Two-photon absorption and effective optical power-limiting properties of small dendritic chromophores derived from functionalized fluorene/oxadiazole units

Tetrahedron 68 (2012) 4935e4949

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Tetrahedron

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Two-photon absorption and effective optical power-limiting properties of small

dendritic chromophores derived from functionalized ﬂuorene/oxadiazole units

*

Tzu-Chau Lin , Ying-Hsuan Lee, Bor-Rong Huang, Chia-Ling Hu, Yu-Kai Li

Photonic Materials Research Laboratory, Department of Chemistry, National Central University, Jhong-Li 32001, Taiwan

a r t i c l e i n f o

a b s t r a c t

Article history:

A set of novel multi-branched chromophores composed of four analogues with generic skeletons of

Received 10 December 2011

Received in revised form 17 April 2012

Accepted 20 April 2012

donor-p-acceptor (D-p-A) derived from functionalized ﬂuorene/oxadiazole moieties has been synthe-

sized and experimentally shown to possess strong and wide-dispersed two-photon absorptivities in near

infrared (NIR) region under the irradiation of femtosecond laser pulses. It is demonstrated that structural

Available online 27 April 2012

parameters, such as the size of

p-framework and the number of electron-donating units attached are

closely connected to the molecular two-photon activities of these model compounds. Effective optical

power-attenuation behaviors in the nanosecond time domain of the studied chromophores were also

investigated and the results indicate that such dye molecules can be potential materials as broadband

and quick-responsive optical-limiters especially against those laser lights with longer pulses.

Keywords:

Two-photon absorption

Two-photon-excited ﬂuorescence

Dendritic structure

Optical power-limiting

Fluorene

Oxadiazole

1. Introduction

molecular 2PA may also be required for the designed molecules

because of various practical needs. For instance, in the case of op-

Two-photon absorption (2PA) phenomenon was theoretically

tical power-limiting in nanosecond regime, compounds with ex-

tended excited-state lifetime may beneﬁt the apparent nonlinear

absorption due to two-photon-assisted excited-state absorption

(2PA-assisted ESA)¹⁰and can be used as optical power-limiters

against long laser pulses. In searching the connection between

structural parameters and two-photon absorption properties in

conjugated systems, we are interested in exploring the inﬂuence

that may be caused by the electronic properties of the selected

1

€

predicted by Maria Goppert-Mayer in 1931, but its experimental

evidence came out about thirty years later when scientists ob-

served up-converted emission from the media under the irradia-

tion of laser light with wavelengths far from the linear absorption

bands of the studied media.²In conjunction with the intrinsic

quadratic dependence of the incident light intensity in this non-

linear optical process, numerous 2PA-based photonic and bio-

photonic applications have been proposed and explored including

optical power-limiting, frequency up-converted lasing, 3-D data

storage, 3-D microfabrication, nondestructive bio-imaging and

tracking, and two-photon photodynamic therapy.³In order to be

applicable in these applications, organic compounds that exhibit

large 2PA within desired spectral region are consequently in great

demand. So far, it has been realized that molecular 2PA is related to

the combination of several structural parameters, such as intra-

building units and the number of

when constructing multi-branched

p

-branches on the molecular 2PA

-frameworks. In this paper we

p

present the synthesis of a new series of two-photon-active model

chromophores (1e4) derived from functionalized ﬂuorene and

oxadiazole moieties as well as the initial investigations of their 2PA-

related properties both in the femtosecond and nanosecond time

domains.

molecular charge-transfer efﬁciency and/or effective size of

p-

conjugation domain within a molecule.^4e9Depending on the ap-

plication, other photophysical properties in addition to strong

2. Results and discussion

2.1. Molecular structures and syntheses

The chemical structures and the synthetic routes toward the

studied model compounds are illustrated in Fig. 1 and Schemes

1e3. This model compound set contains four structural congeners

with one possessing quasi-linear type structure (compound 1) and

* Corresponding author. Tel.: þ886 3 4227251x65925; fax: þ886 3 4227402;

e-mail address: tclin@ncu.edu.tw (T.-C. Lin).

doi:10.1016/j.tet.2012.04.073

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T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

O

N

C₆H₁₃C₆H₁₃

1

N

C₆H₁₃

N

C₆H₁₃

O

N

C₆H₁₃

C₆H₁₃C₆H₁₃

C₆H₁₃

N

2

N

C₆H₁₃

N

O

N

C₆H₁₃

N

C₆H₁₃

C₆H₁₃C₆H₁₃

C₆H₁₃

N

C₆H₁₃

N

C₆H₁₃

N

C₆H₁₃

N

C₆H₁₃

C₆H₁₃C₆H₁₃

C₆H₁₃

4

C₆H₁₃

O

C₆H₁₃

N

C₆H₁₃

C₆H₁₃C₆H₁₃

N

C₆H₁₃

N

C₆H₁₃

N

C₆H₁₃

C₆H₁₃C₆H₁₃

C₆H₁₃

3

C₆H₁₃

N

Fig. 1. Molecular structures of the studied chromophores in this work.

other three having multi-branched skeleton (compounds 2e4). All

these compounds are with generic structure of donor- -acceptor

(D- -A) using functionalized ﬂuorene and oxadiazole units to

construct their unsymmetric backbones with different numbers of

-branches. The original design concept of these model com-

pounds is to tentatively construct a set of structurally unsymmetric

-frameworks with various numbers of electron-donating units

attached so that the resulting ﬂuorophores may possess multi-

polar character and different manners of charge-transfer/

redistribution upon light excitation. On the other hand, the pen-

dent alkyl chains on all ﬂuorenyl moieties in these chromophores

are expected to enhance their solubility in common organic sol-

vents and this is indeed another important parameter to be con-

sidered in the molecular design from either the aspect of

experiments or applications. The synthetic procedures toward

these model dye molecules are relatively straightforward, which

majorly involve consecutive functionalization processes on the

ﬂuorene moiety and BuchwaldeHartwig type amination to prepare

the key intermediates and the ﬁnal model compounds as shown in

Schemes 1e3. The detailed syntheses including the preparation of

the key intermediates (8, 10, 13, 16, 21, and 22) and the ﬁnal cata-

lytic coupling reactions to accomplish the targeted compounds are

described in the Experimental section.

2.2. Optical properties characterization

p

2.2.1. One-photon absorption (1PA) and ﬂuorescence spectra meas-

urement. Fig. 2 presents the linear absorption and ﬂuorescence

spectra of the studied dye molecules in solution phase using THF as

the solvent. Intense one-photon absorption (1PA) was found around

p

385 nm for compound 1 (with ε_maxw5.1ꢀ10⁴cm^ꢁ1

M

^ꢁ1) and

400 nm for compounds 2e4 (with ε_maxw1.01ꢀ10⁵cm^ꢁ1M^ꢁ1for 2,

ε_maxw2.17ꢀ10⁵cm^ꢁ1M^ꢁ1for 3, and ε_maxw3.77ꢀ10⁵cm^ꢁ1M^ꢁ1for

4). All the studied chromophore solutions emit visible ﬂuorescence

under the irradiation of a common UV-lamp with blue color for

compound 1 and greenish-blue for compounds 2e4.

2.2.2. Two-photon-excited ﬂuorescence (2PEF) emission proper-

ties. The studied model chromophores also manifest intense two-

photon-excited upconversion emission which can be easily ob-

served by naked eyes even under the illumination of an w790 nm

unfocused femtosecond laser beam at low intensity level. Fig. 3(a)

illustrates the 2PA-induced ﬂuorescence spectra of these model

chromophores in solution phase. The sample solutions were freshly

prepared at concentration of 1ꢀ10^ꢁ4M in THF for this measurement

and the excitation source utilized for this two-photon induced ﬂuo-

rescence study is from a mode-locked Ti:Sapphire laser (Tsunami

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4937

Scheme 1. The synthetic routes toward each electron-donating intermediate for the construction of the studied chromophores.

pumped with a Millennia 10W, Spectra-Physics), which delivers

w80 fs pulses with the repetition rate of 80 MHz and the beam di-

ameter of 2 mm. The intensity level of the excitation beam was

carefully controlled in order to avoid the saturation of absorption and

photodegradation. To minimize the effect of re-absorption due to the

relatively high concentration of the sample solution used in this

measurement, we have focused the excitation beam as close as pos-

sible to the wall of the quartz cell (5 mmꢀ5 mm cuvette) so that only

the emission from the surface of the sample was recorded. It can be

seen in Fig. 3(a) that for each studied chromophore the shape and

spectral position of measured 2PA-induced emission is basically

identical to its corresponding 1PA-induced ﬂuorescence band shown

in Fig. 1. This result implies that in our dye system the radiative re-

laxation processes occurred within the studied samples are from the

same ﬁnal excited-states regardless of the excitation method.

the measured data and the results conﬁrm that 2PA process is re-

sponsible for the observed up-converted ﬂuorescence emissions in

all cases.

The temporal behavior and lifetime of 2PA-induced ﬂuorescence

of the same sample solutions were also probed based on the time-

correlated single photon counting (TCSPC) technique using a highly

sensitive photomultiplier equipped with accumulating real-time

processor as the detection system (PMA-182 and TimeHarp 200,

PicoQuant). The same Ti:Sapphire laser system (vide supra) was

employed for this experiment. The measured 2PA-induced ﬂuo-

rescence decay curves of the studied compound solutions are

depicted in Fig. 3(f). Theoretical ﬁtting of each decay curve by

single-exponential dependence has revealed that these ﬂuo-

rophores exhibit ﬂuorescence lifetime ranging from 2.2 ns to 3.3 ns

and these data are collected in Table 1.

The power-squared dependence of the 2PA-induced ﬂuores-

cence intensity on the excitation intensity of the studied ﬂuo-

rophores were also examined. Fig. 3(b)e(e) are logarithmic plots of

2.2.3. Degenerate two-photon absorption spectra measurement. In

order to probe and compare the dispersion of 2PA behaviors of

4938

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

AcOH

C₆H₁₃C₆H₁₃

CuCN

DMF

C₆H₁₃C₆H₁₃

H₂SO₄

H₂O

MeOH

H₂SO₄

C₆H₁₃C₆H₁₃

O

Br

CN

Br

OH

OCH₃

17

18

5

19

C₆H₁₃

N N

O

C₆H₁₃

C₆H₁₃C₆H₁₃

(1) t-butyl benzoyl

chloride, THF

N₂H₄.H₂O

MeOH

O

Br

NHNH₂

(2) POCl₃,

21

20

(1)

13

Pd₂(dba)₃

P(t-Bu)₃

NaOtBu

toluene

I

C₆H₁₃

(2)

ICl

C₆H₁₃

N N

O

CH₂Cl₂

C₆H₁₃

0^oC

N

C₆H₁₃

22

I

Scheme 2. The synthesis of the major electron-pulling

p-bridges.

4.5

O

toluene

1

2

8

+

1

2

3

4

Cl

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

1.2x10

1.0x10

8.0x10

6.0x10

4.0x10

2.0x10

21

10

Pd₂(dba)₃

P(t-Bu)₃

NaOtBu

toluene

16

3

4

0.0

400 450 500 550 600 650 700 750

Pd₂(dba)₃

P(t-Bu)₃

NaOtBu

Wavelength (nm)

22

+

toluene

300 400 500 600 700 800 900 1000 1100

Wavelength (nm)

Scheme 3. Coupling reactions toward targeted ﬂuorophores.

Fig. 2. Linear absorption and ﬂuorescence spectra (see the inset) of compounds 1e4 in

solution phase (1ꢀ10^ꢁ5M in THF).

these dye molecules across the wavelengths, we have conducted

the degenerate two-photon-excited ﬂuorescence (2PEF) measure-

ment in the near-IR regime (700e850 nm) using Fluorescein

(w80

m

M in pH¼11 NaOH solution) as the standard.¹¹Fig. 4 shows

simultaneously extending the size of

the number of electron-donating branches attached to the

original D- -A framework of compound 1 could be an effective

p-domain by increasing

the measured degenerate two-photon absorption spectra of these

model compounds in THF (at the concentration of 1ꢀ10^ꢁ4M) and

the combined photophysical data are summarized in Table 1. It is

notable that all these model chromophores exhibit detectable 2PA

within the investigated spectral range and possess an overall as-

cending capability of 2PA from compound 1 to compound 4.

p

approach toward strong molecular 2PA. Besides, it can be seen

from Fig. 4 that chromophores 2e4 exhibit nearly identical

dispersion manner of 2PA with a common local maximum

positioned around 830 nm and this feature reveals that con-

tinuous expansion of the p-conjugation of this molecular sys-

tem under the aforementioned construction concept seems to

provide a beneﬁcial access to enhance the molecular 2PA

without shifting the major 2PA band, which could be very

useful for some particular applications when large multi-

photon absorptivities in a speciﬁc spectral region is required.

(2) Based on the fact that the measured ﬂuorescence emission

spectra (shown in Figs. 1 and 2) for each sample solution are

2.3. Discussion of results

From the measured photophysical properties of the studied

model compounds in the present work, some features are notable:

(1) Using compound 1 as a reference point, the observed ascend-

ing 2PA from compound 1 to compound 4 suggests that

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4939

4.4

4.2

4

3

2

1

0

(a)

1

2

3

4

(f)

(b)

λ

~790 nm

exc

4.0

1

3.8

3.6

3.4

3.2

3.0

2.8

2

3

4

3

2

1

0

Slope = 2.10

τ

~2.2 ns

-0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0

4.2

4.0

3.8

3.6

3.4

3.2

3.0

(c)

~3.3 ns

Slope = 2.06

-0.5 -0.4 -0.3 -0.2 -0.1

0.0

4.8

4.6

4.4

4.2

4.0

3.8

3.6

3.4

(d)

τ

~3.3 ns

Slope = 2.00

-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1

4.8

4.6

4.4

4.2

4.0

3.8

3.6

3.4

3.2

3.0

2.8

(e)

τ

~2.2 ns

Slope = 1.99

-0.8

-0.6

-0.4

-0.2

0.0

400 450 500 550 600 650 700 750 800

-2 -1 0

1 2 3 4 5 6 7 8 9

Log(Input Intensity)/a.u.

