Synthesis and crystal structure of polyaryl substituted diene derivatives based on the reduction of diphenylacetylene with lithium naphthalenide

Article abstract of DOI:10.1016/j.cclet.2011.10.009

The reduction of diphenylacetylene with lithium naphthalenide produced two kinds of intermediates, 1 or 2, depending on the ratio of diphenylacetylene to lithium naphthalenide. A series of polyaryl substituted ethylene/diene derivatives were synthesized b

Full text of DOI:10.1016/j.cclet.2011.10.009

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Chinese Chemical Letters 23 (2012) 69–72
www.elsevier.com/locate/cclet
Synthesis and crystal structure of polyaryl substituted diene
derivatives based on the reduction of diphenylacetylene
with lithium naphthalenide
b
b,
Shu Hong Li a, , Liang Chun Li , Cai Hong Xu
*
*
a Department of Chemistry, School of Science, Beijing Technology and Business University, Beijing 100048, China
b Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Received 7 July 2011
Available online 9 November 2011
Abstract
The reduction of diphenylacetylene with lithium naphthalenide produced two kinds of intermediates, 1 or 2, depending on the
ratio of diphenylacetylene to lithium naphthalenide. A series of polyaryl substituted ethylene/diene derivatives were synthesized by
reaction of electrophiles with the corresponding intermediates produced in situ. All new compounds were fully characterized, and
their single crystal structures were determined.
# 2011 Shu Hong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Lithium naphthalenide; Reduction; Diphenylacetylene; Diene derivatives
The reduction of diphenylacetylene (DPA) or its derivatives with metallic reagents was an old and contemporary
research, and much attention has been focused on the use of metal lithium as reductant [1–5]. On the other hand,
lithium naphthalenide (LiNaph) is easily prepared by reaction of metallic lithium with naphthalene in THF and has
been demonstrated to be an effective reductant in synthesis of 2,5-difunctional silole derivatives [6], p-conjugated
ladder type molecules containing silicon- [7] or carbon- [8] bridge, with diethynylsilanes and (o-silylphenyl)-
acetylene derivatives as starting materials, respectively. These reactions proceeded well under mild conditions and
produced target molecules in moderate to good yields. However, only limit attention was paid on the reduction of
unsubstituted DPA with LiNaph and the use of the reaction to synthesize siloles and other p-electron molecules
[4,9,10].
Our interest in synthesis of ring-fused p-electron molecules by reduction of acetylene derivatives prompted us
investigate the reaction of DPAwith LiNaph. We found in a solution of THF, by tuning the ratio of DPA to LiNaph, two
different reactive intermediates, 1,2-dilithio-1,2-diphenylethene (1) and 1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene
(2), were easily prepared in fair yields. We envisioned this reduction system may provide a convenient access to various
polyaryl substitutedethylene and diene derivatives. In this paper, wewould like to report synthesis of polyaryl substituted
ethylene and diene derivatives by combination of the reduction reaction system with various electrophiles.
* Corresponding authors.
E-mail addresses: lish@th.btbu.edu.cn (S.H. Li), caihong@iccas.ac.cn (C.H. Xu).
1001-8417/$ – see front matter # 2011 Shu Hong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.10.009

