroscopy analysis
Application of the general procedure to 2-bromo-9H-fluorene (1b;
1.226 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2b (1.270 g, 98%) as a yellow solid:
m.p. 147–1488C (lit. 145–1478C);[28] IR (KBr): 1718 cmÀ1 (C=O);
1H NMR (300 MHz, 258C, CDCl3, TMS): d=7.76 (s, 1H), 7.66 (d, J=
7.3 Hz, 1H), 7.60 (d, J=7.8 Hz, 1H), 7.51–7.52 (m, 2H), 7.40 (d, J=
7.8 Hz, 1H), 7.32–7.33 ppm (m, 1H); 13C NMR (75.5 MHz, 258C,
CDCl3, TMS): d=192.7, 143.9, 143.3, 137.4, 136.1, 135.3, 133.9,
129.8, 127.9, 124.9, 123.2, 121.9, 120.7 ppm; elemental analysis
calcd (%) for C13H7BrO: C 60.26, H 2.72; found: C 60.52, H 2.76.
UV/Vis absorption spectra were recorded with a Lambda 1050 UV/
Vis/NIR spectrophotometer (PerkinElmer) using a quartz cell with
a 1 cm optical path. The concentration for the graphite (with/with-
out KOH) was 0.25 mgmLÀ1
.
pH Value analysis
The pH values were recorded with a pH value tester (ORION pH
value tester 2001).
Fourier Transform infrared (FTIR) spectroscopy analysis
FTIR spectra were recorded on a Shimadzu 8400-S (wave numbers
in cmÀ1). All samples were examined as KBr plates.
Synthesis of 2,7-dibromo-9-fluorenone (2c)
Application of the general procedure to 2,7-dibromo-9H-fluorene
(1c; 1.620 g, 5 mmol) and mono-/multilayer graphene-supported
KOH composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg;
DMF 15 mL) afforded compound 2c (1.656 g, 98%) as a yellow
solid: m.p. 203–2058C (lit. 204–2058C);[29] IR (KBr): 1722 cmÀ1 (C=
O); 1H NMR (300 MHz, 258C, CDCl3, TMS): d=7.68 (d, J=1.8 Hz,
2H), 7.54 (dd, J=7.9 Hz, 1.8 Hz, 2H), 7.30 ppm (d, J=7.9 Hz, 2H);
13C NMR (75.5 MHz, 258C, CDCl3, TMS): d=191.0, 142.4, 137.6,
135.6, 128.1, 123.4, 122.0 ppm; elemental analysis calcd (%) for
C13H6Br2O: C 46.20, H 1.79; found: C 46.52, H 1.83.
Nuclear magnetic resonance (NMR) analysis
Nuclear magnetic resonance (1H NMR or 13C NMR) spectra were re-
corded on a Brucker DRX 300 MHz NMR spectrometer. Chemical
shifts were expressed in parts per million (d scale) downfield from
tetramethylsilane and were referenced to residual proton in the
NMR solvent (CHCl3: d=7.26 ppm). Data are presented as follows:
chemical shift, multiplicity (s=singlet, d=doublet, t=triplet, q=
quartet, m=multiplet and/or multiple resonances), coupling con-
stant in Hertz (Hz), integration.
Synthesis of 2-methylfluorenone (2d)
Synthesis
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 2-methyl-9H-fluorene (1d;
0.901 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2d (0.932 g, 96%) as a yellow solid:
m.p. 90–928C (lit. 91–928C);[27] IR (KBr): 1711 cmÀ1(C=O); 1H NMR
(300 MHz, 258C, CDCl3, TMS): d=7.63 (d, J=7.2 Hz, 1H), 7.45–7.48
(m, 3H), 7.39 (d, J=7.6 Hz, 1H), 7.24–7.29 (m, 2H), 2.37 ppm (s,
3H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS): d=194.3, 144.5, 141.5,
138.9, 135.2, 134.6, 134.3, 134.2, 128.7, 124.9, 124.1, 121.9, 119.7,
General procedure for the oxidation of 9H-fluorenes to 9-fluo-
renones
Into a 100 mL, two-necked flask equipped with an electromagnetic
stirrer and an air condenser was charged solutions of 9H-fluorenes
and the mono-/multilayer graphene-supported KOH composite,
and the mixture was stirred at room temperature. All reactions
were carried out while magnetically stirred and were monitored by
thin-layer chromatography (TLC). Exposure to ambient air was
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21.3 ppm; elemental analysis calcd (%) for C14H10O: C 86.57, H 5.19;
found: C 86.72, H 5.22.
