Synthesis of unsymmetrically substituted pyrene derivatives through (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane

Article abstract of DOI:10.1016/j.tetlet.2011.09.089

A straightforward route to unsymmetrically functionalized pyrene derivatives is described involving the synthesis of key precursor (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane 1. In a first step bromide 1 was successful in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions. Subsequent transformation of the trimethylsilyl group to bromide enabled the introduction of a second variable functional group onto the pyrene skeleton.

Full text of DOI:10.1016/j.tetlet.2011.09.089

Tetrahedron Letters 52 (2011) 6284–6287
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of unsymmetrically substituted pyrene derivatives through
(6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane
⇑
Akihiro H. Sato, Mine Maeda, Shigenori Mihara, Tetsuo Iwasawa
Department of Materials Chemistry, Faculty of Science and Technology, Ryukoku University, Otsu, Shiga 520-2194, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2011
Revised 14 September 2011
Accepted 16 September 2011
Available online 22 September 2011
A straightforward route to unsymmetrically functionalized pyrene derivatives is described involving the
synthesis of key precursor (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane 1. In a first step bromide 1
was successful in Suzuki–Miyaura, Sonogashira, and Buchwald–Hartwig cross-coupling reactions. Subse-
quent transformation of the trimethylsilyl group to bromide enabled the introduction of a second vari-
able functional group onto the pyrene skeleton.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Pyrene
Unsymmetrical functionalization
Optelectronic organic devices
1,6-Disubstituted pyrene
Multi-functionalization of pyrene ring is attracting significant
interest in organic materials science, because it allows manipula-
tion of the spectroscopic and opto-electronic properties of pyr-
ene.1,2 Subtle changes in structure or composition of pyrene
derivatives can greatly alter their properties as electronic organic
devices.3 Among synthetic precursors for a poly-functionalized
pyrene, a multi-brominated pyrene is one of the most valuable
Next, TMS group was converted to bromide and it was readily
transformed via Suzuki–Miyaura, Sonogashira and Buchwald–Har-
twig reactions. Thus, it provides a convenient access to unsymmet-
rically functionalized pyrenes.
At the outset of our study the key precursor 1 was designed
with three features in mind. The two butyl groups were included
to provide solubility in various organic solvents.15 The Br substitu-
ent is the first reactive site, and the TMS group serves as a synthon
for a second reactive Br group that can be unveiled after our first
cross-coupling. As a minor point the TMS group is also expected
to increase solubility.
The key intermediate 1 was synthesized from pyrene as shown
in Scheme 2. The reaction of pyrene with bromine in CCl416 gave an
isomeric mixture of 1,6- and 1,8-dibromopyrene,17 and the single
operation of recrystallization from toluene afforded 1,6-dibromop-
yrene in ca. 30% yield with >83% purity.18,19 Initial efforts to con-
vert 1,6-dibromopyrene to the corresponding 1,6-dioctylpyrene
or 1,6-didodecylpyrene proved difficult due to the numerous
amounts of n-butylated pyrene byproducts. Presumably the 1,6-
dilithiated pyrene immediately reacted with 1-bromobutane that
was produced by lithium-halogen exchange between n-BuLi and
1,6-dibromopyrene. Thus, dialkylation reaction was performed
with 1-bromobutane, and it was followed by dibromination at
the 3,8-positions, giving 1,6-dibromo-3,8-dibutylpyrene in 65%
(two steps). Lithiation of 1,6-dibromo-3,8-dibutylpyrene smoothly
proceeded with THF as an additive, and the reaction with chlorotri-
methylsilane gave 1 in 70% yield.20 According to this process, ca.
25 g of 1 was prepared in all. The direct mono-lithiation of
1,6-dibromopyrene was not successful even though the amount
of n-BuLi was controlled, presumably due to the low solubility into
building blocks on the basis of
a transition-metal-catalyzed
cross-coupling strategy.3–5 For example, 1,3,6,8-tetrabromopy-
rene6 was used as a starting material of cross-coupling reactions
to synthesize symmetrical pyrene derivatives for the study of
organic electronics7 and piezochromic8 materials. 1,3-9 and 1,8-
dibromopyrene3 were also transformed into symmetrical
derivatives through Pd-catalyzed cross-coupling reactions to
develop the unique radical material10 and macrocyclic organic de-
vice.11 In addition, lithiation also works to activate multi-bromi-
nated pyrene,12 for example, 1,6-dibromopyrene was converted
into diester through dilithiation for synthesis of fluorescent bright-
ening polymer.13 In contrast to these methods of preparing sym-
metric pyrenes, there remains a great chemical difficulty in
obtaining unsymmetrically functionalized pyrenes.14
Herein, we report a systematic procedure for the synthesis of
unsymmetrically functionalized pyrene derivatives at the 1 and 6
positions (Scheme 1). First, (6-bromo-3,8-dibutylpyren-1-yl)
trimethylsilane 1 was prepared and is readily soluble in various
organic solvents. Bromide 1 was readily amenable to Suzuki–Miya-
ura, Sonogashira and Buchwald–Hartwig cross-coupling reactions.
