Synthesis of 9-ethynyl-9-fluorenol and its derivatives for crystallographic and optical properties study

Article abstract of DOI:10.1016/j.tet.2007.08.029

A series of compounds derived from multifunctional 9-ethynyl-9-fluorenol were synthesized and their structures were characterized by spectroscopic methods. Some derivatives were luminescent with high quantum yields, which might be used as optoelectronic materials based on their optical property investigation.

Full text of DOI:10.1016/j.tet.2007.08.029

Tetrahedron 63 (2007) 11040–11047
Synthesis of 9-ethynyl-9-fluorenol and its derivatives for
crystallographic and optical properties study
*
Jianchuan Ye, Jingyan Ge, Xiaopeng Chen, Zujin Zhao and Ping Lu
Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China
Received 19 June 2007; revised 7 August 2007; accepted 10 August 2007
Available online 14 August 2007
Abstract—A series of compounds derived from multifunctional 9-ethynyl-9-fluorenol were synthesized and their structures were character-
ized by spectroscopic methods. Some derivatives were luminescent with high quantum yields, which might be used as optoelectronic materials
based on their optical property investigation.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
and interesting optoelectronic properties.11 2,7-Dihalo-9-
ethynyl-9-fluorenol is such an intermediate with four func-
tional groups, from which numerous fluorescent organic
compounds could be constructed.
Organic fluorescent compounds are currently attracting
a great deal of attention because of their versatile applica-
tions in the fields of biochemistry, organic electronics, and
supramolecular chemistry. For example, fluorescent temper-
ature sensors,1 solvent polarity sensors,2 metal ions sensors,3
and pH sensors4 are widely applied in biochemistry. Addi-
tionally, in the field of organic electronics, research has
not only focused on the optimization of electroluminescence
cell structure but also on developing new optoelectronic ma-
terials.5 Many of organic molecules have been designed and
synthesized as potential candidates for optoelectronic mate-
rials, such as diarylfluorene derivatives,6 tetra(aryl)silane,7
star shaped truxene or isotruxene derivatives,8 multichromo-
phoric polyphenylene dendrimers,9 polycyclic aromatic
hydrocarbons,10 and so on. One of the reasons for wide ap-
plication of organic fluorescent compounds is the easier
chemical modification of organic structures over inorganic
ones. Therefore, designing new fluorophores with multi-
functional groups are challenging and might open a new
way to obtain unknown organic fluorophores with unique
9-Ethynyl-9-fluorenol and its derivatives were useful com-
pounds in synthetic organic chemistry. They were used for
the synthesis of photochromic material molecules,12 aryl-
substituted cumulenes or extended [4]-radialenes,13 ruthe-
nium carbonyl clusters,14 novel fluorene based host
compounds,15 fluorenyl substituted naphthocyclobutene,
and anthrodicyclobutene derivatives.16 There are hitherto
several synthetic methods leading to 9-ethynyl-9-fluorenol
and its derivatives in literatures. Most of them involve
organometallic reagents, such as sodium acetylide,12b,17 lith-
ium acetylide,18 and ethynylmagnesium bromide19 in which
inert atmosphere reaction conditions could not be avoided.
Here, we would like to report a simple and efficient method
for preparation of 9-ethynyl-9-fluorenol (2a) and its deriva-
tives (Scheme 1). Initially, we would like to have bispiro-
bifluorene framework (A20 in Scheme 1) function as light
Br
Br
X
Y
X
Y
50%NaOH, CEBA, DMSO
OH
1a: X=Y=H
1b: X=H, Y=Br
1c: X=Y=Br
1d: X=H, Y=I
1e: X=Y=I
1f: X=H, Y=NO2
1g: X=Br, Y=NO2
2a: X=Y=H, 79%
2b: X=H, Y=Br, 61%
2c: X=Y=Br, 67%
B
2d: X=H, Y=I, 56%
2e: X=Y=I, 82%
A
2f: X=H, Y=NO2, 49%
2g: X=Br, Y=NO2, 51%
Scheme 1. General procedure for synthesis of 9-ethynyl-9-fluorenol and its derivatives.
* Corresponding author. Tel./fax: +86 571 87952543; e-mail: pinglu@zju.edu.cn
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.08.029

J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
11041
OH
OH
OH
OH
OH
5
4
S
3
8
c
a
f
b
X=Y=H
X=Y=H
OH
X=Y=H
Br
Br
H3CO
OCH3
d
g
e
X
Y
OH
X=Y=Br
X=Y=H
OH
H
CHO
7
6
9
2
Scheme 2. Syntheses of compounds 3–9: (a) 1-iodopyrene, PdCl2(PPh3)2, PPh3, CuI, triethylamine. (b) Iodobenzene, PdCl2(PPh3)2, PPh3, CuI, triethylamine.
