An efficient nickel-catalyzed alkenylation of functionalized benzylic halides with alkenylaluminum reagents

Article abstract of DOI:10.1039/c2ob25303h

Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum reagents catalyzed by NiCl₂(PPh ₃)₂ are reported. The coupling reactions proceed effectively at room temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol% of the catalyst and a longer reaction time of 2 h.

Full text of DOI:10.1039/c2ob25303h

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PAPER
An efficient nickel-catalyzed alkenylation of functionalized benzylic halides
with alkenylaluminum reagents†
Deepak B. Biradar and Han-Mou Gau*
Received 11th February 2012, Accepted 3rd April 2012
DOI: 10.1039/c2ob25303h
Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum
reagents catalyzed by NiCl2(PPh3)2 are reported. The coupling reactions proceed effectively at room
temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-
donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent
yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol%
of the catalyst and a longer reaction time of 2 h.
alkenyl halide. Although, there are a few reports about these
kind of transformations, the reactions are catalyzed by expensive
Introduction
The development of efficient methods that allow the incorpor-
ation of double bonds with high regio- and stereoselectivity are
of enormous importance. Transition metal-catalyzed cross-coup-
ling reactions of organometallic compounds containing an
alkenyl nucleophile with an organic electrophile are one of the
most powerful methods for this purpose.1 Due to their extraordi-
nary diversity, many research groups have attracted much atten-
tion in identifying milder procedures and broader structural
generalities for this transformation. A variety of organometallic
reagents of Zn, Zr,2 Mg,3 B,4 Sn,5 Cu,6 In,7 as well as Li,8 Si,9
and Mn10 have been used in palladium or nickel cross-coupling
reactions, and the synthetic scope of this kind of reaction has
been continuously expanded by the use of new organic electro-
philes, catalysts, or organometallic reagents.
In the last few decades, the synthesis of alkenes by attaching a
C–C single bond onto CvC moieties via cross-coupling have
gained considerable importance due to their wide applicability
and high selectivity in the preparation of biologically active com-
pounds.11 In the mid-1970s, Negishi’s group discovered the first
example of the Pd- or Ni-catalyzed reaction of alkenylalanes
with aryl halides.12 Since then, many groups reported cross-
coupling protocols of Pd-catalyzed alkenylation involving orga-
nometals especially about alkenyl–alkenyl, alkenyl–aryl and
alkenyl–alkyl couplings.13 There are few reports of benzylic
moieties involved in such kind of cross coupling reactions.14
Benzyl cross coupling products can be achieved via coupling of
either alkenyl metal and benzylic halide or benzylic metal and
Pd metal either by using zinc reagent or using an additive to
achieve higher reactivity or selectivity.15 Also, some of the reac-
tions need high temperatures or prolonged reaction time to com-
plete. Moreover, the substrate scope is limited. Therefore, an
efficient and practical synthetic method of alkenyl–benzylic
cross coupling is of considerable importance.
Organoalanes are less studied in cross-coupling reactions
although they have high reactivity and greater Lewis acidity of
aluminum center. Recently, several groups16 including us17 have
developed organoalane reagents and successfully used them in
catalytic reactions. Furthermore, the organoalanes have been
proven to be highly efficient coupling reagents with benzylic or
aryl halides catalyzed by NiCl2(PPh3)2 or Pd(OAc)2 system.18
To continue our efforts in developing the organoalane com-
pounds and to extend their application in cross-coupling reac-
tions, herein, we report the efficient, simple and inexpensive Ni
catalyzed cross-coupling reactions of organic electrophiles with
alkenylalanes in good to excellent yields.
