Styryl ether formation from benzyl alcohols under transition-metal-free basic DMSO conditions

Article abstract of DOI:10.1039/c4ob02358g

A phenol-catalyzed aerobic oxidative styryl ether formation method was developed with benzyl alcohol under basic DMSO. Styryl ether was obtained after 12 hours of heating at 60-80 °C where DMSO was involved in the reaction as the extra carbon source. Control experiments indicated that both phenol and DMSO are crucial for the success of the reaction. A variety of styryl ethers were prepared smoothly from benzyl alcohols in good to excellent yields in an environmentally friendly way. This journal is

Full text of DOI:10.1039/c4ob02358g

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Styryl ether formation from benzyl alcohols under
transition-metal-free basic DMSO conditions†
Cite this: DOI: 10.1039/c4ob02358g
Kai Yang and Qiuling Song*
A phenol-catalyzed aerobic oxidative styryl ether formation method was developed with benzyl alcohol
under basic DMSO. Styryl ether was obtained after 12 hours of heating at 60–80 °C where DMSO was
involved in the reaction as the extra carbon source. Control experiments indicated that both phenol and
DMSO are crucial for the success of the reaction. A variety of styryl ethers were prepared smoothly from
benzyl alcohols in good to excellent yields in an environmentally friendly way.
Received 7th November 2014,
Accepted 2nd December 2014
DOI: 10.1039/c4ob02358g
www.rsc.org/obc
Environmentally benign reactions are desirable as people are Here we would like to report a mild, simple and efficient
paying more and more attention to environment protection. time-controlled method to obtain styryl ether from benzyl
Among the 12 principles of green chemistry,1–4 a metal-free, alcohol under transition-metal-free aerobic oxidative con-
multi-component tandem oxidative reaction with O2 as the ditions in basic DMSO.
oxidant involving common feedstock chemicals has a special
Recently we developed a Cu-catalyzed aerobic oxidative C–N
attraction due to its potential to be transformative. Benzyl triple bond formation method via the decarboxylation of phe-
alcohol is an important synthetic feedstock for a broad range nylacetic acids and urea (Scheme 1).20 On the basis of the
of functionalized, complex molecules. Among them, the selec- mechanism study and our recent related research, benz-
tive oxidation of benzyl alcohol into benzaldehyde is especially aldehydes are the key intermediates for this transformation. It is
attractive. Lately, significant progress has been made in well-known that benzyl alcohol can be easily oxidized into
tandem reactions based on the selective oxidation of benz- aldehydes at various oxidative conditions. Our interest in
aldehyde from benzyl alcohol.5–8 Although numerous methods copper-catalyzed aerobic oxidative tandem reaction prompted
have been developed for the oxidation of benzyl alcohols into us to apply our conditions on benzyl alcohol to see if the same
benzaldehydes in the presence of transition metals, practical product could be obtained. In order to promote the oxidation
and efficient methods with molecular oxygen as the oxidant in of benzyl alcohol under copper-catalyzed aerobic conditions,
the absence of transition metals are still highly desirable. The KOH was added. To our surprise, instead of benzonitrile, an
use of molecular oxygen as an oxidant has attracted consider- unexpected styryl ether was afforded in 31% yield as two
able attention owing to its abundance, low toxicity and envir- isomers (Scheme 2).
onmentally benign nature.9–14 Recently Li and He reported
This result astonished us. Further screening showed that
styryl ether formation from benzyl alcohol via Ag nanoparticle- copper salt and urea were unnecessary for this reaction
catalyzed tandem aerobic oxidation.15 A thorough mechanism (Table 1, entries 1–4). Interestingly, when phenol was added as a
study indicated that the Ag nanoparticle and oxygen are vital nucleophile, it was found to accelerate the reaction dramatically
for the reaction, and DMSO provides a carbon in the final
product.16 While good efficiencies and selectivities were
observed by Li and He, nanoparticles are notorious17–19 for
their irreproducibility because of their size-dependent reactiv-
ities. Significant research has been directed towards the devel-
Scheme 1 Synthesis of benzonitrile from copper-catalyzed aerobic
oxidative decarboxylation of phenylacetic acids and urea.
opment of metal-free oxidations because they are reproducible
and generate less waste to result in a greener process, and
tandem reaction which in situ traps the benzaldehyde from
benzyl alcohol to form the product is thus more attractive.
Institute of Next Generation Matter Transformation, College of Chemical
Engineering, Huaqiao University, 668 Jimei Blvd., Xiamen, Fujian, China.
