Peroxide-Free Co(OAc)2-Catalyzed Radical Addition of sp3 C-H Bonds to Alkynes

Article abstract of DOI:10.1055/s-0036-1588909

Cobalt-catalyzed radical addition of C-H bonds adjacent to an oxygen atom towards alkynes is described. The reaction proceeded at 60 °C without using additional radical initiators, and leads to 2-vinyl ether derivatives in good yields.

Full text of DOI:10.1055/s-0036-1588909

SYNTHESIS
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
© Georg Thieme Verlag Stuttgart · New York
2016, 48, A–G
paper
A
M. Zhang et al.
Paper
Synthesis
Peroxide-Free Co(OAc)2-Catalyzed Radical Addition of sp3 C–H
Bonds to Alkynes
Min Zhang
X
peroxide-free
R2
X
Yun Zhao
+
O
Wanzhi Chen*
R1
R1
O
H
Co(OAc)2•4H2O (10 mol%)
KOAc (12 mol%)
60 °C, air
R2
Department of Chemistry, Zhejiang University,
Hangzhou 310013, P. R. of China
chenwzz@zju.edu.cn
X = C, O
24 examples
mild conditions
25–72% yield
Received: 29.07.2016
Accepted after revision: 17.10.2016
Published online: 28.11.2016
Table 1 Optimization of the Reaction Conditions of Cobalt-Catalyzed
Addition of THF with Alkynesa
DOI: 10.1055/s-0036-1588909; Art ID: ss-2016-h0537-op
catalyst, additive
Abstract Cobalt-catalyzed radical addition of C–H bonds adjacent to
an oxygen atom towards alkynes is described. The reaction proceeded
at 60 °C without using additional radical initiators, and leads to 2-vinyl
ether derivatives in good yields.
+
O
Ph
1a
O
Ph
60 °C, air
H
2
3a
Additive (12 mol%) Yield (%)b
E/Zc
Key words cobalt catalysis, radical addition, alkyne, tetrahydrofuran
Entry
Catalyst (10 mol%)
NaOtBu
KOtBu
NaOH
K3PO4
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
–
trace
trace
10
–
.
1
2
Co(OAc)2 4H2O
The formation of C–C bonds is the most fundamental
transformation in the construction of complex molecules.
Traditional strategies include Friedel–Crafts reaction,1 Aldol
condensation,2 Michael addition reaction,3 nucleophilic ad-
dition, and substitution reaction involving Grignard re-
agents.4 In recent decades, palladium-catalyzed cross-cou-
pling reactions were developed as one of the most efficient
protocols in modern organic synthetic chemistry.5 The cou-
pling reactions often rely on prefunctionalized substrates.
Transition-metal-catalyzed direct carbon–hydrogen bond
functionalization has progressed greatly over the past two
decades.6 Most of these works have focused on directed C–
H activation under the influence of a pre-existing donating
group. The C–C bond formation through radical coupling
and radical addition reactions are also promising,7 especial-
ly reactions that proceed via radicals generated from homo-
lytic fission of a C–H bond. Cyclic ethers such as tetrahydro-
furan are good nucleophilic radical precursors that can re-
act with various electrophiles.8
.
Co(OAc)2 4H2O
–
.
3
Co(OAc)2 4H2O
0.8
0.6
0.7
0.8
0.8
0.6
–
.
4
Co(OAc)2 4H2O
23
.
5
Co(OAc)2 4H2O
68
6
CoCl2
34
7
CoCO3
Co(PPh3)2Cl2
CuCl
13
8
18
9
trace
trace
trace
trace
n.r.
10
11d
12e
13
14
15f
16g
CuBr
–
.
Co(OAc)2 4H2O
–
.
Co(OAc)2 4H2O
–
–
–
.
Co(OAc)2 4H2O
–
n.r.
–
.
Co(OAc)2 4H2O
KOAc
KOAc
n.r.
–
.
Co(OAc)2 4H2O
14
0.8
a Unless otherwise mentioned, all reactions were carried out using 1 (0.3
mmol) in THF (1.5 mL) at 60 °C under air for 10 h.
b Yield of isolated mixtures of cis/trans isomers.
c E/Z ratios were determined through 1H NMR analysis of crude reaction
mixtures.
2-Vinyl tetrahydrofuran derivatives serving as structur-
al motifs play an important role in biological products and
synthetic pharmaceuticals.9 Synthesis of 2-vinyl tetrahy-
drofurans through direct radical addition of an sp3 C–H
bond adjacent to the oxygen atom of tetrahydrofuran (THF)
with various alkynes has been accomplished. It has been
found that copper,10 cobalt,11 or rhodium12 catalysts or visi-
d The reaction was conducted at room temperature.
e The reaction was conducted in a solvent mixture of THF (0.5 mL) and
MeCN (1.0 mL).
f The reaction was conducted under N2 atmosphere.
g The reaction was conducted under O2 atmosphere.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

B
M. Zhang et al.
Paper
Synthesis
ble-light13 can efficiently catalyze the addition of sp3 C–H
bonds to alkynes. However, organic peroxides such as TBHP
are required. Organic peroxides are usually unstable and
sensitive to heat and collision. Therefore, it would be a bet-
ter choice to avoid the use of organic peroxides. Some ef-
forts have been made to improve the reaction. Direct addi-
tion of cyclic ethers to alkynes under microwave conditions
was reported to require quite high temperature.14 Allyl and
benzyl chlorides could initiate reactions of tetrahydrofuran
and alkynes, but the yields were quite low (ca. 20%).15
Me2Zn was found to promote the reaction but the scope
was limited to internal alkynes.16 We found that O2 can ini-
tiate the formation of the tetrahydrofuran radical in the
The reaction of phenylacetylene (1a; 0.3 mmol) with
tetrahydrofuran (2; 1.5 mL) was chosen as the model reac-
tion for the optimization study; the results are summarized
in Table 1. It was found that at a loading of 10 mol%
.