(c) 2-Iodothiophene, PdCl2(PPh3)2, PPh3, CuI, triethylamine. (d) Iodobenzene, PdCl2(PPh3)2, PPh3, CuI, triethylamine. (e) 4-Methoxyphenylboronic acid, Pd
(PPh3)4, K2CO3, 18-crown-6, toluene/ethanol. (f) PdCl2(PPh3)2, CuI, I2, i-Pr2NH and (g) TsOH, grinding.
emitting materials in order to investigate and solve the
‘green-emission tail’, which was the key issue in electrolu-
minescene based on polyfluorene emitters. But eventually,
spirofluorene framework (B in Scheme 1) was constructed.21
And the reason for ‘green-emission tail’ was thereby as-
cribed to fluorenone defects by crystallographic analysis
based on those compounds with framework B. Interestingly,
by changing the sequence of sample addition, 9-ethynyl-9-
fluorenol (2a) was obtained in 79% yield. Moreover, from
2a and 2c, some fluorescent compounds with high emission
efficiencies (3–9) (Scheme 2) were constructed in moderate
yields. Optical properties of these synthesized compounds
were investigated and their structure–property relationship
regarding fluorescence is hereby discussed.
of fluorene could be protonated along with the ease of forma-
tion of benzylic cation. Further, the acetylenic group at 9
position of fluorene also allowed for facile formation of var-
ious kinds of compounds (compounds 3, 4, 5, 6, and 8).
Thus, compounds 3–9 were synthesized (Scheme 2) as we
predicted except compound 9. Grinding compound 2a with
either o-dihydroxyphenol or p-dihydroxyphenol catalyzed
by p-TsOH was supposed to form benzopyrans according
to Tanaka’s publication.12a However, neither o-dihydroxy-
phenol nor p-dihydroxyphenol was involved in the product,
2-(9H-fluoren-9-ylidene)acetaldehyde (9). The possible
mechanism is drawn in Scheme 3.
+
+
O
H
O
H
2. Results and discussion
2.1. Synthesis
H+
H
H
O
H
2a
2-Bromo-9H-fluorene (1b),22 2,7-dibromo-9H-fluorene (1c),23
2-iodo-9H-fluorene (1d),24 2,7-diiodo-9H-fluorene (1e),24
2-nitro-9H-fluorene (1f),25 and 2-bromo-7-nitro-9H-fluorine
(1g)26 were prepared by literature procedures. A simple way
to synthesize compounds (2a–2g) is illustrated in Scheme 1.
In this procedure, 50% NaOH aqueous solution was used as
base to generate the acetylenic anion by elimination of 2 M
HBr followed by abstracting the proton from the terminal
triple bond, while a catalytic amount of cetyltrimethyl-
ammonium bromide (CEBA) was used as phase transfer cata-
lyst. In this way, inert atmosphere and acetylene gas could
be avoided. Not only the bare fluorene (1a) could be used
as the starting material, but also fluorene derivatives with
electron withdrawing groups (1b–1g). Yields were moder-
ate, varying from 49% to 82%. Moreover, DMSO played
a key role in this transformation. For instance, when either
DMF or THF was used as solvent instead of DMSO, no
desired product (A, B or 2) was obtained.
H
C
C
C
C
O
H
H
H
H
H
O
H
O
O
H
+
9
H
Scheme 3. Proposed mechanism from 2a to 9.
2.2. X-ray crystallographic analysis: solid-state
conformation and molecular packing
Structures of 2a and 3 were confirmed by X-ray crystallo-
graphic analysis. Single-needle crystal of 2a or 3 suitable
for X-ray diffraction was obtained by very slow evapora-
tion of a CH2Cl2/hexane solution. A numbering guide
and the derived crystal structures are shown in Figures 1
and 2. The selected molecular parameters are provided in
Table S1.
Due to the multifunctionality of 2, many compounds with
versatile applications could be designed and prepared. For
instance, conjugation system could be well extended through
2,7 positions of fluorene by Suzuki or Ullmann reaction
(compound 7 as an example). Hydroxy group at 9 position
Both 2a and 3 crystallize in a monoclinic crystal system with
a centrosymmetric space group P21/c (No. 14). However, the
number of molecule in a unit cell was different. Compound
2a contains 16 molecules in a unit cell, while 3 contains only
4 molecules in a unit cell.

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J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
Figure 1. Left: the molecular structure of 2a with labeling schemes, 30% thermal ellipsoids, and defining planes. Middle: the C–H/p interaction (dashed lines)
between neighboring 2a. Right: the crystal packing of 2a, showing the intermolecular hydrogen bonding (dashed lines). [Symmetry codes: (i) ꢁ1+x,y,z and
(ii) 1+x,y,z].