E-mail: qsong@hqu.edu.cn; Fax: +86-592-6162990; Tel: +86-592-6162990
†Electronic supplementary information (ESI) available. See DOI: 10.1039/c4ob02358g
Scheme 2 Styryl ether formed from benzyl alcohol under basic DMSO.
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Table 1 Condition screeninga
Entry
Atmosphere
Additive
Base
Temp (°C)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
O2
O2
O2
O2
O2
O2
O2
O2
O2
O2
O2
Air
Air
Air
Air
Air
Air
Air
Air
N2
Urea
Urea
—
—
KOH (2 equiv.)
KOH (2 equiv.)
KOH (2 equiv.)
KOH (2 equiv.)
KOH (3 equiv.)
KOH (3 equiv.)
KOH (3 equiv.)
KOH (2.5 equiv.)
KOH (2 equiv.)
KOH (1.5 equiv.)
KOH (2.2 equiv.)
KOH (3 equiv.)
KOH (2.2 equiv.)
KOH (3 equiv.)
NaOH (2.2 equiv.)
Na2CO3 (2.2 equiv.)
KOBu-t (2.2 equiv.)
NEt3 (2.2 equiv.)
Pyridine (2.2 equiv.)
KOH (2.2 equiv.)
130
80
80
60
80
80
70
80
80
80
80
80
80
80
80
80
80
80
80
80
9
7
20
20
12
9
31 (2 : 3 = 4 : 1)
56
41
33
92 (2 : 3 = 5 : 1)
85
73
64
Phenol (1 equiv.)
Phenol (1 equiv.)
Phenol (1 equiv.)
Phenol (1 equiv.)
Phenol (1 equiv.)
Phenol (1 equiv.)
Phenol (20 mol%)
Phenol (1 equiv.)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
Phenol (20 mol%)
9
12
12
12
12
12
12
12
12
12
12
12
12
12
9
48
10
11
12
13
14
15
16
17
18
19
20
No product
83
91
92 (2 : 3 = 92 : 8)
88
90
No product
69
No product
No product
No product
a Reaction conditions: benzyl alcohol (0.5 mmol), base, DMSO (1 mL) under corresponding atmospheres.
Table 2 Styryl ether formed from benzyl alcohol catalyzed by various phenols
Entry
Oxidant
Additive
Base
Temp (°C)
Time (h)
Yield (%) (2 : 3)
1
2
3
4
5
Air
Air
Air
Air
Air
4-Me-phenol (20 mol%)
4-MeO-phenol (20 mol%)
4-F-phenol (20 mol%)
4-CF3-phenol (20 mol%)
Phenol (20 mol%)
KOH (2 equiv. + 20 mol%)
KOH (2 equiv. + 20 mol%)
KOH (2 equiv. + 20 mol%)
KOH (2 equiv. + 20 mol%)
KOH (2 equiv. + 20 mol%)
80
80
80
80
80
12
12
12
12
12
82 (88 : 12)
59 (79 : 21)
90 (89 : 11)
91 (91 : 9)
92 (92 : 8)
(Table 1, entry 5), which was quite rare and an unprecedented formation under transition-metal free condition emerged as:
example, and catalytic amounts of phenol could give the best benzyl alcohol (1 equiv.), phenol (20 mol%), KOH (2.2 equiv.),
result in terms of yield and the ratio of compounds 2 and 3 DMSO (1 mL) under air at 80 °C.
(Table 1, entry 13). In order to understand the role of phenol
Having found the optimized reaction conditions, we
in the reaction, various substituents on the aromatic ring of explored the scope of aromatic methyl alcohols (Scheme 3).
phenol were explored (Table 2). Both electron-donating and Both electron-rich and electron-poor aromatic methyl alcohols
electron-withdrawing groups worked well in this catalytic reac- converted into the desired products smoothly (Scheme 3, 2a–
tion, yet unsubstituted phenol gave the best result among 2j). The halo-substituted benzyl alcohol survived well leading
them with regard to the isolated yield and the ratio of com- to halo-substituted products (Scheme 3, 2b–2c), which could
pounds 2 and 3 (Table 2, entry 5).
be used for further transformation. Besides the halo-substi-
A base is very important for this reaction; both KOH and tuted ones, Me, i-Pr, phenyl, 1-naphthyl and t-Bu aromatic
NaOH gave good yields, other bases, such as Na2CO3, KOBu-t, methyl alcohols also worked well under the standard con-
NEt3 and pyridine gave poor or no yields (Table 1, entries ditions to give good yields of the desired products (Scheme 3,
14–19). O2 is crucial for this reaction, and without O2, no 2d–2j). Further study showed that heteroaromatic methyl alco-
desired product was formed at all (Table 1, entry 20). Yet pure hols, such as 3-thiophene methyl alcohol and 2-furan methyl
O2 did not show superiority to air, only giving 83% vs. 92% iso- alcohol were also good candidates for this styryl ether for-
lated yield in air under the same conditions (Table 1, entries mation; they gave the corresponding desired products in 76%
11 and 13). Thus the optimal condition for styryl ether and 70% yields respectively (Scheme 3, 2k–2l).