Results and discussion
The coupling reaction between benzyl bromide and the alkenyl-
aluminum reagent prepared via hydroalumination19 of 1-hexyne
was chosen as the model system (Scheme 1), and results are
summarized in Table 1. To find a good catalytic system,
Department of Chemistry, National Chung Hsing University, Taichung,
402, Taiwan. E-mail: hmgau@dragon.nchu.edu.tw; Fax: (+)886-4-
22862547; Tel: (+)886-4-22878615
†Electronic supplementary information (ESI) available: 1H and 13C
NMR spectra of coupling products. See DOI: 10.1039/c2ob25303h
Scheme 1
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Table 1 Optimization of coupling reactions of benzyl bromide with
Table 2 Coupling
of
substituted
benzyl
bromides
and
alkenylaluminum reagenta
alkenylaluminum reagenta
Ni source
Entry (mol%)
PPh3
(mol%)
Time
Solvent (min)
Yieldb
(%)
Entry Substrate
1
R′
Product Yieldb (%)
(1a) n-C4H9
2a
92
85
1
2
3
4
5
6
7
8
—
NiCl2 (1)
NiCl2 (1)
—
—
1
1
1
DME
DME
DME
DME
DME
DME
DME
60
60
60
60
60
60
60
NR
NR
87
92
88
85
92
81
66
76
62
98
98
98
2
(1b) n-C4H9
2b
Ni(acac)2 (1)
Ni(OAc)2 (1)
Ni(ClO4)2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2 (1)
Ni(PPh3)2Cl2
(0.5)
1
3
4
5
(1c)
n-C4H9
2c
2d
2e
91
92
93
—
—
—
—
—
—
—
—
Toluene 60
CH2Cl2 60
Hexane 60
9
(1d) n-C4H9
10
11
12
13
14
THF
Et2O
Et2O
Et2O
60
60
30
30
(1e)
(1f)
n-C4H9
n-C4H9
6
7
8
9
2f
91
90
91
70
15
Ni(PPh3)2Cl2
(0.25)
—
Et2O
30
45
(1g) n-C4H9
(1h) n-C4H9
2g
2h
2i
a Benzyl bromide/Al reagent = 1/1.5 mmol; solvent = 3 mL. b Yields are
based on 1H NMR spectra.
(1i)
(1j)
n-C4H9
n-C4H9
10
11
2j
92
91
(1k) n-C4H9
2k
Scheme 2
12
13
(1l)
n-C4H9
2l
94
85
(1m) n-C4H9
2m
preliminary experiments were performed in DME, and several
Ni salts were surveyed. In the absence of both Ni/phosphine or
phosphine, the reaction did not take place at all over 1 h
(Table 1, entries 1 and 2). While employing 1 mol% each phos-
phine and different Ni salts such as NiCl2, Ni(acac)2, Ni(OAc)2,
and Ni(ClO4)2, the coupling product was furnished in ≥85%
yields with ≥15% homocoupling product of dibenzyl (entries
2–6). However, the reaction in the presence of 1 mol%
NiCl2(PPh3)2 yielded 92% of coupling product with 8% homo-
coupling product in 1 h (entry 7). As it is known that solvent
plays an important role in organoalane mediated reactions, which
were then screened. Non-coordinating solvents like toluene,
CH2Cl2, and hexane provide the coupling product in 88%, 66%,
and 76% yields, respectively. Whereas the strong coordinating
solvent THF made the reaction slow and lowered the yield to
62% in 1 h. The weaker coordinating diethyl ether turned out to
be the best solvent for the reaction, which gave more than 98%
of the desired product with less than 2% of dibenzyl as a by-
product in 1 h (entry 12) as well as in 30 min (entry 13). When
the amount of NiCl2(PPh3)2 was reduced to 0.5 mol%, the reac-
tion afforded 2a in 98% yield (entry 14). A further decrease in
catalyst loading furnished the coupling product in lower yield
(entry 15).
14c
(1n) n-C4H9
(1o) PhCH2
2n
2o
90
15c
16c
17c
82
88
87
(1p) Cyclohexyl 2p
(1q) 3-Thienyl 2q
a Benzyl bromide/Al reagent = 1/1.5 mmol; Et2O = 3 mL. b Isolated
yields of products. c 2 mol% NiCl2(PPh3)2 was used.
The catalytic system works effectively with low catalyst
loading of NiCl2(PPh3)2 to afford the products in good yield.
The results are summarized in Table 2. For substituted benzyl
bromides containing an electron-donating substituent on the aro-
matic ring (entries 1–11), low catalyst loadings of 0.5 mol%
were effective enough to produce coupling products in excellent
yields of ≥90% in 30 min except for 2-methylbenzyl bromide
and 2-phenylbenzyl bromide, which afforded the product in 85%
To evaluate the scope and limitations of the reaction, a variety
of functionalized benzylic bromides and alkenylaluminium
reagents were subjected to coupling reactions (Scheme 2).