Figure 2. Left: the molecular structure of 3 with labeling schemes, 30% thermal ellipsoids, and defining planes. Middle: the C–H/p interaction (dashed lines)
between neighboring 3. [Symmetry codes: (iii) ꢁx,1ꢁy,2ꢁz]. Right: the p/p interaction (dashed lines) between neighboring 3. [Symmetry code:
(iv) ꢁx,1ꢁy,1ꢁz].
Several CH/p interactions occur in compound 2a, which
are shown in Figure 1 (middle). The H(4)/Cg(8) separation
(Cg(8) is the centroid of C21 benzene riꢀng) and C(4)–H(4)/
No face-to-face intermolecular p interaction between fluo-
rene groups was observed in the orientational stacking of
compound 2a. The major two effects are CH/p and hydro-
gen bonding intermolecular attractions.
˚
Cg(8) angle are 3.35 A and 177.15 , respectively. The
H(8)/Cg(7) separation (Cg(7) is the centroid of the C16
˚
benzene ring) and C(8)–H(8)/Cg(7) angle are 3.15 A and
The CH/p interactions also occur in compound 3, which is
shown in Figure 2 (middle). The H(1)/Cg(7) separation
(Cg(7) is the centroid of P5) and O(1)–H(1)/Cg(7) angle
131.25ꢀ, respectively. The H(16)/Cg(12) separation
(Cg(12) is the centroid of the C51 benzene ring) and
ꢀ
ꢀ
˚
˚
C(16)–H(16)/Cg(12) angle are 2.86 A and 156.17 , re-
spectively. The H(30)/Cg(11) separation (Cg(11) is the
centroid of the C46 benzene ring) and C(30)–H(30)/
are 2.58 A and 171.00 , respectively. The H(6)/Cg(5) sepa-
ration (Cg(5) is the centroid of P6) and C(6)–H(6)/Cg(5)
ꢀ
˚
angle are 2.65 A and 148.37 , respectively [symmetry code:
(iii) ꢁx,1ꢁy,2ꢁz]. According to the calculated result, no hy-
drogen bonding exists in 3. As shown in Figure 2 (right), the
pyrene groups of the neighboring compounds (3) were paral-
lel to reach thecofacial arrangement and thedistancebetween
ꢀ
˚
Cg(11) angle are 3.24 A and 98.95 , respectively. The
H(45)/Cg(6) separation (Cg(6) is the centroid of the C1
˚
benzene ring) and C(45)–H(45)/Cg(6) angle are 3.14 A
and 92.42ꢀ, respectively. Neighboring complexes are linked
˚
˚
to each other via an O(1)–H(10)/O(2) hydrogen bonding
them was 3.30 A (less than 3.60 A). Therefore, the major two
effects are CH/p and p/p intermolecular attractions.
˚
with the separation 2.74 A [symmetry code: (i) ꢁ1+x,y,z]
and an O(4)–H(40)/O(3) hydrogen bonding with the sepa-
˚
ration 2.82 A [symmetry code: (ii) 1+x,y,z] to form a
supramolecule.
Although the stabilization arising from a single intermole-
cular CH/p interaction or hydrogen bonding is weak, the

J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
11043
sum of multiple intermolecular CH/p interaction or hydro-
2a
3
1.0
0.8
0.6
0.4
0.2
0.0
gen bonding can become significant. In addition, they may
influence the optical properties of materials, especially for
organic molecules bearing p-groups.27
2.3. Optical properties
Solvents used in spectroscopic measurements were spec-
trograde and purified by distillation before use. The absorp-
tion and emission spectra of 2a–9 in solutions were
measured in THF with a concentration of 10ꢁ6 M. All
absorption and emission properties in THF solutions are
summarized in Table 1.
250 275 300 325 350 375 400 425 450 475 500
Wavelength (nm)
Generally speaking, maximum absorption wavelengths
obtained from spectroscopic recording were related to the
energy gap (ELUMOꢁEHOMO) calculated by PM3 method
to a certain extent (Table 1). The larger energy gap was,
the shorter maximum absorption wavelength observed.
Figure 3. Normalized absorption and fluorescence spectra of 2a and 3 in
THF.
In THF solutions, absorption and emission spectra of 2a and
3 are given in Figure 3. Maximum absorption wavelengths
for them were 276 nm and 366 nm, respectively, while the
maximum emission wavelengths for them were 312 nm
and 383 nm, respectively. Absorption of 2a was the typical
fluorene absorption, that of 3 was the simple combination
of absorptions of fluorene and pyrene due to the interruption
of sp3 hybridized carbon. Absorption and emission of 2a
were structureless, while those of 3 were vibronic. Com-
pound 3 gave a smaller Stokes’ shift.