⇑
Corresponding author. Tel.: +81 77 543 7461; fax: +81 77 543 7483.
E-mail address: iwasawa@rins.ryukoku.ac.jp (T. Iwasawa).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.09.089

A. H. Sato et al. / Tetrahedron Letters 52 (2011) 6284–6287
6285
Scheme 1. The outline of synthetic route to unsymmetrically substituted pyrene via 1.
Table 1
Evaluation of the reactivity of 1 on cross-coupling reactionsa
Entry
Product
Yield (%)
Timeb (h)
1
2
3
4
5
2
3
4
5
6
7
8
9
10
11
12
13
87
88
78
93
89
91
97
90
95
47
91
70
23
21
18
22
14
23
8
11
16
22
1
6
7c
8
9
10
11d
12e
Scheme 2. Synthesis of 1.
15
a
All reactions were performed in accordance with the representative procedure
organic solvents. Compound 1 proved to be quite soluble in CHCl3,
CH2Cl2, benzene, toluene, THF, EtOAc, CH3CN, CH3CH2CN, acetone
and even hexane.21
in Ref. 22, unless otherwise stated.
b
The reactions were stopped when the complete formation of Pd black was
observed and/or when the starting materials disappeared on TLC monitoring.
c
The scope of reactivity of 1 was examined on cross-coupling
reactions, by preparing a 1-substituted (3,8-dibutylpyren-6-yl)tri-
methylsilane 2–13 (Fig. 1). The results are summarized in Table
1.22 Suzuki–Miyaura reactions (entries 1–10) were conducted with
0.5 mmol (233 mg) of 1 and 2 mL of DMF at 105 °C, in the presence
of 10 mol % Pd(PPh3)4 and 2 equiv K2CO3.23 The reactions in entries
1–6 proved to be initially very clean as confirmed by TLC. For entry
7, reaction of ortho-methoxyphenylboronic acid was sluggish pre-
sumably due to the steric hindrance,24 and the alternative catalyst
The reaction was carried out in toluene at 110 °C with 5 mol % Pd2(dba)3,
15 mol % P(C6H11)3, and K3PO4 (2 equiv). dba = dibenzylideneacetone.
d
Reaction at 70 °C was conducted with
1
(0.25 mmol) and TMS acetylene
catalyst system of
(0.75 mmol) in Et3N (1.5 mL) and toluene (1.5 mL).
A
PdCl2(PPh3)2 (0.0125 mmol) and PPh3 (0.025 mmol), and CuI (0.025 mmol) was
used.
e
Reaction at 90 °C was conducted with 1 (0.25 mmol), pyrrolidine (0.75 mmol)
and NaOtBu (0.75 mmol) in toluene (2.0 mL).
A catalyst system of Pd2(dba)3
(0.0125 mmol), and BINAP (0.025 mmol) was used.
system of Pd2(dba)3 (dba = dibenzylideneacetone) and P(C6H11 3
)
completed the reaction in 8 h with 93% yield. For entries 8–10,
the arylboronic acids containing bromine and nitrogen were exam-
ined, and bromide 9,25 benzamide 10,26 and pyridine 11 were
obtained in 90%, 95% and 47% yield, respectively. Sonogashira
cross-coupling27 was carried out with trimethylsilylacetylene,
and compound 12 was given in 91% yield (entry 11). Buchwald–
Hartwig amination reaction with pyrrolidine10 also proceeded to
yield 13 in 70% (entry 12).
Removal of the trimethylsilyl group with Br2 was performed to
transform 2, 5, and 7 into the bromide 14, 15, and 16 (Scheme 3).
Addition of Br2 (neat) to CCl4 solution of 2 proved not to work as
confirmed by the multi spots in TLC monitoring. After several at-
tempts, Br2 as a 1 M CCl4 was found to convert 2–14 cleanly in
Scheme 3. Desilylation of 2, 5, and 7 with bromine.
