FeX3-promoted intermolecular addition of benzylic alcohols to aromatic alkynes: A mild and efficient strategy for the synthesis of alkenyl halides

Article abstract of DOI:10.1002/ejoc.200901020

A convenient, effective, mild and simple strategy has been developed for the synthesis of alkenyl halides by the intermolecular addition of benzylic alcohols to aromatic alkynes. The reactions were carried out in the presence of iron(III) bromide or chloride in 1, 2-dibromoethane without additives in air at room temperature. Alkenyl bromides and chlorides were obtained with high regio- and stereoselectivity (E/Z up to 99:1) in good-to-excellent yields in 0.5-1 h under mild reaction conditions.

Full text of DOI:10.1002/ejoc.200901020

FULL PAPER
DOI: 10.1002/ejoc.200901020
FeX3-Promoted Intermolecular Addition of Benzylic Alcohols to Aromatic
Alkynes: A Mild and Efficient Strategy for the Synthesis of Alkenyl Halides
Kai Ren,[a] Min Wang,[a] and Lei Wang*[a,b]
Keywords: Alkenes / Alkynes / Alcohols / Iron / Synthetic methods / Halides
A convenient, effective, mild and simple strategy has been
developed for the synthesis of alkenyl halides by the inter-
molecular addition of benzylic alcohols to aromatic alkynes.
The reactions were carried out in the presence of iron(III)
bromide or chloride in 1,2-dibromoethane without additives
in air at room temperature. Alkenyl bromides and chlorides
were obtained with high regio- and stereoselectivity (E/Z up
to 99:1) in good-to-excellent yields in 0.5–1 h under mild re-
action conditions.
Introduction
forming reactions is a catalytic amount of CuII and not
FeIII [14]
It is assumed that the reported reactions with FeCl3
.
Lewis acid promoted carbon–carbon bond-forming reac-
tions by the addition of carbonium ions to alkenes have
been extensively explored in the past.[1] However, compared
with alkenes, the use of alkynes as electron-rich substrates
attacked by carbonium ions has been limited.[2] In addition,
most of these transformations are catalysed by anhydrous
zinc(II) chloride and bromide.[2c,2d] Clearly, these methods
have significant drawbacks, such as the difficulty in hand-
ling the moisture-sensitive catalyst, the need for anhydrous
conditions and long reaction times. Thus, the development
of more convenient and effective Lewis acid mediators for
the addition of electrophiles to alkynes is desirable.
may in certain cases be significantly affected by trace quan-
tities of other metals, particularly copper. However, we are
certain that it is desirable to expand the application scope
of iron salts in organic transformations due to their unique
properties and significant advantages for both the academic
and industrial community. Herein we wish to report an ef-
ficient and mild iron-promoted intermolecular addition of
benzylic alcohols to aromatic alkynes, which generates the
corresponding alkenyl halides in high yields.
The relative stabilities of benzylic, allylic and propargylic
carbonium ions are well documented and have been the
subject of numerous theoretical and experimental stud-
Iron is one of the most abundant metals on the earth and ies.[15] Yet, the availability of these cations has not resulted
consequently one of the most inexpensive and environmen- in their general use as synthetic intermediates due to the
tally friendly ones. Iron salts as effective, alternative and strong acidic conditions required to generate them.[16] The
promising transition-metal catalysts have received much at- direct utilization of benzylic alcohols as electrophiles would
tention because of their unique properties.[3] Over the past be quite useful as they would be more atom-economic and
few years, iron-catalysed oxidation,[4] hydrogenation,[5] environmentally friendly and are commercially available.[17]
hydrosilylation,[6] rearrangement,[7] Michael addition[8] and To the best of our knowledge, there is only one report, by
Mannich reactions[9] have been intensively investigated. In Kabalka et al., of the reactions of benzylic alcohols with
addition, iron-catalysed C–S,[10] C–N,[11] C–O[12] and C–C aromatic alkynes in the presence of nBuLi and BCl3, which
bond-forming reactions (such as Sonogashira, Heck, Negi- gives (E)-alkenyl chlorides as the major products.[18] It
shi, Kumada, and Suzuki reactions) have recently been de- would be desirable to develop a protocol for the direct ad-
veloped.[13] However, Buchwald and Bolm recently found dition of benzylic alcohols to alkynes mediated by a milder
that the actual catalyst for the above C–N (–S, –O) bond- Lewis acid. During our ongoing efforts devoted to iron-
mediated organic reactions, we have developed an effective
and mild FeX3-promoted strategy for the synthesis of alk-
enyl halides by the addition of benzylic alcohols to aromatic
alkynes. The reactions were carried out in the presence of
[a] Department of Chemistry, Huaibei Coal Teachers College,
iron(III) bromide or chloride in 1,2-dibromoethane without
Huaibei, Anhui 235000, P. R. China
any additives in air and generated alkenyl bromides or chlo-
rides in high yields and with high regio- and stereoselecti-
vity at room temperature within 1 h with the E isomers as
the major products (E/Z up to 99:1; Scheme 1).