10
1.0
3
0.8
0.6
0.4
0.2
0.0
In order to investigate the structure–property relationship of
optical properties, the absorption and emission spectra of 3
were compared with those of 1-ethynylpyrene (10), which
were prepared by literature procedure.29 As shown in
Figure 4, absorption spectrum of 3 was red-shifted compared
to that of 10, while emission spectra of both were nearly the
same. In a word, the emission of 3 could be simply ascribed
to the emission from pyrene and presented a single mole-
cular emission in its dilute solution.
250
275
300
325
350
375
Wavelength (nm)
400
425
450
475
Figure 4. Normalized absorption and fluorescence spectra of 3 and 10 in
THF.
molecular packing played a critical role in emission charac-
ter. As the molecule got closer, from dilute solution (C¼
1ꢂ10ꢁ5 M) (3–THF–LC in Fig. 5) to highly concentrated
solution (C¼2ꢂ10ꢁ3 M) (3–THF–HC in Fig. 6), to film (3-
film in Fig. 5) or powder (3-powder in Fig. 5), and finally
It is important to survey the emission performance in solid
state because the real state for their functions as optoelectron-
ics materials is the solid state. By examining emissions from
thin film, powder, and crystal of 3 it was noticeable that
Table 1. Optical properties of compounds
Compounds
Abs. (nm)
)
Em.
(nm)
Quantum
yield F (%)
Stokes’
shift (nm)
HOMOd
(eV)
LUMOd
(eV)
Gapd
(eV)
mg
(D)d
Tm
(ꢀC)
Td
e
e
(3ꢂ10ꢁ4
(ꢀC)
2a
3
4
5
6
7
8
9
10
276 (1.19)
366 (3.70)
251 (1.21)
275 (2.47)
291 (1.90)
333 (3.45)
269 (1.81)
267 (3.70)
358
312
0.44b
13.29a
3.43b
0.36b
6.96c
19.5a
0.24b
0.54b
22.19a
36
40
69
37
58
54
53
46
25
ꢁ8.95
ꢁ8.25
ꢁ9.02
ꢁ9.05
ꢁ9.18
ꢁ8.51
ꢁ8.94
ꢁ9.15
ꢁ8.23
ꢁ0.47
ꢁ1.24
ꢁ0.55
ꢁ0.58
ꢁ0.88
ꢁ0.74
ꢁ0.60
ꢁ1.31
ꢁ1.12
8.48
7.01
8.47
8.47
8.30
7.77
8.34
7.84
7.11
1.41
1.73
1.38
2.00
1.78
1.18
2.10
3.25
0.14
106.1
184.7
81.4
101.4
173.6
204.8
—
—
383, 406
320
312
349
387
322
313
383
292.8
244.2
267.8
278.4
323.0
144.3
—
115.9
—
—
Quantum yields were calculated on the basis of 9,10-diphenylanthracene as standard (F¼1.0 in cyclohexane).28
Quantum yields were calculated on the basis of 1,4-diphenylbutadiene (F¼0.42 in hexane).28
The energy level of HOMO or LUMO and the ground-state dipole moment is calculated by PM3 method.
a
Quantum yields were calculated on the basis of p-terphenyl (F¼0.93 in cyclohexane).28
b
c
d
e
¨
Melting points of 2a and 9 were recorded on a BUCHI 535. Others were measured by DSC. Decomposition temperatures were measured by TGA.

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J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
4. Experimental
3-THF-LC
3-THF-HC
1.0
4.1. General methods
3-film
0.8
0.6
0.4
0.2
0.0
3-powder
3-crystal
1H and 13C NMR spectra were obtained on a Bruker
AVANCE DMX500 spectrometer operating in the FT
mode. Five percent w/v solutions in chloroform-d or
DMSO-d were used to obtain NMR spectra. TMS was
used as an internal standard. Hewlett Packard 5989B elec-
tron impact mass spectrometer with 70 eV and IonSpec
HiResMALDI were used to obtain mass spectra. Melting
¨
points were recorded on a BUCHI 535. Fluorescence mea-
surements were made with a RF-5301pc spectrofluorometer
(Shimadzu, Kyoto, Japan) equipped with a xenon lamp. UV–
vis absorption spectra were recorded on Shimadzu UV-2450
spectrophotometer. NETZSCH STA 409 PG/PC was used to
measure the thermal performances of the compounds. Sol-
vents were distilled before use. Commercially available
reagents were used without further purification unless other-
wise stated.
