Cu(acac)2-catalyzed synthesis of functionalized bis(arylmethyl)zinc reagents and their olefination reaction with aromatic aldehydes

Article abstract of DOI:10.1055/s-0031-1289723

An efficient and facile copper(II) acetylacetonate catalyzed synthesis of functionalized bis(arylmethyl)zinc reagents from arylmethyl halides and their olefination reaction with aromatic aldehydes is reported. Aluminum trichloride was found to be the key ingredient in these reactions and (E)-stilbenes were obtained in high yields. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0031-1289723

1030
PAPER
Cu(acac)2-Catalyzed Synthesis of Functionalized Bis(arylmethyl)zinc
Reagents and Their Olefination Reaction with Aromatic Aldehydes
Synthesis of
(
E
)-S
i
tilbenesng Fu,* Xuemei Hu, Yaojuan Chen, Yanshou Yang, Hongxia Hou, Yulai Hu
College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. of China
Fax +86(931)7768159; E-mail: fuying@iccas.ac.cn
Received 17 December 2011; revised 23 January 2012
Transmetalation of organolithium or organomagnesium
reagents with zinc halides is a practical method for the
synthesis of organozinc reagent.8 In order to minimize
formation of the coupling byproduct and functionalize the
Abstract: An efficient and facile copper(II) acetylacetonate cata-
lyzed synthesis of functionalized bis(arylmethyl)zinc reagents from
arylmethyl halides and their olefination reaction with aromatic alde-
hydes is reported. Aluminum trichloride was found to be the key in-
gredient in these reactions and (E)-stilbenes were obtained in high organometallic reagent, an in situ preparation of orga-
yields.
nozinc halide or diorganozinc reagents by reaction of
magnesium metal with organic halides in the presence of
lithium chloride and zinc chloride was recently explored
by the Knochel group and they found that the reactivity of
organozinc reagents can be dramatically enhanced by
magnesium chloride in situ in these reaction systems.9 A
similar effect was also observed by Ellman et al. in the re-
action of arylmethylzinc reagents with N-tert-butanesulfi-
nyl aldimines.10 Encouraged by these findings, we here
report a convenient one-pot, in situ preparation of
bis(arylmethyl)zinc reagents by reaction of magnesium
metal with arylmethyl halides in the presence of zinc ha-
lide (0.5 equiv) and copper(II) acetylacetonate (0.1
equiv), and their olefination reaction with aromatic alde-
hydes (Scheme 1).
Key words: aldehyde, zinc, nucleophilic addition, olefination, ben-
zylation
Organozinc reagents, due to their great compatibility with
a variety of functional groups such as halide, amide, ether,
ester, nitrile, or even formyl groups, have become of in-
creasing importance as selective synthetic tools for C–C
bond formation.1 Previously, we reported an interesting
olefination reaction whereby arylaldehydes were reacted
with arylmethylzinc halides under transition-metal-com-
plex catalysis in the presence of trimethylsilyl chloride to
give trans-stilbene derivatives only.2 This protocol pro-
vides another facile approach to trans-styrenes besides the
well-known Wittig reaction. The obvious advantage of
this method is its stereospecificity as only trans-styrenes
were obtained, whereas the Wittig protocol always gives
both cis- and trans-isomers. However, these reactions
have some limitations as these organometallic reagents
are very sensitive to moisture, which must be excluded
from the reaction system. Moreover, the nucleophilicity
of some arylmethylzinc halides means that they are too
weak to react efficiently with the carbonyl group.
Mg (1.2 equiv)
ZnX2 (0.5 equiv)
Cu(acac)2 (0.1 equiv)
THF, 2–8 h
X
Zn·MgX2
2
up to 95%
Ar
Ar
1a Ar = Ph
1b Ar = 4-ClC6H4
1c Ar = 4-FC6H4
1d Ar = 4-BrC6H4
1e Ar = 4-MeOC6H4
1f Ar = 3,4,5-(MeO)3C6H2
1g Ar = 2-naphthyl
1h Ar = 4-PhC6H4
Diorganozincs (R2Zn) are significantly more reactive than
organozinc halides (RZnX) towards various electrophilic
reagents.3 However, even though diorganozinc reagents
were among the first prepared and practically used orga-
nometallic reagent,4 they are not so widely used in organic
synthesis as organolithium reagents, organomagnesium
reagents, or even their organozinc sibling, organozinc ha-
lides. Diorganozinc reagents, with the exception of a few
commercially obtained examples with simple structures,
such as dimethylzinc, diethylzinc, or diphenylzinc re-
agents, are not readily available, they are prepared by
iodine–zinc exchange,5 boron–zinc exchange,6 or hy-
drozincation reaction.7
Scheme 1 Synthesis of functionalized bis(arylmethyl)zinc–magne-
sium halide complexes
Reaction of magnesium turnings (1.2 equiv) with aryl-
methyl chloride or arylmethyl bromide in the presence of
zinc chloride (0.5 equiv), and copper(II) acetylacetonate
(0.1 equiv) in tetrahydrofuran was shown to be a mild and
efficient method for the preparation of bis(arylmeth-
yl)zinc reagents 1 in our laboratory (Scheme 1). The addi-
tion of copper(II) acetylacetonate to these reaction
systems produced a significant enhancement and, in most
cases, arylmethyl chlorides can be converted into the cor-
responding bis(arylmethyl)zinc reagents 1 in 2–8 hours in
an ice-water bath. Arylmethyl bromides can be best con-
verted into bis(arylmethyl)zinc reagents 1 by stirring the
mixture in a salt-ice bath for 2–6 hours. Quenching the or-
SYNTHESIS 2012, 44, 1030–1036
x
x.