Figure 1. Derivatives from 1 through the cross-coupling reactions.

6286
A. H. Sato et al. / Tetrahedron Letters 52 (2011) 6284–6287
Figure 2. Derivatives from 14, 15, and 16 through the cross-coupling reactions.
Acknowledgments
Table 2
Evaluation of the reactivity of 14, 15, and 16 on cross-coupling reactionsa
Timeb (h)
We are very grateful to Professor Michael P. Schramm at Cali-
fornia State University Long Beach for helpful discussion. We thank
Ryukoku University Science and Technology, and the Research
Foundation for Pharmaceutical Sciences, and Iketani Science and
Technology Foundation for financial support.
Entry
Substrate
Product
Yield (%)
1
2
3
16
16
16
16
16
14
14
15
15
15
17
18
19
20
21
22
23
24
25
26
81
86
67
71
80
73
74
85
97
91
21
21
22
21
25
22
15
17
10
15
4c
5d
6
7c
8
Supplementary data
9c
10
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2011.09.089.
a
All reactions were performed in accordance with the representative procedure
in Ref. 29, unless otherwise stated.
References and notes
b
The reactions were stopped when the complete formation of Pd black was
observed and/or when the starting materials disappeared on TLC monitoring.
1. (a) Lackowicz, J. R. In Principles of Flurorescenece Spectroscopy, 2nd ed.; Kluwer
Academic/Plenum: New York, 1999. pp. 595–614; (b) Birks, J. B. In Photophysics
of Aromatic Molecules; Wiley-Interscience: London, 1970.
2. (a) Berlman, I. B. J. Phys. Chem. 1970, 74, 3085; (b) Oyamada, T.; Uchiuzou, H.;
Akiyama, S.; Oku, Y.; Shimoji, N.; Matsushige, K.; Sasabe, H.; Adachi, C. J. Appl.
Phys. 2005, 98, 074506.
c
Reaction at 70 °C was conducted with starting bromide (0.25 mmol) and TMS
acetylene (0.75 mmol) in Et3N (1.5 mL) and toluene (1.5 mL). A catalyst system of
PdCl2(PPh3)2 (0.0125 mmol), and PPh3 (0.025 mmol) and CuI (0.025 mmol) was
used.
d
Reaction at 90 °C was conducted with 16 (0.25 mmol), pyrrolidine (0.75 mmol)
and NaOtBu (0.75 mmol) in toluene (2.0 mL).
A catalyst system of Pd2(dba)3
3. Figueira-Duarte, T. M.; Müllen, K. Chem. Rev. 2011. ASAP doi: cr100428a, and
references cited therein.
(0.0125 mmol), and BINAP (0.025 mmol) was used.
4. (a) Zhao, Z. J.; Li, J. H.; Chen, X. P.; Wang, X. M.; Lu, P.; Yang, Y. J. Org. Chem.
2009, 74, 383; (b) Oh, H. Y.; Lee, C.; Lee, S. Org. Electron. 2009, 10, 163; (c) Liu, F.;
Lai, W. Y.; Tang, C.; Wu, H. B.; Chen, Q. Q.; Peng, B.; Wei, W.; Huang, W.; Cao, Y.
Macromol. Rapid Commun. 2008, 29, 659; (d) Moorthy, J. N.; Natarajan, P.;
Venkatkrishnan, P.; Huang, D. F.; Chow, T. J. Org. Lett. 2007, 9, 5215.
5. (a) Xia, R. D.; Lai, W. Y.; Levermore, P. A.; Huang, W.; Bradley, D. D. C. Adv. Funct.
Mater. 2009, 19, 2844; (b) Gingras, M.; Placide, V.; Raimundo, J. M.; Bergamini,
G.; Ceroni, P.; Balzani, V. Chem. Eur. J. 2008, 14, 10357; (c) Kim, H. M.; Lee, Y. O.;
Lim, S.; Kim, J. S.; Chao, B. R. J. Org. Chem. 2008, 73, 5127; (d) Sienkowska, M. J.;
Farrar, J. M.; Zhang, F.; Kusuma, S.; Heiney, P. A.; Kaszynski, P. J. Mater. Chem.
2007, 17, 1399; (e) Zhang, H. J.; Wang, Y.; Shao, K. Z.; Liu, Y. Q.; Chen, S. Y.; Qiu,
W. F.; Sun, X. B.; Qi, T.; Ma, Y. Q.; Yu, G.; Su, Z. M.; Zhu, D. B. Chem. Commun.
2006, 7, 755; (f) Venkataramana, G.; Sankararaman, S. Org. Lett. 2006, 8, 2739;
(g) Tang, C.; Liu, F.; Xia, Y. J.; Xie, L. H.; Wei, A.; Li, S. B.; Fan, Q. L.; Huang, W.
