One-pot synthesis of partially fluorinated naphthalene, anthracene, and chrysene derivatives

Article abstract of DOI:10.1016/j.tetlet.2007.12.127

A series of partially fluorinated naphthalene, anthracene, and chrysene derivatives have been synthesized by a convenient one-pot reaction of multi-fluorinated aromatics and 1,4-dilithio-1,2,3,4-tetraaryl-1,3-butadiene that was generated in situ from the reduction of diphenylacetylene derivatives with lithium naphthalenide.

Full text of DOI:10.1016/j.tetlet.2007.12.127

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 1690–1693
One-pot synthesis of partially fluorinated naphthalene,
anthracene, and chrysene derivatives
Shuhong Li a, Junfeng Xiang b, Xuening Mei b, Caihong Xu b,*
a Department of Chemical Engineering, Beijing Technology and Business University, Beijing 100037, China
b Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
Received 24 August 2007; revised 20 December 2007; accepted 25 December 2007
Available online 8 January 2008
Abstract
A series of partially fluorinated naphthalene, anthracene, and chrysene derivatives have been synthesized by a convenient one-pot
reaction of multi-fluorinated aromatics and 1,4-dilithio-1,2,3,4-tetraaryl-1,3-butadiene that was generated in situ from the reduction
of diphenylacetylene derivatives with lithium naphthalenide.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Diphenylacetylene; Lithium naphthalenide; Reduction; Fluorinated acene
Polycyclic aromatic acenes (PAH) have received con-
siderable interest in the past few decades due to their poten-
tial application for the construction of organic electronic
devices.1 Tuning of molecular properties, such as solubility,
stability, and charge mobility by functionalization is the
most active aspect in current synthetic research for PAH.
Especially, there has been increasing interest in the incorpo-
ration of fluorine into acenes, which may contribute to tun-
ing the electronic properties, and altering p-stacking in the
solid state by exploiting aryl–fluoroaryl interactions.2–8
Recently, Watson and Piers independently reported the
synthesis of partially fluorinated polycyclic aromatic com-
pounds by lithium–bromine exchange of 2,20-dibromobiar-
yls and nucleophilic substitutions of aromatic fluorines.2,3
Anthony reported the synthesis of partially fluorinated
pentacenes via quinone routes.4 Xi prepared the partially
fluorinated naphthalene derivatives from the reaction of
1,4-dilithio-1,3-dienes and hexafluorobenzene.5 Swager
and co-workers also reported the synthesis of a series of
fluorine-containing tetracene derivatives with N-methyl-
1,2,3,4-tetrafluoroisoindole as a synthetic building block.6
Very recently, Tilley’s group published their efforts on
developing an n-type organic semiconductor by using
9,10-dichlorooctafluoroanthracene as a viable building
block.7
Here, we present the results of our initial studies aimed
at establishing a new one-pot synthetic protocol to synthe-
size partially fluorinated acenes. This method allowed us to
synthesize a series of partially fluorinated naphthalene,
anthracene, and chrysene derivatives.
The preparation of 1,4-dilithio-1,2,3,4-tetraaryl-1,3-
butadiene 2 from the reaction of diphenylacetylene deriva-
tives with metal lithium has been well studied,9 and now is
commonly used in the synthesis of silole derivatives.10 Our
continuing interest in the construction of ladder-type
p-conjugated molecules by the reductive cyclization of
acetylene derivatives11 led us to investigate the reduction
of diphenylacetylene with lithium naphthalenide (LiNaph)
and to expand this reaction in the synthesis of other ladder
molecules.
We found that by the treatment of 1a (R = H) with
1 equiv of LiNaph at room temperature, 1,4-dilithio-
1,2,3,4-tetraphenyl-1,3-butadiene 2a was produced in mod-
erate to good yield within 5 min, which was indicated by the
formation of 1,2,3,4-tetraphenyl-1,3-butadiene when the
reaction mixture was quenched with water. In this reaction,
*
Corresponding author. Tel./fax: +86 10 6255 4487.