Fax: +86-561-3090-518
E-mail: leiwang@hbcnc.edu.cn
[b] State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, P. R. China
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K. Ren, M. Wang, L. Wang
FULL PAPER
cellent solvent for the addition of diphenylmethanol to
phenylacetylene, giving a quantitative yield of 3a in the
presence of 33.33 mol-% FeBr3 at room temperature in 1 h
(Table 1, entry 6). The use of 1,2-dibromoethane afforded
4a in good yield with FeCl3 as the promoter, although the
yield of 4a was slightly lower than that of 3a (Table 1, En-
try 5 vs. 6). In other classic solvents, such as toluene and
1,4-dioxane, the yields of the desired addition products were
dramatically lowered (Table 1, Entries 7 and 8). Unfortu-
nately, the desired product was not isolated when the reac-
tion was carried out in DMSO, DMF, C2H5OH, CH3NO2
or CH3CN (Table 1, Entries 7–13). Interestingly, 1,3,3-tri-
phenylpropan-1-one was isolated in yields of 10–20% when
the reaction of diphenylmethanol and phenylacetylene was
carried out in CH3NO2 or CH3CN in the presence of FeBr3
(Table 1, Entries 12 and 13).[19] The effect of temperature
on the reaction was also surveyed, and the results show that
the yield of 3a was not improved when the reaction tem-
perature was increased to 50 or 75 °C (Table 1, Entries 14
and 15).
With respect to the iron salt loading, 33.33 mol-% of
FeBr3 or FeCl3 was found to be optimal. When 20 or
10 mol-% of FeBr3 was used, the desired product 3a was
isolated in 61 and 29% yields, respectively (Table 1, En-
tries 16 and 17). In this reaction, FeBr3 and FeCl3 act as
both Lewis acid promoter and the source of halide ions.
To examine the scope of the reaction, different types of
benzylic alcohols were prepared according to the literature
or purchased commercially and subjected to the previously
optimized reaction conditions. The results are outlined in
Table 2. Initially, phenylacetylene was used as the model
substrate, and a variety of benzylic alcohols were examined
in the presence of FeBr3. As can be seen from Table 2, sec-
ondary benzylic alcohols were often much more reactive
than primary ones (Table 2, Entries 1–7 and 11–14 vs. 8–
10) and gave the desired addition products in excellent
yields with an E/Z ratio in the range of 4:1 to 14:1 (Table 2,
Entries 1–7). Secondary benzylic alcohols with either elec-
tron-donating or -withdrawing groups attached to the ben-
zene ring smoothly underwent the addition reaction and
generated the corresponding products in high yields
(Table 2, Entries 2–5). Moreover, steric effects were not ob-
vious (Table 2, Entry 3). However, when other secondary or
tertiary alcohols, such as tert-butyl alcohol, 2-propanol or
cyclohexanol, were treated with phenylacetylene, the desired
addition products were not obtained.
Scheme 1.