4244 | Org. Biomol. Chem., 2012, 10, 4243–4248
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Table 3 Coupling
of
substituted
benzyl
bromides
and
for benzyl bromide in the 92% yield (Table 2, entry 1). Similarly,
5 mol% of the catalysts were used for 3-methyl, 3-methoxy, 4-
methoxy, and 3,5-dimethoxy-substituted benzyl chlorides
(Table 3, entries 2–5) relative to 0.5 mol% of the catalyst for the
corresponding substituted benzyl bromides (Table 2, entries
3–5,11). For 4-fluorobenzyl chloride with an electron-withdraw-
ing fluoro substituent, 5 mol% of the catalyst was used to afford
coupling product 2r in a 91% yield (Table 3, entry 6). We also
examined 4-(vinyl)benzyl chloride (1s′), which also afforded the
coupling product in 93% yield with the same amount of catalyst
loading in 2 h (Table 3, entry 7).
alkenylaluminum reagenta
Entry
1
Substrate
Product
Yieldb (%)
93
(1a′)
(1c′)
(1e′)
2a
2c
2e
2
3
92
93
4
5
(1f′)
2f
92
93
(1k′)
2k
Conclusions
In summary, an extremely efficient, simple and inexpensive
benzyl–alkenyl coupling reaction of benzylic bromides or chlor-
ides with organoalanes is reported. In this study, a wide variety
of benzyl bromides and chlorides are examined, and the coup-
ling reactions of benzylic bromides containing either strong elec-
tron-withdrawing or electron-donating substituents on the
aromatic ring proceed effectively at room temperature in short
reaction times of 30 min while using a low catalyst loading of
0.5 mol% of NiCl2(PPh3)2, achieving coupling products in
excellent yields. In contrast, the coupling reaction of benzyl
chlorides requires a higher catalyst loading of 5 mol% and a
longer reaction time of 2 h to give corresponding products in
similar yields.
6
7
(1r′)
(1s′)
2r
2s
91
93
a Benzyl chloride/(nBuCHvCH)AliBu2(OEt2) = 1/1.5 mmol; Et2O =
3 mL. b Isolated yields of products.
Scheme 3
Experimental
General
and 70% yields, respectively. The same catalyst loading of
0.5 mol% was good enough for the substituted benzyl bromides
containing electron-withdrawing substituents on the aromatic
ring such as 4-chlorobenzyl bromide or 3,5-bis(trifluoromethyl)
benzyl bromide to afford the coupling product in 94% and 85%
yields, respectively (entries 12 and 13). However, an ester substi-
tuted benzyl bromide required a higher catalyst loading of 2 mol
% to afford a 90% yield of coupling product in 30 min
(entry 14).
To extend the reaction scope, the coupling reaction of benzyl
halides with functionalized alkenylaluminum reagents were then
studied. A catalyst loading of 2 mol% was employed for the
coupling reactions of benzyl bromide with the aluminum reagent
prepared by using benzyl acetylene and cyclohexyl acetylene
affording the products in 82% and 88% yields (entries 15 and
16), respectively, in 30 min. Moreover, the reagent having a
heterocyclic moiety prepared by using 3-thienyl acetylene also
gave the coupling product in 87% yield as well (entry 17).
To broaden the reaction scope, we subsequently examined
coupling reactions of benzyl chlorides (Table 3, Scheme 3). The
catalytic system with 5 mol% of catalyst loading in 2 h exhibits
similar yields toward benzyl chlorides compared to benzyl bro-
mides with 0.5 mol% in 30 min. For example, 5 mol% of cata-
lyst was used for benzyl chloride to afford coupling product 2a
in a 93% yield (Table 3, entry 1) compared to the 0.5 mol% used
1H NMR and 13C specta were obtained with a Varian Mercury-
400 (1H, 400 MHz; 13C, 100 MHz) spectrometer and chemical
shifts were measured relative to tetramethylsilane (0.00 ppm) as
the internal reference. Mass spectroscopy was performed using a
Finnigan MAT 95 XL ThermoQuest Mass Spectrometer.
DIBAL-H in hexane and alkynes were purchased from Strem
chemicals and Acros, respectively. All solvents were dried by
refluxing for at least 24 h over P2O5 (dichloromethane) or
sodium–benzophenone and were freshly distilled prior to use.
All synthesis and manipulations were carried out under a dry
nitrogen atmosphere.
General procedures for the synthesis of alkenyl aluminum
reagent
Under a dry nitrogen atmosphere, DIBAL-H in hexane was
charged into a reaction vessel. An alkyne was added via a gas-
tight syringe at room temperature. The reaction mixture was
allowed to react at 50 °C for 5 h. The resulted solution was
cooled to room temperature followed by evaporation of hexane
under reduced pressures to dryness. Then a dry ether was trans-
ferred into the reaction vessel to give an alkenylaluminum sol-
ution which was used in the coupling reaction.