Co(OAc)2 4H2O at 60 °C, no desired addition product was
observed. In the presence of NaOtBu or KOtBu, only 1,4-di-
phenylbuta-1,3-diyne was isolated resulting from the oxi-
dative dimerization of phenylacetylene. When NaOH and
K3PO4 were added, the addition product was obtained in 10
and 23% yield, respectively. To our delight, addition of KOAc
could efficiently promote the addition reaction, and the
yield was sharply increased to 68% (Table 1, entries 1–5).
We also examined the effect of different cobalt salts. Under
the same conditions, other cobalt catalysts such as CoCl2,
CoCO3, and Co(PPh3)2Cl2, were less active (entries 6–8).
CuBr and CuCl were also examined. Under the same condi-
.
presence of Co(OAc)2 4H2O. Herein, we report the prepara-
tion of 2-vinyl tetrahydrofurans by using cobalt catalyst un-
der air, without the addition of organic peroxides.
Co(OAc)2•4H2O (10 mol%)
R
KOAc (12 mol%)
O
+
O
Ar
Ar
60 °C, air
H
R
1
2
3
F
O
O
O
O
F
F
3a 68%
(E/Z = 0.7)
3b 69%
(E/Z = 0.8)
3c 63%
(E/Z = 1.0)
3d 72%
(E/Z = 0.6)
Cl
O
O
O
O
Cl
Cl
Br
3e 44%
(E/Z = 0.5)
3f 51%
(E/Z = 0.9)
3g 54%
(E/Z = 0.4)
3h 61%
(E/Z = 0.7)
O
O
O
O
Br
MeO
3j 55%
(E/Z = 0.6)
3k 45%
(E/Z = 0.8)
3l 61%
(E/Z = 0.9)
3i 59%
(E/Z = 0.1)
O
O
O
O
N
OMe
COOMe
3n 34%
(E/Z = 0.2)
3m 54%
(E/Z = 0.5)
3o 43%
(E/Z = 0.7)
3p 25%
O
O
O
CHO
O
O
3q 50%
(E/Z = 0.6)
3r 52%
(E/Z = 0.8)
3s 32%
(E/Z = 0.4)
3t 43%
(E/Z = 0.4)
Scheme 1 Substrate scope of the cobalt-catalyzed addition of THF with alkynes. Isolated yields. E/Z ratios were determined through 1H NMR analysis
of the product.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

C
M. Zhang et al.
Paper
Synthesis
tions, the desired product was not detected by NMR mea-
surement (entries 9 and 10). When the reaction was con-
ducted at room temperature, no reaction occurred (entry
11). Mixed solvents disfavored the reaction, probably be-
cause of the low reactivity of THF (entry 12).17
less than 10% yield as determined by gas chromatography. It
was found that cobalt(II) could efficiently catalyze the reac-
tion of 1,3-dioxolane with phenylacetylenes; the results are
listed in Scheme 2. 1,3-Dioxolane bears two oxygen atoms,
and two regioisomers were expected. However, the reac-
tion mainly occurred at the C-2 position of 1,3-dioxolane,
and 2-alkenylated 1,3-dioxolanes 5a–d were afforded in
moderate yields.
In addition, we failed to obtain the product under N2 at-
mosphere, illustrating that O2 is essential (Table 1, entry
15). Unexpectedly, the yield was also quite low under an O2
atmosphere, and the major product was diphenylbuta-1,3-
diyne (entry 15). In all the reactions, the products were iso-
lated as cis/trans isomers with the Z isomers predominat-
ing.
O
Co(OAc)2•4H2O (10 mol%)
O
O
KOAc (12 mol%)
+
R
R
60 °C, air
.
O
The results presented above showed that Co(OAc)2 4H2O
H
1
4
5
can catalyze the radical addition of tetrahydrofuran to-
wards triple bonds under the very mild conditions. To ex-
amine the generality of the reaction, the reactivity of a
number of aromatic alkynes bearing either electron-with-
drawing or electron-donating groups was tested. The re-
sults are summarized in Scheme 1. By using THF as both the
solvent and reactant, unsubstituted phenylacetylene react-
ed with THF to give 2-styryltetrahydrofuran 3a in a yield of
O
O
O
O
5a 55%
(E/Z = 0.6)
5b 47%
(E/Z = 0.3)
O
O
O
O
.
68% in the presence of 10 mol% Co(OAc)2 4H2O and 12 mol%
Cl
KOAc. Fluorine-containing phenylacetylene showed similar
activities to those of phenylacetylene, and ortho-, meta-,
and para-fluorophenylacetylene, affording corresponding
addition products 3b–d in 63–72% yields.
5c 43%
(E/Z = 0.8)
5d 51%
(E/Z = 0.3)
Scheme 2 Cobalt-catalyzed addition of 1,3-dioxolane with alkynes.
Isolated yields. E/Z ratios were determined through 1H NMR analysis of
the product.
Chlorine-containing phenylacetylene also reacted with
THF, giving 2-styryltetrahydrofuran derivatives 3e–g in
slightly lower yields. The reactivity of bromine-containing
phenylacetylenes were between those of the corresponding
chlorophenylacetylene and fluorophenylacetylene, and the
target product 2-styryltetrahydrofuran derivatives 3h–i
were obtained in ca. 60% yield. In these reactions, ortho-
substituents did not show obvious steric effects. Phenyl-
acetylenes bearing electron-donating groups such as meth-
yl and methoxyl were also good reactants, and the target
products 3j–m were obtained in ca. 50% yield at 60 °C. Al-
though 2-ethynylpyridine is also reactive, 2-[2-(tetrahydro-
furan-2-yl)vinyl]pyridine (3p) was afforded in only 25%
yield.