Results and Discussion
To optimize the reaction conditions and identify the best
iron species, solvent and reaction temperature, di-
phenylmethanol and phenylacetylene were chosen as model
substrates, and the results are summarized in Table 1. When
33.33 mol-% of FeBr3 or FeCl3 was used as the promoter at
room temperature in 1,2-dichloroethane, the desired alkenyl
bromide (3a) and chloride (4a) were obtained in 73 and
55% yields, respectively (Table 1, Entries 1 and 2). Interest-
ingly, 4a was isolated in only 30% yield when FeCl3·6H2O
was used instead of FeCl3, which showed that FeCl3 is a far
better Lewis acid (Table 1, Entry 3). However, FeCl2 did not
promote this addition reaction and the starting materials
were recovered (Table 1, Entry 4).
Table 1. Optimization of the reaction conditions for the addition
of diphenylmethanol to phenylacetylene.[a]
Entry
Fe salt
Solvent
Product
Yield [%][b]
1
2
3
FeCl3
FeBr3
FeCl3·6H2O
FeCl2
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
BrCH2CH2Br
BrCH2CH2Br
toluene
1,4-dioxane
DMSO
DMF
C2H5OH
CH3NO2
CH3CN
BrCH2CH2Br
BrCH2CH2Br
BrCH2CH2Br
BrCH2CH2Br
4a
3a
4a
–
4a
3a
3a
3a
–
–
–
–
–
55
73
30
0
85
98
15
10
4
5
6
7
8
FeCl3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
FeBr3
9
0
0
0
10
11
12
13
14[d]
15[e]
16[f]
17[g]
0 (18)[c]
0 (13)[c]
98
3a
3a
3a
3a
Various alkynes were investigated as substrates in the re-
action with diphenylmethanol under the standard reaction
conditions (Table 2). Aromatic terminal alkynes with either
electron-donating or -withdrawing functional groups, such
as methyl, fluoro, bromo and chloro groups, reacted with
diphenylmethanol in the presence of FeBr3 to afford the
corresponding alkenyl bromides in good yields and stereo-
selectivities (Table 2, Entries 11–14). A 1,2-disubstituted
ethyne, 1,2-diphenylethyne, also underwent the reaction
99
61
29
[a] Reaction conditions: diphenylmethanol (1.0 equiv.), phenyl-
acetylene (1.1 equiv.), Fe salt (0.3333 equiv.) and solvent
(1.0 mLequiv.–1), 25 °C, 1 h. [b] Isolated yield of the E/Z mixture.
[c] Yield of 1,3,3-triphenylpropan-1-one. [d] At 50 °C. [e] At 75 °C.
[f] In the presence of 0.2 equiv. FeBr3. [g] In the presence of
0.1 equiv. FeBr3.
Further investigation of the solvent effect indicated that with diphenylmethanol to produce the desired product in a
the nature of the reaction media significantly affects the re- moderate yield and with a very high E/Z ratio (25:1,
action (Table 1). 1,2-Dibromoethane was found to be an ex- Table 2, Entry 15). However, aliphatic terminal alkynes,
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Eur. J. Org. Chem. 2010, 565–571

Addition of Benzylic Alcohols to Aromatic Alkynes
Table 2. FeBr3-promoted addition of benzylic alcohols to alkynes.[a]
Eur. J. Org. Chem. 2010, 565–571
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567

K. Ren, M. Wang, L. Wang
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Table 2. (Continued)
[a] Reaction conditions: alcohol (1 equiv.), alkyne (1.1 equiv.), FeBr3 (Ͼ98%, 0.3333 equiv.) and 1,2-dibromoethane (1.0 mLequiv.–1) at
1
room temperature (25 °C) for 0.5 h. [b] Isolated yield of the E/Z mixture; the E/Z ratio was determined by H NMR spectroscopy.
such as 1-octyne and 1-decyne, were inactive in this reac- the range of 5:1 to 99:1 (Table 3, Entries 1–5). The results
tion.