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HRMS calculated for C14H20O [M+]: 204.1514, found
204.1508.
General procedures for the coupling reaction of benzylic
bromide or chloride with alkenyl aluminum reagents catalyzed
by NiCl2(PPh3)2
(E)-1-(Hept-2-enyl)-4-methoxybenzene
(2f). Pale
yellow
liquid, 0.186 g (91%). 1H NMR (400 MHz, CDCl3): δ
7.12–7.06 (m, 2 H), 6.87–6.80 (m, 2H), 5.58–5.43 (m, 2H), 3.78
(s, 3H), 3.26 (d, J = 6.0 Hz, 2H), 2.06–1.98 (m, 2H), 1.40–1.26
(m, 4H), 0.89 (t, J = 6.8 Hz, 3H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ 157.8, 133.2, 131.7, 129.3, 129.1, 113.8,
55.2, 38.1, 32.2, 31.7, 22.2, 13.9 ppm. HRMS calculated for
C14H20O [M+]: 204.1514, found 204.1512.
Under a dry nitrogen atmosphere, 0.5 mol% NiCl2(PPh3)2
(0.0032 g, 0.0050 mmol) and aluminum reagent (1.5 mmol)
were mixed in 3 mL dry diethyl ether at room temperature, and
the mixture was stirred for 15 min followed by an addition of
benzylic bromide (1.00 mmol). After stirring for 30 min at this
temperature, the reaction mixture was quenched by aqueous
hydrochloric acid (3 M, 2 mL). The organic layer was separated,
and the aqueous layer was extracted with hexane or diethyl ether
(3 × 15 mL). The combined organic phase was dried over
MgSO4, filtered, and concentrated. The residue was purified by
column chromatography using hexane as an eluent to give the
products. The coupling reaction of benzylic chloride uses 5 mol
% NiCl2(PPh3)2 (0.032 g, 0.050 mmol) with a reaction time
of 2 h.
(E)-(4-(Hept-2-enyl)phenyl)(methyl)sulfane
(2g). Colorless
liquid, 0.198 g (90%). 1H NMR (400 MHz, CDCl3): δ
7.22–7.17 (m, 2 H), 7.10 (d, J = 8.0 Hz, 2H), 5.57–5.44 (m,
2H), 3.28 (d, J = 5.2 Hz, 2H), 2.46 (s, 3H), 2.02 (dt, J = 6.0, 6.4
Hz, 2H), 1.40–1.25 (m, 4H), 0.89 (t, J = 6.8 Hz, 3H) ppm. 13C
{1H} NMR (100 MHz, CDCl3): δ 138.3, 135.4, 132.2, 129.0,
128.5, 127.3, 38.5, 32.2, 31.6, 22.2, 16.4, 13.9 ppm. HRMS cal-
culated for C14H20S [M+]: 220.1286, found 220.1280.
(E)-Hept-2-enylbenzene (2a). Colorless liquid, 0.16 g (92%).
1H NMR (400 MHz, CDCl3): δ 7.31–7.24 (m, 2H), 7.21–7.15
(m, 3H), 5.61–5.46 (m, 2H), 3.33 (d, J = 5.6 Hz, 2H), 2.02 (dt,
J = 6.0, 6.8 Hz, 2H), 1.40–1.26 (m, 4H), 0.89 (t, J = 7.2 Hz, 3H)
ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 141.1, 132.1, 128.7,
128.5, 128.3, 125.8, 39.1, 32.2, 31.7, 22.2, 13.9 ppm. HRMS
calculated for C13H18 [M+]: 174.1409, found 174.1401.
(E)-1-tert-Butyl-4-(hept-2-enyl)benzene (2h). Colorless liquid,
1
0.209 g (91%). H NMR (400 MHz, CDCl3): δ 7.32–7.28 (m,
2H), 7.11 (d, J = 8.0 Hz, 2H), 5.61–5.46 (m, 2H), 3.29 (d, J =
6.0 Hz, 2H), 2.02 (dt, J = 6.0, 6.8 Hz, 2H), 1.37–1.28 (m, 13H),
0.89 (t, J = 7.2 Hz, 3H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ 148.6, 138.1, 131.9, 128.8, 128.1, 125.2, 38.5, 34.3,
32.2, 31.7, 31.4, 22.3, 14.0 ppm. HRMS calculated for C17H26
[M+]: 230.2035, found 230.2030.