Wavelength (nm)

Time (ns)

Fig. 3. (a) Normalized two-photon-excited emission spectra of ﬂuorophores 1e4 in THF at 1ꢀ10^ꢁ4M; (b), (c), (d) and (e) are the logarithmic plots of power-squared dependence of

the 2PA-induced ﬂuorescence intensity on the input intensity of these compounds in THF; (f) Normalized two-photon-excited ﬂuorescence decay curves of these chromophores in

THF.

Table 1

Photophysical properties of the studied model chromophores 1e4^a

3000

l^a_m^b_a^s_x=nm^blogε_maxl_m^em_ax=nm^cF_F

s

_2PAꢁFL=ns^ed^m₂^ax=GM^fN_p^effd^m₂^ax=N_p^eff

d

g

1

2

3

4

1

2

3

4

386

396

397

398

4.71

5.00

5.34

5.58

454

518

519

520

0.59 2.2

0.40 3.3

0.43 3.3

0.43 2.2

w185

w675

w1350

w2990

23.6 7.8

30.3 22.3

40.4 33.4

55.5 53.9

2500

2000

1500

1000

500

Concentration was 1ꢀ10^ꢁ5M and 1ꢀ10^ꢁ4M for 1PA-related and 2PA-related

a

measurements, respectively.

b

One-photon absorption maximum.

1PA-induced ﬂuorescence emission maximum.

c

d

Fluorescence quantum efﬁciency.

e

2PA-indueced ﬂuorescence lifetime.

f

Maximum 2PA cross-section value (with experimental error wꢂ15%);

1 GM¼1ꢀ10^ꢁ50cm⁴s/photon-molecule.

g

Effective p-electron number.

0

700 720 740

760 780 800 820

840

nearly the same for one- and two-photon excitations, one can

conclude that in these cases, the ﬂuorescence emission is

predominantly from the same relaxed excited-state of each

model chromophore.¹²On the other hand, the observed

medium-level quantum yields from these compounds also in-

dicates that these chromophores could be utilized as frequency

upconverters for the biophotonic applications, such as two-

photon-excited ﬂuorescence microscopy.

Wavelength (nm)

Fig. 4. Measured degenerate two-photon absorption spectra of model chromophores

1e4 by 2PEF method in THF solution at 1ꢀ10^ꢁ4M (with experimental error wꢂ15%).

3. Effective optical power-limiting behaviors in nanosecond

regime

(3) It is notable that the excited-state lifetimes of the studied

model chromophores in the present work are in the nano-

second range, which implies that signiﬁcant excited-state

population may be retained and consequently possessess

excited-state absorption during the excitation by longer laser

pulses. This feature is particularly desirable with regards to

optical power-limiting applications in the nanosecond re-

gime based on 2PA-induced excited-state absorption (2PA-

induced ESA) since the effective three-photon absorption

coefﬁcient increases signiﬁcantly with the excited-state

lifetime.^10f

It is well known that an ideal optical-limiter is expected to show

an intensity-dependent transmission feature so that the output

intensity always below a certain maximum value, which makes

optical-limiters applicable for automatic protection of human eyes

and sensors against intense laser radiation. Additionally, this

power-limiting phenomenon is also important for optical dynamic

range compression and noise suppression in signal processing as

well as nonlinear ultra-fast ﬁltering/reshaping of optical ﬁber sig-

nals. Compared to other mechanisms of optical power-limiting,

such as reverse saturable absorption and nonlinear scattering,¹³the

2PA mechanism provides several promising advantages includes:

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T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

(1) Negligible linear absorption loss for weak optical signals; (2)

quick temporal response to the intensity or power change of the

incident optical signal; and (3) retention of optical quality for the

input beam after passing through the nonlinear absorption

medium.

wide-dispersed two-photon absorptivities in the near IR-region.

Tentative analysis of the correlation between molecular structure

and the observed overall 2PA reveals that repeatedly increase the

number of electron-donating branches while extending the size of

p-domain based on a D-p-A skeleton will enhance the molecular

Recently, many researchers have realized that the intensity-

dependent 2PA-induced excited-state absorption plays an essen-

tial role for the observed large 2PA in various organic systems under

the irradiation of nanosecond laser pulses,¹⁰and the term ‘effective

2PA’ is consequently used to describe the apparent 2PA parameter

measured in nanosecond time domain.^9b,10bFrom the viewpoint of

application, any medium that exhibits strong apparent nonlinear

absorption covering wide spectral range could be very useful op-

tical power-attenuators against the laser pulses working in nano-

second time domain.^3c,14

2PA without shifting the major 2PA band in this dye system.

Moreover, effective optical power-limiting behaviors of the den-

dritic ﬂuorophores were also demonstrated to show that such dye

molecules can be potential materials as broadband and quick-

responsive optical-limiters especially against those laser lights

with longer pulses.

5. Experimental

5.1. General

In order to study the effective power-limiting performance of

these model chromophores, we have utilized nanosecond laser

pulses for this investigation. In our experiment, the nonlinear ab-

sorbing medium was a 1-cm path-length solution of each studied

dye in THF with concentration of 0.02 M. A tunable nanosecond

laser system (an integrated Q-switched Nd:YAG laser and OPO: NT

342/3 from Ekspla) was employed as an excitation laser light source

to provide w6 ns laser pulses with controlled average pulse energy

in the range of w0.02e2 mJ and repetition rate of 10 Hz for this

study. The laser beam was slightly focused onto the center of the

sample solution in order to obtain a nearly uniform laser beam

radius within the whole cell path-length and the transmitted laser

beam from the sample cell was detected by an optical power (en-

ergy) meter with a large detection area of w25 mm in diameter.

Fig. 5 illustrates the measured power-attenuation performance at

w800 nm based on these chromophore solutions. One can see that

compound 4 displays the superior power restriction property at

800 nm compared to the other congeners. This initial ﬁnding sug-

gests the potentiality of using this model ﬂuorophore for broad-

band power-suppressing-related applications in the nanosecond

regime.

All commercially available reagents for the preparation of the

intermediates and targeted chromophores were purchased from

Aldrich Chemical Co. and were used as received, unless stated

otherwise. ¹H NMR and ¹³C NMR spectra were recorded either at

200 or 300 MHz spectrometers and referenced to TMS or residual

CHCl₃. High-resolution mass spectroscopy (HRMS) was conducted

by using a Waters LCT ESI-TOF mass spectrometer. MALDI-TOF MS

spectra were obtained on a Voyager DE-PRO mass spectrometer

(Applied Biosystem, Houston, USA). IR spectra were measured by

a Fourier transform infrared spectrometer (Jasco, FT/IR 4100).

5.2. Photophysical methods

All the linear optical properties of the subject model compound

were measured by corresponding spectrometers and the detailed

experimental conditions as well as the optical set-ups for nonlinear

optical property investigations are described in the Supplementary

data.

5.3. Synthesis

In Schemes 1 and 2, compound 5 (2,7-dibromo-9,9-dihexyl-9H-

ﬂuorene) is the major starting material for the synthesis of the

backbones of each intermediates and model chromophores. This

compound was obtained in a total yield of w80% by applying

bromination and then alkylation on a ﬂuorene unit.¹⁵For the syn-

thesis of other key intermediates (compounds 6e22) and the tar-

geted model compounds (1e4), a series of functionalization steps

starting from compound 5 have been conducted and are presented

as the following:

2.0

1

2

1.5

3

4

1.0

5.3.1. 7-Bromo-9,9-dihexyl-N,N-diphenyl-9H-ﬂuoren-2-amine

(6). To a mixture of compound 5 (30 g; 0.06 mol) and diphenylamine

(11.34 g; 0.067 mol) in toluene (120 mL) was added of BINAP (1.14 g;

1.8 mmol), Pd₂(dba)₃(0.56 g; 0.6 mmol), sodium tert-butoxide (8.2 g;

0.084 mol) and stirred at 80 ^ꢃC under Ar atmosphere for 24 h. After

cooling to the room temperature, w100 mL of H₂O was added to the

reaction mixture. The above solution was then extracted with ethyl

acetate and then dried over MgSO_4(S). After removing the solvent, the

crudeproductwaspuriﬁedthroughcolumnchromatographyonsilica

gel using hexane as the eluent to give the ﬁnal puriﬁed product as

pale-yellow oil with yield of w55% (19.44 g). IR (KBr, cm^ꢁ1): 3063,

3033 (C(sp²)eH stretching absorptions), 2954, 2925, 2853 (C(sp³)eH

stretching absorptions), 1608, 1482 (stretching absorptions of ben-

zene rings), 1466 (CH₂bending absorption), 1375 (CH₃bending ab-

sorption), 1300 (AreN stretching absorption). ¹H NMR (200 MHz,

0.5

0.0

0.5

1.0

1.5

2.0

Input energy (mJ)

Fig. 5. Measured optical power-attenuation curves at w800 nm based on the studied

chromophore solutions at 0.02 M.

4. Conclusion

We have synthesized a novel multi-polar chromophore set

composed of four members of analogues with unsymmetric

substituted skeletons using functionalized ﬂuorene and oxadiazole

moieties as the major building units. The initial experimental re-

sults indicate that these model ﬂuorophores manifest strong and

CDCl₃, tentative assignment based on calculated values) d: 7.54e7.50

(d, J¼8.1 Hz,1H, ArH on the ﬂuorene unit), 7.50e7.44 (d, J¼8.1 Hz,1H,

ArH on the ﬂuorene unit), 7.45e7.40 (dd, J₁¼8.1 Hz, J₂¼3 Hz, 2H, ArH

on the ﬂuorene unit), 7.30e7.22 (m, 4H, ArH on the diphenylamino

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4941

group), 7.14e7.11 (dd, J₁¼8.1 Hz, J₂¼3 Hz, 2H, ArH on the diphenyla-

mino group), 7.10e7.07 (m, 4H, ArH on the diphenylamino group),

7.05e6.98 (m, 2H, ArH on the ﬂuorene unit), 1.87e1.79 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.17e0.99 (m, 12H, eCH₂CH₂CH₂CH₂

CH₂CH₃), 0.81 (t, J¼7.04 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.64 (m,

4H, eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative

chain), 13.91 (carbon on the alkyl chain); HRMS-FAB(m/z): M^þcalcd

for C₃₈H₄₂N₂, 526.3348, found, 526.3342.

5.3.3. 9,9-Dihexyl-N,N-diphenyl-7-(1H-tetrazol-5-yl)-9H-ﬂuoren-2-

amine (8). To a mixture of compound 7 (6 g; 11.4 mmol), and NaN₃

(0.88 g; 13.7 mmol) in toluene (20 mL) was added (n-Bu)₃SnCl

(3.7 mL; 13.7 mmol), then stirred and reﬂuxed in Ar for 24 h. After

cooling to the room temperature, the above solution was then

assignmentbased on calculated values) d: 152.79 (aromaticcarbon on

the ﬂuorene unit), 151.67 (aromatic carbon on the ﬂuorene unit),

147.82 (aromatic carbon on the diphenylamino group), 147.49 (aro-

matic carbon on the ﬂuorene unit), 139.88 (aromatic carbon on the

ﬂuorene unit), 135.00 (aromatic carbon on the ﬂuorene unit), 129.87

(aromatic carbon on the diphenylamino group), 129.13 (aromatic

carbon on the ﬂuorene unit),125.89 (aromatic carbon on the ﬂuorene

unit),123.41 (aromatic carbon on the ﬂuorene unit),122.85 (aromatic

carbon on the ﬂuorene unit),120.41 (aromatic carbon on the ﬂuorene

unit), 122.58 (aromatic carbon on the diphenylamino group), 120.43

(aromatic carbon on the ﬂuorene unit), 120.36 (aromatic carbon on

the diphenylamino group), 120.14 (aromatic carbon on the ﬂuorene

unit),119.01(aromaticcarbononthe ﬂuoreneunit), 55.26 (sp³-carbon

on the ﬂuorene unit), 40.10 (carbon on the alkyl chain), 31.44 (carbon

onthe alkyl chain), 29.51 (carbononthe alkyl chain), 23.66(carbon on

the alkyl chain), 22.50 (carbon on the alkyl chain), 14.03 (carbon on

the alkyl chain); HRMS-FAB(m/z): [MþH]^þcalcd for C₃₇H₄₂BrN,

579.2501, found [(⁷⁹Br)MþH]^þ¼579.2507; [(⁸¹Br)MþH]^þ¼281.2483.

extracted with CH₂Cl₂and the organic layer was dried overMgSO_4(S)

.