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Scheme 5 Synthesis of asymmetric styryl ether from styryl sulfoxide
and benzyl alcohol.
Scheme 6 Styryl ether formation with different purity levels of KOH.
from benzaldehyde and DMSO on the basis of the literature;21
when this compound was subjected to 4-methoxy benzyl
alcohol and 1-phenylethanol under standard conditions,
corresponding asymmetric styryl ethers 2m and 2n were
obtained in 82% and 98% yields respectively (Scheme 5).
In order to exclude the impurity effect in KOH (such as
trace amount of transition metal residue in KOH), we pur-
chased super pure KOH (99.98% purity) and performed the
reaction under standard conditions; 86% of styryl ether was
obtained vs. 92% of the desired product with ≥85% purity of
KOH in air (Scheme 6), thus it ruled out the impurity effect.
Since oxygen was involved in the reaction, the single elec-
tron transfer pathway was first taken into consideration and a
radical trapping experiment was conducted by employing
2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) with benzyl
alcohol under standard conditions, the desired product was
obtained in 68% yield (Scheme 7, eqn (1)). This result showed
that the reaction was not experiencing a radical pathway.
When benzoquinone was added into the reaction instead of
phenol, the desired styryl ether formation was suppressed
Scheme 3 Reactions of various benzyl alcohols in basic DMSO in air.
Reaction condition: benzyl alcohol (0.5 mmol), phenol (20 mol%), KOH
(2 equiv. + 20 mol%), DMSO (1 mL), air.
In order to elucidate the reaction mechanism, an experi-
ment was carried out in DMSO-d6 under the standard con-
ditions. 1H NMR of product d-2a clearly indicated 100%
deuterium incorporation at the extra carbon (Scheme 4).
Obviously, the deuterium could only come from DMSO-d6,
thus the experiment result proved that DMSO provides the
extra carbon in the reaction, which is consistent with the
reported results; in terms of the CvC bond formation in styryl
ether, the possible intermediate—styryl sulfoxide was made
Scheme 4 Reaction of benzyl alcohol in basic deuterium-labeled
DMSO in air and the 1H NMR spectra comparison.
Scheme 7 Control experiments.
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rotary evaporator and the residue was purified by flash chrom-
atography (silica gel, ethyl acetate–petroleum ether = 1 : 30).
Preparation of styryl ether from aryl methyl alcohol
(2-(Benzyloxy)vinyl)benzene (2a, E/Z = 92/8, CAS: 69520-20-
3).15 This was prepared according to the general procedure.
The reaction was performed with benzyl alcohol at 80 °C, and
gave 48.3 mg of product 2a in 92% isolated yield as a white
solid. 1H NMR: (400 MHz, CDCl3, ppm) δ 7.46–7.42 (m, 4H),
7.41–7.38 (m, 1H), 7.34–7.28 (m, 4H), 7.21–7.18 (m, 1H), 7.14
(d, J = 12.9 Hz, 0.92*1H), 6.33 (d, J = 6.8 Hz, 0.08*1H), 6.04
(d, J = 12.9 Hz, 0.92*1H), 5.34 (d, J = 6.8 Hz, 0.08*1H), 5.03
(s, 0.08*2H), 4.95 (s, 0.92*2H). 13C NMR: (100 MHz, CDCl3,
ppm) δ 147.7, 146.2, 136.7, 136.2, 128.5, 128.3, 128.2, 128.0,
127.5, 127.2, 125.7, 125.1, 106.9, 106.3, 74.9, 71.8. mp
41–43 °C.
(E)-1-Bromo-4-(2-((4-bromobenzyl)oxy)vinyl)benzene (2b, E/Z >
99/1, CAS: 507471–18–3).22 This was prepared according to the
general procedure. The reaction was performed with (4-bromo-
phenyl)methanol at 60 °C, and gave 61.3 mg of product 2b in
67% isolated yield as a white solid. 1H NMR: (400 MHz, CDCl3,
ppm) δ 7.51 (d, J = 8.4 Hz, 2H), 7.37 (d, J = 8.4 Hz, 2H), 7.26 (d,
J = 8.4 Hz, 2H), 7.08 (d, J = 8.4 Hz, 2H), 7.03 (d, J = 12.9 Hz,
1H), 5.87 (d, J = 12.9 Hz, 1H), 4.84 (s, 2H). 13C NMR: (100 MHz,
CDCl3, ppm) δ 147.8, 135.5, 135.0, 131.7, 131.6, 129.1, 126.7,
122.1, 119.2, 106.2, 71.1. mp 134–136 °C.