x
x.
2
0
1
2
Advanced online publication: 24.02.2012
DOI: 10.1055/s-0031-1289723; Art ID: H115811SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Synthesis of (E)-Stilbenes
1031
ganozinc reagents 1 immediately after their preparation tion conditions give (E)-stilbenes stereospecifically in
with methanol showed that the formation of the homocou- satisfactory yields.2
pling product bibenzyls can be controlled to less than 7%
The Lewis acid aluminum trichloride has been reported to
for benzyl chlorides and no more than 10% for benzyl bro-
be an efficient catalyst for the olefination reaction of ben-
mides. Other copper(I) or copper(II) salts or complexes,
zylzinc halides with aldehyde and ketones.12 We thus
such as copper sulfate, copper(II) chloride, copper(I) io-
turned our attention to the role of Lewis acids on the reac-
tion of dibenzylzinc reagent 1a with aldehyde 2a and, to
our delight, aluminum trichloride showed a significant ef-
dide, copper(I) cyanide, and copper(II) acetate, were all
effective reagents, but copper(II) acetylacetonate was
shown to be the best as it generally gave the lowest yield
fect on the reaction. Addition of three equivalents of alu-
of coupling byproduct, 1,2-diarylethane.
minum trichloride did not show any effect on the reaction
The role of copper complexes here may be that of an ac- at room temperature (entry 7). However, an increase in the
tive ‘zinc–copper couple’ layer formed on the surface of reaction temperature to 60 °C and stirring the reaction
the magnesium turnings via in situ reduction of zinc chlo- mixture in tetrahydrofuran for eight hours resulted in the
ride and copper complex by magnesium metal, which will formation of the stilbene 3a and the alcohol 4a in a 3:1 ra-
1
react readily with the arylmethyl halide to form bis(aryl- tio based on H NMR spectrum analysis (entry 8). Inter-
methyl)zinc reagents 1, including highly functionalized estingly, when the reaction was performed in 1,4-dioxane
examples. Although the noncatalytic procedure is a sim- at 80 °C for eight hours in the presence of three equiva-
ple and efficient synthetic method,8c where bis(arylmeth- lents of aluminum trichloride, the alcohol was completely
yl)zinc reagents 1 are generated simply by addition of two consumed and only trans-stilbene 3a was obtained in 84%
equivalents of arylmethylmagnesium halides to zinc bro- isolated yield with no detected cis-stilbene (entry 9). The
mide, the high reactivity of Grignard reagents means that olefination reaction could not be improved by further in-
more fragile functional groups cannot be retained in these creasing the amount of aluminum trichloride to five
organometallics. Another advantage of our catalytic pro- equivalents as the yield of stilbene 3a was lowered (entry
cedure is that some of the more reactive arylmethyl ha- 10). Other Lewis acids such as cerium(III) chloride, lithi-
lides, especially those with electron-donating substituents um chloride, iron(III) chloride, and magnesium chloride
on the aryl ring (methoxy, etc.) could be successfully gave 4a only (entries 11–14). In the presence of two
transformed into corresponding bis(arylmethyl)zinc re- equivalents of tin(IV) chloride or titanium(IV) chloride or
agents 1 in high yields whereas using the noncatalytic pro- three equivalents of zinc chloride, the reaction did not oc-
cedures, the synthesis of arylmethyl Grignard reagents cur (entries 15–17). Boron trifluoride–diethyl ether com-
itself would be accompanied by the formation of a consid- plex can be used to form 3a in 56% yield after stirring the
erable amount of homocoupling product11 and the result- reaction mixture under the same conditions (entry 18).
ing magnesium reagent would decomposes rapidly in the
To determine whether the both benzyl groups from the
dibenzylzinc reagent 1a could be transferred, two equiva-
lents of aldehyde 2a were introduced into the reaction sys-
absence of zinc(II) chloride.9c Thus they were normally
used in excess in the formulated synthetic procedure.