After removing the solvent, the crude product was puriﬁed through

column chromatography on silica gel using ethyl acetate/hexane

(1:1) as the eluent to give the yellow puriﬁed product with yield of

80.2% (5.2 g). IR (KBr, cm^ꢁ1): 3061, 3036 (C(sp²)eH stretching ab-

sorptions), 2926, 2856 (C(sp³)eH stretching absorptions),1610,1488

(stretching absorptions of benzene rings), 1585 (N]N stretching

absorption) 1469 (CH₂bending absorption), 1376 (CH₃bending ab-

sorption), 1340 (AreN stretching absorption). ¹H NMR (300 MHz,

CDCl₃, tentative assignment based on calculated values) d: 8.27 (s,

1H, ArH on the ﬂuorene unit), 8.25e8.22 (dd, J₁¼8.1 Hz, J₂¼1.2 Hz,

1H, ArH on the ﬂuorene unit), 7.77e7.74 (d, J¼8.1 Hz, 1H, ArH on the

ﬂuorene unit), 7.59, 7.56 (d, J¼8.1 Hz, 1H, ArH on the ﬂuorene unit),

7.27e7.22 (t, J¼7.2 Hz, 4H, ArH on the diphenylamino group),

7.12e7.10 (m, 6H, ArH on the diphenylamino group), 7.04e6.99 (m,

2H, ArH on the ﬂuorene unit), 2.12e1.70 (m, 4H, eCH₂CH₂CH₂CH₂

CH₂CH₃), 1.09e0.98 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.73e0.69

5.3.2. 7-(Diphenylamino)-9,9-dihexyl-9H-ﬂuorene-2-carbonitrile

(7). Toa mixture of compound 6 (8 g;13.8mmol) in dryDMF(50 mL)

was added CuCN (2.48 g; 27.4 mmol), then stirred and under reﬂux

for 12 h. After cooling to the room temperature, the reaction was

poured into NH₄OH_(aq)(w100 mL) and stirred for 1 h. The above

solution was then extracted with ethyl acetate and the organic layer

was dried over MgSO_4(S). After removing the solvent, the crude

product was puriﬁed through column chromatography on silica gel

using ether/hexane (1:20) as the eluent to give the ﬁnal puriﬁed

product as orange powder with yield of 87.5% (6.81 g). Mp:

79.9e82.1. IR (KBr, cm^ꢁ1): 3071, 3034 (C(sp²)eH stretching absorp-

tions), 2958, 2927, 2854 (C(sp³)eH stretching absorptions), 2220

(C^N stretching absorption), 1592, 1472 (stretching absorptions of

benzene rings), 1463 (CH₂bending absorption), 1376 (CH₃bending

absorption), 1312 (AreN stretching absorption). ¹H NMR (300 MHz,

(t,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

signment based on calculated values) : 156.89 (carbon on tetrazole

6H,

eCH₂CH₂CH₂CH₂CH₂CH₃),

0.64e0.62

(m,

4H,

d

unit), 152.91 (aromatic carbon on the ﬂuorene unit), 152.03 (aro-

matic carbon on the ﬂuorene unit), 148.39 (aromatic carbon on the

ﬂuorene unit), 147.75 (aromatic carbon on the diphenylamino

group), 144.82 (aromatic carbon on the ﬂuorene unit), 134.49 (aro-

matic carbon on the ﬂuorene unit), 129.22 (aromatic carbon on the

diphenylamino group), 126.73 (aromatic carbon on the ﬂuorene

unit), 124.16 (aromatic carbon on the diphenylamino group), 123.13

(aromatic carbon on the ﬂuorene unit), 122.89 (aromatic carbon on

the diphenylamino group), 121.95 (aromatic carbon on the ﬂuorene

unit), 121.20 (aromatic carbon on the ﬂuorene unit), 120.53 (aro-

matic carbon on the ﬂuorene unit), 119.88 (aromatic carbon on the

ﬂuorene unit), 118.62 (aromatic carbon on the ﬂuorene unit), 55.54

(sp³-carbon on the ﬂuorene unit), 40.06 (carbon on the alkyl chain),

31.45 (carbon on the alkyl chain), 29.50 (carbon on the alkyl chain),

23.78 (carbon on the alkyl chain), 22.46 (carbon on the alkyl chain),

13.96 (carbon on the alkyl chain); HRMS-FAB(m/z): M^þcalcd for

C₃₈H₄₃N₅, 569.3518, found, 569.3525.

CDCl₃, tentative assignment based on calculated values) d: 7.64e7.61

(m, 2H, ArH on the ﬂuorene unit), 7.59e7.57 (m, 1H, ArH on the

ﬂuorene unit), 7.56e7.53 (d, J¼7.5 Hz, 1H, ArH on the ﬂuorene unit),

7.29e7.24 (t, J¼7.2 Hz, 4H, ArH on the diphenylamino group), 7.14 (s,

1H), 7.11e7.09 (m, 2H, ArH on the diphenylamino group), 7.07e7.05

(dd, J₁¼7.2 Hz, J₂¼1.2 Hz,1H, ArH on the ﬂuorene unit), 7.07e7.05 (m,

4H, ArH on the diphenylamino group), 1.91e1.79 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.15e1.05 (m, 12H, eCH₂CH₂CH₂CH₂

CH₂CH₃), 0.82e0.77 (t, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.64e0.59(d,

4H, eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative

5.3.4. 9,9-Dihexyl-N²,N²-diphenyl-9H-ﬂuorene-2,7-diamine

(9). Two-step reaction: (i) To a solution of compound 6 (15 g;

0.258 mol) in DMAc (135 mL) was added potassium phthalimide

(4.77 g; 0.258 mol), and CuI (4.92 g; 0.258 mol). The resulting so-

lution was stirred and reﬂuxed for 24 h. After cooling to the room

temperature, the reaction mixture was then extracted with ether

and then dried over MgSO_4(S). After removing the solvent, the crude

product was obtained as dark brown solid. (ii) To a solution of the

crude product from ﬁrst step in ethanol (150 mL) was added of

NH₂NH₂$H₂O (1.293 g; 0.258 mol). The resulting solutionwas stirred

and reﬂuxed for 6 h. After cooling to the room temperature, the re-

action mixture was then extracted with ethyl acetate (30mLꢀ3), and

the organic layer was dried over MgSO_4(S). After removing the sol-

vent, the crude product was puriﬁed by column chromatography on

silica gel using ether/hexane (1:10) as the eluent to give the ﬁnal

puriﬁed product as brown powder with yield of w62% (8.31 g). Mp:

117.1e119.2. IR (KBr, cm^ꢁ1): 3458, 3426 (NeH stretching absorp-

tions), 3214 (C(sp²)eH stretching absorption), 2954, 2926, 2854

(C(sp³)eH stretching absorptions), 1630 (NH₂bending absorption),

1610, 1468 (stretching absorptions of benzene rings), 1456 (CH₂

assignment based on calculated values) d: 152.75 (aromatic carbon

on the ﬂuorene unit), 151.06 (aromatic carbon on the ﬂuorene unit),

148.85 (aromatic carbon on the ﬂuorene unit), 147.47 (aromatic

carbon on the diphenylamino group), 145.46 (aromatic carbon on

the ﬂuorene unit), 133.44 (aromatic carbon on the ﬂuorene unit),

131.27 (aromatic carbon on the ﬂuorene unit), 129.20 (aromatic

carbon on the diphenylamino group), 126.03 (aromatic carbon on

the ﬂuorene unit), 124.31 (aromatic carbon on the ﬂuorene unit),

123.09 (aromatic carbon on the diphenylamino group), 122.68 (ar-

omatic carbon on the diphenylamino group), 121.44 (aromatic car-

bon on the ﬂuorene unit), 119.89 (aromatic carbon on the ﬂuorene

unit), 119.26 (aromatic carbon on the ﬂuorene unit), 117.90 (carbon

on the cyano group), 108.62 (aromatic carbon on the ﬂuorene unit),

55.24 (sp³-carbon on the ﬂuorene unit), 39.82 (carbon on the alkyl

chain), 31.33 (carbon on the alkyl chain), 29.36 (carbon on the alkyl

chain), 23.59 (carbon on the alkyl chain), 22.39 (carbon on the alkyl

4942

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

bending absorption), 1375 (CH₃bending absorption), 1098 (AreN

121.66 (aromatic carbon on the ﬂuorene unit), 120.98 (aromatic

carbon on the diphenylamino group), 120.43 (aromatic carbon on

the ﬂuorene unit), 120.05 (aromatic carbon on the diphenylamino

group), 118.14 (aromatic carbon on the ﬂuorene unit), 112.01 (aro-

matic carbon on the ﬂuorene unit), 54.93 (sp³-carbon on the ﬂuo-

rene unit), 40.47 (carbon on the alkyl chain), 31.60 (carbon on the

alkyl chain), 29.74 (carbon on the alkyl chain), 23.84 (carbon on the

alkyl chain), 22.60 (carbon on the alkyl chain), 14.05 (carbon on the

alkyl chain); HRMS (m/z): M^þcalcd for C₇₄H₈₅N₃1015.6743, found,

1015.6738.

stretching absorption). ¹H NMR (300 MHz, CDCl₃, tentative assign-

ment based on calculated values)

d: 7.43e7.40 (t, J¼8.4 Hz, 2H, ArH

on the ﬂuorene unit), 7.23e7.18 (t, J¼8.4 Hz, 4H, ArH on the diphe-

nylamino group), 7.11e7.09 (m, 4H, ArH on the diphenylamino

group), 7.08e7.07 (s,1H, ArH on the ﬂuorene unit), 7.00e6.97 (m,1H,

ArH on the diphenylamino group), 6.96e6.92 (m, 2H, ArH on the

ﬂuorene unit), 6.61e6.59 (m, 2H, ArH on the ﬂuorene unit),

3.689e3.66 (s, 2H, NH₂on the amino group), 1.87e1.79 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.17e0.99 (m, 12H, eCH₂CH₂CH₂CH₂CH₂

CH₃), 0.81 (t, J¼8.4 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.64 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

5.3.6. 7-Bromo-9,9-(dihexyl-9H-ﬂuoren-2-yl)trimethylsilane

(11). n-Butyllithium in hexane (26.9 mL, 1.6 M, 0.043 mol) was

added to a solution of 5 (20 g, 0.041 mol) in dry ether (150 mL) at

ꢁ78 ^ꢃC under N₂atmosphere, and stirred for 1 h. Then chloro-

trimethylsilane (6 mL, 0.0462 mol) was added slowly at ꢁ78 ^ꢃC and

the reaction was allowed to slowly warm to room temperature and

stirred overnight. The reaction mixture was quenched with satu-

rated brine and the resulting solution was extracted by diethyl

ether. The organic layer was washed with brine and H₂O for three

times and dried over MgSO_4(S). After removing the solvent, the

crude product was puriﬁed through chromatography on silica with

hexane as eluent to give ﬁnal puriﬁed product as a colorless oil

(19.16 g, 97%). IR (KBr, cm^ꢁ1): 3201 (C(sp²)eH stretching absorp-

tion), 2954, 2925, 2853 (C(sp³)eH stretching absorptions), 1609,

1482 (stretching absorptions of benzene rings), 1455 (CH₂bending

absorption), 1376 (CH₃bending absorption), 1305 (AreN stretching

absorption), 1246 (SieC stretching absorption). ¹H NMR (300 MHz,

signment based on calculated values) d: 152.51 (aromatic carbon on

the ﬂuorene unit), 151.09 (aromatic carbon on the ﬂuorene unit),

148.08 (aromatic carbon on the diphenylamino group), 145.38 (ar-

omatic carbon on the ﬂuorene unit), 137.25 (aromatic carbon on the

ﬂuorene unit),132.15 (aromatic carbon on the ﬂuorene unit),128.96

(aromatic carbon on the diphenylamino group), 124.03 (aromatic

carbon on the ﬂuorene unit), 123.22 (aromatic carbon on the

diphenylamino group), 121.93 (aromatic carbon on the diphenyla-

mino group), 119.97 (aromatic carbon on the ﬂuorene unit), 119.89

(aromatic carbon on the ﬂuorene unit), 118.89 (aromatic carbon on

the ﬂuorene unit), 113.87 (aromatic carbon on the ﬂuorene unit),

109.68 (aromatic carbon on the ﬂuorene unit), 54.72 (sp³-carbon on

the ﬂuorene unit), 40.42 (carbon on the alkyl chain), 31.46 (carbon

on the alkyl chain), 29.60 (carbon on the alkyl chain), 23.65 (carbon

on the alkyl chain), 22.49 (carbon on the alkyl chain), 13.97 (carbon

on the alkyl chain); HRMS-FAB(m/z): M^þcalcd for C₃₇H₄₄N₂,

516.3504, found, 516.3505.

CDCl₃, tentative assignment based on calculated values)

d:

7.85e7.84 (d, J¼7.8 Hz, 1H, ArH on the ﬂuorene unit), 7.77e7.73 (m,

2H, ArH on the ﬂuorene unit), 7.63e7.61 (m, 2H, ArH on the ﬂuo-

rene unit), 7.54e7.52 (d, J¼7.8 Hz, 1H, ArH on the ﬂuorene unit),

2.13e2.12 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃), 1.20e1.19 (m, 12H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.91 (t, J¼7.8 Hz, 6H, eCH₂CH₂CH₂CH₂

CH₂CH₃), 0.64 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.46 (s, 9H, CH₃on

the TMS unit); ¹³C NMR (75 MHz, CDCl₃, tentative assignment

5.3.5. N²-(7-(Diphenylamino)-9,9-dihexyl-9H-ﬂuoren-2-yl)-9,9-

dihexyl-N⁷,N⁷-diphenyl-9H-ﬂuorene-2,7-diamine (10). To a mixture

of compound 9 (8.3 g; 0.161 mol), and 6 (9.3 g; 0.161 mol) in dry

toluene (15 mL) was added Pd₂(dba)₃(0.073 g; 0.0803 mmol), so-

dium tert-butoxide (1.852 g; 0.193 mol), P(t-Bu)₃(0.0322 g;

0.161 mmol) and stirred at 90 ^ꢃC under Ar atmosphere for 12 h.