(E)-1-Chloro-4-(2-((4-chlorobenzyl)oxy)vinyl)benzene (2c, E/Z >
99/1, CAS: 84224-58-8).15 This was prepared according to the
general procedure. The reaction was performed with (4-chloro-
phenyl)methanol at 60 °C, and gave 47.9 mg of product 2c in
69% isolated yield as a white solid. 1H NMR: (400 MHz, CDCl3,
ppm) δ 7.37 (d, J = 8.4 Hz, 2H), 7.32 (d, J = 8.4 Hz, 2H), 7.23 (d,
J = 8.4 Hz, 2H), 7.14 (d, J = 8.4 Hz, 2H), 7.02 (d, J = 12.9 Hz,
1H), 5.90 (d, J = 12.9 Hz, 1H), 4.86 (s, 2H). 13C NMR: (100 MHz,
CDCl3, ppm) δ 147.8, 135.0, 134.5, 134.0, 131.3, 128.83, 128.80,
128.7, 126.3, 106.1, 71.1. mp 108–110 °C.
Scheme 8 Phenol-benzoquinone pathway.
(Scheme 7, eqn (2) and (3)), which indicated that benzoqui-
none was not the “active” catalyst in the reaction, thus ruling
out the phenol-benzoquinone mechanism pathway (Scheme 8).
When benzyl alcohol was absent under standard conditions,
no benzoquinone was detected in the reaction (Scheme 7,
eqn (4)), which further proved our above observation.
Conclusions
In summary, a transition-metal-free aerobic oxidative styryl
ether formation method was developed with benzyl alcohols
under basic DMSO. Both phenol and DMSO were important in
styryl ether formation as the former is a good catalyst and the
latter provided the extra carbon for the desired products. A
variety of styryl ethers were prepared smoothly from benzyl
alcohols in good to excellent yields under mild conditions.
Experimental section
General information
All experiments were conducted using a round-bottom flask.
Flash column chromatography was performed over silica gel
(200–300 mesh). 1H NMR spectra were recorded on Bruker
AVIII-400M or 500M spectrometers. Chemical shifts (in ppm)
were referenced to CDCl3 (δ = 7.26 ppm) as the internal stan-
dard. 13C NMR spectra were obtained by using the same NMR
spectrometers and were calibrated with CDCl3 (δ = 77.0 ppm).
Unless otherwise noted, materials obtained from commercial
suppliers were used without further purification, and most
starting materials were purchased from Adamas.
(E)-1-Methyl-4-(2-((4-methylbenzyl)oxy)vinyl)benzene (2d, E/Z >
99/1, CAS: 84224-57-7).15 This was prepared according to the
general procedure. The reaction was performed with p-tolyl-
methanol at 60 °C, and gave 51.8 mg of product 2d in 87% iso-
1
lated yield as a white solid. H NMR: (400 MHz, CDCl3, ppm)
δ 7.31–7.27 (m, 2H), 7.21–7.19 (m, 2H), 7.15–7.13 (m, 2H),
7.09–7.06 (m, 2H), 7.04 (d, J = 12.9 Hz, 1H), 5.95 (d,
J = 12.9 Hz, 1H), 4.86 (s, 2H), 2.37 (s, 3H), 2.32(s, 3H).
13C NMR: (100 MHz, CDCl3, ppm) δ 147.1, 137.8, 135.3,
133.7, 133.3, 129.2, 127.7, 125.0, 106.6, 71.8, 21.2, 21.0. mp
105–107 °C.