This is probably because the radical intermediate result-
ing from the electron-deficient alkyne is less stable. Under
the same conditions, internal alkynes were applied to give
trisubstituted alkenes. Unsymmetric propyn-1-ylbenzene
also reacted with THF to give 2-(1-phenylpropen-2-yl)tet-
rahydrofuran (3r), and the regioisomer 2-(1-phenylpropen-
1-yl)tetrahydrofuran was not detected by NMR spectrosco-
py. Similarly, the radical addition of THF towards diphenyl-
acetylene and ditolylacetylene at 60 °C led to the isolation
of 3s and 3t, respectively.
Based on the experimental data listed in Table 1, we
tentatively propose that the reaction proceeds through a
radical mechanism. This is supported by a control experi-
ment that showed that when the reaction was conducted
for 24 h in the presence of one equivalent of 2,2,6,6-te-
tramethylpiperidine-1-oxyl (TEMPO) under the standard
conditions, no addition product was observed (Scheme 3).
The reaction is probably initiated by the reaction of Co(II)
with O2 leading to Co(III)-O-O· radical. Abstraction of a H
atom from a THF molecule would generate a THF radical
and Co(III)-O-OH. Subsequent radical addition towards the
triple bond would form olefinic radicals. Finally, the olefinic
radicals would abstract one H atom from THF affording the
addition product and regenerate THF radicals.
Co(OAc)2•4H2O (10 mol%)
KOAc (12 mol%)
O
+
+
TEMPO
60 °C, air
24 h
O
1a
2
3a
Scheme 3 A control experiment
The addition reactions of alkynes with other cyclic
ethers including 1,4-dioxane, 2,5-dimethoxytetrahydrofu-
ran, morpholine, and 2,3-dihydrofuran were also examined
under the conditions detailed above. Unfortunately, these
reactions gave mixtures containing the desired products in
.
In summary, Co(OAc)2 4H2O-catalyzed direct radical ad-
dition of a C–H bond adjacent to the oxygen atom of THF
and 1,3-dioxolane towards alkynes was described. The re-
actions afford a number of 2-alkenylated tetrahydrofuran
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

D
M. Zhang et al.
Paper
Synthesis
and 1,3-dioxolane derivatives in good yields under very
mild conditions without use of additional radical initiators.
This protocol offers an economic and convenient synthetic
route to 2-styryltetrahydrofurans.
13C NMR (100 MHz, CDCl3): δ = 162.3 (d, JC–F = 245.2 Hz), 162.0 (d,
JC–F = 245.1 Hz), 133.0 (d, JC–F = 3.0 Hz), 132.7, 132.7, 130.5 (d, JC–F
=
13.9 Hz), 130.5, 130.3 (d, JC–F = 2.3 Hz), 129.3, 128.0 (d, JC–F = 8.0 Hz),
115.4 (d, JC–F = 21.5 Hz), 115.1 (d, JC–F = 21.3 Hz), 79.6, 74.9, 68.2, 68.1,
32.9, 32.4, 26.4, 25.9.
HRMS: m/z [M+] calcd for C12H13FO: 192.0950; found: 192.0943.
Unless otherwise noted, all reactions were carried out under air in
Schlenk tubes with magnetic stirring. Temperature was maintained
by using a thermostat-controlled silicone oil bath. All the chemicals
were purchased commercially, and used without further purification.
Anhydrous THF was distilled from Na by using benzophenone as the
indicator. Purification of the reaction products was carried out by
flash column chromatography using 300–400 mesh silica gel. Thin-
layer chromatography (TLC) was performed with Huanghai GF254 sil-
ica gel coated plates and visualized by exposure to UV light (254 nm).
1H NMR (400 MHz) and 13C NMR (100 MHz) were recorded with
Avance Bruker Spectrometers with CDCl3 as solvent and tetramethyl-
silane (TMS) as internal standard. Chemical shifts are referenced to
residual solvent peaks (CDCl3: δH = 7.28 ppm; δC = 77.0 ppm). Data for
1H NMR spectra are reported as: chemical shift (ppm, referenced to
TMS; s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet of
doublets, dt = doublet of triplets, m = multiplet), coupling constant
(Hz), and integration. High-resolution mass spectra (HRMS) were re-
corded with a Bruker Apex IV FTMS mass spectrometer (ESI). IR spec-
tra were recorded with a Perkin–Elmer BXII spectrophotometer.
2-(3-Fluorostyryl)tetrahydrofuran (3c)18
Yield: 36.5 mg (63%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 1.0; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.24–6.83 (m, 8 H), 6.50–6.46 (m, 2 H),
6.14 (dd, J = 15.6, 6.4 Hz, 1 H), 5.67 (dd, J = 11.6, 8.8 Hz, 1 H), 4.58–
4.52 (m, 1 H), 4.43–4.38 (m, 1 H), 3.93–3.86 (m, 2 H), 3.80–3.69 (m,
2 H), 2.11–2.02 (m, 2 H), 1.96–1.84 (m, 4 H), 1.68–1.61 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 163.1 (d, JC–F = 243.3 Hz), 162.6 (d, JC–F
=
244.2 Hz), 139.3 (d, JC–F = 7.5 Hz), 138.9 (d, JC–F = 7.5 Hz), 134.0, 132.0,
130.3 (d, JC–F = 1.7 Hz), 129.9 (d, JC–F = 8.7 Hz), 129.6 (d, JC–F = 8.4 Hz),
129.2 (d, JC–F = 2.5 Hz), 124.6 (d, JC–F = 2.7 Hz), 122.4 (d, JC–F = 2.6 Hz),
115.6 (d, JC–F = 21.5 Hz), 114.1 (d, JC–F = 4.7 Hz), 114.1 (d, JC–F = 4.9 Hz),
112.9 (d, JC–F = 21.6 Hz), 79.3, 74.9, 68.3, 68.1, 32.9, 32.4, 26.4, 25.9.