127.7, 125.9, 123.5 ppm; elemental analysis calcd (%) for
C13H6BrNO3: C 51.35, H 1.99, N 4.61; found: C 51.21, H 1.98, N 4.59.
Synthesis of 2,7-dibromo-4-nitro-9-fluorenone (2i)
Synthesis of 2-methoxy-9-fluorenone (2e)
Application of the general procedure to 2,7-dibromo-4-nitro-9H-flu-
orene (2i; 1.845 g, 5 mmol) and mono-/multilayer graphene-sup-
ported KOH composite solution (KOH 0.280 g, 5 mmol; graphite
7 mg; DMF 15 mL) afforded compound 2i (1.877 g, 98%) as
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 2-methoxy-9H-fluorenone
(1e; 0.981 g, 5 mmol) and mono-/multilayer graphene-supported
KOH composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg;
DMF 15 mL) afforded compound 2e (1.019 g, 97%) as a yellow
a
yellow solid: m.p. 194–1968C (lit. 192–1938C);[33] IR (KBr):
1
1726 cmÀ1 (C=O); H NMR (300 MHz, 258C, CDCl3, TMS): d=8.24 (d,
J=1.8 Hz, 1H), 8.06 (d, J=1.8 Hz, 1H), 7.95 (d, J=8.3 Hz, 1H), 7.91
(d, J=2.0 Hz, 1H), 7.74 ppm (dd, J=8.3 Hz, 2.0 Hz, 1H); 13C NMR
(75.5 MHz, 258C, CDCl3, TMS): d=190.3, 149.4, 141.9, 139.2, 137.1,
134.8, 131.7, 128.2, 125.8, 125.4, 123.5, 119.7 ppm; elemental analy-
sis calcd (%) for C13H5Br2NO3: C 40.77, H 1.32, N 3.66; found:
C 40.86, H 1.33, N 3.64.
1
solid: m.p. 78–798C (lit. 788C);[29] IR (KBr): 1709 cmÀ1 (C=O); H NMR
(300 MHz, 258C, CDCl3, TMS): d=7.58 (d, J=7.6 Hz, 1H), 7.36–7.48
(m, 3H), 7.16–7.21 (m, 2H), 6.97 (dd, J=8.2 Hz, 2.4 Hz, 1H),
3.84 ppm (s, 3H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS): d=194.0,
161.1, 145.1, 137.2, 136.0, 135.1, 134.5, 128.0, 124.5, 121.5, 120.4,
119.8, 109.5, 56.0 ppm; elemental analysis calcd (%) for C14H10O2:
C 79.98, H 4.79; found: C 79.82, H 4.83.
Synthesis of 2,7-bis(diphenylamino)-9-fluorenone (2j)
Synthesis of 2-nitro-9-fluorenone (2 f)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 2,7-bis(diphenylamino)-
9H-fluorene (1j; 2.503 g, 5 mmol) and mono-/multilayer graphene-
supported KOH composite solution (KOH 0.280 g, 5 mmol; graphite
7 mg; DMF 15 mL) afforded compound 2j (2.419 g, 94%) as a red
solid: m.p. 213–2158C (lit. 219–2208C);[34] IR (KBr): 1712 cmÀ1 (C=
O); 1H NMR (300 MHz, 258C, CDCl3, TMS): d=7.66 (d, J=7.6 Hz,
4H), 7.48 (d, J=7.6 Hz, 6H), 7.32–7.23 (m, 10H), 7.06 (d, J=7.6 Hz,
4H), 6.92 ppm (t, J=7.4 Hz, 2H); 13C NMR (75.5 MHz, 258C, CDCl3,
TMS): d=194.2, 149.1, 148.0, 138.8, 136.6, 130.6, 129.6, 125.8,
124.6, 121.4, 120.2 ppm; elemental analysis calcd (%) for
C37H26N2O: C 86.35, H 5.09, N 5.44; found: C 86.01, H 5.11, N 5.48.