With the desired bis(arylmethyl)zinc reagents 1 in hand, tem. However, after stirring at 80 °C for 12 hours, only
we began to examine their reaction with arylaldehydes 2. half of the aldehyde had been consumed and stilbene 4a
Initially, the reaction of dibenzylzinc reagent 1a with p- was obtained in 82% isolated yield based on the recovered
anisaldehyde (2a) in tetrahydrofuran was investigated as aldehyde (entry 19).
a model system to identify whether stilbene 3a or an alco-
hol product 4a would be formed. As expected no reaction
occurred without the addition of a catalytic additive, indi-
cating that organozinc reagents had indeed been effective-
ly formed as the corresponding Grignard reagent would be
expected to react with carbonyl compounds easily without
the use of a catalyst (Table 1, entry 1). In the presence of
two equivalents of trimethylsilyl chloride, only alcohol 4a
Based on the control experiment given in Table 1, entry 9,
the reaction of substituted arylaldehydes 2 and bis(aryl-
methyl)zinc reagents 1a–h was performed in the presence
of three equivalents of aluminum trichloride (Table 2).
Reaction of dibenzylzinc reagent 1a with various substi-
tuted arylaldehydes 2 bearing electron-withdrawing
groups and electron-donating groups present in the para
or meta positions all proceeded smoothly and consistently
was obtained in 84% isolated yield and stilbene 3a was
gave the corresponding stilbenes 3b–i in good to high
not detected (entry 2). Addition of transition-metal com-
yield (entries 2–10). However, ortho-substituted benzal-
dehydes did not react cleanly and gave the corresponding
stilbene 3k in low yield (entry 12).
plexes such as Ni(PPh3)2Cl2, Ni(PPh3)4 Pd(PPh3)2Cl2, and
Pd(PPh3)4 together with two equivalents of TMSCl to the
reaction of 1a with 2a did not induce the formation of the
desired (E)-stilbene 3a, and the alcohol 4a was again ob-
tained (entries 3–6). Reaction of 1a with aldehyde 2a in
the presence of trimethylsilyl chloride and transition-met-
al complexes gave only the alcohol product 4a indicating
that the reactivity of dibenzylzinc reagent 1a is quite dif-
Interestingly, hydroxy-substituted benzaldehydes can be
used directly but an extra equivalent of bis(arylmeth-
yl)zinc halide 1a,b was added as the acidic hydroxy group
must first be neutralized by the bis(arylmethyl)zinc re-
agent.13 The resulting formyl phenolate then reacted with
bis(arylmethyl)zinc reagent to give the hydroxylated stil-
benes 3e and 3p in moderate yields (entries 5 and 17). Ac-
ferent to benzylzinc halides, which under the same reac-
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1030–1036

1032
Y. Fu et al.
PAPER
etoxy-substituted benzaldehydes were sensitive to the tries 13–19) or electron-donating substituents (methoxy,
reaction condition and the product was deacetylated to benzyloxy, or phenyl groups, entries 20–23) on the phenyl
give the hydroxystilbene 3e (entry 6). The nitro group in ring all reacted efficiently with arylaldehydes 2 to give the
4-nitrobenzaldehyde was reduced to hydroxylamine with corresponding stilbenes 3l–s in moderate to high yields,
4-(hydroxylamino)stilbene (3c) isolated in 58% yield (en- which shows that both types of substituents are well toler-
try 3).
ated. Some fragile substituents such as cyano and ester
groups were not retained in these reactions, although the
corresponding functionalized bis(arylmethyl)zinc re-
agents themselves can be successfully obtained.9
Next, we screened the reaction by varying the substituent
on the aromatic ring of the bis(arylmethyl)zinc reagents 1.
Bis(arylmethyl)zinc reagents bearing either electron-
withdrawing substituents (chloro, bromo, or fluoro, en-
Table 1 Conditions for the Reaction of Dibenzylzinc Reagent 1a with p-Anisaldehyde (2a)a
Ph
Ph
CHO
HO
Bn2Zn⋅MgX2 1a
+
catalyst
OMe
OMe
3a
OMe
4a
2a
Entry
Temp (°C)
Time (h)
Additive (equiv)
Solvent
THF
Productb
Yieldc (%)
1
2
3
0–20
0–20
0–20
8
8
8
–
–
–
TMSCl (2)
THF
4a
4a
84
86
TMSCl (2)
THF
Ni(PPh3)2Cl2 (0.5)
4
5
6
0–20
0–20
0–20
8
8
8
TMSCl (2)
Ni(PPh3)4 (0.5)
THF
THF
THF
4a
4a
4a
82
83
82
TMSCl (2)
Pd(PPh3)2Cl2 (0.3)
TMSCl (2)
Pd(PPh3)4 (0.3)
7
8
0–20
60
80
80
80
80
80
80
80
80
80
80
80
8
8
8
8
8
8
8
8
8
8
8
8
8
AlCl3 (3)
AlCl3 (3)
AlCl3 (3)
AlCl3 (5)
CeCl3 (3)
LiCl (3)
THF
–
–
THF
3a/4a (3:1)
86
84
65
32
67
23
54
–
9
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
3a
3a
4a
4a
4a
4a
–
10
11
12
13
14
15
16
17
18
19
FeCl3 (3)
MgCl2 (3)
ZnCl2 (3)
SnCl4 (2)
TiCl4 (2)
BF3·OEt2 (3)
AlCl3 (3)
–
–
–
–
3a
3a
56
82d
a Reaction conditions: aldehyde 1a (1.0 mmol), Bn2Zn (2a, 1.2 mmol), additive [Lewis acid], solvent (10 mL), under N2, 8 h.