HRMS: m/z [M+] calcd for C12H13FO: 192.0950; found: 192.0945.
2-(2-Fluorostyryl)tetrahydrofuran (3d)18
Yield: 41.8 mg (72%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.6; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.47–6.99 (m, 6.4 H), 6.74 (d, J =
16.0 Hz, 0.6 H), 6.60 (d, J = 8.0 Hz, 1 H), 6.30 (dd, J = 16.0, 6.4 Hz,
0.6 H), 5.80 (dd, J = 11.6, 8.8 Hz, 1 H), 4.58–4.46 (m, 1.6 H), 4.00–3.92
(m,1.6 H), 3.87–3.75 (m, 1.6 H), 2.18–2.08 (m, 1.6 H), 2.03–1.87 (m,
3.2 H), 1.76–1.64 (m, 1.6 H).
Cobalt-Catalyzed Addition of THF and 1,3-Dioxolane with Alkynes;
General Procedure
Co(OAc)2·4 H2O (0.1 equiv) and KOAc (0.12 equiv) were added to ei-
ther THF or 1,3-dioxolane (1.5 mL) in a Schlenk tube under air. Alkyne
(0.3 mmol, 1.0 equiv) was then added and the mixture was stirred
and heated at 60 °C for 10 h. The resulting mixture was purified by
flash column chromatography (petroleum ether/EtOAc, 50:1) to af-
ford the desired pure product.
13C NMR (100 MHz, CDCl3): δ = 160.3 (d, JC–F = 247.8 Hz), 160.2 (d, JC–F
=
245.7 Hz), 134.7, 133.2 (d, JC–F = 4.6 Hz), 130.8 (d, JC–F = 1.7 Hz), 129.0
(d, JC–F = 8.1 Hz), 128.7 (d, JC–F = 8.2 Hz), 127.5 (d, JC–F = 3.9 Hz), 124.6
(d, JC–F =12.3 Hz), 124.4 (d, JC–F = 14.4 Hz), 124.0 (d, JC–F = 3.2 Hz), 123.7
(d, JC–F = 3.6 Hz), 122.8 (d, JC–F = 1.7 Hz), 115.7 (d, JC–F = 22.3 Hz), 115.3
(d, JC–F = 21.7 Hz), 79.8, 75.2, 68.2, 68.1, 32.7, 32.4, 26.4, 25.9.
2-Styryltetrahydrofuran (3a)18
Yield: 35.3 mg (68%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.7; Rf = 0.50 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C12H13FO: 192.0950; found: 192.0943.
1H NMR (400 MHz, CDCl3): δ = 7.39–7.22 (m, 8.5 H), 6.61–6.56 (m,
1.7 H), 6.24–6.18 (m, 0.7 H), 5.73–5.68 (m, 1 H), 4.67 (dd, J = 15.2,
7.6 Hz, 1 H), 4.48 (dd, J = 14.0, 7.2 Hz, 0.7 H), 4.00–3.93 (m, 1.7 H),
3.87–3.76 (m, 1.7 H), 2.18–2.09 (m, 1.7 H), 2.04–1.89 (m, 3.4 H), 1.74–
1.70 (m, 1.7 H).
13C NMR (100 MHz, CDCl3): δ = 136.9, 136.7, 132.9, 131.5, 130.5,
130.5, 128.8, 128.5, 128.2, 127.5, 127.1, 126.5, 79.7, 75.1, 68.2, 68.1,
32.9, 32.4, 26.4, 25.9.
2-(4-Chlorostyryl)tetrahydrofuran (3e)18
Yield: 27.3 mg (44%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.5; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.23–7.15 (m, 6 H), 6.48–6.44 (m,
1.5 H), 6.11 (dd, J = 16.0, 6.8 Hz, 0.5 H), 5.64 (dd, J = 11.6, 8.8 Hz, 1 H),
4.51 (dd, J = 15.6, 8.0 Hz, 1 H), 4.38 (q, J = 13.2, 6.4 Hz, 0.5 H), 3.92–
3.85 (m, 1.5 H), 3.79–3.68 (m, 1.5 H), 2.09–2.01 (m, 1.5 H), 1.95–1.84
(m, 3.1 H), 1.65–1.59 (m, 1.5 H).
HRMS: m/z [M+] calcd for C12H14O: 175.1045; found: 175.1049.
13C NMR (100 MHz, CDCl3): δ = 134.3, 132.5.0, 132.0, 130.2, 129.4,
129.1, 128.1, 127.6, 127.3, 127.0, 126.7, 126.6, 78.4, 73.8, 67.2, 67.1,
31.9, 31.3, 25.4, 24.9.
2-(4-Fluorostyryl)tetrahydrofuran (3b)18
Yield: 40.0 mg (69%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.8; Rf = 0.50 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C12H13ClO: 208.0655; found: 208.0651.
1H NMR (400 MHz, CDCl3): δ = 7.35–7.25 (m, 3.6 H), 7.04–6.96 (m,
3.6 H), 6.56–6.52 (m, 1.8 H), 6.12 (dd, J = 16.0, 6.8 Hz, 0.8 H), 5.69 (dd,
J = 11.6, 8.8 Hz, 0.8 H), 4.63–4.57 (m, 0.8 H), 4.48–4.42 (m, 0.8 H),
3.99–3.93 (m, 1.8 H), 3.86–3.76 (m, 1.8 H), 2.16–2.08 (m, 1.8 H), 2.06–
1.88 (m, 3.6 H), 1.75–1.64 (m, 1.8 H).