Application of the general procedure to 2-nitro-9H-fluorene (1 f;
1.056 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2 f (1.103 g, 98%) as a yellow solid:
m.p. 222–2238C (lit. 222–2248C);[30] IR (KBr): 1717 cmÀ1 (C=O);
1H NMR (300 MHz, 258C, CDCl3, TMS): d=8.48 (d, J=1.9 Hz, 1H),
8.43 (dd, J=1.9 Hz, 8.2 Hz, 1H), 7.77 (d, J=7.3 Hz, 1H), 7.72–7.67
(m, 2H), 7.62 (t, 1H), 7.46 (t, 1H) ppm; 13C NMR (75.5 MHz, 258C,
CDCl3, TMS): d=191.2, 150.0, 149.0, 142.5, 135.7, 135.5, 135.3,
131.3, 130.2, 125.4, 122.1, 121.0, 119.8 ppm; elemental analysis
calcd (%) for C13H7NO3: C 69.33, H 3.13, N 6.22; found: C 69.21,
H 3.11, N 6.25.
Synthesis of 11H-benzo[a]fluoren-11-one (2k)
Synthesis of 4-chlorofluorenone (2g)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 11H-benzo[a]fluorene (1k;
1.081 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2k (1.105 g, 96%) as an orange solid:
m.p. 132–1348C (lit. 1328C);[35] IR (KBr): 1702 cmÀ1 (C=O); 1H NMR
(300 MHz, 258C, CDCl3, TMS): d=8.94 (d, J=8.6 Hz, 1H), 7.98 (d,
J=8.2 Hz, 1H), 7.76 (d, J=8.2 Hz, 1H), 7.57–7.65 (m, 3H), 7.42–7.48
(m, 3H), 7.22 ppm (dt, J=8.6 Hz, 2.0 Hz, 1H); 13C NMR (75.5 MHz,
258C, CDCl3, TMS): d=196.2, 146.9, 144.6, 136.6, 135.2, 135.1,
134.9, 130.8, 130.1, 129.9, 129.3, 127.6, 127.1, 125.0, 124.5, 120.6,
118.8 ppm; elemental analysis calcd (%) for C17H10O: C 88.67,
H 4.38; found: C 88.81, H 4.42.
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 4-chloro-9H-fluorene (1g;
1.003 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2g (1.030 g, 96%) as a yellow solid:
m.p. 145–1478C (lit. 147–1488C);[31] IR (KBr): 1718 cmÀ1 (C=O);
1H NMR (300 MHz, 258C, CDCl3, TMS): d=8.15 (d, J=7.6 Hz, 1H),
7.73 (d, J=7.2 Hz, 1H), 7.61 (d, J=7.2 Hz, 1H), 7.58 (d, J=7.6 Hz,
1H), 7.45 (d, J=8.3 Hz, 1H), 7.38 (t, 1H), 7.26 ppm (t, 1H); 13C NMR
(75.5 MHz, 258C, CDCl3, TMS): d=192.6, 143.0, 140.7, 136.4, 136.2,
134.8, 134.0, 129.8, 129.4, 129.3, 124.3, 124.0, 122.5 ppm; elemental
analysis calcd (%) for C13H7ClO: C 72.74, H 3.29; found: C 72.49,
H 3.31.