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S.H. Li et al. / Chinese Chemical Letters 23 (2012) 69–72
1. Experimental
1
Melting points were measured on a melting point apparatus with a microscope, H and 13C NMR spectra were
measured with a Bruker AVANCE 400 or Bruker AVANCE 600 spectrometer. Single crystal X-ray diffraction
measurements were performed with Rigaku or Bruker single crystal diffractometer. Tetrahydrofuran (THF) and
acetone were dried by normal procedures and distilled under an inert atmosphere before use, and all reactions were
carried out under nitrogen atmosphere.
Synthesis of (Z)-2,5-dimethyl-3,4-diphenylhex-3-ene-2,5-diol (3a): To the solution of lithium naphthalenide
prepared from granular lithium (17.4 mg, 2.5 mmol) and naphthalene (320 mg, 2.5 mmol) in THF (10 mL) was added
a solution of diphenylacetylene (178 mg, 1.0 mmol) in THF (3 mL) at room temperature. After stirring for 5 min, the
new distilled acetone (0.18 mL, 2.4 mmol) was added to the reaction mixture at room temperature and stirred for 2 h.
After normal work up, the mixture was passed through the silica gel column (petroleum ether/AcOEt) and re-
crystallized from ethanol to give 92 mg (0.31 mmol) of 3a in 31% yield as a colorless solid. Mp 189–190 8C, 1H NMR
(400 MHz, CDCl3): d 6.95 (t, 4H, J = 7.2 Hz); 6.87 (t, 2H, J = 7.0 Hz); 6.80 (d, 4H, J = 7.5 Hz); 1.41 (s, 12H); 4.08 (s,
2H). 13C NMR (100 MHz, CDCl3): d 145.75, 143.24, 142.06, 129.96, 126.90, 126.81, 125.69, 125.10, 74.08, 32.45,
31.85; HRMS (SIMS): Calcd. for C20H24O2: 296.1776. Found: 319.1667(M+Na).
Synthesis of (5,5-dimethylcyclopenta-1,3-diene-1,2,3,4-tetrayl) tetrabenzene (4a): The compound 4a was prepared
in the similar manner as described for 3a in 20% yield as a colorless solid with the molar ratio of LiNaph to DPA was
1.2. Mp 192–194 8C, 1H NMR (600 MHz, CDCl3): d 6.90–7.33 (m, 20H); 1.38(s, 6H). 13C NMR (150 MHz, CDCl3): d
152.34, 140.16, 137.49, 135.78, 130.17, 127.95, 127.27, 126.55, 126.03, 56.19, 22.19; HRMS (EI): Calcd. for C31H26:
398.2035. Found: 398.2039.
Synthesis of (2Z,4Z)-1,1,2,3,4,5,6,6-octaphenylhexa-2,4-diene-1,6-diol (5a): The compound 5a was prepared in the
similar manner as described for 3a in 39% yield as a colorless solid with the molar ratio of LiNaph to DPAwas 1.2 and
benzophenone as an electrophile. Mp 234–236 8C, 1H NMR (400 MHz, CDCl3): d 6.54–6.86 (m, 20H); 7.07–7.17 (m,
12H), 7.28 (s, 8H), 5.16 (s, 2H). 13C NMR (100 MHz, CDCl3): d 146.95, 144.62, 143.95, 142.70, 142.36, 141.53,
131.80, 128.95, 127.41, 127.15, 127.06, 126.79, 126.61, 126.26, 125.69, 125.42, 85.40; HRMS (SIMS): Calcd. for
C54H42O2: 722.3185. Found: 745.3052 (M+Na).
2. Results and discussion
The reductant, LiNaph, was prepared in situ by reaction of equal molar amount of lithium and naphthalene in THF
at room temperature. The followed reaction of DPAwith LiNaph was carried out by addition of a THF solution of DPA
to the as prepared LiNaph/THF mixture under N2 atmosphere. The reaction proceed very fast at room temperature,
accompanied by disappearance of dark green color, the characteristics of LiNaph, within 5 min after addition of DPA
(see Scheme 1).
Upon change in the ratio of DPA to LiNaph, two different dilithium adducts can be formed as major in reactive
intermediates. Thus, when the molar ratio of LiNaph to DPA is 2 or more, the dominative reactive intermediate is
dilithium adduct 1, which was confirmed by isolation of (Z)-diphenylethylene in 42% yield when the reaction mixture
Li
Li
R
R
ii
R = C(CH3)2-OH
i
3a
1
iv
iii
DPA
or
OH
Ph
Li
Li
HO
Ph
Ph
Ph
2
4a
5a
Scheme 1. The reaction mechanism based on the reduction of DPA with LiNaph. (i) LiNaph, the molar ratio of LiNaph to DPA is about 2.5. (ii)
Electrophile (acetone). (iii) LiNaph, the molar ratio of LiNaph to DPA is about 1.2. (iv) Electrophiles (acetone or benzophenone).

S.H. Li et al. / Chinese Chemical Letters 23 (2012) 69–72
71
Fig. 1. ORTEP drawings of the compounds (A) 4a and (B) 5a and crystal packing of 5a (C) along b axis in 1,4-dioxane (50% probability for thermal
ellipsoids, hydrogen atoms are omitted for clarity).
was quenched with water. However, the reaction of DPA with LiNaph in 1:1 molar ratio yields dilithium adduct 2 as
main intermediate species, and (Z)-1,2,3,4-tetraphenyl-1,3-butadiene was obtained in 60% yield after protonation of
the reaction mixture with H2O. Dilithium adduct 2 as well as other 1,4-dilithio-1,3-butadienes with various
substituents on the butadienyl skeleton have recently drawn intensive attention in construction of various new
compounds, such as silole derivatives and partially fluorinated p-conjugated compounds [4,9–11]. This work provides
a convenient approach to design such molecules.
We examined the reaction of intermediates 1 and 2 with several electrophiles, and found polyaryl substituted
ethylene/diene derivatives were easily achieved by combination of appropriate electrophile and corresponding
intermediate.
The reaction of intermediate 1 with acetone was first investigated. Thus, the reaction of an excess amount of acetone
with intermediate 1 generated in situ from equimolar ratio of LiNaph and DPA produced (Z)-2,5-dimethyl-3,4-
diphenylhex-3-ene-2,5-diol (3a) as a colorless crystal. The structure of 3a was well confirmed by NMR, HRMS, and
single-crystal X-ray analysis [12]. No E-isomer of the compound 3a was obtained, suggesting the electrophile addition
of acetone to dilithio intermediate 1 prefers to form Z-isomer.
However, the replacement of acetone with benzophenone failed to afford expected 1,1,2,3,4,4-hexaphenylbut-2-
ene-1,4-diol, the analogue of 3a. This may be attributed to synergistic steric hindrance caused by phenyl group of
ketone and short distance between the two C-Li moieties of intermediate 1.
The reactions between intermediate 2 and acetone, benzophenone were also examined, respectively.
Cyclopentadiene derivative 4a, (5,5-dimethulcyclopenta-1,3-diene-1,2,3,4-tetrayl) tetrabenzene, was the only
isolated compound when 2 reacted with acetone. The structure of 4a is similar to that of 1,1-dimethyl-2,3,4,5-
tetraphenyl-1H-silole. 4a also showed the phenomenon of aggregation induced emission that commonly existed for
silole derivatives. However, the use of benzophenone resulted in formation of uncyclized diene 5a, (2Z,4Z)-
1,1,2,3,4,5,6,6-octaphenylhexa-2,4-diene-1,6-diol, and no corresponding cyclopentadiene derivative was obtained.
These results suggest that benzophenone is different from acetone as an electrophile because of phenyl ring’s
electronic structure and hindrance effect.
Single crystals of 4a and 5a suitable for X-ray diffraction were obtained from ethanol and THF solution,
respectively. Their molecular structure was shown in Fig. 1. 4a crystallized in the monoclinic space group P21/n, and
four phenyl groups were distributed around cyclopentadiene ring like propeller. Compound 5a crystallized in the
triclinic space group P-1. In crystal structure, the molecule of 5a adopt a cis-conformation and the two hydroxyl
groups stick out like antennae to capture disorder solvent molecules THF through hydroxyl bond interaction.
Interestingly, single crystal of compound 5a obtained from 1,4-dioxane adopts monoclinic space group P21/c, and
Fig. 1c shows the crystal packing along b axis. There also exists hydroxyl interaction between the molecules of 5a and
1,4-dioxane.
3. Conclusion
Upon changing the molar ratio of LiNaph to DPA, two dilithio intermediates, 1,2-dilithio-1,2-diphenylethene (1)
and 1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene (2) can be prepared. By choice of intermediates and electrophiles,