350
400
450
500
Wavelength (nm)
550
600
650
Figure 5. Normalizedemissionspectraof3indifferentexistingapprearances.
7
100
XRD measurements were carried out at room temperature
on a rotating-anode Rigaku RASIX-RAPID diffractometer
by using graphite-monochromated Mo Ka radiation (l¼
80
60
40
20
0
˚
0.71073 A). Measurements for 2a and 3 were carried out
on a charge-coupled device (CCD) area detector diffracto-
meter under the same conditions. In these two cases, inten-
sity data were collected in the u scan mode. Crystal
structure of 2a was solved by direct methods where the
SIR92 program was used,31 while the crystal structure of
compound 3 was solved by the SIR97 program.32
4.1.1. General procedure for synthesis of 9-ethynyl-9-
fluorenol derivatives (2). 1,2-Dibromoethane (25 mmol),
12.5 mL of 50% NaOH aqueous solution, and a catalytic
amount of CEBA in 80 mL DMSO were mixed at room tem-
perature, the solution of fluorene derivative (5 mmol) in
30 mL DMSO was added drop wise. After solution was
stirred vigorously at room temperature for 10 h, the mixture
was poured into water and extracted with dichloromethane
(30 mLꢂ3), The organic layers were combined, washed
with water, and dried over anhydrous MgSO4. After filtra-
tion, filtrate was evaporated under reduced pressure. The
crude products were purified through column chromato-
graphy (silica gel, n-hexane/dichloromethane as eluent).
In this way, the 9-ethynyl-9-fluorenol derivatives were
obtained.
0
100
200
300
400
Temperature (°C)
500
600
700
800
Figure 6. TGA chart of compound 7 in N2 at the heating rate of 10 ꢀC/min.
to crystal (3-crystal in Fig. 5), the excimer emissions30 of 3
were gradually red-shifted. The more oriented molecular
packing was, the more red-shifted emission observed.
2.4. Thermal stabilities
Thermal stabilities of the compounds (3–8) were measured
by the DSC and TGA analyses. Melting points of these com-
pounds were obtained and listed in Table 1. TGA analysis
showed that these compounds exhibited decomposition tem-
peratures (Td) in the range of 244.2–323.0 ꢀC with 5%
weight loss excepted for 8 (Table 1). TGA chart of 7 is given
in Figure 6 as an example.
4.1.1.1. 9-Ethynyl-9-fluorenol (2a). Application of
above procedure to fluorene (1a) (831 mg, 5 mmol) afforded
compound 2a (815 mg, 79%) as a white solid: mp 105.7–
1
106.4 ꢀC. H NMR d CDCl3: 2.47 (s, 1H, C^CH), 2.59
(s, 1H, OH), 7.36 (t, 2H, J¼7.5 Hz), 7.41 (t, 2H,
J¼7.5 Hz), 7.61 (d, 2H, J¼7.5 Hz), 7.70 (d, 2H,
J¼7.5 Hz) ppm; 1H NMR d CDCl3/D2O: 2.48 (s, 1H),
7.36 (t, 2H, J¼7.4 Hz), 7.41 (t, 2H, J¼7.5 Hz), 7.62 (d,
2H, J¼8.0 Hz), 7.71 (d, 2H, J¼7.5 Hz) ppm; 13C NMR
d CDCl3: 71.60, 74.80, 84.07, 120.48, 124.48, 128.86,
130.10, 139.34, 146.82 ppm. MS (ESI) (m/z): calcd for
C15H10O: 206.2, found: 228.7 (100%, M+Na+).
3. Conclusion
In conclusion, we described a facile synthetic route to
9-ethynyl-9-fluorenol. Several fluorescent compounds de-
rived from it were thereafter synthesized. Emission proper-
ties were not only relative to the molecular structure, but
also molecular packing. Further studies about their fluores-
cent applications are under investigation.
4.1.1.2. 2-Bromo-9-ethynyl-9H-fluoren-9-ol (2b). Ap-
plication of above procedure to 2-bromo-9H-fluorene (1b)

J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
11045
(123 mg, 0.5 mmol) afforded compound 2b (87 mg, 61%) as
a pale yellow solid: mp 128.1–128.9 ꢀC. 1H NMR d CDCl3:
2.48 (s, 1H, C^CH), 2.74 (s, 1H, OH), 7.37 (m, 2H), 7.44 (d,
1H, J¼8.0 Hz), 7.51 (dd, 1H, J1¼8.0 Hz and J2¼1.5 Hz),
7.56 (d, 1H, J¼6.5 Hz), 7.66 (d, 1H, J¼7.0 Hz), 7.81 (d,
1H, J¼1.5 Hz) ppm; 13C NMR d CDCl3: 72.27, 74.45,
83.36, 120.55, 121.81, 122.36, 124.54, 128.04, 129.23,
130.29, 133.12, 138.28, 138.32, 146.46, 148.62 ppm. MS
(ESI) (m/z): calcd for C15H9BrO: 284.0, found: 306.7
(91.7%, M+Na+), 308.7 (100%, M+2+Na+).