Synthesis of 11H-benzo[b]fluoren-11-one (2l)
Synthesis of 2-nitro-7-bromo-9-fluorenone (2h)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 11H-benzo[b]fluorene (1l;
1.081 g, 5 mmol) and mono-/multilayer graphene-supported KOH
composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg; DMF
15 mL) afforded compound 2l (1.094 g, 95%) as a yellow solid:
m.p. 153–1558C (lit. 1528C);[35] IR (KBr): 1700 cmÀ1 (C=O); 1H NMR
(300 MHz, 258C, CDCl3, TMS): d=8.12 (s, 1H), 7.89–7.76 (m, 3H),
7.70 (d, J=8.2 Hz, 1H), 7.66 (d, J=7.6 Hz, 1H), 7.56–7.48 (m, 2H),
7.42 (td, J=8.2 Hz, 1.6 Hz, 1H), 7.30 ppm (td, J=7.6 Hz, 2.0 Hz,
1H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS): d=193.2, 145.0, 138.6,
137.2, 136.3, 135.1, 132.9, 130.9, 129.4, 129.2, 129.0, 127.2, 125.8,
Application of the general procedure to 2-nitro-7-bromo-9H-fluo-
rene (1h; 1.451 g, 5 mmol) and mono-/multilayer graphene-sup-
ported KOH composite solution (KOH 0.280 g, 5 mmol; graphite
7 mg; DMF 15 mL) afforded compound 2h (1.490 g, 98%) as
a
yellow solid: m.p. 228–2308C (lit. 230–2318C);[32] IR (KBr):
1724 cmÀ1 (C=O); H NMR (300 MHz, 258C, CDCl3, TMS): d=8.52 (d,
J=1.8 Hz, 1H), 8.48 (dd, J=1.8 Hz, 8.2 Hz, 1H), 7.93 (d, J=1.8 Hz,
1H), 7.78 (dd, J=1.8 Hz, 8.0 Hz, 1H), 7.74 (d, J=8.2 Hz, 1H),
7.69 ppm (d, J=8.0 Hz, 1H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS):
d=188.5, 144.9, 138.5, 137.3, 135.6, 135.2, 132.7, 131.9, 128.3,
1
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125.7, 124.6, 121.2, 119.2 ppm; elemental analysis calcd (%) for
C17H10O: C 88.67, H 4.38; found: C 88.84, H 4.41.
Pilot-scale study for synthesis of 9-fluorenone
Into a 100 L four-necked flask equipped with a mechanical stirrer,
a bubbling tube, and an air condenser was charged 9H-fluorene
(1a; 5.00 Kg, 30.08 mol) and mono-/multilayer graphene-supported
KOH composite solution (KOH 1.684 Kg, 30.08 mol; graphite
42.12 g; DMF 60 L). The reaction mixture was stirred at room tem-
perature while the solution surface was kept lower than the bub-
bling tube, and air was introduced for 5 min every 30 min to
ensure there was sufficient oxygen with minimal loss of solvent. At
the completion of the reaction, the reaction mixture was filtered to
remove the mono-/multilayer graphene-supported KOH composite
and the filtrate was concentrated under vacuum to obtain the
crude product. The crude product was washed with water (3ꢁ
100 L) and then dried in an oven to give 5.26 Kg of 9-fluorenone,
yield: 97%. The mono-/multilayer graphene-supported KOH com-
posite (1.362 Kg, 79%) and DMF (51 L, 85%) were recycled.
Synthesis of 11H-benzo[c]fluoren-11-one (2m)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 11H-benzo[c]fluorene
(1m; 1.081 g, 5 mmol) and mono-/multilayer graphene-supported
KOH composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg;
DMF 15 mL) afforded compound 2m (1.093 g, 95%) as a yellow
solid: m.p. 159–1618C (lit. 161–1628C);[22] IR (KBr): 1709 cmÀ1 (C=
O); 1H NMR (300 MHz, 258C, CDCl3, TMS): d=8.46 (d, J=7.6 Hz,
1H), 8.01 (d, J=7.6 Hz, 1H), 7.86 (d, J=7.2 Hz, 1H), 7.76 (d, J=
7.8 Hz, 1H), 7.72 (d, J=7.8 Hz, 1H), 7.68 (t, J=7.2 Hz, 1H), 7.60–
7.54 (m, 1H), 7.51–7.47 (m, 1H), 7.32–7.23 ppm (m, 2H); 13C NMR
(75.5 MHz, 258C, CDCl3, TMS): d=194.6, 145.1, 143.0, 138.3, 134.6,
132.0, 130.0, 129.8, 129.1, 129.0, 128.4, 128.0, 127.9, 126.0, 124.2,
123.5, 120.0 ppm; elemental analysis calcd (%) for C14H10O: C 88.67,
H 4.38; found: C 88.89, H 4.60.