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S.H. Li et al. / Chinese Chemical Letters 23 (2012) 69–72
various polyaryl substituted diene derivatives were achieved. The reaction system may provide a new approach to
construct p-electron molecules.
Acknowledgments
The authors gratefully acknowledge the National Science Foundation of China (Nos. 50673094 and 20774102) for
financial support.
References
[1] (a) A.F. Thompson Jr., S.B. Wyatt, J. Am. Chem. Soc. 62 (1940) 2555;
(b) L.I. Smith, H.H. Hoehn, J. Am. Chem. Soc. 63 (1941) 1184.
[2] (a) J. Tsuji, T. Nogi, J. Am. Chem. Soc. 88 (1966) 1289;
(b) J.E. Mulvaney, S. Groen, L.J. Carr, et al. J. Am. Chem. Soc. 91 (1969) 388;
(c) G. Levin, J. Jagur-Grodzinski, M. Szwarc, J. Am. Chem. Soc. 92 (1970) 2268.
[3] (a) J. Dubac, A. Laporterie, G. Manuel, Chem. Rev. (1990) 215;
(b) A. Maercker, M. Kemmer, H.C. Wang, et al. Angew. Chem., Int. Ed. Engl. 37 (1998) 2136;
(c) K. Ueura, T. Satoh, M. Miura, Org. Lett. 9 (2007) 1407.
[4] (a) B.Z. Tang, X. Zhan, G. Yu, et al. J. Mater. Chem. 11 (2001) 2974;
(b) Z. Li, Y.Q. Dong, J.W.Y. Lam, et al. Adv. Funct. Mater. 19 (2009) 905;
(c) X. Zhan, C. Risko, F. Amy, et al. J. Am. Chem. Soc. 127 (2005) 9021;
(d) H.J. Son, W.S. Han, J.Y. Chun, et al. Organometallics 26 (2007) 519.
[5] (a) C. Wang, Q. Luo, H. Sun, et al. J. Am. Chem. Soc. 129 (2007) 3094;
(b) N.F. Mckinley, D.F. O’Shea, J. Org. Chem. 71 (2006) 9552.
[6] K. Tamao, S. Yamaguchi, M. Shiro, J. Am. Chem. Soc. 116 (1994) 11715.
[7] (a) S. Yamaguchi, C. Xu, K. Tamao, J. Am. Chem. Soc. 125 (2003) 13662;
(b) C. Xu, A. Wakamiya, S. Yamaguchi, J. Am. Chem. Soc. 127 (2005) 1638;
(c) C. Xu, A. Wakamiya, S. Yamaguchi, Org. Lett. 6 (2004) 3707.
[8] X. Zhu, C. Mitsui, H. Tsuji, et al. J. Am. Chem. Soc. 131 (2009) 13596.
[9] S. Li, J. Xiang, X. Mei, et al. Tetrahedron Lett. 49 (2008) 1690.
[10] Z. Xi, Acc. Chem. Res. 43 (2010) 1342.
[11] P.F. Hudrlik, D. Dai, A.M. Hudrlik, J. Organomet. Chem. 691 (2006) 1257.
[12] S. Li, C. Xu, Acta Crystallogr. Sect. E 63 (2007) O4200.