b Detected by 1H NMR.
c Isolated yields.
d Aldehyde 2a (2 equiv) was used.
Synthesis 2012, 44, 1030–1036
© Thieme Stuttgart · New York

PAPER
Synthesis of (E)-Stilbenes
1033
Attempts to expand the substrates to ketones were unsuc-
cessful as the products of these reactions were mainly al-
cohols. Heterocyclic aldehydes such as furfural and
thiophene-2-carbaldehyde gave very low yields of olefin
products, probably because these heterocycles are fragile
under these reaction conditions.
Table 2 Reaction of Bis(arylmethyl)zinc Reagents 1a–h with Alde-
hydes 2a
Zn·MgX2
2
AlCl3, 1,4-dioxane, 80 °C
R
R
CHO
+
Ar
Ar
1a–h
2
3
In summary, we have developed a practical and facile pro-
cedure for the synthetic utilization of functionalized
bis(arylmethyl)zinc reagents, which, as functionalized or-
ganometallic reagents, were efficiently utilized in reac-
tions with arylaldehydes in a C=C bond-forming reaction.
Copper(II) acetylacetonate was found to be an efficient
catalyst in the synthesis of the functionalized bis(aryl-
methyl)zinc reagents and aluminum trichloride was
shown to be the key Lewis acid in the promotion of these
reactions. In most cases, (E)-stilbenes were stereoselec-
tively formed in high yields.
Entry Ar
R
Product Yieldb
(%)
1
2
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4-MeOC6H4
Ph
3a
3b
3cc
3d
3e
3ee
3f
84
86
58
83
76d
62e
82
78
81
80
72
36
75
86
84
81
55d
76
85
62
76
65
78
3
4-O2NC6H4
4
3,4,5-(MeO)3C6H2
3-MeO-4-HOC6H3
3-MeO-4-AcOC6H3
3-MeO-4-BnOC6H3
3,4-(MeO)2C6H3
4-BnOC6H4
5
6
7
All chemicals were obtained from commercial sources. Melting
points were measured on an X-4 electrothermal micro melting point
apparatus and are uncorrected. IR spectra were measured using an
Alpha Centauri FT-IR spectrophotometer. 1H and 13C NMR spectra
(400 MHz and 100 MHz, respectively) were recorded on Bruker
AC-E 400 MHz spectrometer in CDCl3 with TMS as an internal
standard. Mass spectra were performed on QP-1000A GCMS spec-
trometer by EI ionization at 70 eV. Purification of products was per-
formed by flash chromatography on 300–400 mesh silica gel
(petroleum ether–EtOAc).
8
3g
3h
3i
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
4-PhC6H4
CH=CHPh
3j
2-MeOC6H4
4-MeOC6H4
4-MeO-3-BnOC6H3
3-MeO-4-BnOC6H3
3,4,5-(MeO)3C6H2
3-MeO-4-HOC6H3
4-ClC6H4
3k
3l
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-FC6H4
Dibenzylzinc–Magnesium Halide Complex 1a; Typical Proce-
dure
3m
3n
3o
3p
3q
3r
3b
3d
3s
Cut Mg foil (0.36 g, 15 mmol) and ZnCl2 (0.82 g, 6.0 mmol) were
added to a dry, three-necked flask equipped with an argon inlet, a
thermometer, and an addition funnel. The system was flushed and
maintained under argon or N2 atmosphere, 1,2-dibromoethane (0.1
mL) in THF (5 mL) was added, and the mixture was heated to 65 °C
for 10 min. The mixture was then cooled to 0–5 °C (ice–water bath),
a solution of Cu(acac)2 (0.32 g, 1.2 mmol) in THF (2 mL) was add-
ed, and then a soln of BnCl (1.52 g, 12.0 mmol) in THF (15 mL) was
added dropwise (for BnBr, the reaction was conducted in an ice-salt
bath). The mixture was stirred and the temperature was allowed to
rise to r.t. until GLC analysis showed that the starting material was
completely consumed (2–8 h).