Procedure and characterization data for products
General procedure for the preparation of styryl ether from
aryl methyl alcohol. To a round-bottom flask was added the
corresponding aryl methyl alcohol (0.5 mmol), phenol (9.4 mg,
0.1 mmol, 0.2 eq.), potassium hydroxide (61.6 mg, 1.1 mmol,
2.2 eq.) and DMSO (1 mL). The resulting solution was stirred
at 60–80 °C under air for 12 hours. Upon completion of the
reaction, saturated NaCl (10 mL) was added and 1 N HCl was
added to adjust the pH to 7. The solution was extracted by
ethyl acetate (3 × 20mL) and the combined organic layers were
dried over anhydrous Na2SO4. The solvents were removed via a
(E)-1-Isopropyl-4-(2-((4-isopropylbenzyl)oxy)vinyl)benzene (2e,
E/Z > 99/1). This was prepared according to the general pro-
cedure. The reaction was performed with (4-isopropylphenyl)-
methanol at 80 °C, and gave 59.5 mg of product 2e in 81% iso-
lated yield as a white solid. 1H NMR: (400 MHz, CDCl3, ppm) δ
7.35–7.31 (m, 2H), 7.28–7.27 (m, 2H), 7.20–7.14 (m, 4H), 7.06
(d, J = 12.8 Hz, 1H), 5.97 (d, J = 12.8 Hz, 1H), 4.88 (s, 2H),
2.98–2.85 (m, 2H), 1.28 (d, J = 6.8 Hz, 6H), 1.26 (d, J = 6.8 Hz,
6H). 13C NMR: (100 MHz, CDCl3, ppm) δ 148.9, 147.2, 146.4,
134.1, 133.8, 127.8, 126.65, 126.62, 125.1, 106.6, 71.8, 33.9,
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33.7, 24.0. mp 55–57 °C. HRMS (ESI, m/z) calcd for [C21H26O + procedure. The reaction was performed with (4-(tert-butyl)-
Na+]: 317.1881; found: 317.1883.
phenyl)methanol at 60 °C (17 h), and gave 60.3 mg of product
2j in 75% isolated yield as a white solid. H NMR: (500 MHz,
1
(E)-1-Methoxy-4-(2-((4-methoxybenzyl)oxy)vinyl)benzene (2f,
E/Z > 99/1, CAS: 84224-56-6).15 This was prepared according to
the general procedure. The reaction was performed with (4-
methoxyphenyl)methanol at 60 °C, and gave 32.4 mg of
product 2f in 48% isolated yield as a white solid. 1H NMR:
(400 MHz, CDCl3, ppm) δ 7.32 (d, J = 8.8 Hz, 2H), 7.16 (d, J =
8.8 Hz, 2H), 6.97–6.91 (m, 3H), 6.82 (d, J = 8.8 Hz, 2H), 5.92 (d,
J = 12.8 Hz, 1H), 4.81 (s, 2H), 3.82 (s, 3H), 3.79 (s, 3H). 13C
NMR: (100 MHz, CDCl3, ppm) δ 159.5, 157.9, 146.3, 129.3,
128.9, 128.8, 126.2, 114.1, 114.0, 106.3, 71.6, 55.3. mp
120–121 °C.
CDCl3, ppm) δ 7.43 (2H, d, J = 8.4 Hz), 7.35 (2H, d, J = 8.4 Hz),
7.31 (2H, d, J = 8.4 Hz), 7.20 (2H, d, J = 8.4 Hz), 7.07 (1H, d, J =
12.9 Hz), 5.98 (1H, d, J = 12.6 Hz), 4.88 (2H, s), 1.36 (9H, s),
1.33 (9H, s). 13C NMR: (125 MHz, CDCl3, ppm) δ 151.1, 148.7,
147.3, 133.8, 133.4, 127.5, 125.5, 125.4, 124.9, 106.6, 71.8, 34.6,
34.4, 31.3.
3-(((2-(Thiophen-3-yl)vinyl)oxy)methyl)thiophene (2k, E/Z = 87/
13). This was prepared according to the general procedure.
The reaction was performed with thiophen-3-ylmethanol at
60 °C, and gave 42.2 mg of product 2j in 76% isolated yield as
(E)-1-Methoxy-3-(2-((3-methoxybenzyl)oxy)vinyl)benzene (2g, a white solid. 1H NMR: (400 MHz, CDCl3, ppm) δ 7.35–7.33
(1H, m), 7.30–7.29 (m, 1H), 7.25–7.24 (m, 1H), 7.11 (dd, J1 = 4.8
Hz, J2 = 1.2 Hz, 1H), 7.05 (dd, J1 = 5.2 Hz, J2 = 1.2 Hz, 1H), 7.00
(d, J = 13.2 Hz, 0.87*1H), 6.94 (dd, J1 = 2.8 Hz, J2 = 1.2 Hz, 1H),
6.24 (d, J = 6.4 Hz, 0.13*1H), 6.00 (d, J = 13.2 Hz, 0.87*1H),
5.42 (d, J = 6.8 Hz, 0.13*1H), 4.99 (s, 0.13*2H), 4.88 (s,
0.87*2H). 13C NMR: (100 MHz, CDCl3, ppm) δ 147.6, 137.7,
137.2, 127.0, 126.4, 125.9, 124.5, 123.2, 118.3, 102.0, 67.2. mp
84–86 °C. HRMS (ESI, m/z) calcd for [C11H10OS2 + Na+]:
245.0071; found: 245.0074.