E-mail address: caihong@iccas.ac.cn (C. Xu).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.12.127

S. Li et al. / Tetrahedron Letters 49 (2008) 1690–1693
1691
the use of 1 equiv of LiNaph was crucial. When 2 equiv or
more of LiNaph was used, 1,2-dilithio-1,2-diphenyl-ethyl-
ene was the major product.12
F
F
F
F
F
F
F
F
F
Then, we examined the reaction of 2a prepared in situ
from 1a with hexafluorobenzene. Thus, the treatment of
2a with 1 equiv of hexafluorobenzene in THF followed
by workup and chromatographic purification produced
3a as a white solid in 30% yield.13,14 Similarly, starting
from 1b produced 3b in 29% yield (Scheme 1).
F
5
7
Interestingly, during the purification of 3a, a trace
amount of 4a was isolated as a byproduct. This result sug-
gests that terminal fluorine-substituted ‘unsymmetrical’
naphthalene 3 and central fluorine-substituted ‘symmetri-
cal’ anthracene 4 could be synthesized with this one-pot
procedure. As a test, the reaction between 2a and
0.5 equiv of hexafluorobenzene was carried out and, as
expected, 4a was obtained in 7% yield as a bright-yellow
solid15 (Scheme 2).
F
F
F
F
F
F
F
F
F
F
8
6
Structures of 5, 6, 7, and 8
Encouraged by the results, we further investigated the
reaction of 2a with perfluoronaphthalene (C10F8), expect-
ing that the procedure would provide a simple synthetic
way to produce partially fluorinated tetracene 5. However,
chrysene 6 was produced as the major product when 2a was
treated with 0.5 equiv of C10F8, which was isolated as a
yellow solid in 9% yield, while the expected 5 was not
obtained. Similarly, anthracene 7 was not the major com-
ponent in the mixed products when the reaction was car-
ried between 2a and the excess amount of C10F8.
Compound 7 was only isolated in 2% yield together with
6% of phenanthrene 8.
Single crystals of 3a and 4a suitable for X-ray diffraction
were obtained from THF/ethanol and CH2Cl2/hexane
solution, respectively. Their molecular structure is shown
in Figure 1. Compound 3a crystallized in the orthorhombic
space group Pbca. It has a partial face-to-face antiparallel
˚
p-stacking motif with the shortest C–C contact of 3.35 A
between two antiparallel molecules. The anthracene core
of 4a shows a coplanar conformation which is different
from that of highly twisted decaphenylanthracene,16 which
can be attributed to the reduced size of substituents at 9, 10
positions from phenyl groups to fluorine.
Though all attempts to prepare single crystal of 6, 7, and
8 failed, their structures could be determined by the analy-
sis of 1H, 19F NMR, high resolution mass spectra (HRMS),
and UV–vis spectra.17 Compounds 7 and 8 have exactly the
same molecular weight as indicated by their HRMS data.
However, their 19F NMR spectra are distinguishable from
each other. There are only three resonance signals for 7 but
six for 8 in the 19F NMR spectra. This fact suggests the
existence of six different types of fluorine atom in com-
pound 8, while 7 has more symmetric structure. Further
elucidation of structures of 7 and 8 was also conducted
by means of the combination of 2D homo- and hetero-
nuclear experiments (see Supplementary data).
The data of UV–vis spectra also prove the assignment of
molecular structures. The normalized UV–vis spectra and
emission spectra of acene derivatives 3a, 4a, and 6–8 are
shown in Figures 2 and 3, respectively. For the linear acene
3a, 7, and 4a, both the absorption and emission maxima
shift to longer wavelength with the increase of p-conju-
gation. The non-linear 6 and 8 show a similar trend. In
the area of longer wavelength, the non-linear isomer 8
exhibits broader absorption peaks, while 7 has some of
the fine vibronic structures. Notably, both 7 and 4a show
typical absorption band arising from anthracene backbone.
