Chemoselective Suzuki-Miyaura coupling of bromophenyl-substituted bromoallenes with arylboronic acids

Article abstract of DOI:10.1055/s-0031-1290682

Developing highly chemoselective Suzuki-Miyaura coupling reactions is of great value in the synthetic chemistry. Here we report the results of palladium-catalyzed reaction of bromoallenes containing an aryl bromide moiety with arylboronic acids. It is found that the C-Br insertion exclusively takes place on bromoallene rather than on the benzene ring. Theoretical calculations demonstrate that the corresponding oxidative addition intermediate has a much lower free energy. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0031-1290682

LETTER
▌1505
lCetther emoselective Suzuki–Miyaura Coupling of Bromophenyl-Substituted
Bromoallenes with Arylboronic Acids
Suzuki–Miyaura Coupling of Bromoallenes with Arylboronic Acids
Xin Du,a Xuesong Liu,a Liang Xu,*a Wenfeng Jiang,*a Ming Bao,b Ren Heb
a
School of Chemistry, Dalian University of Technology, Western Campus, No.2 Linggong Road, Dalian 116023, P. R. of China
b
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Western Campus, No.2 Linggong Road, Dalian 116023,
P. R. of China
E-mail: xuliang@dlut.edu.cn; E-mail: jiangwf@dlut.edu.cn
Received: 24.02.2012; Accepted after revision: 05.04.2012
coupling reactions. Several reviews on highly selective
Suzuki–Miyaura coupling have been published.2 Aryl
bromides1,3 and bromoallenes4 have been reported to be
utilized as coupling partners in the palladium-catalyzed
Abstract: Developing highly chemoselective Suzuki–Miyaura
coupling reactions is of great value in the synthetic chemistry. Here
we report the results of palladium-catalyzed reaction of bromoal-
lenes containing an aryl bromide moiety with arylboronic acids. It
is found that the C–Br insertion exclusively takes place on bromoal- coupling reactions. Although many other experimental
studies have been reported,5–14 the relative reactivity be-
tween aryl bromides and bromoallenes, to the best of our
knowledge, is not reported by experimental research. On
the other hand air-stable hemilabile P–O coordinated cy-
lene rather than on the benzene ring. Theoretical calculations dem-
onstrate that the corresponding oxidative addition intermediate has
a much lower free energy.
Key words: coupling, chemoselectivity, palladium, oxidation, ad-
dition
clopalladated complex Pd(Ph2PCH2CO2)2 could be used
as a precatalyst in the Suzuki reaction of both aryl bro-
mides and bromoallenes with arylboronic acids to obtain
As one of the most useful methods for the construction of
new C–C bonds, the Suzuki reaction of organoboron re-
agents with organic halides has been extensively applied
in the synthetic community.1 When the starting molecule
has more than one halogen-substituent, selectivity is a
critical issue for the cross-coupling reactions because the
remaining halo group in the product of the cross-coupling
reaction can be further converted into another group
through a subsequent synthetic procedure. Chemoselec-
tive cross-coupling has thus become an attractive ap-
proach in the synthetic chemistry, and consequently, it is
of great value to develop such site-selective cross-
diaryl compounds with satisfactory and even excellent
yields.4d,15
Here, we report the results of the chemoselective Suzkui–
Miyaura coupling reaction of bromoallenes containing an
aryl bromide moiety with arylboronic acids using
Pd(Ph2PCH2CO2)2.
The reaction of 1-bromo-4-(3-bromohepta-1,2-dienyl)-
benzene (1a) with phenylboronic acid was first examined,
and two coupling products seem possible. However, it is
surprised to find that only 1-bromo-4-(3-phenylhepta-1,2-
dienyl)-benzene (3a) can be detected (Scheme 1).