2-(3-Chlorostyryl)tetrahydrofuran (3f)18
Yield: 31.6 mg (51%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.9; Rf = 0.50 (PE/EtOAc, 10:1).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

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M. Zhang et al.
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Synthesis
1H NMR (400 MHz, CDCl3): δ = 7.29–7.10 (m, 7.6 H), 6.47–6.43 (m,
1.9 H), 6.15 (dd, J = 15.6, 6.4 Hz, 0.9 H), 5.68 (dd, J = 11.6, 9.2 Hz,
0.9 H), 4.56–4.50 (m, 0.9 H), 4.43–4.38 (m, 0.9 H), 3.93–3.86 (m,
1.9 H), 3.80–3.69 (m, 1.9 H), 2.10–2.02 (m, 1.9 H), 1.89–1.83 (m,
3.8 H), 1.68–1.59 (m, 1.9 H).
13C NMR (100 MHz, CDCl3): δ = 136.3, 135.9, 133.0, 132.8, 131.1,
130.4, 129.4, 128.4, 128.2, 127.8, 127.7, 125.3, 78.8, 74.1, 67.1, 67.0,
31.9, 31.4, 25.4, 24.9, 20.2.
HRMS: m/z [M+] calcd for C13H16O: 188.1201; found: 188.1198.
13C NMR (100 MHz, CDCl3): δ = 137.7, 137.4, 133.4, 133.2, 133.0,
131.1, 129.1, 128.7, 128.4, 127.9, 127.7, 126.4, 126.2, 126.0, 125.3,
123.7, 78.3, 73.8, 67.2, 67.1, 31.9, 31.3, 25.3, 24.9.
2-(3-Methylstyryl)tetrahydrofuran (3k)18
Yield: 25.2 mg (45%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.8; Rf = 0.50 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C12H13ClO: 208.0655; found: 208.0649.
1H NMR (400 MHz, CDCl3): δ = 7.24–7.03 (m, 7.2 H), 6.57–6.53 (m,
1.8 H), 6.19 (dd, J = 15.6, 6.4 Hz, 0.8 H), 5.69 (dd, J = 11.6, 8.8 Hz, 1 H),
4.69–4.64 (m, 1 H), 4.49–4.44 (m, 0.8 H), 3.99–3.93 (m, 1.8 H), 3.86–
3.75 (m, 1.8 H), 2.35 (s, 3.0 H), 2.33 (s, 2.4 H), 2.19–2.08 (m, 1.8 H),
2.02–1.89 (m, 3.6 H), 1.75–1.64 (m, 1.8 H).
2-(2-Chlorostyryl)tetrahydrofuran (3g)18
Yield: 33.5 mg (54%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.4; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.54–7.32 (m, 2.8 H), 7.26–7.13 (m,
2.8 H), 6.97 (d, J = 16.0 Hz, 0.4 H), 6.69 (d, J = 12.0 Hz, 1 H), 6.20 (dd,
J = 15.6, 6.4 Hz, 0.4 H), 5.81 (dd, J = 11.6, 9.2 Hz, 1 H), 4.54–4.45 (m,
1.4 H), 3.99–3.91 (m, 1.4 H), 3.88–3.74 (m, 0.4 H),3.79–3.74 (m, 1 H),
2.19–2.04 (m, 1.4 H), 2.00–1.86 (m, 2.8 H), 1.75–1.65 (m, 1.4 H).
13C NMR (100 MHz, CDCl3): δ = 138.0, 137.7, 136.8, 136.7, 132.7,
131.5, 130.6, 130.3, 129.6, 128.4, 128.3, 128.1, 127.9, 127.2, 125.9,
123.6, 79.7, 75.1, 68.2, 68.1, 33.0, 32.4, 26.4, 25.9, 21.5, 21.4.
HRMS: m/z [M+] calcd for C13H16O: 188.1201; found: 188.1196.
13C NMR (100 MHz, CDCl3): δ = 133.9, 132.9, 132.6, 132.4, 132.0,
129.8, 128.6, 128.3, 127.7, 127.6, 127.5, 125.9, 125.7, 125.6, 125.3,
78.5, 73.9, 67.2, 67.1, 31.8, 31.3, 28.7, 25.4, 24.9.
2-(4-Methoxystyryl)tetrahydrofuran (3l)18
Yield: 37.2 mg (61%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.9; Rf = 0.40 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C12H13ClO: 208.0655; found: 208.0650.
1H NMR (400 MHz, CDCl3): δ = 7.25–7.17 (m, 3.8 H), 6.82–6.76 (m,
3.8 H), 6.47–6.44 (m, 1.8 H), 5.99 (dd, J = 15.6, 6.8 Hz, 0.9 H), 5.55 (dd,
J = 11.6, 8.8 Hz, 1 H), 4.62–4.56 (m, 1 H), 4.40–4.34 (m,0.9 H), 3.92–
3.86 (m, 1.9 H), 3.80–3.69 (m, 7.6 H), 2.11–2.00 (m, 1.9 H), 1.94–1.83
(m, 3.8 H), 1.66–1.61 (m, 1.9 H).
2-(4-Bromostyryl)tetrahydrofuran (3h)18
Yield: 46.4 mg (61%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.7; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.39–7.34 (m, 3.4 H), 7.19–7.09 (m,
3.4 H), 6.47–6.43 (m, 1.7 H), 6.13 (dd, J = 16.0, 6.8 Hz, 0.7 H), 5.66 (dd,
J = 11.6, 9.2 Hz, 1 H), 4.54–4.48 (m, 0.7 H), 4.41–4.36 (m, 0.7 H), 3.91–
3.83 (m, 1.7 H), 3.72–3.67 (m, 1.7 H), 2.09–1.87 (m, 1.7 H), 1.97–1.82
(m, 3.4 H), 1.70–1.56 (m, 1.7 H).