Org. Electron. 2006, 7, 155; (h) Hayer, A.; Halleux, V. de.; Kohler, A.; El-
Garoughy, A.; Meijer, E. W.; Barbera, J.; Tant, J.; Levin, J.; Lehmann, M.;
Gierschner, J.; Cornil, J.; Geerts, Y. H. J. Phys. Chem. B 2006, 110, 7653; (i)
Malinovskii, V. L.; Häner, R. Eur. J. Org. Chem. 2006, 3550–3553; (j)
Mikroyannidis, J. A. Synth. Met. 2005, 155, 125; (k) Halleux, V. de.; Calbert, J.
P.; Brocorens, P.; Cornil, J.; Declercq, J. P.; Bredas, J. L.; Geerts, Y. Adv. Funct.
Mater. 2004, 14, 649; (l) Faulkner, L. R.; Bard, A. J.; Tachikaw, H. J. Am. Chem. Soc.
1972, 94, 691.
91% yield. Similar clean-deprotection by the addition of a 1 M CCl4
solution of Br2 were observed in 5 and 7, giving 15 in 93% yield and
16 in 87% yield, respectively.28
The reactivity of Br substituent of 14, 15, and 16 were examined
on cross-coupling reactions, by preparing unsymmetrically func-
tionalized pyrenes 17–26 (Fig. 2). The results are summarized in
Table 2. Bromide 14 smoothly cross-coupled with arylboronic acids
containing methyl ester, formyl, and pyridine groups (entries 1–3).
Compound 14 also reacted with trimetylsilylacetylene by Sono-
gashira cross-coupling in 71% yield (entry 4), and reacted with pyr-
rolidine in Buchwald–Hartwig amination in 80% yield (entry 5). For
entries 6–10, bromide 14 and 15 were also effective to Suzuki–
Miyaura and Sonogashira cross-coupling, giving 22–26 in 73–97%
yields. In particular, for entries 6 and 8, both 22 and 24 have
methyl ester group and formyl group specifically at the ortho-
and para-positions, respectively; thus, these systematic transfor-
mations using 1 achieved exact installation of functional groups
into pyrene core structure.
6. Bernhardt, S.; Kastler, M.; Enkelmann, V.; Baumgarten, M.; Müllen, K. Chem.
Eur. J. 2006, 12, 6117.
7. Sonar, P.; Soh, M. S.; Cheng, Y. H.; Henssler, J. T.; Sellinger, A. Org. Lett. 2010, 12,
3292–3295.
In summary, we have developed a systematic procedure for the
synthesis of unsymmetrically substituted pyrene derivatives. The
synthetic approach, which employs (6-bromo-3,8-dibutylpyren-
1-yl)trimethylsilane 1, accomplished to install varied functional
groups into the 1, 6-positions of the pyrene core structure, provid-
ing novel functionalized molecules 2–26. Because of the utility of
unsymmetrically functionalized pyrene derivatives, we anticipate
that this approach is likely to find widespread use in the field of or-
ganic materials science. Furthermore, this strategy should find
applications toward other substitution pyrene patterns. We will
report this work in due course.
8. Sagara, Y.; Mutai, T.; Yoshikawa, I.; Araki, K. J. Am. Chem. Soc. 2007, 129, 1520–
1521.
9. Figueira-Duarte, T. M.; Simon, S. C.; Wagner, M.; Drtezhinin, S. L.; Zachariasse,
K. A.; Mullen, K. Angew. Chem., Int. Ed. 2008, 47, 10175.
10. Suzuki, S.; Takeda, T.; Kuratsu, M.; Kozaki, M.; Sato, K.; Shiomi, D.; Takui, T.;
Okada, K. Org. Lett. 2009, 11, 2816–2818.
11. Venkataramana, G.; Dongare, P.; Dawe, L. N.; Thompon, D. W.; Zhao, Y.;
Bodwell, G. J. Org. Lett. 2011, 13, 2240–2243.
12. Zhao, S. B.; Wucher, P.; Hudoson, Z. M.; McCormick, T. M.; Liu, X.-Y.; Wang, S.;
Feng, X.-D.; Lu, Z.-H. Organometallics 2008, 27, 6446–6456.