(E)-1-(Hept-2-enyl)-2-methylbenzene (2b). Colorless liquid,
1
0.16 g (85%). H NMR (400 MHz, CDCl3): δ 7.15–7.08 (m,
4H), 5.57–5.49 (m, 1H), 5.46–5.37 (m, 1H), 3.30 (d, J = 6.4 Hz,
2H), 2.28 (s, 3H), 2.01 (dt, J = 6.4, 6.8 Hz, 2H), 1.38–1.24 (m,
4H), 0.88 (t, J = 6.4 Hz, 3H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ 139.1, 136.2, 131.9, 130.0, 128.9, 127.8, 126.0,
125.9, 36.6, 32.2, 31.7, 22.2, 19.3, 13.9 ppm. HRMS calculated
for C14H20 [M+]: 188.1565, found 188.1557.
(E)-2-(Hept-2-enyl)biphenyl (2i). Colorless liquid, 0.175 g
(70%). H NMR (400 MHz, CDCl3): δ 7.42–7.20 (m, 9H), 5.46
1
(dt, J = 6.4, 15.2. Hz, 1H), 5.29 (dt, J = 6.4, 15.2 Hz, 1H), 3.27
(d, J = 6.4 Hz, 2H), 1.97 (dt, J = 6.4, 6.8 Hz, 2H), 1.34–1.23
(m, 4H), 0.87 (t, J = 6.8 Hz, 3H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ 141.9, 141.8, 138.3, 132.0, 130.0, 129.6,
129.3, 128.9, 127.9, 127.3, 126.8, 125.8, 36.3, 32.0, 31.6, 22.2,
13.9 ppm. HRMS calculated for C19H22 [M+]: 250.1722, found
250.1716.
(E)-1-(Hept-2-enyl)-3-methylbenzene (2c). Colorless liquid,
1
0.171 g (91%). H NMR (400 MHz, CDCl3): δ 7.20–7.14 (m,
1H), 7.01–6.97 (m, 3H), 5.60–5.46 (m, 2H), 3.29 (d, J = 5.6 Hz,
2H), 2.32 (s, 3H), 2.02 (dt, J = 6.4, 6.4 Hz, 2H), 1.40–1.26 (m,
4H), 0.89 (t, J = 7.2 Hz, 3H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ 141.1, 137.9, 132.0, 129.3, 128.8, 128.2, 126.6,
125.5, 39.0, 32.2, 31.7, 22.2, 21.4, 13.9 ppm. HRMS calculated
for C14H20 [M+]: 188.1565, found 188.1561.
(E)-3-(Hept-2-enyl)biphenyl (2j). Colorless liquid, 0.230 g
(92%). 1H NMR (400 MHz, CDCl3): δ 7.62–7.57 (m, 2H),
7.46–7.40 (m, 4H), 7.39–7.31 (m, 2H), 7.20–7.16 (m, 1H),
5.66–5.51 (m, 2H), 3.40 (d, J = 6.0 Hz, 2H), 2.05 (dt, J = 6.0,
6.4 Hz, 2H), 1.42–1.28 (m, 4H), 0.91 (t, J = 7.2 Hz, 3H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ 141.6, 141.4, 141.3,
132.3, 128.71, 128.66, 128.60, 127.42, 127.38, 127.2, 127.1,
124.8, 39.1, 32.2, 31.6, 22.2, 13.9 ppm. HRMS calculated for
C19H22 [M+]: 250.1722, found 250.1713.
(E)-1-(Hept-2-enyl)-4-methylbenzene (2d). Colorless liquid,
1
0.173 g (92%). H NMR (400 MHz, CDCl3): δ 7.14–7.05 (m,
4H), 5.58–5.44 (m, 2H), 3.28 (d, J = 5.6 Hz, 2H), 2.32 (s, 3H),
2.01 (dt, J = 6.8, 6.8 Hz, 2H), 1.40–1.24 (m, 4H), 0.89 (t, J =
7.2 Hz, 3H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 138.1,
135.3, 131.8, 129.01, 128.98, 128.3, 38.6, 32.2, 31.7, 22.2,
21.0, 13.9 ppm. HRMS calculated for C14H20 [M+]: 188.1565,
found 188.1558.