In summary, we report a convenient one-pot synthesis of
highly aryl-substituted fluorinated acenes by the reaction
R
R
R
R
R
R
F
F
F
F
i
ii
Li
Li
R
R
R
3a (R = H) 30% from 1a
3b (R = Me) 29% from 1b
R
1a-b
2a-b
Scheme 1. Reagents and conditions: (i) LiNaph (1 mol amt.), THF, rt,
5 min; (ii) C6F6 (excess), THF, rt, 2 h.
F
1) LiNaph (1 mol amt.)
THF, r. t., 5 min
2) C6F6 (0.25 mol amt.)
THF, r. t., 2 h
F
1a
4a
Scheme 2.

1692
S. Li et al. / Tetrahedron Letters 49 (2008) 1690–1693
3a
4a
7
6
8
300
350
400
450
500
550
600
650
Wavelength (nm)
Fig. 3. Normalized emission spectra of acene derivatives in THF.
polycyclic aromatic hydrocarbons, which have potential
application as new materials for organic electronic devices.
Studies involving the optimization of the reaction condi-
tions, examination of the applicable scale for acetylene
derivatives, and the electronic properties of the present
compounds are underway.
Acknowledgments
We are grateful to the National Natural Science Foun-
dation of China (50673094) for financial support. We also
express our appreciation to Professor Zhaohui Wang for
his helpful discussions.
Fig. 1. ORTEP drawings of compounds (a) 3a and (b) 4a (50%
probability for thermal ellipsoids. Hydrogen atoms are omitted for
clarity).
of multi-fluorinated aromatics and 1,4-dilithio-1,2,3,
4-tetraaryl-1,3-butadiene generated in situ from the
reduction of diphenylacetylene derivatives with lithium
naphthalenide. This new protocol is expected to provide
a facile entry to a variety of substituted fluorine-containing
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
2007.12.127.
References and notes
3a
4a
7
1. For recent reviews, see: (a) Bendikov, M.; Wudl, F.; Perepichka, D. F.
Chem. Rev. 2004, 104, 4891; (b) Anthony, J. E. Chem. Rev. 2006, 106,
5028; (c) Pascal, R. A., Jr. Chem. Rev. 2006, 106, 4809.
2. Cho, D. M.; Parkin, S. R.; Watson, M. D. Org. Lett. 2005, 7,
1067.
6
8
3. Morrison, D. J.; Trefz, T. K.; Piers, W. E.; McDonald, R.; Parvez, M.
J. Org. Chem. 2005, 70, 5309.
4. Swartz, C. R.; Parkin, S. R.; Bullock, J. E.; Anthony, J. E.; Mayer, A.
C.; Malliaras, G. G. Org. Lett. 2005, 7, 3163.
5. Wang, Z.; Wang, C.; Xi, Z. Tetrahedron Lett. 2006, 47, 4157.
6. Chen, Z.; Muller, P.; Swager, T. M. Org. Lett. 2006, 8, 273.
7. Tannaci, J. F.; Noji, M.; McBee, J.; Tilley, T. Don. J. Org. Chem.
2007, 72, 5567.
8. (a) Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.;
Inoue, Y.; Sato, F.; Tokito, S. J. Am. Chem. Soc. 2004, 126, 8138; (b)
Inoue, Y.; Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.;
Tokito, S. Jpn. J. Appl. Phys. 2005, 44, 3663; (c) Babudri, F.;
Farinola, G. M.; Naso, F.; Ragni, R. Chem. Commun. 2007, 1003.
250
300
350
400
450
500
Wavelength (nm)
Fig. 2. Normalized absorption spectra of acene derivatives in THF.

S. Li et al. / Tetrahedron Letters 49 (2008) 1690–1693
1693
3
9. (a) Smith, I. I.; Hoehn, H. H. J. Am. Chem. Soc. 1941, 63, 1184;
V = 4989.0(17) A .