n-Bu
Br
Br
3a
n-Bu
Pd(Ph2PCH2COO)2 (3 mol%)
+ (HO)2B
K3PO4⋅3H2O (3 mmol)
THF–H2O, r.t., 16 h
Br
Br
1a
(1 mmol)
2a
(1.5 mmol)
n-Bu
3a'
Scheme 1 The coupling reaction of brominated bromoallenes with arylboronic acids
SYNLETT 2012, 23, 1505–1510
Advanced online publication: 29.05.2012
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0031-1290682; Art ID: ST-2012-W0167-L
© Georg Thieme Verlag Stuttgart · New York

1506
X. Du et al.
LETTER
Screening of the catalysts confirms that C–Br on bromoal- group of 1a was changed to the n-pentyl group, the cross-
lene rather than on benzene ring readily takes part in the coupling reactions also proceed smoothly, giving the de-
Suzuki cross-coupling reaction between 1-bromo-1-bu- sired products 3d,e,f with good yields (86%, 87%, and
tyl-(4-bromophenyl)-1,2-propadiene (1a) and aryl boric 82%, respectively). It was found that ortho-bromo-substi-
acid (2a), catalyzed by Pd(PPh3)4, Pd(OAc)2/Ph3P, tuted substrate 1c displays comparable reactivity relative
PdCl2/Ph3P, and Pd(Ph2PCH2CO2)2 (Table 1, entries 4–7). to the para-bromo-substituted substrate 1a (Table 2, en-
In contrast, PdCl2, Pd(OAC)2, and Pd2(dba)3 show very tries 7–9). But the mixture of diaryl-substituted allenes
low chemoselectivity, yielding unidentified mixtures (Ta- and diaryl-substituted propynes was found in the case of
ble 1, entries 1–3).
meta-bromo-substituted substrates (Table 2, entries 10
and 11). It was assumed that isomerization occurs be-
tween allenes and propaygyl bromines.
Table 1 The Suzuki Cross-Coupling Reaction of 1a with Phenyl-
boronic Acid Catalyzed by Different Pd Complexesa
Theoretical computations were further employed to ex-
plain such chemoselectivity. It is generally recognized
that the oxidative addition step is the selectivity-determin-
ing step. The free energy difference (14.94 kcal/mol) be-
tween the two possible intermediates clearly demonstrates
that palladium favors C–Br insertion on the allene moiety
by stabilizing the C–Br insertion transition state more
strongly (Figure 1).
Br
n-Bu
catalyst
(HO) B
+
2
K3PO4
toluene
n-Bu
2a
Br
1a
Br
3a
Entry
Catalyst
PdCl2
Product
Yield (%)b
1
2
3
4
5
6
7
n.a.
n.a.
n.a.
3a
n.a.e
n.a.
n.a.
82
Pd(OAc)2
Pd2(dba)3
Pd(PPh3)4
Pd(OAC)2/Ph3Pc
PdCl2/Ph3Pc
3a
80
3a
63
d
Pd(Ph2PCH2COO)2
3a
87
a Reaction conditions: 1a (0.50 mmol), 2a (0.75 mmol), K3PO4 (3.00
mmol), catalyst (10 mmol%), toluene (3.0 mL), 60 °C, 16 h.
b Isolated yields.
c Reaction conditions: 1a (0.50 mmol), 2a (0.75 mmol), K3PO4 (3.00
mmol), Pd (10 mmol%), Ph3P (20 mmol%), toluene (3.0 mL), 60
°C.16 h.
Figure 1 Free energy profile of structures along two possible reac-
tion paths (path a and path b). Energies are given in kcal/mol. Calcu-
lations were performed by employing B3LYP/6-31+G(d), LANL2DZ
(Pd)
d Reaction conditions: 1a (0.50 mmol), 2a (0.75 mmol), K3PO4·3H2O
(3.00 mmol), Pd(Ph2PCH2COO)2 (5 mmol%), THF–H2O (1:1, 3.0
mL), r.t., 8 h.
e n.a. = unidentified mixture or not available.
In summary, the Suzuki–Miyaura coupling of bromophe-
nyl-substituted bromoallenes with arylboronic acids was
studied, and the reaction was observed exclusively to take
place at the bromoallenes moiety. One of the possible ex-
planations for such chemoselectivity might be due to the
energetically favorable oxidative addition species.