After cooling to the room temperature, w100 mL of H₂O was added

to the reaction mixture. The above solution was then extracted with

ethyl acetate (30mLꢀ3) and the organic layer was dried over

MgSO_4(S). After removing the solvent, the crude product was pu-

riﬁed through column chromatography on silica gel using ether/

hexane (1:20) as the eluent to give the ﬁnal puriﬁed product as gray

power with yield of w60.2% (4.91 g). Mp: 129.9e132.3. IR (KBr,

cm^ꢁ1): 3392 (NeH stretching absorption), 3061, 3033 (C(sp²)eH

stretching absorptions), 2953, 2925, 2854 (C(sp³)eH stretching

absorptions), 1597, 1473 (stretching absorptions of benzene rings),

1464 (CH₂bending absorption), 1378 (CH₃bending absorption). ¹H

NMR (300 MHz, CDCl₃, tentative assignment based on calculated

based on calculated values) d: 153.07 (aromatic carbon on the ﬂu-

orene unit), 149.17 (aromatic carbon on the ﬂuorene unit), 140.68

(aromatic carbon on the ﬂuorene unit), 139.96 (aromatic carbon on

the ﬂuorene unit), 139.71 (aromatic carbon on the ﬂuorene unit),

132.09 (aromatic carbon on the ﬂuorene unit), 129.89 (aromatic

carbon on the ﬂuorene unit), 127.41 (aromatic carbon on the ﬂuo-

rene unit), 126.19 (aromatic carbon on the ﬂuorene unit), 121.44

(aromatic carbon on the ﬂuorene unit), 121.07 (aromatic carbon on

the ﬂuorene unit), 119.06 (aromatic carbon on the ﬂuorene unit),

55.20 (sp³-carbon on the ﬂuorene unit), 40.03 (carbon on the alkyl

chain), 31.30 (carbon on the alkyl chain), 29.50 (carbon on the alkyl

chain), 23.57 (carbon on the alkyl chain), 22.45 (carbon on the alkyl

chain), 14.00 (carbon on the alkyl chain), ꢁ0.89 (carbon on the TMS

unit); HRMS-FAB(m/z): [MþH]^þcalcd for C₂₈H₄₁BrSi, 484.2161,

found [(⁷⁹Br)MþH]^þ¼484.2150; [(⁸¹Br)MþH]^þ¼486.2150.

values) d: 7.52e7.48 (m, 4H, ArH on the ﬂuorene unit), 7.36e7.32

(m, 4H, ArH on the ﬂuorene unit), 7.30e7.22 (m, 4H, ArH on the

diphenylamino group), 7.26e7.20 (t, J¼8.1 Hz, 8H, ArH on the

diphenylamino group), 7.12e7.10 (t, J¼8.1 Hz, 12H, ArH on the

diphenylamino group), 7.02e6.95 (m, 4H, ArH on the ﬂuorene unit),

6.42 (s, 1H, NH on the amino group), 1.84e1.79 (m, 8H,

5.3.7. 9,9-Dihexyl-7-(trimethylsilyl)-9H-ﬂuoren-2-amine (12). Two-

step reaction: (i) To a solution of compound 11 (19 g; 0.039 mol) in

DMAc (45 mL) was added of potassium phthalimide (7.26 g;

0.039 mol), and CuI (7.44 g; 0.039 mol) was stirred and heated to

reﬂux for 24 h. After cooling to the room temperature, the reaction

mixture was then extracted with ether, dried over MgSO_4(S). After

removing the solvent, the crude product was obtained as brown

solid. (ii) To a solution of the crude product from ﬁrst step in eth-

anol (300 mL) was added of NH₂NH₂,H₂O (2.46 g; 0.039 mol) and

the resulting solution was stirred and reﬂuxed for 6 h. After cooling

to room temperature, the reaction mixture was then extracted with

ethyl acetate (30mLꢀ3) and the collected organic layer was dried

over MgSO_4(S). After removing the solvent, the crude product was

puriﬁed by column chromatography on silica gel using ether/

eCH₂CH₂CH₂CH₂CH₂CH₃),

1.15e1.08

(m,

24H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.81 (t, J¼7.04 Hz, 6H, eCH₂CH₂CH₂CH₂

CH₂CH₃), 0.64 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz,

CDCl₃, tentative assignment based on calculated values) d: 152.62

(aromatic carbon on the ﬂuorene unit), 150.47 (aromatic carbon on

the ﬂuorene unit), 148.06 (aromatic carbon on the diphenylamino

group), 147.49 (aromatic carbon on the ﬂuorene unit), 132.46 (ar-

omatic carbon on the ﬂuorene unit), 131.23 (aromatic carbon on the

ﬂuorene unit), 129.03 (aromatic carbon on the diphenylamino

group), 127.06 (aromatic carbon on the ﬂuorene unit), 125.89 (ar-

omatic carbon on the ﬂuorene unit),123.83 (aromatic carbon on the

ﬂuorene unit), 122.85 (aromatic carbon on the ﬂuorene unit),

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4943

hexane (1:10) as the eluent to give the ﬁnal puriﬁed product as

white powder as pale-yellow oil with yield of 70.5% (11.62 g); IR

(KBr, cm^ꢁ1): 3468, 3398 (NeH stretching absorptions), 3206

(C(sp²)eH stretching absorption), 2953, 2925, 2856 (C(sp³)eH

stretching absorptions), 1624 (NH₂bending absorption), 1609, 1482

(stretching absorptions of benzene rings), 1455 (CH₂bending ab-

sorption), 1376 (CH₃bending absorption), 1305 (AreN stretching

absorption), 1246 (SieC stretching absorption). ¹H NMR (300 MHz,

carbon on the ﬂuorene unit), 54.88 (sp³-carbon on the ﬂuorene

unit), 40.45 (carbon on the alkyl chain), 31.46 (carbon on the alkyl

chain), 29.71 (carbon on the alkyl chain), 23.73 (carbon on the alkyl

chain), 22.55 (carbon on the alkyl chain), 14.01 (carbon on the alkyl

chain), ꢁ0.83 (1^ꢃcarbon on the TMS unit); HRMS (m/z): M^þcalcd

for C₅₆H₈₃NSi₂825.6064, found, 825.6063.

5.3.9. Bis(9,9-dihexyl-7-(trimethylsilyl)-9H-ﬂuoren-2-yl)carbamate

(14). To a mixture of compound 13 (4.9 g; 6 mmol) in dry THF

(45 mL) was added (Boc)₂O (2.59 g; 0.012 mol), 4-DMAP (0.362 g;

0.003 mmol) and stirred at 90 ^ꢃC under N₂atmosphere for 12 h.

After cooling to the room temperature, the reaction mixture was

then extracted with ethyl acetate and the organic layer was dried

over MgSO_4(S). After removing the solvent, the crude product was

puriﬁed through column chromatography on silica gel using ethyl

acetate/hexane (1:50) as the eluent to give the ﬁnal puriﬁed

product with yield of w81% (4.45 g). ¹H NMR (300 MHz, CDCl₃,

CDCl₃, tentative assignment based on calculated values)

d:

7.66e7.63 (d, J¼7.5 Hz, 1H, ArH on the ﬂuorene unit), 7.66e7.63 (d,

J¼7.5 Hz, 1H, ArH on the ﬂuorene unit), 7.58e7.52 (m, 2H, ArH on

the ﬂuorene unit), 7.38e7.36 (d, J¼7.5 Hz, 1H, ArH on the ﬂuorene

unit), 6.74e6.69 (m, 2H, ArH on the ﬂuorene unit), 3.72 (s, 2H, NH₂

on

the

amino

group),

2.12e2.02

(m,

4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.22e1.16 (m, 12H, eCH₂CH₂CH₂CH₂CH₂

CH₃), 0.89e0.85 (m, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.78 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.41 (s, 9H, CH₃on the TMS unit); ¹³C

NMR (75 MHz, CDCl₃, tentative assignment based on calculated

tentative assignment based on calculated values) d: 7.69e7.64 (t,

values)

d

: 152.44 (aromatic carbon on the ﬂuorene unit), 149.62

J¼7.2 Hz, 4H, ArH on the ﬂuorene unit), 7.54e7.52 (d, J¼8.1 Hz, 4H

ArH on the ﬂuorene unit), 7.29e7.28 (d, J¼8.1 Hz, 2H ArH on the

ﬂuorene unit), 7.24e7.21 (d, J¼7.8 Hz, 2H ArH on the ﬂuorene unit),

2.02e1.95 (m, 8H, eCH₂CH₂CH₂CH₂CH₂CH₃), 1.11e1.16 (m, 24H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.53 (s, 9H, CH₃on the Boc group),

0.85e0.76 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.68 (m, 8H,

(aromatic carbon on the ﬂuorene unit), 145.86 (aromatic carbon on

the ﬂuorene unit), 141.49 (aromatic carbon on the ﬂuorene unit),

132.27 (aromatic carbon on the ﬂuorene unit), 131.62 (aromatic

carbon on the ﬂuorene unit), 126.48 (aromatic carbon on the ﬂu-

orene unit), 125.21 (aromatic carbon on the ﬂuorene unit), 122.42

(aromatic carbon on the ﬂuorene unit), 120.32 (aromatic carbon on

the ﬂuorene unit), 118.20 (aromatic carbon on the ﬂuorene unit),

113.78 (aromatic carbon on the ﬂuorene unit), 109.59 (aromatic

carbon on the ﬂuorene unit), 54.65 (sp³-carbon on the ﬂuorene

unit), 40.61 (carbon on the alkyl chain), 31.47 (carbon on the alkyl

chain), 29.73 (carbon on the alkyl chain), 23.61 (carbon on the alkyl

chain), 22.55 (carbon on the alkyl chain), 13.94 (carbon on the alkyl

chain), ꢁ0.90 (1^ꢃcarbon on the TMS unit) HRMS-FAB (m/z): M^þ

calcd for C₂₈H₄₃NSi 421.3165, found, 421.7332.

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.36 (s, 18H, CH₃on the TMS group); ¹³

NMR (75 MHz, CDCl₃, tentative assignment based on calculated

values)

: 153.75 (sp²-carbon on the Boc group), 151.27 (aromatic

C

d

carbon on the ﬂuorene unit), 149.98(aromatic carbon on the ﬂuo-

rene unit), 142.64 (aromatic carbon on the ﬂuorene unit), 141.20

(aromatic carbon on the ﬂuorene unit), 138.65 (aromatic carbon on

the ﬂuorene unit), 138.33 (aromatic carbon on the ﬂuorene unit),

131.79 (aromatic carbon on the ﬂuorene unit), 127.35 (aromatic

carbon on the ﬂuorene unit), 125.16 (aromatic carbon on the ﬂuo-

rene unit), 121.75 (aromatic carbon on the ﬂuorene unit), 119.79

(aromatic carbon on the ﬂuorene unit), 118.82 (aromatic carbon on

the ﬂuorene unit), 80.86 (4^ꢃcarbon on the Boc group), 54.93 (sp³-

carbon on the ﬂuorene unit), 40.12 (carbon on the alkyl chain),

31.38 (carbon on the alkyl chain), 29.55 (carbon on the alkyl chain),

28.28 (1^ꢃcarbon on the Boc group), 23.62 (carbon on the alkyl

chain), 22.46 (carbon on the alkyl chain), 13.98 (carbon on the alkyl

chain), ꢁ0.91(1^ꢃcarbon on the TMS unit); HRMS (m/z): M^þcalcd

for C₅₆H₈₃NSi₂925.6588, found, 925.6487.

5.3.8. Bis(9,9-dihexyl-7-(trimethylsilyl)-9H-ﬂuoren-2-yl)amine

(13). To a mixture of compound 12 (9 g; 0.0213 mol), and 11

(10.36 g; 0.0213 mol) in dry toluene (60 mL) was added Pd₂(dba)₃

(0.0976 g; 0.1064 mmol), sodium tert-butoxide (2.48 g; 0.256 mol),

P(t-Bu)₃(0.044 g; 0.2132 mmol) and stirred at 90 ^ꢃC under Ar at-

mosphere for 12 h. After cooling to the room temperature,

w100 mL of H₂O was added to the reaction mixture. The above

solution was then extracted with ethyl acetate (30mLꢀ3) and the

organic layer was over MgSO_4(S). After removing the solvent, the

crude product was puriﬁed through column chromatography on

silica gel using ethyl acetate/hexane (1:40) as the eluent to give the

ﬁnal puriﬁed product with yield of 55.6% (4.9 g). ¹H NMR (300 MHz,

5.3.10. tert-Butyl-bis(9,9-dihexyl-7-iodo-9H-ﬂuoren-2-yl)carbamate

(15). To a solution of compound 14 (4.45 g; 0.048 mol) in CH₂Cl₂

(20 mL) was added iodine monochloride (1.64 g; 0.01 mol) at 0 ^ꢃC,

then warm to room temperature and stirred for 4 h. w50 mL of

saturated NaHSO₃solutions was added into the reaction mixture.

The above solution was then extracted with dichloromethane

(30mLꢀ3) and the organic layer was dried over MgSO_4(S). After

removing the solvent, the crude product was puriﬁed by column

chromatography on silica gel using ethyl acetate/hexane (1:40) to

give the ﬁnal puriﬁed product of w75% (3.72 g). ¹H NMR (300 MHz,

CDCl₃, tentative assignment based on calculated values)

d:

7.59e7.56 (m, 6H, ArH on the ﬂuorene unit), 7.47e7.43 (m, 6H, ArH

on the ﬂuorene unit), 2.02e2.01 (m, 8H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.14e1.12 (m, 24H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.79e0.75 (m, 12H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.65 (m, 8H, eCH₂CH₂CH₂CH₂CH₂CH₃),

0.30 (s, 18H, CH₃on the TMS unit); IR (KBr, cm^ꢁ1): 3392 (NeH

stretching absorptions), 3206 (C(sp²)eH stretching absorption),

2956, 2927, 2857 (C(sp³)eH stretching absorptions), 1597, 1473

(stretching absorptions of benzene rings), 1464 (CH₂bending ab-

sorption), 1363 (CH₃bending absorption). 1307 (AreN stretching

absorption), 1247 (SieC stretching absorption). ¹³C NMR (75 MHz,

CDCl₃, tentative assignment based on calculated values)

d:

7.68e7.62 (t, J¼7.5 Hz, 4H, ArH on the ﬂuorene unit), 7.52e7.51 (d,

J¼8.1 Hz 4H, ArH on the ﬂuorene unit), 7.29e7.28 (d, J¼8.1 Hz, 2H,

ArH on the ﬂuorene unit), 7.24e7.22 (d, J¼7.2 Hz, 2H, ArH on the

ﬂuorene unit), 1.81e1.78 (m, 8H, eCH₂CH₂CH₂CH₂CH₂CH₃), 1.51 (s,

9H, CH₃on the Boc group) 1.10e1.05 (m, 24H,

CDCl₃, tentative assignment based on calculated values) d: 152.44

(aromatic carbon on the ﬂuorene unit), 152.14 (aromatic carbon on

the ﬂuorene unit), 149.21 (aromatic carbon on the ﬂuorene unit),

141.93 (aromatic carbon on the ﬂuorene unit), 137.35 (aromatic

carbon on the ﬂuorene unit), 134.38 (aromatic carbon on the ﬂu-

orene unit), 131.82 (aromatic carbon on the ﬂuorene unit), 127.31

(aromatic carbon on the ﬂuorene unit), 120.70 (aromatic carbon on

the ﬂuorene unit), 118.05 (aromatic carbon on the ﬂuorene unit),

116.85 (aromatic carbon on the ﬂuorene unit), 111.64 (aromatic

eCH₂CH₂CH₂CH₂CH₂CH₃),

0.84e0.76

(m,

12H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.65 (m, 8H, eCH₂CH₂CH₂CH₂CH₂CH₃);

¹³C NMR (75 MHz, CDCl₃, tentative assignment based on calculated

values) d

: 152.75 (sp²-carbon on the Boc group), 151.11 (aromatic

carbon on the ﬂuorene unit), 150.87 (aromatic carbon on the ﬂu-

orene unit), 149.87 (aromatic carbon on the ﬂuorene unit), 141.54

(aromatic carbon on the ﬂuorene unit), 141.10 (aromatic carbon on

4944

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

the ﬂuorene unit), 138.95 (aromatic carbon on the ﬂuorene unit),

137.25 (aromatic carbon on the ﬂuorene unit), 130.24 (aromatic

carbon on the ﬂuorene unit), 128.91 (aromatic carbon on the ﬂu-

orene unit)124.56 (aromatic carbon on the ﬂuorene unit), 120.25

(aromatic carbon on the ﬂuorene unit), 118.59 (aromatic carbon on

the ﬂuorene unit), 118.26 (aromatic carbon on the ﬂuorene unit),

92.18 (aromatic carbon on the ﬂuorene unit), 80.88 (4^ꢃcarbon on

the Boc group), 54.89 (sp³-carbon on the ﬂuorene unit), 39.84

(carbon on the alkyl chain), 31.26 (carbon on the alkyl chain), 29.48

(carbon on the alkyl chain), 28.18 (1^ꢃcarbon on the Boc group),

22.89 (carbon on the alkyl chain), 21.83 (carbon on the alkyl chain),

12.85 (carbon on the alkyl chain); HRMS (m/z): M^þcalcd for

C₅₅H₇₃I₂NO₂1033.3731, found, 1033.8998.