(E)-1-(Hept-2-enyl)-3,5-dimethoxybenzene (2k). Pale yellow
liquid, 0.213 g (91%). 1H NMR (400 MHz, CDCl3): δ
6.38–6.33 (m, 2H), 6.30 (t, J = 2.4 Hz, 1H), 5.58–5.47 (m, 2H),
3.77 (s, 6H), 3.26 (d, J = 4.8 Hz, 2H), 2.03 (dt, J = 4.8, 6.8 Hz,
2H), 1.41–1.27 (m, 4H), 0.89 (t, J = 6.8 Hz, 3H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ 160.8, 143.6, 132.4, 128.3, 106.5,
98.0, 55.2, 39.3, 32.1, 31.6, 22.2, 13.9 ppm. HRMS calculated
for C15H22O2 [M+]: 234.1620, found 234.1613.
(E)-1-(Hept-2-enyl)-3-methoxybenzene
(2e). Pale
yellow
1
liquid, 0.19 g (93%). H NMR (400 MHz, CDCl3): δ 7.23–7.16
(m, 1H), 6.80–6.70 (m, 3H), 5.60–5.47 (m, 2H), 3.79 (s, 3H),
3.30 (d, J = 5.2 Hz, 2H), 2.03 (dt, J = 6.0, 6.8 Hz, 2H),
1.40–1.26 (m, 4H), 0.89 (t, J = 7.2 Hz, 3H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ 159.6, 142.7, 132.2, 129.2, 128.5,
120.8, 114.1, 111.2, 55.0, 39.0, 32.1, 31.6, 22.2, 13.9 ppm.
(E)-1-Chloro-4-(hept-2-enyl)benzene (2l). Colorless liquid,
1
0.196 g (94%). H NMR (400 MHz, CDCl3): δ 7.30–7.24 (m,
2H), 7.16–7.10 (m, 2H), 5.60–5.48 (m, 2H), 3.31 (d, J = 4.8 Hz,
4246 | Org. Biomol. Chem., 2012, 10, 4243–4248
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2H), 2.06 (dt, J = 5.2, 6.4 Hz, 2H), 1.42–1.30 (m, 4H), 0.93 (t, J
= 7.2 Hz, 3H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 139.5,
132.6, 131.6, 129.8, 128.4, 128.1, 38.3, 32.1, 31.6, 22.2,
13.9 ppm. HRMS calculated for C13H17Cl [M+]: 208.1019,
found 208.1010.
11.2 Hz, 1H), 3.31 (d, J = 5.6 Hz, 2H), 2.02 (dt, J = 6.0, 6.8 Hz,
2H), 1.39–1.26 (m, 4H), 0.89 (t, J = 7.2 Hz, 3H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ 140.9, 136.7, 135.4, 132.2, 128.6,
128.5, 126.2, 112.9, 38.8, 32.2, 31.7, 22.2, 13.9 ppm. HRMS
calculated for C15H20 [M+]: 200.1565, found 200.1572.
(E)-1-(Hept-2-enyl)-3,5-bis(trifluoromethyl)benzene (2m).
Pale yellow liquid, 0.263 g (85%). 1H NMR (400 MHz, CDCl3):
δ 7.71 (s, 1H), 7.63 (s, 2H), 5.63–5.49 (m, 2H), 3.45 (d, J = 6.0
Hz, 2H), 2.09–2.04 (m, 2H), 1.42–1.28 (m, 4H), 0.90 (t, J = 6.8
Hz, 3H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 143.7,
134.4, 131.6 (q, J = 32.8 Hz), 128.7, 126.6, 123.5 (q, J = 270.3
Hz), 120.0 (q, J = 3.6 Hz), 38.6, 32.2, 31.5, 22.2, 13.8 ppm.
HRMS calculated for C15H16F6 [M+]: 310.1156, found
310.1165.
Acknowledgements
Financial support from the National Science Council of Taiwan,
ROC, under Grant No. NSC 99-2113-M-005-005-MY3 is
appreciated.
Notes and references
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959; (b) N. Jabri, A. Alexakis and J. F. Normant, Tetrahedron Lett., 1981,
22, 3851; (c) A. Alexakis, C. Chuit, M. Commercon-Bourgain, J.