No significant difference of yield was observed when us-
ing different arylboronic acids in the cross-coupling reac-
tion (Table 2). The reaction of 1a with 2b and 2c gives the
corresponding coupling products 3b and 3c with satisfac-
tory yields and high chemoselectivities of 85% and 83%,
respectively (Table 2, entries 2 and 3). When the n-butyl
Synlett 2012, 23, 1505–1510
© Georg Thieme Verlag Stuttgart · New York

LETTER
Suzuki–Miyaura Coupling of Bromoallenes with Arylboronic Acids
1507
a
Table 2 The Cross-Coupling Reaction of Compound 1 with Various Arylboronic Acids 2 Catalyzed by Pd(Ph2PCH2COO)2
R2
Br
Pd(Ph2PCH2COO)2 (3 mol%)
+
(HO)2B
R2
R1
K3PO4⋅3H2O (3 equiv)
THF–H2O, r.t., 8 h
Ar
1
2
Ar
R1
3
Entry
Bromoallenes
Aryboronic acids
Product
Yield (%)b
Br
nBu
(HO)2B
n-Bu
1
87
2a
Br
Br
1a
3a
(HO)2B
2
1a
85
n-Bu
2b
Br
3b
F
(HO)2B
F
3
1a
83
n-Bu
2c
Br
3c
Br
n-Pent
n-Pent
4
2a
86
Br
Br
1b
3d
5
1b
2b
87
n-Pent
Br
3e
© Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 1505–1510

1508
X. Du et al.
LETTER
Table 2 The Cross-Coupling Reaction of Compound 1 with Various Arylboronic Acids 2 Catalyzed by Pd(Ph2PCH2COO)2a (continued)
R2
Br
Pd(Ph2PCH2COO)2 (3 mol%)
+
(HO)2B
R2
R1
K3PO4⋅3H2O (3 equiv)
THF–H2O, r.t., 8 h
Ar
1
2
Ar
R1
3
Entry
Bromoallenes
Aryboronic acids
Product
Yield (%)b
F
6
1b
2c
82
n-Pent
Br
3f
Br
n-Bu
7
2a
84
n-Bu
Br
Br
1c
3g
8
1c
2b
85
n-Bu
Br
3h
F
9
1c
2c
80
n-Bu
Br
3i
Br
n-Bu
+
n-Bu
10
2a
Br
Br
n-Bu
Br
1d
3j
Synlett 2012, 23, 1505–1510
© Georg Thieme Verlag Stuttgart · New York

LETTER
Suzuki–Miyaura Coupling of Bromoallenes with Arylboronic Acids
1509
Table 2 The Cross-Coupling Reaction of Compound 1 with Various Arylboronic Acids 2 Catalyzed by Pd(Ph2PCH2COO)2a (continued)
R2
Br
Pd(Ph2PCH2COO)2 (3 mol%)
+
(HO)2B
R2
R1
K3PO4⋅3H2O (3 equiv)
THF–H2O, r.t., 8 h
Ar
1
2
Ar
R1
3
Entry
Bromoallenes
Aryboronic acids
Product
Yield (%)b
Br
n-Bu
n-Bu
+
n-Bu
Br
11
2a
Br
Br
Br
Br
Br
1e
3k
a Reaction conditions: 1 (0.50 mmol), 2 (0.75 mmol), K3PO4·3H2O (3.00 mmol), Pd(Ph2PCH2COO)2 (3 mmol%), THF–H2O (1:1, 3.0 mL), r.t.,
8 h.
b Isolated yields.
(10) Akravi, O. A.; Hussain, M.; Langer, P. Tetrahedron Lett.
References
2011, 52, 1093.
(1) For recent reviews on Suzuki–Miyaura cross-coupling
(11) Mohamed, Y. M. A.; Hansen, T. V. Tetrahedron Lett. 2011,
reaction, see: (a) Suzuki, A. Angew. Chem. Int. Ed. 2011, 50,
6722. (b) Polshettwar, V.; Decottignies, A.; Len, C.; Fihri,
A. ChemSusChem 2010, 3, 502. (c) Doucet, H. Eur. J. Org.
52, 1057.
(12) Zhang, H.; Zhou, C.-B.; Chen, Q.-Y.; Xiao, J.-C.; Hong, R.
Org. Lett. 2011, 13, 560.
Chem. 2008, 2013. (d) Alonso, F.; Beletskaya, I. P.; Yus, M.