ﬂuorene unit), 120.14 (aromatic carbon on the ﬂuorene unit), 119.01

(aromatic carbon on the ﬂuorene unit), 117.20 (aromatic carbon on

the ﬂuorene unit), 55.26 (sp³-carbon on the ﬂuorene unit), 40.10

(carbon on the alkyl chain), 31.44 (carbon on the alkyl chain), 29.51

(carbon on the alkyl chain), 23.66 (carbon on the alkyl chain), 22.50

(carbon on the alkyl chain),14.03 (carbon on the alkyl chain); HRMS

(m/z): M^þcalcd for C₁₉₈H₂₃₃N₇2711.0155, found, 2712.0996.

5.3.12. 7-Bromo-9,9-dihexyl-9H-ﬂuorene-2-carbonitrile

(17). To

a mixture of compound 5 (8 g; 0.016 mol) in dry DMF (50 mL) was

added CuCN (1.3 g; 14.6 mmol), and stirred at 110 ^ꢃC for 24 h. After

cooling to the room temperature, w50 mL of NaOH_(aq)was added to

the reaction mixture. The above solution was then extracted with

ethyl acetate and the organic layer was dried over MgSO_4(S). After

removing the solvent, the crude product was puriﬁed through col-

umn chromatography on silica gel using ethyl acetate/hexane (1:20)

as the eluent to give the ﬁnal puriﬁed product as orange powder

with yield of w45% (3.21 g). Mp: 74.3e76.7. IR (KBr, cm^ꢁ1): 3068,

3051 (C(sp²)eH stretching absorptions), 2947, 2922, 2853 (C(sp³)eH

stretching absorptions), 2224 (C^N stretching absorption), 1608,

1454 (stretching absorptions of benzene rings), 1463 (CH₂bending

absorption), 1376 (CH₃bending absorption). ¹H NMR (300 MHz,

5.3.11. N²-(7-(7-(Bis(7-(diphenylamino)-9,9-dihexyl-9H-ﬂuoren-2-

yl)amino)-9,9-dihexyl-9H-ﬂuoren-2-ylamino)-9,9-dihexyl-9H-ﬂuo-

ren-2-yl)-N²-(7-(diphenylamino)-9,9-dihexyl-9H-ﬂuoren-2-yl)-9,9-

dihexyl-N⁷,N⁷-diphenyl-9H-ﬂuorene-2,7-diamine (16). Two-step re-

action: (i) To a mixture of compound 15 (2.4 g; 2.321 mol), and 10

(4.718 g; 4.642 mol) in dry toluene (15 mL) was added Pd₂(dba)₃

(0.085 g; 0.093 mmol), sodium tert-butoxide (0.468 g; 4.874 mmol),

P(t-Bu)₃(0.038 g; 0.186 mmol) and stirred at 90 ^ꢃC under Ar at-

mosphere for 12 h. After cooling to the room temperature,

w100 mL of H₂O was added to the reaction mixture. The above

solution was then extracted with ethyl acetate (30mLꢀ3) and the

organic layer was dried over MgSO_4(S). After removing the solvent,

the crude product was puriﬁed through column chromatography

on silica gel using ethyl acetate/hexane (1:20) as the eluent to give

the ﬁnal puriﬁed product with yield of w78% (5.08 g). HRMS (m/z):

M^þcalcd for C₂₀₃H₂₄₁N₇O 2811.1313, found, 2812.8954. (ii) To

a solution of compound from the ﬁrst step in CH₂Cl₂(30 mL) was

added TFA (1.44 g; 0.013 mol), and stirred at room temperature

under for 2 h. Then, w50 mL of NaOH_(aq)was added into the re-

action mixture, and the above solution was then extracted with

dichloromethane (30mLꢀ3) and then dried over MgSO_4(S). After

removing the solvent, the crude product was puriﬁed by column

chromatography on silica gel using ethyl acetate/hexane (1:20) to

give the ﬁnal puriﬁed product as gray powder with yield of 84.6%

(4.17 g). IR (KBr, cm^ꢁ1): 3395 (NeH stretching absorption), 3062,

3033 (C(sp²)eH stretching absorptions), 2953, 2926, 2855 (C(sp³)e

H stretching absorptions), 1586, 1493 (stretching absorptions of

benzene rings), 1465 (CH₂bending absorption), 1377 (CH₃bending

absorption). ¹H NMR (300 MHz, CDCl₃, tentative assignment based

CDCl₃, tentative assignment based on calculated values) d: 7.75e7.72

(dd, J₁¼8.1 Hz, J₂¼0.6 Hz,1H, ArH on the ﬂuoreneunit), 7.65e7.58 (m,

3H, ArH on the ﬂuorene unit), 7.52e7.49 (m, 2H, ArH on the ﬂuorene

unit), 2.00e1.90 (t, J¼8.4 Hz, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.15e1.03 (m,12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.88e0.75 (t, J¼8.4 Hz,

6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.61e0.49 (m, 4H, eCH₂CH₂CH₂CH₂

CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative assignment based on

calculated values) d: 153.46 (aromatic carbon on the ﬂuorene unit),

150.99 (aromatic carbon on the ﬂuorene unit), 144.51 (aromatic

carbon on the ﬂuorene unit), 138.08 (aromatic carbon on the ﬂuo-

rene unit), 131.40 (aromatic carbon on the ﬂuorene unit), 130.51

(aromatic carbon on the ﬂuorene unit), 126.44 (aromatic carbon on

the ﬂuorene unit), 126.38 (aromatic carbon on the ﬂuorene unit),

123.17 (aromatic carbon on the ﬂuorene unit), 122.09 (aromatic

carbon on the ﬂuorene unit), 120.29 (aromatic carbon on the ﬂuo-

rene unit), 119.59 (carbon on the cyano group), 110.34 (aromatic

carbon on the ﬂuoreneunit), 55.75 (sp³-carbon on the ﬂuorene unit),

39.95 (carbon on the alkyl chain), 31.36 (carbon on the alkyl chain),

29.42 (carbon on the alkyl chain), 23.60 (carbon on the alkyl chain),

22.46 (carbon on the alkyl chain), 13.90 (carbon on the alkyl chain);

HRMS (m/z): [MþH]^þcalcd for C₂₆H₃₂BrN, 437.1718, found [(⁷⁹Br)

MþH]^þ¼438.1794; [(⁸¹Br)MþH]^þ¼440.1794.

on calculated values) d: 7.52e7.49 (m, 12H, ArH on the ﬂuorene

unit), 7.27e7.25 (m, 4H, ArH on the ﬂuorene unit), 7.25e7.20 (m,

16H, ArH on the diphenylamino group), 7.13e7.10 (d, J¼8.4 Hz, 24H,

ArH on the diphenylamino group), 7.01e6.95 (m, 20H, ArH on the

ﬂuorene unit), 5.98 (s, 1H, NH on the amino group), 2.04e1.82 (m,

5.3.13. 7-Bromo-9,9-dihexyl-9H-ﬂuorene-2-carboxylic acid (18). To

a mixture of compound 17 (2.7 g; 0.006 mol) in CH₃COOH (6 mL),

H₂SO₄(6 mL), and H₂O (6 mL) was stirred and reﬂuxed for 24 h.

After cooling to the room temperature, w50 mL of NaOH_(aq)was

added to the reaction mixture. The above solution was then

extracted with ethyl acetate and the organic layer was dried over

MgSO_4(S). After removing the solvent, the crude product was pu-

riﬁed through column chromatography on silica gel using ethyl

acetate/hexane (1:1) as the eluent to give the ﬁnal puriﬁed product

as white powder with yield of w97% (2.73 g). IR (KBr, cm^ꢁ1): 2952,

2928, 2856 (C(sp³)eH stretching absorptions), 1881 (C]O

stretching absorption) 1609, 1478 (stretching absorptions of ben-

zene rings), 1485 (CH₂bending absorption), 1377 (CH₃bending

absorption). Mp: 86.2e87.5. ¹H NMR (300 MHz, CDCl₃, tentative

24H,

eCH₂CH₂CH₂CH₂CH₂CH₃),

1.25e1.23

(m,

72H,

36H,

eCH₂CH₂CH₂CH₂CH₂CH₃),

0.80e0.78

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.65 (m, 24H, eCH₂CH₂CH₂CH₂CH₂CH₃);

¹³C NMR (75 MHz, CDCl₃, tentative assignment based on calculated

values) d: 152.83 (aromatic carbon on the ﬂuorene unit), 151.89

(aromatic carbon on the ﬂuorene unit), 147.21 (aromatic carbon on

the diphenylamino group), 147.05 (aromatic carbon on the ﬂuorene

unit), 139.22 (aromatic carbon on the ﬂuorene unit), 138.38 (aro-

matic carbon on the ﬂuorene unit), 137.85 (aromatic carbon on the

ﬂuorene unit), 135.28 (aromatic carbon on the ﬂuorene unit),

130.85 (aromatic carbon on the ﬂuorene unit), 129.83 (aromatic

carbon on the diphenylamino group), 126.79 (aromatic carbon on

the ﬂuorene unit), 124.81 (aromatic carbon on the ﬂuorene unit),

123.41 (aromatic carbon on the diphenylamino group), 122.85

(aromatic carbon on the ﬂuorene unit), 122.37 (aromatic carbon on

the ﬂuorene unit), 121.69 (aromatic carbon on the diphenylamino

group), 120.51 (aromatic carbon on the ﬂuorene unit), 120.36 (ar-

omatic carbon on the ﬂuorene unit),120.29 (aromatic carbon on the

assignment based on calculated values)

d: 8.17e8.14 (d, J¼7.8 Hz,

1H, ArH on the ﬂuorene unit), 8.10 (s, 1H, ArH on the ﬂuorene unit),

7.77e7.74 (d, J¼7.5 Hz, 1H, ArH on the ﬂuorene unit), 7.64e7.61 (d,

J¼8.1 Hz, 1H, ArH on the ﬂuorene unit), 7.52e7.48 (m, 2H, ArH on

the ﬂuorene unit), 2.16e1.91 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.14e1.05 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.78e0.74 (t,

J¼6.6 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.59 (m, 4H,

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4945

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

signment based on calculated values)

: 172.68 (sp²-carbon on the

16,651,881 (C]O stretching absorption), 1612, 1483 (stretching

absorptions of benzene rings), 1455 (CH₂bending absorption), 1376

(CH₃bending absorption), 1133 (CeN stretching absorption). ¹H

NMR (300 MHz, CDCl₃, tentative assignment based on calculated

d

carbonyl acid),154.10 (aromatic carbon on the ﬂuorene unit),150.51

(aromatic carbon on the ﬂuorene unit), 145.61 (aromatic carbon on

the ﬂuorene unit)138.74 (aromatic carbon on the ﬂuorene unit),

130.31 (aromatic carbon on the ﬂuorene unit), 129.75 (aromatic

carbon on the ﬂuorene unit), 128.10 (aromatic carbon on the ﬂuo-

rene unit), 126.39 (aromatic carbon on the ﬂuorene unit), 124.60

(aromatic carbon on the ﬂuorene unit), 122.77 (aromatic carbon on

the ﬂuorene unit), 122.06 (aromatic carbon on the ﬂuorene unit),

119.62 (aromatic carbon on the ﬂuorene unit), 55.61 (sp³-carbon on

the ﬂuorene unit), 40.08 (carbon on the alkyl chain), 31.43 (carbon

on the alkyl chain), 29.54 (carbon on the alkyl chain), 23.68 (carbon

on the alkyl chain), 22.52 (carbon on the alkyl chain), 13.95 (carbon

on the alkyl chain); HRMS (m/z): [MþH]^þcalcd for C₂₆H₃₃BrO₂,

457.1742, found [(⁷⁹Br)MþH]^þ¼457.1751; [(⁸¹Br)MþH]^þ¼459.1799.

values) d: 8.05 (s, 1H, ArH on the ﬂuorene unit), 7.84e7.74 (m, 2H,

ArH on the ﬂuorene unit), 7.70e7.67 (d, J¼7.8 Hz, 1H, ArH on the

ﬂuorene unit), 7.59e7.56 (d, J¼7.8 Hz, 1H, ArH on the ﬂuorene unit),

7.49 (s, 1H, ArH on the ﬂuorene unit), 4.24 (s, 3H, NH on the car-

bohydrazide unit), 2.10e1.86 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.12e1.01 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.77e0.72 (t,

J¼6.6 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.65e0.51(m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

signments based on calculated values) d

:168.79 (sp²-carbon on the

carbohydrazide unit), 153.56 (aromatic carbon on the ﬂuorene

unit), 150.83 (aromatic carbon on the ﬂuorene unit), 143.69 (aro-

matic carbon on the ﬂuorene unit), 138.76 (aromatic carbon on the

ﬂuorene unit), 131.30 (aromatic carbon on the ﬂuorene unit), 130.17

(aromatic carbon on the ﬂuorene unit), 126.26 (aromatic carbon on

the ﬂuorene unit), 125.76 (aromatic carbon on the ﬂuorene unit),

122.27 (aromatic carbon on the ﬂuorene unit), 121.74 (aromatic

carbon on the ﬂuorene unit), 121.66 (aromatic carbon on the ﬂuo-

rene unit), 119.68 (aromatic carbon on the ﬂuorene unit), 55.60

(sp³-carbon on the ﬂuorene unit), 40.09 (carbon on the alkyl chain),

31.37 (carbon on the alkyl chain), 29.48 (carbon on the alkyl chain),

23.62 (carbon on the alkyl chain), 22.45 (carbon on the alkyl chain),

13.87 (carbon on the alkyl chain); HRMS (m/z): [MþH]^þcalcd for

C₂₆H₃₅BrN₂O, 470.1933, found [(⁷⁹Br)MþH]^þ¼470.1931; [(⁸¹Br)

MþH]^þ¼472.1906.