4-BrC6H4
Ph
4-MeOC6H4
Ph
3,4,5-(MeO)3C6H2 Ph
2-naphthyl
4-PhC6H4
4-MeOC6H4
Ph
1,2-Diarylethenes 3;General Procedure
Bis(arylmethyl)zinc 1 prepared as above (5.0 mL, about 1.2 mmol)
was added to a soln of arylaldehyde 2 (1.0 mmol) and AlCl3 (0.4 g,
3.0 mmol) in 1,4-dioxane (10 mL). The mixture was heated to 80 °C
and stirred at this temperature for 8 h. The mixture was allowed to
cool to r.t. and the reaction was quenched with aq NH4Cl (10 mL).
EtOAc (10 mL) was added and the organic phase was separated,
washed with H2O (10 mL) and then with brine (10 mL). The aque-
ous phase was extracted with EtOAc (2 × 10 mL). The combined
organic phases were dried (Na2SO4) and concentrated under re-
duced pressure. (E)-Stilbenes 3 were obtained by column chroma-
tography (silica gel, petroleum ether–EtOAc). All products were
characterized by IR and 1H and 13C NMR.
3i
a Reaction conditions: RCHO 2 (1.0 mmol), Ar2Zn 1 (1.2 mmol),
AlCl3 (3.0 equiv), 1,4-dioxane (10 mL), 80 °C.
b Isolated yield.
c Nitro was reduced to hydroxylamine.
d Ar2Zn (2.2 mmol) was used.
e The acetoxy group was cleaved.
The reaction of cinnamaldehyde with dibenzylzinc re-
agent 1a produced (1E,3E)-1,4-diphenylbuta-1,3-diene
(3j) in 72% yield (entry 11) indicating that the unsaturated
double bond in the aromatic aldehyde could be retained
(E)-4-Methoxystilbene (3a)
and directly introduced into the product. This protocol White solid; yield: 175 mg (84%); mp 137–139 °C (Lit.14 135–137
°C).
could be a good method for the synthesis of conjugated
polyenes, which have a plethora of applications in both or-
ganic and biological chemistry.
IR (KBr): 1600, 1510, 1296, 1248, 1176, 1072 cm–1.
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1030–1036

1034
Y. Fu et al.
PAPER
1H NMR (400 MHz, CDCl3): d = 3.83 (s, 3 H, OCH3), 6.90 (dt,
J = 11.2, 2.8 Hz, 2 H, ArH), 6.97 (d, J = 16.4 Hz, 1 H, =CH), 7.07
(d, J = 16.4 Hz, 1 H, =CH), 7.23 (t, J = 7.2 Hz, 1 H, ArH), 7.34 (t,
J = 7.6 Hz, 2 H, ArH), 7.45 (dt, J = 11.2, 2.8 Hz, 2 H, ArH), 7.49
(br d, J = 8.0 Hz, 2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 55.3, 114.2, 126.4, 127.3, 127.4,
127.8, 129.8, 135.2, 139.9, 159.9.
Anal. Calcd for C22H20O2: C, 83.51; H, 6.37; Found: C, 83.27; H,
6.52.
(E)-3,4-Dimethoxystilbene (3g)
White solid; yield: 186 mg (78%); mp 128–130 °C (Lit.16 129–130
°C).
IR (KBr): 1630, 1515, 1485, 1459, 1073, 963 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.95 (s, 3 H, OCH3), 3.90 (s, 3 H,
OCH3), 6.88 (t, J = 8.6 Hz, 1 H, ArH), 7.03 (q, J = 8.8 Hz, 4 H,
ArH), 7.25 (t, J = 3.6 Hz, 1 H, ArH), 7.35 (tt, J = 7.2, 1.6 Hz, 2 H,
ArH), 7.50 (dt, J = 9.6, 1.6Hz, 2 H, ArH).
(E)-Stilbene (3b)
White solid; yield: 155 mg (86%); mp 124–126 °C (Lit.15 124.5 °C).
IR (KBr): 1635, 1493, 1448, 1138, 1027, 962 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.15 (s, 2 H, =CH), 7.25–7.43 (m,
6 H, ArH), 7.55 (d, J = 8 Hz, 4 H, ArH).
13C NMR (100 MHz, CDCl3): d = 55.8, 55.9, 108.7, 111.2, 119.8,
126.3, 126.8, 127.3, 128.4, 128.6, 130.4, 137.5, 148.9, 149.1.
13C NMR (100 MHz, CDCl3): d = 126.4, 127.4, 128.0, 128.7, 135.2.
(E)-4-(Benzyloxy)stilbene (3h)
White solid; yield: 230 mg (81%); mp 169–172 °C (Lit.2c 168–170
°C).
(E)-N-(4-Styrylphenyl)hydroxylamine (3c)
Pale yellow solid; yield: 120 mg (58%); mp 150–152 °C.