13. (a) Connor, D. M.; Collard, D. M.; Liotta, C. L.; Schiradi, D. A. Dyes Pigm. 1999, 43,
203–206; (b) Connor, D. M.; Kriegel, R. M.; Collard, D. M.; Liotta, C. L.; Schiraldi,
D. A. J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 1291–1301.

A. H. Sato et al. / Tetrahedron Letters 52 (2011) 6284–6287
6287
14. (a) Mizushima, T.; Yoshida, A.; Harada, A.; Yoneda, Y.; Minatani, T.; Murata, S.
Org. Biomol. Chem. 2006, 4, 4336–4344; (b) Yoshida, A.; Harada, A.; Mizushima,
T.; Murata, S. Chem. Lett. 2003, 32, 68–69; (c) Zöphel, L.; Beckmann, D.;
Enkelmann, V.; Chercka, D.; Rieger, R.; Müllen, K. Chem. Commun. 2011, 47,
6960–6962.
15. Banerjee, M.; Vyas, V. S.; Lindeman, S. V.; Rathore, R. Chem. Commun. 2008,
1889–1891.
16. The use of CH2Cl2 and CHCl3 in place of CCl4 was applicable to the bromination,
although the chemical yields slightly decreased.
17. (a) Grimshaw, J.; Grimshaw, J. T. J. Chem. Soc., Perkin Trans. 1 1972, 1622; (b)
Vollmann, H.; Becker, M.; Correll, H. S. Justus Liebigs Ann. Chem. 1937, 531, 1.
18. The experiment of dibromination was conducted with 18.2 g of pyrene, and the
recrystallization was performed with freshly distilled toluene.
2 mL of DMF was added. The reaction mixture was stirred at room temperature
for 1 min, and then conducted at 105 °C for 23 h. After the reaction, the mixture
was diluted with 15 mL EtOAc, and filtered through a pad of Celite and florisil.
Purification by silica gel column chromatography gave 2 (227 mg, 87%) as pale
yellow solid materials. 1H NMR(400 MHz, CDCl3) d 8.39 (d, J = 9.4 Hz, 1H), 8.30
(d, J = 9.4 Hz, 1H), 8.23 (d, J = 8.4 Hz, 2H), 8.16 (d, J = 9.4 Hz, 1H), 8.09 (d,
J = 9.4 Hz, 1H), 8.03 (s, 1H), 7.81 (s, 1H), 7.72 (d, J = 8.4 Hz, 2H), 4.01 (s, 3H),
3.37 (t, J = 7.7, 7.7 Hz, 2H), 3.30 (t, J = 7.7, 7.7 Hz, 2H), 1.92–1.78 (m, 4H), 1.59–
1.46 (m, 4H), 1.03–0.98 (m, 6H), 0.61 (s, 9H). 13C NMR (100 MHz, CDCl3) d
167.3, 146.7, 137.1, 136.0, 135.5, 134.5, 134.1, 131.0, 129.9, 129.8, 129.1, 128.8,
128.6, 128.1, 127.1, 126.5, 126.0, 125.2, 123.4, 122.4, 52.4, 34.4, 34.3, 33.9,
33.8, 23.3, 23.2, 14.34, 14.33, 1.0. MS(FAB) m/z: 520 (M+). Anal. Calcd for
C35H40O2Si: C, 80.72; H, 7.74. Found: C, 80.76; H, 7.55.
19. The other 17% impurity was mainly 1,8-dibromopyrene. Although the
byproduct would be converted to 1,8-dibromo-3,6-dibutylpyrene in the
subsequent step, it was removed by the single operation of recrystallization
from freshly distilled toluene.
23. Wegner, H. A.; Reisch, H.; Rauch, K.; Demeter, A.; Zachariasse, K. A.; Meijere, A.;
Scott, L. T. J. Org. Chem. 2006, 71, 9080–9087.
24. Numerous amounts of compound 1 was observed on TLC analyzing even in
48 h reaction times.