5.3.14. 4-Methyl-7-bromo-9,9-dihexyl-9H-ﬂuorene-2-carboxylate

(19). To a mixture of compound 18 (2.6 g; 5.6 mmol) in methanol

(20 mL), and H₂SO₄(4 mL), was stirred and reﬂuxed for 6 h. After

cooling to the room temperature, w50 mL of NaOH_(aq)was added to

the reaction mixture. The above solution was then extracted with

ethyl acetate and the organic layer was dried over MgSO_4(S). After

removing the solvent, the crude product was puriﬁed through col-

umn chromatography on silica gel using ethyl acetate/hexane (1:20)

as the eluent to give the ﬁnal puriﬁed product as white powder with

yield of w93% (2.49 g). Mp: 73.8e75.1. IR (KBr, cm^ꢁ1): 2952, 2926,

2856 (C(sp³)eH stretching absorptions), 1719 (C]O stretching ab-

sorption) 1605,1474 (stretching absorptions of benzene rings),1465

(CH₂bending absorption), 1375 (CH₃bending absorption). ¹H NMR

(300 MHz, CDCl₃, tentative assignment based on calculated values)

5.3.16. 2-(7-Bromo-9,9-dihexyl-9H-ﬂuoren-2-yl)-5-(4-tert-butyl-

phenyl)-1,3,4-oxadiazole (21). Two-step reaction: (i) To a mixture of

compound 20 (2.25 g; 4.7 mmol) in THF (60 mL) was added 4-tert-

butylbenzoyl chloride (1.03 g; 5.2mmole), pyridine (3 mL). The

resulting solution was then heated and stirred for 12 h. After

cooling to the room temperature, the solvent was removed and the

crude solid product was collected and recrystallized from hexane.

The puriﬁed product was obtained as white powder with yield of

90.3% (2.72 g). ¹H NMR (300 MHz, CDCl₃, tentative assignment

d: 8.06e8.02 (dd, J₁¼7.8 Hz, J₂¼1.2 Hz,1H, ArH on the ﬂuorene unit),

7.99 (s,1H, ArH on the ﬂuorene unit), 7.71e7.68 (d, J¼7.8 Hz,1H, ArH

on the ﬂuorene unit), 7.61e7.58 (d, J¼7.8 Hz,1H, ArH on the ﬂuorene

unit), 7.49e7.46 (m, 2H, ArH on the ﬂuorene unit), 3.95 (s, 3H, CH₃on

the COOMe group), 2.06e1.88 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.13e1.01 (m,12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.78e0.73 (t, J¼6.9 Hz,

6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.61e0.51 (m, 4H, eCH₂CH₂

CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative assignment

based on calculated values)

d

: 10.16e10.14 (d, J¼5.4 Hz, 1H, NH on

based on calculated values)

d

: 167.31(sp²-carbon on the COOMe

the carbohydrazide unit), 9.81e9.79 (d, J¼5.4 Hz, 1H, NH on the

carbohydrazide unit), 7.96e7.92 (m, 2H, ArH on the ﬂuorene unit),

7.85e7.82 (d, J¼8.1 Hz, 2H, ArH on the phenyl group), 7.69e7.66 (d,

J¼8.1 Hz, 1H, ArH on the ﬂuorene unit), 7.57e7.54 (d, J¼8.4 Hz, 1H,

ArH on the ﬂuorene unit), 7.48e7.45 (m, 2H, ArH on the ﬂuorene

unit), 7.44e7.42 (d, J¼8.1 Hz, 2H, ArH on the phenyl group),

1.95e1.89 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃), 1.32 (s, 9H, CH₃on the

tert-butyl group), 1.11e0.93 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃),

0.74e0.68 (t, J¼6.9 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.50 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

group), 153.91 (aromatic carbon on the ﬂuorene unit), 150.35 (aro-

matic carbon on the ﬂuorene unit), 144.61 (aromatic carbon on the

ﬂuorene unit), 138.86 (aromatic carbon on the ﬂuorene unit),130.17

(aromatic carbon on the ﬂuorene unit), 128.90 (aromatic carbon on

the ﬂuorene unit), 126.30 (aromatic carbon on the ﬂuorene unit),

123.99 (aromatic carbon on the ﬂuorene unit), 122.40 (aromatic

carbon on the ﬂuorene unit), 121.83 (aromatic carbon on the ﬂuo-

rene unit),119.42 (aromatic carbon on the ﬂuorene unit), 55.53 (sp³-

carbon on the ﬂuorene unit), 52.03 (1^ꢃcarbon on the COOMe group),

40.05 (carbon on the alkyl chain), 31.37 (carbon on the alkyl chain),

29.48 (carbon on the alkyl chain), 23.60 (carbon on the alkyl chain),

22.45 (carbon on the alkyl chain), 13.86 (carbon on the alkyl chain);

HRMS (m/z): [MþH]^þcalcd for C₂₇H₃₅BrO₂, 470.1820, found [(⁷⁹Br)

MþH]^þ¼471.1900; [(⁸¹Br)MþH]^þ¼473.1900.

signment based on calculated values) d

:164.73 (sp²-carbon on the

carbohydrazide unit), 164.36 (sp²-carbon on the carbohydrazide

unit), 156.09 (aromatic carbon on the ﬂuorene unit), 153.77 (aro-

matic carbon on the phenyl group), 150.87 (aromatic carbon on the

ﬂuorene unit), 144.26 (aromatic carbon on the ﬂuorene unit),

138.80 (aromatic carbon on the ﬂuorene unit), 130.22 (aromatic

carbon on the phenyl group), 130.14 (aromatic carbon on the ﬂu-

orene unit), 128.44 (aromatic carbon on the ﬂuorene unit), 127.17

(aromatic carbon on the phenyl group), 126.91 (aromatic carbon on

the ﬂuorene unit), 126.33 (aromatic carbon on the ﬂuorene unit),

125.70 (aromatic carbon on the phenyl group), 122.43 (aromatic

carbon on the ﬂuorene unit), 121.84 (aromatic carbon on the ﬂuo-

rene unit), 121.79 (aromatic carbon on the ﬂuorene unit), 119.84

(aromatic carbon on the ﬂuorene unit), 55.72 (sp³-carbon on the

ﬂuorene unit), 40.12 (carbon on the alkyl chain), 35.02 (4^ꢃcarbon

on the tert-butyl group), 31.45 (carbon on the alkyl chain), 31.09 (1^ꢃ

carbon on the tert-butyl group), 29.52 (carbon on the alkyl chain),

5.3.15. 7-Bromo-9,9-dihexyl-9H-ﬂuorene-2-carbohydrazide (20). To

a mixture of compound 19 (2.4 g; 5.1 mmol) in methanol (20 mL),

was added hydrazine monohydrate (0.637 g; 0.01 mol), then stirred

and reﬂuxed for 24 h. The reaction mixture was then extracted with

dichloromethane (30mLꢀ3) and the organic layer was dried over

MgSO_4(S). After removing the solvent, the crude product was pu-

riﬁed by column chromatography on silica gel using ethyl acetate/

hexane (1:1) to give the ﬁnal puriﬁed product as white powder

with yield of 91.6% (2.28 g). Mp: 155.3e157.1. IR (KBr, cm^ꢁ1): 3293

(NeH stretching absorption), 3066 (C(sp²)eH stretching absorp-

tion), 2955, 2925, 2854 (C(sp³)eH stretching absorptions),

4946

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

23.70 (carbon on the alkyl chain), 22.52 (carbon on the alkyl chain),

13.93 (carbon on the alkyl chain); HRMS (m/z): HRMS (m/z):

[MþH]^þcalcd for C₃₇H₄₇BrN₂O₂, 631.6853, found [({79}Br)

MþH]^þ¼631.2908; [({81}Br)MþH]^þ¼633.2892.

¹H NMR (300 MHz, CDCl₃, tentative assignment based on calculated

values) : 8.12e8.08 (m, 4H, ArH on the ﬂuorene unit), 7.74e7.71 (d,,

d

ArH on the ﬂuorene unit 1H, ArH on the ﬂuorene unit), 7.62e7.55

(m, 7H, ArH on the ﬂuorene unit), 7.49e7.44 (m, 4H, ArH on the

phenyl group), 7.30e7.28 (m, 3H, ArH on the ﬂuorene unit),

7.09e7.03 (m, 3H, ArH on the ﬂuorene unit), 2.08e1.82 (m, 12H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.38 (s, 9H, CH₃on the tert-butyl group),

1.17e1.09 (m, 36H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.90e0.78 (m, 30H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.31 (s, 18H, CH₃on the TMS unit); ¹³C

NMR (75 MHz, CDCl₃, tentative assignments based on calculated

(ii) The compound from the previous step was suspended in

POCl₃(45 mL) and heated to reﬂux for 6 h. After cooling to the room

temperature, 50 mL of ice water was added to the reaction mixture.

After ﬁltration, the crude solid product was collected and recrys-

tallized from methanol. The puriﬁed product was obtained as white

powder with yield of w79% (2.09 g). Mp: 99.8e103.3. IR (KBr,

cm^ꢁ1): 3066 (C(sp²)eH stretching absorption), 2954, 2928, 2856

(C(sp³)eH stretching absorptions), 1614, 1468 (stretching absorp-

tions of benzene rings), 1581 (C]N stretching absorption), 1461

(CH₂bending absorption), 1364 (CH₃bending absorption), 1300

(AreN stretching absorption), 1268 (CeOeC stretching absorption).

¹H NMR (300 MHz, CDCl₃, tentative assignment based on calculated

values) d:165.16 (aromatic carbon on the oxadiazole group), 164.38

(aromatic carbon on the oxadiazole group), 155.11 (aromatic carbon

on the ﬂuorene unit),152.77 (aromatic carbon on the ﬂuorene unit),

152.23 (aromatic carbon on the ﬂuorene unit), 151.18 (aromatic

carbon on the ﬂuorene unit), 149.57 (aromatic carbon on the ﬂuo-

rene unit), 148.30 (aromatic carbon on the phenyl group), 146.87

(aromatic carbon on the ﬂuorene unit), 144.72 (aromatic carbon on

the ﬂuorene unit), 141.49 (aromatic carbon on the ﬂuorene unit),

138.14 (aromatic carbon on the ﬂuorene unit), 136.44 (aromatic

carbon on the ﬂuorene unit), 134.19 (aromatic carbon on the ﬂuo-

rene unit), 131.85 (aromatic carbon on the ﬂuorene unit), 127.38

(aromatic carbon on the phenyl group), 126.7 (aromatic carbon on

the ﬂuorene unit)5, 126.15 (aromatic carbon on the ﬂuorene unit),

126.00 (aromatic carbon on the phenyl group), 123.28 (aromatic

carbon on the phenyl group), 122.44 (aromatic carbon on the ﬂu-

orene unit), 121.30 (aromatic carbon on the ﬂuorene unit), 121.08

(aromatic carbon on the ﬂuorene unit), 120.47 (aromatic carbon on

the ﬂuorene unit), 119.27 (aromatic carbon on the ﬂuorene unit),

118.65 (aromatic carbon on the ﬂuorene unit), 118.36 (aromatic

carbon on the ﬂuorene unit), 117.20 (aromatic carbon on the ﬂuo-

rene unit), 55.41 (sp³-carbon on the ﬂuorene unit), 55.01 (sp³-car-

bon on the ﬂuorene unit), 40.31 (carbon on the alkyl chain), 40.12

(carbon on the alkyl chain), 35.04 (4^ꢃcarbon on the tert-butyl

group), 31.66 (1^ꢃcarbon on the tert-butyl group), 31.51 (carbon on

the alkyl chain), 31.11 (carbon on the alkyl chain), 29.67 (carbon on

the alkyl chain), 29.59 (carbon on the alkyl chain), 23.85 (carbon on

the alkyl chain), 23.78 (carbon on the alkyl chain), 22.58 (carbon on

the alkyl chain), 22.51 (carbon on the alkyl chain), 14.05 (carbon on

the alkyl chain), ꢁ0.88 (1^ꢃcarbon on the TMS unit); HRMS (m/z):

values) d: 8.14e8.12 (m, 2H, ArH on the ﬂuorene unit), 8.11e8.09 (d,

J¼8.1 Hz, 2H, ArH on the phenyl group), 7.80e7.78 (d, J¼8.1 Hz, 1H,

ArH on the ﬂuorene unit), 7.62e7.52 (m, 3H, ArH on the ﬂuorene

unit), 7.50e7.47 (d, J¼8.1 Hz, 2H, ArH on the phenyl group),

2.13e1.94 (m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃), 1.37 (s, 9H, CH₃on the

tert-butyl group), 1.14e1.05 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃),

0.77e0.72 (t, J¼7.2 Hz, 6H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.65e0.60

(m, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, ten-

tative assignment based on calculated values) d: 164.76 (aromatic

carbon on the oxadiazole group), 164.49 (aromatic carbon on the

oxadiazole group), 155.18 (aromatic carbon on the ﬂuorene unit),

153.47 (aromatic carbon on the ﬂuorene unit), 151.13 (aromatic

carbon on the phenyl group), 143.43 (aromatic carbon on the ﬂu-

orene unit), 138.80 (aromatic carbon on the ﬂuorene unit), 130.23

(aromatic carbon on the ﬂuorene unit), 126.70 (aromatic carbon on

the phenyl group), 126.24 (aromatic carbon on the ﬂuorene unit),

126.02 (aromatic carbon on the ﬂuorene unit), 125.94 (aromatic

carbon on the phenyl group), 122.72 (aromatic carbon on the

phenyl group), 122.35 (aromatic carbon on the ﬂuorene unit),

121.65 (aromatic carbon on the ﬂuorene unit), 121.19 (aromatic

carbon on the ﬂuorene unit), 121.07 (aromatic carbon on the ﬂuo-

rene unit), 120.20 (aromatic carbon on the ﬂuorene unit), 55.69

(sp³-carbon on the ﬂuorene unit), 40.12 (carbon on the alkyl chain),

34.97 (4^ꢃcarbon on the tert-butyl group), 31.37 (carbon on the alkyl

chain), 31.02 (1^ꢃcarbon on the tert-butyl group), 29.46 (carbon on

the alkyl chain), 23.63 (carbon on the alkyl chain), 22.44 (carbon on

the alkyl chain), 13.87 (carbon on the alkyl chain); HRMS (m/z):

HRMS (m/z): [MþH]^þcalcd for C₃₇H₄₅BrN₂O, 612.2715, found

[(⁷⁹Br)MþH]^þ¼612.2719; [(⁸¹Br)MþH]^þ¼614.2722.