IR (KBr): 1602, 1508, 1449, 1246, 1074, 964 cm–1.
1H NMR (400 MHz, CDCl3): d = 5.09 (s, 2 H), 7.0–6.91 (m, 4 H,
ArH), 7.06 (d, J = 16.4 Hz, 2 H, =CH), 7.51–7.22 (m, 10 H, ArH).
13C NMR (100 MHz, CDCl3): d = 70.0, 115.1, 126.7, 127.2, 127.4,
127.0, 128.0, 128.1, 128.5, 128.6, 128.6, 130.4, 136.9, 137.6,
155.4.
IR (KBr): 3398, 1605, 1514, 1458, 1247, 1179, 1122, 1074, 1026,
963 cm–1.
1H NMR (400 MHz, CDCl3): d = 4.15 (br s, 1 H, OH), 4.37 (s, 1 H,
NH), 6.63 (d, J = 8.6 Hz, 2 H, ArH), 6.90 (d, J = 16.3 Hz, 1 H,
ArH), 7.02 (d, J = 16.3Hz, 1 H, ArH), 7.19 (t, J = 7.2 Hz, 1 H, ArH),
7.26–7.34 (m, 4 H, ArH), 7.47 (d, J = 7.2 Hz, 2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 116.5, 124.2, 126.4, 127.4, 128.0,
(E)-4-Styrylbiphenyl (3i)
128.7, 128.9, 135.2, 150.0.
White solid;18 yield: 205 mg (80%); mp 126–128 °C.
MS (EI, 70 eV): m/z = 212.3 [M + H]+.
IR (KBr): 3024, 1486, 1446, 165, 1073, 966 cm–1.
(E)-3,4,5-Trimethoxystilbene (3d)
1H NMR (400 MHz, CDCl3): d = 7.15 (s, 2 H, =CH), 7.22 (t, J = 8.2
Hz, 2 H, ArH), 7.36 (m, J = 7.6 Hz, 3 H, ArH), 7.45 (t, J = 7.6 Hz,
2 H, ArH), 7.54 (d, J = 8.2 Hz, 2 H, ArH), 7.61 (t, J = 5.4 Hz, 5 H,
ArH).
13C NMR (100Hz, CDCl3): d = 126.5, 127.1, 127.3, 127.6, 128.2,
128.7, 128.8, 136.5, 137.3, 140.3, 140.6.
White solid; yield: 225 mg (83%); mp 108–110 °C (Lit.16 109–110
°C).
IR (KBr): 1633, 1506, 1417, 1188, 1130, 987 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.87 (s, 3 H, OCH3), 3.92 (s, 6 H,
OCH3), 6.75 (s, 2 H, ArH), 7.03 (d, J = 2.8 Hz, 2 H, =CH), 7.26 (tt,
J = 7.6, 1.2 Hz, 1 H, ArH), 7.36 (t, J = 7.6 Hz, 2 H, ArH), 7.50 (d,
J = 0.7 Hz, 1 H, ArH), 7.52 (d, J = 1.4 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): d = 56.1, 60.9, 103.4, 126.4, 127.5,
128.1, 128.6, 128.6, 133.0, 137.1, 137.8, 153.3.
(1E,3E)-1,4-Diphenylbuta-1,3-diene (3j)
White solid; yield: 148 mg (72%); mp 148–151 °C (Lit.14 151 °C).
IR (KBr): 1636, 1537, 1487, 1173, 1071, 991, 911 cm–1.
1H NMR (400 MHz, CDCl3): d = 6.68 (ddd, J = 18.8, 8.4, 2.8 Hz, 2
H, =CH), 6.98 (ddd, J = 18.8, 8.8, 2.9 Hz, 2 H, =CH), 7.48–7.43 (dt,
J = 8.6, 1.8 Hz, 4 H, ArH), 7.34 (tt, J = 7.0, 1.4 Hz, 4 H, ArH), 7.28–
7.42 (m, 2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 126.3, 127.5, 128.6, 129.2, 132.8,
137.3.
(E)-3-Methoxy-4-hydroxystilbene (3e)
White solid; yield: 170 mg (76%); mp 134–136 °C (Lit.17 138 °C).
IR (KBr): 2945, 1593, 1551, 1465, 1073, 963 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.94 (s, 3 H, OCH3), 5.67 (br s, 1
H, OH), 6.88–7.09 (m, 5 H, ArH), 7.24 (tt, J = 7.2, 1.4 Hz, 1 H,
ArH), 7.32 (tt, J = 8.0, 2.2 Hz, 2 H, =CH), 7.50 (dt, J = 7.0, 1.6 Hz,
2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 56.0, 109.3, 116.8, 120.4, 125.4,
127.4, 127.9, 128.7, 128.8, 130.8, 135.0, 144.8, 151.3.