E/Z > 99/1). This was prepared according to the general pro-
cedure. The reaction was performed with (3-methoxyphenyl)
methanol at 60 °C (15 h), and gave 49.9 mg of product 2g in
74% isolated yield as a colorless liquid. 1H NMR: (400 MHz,
CDCl3, ppm) δ 7.31 (t, J = 8.0 Hz, 1H), 7.19 (t, J = 8.0 Hz, 1H),
7.09 (d, J = 12.9 Hz, 1H), 6.99–6.95 (m, 2H), 6.89–6.84 (m, 2H),
6.78 (t, J = 2.0 Hz, 1H), 6.72–6.70 (m, 1H), 5.94 (d, J = 12.9 Hz,
1H), 4.88 (s, 2H), 3.83 (s, 3H), 3.81 (s, 3H). 13C NMR:
(100 MHz, CDCl3, ppm) δ 159.8, 159.7, 147.9, 138.2, 137.6,
129.6, 129.5, 119.7, 117.7, 113.7, 112.9, 111.1, 110.8, 106.8,
71.7, 55.2, 55.1. HRMS (ESI, m/z) calcd for [C17H18O3 + Na+]:
293.1154; found: 293.1151.
3-(((2-([1,1′-Biphenyl]-3-yl)vinyl)oxy)methyl)-1,1′-biphenyl (2h,
E/Z = 86/14). This was prepared according to the general pro-
cedure. The reaction was performed with [1,1′-biphenyl]-3-yl-
methanol at 80 °C, and gave 74.2 mg of product 2h in 82%
isolated yield as a white solid. 1H NMR: (400 MHz, CDCl3,
ppm) δ 7.64–7.57 (m, 7H), 7.47–7.35 (m, 11H), 7.19 (d, J = 12.8
Hz, 0.86*1H), 6.36 (d, J = 6.8 Hz, 0.14*1H), 6.09 (d, J = 12.8 Hz,
0.86*1H), 5.40 (d, J = 6.8 Hz, 0.14*1H), 5.04 (s, 0.14*2H), 4.97
(s, 0.86*2H). 13C NMR: (100 MHz, CDCl3, ppm) δ 147.9, 146.4,
141.6, 141.2, 140.8, 137.2, 136.6, 129.0, 128.7, 128.6, 127.4,
127.2, 127.13, 127.11, 126.9, 126.8, 126.4, 126.3, 126.1, 125.9,
124.7, 124.2, 124.0, 106.9, 106.5, 74.8, 71.9. mp 64–66 °C.
HRMS (ESI, m/z) calcd for [C27H22O + Na+]: 385.1568; found:
385.1563.
2-(((2-(Furan-2-yl)vinyl)oxy)methyl)furan (2l, E/Z
= 90/10).
This was prepared according to the general procedure.
The reaction was performed with furan-2-ylmethanol at 60 °C,
and gave 36 mg of product 2k in 70% isolated yield as a white
1
solid. H NMR: (400 MHz, CDCl3, ppm) δ 7.42 (s, 1H), 7.23 (s,
1H), 7.04 (d, J = 12.8 Hz, 1H), 6.40–6.27 (m, 3H), 6.00 (s, 1H),
5.80 (d, J = 12.8 Hz, 1H), 5.40 (d, J = 6.4 Hz, 0.11*1H), 4.87 (s,
0.11*2H), 4.78 (s, 2H). 13C NMR: (100 MHz, CDCl3, ppm) δ
151.2, 149.9, 146.9, 143.8, 143.3, 142.5, 140.3, 139.8, 111.3,
111.0, 110.5, 110.2, 108.1, 104.5, 97.6, 97.1, 66.4, 64.2. mp
36–38 °C. HRMS (ESI, m/z) calcd for [C11H10O + Na+]:
213.0528; found: 213.0530.