M

^þcalcd for C₉₃H₁₂₇N₃OSi₂1357.9518, found 1360.2367.

(ii) To a solution of compound from the ﬁrst step (0.62 g;

0.46 mmol) in CH₂Cl₂(10 mL) was added iodine monochloride

(0.16 g; 0.96mmole) at 0 ^ꢃC, then warmed to room temperature and

stirred for 4 h. w30 mL of saturated NaHSO₃solutions was added

into the reaction mixture. The above solution was then extracted

with dichloromethane (30mLꢀ3) and the organic layer was dried

over MgSO_4(S). After removing the solvent, the crude product was

puriﬁed bycolumn chromatography on silica gel using ethyl acetate/

hexane (1:20) to give the ﬁnal puriﬁed product as yellow powder

with yield of w91% (0.61 g). Mp: 103.1e105.4. IR (KBr, cm^ꢁ1): 3062,

3035 (C(sp²)eH stretching absorptions), 2953, 2925, 2854(C(sp³)eH

stretching absorptions), 1604, 1483 (stretching absorptions of ben-

zene rings), 1576 (C]N stretching absorption) 1456 (CH₂bending

absorption), 1375 (CH₃bending absorption), 1340 (AreN stretching

absorption), 1268 (CeOeC stretching absorption). ¹H NMR

(300 MHz, CDCl₃, tentative assignment based on calculated values)

5.3.17. N-(7-(5-(4-tert-Butylphenyl)-1,3,4-oxadiazol-2-yl)-9,9-

dihexyl-9H-ﬂuoren-2-yl)-N-(9,9-dihexyl-7-iodo-9H-ﬂuoren-2-yl)-

9,9-dihexyl-7-iodo-9H-ﬂuoren-2-amine (22). Two-step reaction: (i)

To a mixture of compound 21 (0.37 g; 0.603 mmol), and 13 (0.5 g;

0.603 mmol) in dry toluene (15 mL) was added Pd₂(dba)₃(1.1 mg;

0.012 mmol), sodium tert-butoxide (0.069 g; 0.724 mmol), P(t-Bu)₃

(4.9 mg; 0.024 mmol) and stirred at 90 ^ꢃC under Ar atmosphere for

12 h. After cooling to the room temperature, w100 mL of H₂O was

added to the reaction mixture. The above solution was then

extracted with ethyl acetate and the organic layer was dried over

MgSO_4(S). After removing the solvent, the crude product was pu-

riﬁed through column chromatography on silica gel using ethyl

acetate/hexane (1:20) as the eluent to give the ﬁnal puriﬁed

product as light yellow powder with yield of 75.6% (0.62 g). Mp:

101.1e102.3. IR (KBr, cm^ꢁ1): 3040, 3014 (C(sp²)eH stretching ab-

sorptions), 2954, 2927, 2856 (C(sp³)eH stretching absorptions),

1603, 1483 (stretching absorptions of benzene rings), 1577 (C]N

stretching absorption), 1462 (CH₂bending absorption), 1376 (CH₃

bending absorption), 1329 (AreN stretching absorption), 1266

(CeOeC stretching absorption), 1247(SieC stretching absorption).

d: 8.12e8.08 (m, 4H, ArH on the ﬂuorene unit), 7.74e7.71 (dd,

J₁¼8.4 Hz, J₂¼2.1 Hz,1H, ArH on the ﬂuorene unit), 7.64e7.55 (m, 7H,

ArH on the ﬂuorene unit), 7.54e7.51 (d, J¼8.4 Hz, 2H, ArH on the

phenyl group), 7.37e7.34 (dd, J₁¼8.4 Hz, J₂¼2.1 Hz, 2H, ArH on the

phenyl group), 7.26e7.22 (m, 4H, ArH on the ﬂuorene unit),

7.05e7.01 (dd, J₁¼8.1 Hz, J₂¼2.1 Hz, 2H, ArH on the ﬂuorene unit),

2.07e1.79 (m,12H, eCH₂CH₂CH₂CH₂CH₂CH₃),1.38 (s, 9H, CH₃on the

tert-butyl group), 1.17e1.08(m, 36H, eCH₂CH₂CH₂CH₂CH₂CH₃),

0.84e0.76(m, 18H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.68 (br, 12H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4947

assignment based on calculated values)

d

: 165.00 (aromatic carbon

(aromatic carbon on the diphenylamino group), 122.94 (aromatic

carbon on the diphenylamino group), 122.73 (aromatic carbon on

the phenyl group), 121.27 (aromatic carbon on the ﬂuorene unit),

121.09 (aromatic carbon on the ﬂuorene unit), 121.00 (aromatic

carbon on the ﬂuorene unit), 120.89 (aromatic carbon on the ﬂu-

orene unit), 119.25 (aromatic carbon on the ﬂuorene unit), 118.40

(aromatic carbon on the ﬂuorene unit), 55.17 (sp³-carbon on the

ﬂuorene unit), 39.95 (carbon on the alkyl chain), 34.79 (4^ꢃcarbon

on the tert-butyl group), 31.30 (carbon on the alkyl chain), 30.90 (1^ꢃ

carbon on the tert-butyl group), 29.36 (carbon on the alkyl chain),

23.60 (carbon on the alkyl chain), 22.31 (carbon on the alkyl chain),

13.82 (carbon on the alkyl chain); HRMS (m/z): M^þcalcd for

C₄₉H₅₅N₃O, 701.4345, found, 701.4351.

on the oxadiazole group),164.31 (aromatic carbon on the oxadiazole

group), 155.01 (aromatic carbon on the ﬂuorene unit), 152.77 (aro-

matic carbon on the ﬂuorene unit), 152.00 (aromatic carbon on the

ﬂuorene unit), 151.47 (aromatic carbon on the ﬂuorene unit), 151.10

(aromatic carbon on the phenyl group), 147.86 (aromatic carbon on

the ﬂuorene unit), 147.14 (aromatic carbon on the ﬂuorene unit),

144.42 (aromatic carbon on the ﬂuorene unit), 140.38 (aromatic

carbon on the ﬂuorene unit), 135.81 (aromatic carbon on the ﬂuo-

rene unit), 135.32 (aromatic carbon on the ﬂuorene unit), 134.58

(aromatic carbon on the ﬂuorene unit), 131.80 (aromatic carbon on

the ﬂuorene unit), 126.67 (aromatic carbon on the phenyl group),

125.92 (aromatic carbon on the phenyl group), 123.26 (aromatic

carbon on the ﬂuorene unit),122.66 (aromatic carbon on the phenyl

group), 121.44 (aromatic carbon on the ﬂuorene unit), 121.19 (aro-

matic carbon on the ﬂuorene unit), 120.72 (aromatic carbon on the

ﬂuorene unit),120.54 (aromatic carbon on the ﬂuorene unit),119.33

(aromatic carbon on the ﬂuorene unit), 118.25 (aromatic carbon on

the ﬂuorene unit), 117.46 (aromatic carbon on the ﬂuorene unit),

91.66 (aromatic carbon on the ﬂuorene unit), 55.35 (sp³-carbon on

the ﬂuorene unit), 55.23 (sp³-carbon on the ﬂuorene unit), 40.13

(carbonon thealkylchain), 34.95(4^ꢃcarbonon thetert-butylgroup),

31.55 (1^ꢃcarbon on the tert-butyl group), 31.05 (carbon on the alkyl

chain), 29.56 (carbon on the alkyl chain), 23.77 (carbon on the alkyl

chain), 22.51 (carbon on the alkyl chain), 14.03 (carbon on the alkyl

chain); HRMS (m/z): M^þcalcd for C₈₇H₁₀₉I₂N₃O 1465.666, found,

1467.6660.

5.3.19. Compound 2. To a mixture of compound 21 (0.32 g;

0.521 mmol), and 10 (0.53 g; 0.521 mmol) in dry toluene (15 mL)

was added Pd₂(dba)₃(9.55 mg; 0.011 mmol), sodium tert-butoxide

(0.06 g; 0.626 mmol), P(t-Bu)₃(4.2 mg; 0.021 mmol) and stirred at

90 ^ꢃC under Ar atmosphere for 12 h. After cooling to the room

temperature, w100 mL of H₂O was added to the reaction mixture.

The above solution was then extracted with ethyl acetate and the

organic layer was dried over MgSO_4(S). After removing the solvent,

the crude product was puriﬁed through column chromatography

on silica gel using ethyl acetate/hexane (1:10) as the eluent to give

the ﬁnal puriﬁed product as yellow powder with yield of 80.6%

(0.65 g). Mp: 103.3e105.7. IR (KBr, cm^ꢁ1): 3066 (C(sp²)eH

stretching absorption), 2953, 2925, 2856 (C(sp³)eH stretching ab-

sorptions), 1598, 1482 (stretching absorptions of benzene rings),

1593 (C]N stretching absorption) 1454 (CH₂bending absorption),

1384 (CH₃bending absorption), 1312 (AreN stretching absorption),

1270 (CeOeC stretching absorption). ¹H NMR (300 MHz, CDCl₃,

5.3.18. Compound 1. To

a mixture of compound 8 (0.5 g;

0.88 mmol) in dry pyridine (12 mL) was added 4-tert-butylbenzoyl

chloride (0.2 g; 1.05 mmol), then stirred and reﬂuxed under Ar

atmosphere for 4 h. After cooling to the room temperature, the

reaction mixture was extracted with ethyl acetate and the organic

layer was dried over MgSO_4(S). After removing the solvent, the

crude product was puriﬁed through column chromatography on

silica gel using ethyl acetate/hexane (1:10) as the eluent to give the

ﬁnal light yellow powder with yield of 91% (0.56 g). Mp:

117.1e118.0. IR (KBr, cm^ꢁ1): 3060, 3033 (C(sp²)eH stretching ab-

sorptions), 2952, 2925, 2853 (C(sp³)eH stretching absorptions),

1610, 1492 (stretching absorptions of benzene rings), 1541 (C]N

stretching absorption), 1461 (CH₂bending absorption), 1384 (CH₃

bending absorption), 1300 (AreN stretching absorption), 1271

(CeOeC stretching absorption). ¹H NMR (300 MHz, CDCl₃, tentative

tentative assignment based on calculated values) d: 8.11e8.06 (m,

4H, ArH on the ﬂuorene unit), 7.73e7.70 (d, J¼7.8 Hz,1H, ArH on the

ﬂuorene unit), 7.59e7.54 (m, 3H, ArH on the ﬂuorene unit),

7.50e7.47 (d, J¼7.8 Hz, 4H, ArH on the phenyl group), 7.26e7.21 (m,

12H, ArH on the diphenylamino group and ArH on the ﬂuorene

unit), 7.12e7.09 (d, J¼7.8 Hz 10H, ArH on the diphenylamino group

and ArH on the ﬂuorene unit), 7.06e6.96 (m, 8H, ArH on the

diphenylamino

group),

2.06e1.76

(m,

12H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.38 (s, 9H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.19e1.07 (m, 36H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.84e0.71 (m, 30H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

signment based on calculated values) d:165.16 (aromatic carbon on

assignment based on calculated values)

d

: 8.12 (s, 1H, ArH on the

the oxadiazole group), 164.38 (aromatic carbon on the oxadiazole

group), 155.14 (aromatic carbon on the ﬂuorene unit), 152.74 (ar-

omatic carbon on the ﬂuorene unit), 151.94 (aromatic carbon on the

ﬂuorene unit), 151.86 (aromatic carbon on the ﬂuorene unit), 151.15

(aromatic carbon on the phenyl group), 148.32 (aromatic carbon on

the ﬂuorene unit), 148.00 (aromatic carbon on the diphenylamino

group), 146.49 (aromatic carbon on the ﬂuorene unit), 146.16 (ar-

omatic carbon on the ﬂuorene unit),144.73 (aromatic carbon on the

ﬂuorene unit), 136.26 (aromatic carbon on the ﬂuorene unit),

136.21 (aromatic carbon on the ﬂuorene unit), 133.99 (aromatic

carbon on the ﬂuorene unit), 129.10 (aromatic carbon on the

diphenylamino group), 126.75 (aromatic carbon on the phenyl

group), 126.00 (aromatic carbon on the phenyl group), 123.81 (ar-

omatic carbon on the ﬂuorene unit),123.61 (aromatic carbon on the

ﬂuorene unit), 123.41 (aromatic carbon on the diphenylamino

group), 122.32 (aromatic carbon on the phenyl group), 122.22 (ar-

omatic carbon on the diphenylamino group), 121.12 (aromatic car-

bon on the ﬂuorene unit), 121.04 (aromatic carbon on the ﬂuorene

unit), 119.74 (aromatic carbon on the ﬂuorene unit), 119.54 (aro-

matic carbon on the ﬂuorene unit), 119.22 (aromatic carbon on the

ﬂuorene unit), 118.61 (aromatic carbon on the ﬂuorene unit), 116.93

(aromatic carbon on the ﬂuorene unit), 115.11 (aromatic carbon on

the ﬂuorene unit), 55.06 (sp³-carbon on the ﬂuorene unit), 40.18

ﬂuorene unit), 8.09e8.06 (m, 2H, ArH on the ﬂuorene unit),

7.75e7.72 (d, J¼8.4 Hz, 2H, ArH on the ﬂuorene unit), 7.63e7.60 (d,

J¼8.4 Hz, 1H, ArH on the ﬂuorene unit), 7.59e7.55 (dd, J₁¼8.4 Hz,

J₂¼2.1 Hz, 2H, ArH on the phenyl group), 7.30(s, 1H, ArH on the

ﬂuorene unit), 7.27e7.24 (m, 4H, ArH on the diphenylamino group),

7.15e7.11 (m, 2H, ArH on the diphenylamino group), 7.11e7.09 (m,

2H, ArH on the phenyl group), 7.07e7.01 (m, 4H, ArH on the

diphenylamino

group),

2.04e1.83

(m,

4H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.38 (s, 9H, CH₃on the tert-butyl group),