Acknowledgements
We are exceedingly grateful for support received from the Shanxi
Scholarship Council of China (no. 200817) and the Science and
Technology Project for the Higher Educational Institutes of Shanxi
Province of China (no. 20080001).
Synthesis of 12H-dibenzo[b,h]fluoren-12-one (2n)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 12H-dibenzo[b,h] fluorene
(1n; 1.332 g, 5 mmol) and mono-/multilayer graphene-supported
KOH composite solution (KOH 0.280 g, 5 mmol; graphite 7 mg;
DMF 15 mL) afforded compound 2n (1.318 g, 94%) as a yellow
solid: m.p. 273–2758C (lit. 275–2768C);[36] IR (KBr): 1707 cmÀ1 (C=
Keywords: aerobic oxidation
fluorenones · synthetic methods
· catalysis · graphene · 9-
1
O); H NMR (300 MHz, 258C, CDCl3, TMS): d=8.29 (s, 2H), 8.11 (s,
2H), 7.95 (d, J=8.2 Hz, 2H), 7.90 (d, J=8.2 Hz, 2H), 7.60 (td, J=
8.2 Hz, 1.8 Hz, 2H), 7.50 ppm (td, J=8.2 Hz, 1.8 Hz, 2H); 13C NMR
(75.5 MHz, 258C, CDCl3, TMS): d=193.8, 140.0, 138.5, 135.3, 134.8,
131.9, 130.2, 129.6, 128.0, 126.8, 120.8 ppm; elemental analysis
calcd (%) for C21H12O: C 89.98, H 4.31; found: C 89.74, H 4.35.
[1] H. S. Oh, S. Liu, H. Jee, A. Baev, M. T. Swihart, P. N. Prasad, J. Am. Chem.
Soc. 2010, 132, 17346–17348.
[2] C.-J. Qin, A. Islam, L.-Y. Han, J. Mater. Chem. 2012, 22, 19236–19243.
[3] J. Pecher, J. Huber, M. Winterhalder, A. Zumbusch, S. Mecking, Biomac-
romolecules 2010, 11, 2776–2780.
[4] a) K. M. Omer, S.-Y. Ku, Y.-C. Chen, K.-T. Wong, A. J. Bard, J. Am. Chem.
Soc. 2010, 132, 10944–10952; b) F. Jaramillo-Isaza, M. L. Turner, J. Mater.
Chem. 2006, 16, 83–89;c) K. Zhang, Z. Chen, C.-L. Yang, Y.-T. Tao, Y. Zou,
J.-G. Qin, Y. Cao, J. Mater. Chem. 2008, 18, 291–298; d) L. Oldridge, M.
Kastler, K. Mꢂllen, Chem. Commun. 2006, 885; e) Y.-M. Jeon, J.-W. Kim,
C.-W. Lee, M.-S. Gong, Dyes Pigm. 2009, 83, 66–71;f) X. Zhang, J.-B. Han,
P.-F. Li, X. Ji, Z. Zhang, Synth. Commun. 2009, 39, 3804–3815;g) K. M.
Omer, S.-Y. Ku, K.-T. Wong, A. J. Bard, J. Am. Chem. Soc. 2009, 131,
10733–10741;h) Y. Wei, S. Samori, S. Tojo, M. Fujitsuka, J.-S. Lin, C.-T.
Chen, T. Majima, J. Am. Chem. Soc. 2009, 131, 6698–6707.
[5] a) F. Lincker, B. Heinrich, R. D. Bettignies, P. Rannou, J. Pꢃcaut, B. Grꢃvin,
A. Pron, B. Donnio, R. Demadrille, J. Mater. Chem. 2011, 21, 5238–
5247;b) R. Demadrille, N. Delbosc, Y. Kervella, M. Firon, R. D. Bettignies,
M. Billon, P. Rannou, A. Pron, J. Mater. Chem. 2007, 17, 4661–4669.
[6] a) S. E. Dapurkar, H. Kawanami, T. Yokoyama, Y. Ikushima, New J. Chem.