20. The synthetic procedure of 1: To a solution of 1,6-dibromo-3,8-dibutylpyrene
(7.6 g, 16 mmol) in anhydrous toluene (600 mL) at room temperature was
added THF (3.2 mL, 38 mmol), and then n-BuLi (11 mL, 1.63 M in hexane) was
added dropwise over 3 min. The solution was stirred for 15 min, and
chlorotrimethylsilane (9.5 mL, 48 mmol) was added over 1 min. After stirring
for 1 h at room temperature, the reaction was quenched with water. The
solvent was thoroughly evaporated, and to the mixture was added CHCl3 and
aqueous phase was extracted with CHCl3. Combined organic phases were
washed with brine, and then dried over Na2SO4, and concentrated to give the
crude products. Purification by silica gel column chromatography (hexane
only) gave a desired compound 1 (5.2 g, 70%) as white solid materials. 1H NMR
(400 MHz, CDCl3) d 8.43 (d, J = 9.5 Hz, 1H), 8.37 (d, J = 9.4 Hz, 1H), 8.30 (d,
J = 9.5 Hz, 1H), 8.21 (d, J = 9.4 Hz, 1H), 8.10 (s, 1H), 8.04 (s, 1H), 3.35–3.27 (m,
4H), 1.85–1.83 (m, 4H), 1.56–1.49 (m, 4H), 1.0 (t, J = 7.4, 7.4 Hz, 6H), 0.60 (s,
9H). 13C NMR (100 MHz, CDCl3) d 138.3, 136.6, 136.1, 134.5, 134.3, 131.2,
129.9, 128.33, 128.25, 128.1, 127.4, 126.4, 125.2, 124.5, 34.6, 34.11, 34.05, 33.5,
23.3, 23.2, 14.42, 14.38, 1.05. MS (FAB) m/z: 466 (M+). Anal. Calcd for
25. The solubility of 9 was very good: 244 mg of 9 dissolved in 0.5 mL hexane.
26. Cross-coupling between
1 and p-(aminocarbonyl)phenylboronic acid was
carried out in toluene at 110 °C with 5 mol % Pd2(dba)3, 15 mol % P(C6H11)3,
and 2 equiv K3PO4, however no reaction was observed.
27. Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 4467–4470.
28. Benzylic bromination of 2, 5, and 7 were not observed.
29. The typical procedure of cross-coupling reactions (Table 2, entry 1): K2CO3
(83 mg, 0.6 mmol) and p-(methoxycarbonyl)phenylboronic acid (81 mg,
0.45 mmol) were dried in vacuo in
a Schelenk tube with heating, then
bromide 16 (149 mg, 0.3 mmol), and Pd(PPh3)4 (69 mg, 0.06 mmol) were
added. The whole system was evacuated and backfilled with argon three times,
and 1.2 mL of DMF was added. The reaction mixture was stirred at room
temperature for 1 min, and then conducted at 105 °C for 21 h. After the
reaction, the mixture was diluted with 15 mL EtOAc, and filtered through a pad
of Celite and florisil. Purification by silica gel column chromatography gave 17
(134 mg, 81%) as pale yellow solid materials. 1H NMR(400 MHz, CDCl3) d 8.24–
8.17 (m, 5H), 8.10 (d, J = 9.5 Hz, 1H), 7.83 (d, J = 8.4 Hz, 2H), 7.73 (d, J = 8.4 Hz,
2H), 7.58 (d, J = 8.7 Hz, 2H), 7.11 (d, J = 8.7 Hz, 2H), 4.01 (s, 3H), 3.94 (s, 3H),
3.33 (t, J = 7.6, 7.6 Hz, 4H), 1.86–1.81 (m, 4H), 1.54–1.48 (m, 4H), 1.00–0.96 (m,
6H). 13C NMR (100 MHz, CDCl3) d 167.4, 159.2, 146.7, 137.4, 136.9, 136.6,
135.9, 134.0, 131.9, 131.0, 129.9, 129.5, 129.1, 129.0, 128.2, 127.5, 127.3,
126.42, 126.39, 125.8, 124.6, 123.2, 122.6, 114.1, 55.6, 52.4, 34.3, 34.2, 33.7,
23.2, 14.3. MS(FAB) m/z: 554 (M+). Anal. Calcd for C39H38O3: C, 84.44; H, 6.90.
Found: C, 84.46; H, 7.01.
C27H33BrSi: C, 69.66; H, 7.14. Found: C, 69.79; H, 7.10.
21. 6.1 g of 1 was recrystallized from 33 mL of hexane, giving a first crop of 4.1 g in
pure form.
22. The typical procedure of cross-coupling reactions (Table 1, entry 1): K2CO3
(138 mg, 1 mmol) and p-(methoxycarbonyl)phenylboronic acid (135 mg,
0.75 mmol) were dried in vacuo in
a Schelenk tube with heating, then
bromide 1 (233 mg, 0.5 mmol), and Pd(PPh3)4 (58 mg, 0.05 mmol) were added.
The whole system was evacuated and backfilled with argon three times, and