7.60 (dd, 2H, J1¼25.5 Hz, J2¼8.0 Hz), 7.72 (d, 1H,
J¼8.5 Hz), 7.90 (s, 1H), 8.33 (d, 1H, J¼7.0 Hz), 8.53 (s,
1H) ppm; 13C NMR d CDCl3: 73.57, 73.92, 82.00, 120.41,
120.88, 123.12, 124.90, 126.31, 128.55, 133.86, 135.96,
144.70, 147.75, 148.47, 149.71 ppm. MS (ESI) (m/z): calcd
for C15H8BrNO3: 329.0, found: 351.7 (100%, M+Na+).
353.7 (66.7%, M+2+Na+).
4.1.1.8. 9-(Pyren-1-ylethynyl)-9H-fluoren-9-ol (3).
Compound 2a (206 mg, 1 mmol), 1-iodopyrene (328 mg,
1 mmol), cuprous iodide (10 mg, 0.05 mmol), dichlorobis-
(triphenylphosphine)palladium(II) (3.5 mg, 0.005 mmol),
triphenylphosphine (5 mg, 0.02 mmol), and dry triethyl-
amine 100 mL were placed in a 150-mL round bottle flask
equipped with a Teflon covered magnetic stir bar. After the
solution was purged with nitrogen for half an hour, it was
refluxed under nitrogen for 4 h. The reaction mixture was
filtered and filtrate was evaporated under reduced pressure.
The residue was purified through column chromatography
(silica gel, hexane/dichloromethane as eluent). In this way,
305 mg (75% yield) of 3 was obtained as a yellow solid:
4.1.1.3. 2,7-Dibromo-9-ethynyl-9H-fluoren-9-ol (2c).
Application of above procedure to 2,7-dibromo-9H-fluorene
(1c) (162 mg, 0.5 mmol) afforded compound 2c (122 mg,
1
67%) as a pale yellow solid: mp 199.7–200.8 ꢀC. H NMR
d CDCl3: 2.55 (s, 1H, C^CH), 2.63 (s, 1H, OH), 7.46
(d, 2H, J¼8.0 Hz), 7.54 (dd, 2H, J1¼8.0 Hz, J2¼1.5 Hz),
7.82 (d, 2H, J¼1.5 Hz) ppm; 13C NMR d CDCl3: 72.97,
74.25, 82.86, 121.92, 122.84, 128.14, 133.40, 137.34,
148.29 ppm. MS (ESI) (m/z): calcd for C15H8Br2O: 361.9,
found: 384.6 (44.7%, M+Na+), 386.6 (100%, M+2+Na+),
388.5 (36.7%, M+4+Na+).
1
mp 184.7 ꢀC. H NMR d CDCl3: 2.83 (s, 1H), 7.40–7.45
(m, 4H), 7.66 (d, 2H, J¼7.0 Hz), 7.92–8.05 (m, 8H), 8.11–
8.13 (m, 2H), 8.40 (d, 1H, J¼8.5 Hz) ppm; 13C NMR
d CDCl3: 75.88, 82.66, 94.80, 116.97, 120.61, 124.40,
124.51, 124.71, 125.55, 125.81, 125.87, 126.41, 127.39,
128.48, 128.66, 128.97, 130.03, 130.18, 131.19, 131.38,
131.67, 132.60, 139.45, 147.60 ppm. MS (MALDI) (m/z):
calcd for C31H18O: 406.1, found: 406.2 (100%, M+).
4.1.1.4. 9-Ethynyl-2-iodo-9H-fluoren-9-ol (2d). Appli-
cation of above procedure to 2-iodo-9H-fluorene (1d)
(146 mg, 0.5 mmol) afforded compound 2d (93 mg, 56%)
as a dark yellow solid: mp 135.8–137.4 ꢀC; 1H NMR
d CDCl3: 2.50 (s, 1H, C^CH), 2.64 (s, 1H, OH), 7.38 (m,
3H), 7.58 (m, 1H), 7.67 (m, 1H), 7.72 (dd, 1H, J1¼8.0 Hz,
J2¼1.5 Hz), 8.02 (d, 1H, J¼1.5 Hz) ppm; 13C NMR
d CDCl3: 72.28, 74.38, 83.40, 93.62, 120.61, 122.14,
124.49, 129.43, 130.30, 133.85, 138.43, 138.95, 139.05,
146.29, 148.73 ppm. MS (ESI) (m/z): calcd for C15H9IO:
332.0, found: 354.8 (100%, M+Na+).