13C NMR (100 MHz, CDCl3): δ = 159.2, 158.8, 131.3, 131.2, 130.2,
130.1, 129.4, 128.9, 128.3, 127.7, 113.9, 113.6, 79.9, 75.2, 68.1, 68.0,
55.3, 55.2, 33.0, 32.5, 26.4, 26.0.
HRMS: m/z [M+] calcd for C13H17O2: 204.1150; found: 204.1148.
13C NMR (100 MHz, CDCl3): δ = 135.8, 135.6, 133.6, 131.6, 131.4,
131.3, 130.5, 129.2, 128.0, 121.2, 121.1, 79.5, 74.9, 68.3, 68.1, 32.9,
32.3, 26.4, 25.9.
2-(2-Methoxystyryl)tetrahydrofuran (3m)18
Yield: 32.9 mg (54%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.5; Rf = 0.40 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C12H13BrO: 252.0150; found: 252.0147.
1H NMR (400 MHz, CDCl3): δ = 7.45–7.43 (m, 0.5 H), 7.33–7.18 (m,
2 H), 6.95–6.84 (m, 4 H), 6.73–6.70 (d, J = 11.2 Hz, 1 H), 6.22 (dd, J =
16.0, 6.8 Hz, 0.5 H), 5.72 (dd, J = 11.6, 9.2 Hz, 1 H), 4.60–4.54 (m, 1 H),
4.47 (q, J = 13.6, 6.8, 0.5 H), 3.97–3.74 (m, 7.5 H), 2.11–2.05 (m, 1.5 H),
2.01–1.89 (m, 3 H), 1.72–1.68 (m, 1.5 H).
2-(2-Bromostyryl)tetrahydrofuran (3i)18
Yield: 44.8 mg (59%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.1; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.50–7.48 (m, 1.1 H), 7.32–7.29 (m,
1.1 H), 7.23–7.19 (m, 1.1 H), 7.09–7.02 (m, 1.1 H), 6.85 (d, J = 15.6 Hz,
0.1 H), 6.55 (d, J = 11.2 Hz, 1 H), 6.08 (dd, J = 15.6, 6.4 Hz, 0.1 H), 5.73–
5.68 (m, 1 H), 4.41–4.36 (m, 1.1 H), 3.89–3.84 (m, 1.1 H), 3.72–3.67
(m, 1.1 H), 2.04–1.78 (m, 3.3 H), 1.63–1.58 (m, 1.1 H).
13C NMR (100 MHz, CDCl3): δ = 136.8, 136.7, 133.7, 133.6, 132.9,
132.5, 131.0, 130.9, 129.3, 128.8, 127.5, 127.4, 127.3, 127.1, 127.0,
123.9, 79.5, 75.0, 68.3, 68.2, 32.8, 32.4, 26.4, 25.9.
13C NMR (100 MHz, CDCl3): δ = 156.0, 155.7, 131.4, 130.0, 129.9,
129.4, 127.8, 127.7, 127.5, 126.3, 125.9, 124.8, 124.6, 124.5, 119.5,
119.1, 109.8, 109.2, 79.2, 74.3, 67.1, 67.0, 54.4, 54.3, 31.8, 31.4, 25.4,
25.0.
HRMS: m/z [M+] calcd for C13H17O2: 204.1150; found: 204.1147.
Methyl 2-[2-(Tetrahydrofuran-2-yl)vinyl]benzoate (3n)18
Yield: 23.8 mg (34%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.2; Rf = 0.40 (PE/EtOAc, 7:1).
HRMS: m/z [M+] calcd for C12H13BrO: 252.0150; found: 252.0148.
1H NMR (400 MHz, CDCl3): δ = 7.97–7.95 (m, 1 H), 7.87–7.85 (m,
0.2 H), 7.58–7.32 (m, 3.6 H), 7.07 (d, J = 11.6 Hz, 1 H), 6.11 (dd, J =
16.0, 6.8 Hz, 0.2 H), 5.73 (dd, J = 11.6, 9.6 Hz, 1 H), 4.52 (q, J = 13.6,
6.8 Hz, 0.2 H), 4.41–4.35 (m, 1 H), 3.97–3.71 (m, 6 H), 2.03–1.82 (m,
3.6 H), 1.72–1.61 (m, 1.2 H).
13C NMR (100 MHz, CDCl3): δ = 167.9, 167.5, 138.7, 138.2, 133.4,
132.0, 131.8, 131.6, 131.1, 130.5, 130.4, 129.3, 129.1, 127.5, 127.4,
127.2, 127.1, 79.6, 75.1, 68.2, 68.1, 52.1, 52.0, 32.9, 32.3, 26.4, 25.9.
2-(4-Methylstyryl)tetrahydrofuran (3j)18
Yield: 30.8 mg (55%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.6; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.21–7.02 (m, 6.4 H), 6.50–6.46 (m,
1.6 H), 6.11–6.05 (m, 0.6 H), 5.59 (dd, J = 11.2, 8.8 Hz, 1 H), 4.60 (q, J =
15.2, 7.6 Hz, 1 H), 4.38 (q, J = 13.6, 6.8 Hz, 0.6 H), 3.92–3.86 (m, 1.6 H),
3.79–3.68 (m, 1.6 H), 2.27 (s, 3.0 H), 2.25 (s, 1.8 H), 2.10–2.00 (m,
1.8 H), 1.93–1.83 (m, 3.2 H), 1.65–1.60 (m, 1.6 H).
HRMS: m/z [M+] calcd for C14H16O3: 232.1099; found: 232.1095.