also revealed that the electronic characteristics of general
To synthesize different kinds of alkenyl chlorides, the re- electron-donating (such as CH3) or -withdrawing groups
actions of a variety of alcohols and alkynes were examined (such as F, Cl) attached to the benzene ring of the benzylic
in the presence of FeCl3 under the above reaction condi- alcohols or aromatic alkynes were relatively insensitive to
tions. The results in Table 3 show that secondary benzylic the reaction conditions (Table 3, Entries 1–5). However,
alcohols and terminal aromatic alkynes are good substrates when primary benzylic alcohols and aliphatic terminal al-
for the addition reaction, and 81–89% yields of the desired kynes served as the starting materials, poor yields of the
alkenyl chlorides were obtained in 1 h with an E/Z ratio in corresponding products were observed.
Table 3. FeCl3-promoted addition of benzyl alcohols to alkynes.[a]
[a] Reaction conditions: benzylic alcohol (1.0 equiv.), arylalkyne (1.1 equiv.), FeCl3 (Ͼ99.99%, 0.3333 equiv.) and 1,2-dibromoethane
1
(1.0 mLequiv.–1) at room temperature (25 °C) for 1 h. [b] Isolated yield of the E/Z mixture; the E/Z ratio was determined by H NMR
spectroscopy.
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Eur. J. Org. Chem. 2010, 565–571

Addition of Benzylic Alcohols to Aromatic Alkynes
A possible mechanism for the FeX3-promoted addition desired products in good to excellent yields at room tem-
of benzylic alcohol to aromatic alkyne is shown in perature in 0.5–1 h with high regio- and stereoselectivities
Scheme 2. Benzyl alcohol is activated by the Lewis acid, (E/Z ratio up to 99:1). In addition, the reaction may expand
FeBr3 or FeCl3, to form a carbocation intermediate A and the scope of iron salts as a versatile tool in organic synthe-
Fe(OH)X3– as an ion-pair in the first cycle. The carbocation sis. Further investigations of the application of this kind of
A attacks the electron-rich aromatic alkyne with excellent iron salt in asymmetric organic reactions are underway in
regioselectivity to generate vinyl cation B. The sp-hy- our laboratory.
bridized vinyl cation B can be attacked by X– in Fe(OH)-
–
X3 to give an E/Z mixture of the alkenyl halide with good
Experimental Section
stereoselectivity (E isomer as the major product) and
Fe(OH)X2, which is used to activate the benzyl alcohol in
the second cycle, until it is finally transformed into Fe-
General: All reactions were carried out in air. All reagents were
purchased from commercial suppliers and used after further purifi-
(OH)3 without activity. It is clear that FeX3 (X = Br or Cl) cation. 1H and 13C NMR spectra were recorded with a Bruker Av-
ance NMR spectrometer (400 or 100 MHz, respectively) with
CDCl3 as solvent. Chemical shifts are given in ppm relative to tet-
ramethylsilane as the internal standard. High-resolution mass spec-
trometry data were collected with a Waters micromass GCT prem-
ier instrument.
acts as both Lewis acid promoter and the source of halide
ions. To lower the FeX3 loading, the reaction of di-
phenylmethanol and phenylacetylene was examined in the
presence of 10 mol-% of FeCl3 with aq. NaCl (2 equiv.), aq.
HCl (2 equiv.) or tetrabutylammonium chloride (2 equiv.)
as additive to provide chloride ions as nucleophiles to at-
tack the vinyl cation B. However, the yield of the desired
product 4a was not improved in comparison with the reac-
tion without additive, even with a prolonged reaction time
(10 h). Meanwhile, the reaction of diphenylmethanol with
phenylacetylene in the presence of a copper salt or oxide,
such as CuCl2, CuBr, CuI or Cu2O (0.50 equiv.), in
BrCH2CH2Br was examined. However, the desired product
was not observed.