1.17e1.06 (m, 12H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.81e0.76 (t, 6H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 0.66 (br, 4H, eCH₂CH₂CH₂CH₂CH₂CH₃);

¹³C NMR (75 MHz, CDCl₃, tentative assignment based on calculated

values) d:164.88 (aromatic carbon on the oxadiazole group), 164.15

(aromatic carbon on the oxadiazole group), 154.85 (aromatic car-

bon on the ﬂuorene unit), 152.68 (aromatic carbon on the ﬂuorene

unit), 151.22 (aromatic carbon on the phenyl group), 148.16 (aro-

matic carbon on the ﬂuorene unit), 147.55 (aromatic carbon on the

diphenylamino group), 144.39 (aromatic carbon on the ﬂuorene

unit), 134.43 (aromatic carbon on the ﬂuorene unit), 129.04 (aro-

matic carbon on the diphenylamino group), 126.55 (aromatic car-

bon on the phenyl group), 125.89 (aromatic carbon on the phenyl

group), 125.77 (aromatic carbon on the ﬂuorene unit), 123.97

4948

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

(carbon on the alkyl chain), 35.06(4^ꢃcarbon on the tert-butyl

group), 31.66 (carbon on the alkyl chain), 31.12(1^ꢃcarbon on the

tert-butyl group), 29.65 (carbon on the alkyl chain), 23.92 (carbon

on the alkyl chain), 22.57 (carbon on the alkyl chain), 14.09; HRMS

(m/z): M^þcalcd for C₁₁₁H₁₂₉N₅O 1548.0197, found, 1548.0194.

under Ar atmosphere for 12 h. After cooling to the room tempera-

ture, w100 mL of H₂O was added to the reaction mixture. The above

solution was then extracted with ethyl acetate and the organic layer

was dried over MgSO_4(S). After removing the solvent, the crude

product was puriﬁed through column chromatography on silica gel

using ethyl acetate/hexane (1:30) as the eluent to give the ﬁnal

puriﬁed product as yellow powder with yield of 50% (0.27 g). Mp:

98.6e99.4. IR (KBr, cm^ꢁ1): 3061, 3033 (C(sp²)eH stretching ab-

sorptions), 2953, 2925, 2854 (C(sp³)eH stretching absorptions),

1603, 1482 (stretching absorptions of benzene rings), 1588 (C]N

stretching absorption) 1464 (CH₂bending absorption), 1376 (CH₃

bending absorption), 1310 (AreN stretching absorption), 1269

(CeOeC stretching absorption). ¹H NMR (300 MHz, CDCl₃, tentative

5.3.20. Compound 3. To

a mixture of compound 21 (0.1 g;

0.163 mmol), and 16 (0.44 g; 0.163 mmol) in dry toluene (15 mL) was

added Pd₂(dba)₃(3 mg; 0.003 mmol), sodium tert-butoxide (0.018 g;

0.1955 mmol), P(t-Bu)₃(1.3 mg; 0.006518 mmol) and stirred at 90 ^ꢃC

under Ar atmosphere for 12 h. After cooling to the room temperature,

w100 mL of H₂O was added to the reaction mixture. The above so-

lutionwasthen extracted withethyl acetate and theorganic layerwas

dried over MgSO_4(S). After removing the solvent, the crude product

was puriﬁed through column chromatography on silica gel using

ethyl acetate/hexane (1:15) as the eluent to give the ﬁnal puriﬁed

product as yellow powder with yield of 73.1% (0.386 g). Mp:

100.1e102.3. IR (KBr, cm^ꢁ1): 3059, 3034 (C(sp²)eH stretching ab-

sorptions), 2954, 2926, 2855 (C(sp³)eH stretching absorptions),1600,

1483 (stretching absorptions of benzene rings),1541 (C]N stretching

absorption) 1464 (CH₂bending absorption), 1376 (CH₃bending ab-

sorption), 1311 (AreN stretching absorption), 1270 (CeOeC stretch-

ing absorption). ¹H NMR (300 MHz, CDCl₃, tentative assignment

assignment based on calculated values) d: 8.12e8.07 (m, 8H, ArH on

the ﬂuorene unit), 7.74e7.71 (d, J¼8.1 Hz, 4H, ArH on the ﬂuorene

unit), 7.60e7.55 (m, 4H, ArH on the phenyl group), 7.51e7.45 (m,

20H, ArH on the ﬂuorene unit), 7.26e7.21 (m, 56H, ArH on the

diphenylamino group and ArH on the ﬂuorene unit), 7.13e7.10 (d,

J¼8.4 Hz, 42H, ArH on the diphenylamino group and ArH on the

ﬂuorene unit), 7.06e6.96, (m, 38H, ArH on the diphenylamino group

and ArH on the ﬂuorene unit), 2.31e2.17 (m, 4H,

eCH₂CH₂CH₂CH₂CH₂CH₃),

1.81e1.78

(m,

56H,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.38 (s, 9H, CH₃on the tert-butyl group),

1.25e1.08 (m, 180H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.88e0.75 (m, 150H,

eCH₂CH₂CH₂CH₂CH₂CH₃); ¹³C NMR (75 MHz, CDCl₃, tentative as-

based on calculated values) d: 8.11e8.07 (m, 8H, ArH on the ﬂuorene

unit), 7.73e7.70 (d, J¼8.1 Hz, 2H, ArH on the ﬂuorene unit), 7.60e7.55

(m, 8H, ArH on the ﬂuorene unit), 7.51e7.48 (d, J¼8.1 Hz, 4H, ArH on

the phenyl group), 7.27e7.22 (m, 28H, ArH on the diphenylamino

group and ArH on the ﬂuorene unit), 7.13e7.10 (m, 18H, ArH on the

diphenylamino group and ArH on the ﬂuorene unit), 7.07e6.97 (m,

16H, ArH on the diphenylamino group), 2.06e1.77 (m, 28H,,

eCH₂CH₂CH₂CH₂CH₂CH₃), 1.38 (s, 9H, eCH₂CH₂CH₂CH₂CH₂CH₃),

1.17e1.08 (m, 84H, eCH₂CH₂CH₂CH₂CH₂CH₃), 0.85e0.75 (m, 70H,

eCH₂CH₂CH₂CH₂CH₂CH₃); C NMR (75 MHz, CDCl₃, tentative assign-

signment based on calculated values) d: 165.15 (aromatic carbon on

the oxadiazole group), 164.35 (aromatic carbon on the oxadiazole

group), 155.08 (aromatic carbon on the ﬂuorene unit), 152.76 (aro-

matic carbon on the ﬂuorene unit), 151.83 (aromatic carbon on the

ﬂuorene unit), 151.79 (aromatic carbon on the ﬂuorene unit), 151.13

(aromatic carbon on the phenyl group), 148.38 (aromatic carbon on

the ﬂuorene unit), 148.00 (aromatic carbon on the diphenylamino

group), 146.65 (aromatic carbon on the ﬂuorene unit), 146.53 (aro-

matic carbon on the ﬂuorene unit), 146.32 (aromatic carbon on the

ﬂuorene unit), 146.10 (aromatic carbon on the ﬂuorene unit), 144.74

(aromatic carbon on the ﬂuorene unit), 136.39 (aromatic carbon on

the ﬂuorene unit), 135.69 (aromatic carbon on the ﬂuorene unit),

133.88 (aromatic carbon on the ﬂuorene unit), 129.07 (aromatic

carbon on the diphenylamino group), 128.43 (aromatic carbon on

the ﬂuorene unit), 126.74 (aromatic carbon on the phenyl group),

126.00 (aromatic carbon on the phenyl group), 123.86 (aromatic

carbon on the ﬂuorene unit), 123.55 (aromatic carbon on the

diphenylamino group), 123.03 (aromatic carbon on the ﬂuorene

unit),122.82 (aromatic carbon on the diphenylamino group),122.26

(aromatic carbon on the phenyl group), 121.26 (aromatic carbon on

the ﬂuorene unit), 121.06 (aromatic carbon on the ﬂuorene unit),

119.64 (aromatic carbon on the ﬂuorene unit), 118.84 (aromatic

carbon on the ﬂuoreneunit),117.99 (aromatic carbon on the ﬂuorene

unit),116.70 (aromaticcarbonon theﬂuorene unit),112.60 (aromatic

carbon on the ﬂuoreneunit), 55.02 (sp³-carbon on the ﬂuorene unit),

40.21 (carbon on the alkyl chain), 35.05(4^ꢃcarbon on the tert-butyl

group), 31.65 (carbon on the alkyl chain), 31.11(1^ꢃcarbon on the tert-

butyl group), 29.76 (carbon on the alkyl chain), 23.91 (carbon on the

alkyl chain), 22.56 (carbon on the alkyl chain), 14.09 (carbon on the

alkyl chain); HRMS (m/z): M^þcalcd for HRMS (m/z): M^þcalcd for

C₄₈₃H₅₇₃N₁₇O 6627.5309, found, 6627.0708.

ment based on calculated values) d: 165.13 (aromatic carbon on the

oxadiazole group),164.33 (aromatic carbon on the oxadiazole group),

155.09 (aromatic carbon on the ﬂuorene unit), 152.70 (aromatic car-

bon on the ﬂuorene unit), 151.90 (aromatic carbon on the ﬂuorene

unit), 151.81 (aromatic carbon on the ﬂuorene unit), 151.10 (aromatic

carbon on the phenyl group),148.28 (aromatic carbon on the ﬂuorene

unit), 147.95 (aromatic carbon on the diphenylamino group), 146.45

(aromaticcarbonontheﬂuoreneunit),146.11(aromaticcarbononthe

ﬂuorene unit), 144.70 (aromatic carbon on the ﬂuorene unit), 136.22

(aromatic carbon on the ﬂuorene unit), 136.16 (aromatic carbon on

the ﬂuorene unit), 135.65 (aromatic carbon on the ﬂuorene unit),

133.95 (aromatic carbon on the ﬂuorene unit), 129.65 (aromatic car-

bon on the ﬂuorene unit), 129.06 (aromatic carbon on the dipheny-

lamino group),126.71 (aromatic carbon on the phenyl group),125.97

(aromatic carbon on the phenyl group), 123.75 (aromatic carbon on

the ﬂuorene unit), 123.57 (aromatic carbon on the diphenylamino

group),122.28 (aromatic carbon on the diphenylamino group),121.20

(aromatic carbon on the phenyl group), 121.02 (aromatic carbon on

the ﬂuorene unit), 119.76 (aromatic carbon on the ﬂuorene unit),

119.49 (aromatic carbon on the ﬂuorene unit), 119.20 (aromatic car-

bon on the ﬂuorene unit), 118.56 (aromatic carbon on the ﬂuorene

unit),116.87(aromaticcarbononthe ﬂuoreneunit), 55.02(sp³-carbon

on the ﬂuorene unit), 40.15 (carbon on the alkyl chain), 35.02 (4^ꢃ

carbon on the tert-butyl group), 31.62 (carbon on the alkyl chain),

31.08 (1^ꢃcarbon on the tert-butyl group), 29.62 (carbon on the alkyl

chain), 23.88 (carbon on the alkyl chain), 22.54 (carbon on the alkyl

chain), 14.06 (carbon on the alkyl chain); HRMS (m/z): M^þcalcd for

C₂₃₅H₂₇₇N₉O 3243.77, found, 3244.8767.

Acknowledgements

We thank National Science Council (NSC), Taiwan for the ﬁnan-

cial support.

5.3.21. Compound 4. To a mixture of compound 22 (0.12 g;

0.082 mmol), and 16 (0.44 g; 0.163 mmol) in dry toluene (15 mL) was

added Pd₂(dba)₃(3 mg; 0.003 mmol), sodium tert-butoxide (0.019 g;

0.196 mmol), P(t-Bu)₃(1.3 mg; 0.0065 mmol) and stirred at 90 ^ꢃC

Supplementary data

Supplementary data related to this article can be found online at

doi:10.1016/j.tet.2012.04.073.

T.-C. Lin et al. / Tetrahedron 68 (2012) 4935e4949

4949

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Article Doi

Two-photon absorption and effective optical power-limiting properties of small dendritic chromophores derived from functionalized fluorene/oxadiazole units

DOI: 10.1016/j.tet.2012.04.073

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