(E)-2-Methoxystilbene (3k)
White solid; yield: 75 mg (36%); mp 56–58 °C (Lit.16 56–57 °C).
IR (KBr): 1600, 1591, 1483, 1466, 1030, 965 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.96 (s, 3 H, OCH3), 6.93 (d,
J = 8.0 Hz, 2 H, ArH), 7.08 (d, J = 16.6 Hz, 2 H, =CH), 7.29–7.18
(m, 2 H, ArH), 7.21 (tt, J = 7.2, 1.6Hz, 2 H, ArH), 7.49–7.61 (m, 3
H, ArH).
13C NMR (100 MHz, CDCl3): d = 55.5, 110.9, 120.7, 123.5, 126.4,
126.4, 126.5, 127.3, 128.5, 128.6, 129.1, 137.9, 156.9.
(E)-4-(Benzyloxy)-3-methoxystilbene (3f)
White solid; yield: 258 mg (82%); mp 114–116 °C.
IR (KBr): 1600, 1509, 1460, 1418, 1218, 958 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.95 (s, 3 H, OCH3), 5.19 (s, 2 H,
OCH2), 6.85 (d, J = 8.3 Hz, 1 H, ArH), 6.94–6.99 (m, 2 H, ArH),
7.03 (d, J = 1.7 Hz, 1 H, =CH), 7.24 (d, J = 1.7 Hz, 1 H, =CH), 7.30
(t, J = 8.2 Hz, 1 H, ArH), 7.36 (t, J = 8.3 Hz, 4 H, ArH), 7.46 (dd,
J = 17.0, 7.6 Hz, 5 H, ArH).
13C NMR (100 MHz, CDCl3): d = 55.9, 67.3, 109.3, 113.9, 119.7,
126.2, 126.9, 127.3, 127.5, 127.8, 128.2, 128.5, 128.6, 130.8, 136.9,
137.4, 147.9, 149.7.
(E)-4-Chloro-4¢-methoxystilbene (3l)
White blocks; yield: 185 mg (75%); mp 182–185 °C (Lit.19 184 °C).
IR (KBr): 2960, 1604, 1574, 1176, 969 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.81 (s, 3 H, OCH3), 6.93 (d,
J = 8.0 Hz, 2 H, ArH), 6.92 (d, J = 16.4 Hz, 1 H, =CH), 7.12 (d,
J = 16.4 Hz, 1 H, =CH), 7.25–7.32 (m, 3 H, ArH), 7.35–7.48 (m, 3
H, ArH).
MS (EI, 70 eV): m/z = 317.4 [M + H]+.
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Synthesis of (E)-Stilbenes
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13C NMR (100 MHz, CDCl3): d = 55.3, 114.2, 125.3, 127.4, 127.7,
IR (KBr): 3029, 1601, 1576, 1510, 1496, 1448 cm–1.
128.8, 128.8, 129.8, 132.7, 136.2, 159.5.
1H NMR (400 MHz, CDCl3): d = 6.85 (d, J = 16.0 Hz, 1 H, =CH),
7.04 (d, J = 16.0 Hz, 1 H, =CH), 7.06–7.10 (m, 2 H, ArH), 7.32 (d,
J = 8.4 Hz, 2 H), 7.42 (d, J = 8.4 Hz, 2 H), 7.47 (dd, J = 8.4, 5.6 Hz,
2 H, ArH).
(E)-3-(Benzyloxy)-4¢-chloro-4-methoxystilbene (3m)
White solid; yield: 300 mg (86%); mp 128 °C.
IR (KBr): 3028, 2933, 1635, 1599, 1512, 1489, 1383, 1249, 1161,
958 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.90 (s, 3 H, OCH3), 5.20 (s, 2 H,
OCH2), 6.81–6.99 (m, 3 H, ArH), 7.07 (dt, J = 4.0, 1.9 Hz, 2 H,
=CH), 7.26–7.41 (m, 7 H, ArH), 7.45 (d, J = 7.6 Hz, 2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 56.0, 71.1, 111.7, 120.4, 125.4,
127.3, 127.4, 127.9, 128.6, 128.7, 128.8, 128.9, 130.0, 132.7, 135.9,
137.0, 148.3, 149.8.
13C NMR (100 MHz, CDCl3): d = 115.7 (J = 21.5 Hz), 127.1,
127.6, 128.0, 128.1, 128.9, 130.7, 133.1, 136.6, 162.4 (J = 246.2
Hz).
19F NMR (376.5 MHz, CDCl3): d = –114.2.
MS (EI, 70 eV): m/z = 233.7 [M + H]+.
Anal. Calcd for C14H10ClF: C, 72.27; H, 4.33. Found: C, 72.12; H,
4.42.
MS (EI, 70 eV): m/z = 351.9 [M + H]+.