Preparation of key intermediate—styryl sulfoxide
(E)-(2-(Methylsulfinyl)vinyl)benzene (CAS: 38082-31-4).15 This
was prepared according to the previous reports.6 To a Schlenk
tube was added potassium hydroxide (280 mg, 5 mmol, 1 eq.),
DMSO (10 ml), and benzaldehyde (530 mg, 5 mmol, 1 eq.)
under dry nitrogen. The resulting solution was stirred at 60 °C
for 90 min. Upon completion of the reaction, saturated NaCl
(30 mL) was added. The solution was extracted by ethyl acetate
(3 × 30 mL) and the combined organic layers were dried over
anhydrous Na2SO4. The solvents were removed via a rotary
evaporator and the residue was purified with flash chromato-
graphy (silica gel, ethyl acetate–petroleum ether = 4 : 1) to
(E)-1-(((2-(Naphthalen-1-yl)vinyl)oxy)methyl)naphthalene (2i,
E/Z > 99/1). This was prepared according to the general pro-
cedure. The reaction was performed with naphthalen-1-
ylmethanol at 60 °C, and gave 51.1 mg of product 2i in 66%
isolated yield as a white solid. 1H NMR: (400 MHz, CDCl3,
ppm) δ 8.17–8.11 (m, 2H), 7.96–7.87 (m, 3H), 7.76 (d, J = 8.0
Hz, 1H), 7.66–7,62 (m, 2H), 7.60–7.58 (m, 1H), 7.55–7.49 (m,
4H), 7.46–7.42 (m, 1H), 7.15 (d, J = 12.6 Hz, 1H), 6.76 (d, J =
12.6 Hz, 1H), 5.47 (s, 2H). 13C NMR: (100 MHz, CDCl3, ppm) δ
148.9, 133.8, 133.7, 133.3, 132.1, 131.5, 131.4, 129.2,
128.7,128.4, 126.8, 126.7, 126.5, 126.0, 125.73, 125.70, 125.69,
125.3, 124.1, 123.7, 122.9, 104.1, 70.6. mp 64–65 °C. HRMS
1
afford the product as a colorless oil (257 mg, 31%). H NMR:
(400 MHz, CDCl3, ppm) δ 7.48–7.45 (m, 2H), 7.41–7.35 (m,
3H), 7.26 (d, J = 15.2 Hz, 1H), 6.90 (d, J = 15.2 Hz, 1H), 2.7 (s,
3H). 13C NMR: (100 MHz, CDCl3, ppm) δ 136.4, 133.7, 132.2,
129.7, 128.9, 127.6, 40.9.
(ESI, m/z) calcd for [C23H18O
+
Na+]: 333.1255; found:
Preparation of asymmetric styryl ether
(E)-1-Methoxy-4-((styryloxy)methyl)benzene (2m, CAS: 1445154-
10-8).15 A round-bottom flask was charged with (4-methoxy-
phenyl)methanol (27.0 mg, 0.25 mmol, 1 eq.), (E)-(2-(methyl-
333.1256.
(E)-1-(tert-Butyl)-4-(2-((4-(tert-butyl)benzyl)oxy)vinyl)benzene
(2j, E/Z > 99/1). This was prepared according to the general
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Organic & Biomolecular Chemistry
sulfinyl)vinyl)benzene (49.8 mg, 0.3 mmol, 1.2 eq.), phenol Hundred Talents Program and Research Funds of Huaqiao
(4.7 mg, 0.05 mmol, 0.2 eq.), potassium hydroxide (30.8 mg, University.
0.55 mmol, 2.2 eq.) and DMSO (1 mL). The resulting solution
was stirred at 60 °C under air for 12 hours. Upon completion
of the reaction, saturated NaCl (10 mL) was added and 1 N HCl
Notes and references
was added to adjust the pH to 7. The solution was extracted by
ethyl acetate (3 × 20 mL) and the combined organic layers were
1 P. T. Anastas and J. Warner, Green Chemistry: Theory and
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atography (silica gel, ethyl acetate–petroleum ether = 1 : 30) to
1
afford the product as a white solid (46.5 mg, 82%). H NMR:
(500 MHz, CDCl3, ppm) δ 7.35 (d, J = 8.5 Hz, 2H), 7.30–7.25 (m,
4H), 7.16 (t, J = 7.0 Hz, 1H), 7.10 (J = 13.0 Hz, 1H), 6.95 (d, J =
4 P. J. Walsh, H. Li and C. A. de Parrodi, Chem. Rev., 2007,
8.5 Hz, 2H), 5.98 (d, J = 13.0 Hz, 1H), 4.85 (s, 2H), 3.84 (s, 3H).
107, 2503–2545.
13C NMR: (125 MHz, CDCl3, ppm) δ 159.5, 147.7, 136.3, 129.3,
128.8, 128.5, 125.7, 125.1, 114.0, 106.7, 71.7, 55.3. mp
5 M. Bala, P. K. Verma, U. Sharma, N. Kumar and B. Singh,
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100–101 °C.