Z = 8,
Dc = 1.343 Mg mꢀ3
,
l(Mo Ka) =
˚
(b) Braye, E. H.; Hubel, W.; Caplier, I. J. Am. Chem. Soc. 1961, 83,
0.098 mmꢀ1
, T = 295 (2) K, F(000) = 2080, 2hmax = 55°. 36,938
¨
4406.
Reflections measured, of which 5573 was unique (Rint = 0.0414). Final
R1 = 0.0708 with wR2 = 0.2150 for 3709 reflections with I > 2r(I).
15. Compound 4a: This compound was prepared essentially in the
same manner as described for 3a in 7% yield except for using
0.5 equiv of C6F6. Bright-yellow solid. Mp >300 °C 1H NMR
(600 MHz, CD2Cl2, ppm) d 6.70–6.71 (m, 4H), 6.76–6.83 (m, 16H),
6.97–7.05 (m, 20H); HRMS (EI): Calcd for C62H40F2: 822.3098.
Found: 822.3093 (M+). Crystallographic data: C62H40F2, FW =
822.94, crystal dimension 0.18 ꢁ 0.16 ꢁ 0.08 mm3, monoclinic, space
10. For recent examples, see: (a) Zhan, X.; Risko, C.; Amy, F.; Chan, C.;
´
Zhao, W.; Barlow, S.; Kahn, A.; Bredas, J.-L.; Marder, S. R. J. Am.
Chem. Soc. 2005, 127, 6335; (b) Li, Z.; Dong, Y.; Mi, B.; Tang, Y.;
Ha¨ussler, M.; Tong, H.; Dong, Y.; Lam, J. W. Y.; Ren, Y.; Sung, H.
H. Y.; Wong, K. S.; Gao, P.; Williams, I. D.; Kwok, H. S.; Tang, B.
Z. J. Phys. Chem. B 2005, 109, 10061.
11. (a) Yamaguchi, S.; Xu, C.; Tamao, K. J. Am. Chem. Soc. 2003, 125,
13662; (b) Xu, C.; Wakamiya, A.; Yamaguchi, S. J. Am. Chem. Soc.
2005, 127, 1638; (c) Yamaguchi, S.; Xu, C.; Yamada, H.; Wakamiya,
A. J. Organomet. Chem. 2005, 690, 5365.
12. 1,2-Diphenylethene was formed in good yield when water was used as
quenching reagent.
13. Synthesis of 3a with other method: (a) Grugel, C.; Neumann, W. P.;
Schriewer, M. Angew. Chem., Int. Ed. Engl. 1979, 18, 543; (b) Sartori,
P.; Golloch, A. Chem. Ber. 1970, 103, 313.
˚
˚
˚
group P2(1)/c, a = 6.477(3) A, b = 15.423(8) A, c = 21.836(11) A.
3
˚
a = 90.00°, b = 93.678°, c = 90.00°. V = 2176.9(19) A . Z = 2,
Dc = 1.255 Mg mꢀ3
,
l(Mo Ka) = 0.077 mmꢀ1
,
T = 294 (2) K,
F(000) = 860. 23,780 Reflections measured, of which 4410 was
unique (Rint = 0.000). Final R1 = 0.0824 with wR2 = 0.1840 for 2670
reflections with I > 2r(I).
16. Qiao, X.; Padula, M. A.; Ho, D. M.; Vogelaar, N. J.; Schutt, C. E.;
Pascal, R. A., Jr. J. Am. Chem. Soc. 1996, 118, 741.
14. A typical procedure for the preparation of 3a: A mixture of granular
lithium (18.2 mg, 2.6 mmol) and naphthalene (336.3 mg, 2.6 mmol) in
THF was stirred at room temperature (rt) for 4 h. To the resulting
solution of lithium naphthalenide was added a solution of diphenyl-
acetylene (311.6 mg, 1.75 mmol) in THF (4 mL) at room temperature.