(13) Endo, K.; Ohkubo, T. Org. Lett. 2011, 13, 3368.
Tetrahedron 2008, 64, 3047. (e) Molander, G. A.; Ellis, N.
(14) Littke, A. F.; Dai, C. Y.; Fu, G. C. J. Am. Chem. Soc. 2000,
Acc. Chem. Res. 2007, 40, 275. (f) Suzuki, A. Chem.
122, 4020.
Commun. 2005, 38, 4759. (g) Suzuki, A. Proc. Japan Acad.,
(15) (a) Guo, M.-P.; Jian, F.-F.; He, R. J. Fluorine Chem. 2006,
Ser. B 2004, 80, 359. (h) Kotha, S.; Lahiri, K.; Kashinath, D.
Tetrahedron 2002, 58, 9633.
(2) For recent reviews on highly selective Suzuki cross-
127, 177. (b) Guo, M.-P.; Jian, F.-F.; He, R. Tetrahedron
Lett. 2006, 47, 2033. (c) Guo, M.-P.; Jian, F.-F.; He, R.
Tetrahedron Lett. 2005, 46, 9017.
coupling reaction, see: (a) Rossi, R.; Bellina, F.; Lessi, M.
Tetrahedron 2011, 67, 6969. (b) Schroter, S.; Stock, C.;
Bach, T. Tetrahedron 2005, 61, 2245. (c) Wang, J.-R.;
Manabe, K. Synthesis 2009, 1405.
(16) General Procedure for the Suzuki Reaction
A mixture of bromoallene (1.0 mmol), arylboronic acid
(1.5 mmol), K3PO4·3H2O (798.9 mg, 3.0 mmol) and
Pd(Ph2PCH2CO2)2 (17.8 mg, 3 mol%) in of THF–H2O (v/v
(3) For selected recent references, see: (a) Ullah, E.; McNulty,
= 1:1, 3 mL) was stirred at r.t. under nitrogen atmosphere for
J.; Robertson, A. Tetrahedron Lett. 2009, 50, 5599.
6 h. The product was extracted with Et2O (5 × 5 mL), and the
(b) Sawai, K.; Tatumi, R.; Nakahodo, T.; Fujihara, H.
combined organic layer was dried over MgSO4. Then the
Angew. Chem. Int. Ed. 2008, 47, 6917. (c) Fleckenstein,
C. A.; Plenio, H. Green Chem. 2007, 9, 1287.
(d) Wawrzyniak, P.; Heinicke, J. Tetrahedron Lett. 2006,
47, 8921.
solvent was removed under reduced pressure, and the crude
product was purified by silica gel column chromatography
(eluent: hexane) to afford desired pure product.
1H NMR and 13C NMR spectra were recorded in CDCl3
solution on a Varian Inova-400 spectrometer (1H: 400 MHz;
13C: 100 MHz). The chemical shifts are reported in ppm
downfield from TMS. IR spectra were recorded on a
NEXUS FTIR spectrometer. HRMS spectra were recorded
on a Q-TOF mass spectrometry (Micromass, England)
equipped with Z-spray ionization source. TLC was carried
out on SiO2 (silica gel 60 F254, Merck). Flash chroma-
tography was carried out on SiO2 (silica gel 60, 200–300
mesh). 1-Bromo-4-(3-bromohepta-1,2-dienyl)-benzene (1a)
was synthesized following the procedure described in ref.
17.
(4) (a) Saalfrank, R. W.; Haubner, M.; Deutscher, C.; Bauer,
W.; Clark, T. J. Org. Chem. 1999, 64, 6166. (b) Liu, P. H.;
Li, L.; Webb, J. A.; Zhang, Y.; Goroff, N. S. Org. Lett. 2004,
6, 2081. (c) Gillmann, T.; Weeber, T. Synlett 1994, 649.
(d) Du, X.; Feng, X. J.; Liu, Y.; He, R.; Bao, M. Chin. Chem.
Lett. 2010, 21, 641.
(5) Salman, G. A.; Mahal, A.; Shkoor, M.; Hussain, M.;
Villinger, A.; Langer, P. Tetrahedron Lett. 2011, 52, 392.