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[2-(Naphthalen-2-yl)vinyl]tetrahydrofuran (3o)18
IR (neat): 3055, 3023, 2971, 2866, 1722, 1599, 1492, 1445, 1242,
1178, 1049, 921, 876, 765, 689 cm–1
.
Yield: 28.8 mg (43%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.7; Rf = 0.50 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.45–6.84 (m, 14 H), 6.67 (s, 1 H), 6.61
(s, 0.4 H), 4.90 (dd, J = 8.0, 6.8 Hz, 1 H), 4.64–4.60 (m, 0.4 H), 3.81–
3.68 (m, 2.8 H), 3.73–3.68 (m, 2.8 H), 1.93–1.57 (m, 5.6 H).
13C NMR (100 MHz, CDCl3): δ = 143.1, 142.4, 141.3, 139.0, 137.0,
136.8, 133.1, 131.6, 129.3, 129.3, 129.1, 128.8, 128.6, 128.4, 128.2,
127.9, 127.8, 127.2, 127.0, 126.5, 125.8, 83.6, 77.0, 68.7, 68.3, 31.1,
30.6, 26.7, 25.8.
1H NMR (400 MHz, CDCl3): δ = 7.84–7.73 (m, 6.8 H), 7.62–7.59 (m,
0.7 H), 7.48–7.43 (m, 3.4 H), 6.77–6.73 (m, 1.7 H), 6.34 (dd, J = 15.6,
6.4 Hz, 0.7 H), 5.79 (dd, J = 11.6, 9.2 Hz, 1 H), 4.75 (q, J = 15.2, 7.6 Hz,
1 H), 4.53 (q, J = 13.6, 6.8 Hz, 0.7 H), 4.02–3.96 (m, 1.7 H), 3.90–3.78
(m, 1.7 H), 2.22–2.14 (m, 1.7 H), 2.05–1.93 (m, 3.4 H), 1.79–1.68 (m,
1.7 H).
13C NMR (100 MHz, CDCl3): δ = 133.3, 133.2, 132.2, 132.2, 131.9,
131.4, 130.5, 129.9, 129.6, 127.8, 127.1, 127.0, 126.9, 126.7, 126.6,
126.6, 126.0, 125.4, 125.2, 125.1, 124.9, 124.8, 122.6, 78.7, 74.2, 67.2,
67.1, 32.0, 31.4, 25.4, 24.9.
HRMS: m/z [M+] calcd for C18H18O: 250.1360; found: 250.1358.
2-(1,2-Di-p-tolylvinyl)tetrahydrofuran (3t)
Yield: 35.7 mg (43%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.4; Rf = 0.3 (PE/EtOAc, 50:1).
HRMS: m/z [M+] calcd for C16H16O: 224.1201; found: 224.1200.
IR (neat): 2960, 2922, 2864, 1698, 1606, 1562, 1511, 1454, 1262,
2-[(E)-2-(Tetrahydrofuran-2-yl)ethenyl]pyridine (3p)18
Yield: 13.0 mg (25%); pale-yellow oil; Rf = 0.30 (PE/EtOAc, 3:1).
1H NMR (400 MHz, CDCl3): δ = 8.55 (d, J = 4.0 Hz, 1 H), 7.62 (dt, J = 8.6,
2 Hz, 1 H), 7.28 (d, J = 8.0 Hz, 1 H), 7.12 (dd, J = 5.2, 1.6 Hz, 1 H), 6.76–
6.65 (m, 2 H), 4.60–4.55 (m, 1 H), 3.99 (dd, J = 14.4, 7.6 Hz, 1 H), 3.86
(dd, J = 14.0, 7.6 Hz, 1 H), 2.19–2.12 (m, 1 H), 2.02–1.91 (m, 2 H),
1.81–1.75 (m, 1 H).
1048, 965, 886, 817, 730, 666 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 7.41–6.83 (m, 11.2 H), 6.70 (s, 1 H),
6.62 (s, 0.4 H), 4.97 (dd, J = 8.4, 6.4 Hz, 1 H), 4.67–4.64 (m, 0.4 H),
3.93–3.75 (m, 2.8 H), 2.36 (s, 7.2 H), 2.23 (s, 1.2 H), 1.89–1.76 (m,
4.2 H), 1.71–1.65 (m, 1.4 H).
13C NMR (100 MHz, CDCl3): δ = 142.1, 141.6, 138.5, 136.7, 136.6,
136.1, 136.1, 134.2, 134.0, 132.8, 131.3, 129.3, 129.1, 129.1, 129.0,
128.7, 128.6, 128.6, 125.5, 83.7, 68.7, 68.3, 31.1, 30.6, 26.7, 25.8, 21.2,
21.2.
13C NMR (100 MHz, CDCl3): δ = 155.3, 149.5, 136.5, 135.3, 129.5,
122.1, 121.8, 79.0, 68.3, 32.2, 25.8.
HRMS: m/z [M+] calcd for C11H13NO: 175.0997; found: 175.0998.
HRMS: m/z [M+] calcd for C20H22O: 278.1671; found: 278.1671.
2-Styryl-1,3-dioxolane (5a)18
2-[3-(Tetrahydrofuran-2-yl)allyloxy]benzaldehyde (3q)
Yield: 31.0 mg (50%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.6; Rf = 0.30 (PE/EtOAc, 5:1).
Yield: 29.1 mg (55%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.6; Rf = 0.60 (PE/EtOAc, 10:1).