2009, 33, 538–544; b) F. Majunke, H. Borchert, M. Baerns, Stud. Surf. Sci.
Catal. 1993, 75, 707–17.
Synthesis of indeno[1,2-b]fluorene-6,12-dione (2o)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to 6,12-dihydroindeno[1,2b]-
fluorene (1o; 1.272 g, 5 mmol) and mono-/multilayer graphene-
supported KOH composite solution (KOH 0.560 g, 10 mmol; graph-
ite 14 mg; DMF 25 mL) afforded compound 2o (1.327 g, 94%) as
a
yellow solid: m.p. 345–3478C (lit. 351–3548C);[37] IR (KBr):
1716 cmÀ1 (C=O); H NMR (300 MHz, 258C, CDCl3, TMS): d=7.89 (s,
2H), 7.80 (d, J=8.2 Hz, 2H), 7.66–7.62 (m, 4H), 7.45–7.41 ppm (m,
2H); 13C NMR (75.5 MHz, 258C, CDCl3, TMS): d=194.1, 147.0, 144.8,
140.3, 136.5, 135.0, 130.6, 125.6, 121.8, 116.9 ppm; elemental analy-
sis calcd (%) for C20H10O2: C 85.09, H 3.57; found: C 84.74, H 3.40.
1
[7] a) M. Nakanishi, C. Bolm, Adv. Synth. Catal. 2007, 349, 861–864; b) H. P.
Rathnayake, A. Cirpan, F. E. Karasz, M. Y. Odoi, N. I. Hammer, M. D.
Barnes, P. M. Lahti, Chem. Mater. 2007, 19, 3265–3270; c) N. Chidambar-
am, S. Chandrasekaran, J. Org. Chem. 1987, 52, 5048–5051; d) R. Ran-
garajan, E. J. Eisenbraun, J. Org. Chem. 1985, 50, 2435–2438; e) R. Gri-
sorio, P. Mastrorilli, G. Ciccarella, G. P. Suranna, C. F. Nobile, Tetrahedron
Lett. 2008, 49, 2078–2082; f) J. G. Rodrꢄguez, J. L. Tejedor, T. La Parra, C.
Dꢄaz, Tetrahedron 2006, 62, 3355–3361.
Synthesis of truxenone (2p)
Application of the general procedure (the crude product was puri-
fied by recrystallization from ethanol) to truxene (1p; 1.712 g,
5 mmol) and mono-/multilayer graphene-supported KOH compo-
site solution (KOH 0.840 g, 5 mmol; graphite 21 mg; DMF 35 mL)
afforded compound 2p (1.787 g, 93%) as a yellow solid: m.p.>
3508C (lit.>3508C);[38] IR (KBr): 1708 cmÀ1 (C=O); 1H NMR
(300 MHz, 258C, CDCl3, TMS): d=9.35 (d, J=8.2 Hz, 3H), 7.94 (d,
J=8.2 Hz, 3H), 7.76 (t, J=8.2 Hz, 3H), 7.64 ppm (t, J=8.2 Hz, 3H);
elemental analysis calcd (%) for C27H12O3: C 84.37, H 3.15; found:
C 84.54, H 3.21.
[8] X. Zhang, X. Ji, S.-S. Jiang, L.-L. Liu, B. L. Weeks, Z. Zhang, Green Chem.
2011, 13, 1891–1896.
[9] a) H. Kim, A. A. Abdala, C. W. Macosko, Macromolecules 2010, 43, 6515–
6530; b) X. Huang, X.-Y. Qi, F. Boey, H. Zhang, Chem. Soc. Rev. 2012, 41,
666–686; c) Y.-X. Liu, X.-C. Dong, P. Chen, Chem. Soc. Rev. 2012, 41,
2283–2307; d) M. J. Allen, V. C. Tung, R. B. Kaner, Chem. Rev. 2010, 110,
132–145; e) S. Mao, H.-H. Pu, J.-H. Chen, RSC Adv. 2012, 2, 2643–2662;
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2013, 78, 703 – 711 710

CHEMPLUSCHEM
FULL PAPERS
www.chempluschem.org
f) X. Zhang, W. M. Hikal, Y. Zhang, S. K. Bhattacharia, L. Li, S. Panditrao,
S.-R. Wang, B. L. Weeks, Appl. Phys. Lett. 2013, 102, 141905; g) T.-C. He,
X.-Y. Qi, R. Chen, J. Wei, H. Zhang, H.-D. Sun, ChemPlusChem. 2012, 77,
688–693; h) D. Sun, L. Jin, Y. Chen, J.-R. Zhang, J.-J. Zhu, ChemPlusChem
2013, 78, 227–234.