General Procedure for the FeX3-Promoted Intermolecular Addition
of Benzylic Alcohols to Aromatic Alkynes: A reaction tube equipped
with a magnetic stirring bar was charged with the benzylic alcohol
(1.0 mmol), arylalkyne (1.1 mmol), FeBr3 or FeCl3 (0.3333 mmol)
and 1,2-dibromoethane (1.0 mL). The reaction vessel was placed in
the open air at room temperature (25 °C). After stirring the mixture
at this temperature for 0.5–1 h, it was diluted with dichlorometh-
ane. The resulting solution was directly filtered through a pad of
silica gel by using a sintered-glass funnel and concentrated under
reduced pressure. The residue was purified by flash chromatog-
raphy on silica gel (eluent: petroleum ether) to give the desired alk-
enyl bromide or chloride as product.
(E)-3a:[2a] 1H NMR (400 MHz, CDCl3): δ = 7.20–7.13 (m, 10 H),
7.08 (d, J = 6.8 Hz, 2 H), 6.99 (d, J = 6.0 Hz, 3 H), 6.60–6.56 (m,
1 H), 4.61 (d, J = 10.8 Hz, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 142.9, 138.3, 135.5, 128.7, 128.6, 128.3, 128.1, 127.7,
126.6, 121.2, 51.6 ppm.
(E)-3b: 1H NMR (400 MHz, CDCl3): δ = 7.34–7.14 (m, 10 H), 7.00
(d, J = 8.4 Hz, 3 H), 6.56 (d, J = 10.8 Hz, 1 H), 4.64 (d, J =
10.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 141.0, 138.0,
134.3, 132.7, 129.4, 128.9, 128.5, 127.7, 122.2, 50.4 ppm. HRMS
(ESI): calcd. for C21H15BrCl2 [M]+ 415.9734; found 415.9731.
(E)-3c: 1H NMR (400 MHz, CDCl3): δ = 7.31–7.17 (m, 11 H),
7.14–7.09 (m, 3 H), 6.65 (d, J = 10.8 Hz, 1 H), 5.20 (d, J = 10.4 Hz,
1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 142.1, 140.5, 138.1,
134.1, 133.8, 129.9, 129.7, 128.8, 128.7, 128.6, 128.2, 128.0, 127.9,
127.1, 126.6, 122.6, 48.3 ppm. HRMS (ESI): calcd. for C21H16BrCl
[M]+ 382.0124; found 382.0120.
(E)-3d: 1H NMR (400 MHz, CDCl3): δ = 7.31–7.08 (m, 11 H),
7.08–7.00 (m, 3 H), 6.62 (d, J = 10.8 Hz, 1 H), 4.67 (d, J = 10.8 Hz,
1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 142.4, 141.5, 138.1,
134.9, 132.4, 129.4, 128.8, 128.7, 128.6, 128.4, 128.0, 126.8, 121.7,
51.0 ppm. HRMS (ESI): calcd. for C21H16BrCl [M]+ 382.0124;
found 382.0130.
Scheme 2. Possible mechanism for the FeX3-promoted addition of
benzylic alcohol to aromatic alkyne.
(E)-3e: 1H NMR (400 MHz, CDCl3): δ = 7.32–7.01 (m, 14 H), 6.67
(d, J = 10.4 Hz, 1 H), 4.68 (d, J = 10.8 Hz, 1 H), 2.92 (s, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 143.2, 140.0, 139.7, 138.3, 136.2,
135.6, 129.3, 128.8, 128.7, 128.6, 128.3, 128.1, 126.5, 121.0, 51.2,
21.0 ppm. HRMS (ESI): calcd. for C22H19Br [M]+ 362.0670; found
362.0668.
Conclusions
We have successfully developed a convenient, effective
and mild strategy for the synthesis of alkenyl bromides and
chlorides by the intermolecular addition of benzylic
alcohols to aromatic alkynes. The reactions were carried out
in the presence of FeBr3 or FeCl3 (33.33 mol-%) in 1,2-di-
(E)-3f:[2a] 1H NMR (400 MHz, CDCl3): δ = 7.32–7.24 (m, 7 H),
bromoethane without any additive in air and generated the 7.18–7.11 (m, 3 H), 6.34 (d, J = 10.4 Hz, 1 H), 3.52–3.47 (m, 1 H),
Eur. J. Org. Chem. 2010, 565–571
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K. Ren, M. Wang, L. Wang
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1.30 (d, J = 6.8 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 3 H), 6.22 (d, J = 10.0 Hz, 1 H), 4.61 (d, J = 11.2 Hz, 1 H) ppm.