(E)-4-Bromostilbene (3r)
Anal. Calcd for C22H19ClO2: C, 75.32; H, 5.46; Found: C, 75.21; H,
5.52.
White solid; yield: 220 mg (85%); mp 136–138 °C (Lit.20 140 °C).
IR (KBr): 1599, 1587, 1575, 1493, 1485, 1447 cm–1.
1H NMR (400 MHz, CDCl3): d = 6.49 (d, J = 16.0 Hz, 1 H, =CH),
6.63 (d, J = 16.0 Hz, 1 H, =CH), 7.08–7.35 (m, 9 H, ArH).
13C NMR (100 MHz, CDCl3): d = 120.9, 127.3, 128.3, 128.7, 128.9,
130.5, 130.9, 131.3, 136.0, 136.8.
(E)-4-(Benzyloxy)-4¢-chloro-3-methoxystilbene (3n)
White solid; yield: 283 mg (84%); mp 186–190 °C.
IR (KBr): 3013, 1631, 1597, 1512, 1463, 1415, 1383, 1348, 1309,
1269, 1250, 1226, 1138, 957 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.95 (s, 3 H, OCH3), 5.19 (s, 2 H,
(E)-2-(4-Methoxystyryl)naphthalene (3s)
White solid; yield: 202 mg (65%); mp 171–173 °C.
IR (KBr): 3445, 1629, 1595, 1273, 1121, 958 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.18 (s, 3 H, OCH3), 7.36 (dd,
J = 8.0, 4.0 Hz, 2 H, ArH), 7.40–7.50 (m, 4 H), 7.66 (s, 1 H, ArH),
7.75–7.95 (m, 6 H).
OCH2), 6.85–7.32 (m, 5 H, ArH), 7.29–7.45 (m, 9 H, ArH).
13C NMR (100 MHz, CDCl3): d = 56.0, 70.9, 109.3, 113.9, 119.8,
125.6, 127.2, 127.4, 127.9, 128.6, 128.8, 129.0, 130.5, 132.8 136.0,
136.9, 148.1, 149.7.
MS (EI, 70 eV): m/z = 351.9 [M + H]+.
Anal. Calcd for C22H19ClO2: C, 75.32; H, 5.46; Found: C, 75.18; H,
5.48.
13C NMR (100 MHz, CDCl3): d = 38.0, 125.2, 125.9, 126.6, 127.3,
127.5, 127.6, 127.9, 132.0, 133.6, 139.2.
MS (EI, 70 eV): m/z = 261.3 [M + H]+.
(E)-4¢-Chloro-3,4,5-trimethoxystilbene (3o)
White solid; yield: 246 mg (81%); mp 174–176 °C.
Anal. Calcd for C19H16O: C, 87.66; H, 6.19. Found: C, 87.74; H,
6.32.
IR (KBr): 1637, 1504, 1419, 1236, 1088, 973 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.87 (s, 3 H, OCH3), 3.92 (s, 6 H,
OCH3), 6.73 (s, 2 H, ArH), 6.98 (dd, J = 16.4, 9.2 Hz, 2 H, =CH),
7.32 (d, J = 8.8 Hz, 2 H, ArH), 7.43 (d, J = 8.8 Hz, 2 H, ArH).
13C NMR (100 MHz, CDCl3): d = 56.1, 60.9, 103.5, 126.8, 127.5,
128.8, 129.2, 132.7, 133.1, 135.7, 138.0, 153.4.
Acknowledgment
The authors are grateful for financial support from National Natural
Science Foundation of China (No. 20962017), the Natural Science
Foundation of Gansu Province, China (No. 1107RJZA263) and Key
Laboratory of Eco-Environment-Related Polymer Materials of
Ministry of Education, and Key laboratory Polymer Materials of
Gansu Province (Northwest Normal University).
MS (EI, 70 eV): m/z = 305.8 [M + H]+.
Anal. Calcd for C17H17ClO3: C, 67.00; H, 5.62; Found: C, 65.88; H,
5.80.
(E)-4¢-Chloro-4-hydroxy-3-methoxystilbene (3p)
Pale yellow solid; yield: 143 mg (55%); mp 165–167 °C.
References
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Z.; Marek, I., Eds.; John Wiley & Sons: Chichester, 2006.
(b) Knochel, P.; Jones, P. Organozinc Reagents, A Practical
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IR (KBr): 3216, 1593, 1514, 1489, 1451, 1427, 1370, 1277, 1260,
1208, 1156, 1122, 1098, 1026, 959 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.96 (s, 3 H, OCH3), 5.67 (s, 1 H,
OH), 6.87–6.92 (m, 2 H, =CH), 6.99–7.03 (m, 3 H, ArH), 7.31 (d,
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(E)-4-Chloro-4¢-fluorostilbene (3q)
White solid; yield: 176 mg (76%); mp 132–134 °C.
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