(6) Salman, G.; Hussain, M.; Villinger, A.; Langer, P. Synlett
2010, 3031.
(7) Niphakis, M. J.; Georg, G. I. Org. Lett. 2011, 13, 196.
(8) Lima, C. F. R. A. C.; Rodriguez-Borges, J. E.; Santos, L. M.
N. B. F. Tetrahedron 2011, 67, 689.
(9) Jepsen, T. H.; Larsen, M.; Jørgensen, M.; Solanko, K. A.;
Bond, A. D.; Kadziola, A.; Nielsen, M. B. Eur. J. Org.
Chem. 2011, 53.
Free energy calculations were carried out using the
Gaussian09 program (Frisch, M. J. et al. Gaussian 09,
revision A.01). The geometry of each structure was first
optimized by density functional theory B3LYP method. The
basis set of 6-31+G (d) was used for C, N, and Br atoms,
while Pd was described by LANL2DZ basis set and an
© Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 1505–1510

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X. Du et al.
LETTER
128.2, 128.2, 126.0, 126.0, 120.5, 110.3, 96.9, 31.7,30.1,
27.6, 22.5, 21.1, 14.1. IR (neat): ν = 2957, 2923, 2850, 1927,
1524, 1476, 1073, 998, 844, 811 cm–1. HRMS (EI): m/z calcd
for C21H23Br: 354.0975 [M]+; found: 354.0983.
effective core potential (ECP) employed. Frequency
calculations were then performed on each optimized
structure, and no imaginary frequency was found, indicating
that the stationary point of each structure was minima in the
energy surface.
1-Bromo-4-[3-(4-fluorophenyl)octa-1,2-dienyl]benzene
(3f)
Spectral Data for New Compounds
1-Bromo-4-(3-phenylhepta-1,2-dienyl)benzene (3a)
Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.18–7.60
(m, 9 H, ArH), 6.46 (s, 1 H, H–=·=), 2.27–2.57 (m, 2 H,
CH2), 1.47–1.59 (m, 2 H, CH2), 1.39–1.45 (m, 2 H, CH2),
0.91 (t, J = 7.2 Hz, 3 H, CH3). 13C NMR (100 MHz, CDCl3):
δ = 206.8, 136.0, 133.9, 132.0, 132.0, 128.7, 128.7, 128.4,
128.4, 127.4, 126.3, 126.3, 120.7, 110.7, 97.2, 30.2, 30.0,
22.8, 14.1. IR (neat): ν = 3059, 2956, 2927, 2858, 1933,
1596, 1486, 1070, 1009, 844, 692 cm–1. HRMS (EI): m/z
calcd for C19H19Br: 326.0670 [M]+; found: 326.0669.
1-Bromo-4-(3-p-tolylhepta-1,2-dienyl)benzene (3b)
Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.41 (d, J =
8.4 Hz, 2 H, ArH), 7.31(d, J = 8.0 Hz, 2 H, ArH), 7.19(d,
J = 8.4 Hz, 2 H, ArH), 7.13 (d, J = 8.0 Hz, 2 H, ArH), 6.44
(s, 1 H, H–=·=), 2.51–2.56 (m, 2 H, CH2), 2.33 (s, 3 H, CH3),
1.53–1.59 (m, 2 H, CH2), 1.39–1.44 (m, 2 H, CH2), 0.91 (t,
J = 7.6 Hz, 3 H, CH3). 13C NMR (100 MHz, CDCl3): δ =
206.5, 137.0, 134.0, 132.8, 131.8, 131.8, 129.3, 129.3,
128.2, 128.2, 126.0, 126.0, 120.5, 110.3, 96.9, 30.1, 29.9,
22.6, 21.1, 13.9. IR (neat): ν = 2956, 2923, 2857, 1927, 1647,
1487, 1070, 1010, 846 cm–1. HRMS (EI): m/z calcd for
C20H21Br: 340.0827 [M]+; found: 340.0823.
Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.36–7.47
(m, 4 H, ArH), 6.98–7.20 (m, 4 H, ArH), 6.46 (t, J = 3.2 Hz,
1 H, H–=·=), 2.49–2.54 (m, 2 H, CH2), 1.53–1.60 (m, 2 H,
CH2), 1.28–1.39 (m, 4 H, CH2CH2), 0.86 (t, J = 7.1 Hz, 3 H,
CH3). 13C NMR (100 MHz, CDCl3): δ = 206.4, 162.2 (d, J =
245.0 Hz), 131.8, 131.8, 131.7, 131.7, 128.6, 128.6, 127.7
(d, J = 8.0 Hz), 127.7 (d, J = 8.0 Hz), 120.7, 115.3 (d, J =
21.0 Hz), 115.3 (d, J = 21.0 Hz), 109.7, 97.2, 31.7, 30.2,
27.5, 22.5, 14.1. IR (neat): ν = 2957, 2923, 2856, 1927, 1597,
1509, 1228, 1012, 830 cm–1. HRMS (EI): m/z calcd for
C20H20BrF: 358.0732 [M]+; found: 357.0659 [M – H]+.
1-Bromo-2-(3-phenylhepta-1,2-dienyl)-benzene (3g)
1H NMR (400 MHz, CDCl3): δ = 7.31–7.46 (m, 6 H, ArH),
7.19–7.23 (m, 2 H, ArH), 7.03–7.07 (m, 1 H, ArH), 6.98 (t,
J = 2.8 Hz, 1 H, H–=·=), 2.54–2.59 (m, 2 H, CH2), 1.54–1.62
(m, 2 H, CH2),1.41–1.46 (m, 2 H, CH2), 0.92 (t, J = 8.0 Hz,
3 H, CH3). 13C NMR (100 MHz, CDCl3): δ = 207.6, 135.8,
134.1, 133.2, 128.6, 128.6, 128.3, 128.3, 127.5, 127.2,
126.2, 126.2, 122.6, 110.3, 96.7, 30.1, 29.8, 22.7, 14.0. IR
(neat): ν = 3059, 2953, 2914, 2860, 1936, 1509, 1476, 1432,
1004, 821, 745, 685 cm–1. HRMS (EI): m/z calcd for
C19H19Br: 326.0667 [M]+; found: 326.0670.
1-Bromo-4-[3-(4-fluorophenyl)hepta-1,2-dienyl]benzene
(3c)
1-Bromo-2-(3-p-tolylhepta-1,2-dienyl)benzene (3h)
1H NMR (400 MHz, CDCl3): δ = 7.32–7.55 (m, 4 H, ArH),
7.13–7.22 (m, 3 H, ArH), 7.02–7.06 (m, 1 H, ArH), 6.95 (t,
J = 2.8 Hz, 1 H, H–=·=), 2.52–2.56 (m, 2 H, CH2), 2.33 (s, 3
H, CH3), 1.54–1.60 (m, 2 H, CH2), 1.38–1.45 (m, 2 H, CH2),
0.92 (t, J = 7.6 Hz, 3 H, CH3). 13C NMR (100 MHz, CDCl3):
δ = 207.6, 137.1, 134.3, 133.3, 132.8, 129.4, 128.4, 128.4,
128.3, 127.6, 126.2, 126.2, 122.7, 110.3, 96.9, 30.2, 29.9,
22.8, 21.3, 14.1. IR (neat): ν = 3020, 2966, 2925, 2849, 1933,
1516, 1468, 1010, 813, 737, 662 cm–1. HRMS (EI): m/z calcd
for C20H21Br: 340.0829 [M]+; found: 340.0827.
Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.36–7.41
(m, 4 H, ArH), 7.17–7.19 (m, 2 H, ArH), 6.98–7.03 (m, 2 H,
ArH), 6.46 (br s, 1 H, H–=·=), 2.51–2.54 (m, 2 H, CH2),
1.55–1.56 (m, 2 H, CH2), 1.41–1.43 (m, 2 H, CH2), 0.91 (t,
J = 7.2 Hz, 3 H, CH3). 13C NMR (100 MHz, CDCl3): δ =
206.4, 162.1 (d, J = 246.0 Hz), 133.6, 133.6, 131.8, 131.8,
128.2, 128.2, 127.6 (d, J = 8.0 Hz), 127.6 (d, J = 8.0 Hz),
115.4 (d, J = 22.0 Hz), 115.4 (d, J = 22.0 Hz), 109.7, 97.2,
30.2, 30.2, 22.6, 14.0. IR (neat): ν = 2955, 2927, 2858, 1932,
1600, 1507, 1486, 1230, 1158, 1070, 1009, 845, 835 cm–1.