4.1.1.9. 9-(Phenylethynyl)-9H-fluoren-9-ol (4).33 Com-
pound 4 was prepared by a similar method as the preparation
of 3. When 2a (824 mg, 4 mmol) was reacted with iodo-
benzene (816 mg, 4 mmol) and purified through column
chromatography (silica gel, n-hexane/dichloromethane as
eluent), 903 mg (80% yield) of 4 was obtained as a brown
4.1.1.5. 9-Ethynyl-2,7-diiodo-9H-fluoren-9-ol (2e). Ap-
plication of above procedure to 2,7-diiodo-9H-fluorene (1e)
(209 mg, 0.5 mmol) afforded compound 2e (188 mg, 82%)
1
solid: mp 81.4 ꢀC. H NMR d CDCl3: 2.73 (s, 1H), 7.20–
7.25 (m, 3H), 7.30–7.33 (m, 2H), 7.35–7.40 (m, 4H), 7.59
(d, 2H, J¼7.0 Hz), 7.74 (d, 2H, J¼7.5 Hz) ppm.
1
as a yellow solid: mp 236.3–237.1 ꢀC. H NMR d CDCl3:
2.55 (s, 1H, C^CH), 2.61 (s, 1H, OH), 7.33 (d, 2H,
J¼8.5 Hz), 7.74 (dd, 2H, J1¼7.8 Hz, J2¼1.8 Hz), 8.01 (d,
2H, J¼1.5 Hz) ppm; 13C NMR d CDCl3: 72.99, 74.06,
82.71, 94.22, 122.23, 133.85, 138.05, 139.29, 148.09 ppm.
MS (ESI) (m/z): calcd for C15H8I2O: 457.9, found: 456.7
(100%, (Mꢁ1)+).
4.1.1.10.
9-(Thiophen-2-ylethynyl)-9H-fluoren-9-ol
(5). Compound 5 was prepared by a similar method as the
preparation of 3. When 2a (206 mg, 1 mmol) was reacted
with 2-iodothiophene (210 mg, 1 mmol) and purified
through column chromatography (silica gel, n-hexane/
dichloromethane as eluent), 236 mg of 5 (82% yield) was
obtained as a brown solid: mp 101.4 ꢀC. 1H NMR
d CDCl3: 2.83 (s, 1H), 6.84–6.86 (m, 1H), 7.13–7.15 (m,
2H), 7.27–7.35 (m, 4H), 7.55 (d, 2H, J¼7.5 Hz), 7.69 (d,
2H, J¼7.5 Hz) ppm; 13C NMR d CDCl3: 75.40, 76.61,
92.93, 120.38, 122.41, 124.59, 127.02, 127.64, 128.74,
129.87, 132.92, 139.15, 146.95 ppm; MS (ESI) (m/z): calcd
for C19H12OS: 288.4, found: 311.0 (100%, M+Na+).
4.1.1.6. 9-Ethynyl-2-nitro-9H-fluoren-9-ol (2f). Appli-
cation of above procedure to 2-nitro-9H-fluorene (1f)
(106 mg, 0.5 mmol) afforded compound 2f (62 mg, 49%)
1
as a brown solid: mp 171.9–173.5 ꢀC. H NMR d CDCl3:
2.56 (s, 1H, C^CH), 2.81 (s, 1H, OH), 7.49–7.50 (m,
2H), 7.71–7.77 (m, 3H), 8.33 (dd, 1H, J1¼15.8 Hz,
J2¼2.3 Hz), 8.56 (d, 1H, J¼1.5 Hz) ppm; 13C NMR
d CDCl3: 72.90, 74.29, 82.62, 120.36, 120.76, 121.88,
124.92, 126.16, 130.72, 130.95, 137.06, 145.67, 148.05,
148.08, 148.31 ppm. MS (ESI) (m/z): calcd for C15H9NO3:
251.1, found: 273.8 (100%, M+Na+).