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(E)-Methyl 4-(hept-2-enyl)benzoate (2n). Colorless liquid,
0.208 g (90%). H NMR (400 MHz, CDCl3): δ 7.98–7.93 (m,
1
2H), 7.28–7.22 (m, 2H), 5.59–5.47 (m, 2H), 3.90 (s, 3H), 3.37
(d, J = 4.8 Hz, 2H), 2.03 (dt, J = 5.2, 6.8 Hz, 2H), 1.41–1.25
(m, 4H), 0.89 (t, J = 7.2 Hz, 3H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ 167.0, 146.5, 132.8, 129.6, 128.4, 127.8,
127.6, 51.8, 38.9, 32.1, 31.5, 22.1, 13.8 ppm. HRMS calculated
for C15H20O2 [M+]: 232.1463, found 232.1457.
(E)-1,4-Diphenylbut-2-ene (2o). Colorless liquid, 0.170 g
(82%). 1H NMR (400 MHz, CDCl3): δ 7.32–7.17 (m, 10H),
5.68–5.66 (m, 2H), 3.37 (d, J = 4.8 Hz, 4H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ 140.7, 130.4, 128.5, 128.4, 126.0,
39.0 ppm.
(E)-(3-Cyclohexylallyl)benzene (2p). Colorless liquid, 0.176 g
(88%). 1H NMR (400 MHz, CDCl3): δ 7.30–7.25 (m, 2H),
7.20–7.14 (m, 3H), 5.56–5.43 (m, 2H), 3.31 (d, J = 5.6 Hz, 2H),
1.99–1.89 (m, 1H), 1.78–1.60 (m, 5H), 1.32–1.02 (m, 5H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ 141.2, 138.1, 128.4,
128.3, 126.1, 125.8, 40.6, 39.1, 33.1, 26.2, 26.1 ppm. HRMS
calculated for C15H20 [M+]: 200.1565, found 200.1563.
(E)-3-(3-Phenylprop-1-enyl)thiophene
(2q). Pale
yellow
7 (a) I. Pèrez, J. P. Sestelo and L. A. Sarandeses, Org. Lett., 1999, 1, 1267;
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liquid, 0.174 g (87%). 1H NMR (400 MHz, CDCl3): δ
7.34–7.29 (m, 2H), 7.27–7.22 (m, 4H), 7.21–7.17 (m, 1H),
7.10–7.07 (m, 1H), 6.46 (d, J = 15.6 Hz, 1H), 6.21 (dt, J = 6.8,
15.6 Hz, 1H), 3.51 (d, J = 6.8 Hz, 2H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ 140.1, 140.0, 129.2, 128.7, 128.5, 126.2,
125.8, 125.3, 125.0, 121.0, 39.2 ppm. HRMS calculated for
C13H12S [M+]: 200.0660, found 200.0666.
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W. Lee and E. J. Corey, J. Am. Chem. Soc., 2001, 123, 1872; (i) C.
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12 E. Negishi and S. Baba, Chem. Commun., 1976, 597.
13 (a) A. Suzuki and H. C. Brown, Suzuki Coupling; Organic Syntheses via
Boranes Series, Aldrich Chemical Co., Milwaukee, 2003, vol. 3;
(b) N. Jabri, A. Alexakis and J. F. Normant, Tetrahedron Lett., 1982, 23,
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(E)-1-Fluoro-4-(hept-2-enyl)benzene (2r). Colorless liquid,
1
0.174 g (91%). H NMR (400 MHz, CDCl3): δ 7.15–7.09 (m,
2H), 6.99–6.92 (m, 2H), 5.57–5.44 (m, 2H), 3.28 (d, J = 5.2 Hz,
2H), 2.02 (dt, J = 6.4, 6.8 Hz, 2H), 1.40–1.25 (m, 4H), 0.89 (t, J
= 7.2 Hz, 3H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 161.4
(d, J = 242 Hz), 136.7 (d, J = 2.8 Hz), 132.3, 129.8 (d, J = 8.2
Hz), 128.6, 115.0 (d, J = 20.9 Hz), 38.2, 32.2, 31.7, 22.2,
13.9 ppm. HRMS calculated for C13H17F [M+]: 192.1314, found
192.1317.
(E)-1-(Hept-2-enyl)-4-vinylbenzene (2s). Colorless liquid,
1
0.186 g (93%). H NMR (400 MHz, CDCl3): δ 7.33 (d, J = 8.0
Hz, 2H), 7.14 (d, J = 8.0 Hz, 2H), 6.69 (dd, J = 10.8, 17.6 Hz,
1H), 5.70 (d, J = 17.6 Hz, 1H), 5.58–5.46 (m, 2H), 5.18 (d, J =
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