HRMS (EI): m/z calcd for C19H18FBr: 344.0576 [M]+;
found: 344.0564.
1-Bromo-2-[3-(4-fluorophenyl)hepta-1,2-dienyl]benzene
(3i)
1H NMR (400 MHz, CDCl3): δ = 7.55 (m, 1 H, ArH), 7.38–
7.44 (m, 3 H, ArH), 7.19–7.24 (m, 1 H, ArH), 6.99–7.07 (m,
3 H, ArH), 6.97 (t, J = 3.0 Hz, 1 H, H–=·=), 2.51–2.56 (m, 2
H, CH2), 1.53–1.64 (m, 2 H, CH2), 1.38–1.47 (m, 2 H, CH2),
0.92 (t, J = 7.2 Hz, 3 H, CH3). 13C NMR (400 MHz, CDCl3):
δ = 207.4, 162.2 (d, J = 245 Hz), 134.1, 133.4, 131.9, 128.5,
128.4, 127.8 (d, J = 8 Hz), 127.8 (d, J = 8 Hz), 127.7, 122.7,
115.6 (d, J = 10 Hz), 115.6 (d, J = 10 Hz), 109.6, 97.2, 30.2,
27.1, 22.8, 14.1. IR (neat): ν = 3055, 2959, 2918, 2856, 1926,
1605, 1509, 1462, 1168, 1017, 840, 737, 593 cm–1. HRMS
(EI): m/z calcd for C19H18FBr: 344.0570 [M]+; found:
344.0576.
1-Bromo-4-(3-phenylocta-1,2-dienyl)-benzene (3d)
1H NMR (400 MHz, CDCl3): δ = 7.41–7.43 (m, 4 H, ArH),
7.30–7.34 (m, 2 H, ArH), 7.19–7.24 (m, 3 H, ArH), 6.50 (s,
1 H, H–=·=), 2.50–2.51 (m, 2 H, CH2), 1.50–1.52 (m, 2 H,
CH2), 1.25–1.42 (m, 4 H, CH2CH2), 0.86 (t, J = 7.6 Hz, 3 H,
CH3). 13C NMR (400 MHz, CDCl3): δ = 206.7, 135.9, 133.8,
131.8, 131.8, 128.6, 128.6, 128.3, 128.3, 127.2, 126.1,
126.1, 120.6, 110.5, 97.1, 31.8, 30.1, 27.6, 22.5, 14.1. IR
(neat): ν = 2950, 2926, 2861, 1925, 1481, 1070, 1014, 8525,
6912 cm–1. HRMS (EI): m/z calcd for C20H21Br: 340.0815
[M]+; found: 340.0827.
1-Bromo-4-(3-p-tolylocta-1,2-dienyl)benzene (3e)
Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.41 (d, J =
6.6 Hz, 2 H, ArH), 7.31 (d, J = 8.0 Hz, 2 H, ArH), 7.19 (d,
J = 6.6 Hz, 2 H, ArH), 7.13 (d, J = 8.0 Hz, 2 H, ArH), 6.45
(s, 1 H, H–=·=), 2.50–2.56 (m, 2 H, CH2), 2.33 (s, 3 H, CH3),
1.53–1.60 (m, 2 H, CH2), 1.28–1.39 (m, 4 H, CH2CH2), 0.86
(t, J = 7.1 Hz, 3 H, CH3). 13C NMR (100 MHz, CDCl3): δ =
206.5, 137.0, 134.0, 132.8, 131.7, 131.7, 129.3, 129.3,
Compounds 3j,k
The products are difficult to purify, and the 1HNMR data are
very complicated, only the typical signal of =·=–H (δ = 6.90,
s, 1 H) and ≡–CArHn-Bu (δ = 6.10, s ,1 H) could be
assigned.
(17) Du, X.; Dai, Y.; He, R.; Lu, S.; Bao, M. Synth. Commun.
2009, 39, 3940.
Synlett 2012, 23, 1505–1510
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