144.5, 138.7, 138.4, 128.7, 128.6, 128.5, 128.3, 126.7, 126.4, 119.8,
40.7, 22.0 ppm.
13C NMR (100 MHz, CDCl3): δ = 141.3, 140.9, 136.5, 132.7, 132.4,
129.4, 128.9, 128.5, 128.4, 126.6, 49.5 ppm. HRMS (ESI): calcd.
for C21H15Cl3 [M]+ 372.0239; found 372.0245.
(E)-4c:[18b] 1H NMR (400 MHz, CDCl3): δ = 7.32–7.20 (m, 8 H),
7.17–7.12 (m, 6 H), 6.41 (d, J = 11.2 Hz, 1 H), 4.79 (d, J = 11.2 Hz,
1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 143.4, 138.9, 134.0,
131.6, 131.0, 129.0, 128.6, 128.5, 128.2, 126.6, 50.7, 21.3 ppm.
(E)-4d: 1H NMR (400 MHz, CDCl3): δ = 7.26–7.21 (m, 6 H), 7.15–
7.11 (m, 2 H), 7.03 (d, J = 7.6 Hz, 4 H), 6.94 (t, J = 8.8 Hz, 2 H),
6.37 (d, J = 11.2 Hz, 1 H), 4.64 (d, J = 10.8 Hz, 1 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 164.0, 161.5, 143.1, 132.9, 131.7,
130.6, 130.5, 130.4, 128.7, 128.1, 126.7, 115.5, 115.3, 50.8 ppm.
HRMS (ESI): calcd. for C21H16ClF [M]+ 322.0925; found
322.0930.
(E)-4e:[2a] 1H NMR (400 MHz, CDCl3): δ = 7.26–7.18 (m, 7 H),
7.09–7.05 (m, 3 H), 6.03 (d, J = 10.8 Hz, 1 H), 3.50–3.46 (m, 1 H),
1.25 (d, J = 6.8 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
144.9, 137.2, 134.2, 130.1, 128.6, 128.3, 127.0, 126.7, 126.5, 126.4,
39.6, 22.4 ppm.
(E)-3g: 1H NMR (400 MHz, CDCl3): δ = 7.40–7.34 (m, 7 H), 7.28–
7.16 (m, 3 H), 6.44 (d, J = 10.8 Hz, 1 H), 3.28 (q, J = 7.2, 10.8 Hz,
1 H), 1.79–1.71 (m, 2 H), 0.87 (t, J = 7.6 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 143.5, 138.8, 137.4, 128.8, 128.6, 128.4,
128.2, 127.2, 126.4, 120.4, 48.3, 29.7, 11.9 ppm. HRMS (ESI):
calcd. for C17H17Br [M]+ 300.0514; found 300.0512.
(E)-3h:[2a] 1H NMR (400 MHz, CDCl3): δ = 7.41–7.13 (m, 10 H),
6.38 (t, J = 7.2 Hz, 1 H), 3.73 (d, J = 7.2 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 139.7, 139.1, 130.2, 128.6, 128.5, 128.2,
127.6, 126.4, 126.2, 38.8 ppm.
(E)-3i: 1H NMR (400 MHz, CDCl3): δ = 7.36–7.18 (m, 8 H), 7.06–
7.04 (m, 1 H), 6.35–6.30 (m, 1 H), 3.68 (d, J = 7.2 Hz, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 139.5, 137.5, 132.2, 129.8, 129.5,
128.9, 128.7, 128.3, 127.6, 121.9, 38.1 ppm. HRMS (ESI): calcd.
for C15H12BrCl [M]+ 305.9811; found 305.9808.