[21] The chromatographic conditions: the column was dalian Elite Hypersil
OSD2 C18 column (4.6ꢁ250 mm i.d., 5 mm), the mobile phase was meth-
anol/water (85:15 v/v), the flow rate was 1.0 mLminÀ1, the detection
wavelength was 254 nm, and the column temperature was 258C.
[22] R. G. Harvey, E. Abu-Shqara, C. X. Yang, J. Org. Chem. 1992, 57, 6313–
6317.
[23] a) D. Jena, A. Konar, Phys. Rev. Lett. 2007, 98, 136805; b) A. Opitz, M.
Scherge, S. I. U. Ahmed, J. A. Schaefer, J. Appl. Phys. 2007, 101, 064310;
c) M. Topsakal, H. Sahin, S. Ciraci, Phys. Rev. B 2012, 85, 155445; d) Y.
Sato, K. I. Takai, T. Enoki, Nano Lett. 2011, 11, 3468–3475; e) X.-F. Feng,
S. Maier, M. Salmeron, J. Am. Chem. Soc. 2012, 134, 5662–5668; f) F.
Yavari, C. Kritzinger, C. Gaire, L. Song, H. Gullapalli, T. Borca-Tasciuc, P. M.
Ajayan, N. Koratkar, Small 2010, 6, 2535–2538; g) F. Schedin, A. K. Geim,
S. V. Morozov, E. W. Hill, P. Blake, M. I. Katsnelson, K. S. Novoselov, Nat.
Mater. 2007, 6, 652–655.
[24] S. Kajigaeshi, T. Kadowaki, A. Nishida, S. Fujisaki, Bull. Chem. Soc. Jpn.
1986, 59, 97–103.
[25] M. Kimura, Y. Toba, T. Kurata, T. Enokida, Y. Sawaki, K. Takagi, Bull. Chem.
Soc. Jpn. 2007, 80, 418–422.
[26] X. Zhang, G.-X. Zhang, Y.-C. Liao, B. L. Weeks, Z. Zhang, J. Colloid Inter-
face Sci. 2012, 387, 175–179.
[27] P. Sunanda, S. Shubhankar, K. R. Jayanta, Tetrahedron Lett. 2010, 51,
5604–5608.
[10] a) B. F. Machado, P. Serp, Catal. Sci. Technol. 2012, 2, 54–75; b) H.-Y. Li,
Y.-W. Zhang, G.-H. Chang, S. Liu, J.-Q. Tian, Y.-L. Luo, A. M. Asiri, A. O. Al-
Youbi, X.-P. Sun, ChemPlusChem 2012, 77, 545–550; c) Q. Wang, M.-M.
Song, C.-L. Chen, W.-P. Hu, X.-K. Wang, ChemPlusChem. 2012, 77, 432–
436.
[11] a) G. M. Scheuermann, L. Rumi, P. Steurer, W. Bannwarth, R. Mꢂlhaupt, J.
Am. Chem. Soc. 2009, 131, 8262–8270; b) Y. Li, X.-B. Fan, J.-J. Qi, J.-Y. Ji,
S.-L. Wang, G.-J. Zhang, F.-B. Zhang, Nano Res. 2010, 3, 429–437; c) Y. Li,
X.-B. Fan, J.-J. Qi, J.-Y. Ji, S.-L. Wang, G.-L. Zhang, F.-B. Zhang, Mater. Res.
Bull. 2010, 45, 1413–1418; d) A. R. Siamakib, A. EI Rahman, S. Khder, V.