6 C. Tao, F. Liu, Y. Zhu, W. Liu and Z. Cao, Org. Biomol.
(E)-(2-(1-Phenylethoxy)vinyl)benzene (2n, CAS: 1445154-11-9)1.
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A round-bottom flask was charged with 1-phenylethanol
7 D. K. T. Yadav and B. M. Bhanage, Eur. J. Org. Chem., 2013,
(30.5 mg, 0.25 mmol, 1 eq.), (E)-(2-(methylsulfinyl)vinyl)-
5106–5110.
benzene (49.8 mg, 0.3 mmol, 1.2 eq.), phenol (4.7 mg,
0.05 mmol, 0.2 eq.), potassium hydroxide (30.8 mg,
0.55 mmol, 2.2 eq.) and DMSO (1 mL). The resulting solution
was stirred at 60 °C under air for 12 hours. Upon completion
of the reaction, saturated NaCl (10 mL) was added and 1 N HCl
was added to adjust the pH to 7. The solution was extracted by
ethyl acetate (3 × 20 mL) and the combined organic layers were
dried over anhydrous Na2SO4. The solvents were removed via a
8 W. Yin, C. Wang and Y. Huang, Org. Lett., 2013, 15, 1850–
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12 A. E. Wendlandt, A. M. Suess and S. S. Stahl, Angew. Chem.,
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Int. Ed., 2011, 50, 11062–11087.
13 Z. Shi, C. Zhang, C. Tang and N. Jiao, Chem. Soc. Rev.,
afford the product as a colorless liquid (54.9 mg, 98%). 1H
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NMR: (500 MHz, CDCl3, ppm) δ 7.40–7.37 (4H, m), 7.34–7.31
14 C. Zhang, C. Tang and N. Jiao, Chem. Soc. Rev., 2012, 41,
(1H, m), 7.25–7.22 (2H, m), 7.19–7.17 (2H, m), 7.14–7.11 (1H,
3464–3484.
m), 6.89 (1H, d, J = 12.7 Hz), 5.98 (1H, d, J = 12.7 Hz), 5.00 (1H,
15 Q. Zhang, S. Cai, L. Li, Y. Chen, H. Rong, Z. Niu, J. Liu,
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16 M. Julia, A. Righini and D. Uguen, J. Chem. Soc., Perkin
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17 B. Katsnelson, L. Privalova, V. Gurvich, O. Makeyev,
q, J = 6.5 Hz), 1.62 (3H, d, J = 6.5 Hz). 13C NMR: (125 MHz,
CDCl3, ppm) δ 146.6, 142.7, 136.3, 128.6, 128.4, 127.7, 125.9,
125.6, 125.1, 108.5, 79.0, 23.6.
Preparation of styryl ether in d6-DMSO
d-(E)-(2-(Benzyloxy)vinyl)benzene (d-2a, CAS: 344740-75-6).15
V. Shur, Y. Beikin, M. Sutunkova, E. Kireyeva,
It was prepared according to general procedure in d6-DMSO
I. Minigalieva, N. Loginova, M. Vasilyeva, A. Korotkov,
(1 mL). The reaction was performed with benzyl alcohol at
60 °C, and gave 34 mg of product d-2a in 65% isolated yield as
E. Shuman, L. Vlasova, E. Shishkina, A. Tyurnina, R. Kozin,
I. Valamina, S. Pichugova and L. Tulakina, Int. J. Mol. Sci.,
a white solid. 1H NMR: (500 MHz, CDCl3, ppm) δ 7.38–7.37 (m,
2013, 14, 2449–2483.
4H), 7.33–7.31 (m, 1H), 7.25–7.20 (m, 4H), 7.14–7.10 (m, 1H),
18 V. Matranga and I. Corsi, Mar. Environ. Res., 2012, 76, 32–
5.94 (s, 1H), 4.88 (s, 2H). 13C NMR: (125 MHz, CDCl3, ppm) δ
40.
147.4, 136.7, 136.2, 128.6, 128.1, 127.6, 125.7, 125.1, 106.7,
71.8. mp 39–41 °C.
19 W. J. Trickler, S. M. Lantz, R. C. Murdock, A. M. Schrand,
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Acknowledgements
1702.
We are grateful for the financial support from the National 21 G. A. Russell and H.-D. Becker, J. Am. Chem. Soc., 1963, 85,
Natural Science Foundation of China (21202049), the Recruit-
3406–3410.
ment Program of Global Experts (1000 Talents Plan), Fujian 22 M. Shi and Y. M. Shen, J. Chem. Res. (S), 2002, 422–427.
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2014