After stirring for 20 min, hexafluorobenzene (0.25 mL, 2.14 mmol)
was added to the reaction mixture at room temperature. The reaction
mixture was stirred for 1 h and then quenched with a saturated
aqueous solution of NH4Cl. The mixture was extracted with either
ethyl ether or ether. The organic layer was washed with brine, dried
over MgSO4, filtered, and concentrated under reduced pressure. The
resulting mixture was passed through a silica gel column with
petroleum ether (Rf = 0.2) as an eluent, followed by further purifica-
tion by recrystallization (THF/ethanol) to give 133.2 mg of 3a in 30%
yield as a colorless crystal. Mp 259–260 °C. 1H NMR (600 MHz,
CDCl3, ppm) d 6.73–6.75 (m, 4H), 6.78–6.85 (m, 6H), 7.12–7.17 (m,
10H); 19F NMR (400 MHz, CDCl3, ppm) d ꢀ136.40, ꢀ159.01; 13C
NMR (150.9 MHz, CDCl3, ppm) d 142.20, 140.09, 138.87, 134.69,
130.87, 129.79, 127.01, 126.55, 126.51, 125.70, 118.85; HRMS (EI):
Calcd for C34H20F4: 504.15011. Found: 504.15005 (M+). Crystallo-
graphic data: C34H20F4, FW = 504.50, crystal dimension 0.52 ꢁ 0.31 ꢁ
17. Compound 3b: White solid. Mp 252–254 °C. 1H NMR (400 MHz,
CDCl3) d 2.00 (s, 6H), 2.20 (s, 6H), 6.51–6.57 (m, 8H), 6.87–6.93 (m,
8H); 19F NMR (400 MHz, CDCl3) d ꢀ135.685 (m, J = 1.88 Hz),
ꢀ158.735 (m, J = 1.88 Hz); 13C NMR (150.9 MHz, CDCl3, ppm) d
142.50, 137.36, 136.09, 135.74, 134.74, 134.63, 130.68, 129.62, 127.67,
127.20, 119.03, 21.24, 21.04. HRMS (EI) Calcd for C38H28F4:
560.2127. Found: 560.2133 (M+). Compound 6: Yellow solid. Mp
>300 °C. 1H NMR (400 MHz, C4D8O), d 6.70–6.73 (m, 4H), 6.74–
6.80 (m, 10H), 6.85–6.86 (m, 6H), 6.98–7.08 (m, 20H); 19F NMR
(400 MHz, THF, ppm), d ꢀ130.22 (d, J = 7.53 Hz), ꢀ138.64 (d,
J = 7.53 Hz); HRMS (EI) Calcd for C66H40F4: 908.3066. Found:
908.3077 (M+). Compound 7: Yellow solid. Mp 291–293 °C 1H NMR
(600 MHz, CDCl3, ppm), d 6.74–6.75 (m, 4H), 6.81–6.83 (m, 6H),
7.15–7.17 (m, 10H), 19F NMR (400 MHz, CDCl3, ppm) d ꢀ111.74 (d,
J = 37.65 Hz), ꢀ145.975 (d, J = 39.53 Hz), ꢀ157.16; HRMS (EI):
Calcd for C38H20F6: 590.1469. Found: 590.1475 (M+). Compound 8:
White solid. Mp 219–221 °C 1H NMR (600 MHz, CDCl3, ppm), d
6.64–6.69 (m, 4H), 6.81 (m, 2H), 6.87–6.94 (m, 6H), 7.01 (m, 2H),
7.08–7.14 (m, 6H); 19F NMR (400 MHz, CDCl3, ppm) d ꢀ123.82,
ꢀ136.29, ꢀ148.38 (d, J = 32.00 Hz), ꢀ149.65 (m, J = 23.53 Hz),
ꢀ156.29 (t, J = 18.82 Hz), ꢀ158.98 (t, J = 22.59 Hz); HRMS (EI):
Calcd for C38H20F6: 590.1469. Found: 590.1473 (M+).
0.17 mm3, orthorhombic, space group Pbca, a = 6.6985(13) A,
˚
˚
˚
b = 22.946(5) A, c = 32.459(7) A. a = 90.00°, b = 90.00°, c = 90.00°.