Abdelsayed, M. S. El-Shall, B. F. Gupton, J. Catal. 2011, 279, 1–11.
[12] S. Zhang, Y.-Y. Shao, H.-G. Liao, J. Liu, I. A. Aksay, G.-P. Yin, Y.-H. Lin,
Chem. Mater. 2011, 23, 1079–1081.
[13] H.-Y. Chen, Y. Li, F.-B. Zhang, G.-L. Zhang, X.-B. Fan, J. Mater. Chem. 2011,
21, 17658–17661.
[14] a) E. J. Yoo, T. Okata, T. Akita, M. Kohyama, J. Nakamura, I. Honma, Nano
Lett. 2009, 9, 2255–2259; b) S. Guo, S. Dong, E. Wang, ACS Nano 2010,
4, 547–555.
[28] W.-F. Jiang, H.-L. Wang, An-G. Wang, Z.-Q. Li, Synth. Commun. 2008, 38,
1888–1895.
[15] J. Du, X. Lai, N. Yang, J. Zhai, D. Kisailus, F. Su, D. Wang, L. Jiang, ACS
Nano 2011, 5, 590–596.
[29] A. Hauser, J. Thurner, B. J. Hinzman, J. Prakt. Chem. 1988, 330, 367–378.
[30] D. F. Detar, D. I. Relyea, J. Am. Chem. Soc. 1954, 76, 1680–1685.
[31] E. Campaigne, M. B. Reid, Jr., J. Org. Chem. 1947, 12, 807–814.
[32] W. E. Hahn, W. Cherasko, Roczniki Chemii 1975, 49, 1309–1327.
[33] D. W. Price, Jr., J. M. Tour, Tetrahedron 2003, 59, 3131–3165.
[34] J. Ipaktschi, A. Sharifi, Monatsh. Chem. 1998, 129, 915–920.
[35] A. Streitwieser, Jr., S. M. Brown, J. Org. Chem. 1988, 53, 904–906.
[36] L. J. Morris, L. C. Becker, R. F. Fronczek, H. W. Daly, L. M. McLaughlin, J.
Org. Chem. 1994, 59, 6484–6486.
[16] D. Marquardt, C. Vollmer, R. Thomann, P. Steurer, R. Mꢂlhaupt, E. Redel,
C. Janiak, Carbon 2011, 49, 1326–1332.
[17] a) J. Huang, L. Zhang, B. Chen, N. Ji, F. Chen, Y. Zhang, Z. Zhang, Nano-
scale 2010, 2, 2733–2738; b) P. Wang, L. Han, C.-Z. Zhu, Y.-M. Zhai, S.-S.
Dong, Nano Res. 2011, 4, 1153–1162.
[18] a) D. R. Dreyer, H.-P. Jia, A. D. Todd, J. Geng, C. W. Bielawski, Org. Biomol.
Chem. 2011, 9, 7292–7295; b) D. R. Dreyer, C. W. Bielawski, Chem. Sci.
2011, 2, 1233–1240; c) H.-P. Jia, D. R. Dreyer, C. W. Bielawski, Tetrahedron
2011, 67, 4431–4434; d) H.-P. Jia, D. R. Dreyer, C. W. Bielawski, Adv.
Synth. Catal. 2011, 353, 528–532; e) D. R. Dreyer, H.-P. Jia, C. W. Bielaw-
ski, Angew. Chem. 2010, 122, 6965–6968; Angew. Chem. Int. Ed. 2010,
49, 6813–6816.
[37] S. Ando, J. Nishida, H. Tada, Y. Inoue, S. Tokito, Y. Yamashita, J. Am.
Chem. Soc. 2005, 127, 5336–5337.
[38] E. V. Dehmlow, T. Kelle, Synth. Commun. 1997, 27, 2021–2031.
[19] M. Nagai, R. Isoe, K. Ishiguro, H. Tominaga, M. Shimizu, Chem. Eng. J.
2012, 207–208, 938–942.
Received: April 6, 2013
[20] W.-W. Liu, J.-N. Wang, Chem. Commun. 2011, 47, 6888–6890.
Published online on May 28, 2013
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