4.1.1.11. 2,7-Dibromo-9-(phenylethynyl)-9H-fluoren-
9-ol (6). Compound 6 was prepared by a similar method as
the preparation of 3. When 2c (728 mg, 2 mmol) was reacted
with iodobenzene (408 mg, 2 mmol) and purified through
column chromatography (silica gel, n-hexane/dichloro-
methane as eluent), 687 mg of 6 (78% yield) was obtained
as a yellow solid: mp 173.6 ꢀC. 1H NMR d CDCl3: 2.70 (s,
1H), 7.28–7.34 (m, 3H), 7.43–7.46 (m, 3H), 7.47 (s, 1H),
7.53 (d, 1H, J¼1.5 Hz), 7.55 (d, 1H, J¼2.0 Hz), 7.87 (d,
4.1.1.7. 2-Bromo-9-ethynyl-7-nitro-9H-fluoren-9-ol
(2g). Application of above procedure to 2-bromo-7-nitro-
9H-fluorene (1g) (145 mg, 0.5 mmol) afforded compound
1
2g (84 mg, 51%) as a brown solid: mp 206.9–208.3 ꢀC. H
NMR d CDCl3: 2.60 (s, 1H, C^CH), 2.92 (s, 1H, OH),

11046
J. Ye et al. / Tetrahedron 63 (2007) 11040–11047
2H, J¼1.5 Hz) ppm; 13C NMR d CDCl3: 74.92, 84.61,
87.59, 121.93, 122.82, 128.18, 128.56, 129.23, 132.27,
133.25, 137.29, 148.89 ppm. MS (ESI) (m/z): calcd for
C21H12Br2O: 437.9, found: 436.7 (47.7%, (Mꢁ1)+), 438.8
(100%, (M+1)+), 440.7 (33.2%, (M+3)+).
Supplementary data
Supplementary data associated with this article can be found
in the online version, at doi:10.1016/j.tet.2007.08.029.
References and notes
4.1.1.12. 2,7-Bis(4-methoxyphenyl)-9-(phenylethynyl)-
9H-fluoren-9-ol (7). A mixture of 6 (330 mg, 0.75 mmol),
4-methoxyphenylboronic acid (342 mg, 2.25 mmol), K2CO3
(1.05 g, 7.5 mmol), and Pd(PPh3)4 (10 mg, 0.08 mmol) in
70 mL toluene/ethanol (10:1, v/v) was refluxed for 40 h.34
After cooling and filtering, the filtrate was evaporated under
reduced pressure. The crude products were purified through
column chromatography (silica gel, n-hexane/dichloro-
methane as eluent). In this way, 260 mg (70% yield) of 7
was obtained as a dark yellow solid: mp 204.8 ꢀC. 1H
NMR d CDCl3: 2.70 (s, 1H), 3.86 (s, 6H), 7.00 (d, 4H,
J¼8.5 Hz), 7.24–7.28 (m, 3H), 7.43–7.45 (m, 2H), 7.61–
7.63 (m, 6H), 7.67 (s, 1H), 7.69 (s, 1H), 7.98 (d, 2H,
J¼1.0 Hz) ppm; 13C NMR d CDCl3: 55.61, 75.49, 83.69,
89.13, 114.53, 120.74, 122.54, 122.91, 128.37, 128.40,
128.46, 128.78, 132.22, 133.55, 137.58, 141.47, 148.32,
159.56 ppm. MS (MALDI) (m/z): calcd for C35H26O3:
494.2, found: 492.7 (100%, (Mꢁ1)+).
4.1.1.13. 9,90-(Buta-1,3-diyne-1,4-diyl)bis(9H-fluoren-
9-ol) (8).12a,35 Compound 2a (206 mg, 1 mmol), cuprous
iodide (10 mg, 0.05 mmol), dichlorobis(triphenylphos-
phine)palladium(II) (10 mg, 0.015 mmol), I2 (126 mg,
0.5 mmol), and dry i-Pr2NH (80 mL) were placed in
a 150-mL round bottle flask equipped with a Teflon covered
magnetic stir bar.36 The mixture was stirred at room temper-
ature for 6 h and then poured into 50 mL of water with some
sodium bisulfite. The mixture was extracted with dichloro-
methane (20 mLꢂ3). Solvent was removed by evaporation.
The residue was purified through column chromatography
(silica gel, n-hexane/ethyl acetate as eluent), 152 mg of 8
(yield, 74%) was obtained as a brown solid. 1H NMR
d (CD3)2SO: 6.86 (s, 2H), 7.34 (t, 4H, J¼7.5 Hz), 7.42 (t,
4H, J¼7.5 Hz), 7.60 (d, 4H, J¼7.5 Hz), 7.78 (d, 4H,
J¼7.5 Hz) ppm.
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ꢀ
ꢀ
4.1.1.14. 2-(9H-Fluoren-9-ylidene)acetaldehyde (9). A
mixture of 2a (330 mg, 1.6 mmol), p-TsOH (0.1 equiv),
and a small amount of silica gel was well ground for
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Acknowledgements
P.L. thanks National Nature Science Foundation of China
(20674070) and Natural Science Foundation of Zhejiang
Province for financial supports (R404109).
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