(E)-3j: 1H NMR (400 MHz, CDCl3): δ = 7.39–7.28 (m, 5 H), 7.17–
7.01 (m, 4 H), 6.39–6.34 (m, 1 H), 3.32 (d, J = 8.0 Hz, 2 H), 2.31
(s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 138.4, 136.0,
135.9, 132.7, 129.3, 129.0, 128.3, 128.1, 127.6, 121.1, 36.3,
21.0 ppm. HRMS (ESI): calcd. for C16H15Br [M]+ 286.0357; found
286.0353.
Acknowledgments
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (No. 20972057).
(E)-3k:[18b] 1H NMR (400 MHz, CDCl3): δ = 7.34–7.32 (m, 1 H),
7.14–7.07 (m, 9 H), 7.00–6.98 (m, 4 H), 6.56–6.50 (m, 1 H), 4.62
(d, J = 10.4 Hz, 1 H), 2.19 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 143.1, 138.6, 135.4, 135.1, 129.0, 128.6, 128.5, 128.1,
126.6, 121.5, 51.6, 21.1 ppm.
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(E)-3l: 1H NMR (400 MHz, CDCl3): δ = 7.20–7.07 (m, 9 H), 7.00–
6.98 (m, 3 H), 6.90–6.83 (m, 2 H), 6.59 (d, J = 10.8 Hz, 1 H), 4.56
(d, J = 10.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
163.8, 161.3, 142.8, 135.9, 134.4, 134.3, 130.7, 130.6, 128.7, 128.3,
126.7, 124.9, 120.0, 115.5, 115.3, 51.7 ppm. HRMS (ESI): calcd.
for C21H16BrF [M]+ 366.0419; found 366.0419.
(E)-3m: 1H NMR (400 MHz, CDCl3): δ = 7.31–7.21 (m, 10 H),
7.09 (d, J = 8.0 Hz, 4 H), 6.69 (d, J = 10.8 Hz, 1 H), 4.66 (d, J =
10.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 142.7, 136.7,
136.2, 134.7, 130.1, 128.7, 128.6, 128.0, 126.7, 119.8, 51.7 ppm.
HRMS (ESI): calcd. for C21H16BrCl [M]+ 382.0124; found
382.0117.
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(E)-3n: 1H NMR (400 MHz, CDCl3): δ = 7.47–7.39 (m, 2 H), 7.30–
7.17 (m, 9 H), 7.11–7.09 (m, 3 H), 6.70 (d, J = 10.8 Hz, 1 H), 4.66
(d, J = 10.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
142.7, 137.2, 136.2, 131.6, 130.4, 128.7, 128.0, 126.7, 123.0, 119.8,
51.7 ppm. HRMS (ESI): calcd. for C21H16Br2 [M]+ 425.9617;
found 425.9618.
(E)-3o:[2a] 1H NMR (400 MHz, CDCl3): δ = 7.52–7.50 (m, 1 H),
7.36–7.16 (m, 14 H), 4.03 (q, J = 7.6, 7.6 Hz, 1 H), 1.30 (d, J =
7.6 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 148.4, 147.7,
144.9, 138.4, 135.6, 129.5, 129.4, 128.5, 128.0, 127.2, 126.6, 125.1,
122.8, 120.4, 45.9, 16.6 ppm.
[6] a) H. Nishiyama, A. Furuta, Chem. Commun. 2007, 760–762;
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(E)-4a:[18b] 1H NMR (400 MHz, CDCl3): δ = 7.25–7.22 (m, 5 H),
7.19–7.16 (m, 4 H), 7.11–7.08 (m, 2 H), 7.01 (d, J = 7.6 Hz, 4 H),
6.36 (d, J = 10.8 Hz, 1 H), 4.69 (d, J = 10.8 Hz, 1 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 143.3, 136.8, 131.5, 131.4, 128.9,
128.6, 128.3, 128.3, 128.1, 126.6, 50.7 ppm.
1
(E)-4b: H NMR (400 MHz, CDCl3): δ = 7.23–7.21 (m, 5 H), 7.15
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Received: September 7, 2009
Published Online: November 9, 2009
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5586–5587, and references cited therein.
Eur. J. Org. Chem. 2010, 565–571
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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