1H NMR (400 MHz, CDCl3): δ = 7.46–7.27 (m, 8.0 H), 6.84–6.76 (m,
1.6 H), 6.19–6.14 (m, 0.6 H), 5.75–5.70 (m, 1 H), 5.52 (d, J = 7.6 Hz,
1 H), 5.43 (d, J = 6.0 Hz, 0.6 H), 4.09–4.05 (m, 3.2 H), 3.98–3.91 (m,
3.2 H).
13C NMR (100 MHz, CDCl3): δ = 135.8, 135.7, 134.9, 129.0, 128.6,
128.4, 128.3, 127.8, 127.7, 127.0, 126.6, 125.1, 103.9, 99.7, 65.2, 65.1.
IR (neat): 2925, 2862, 1725, 1686, 1599, 1482, 1456, 1390, 1286,
1238, 1190, 1161, 1104, 1047, 1011, 969, 841, 810, 757, 650 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 10.53 (s, 1 H), 10.50 (s, 0.6 H), 7.85–
7.51 (m, 6.4 H), 5.95–5.74 (m, 3.2 H), 4.81 (d, J = 6.0 Hz, 1.6 H), 4.66 (d,
J = 4.4 Hz, 1.6 H), 4.31 (t, J = 6.8 Hz, 1.6 H), 3.97–3.90 (m, 1.6 H), 3.84–
3.78 (m, 1.6 H), 2.10–2.06 (m, 1.6 H), 1.97–1.90 (m, 3.2 H), 1.67–1.63
(m, 1.6 H).
13C NMR (100 MHz, CDCl3): δ = 189.9, 161.0, 160.9, 135.9, 134.9,
130.9, 128.8, 128.4, 126.0, 125.0, 124.9, 120.8, 112.8, 78.7, 75.1, 68.3,
68.2, 65.6, 64.7, 32.7, 32.1, 26.0, 25.8.
HRMS: m/z [M+] calcd for C11H12O2: 176.0837; found: 176.0839.
2-(4-Methylstyryl)-1,3-dioxolane (5b)18
Yield: 26.8 mg (47%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.3; Rf = 0.60 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C14H16O3: 232.1099; found: 232.1102.
1H NMR (400 MHz, CDCl3): δ = 7.32–7.12 (m, 5.2 H), 6.80–6.71 (m,
1.3 H), 6.11 (dd, J = 10.0, 8.4 Hz, 0.3 H), 5.68 (dd, J = 11.6, 7.6 Hz, 1 H),
5.53 (d, J = 7.2 Hz, 1 H), 5.42 (d, J = 6.4 Hz, 0.3 H), 4.08–4.04 (m, 2.6 H),
3.96–3.90 (m, 2.6 H), 2.39 (s, 0.9 H), 2.35 (s, 3 H).
2-(1-Phenylprop-1-en-2-yl)tetrahydrofuran (3r)18
Yield: 29.1 mg (52%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.8; Rf = 0.60 (PE/EtOAc, 7:1).
1H NMR (400 MHz, CDCl3): δ = 7.26–7.15 (m, 5.4 H), 7.12–7.09 (m,
3.6 H), 6.47–6.38 (m, 1.8 H), 4.68–4.64 (m, 1 H), 4.33–4.29 (m, 0.8 H),
3.95–3.63 (m, 3.6 H), 2.07–1.99 (m, 0.8 H), 1.95–1.83 (m, 4.6 H), 1.80
(d, J = 1.6 Hz, 3 H), 1.77 (d, J = 1.2 Hz, 2.4 H), 1.75–1.67 (m, 1.8 H).
13C NMR (100 MHz, CDCl3): δ = 138.8, 138.6, 137.9, 137.5, 129.0,
128.7, 128.3, 128.0, 128.0, 126.4, 126.2, 124.5, 84.0, 68.7, 31.0, 30.5,
26.9, 26.1, 17.9, 14.0.
13C NMR (100 MHz, CDCl3): δ = 138.3, 137.7, 135.7, 134.9, 133.0,
132.9, 129.9, 129.0, 126.9, 126.6, 125.0, 124.0, 104.1, 99.8, 65.2, 65.1,
21.3, 21.2.
HRMS: m/z [M+] calcd for C12H14O2: 190.0994; found: 190.0997.
2-(4-Chlorostyryl)-1,3-dioxolane (5c)18
Yield: 27.1 mg (43%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.8; Rf = 0.60 (PE/EtOAc, 10:1).
HRMS: m/z [M+] calcd for C13H16O: 188.1201; found: 188.1202.
1H NMR (400 MHz, CDCl3): δ = 7.28–7.19 (m, 7.2 H), 6.70–6.64 (m,
1.8 H), 6.07 (dd, J = 16.0, 6.0 Hz, 0.8 H), 5.67 (dd, J = 11.6, 7.6 Hz, 1 H),
5.39 (d, J = 7.6 Hz, 1 H), 5.35 (d, J = 6.0 Hz, 0.8 H), 4.00–3.99 (m, 3.6 H),
3.91–3.86 (m, 3.6 H).
2-(1,2-Diphenylvinyl)tetrahydrofuran (3s)
Yield: 24.1 mg (32%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.4; Rf = 0.30 (PE/EtOAc, 50:1).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

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M. Zhang et al.
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13C NMR (100 MHz, CDCl3): δ = 134.4, 134.3, 134.1, 134.1, 133.8,
133.5, 130.3, 128.8, 128.5, 128.4, 128.1, 125.8, 103.6, 99.5, 66.2, 65.1.
HRMS: m/z [M+] calcd for C11H11ClO2: 210.0448; found: 210.0045.
(5) Reviews of palladium-catalyzed cross-coupling reactions:
(a) Jana, R.; Pathak, T. P.; Sigman, M. S. Chem. Rev. 2011, 111,
1417. (b) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147.
(c) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(6) Reviews of transition-metal-catalyzed direct carbon–hydrogen
bond functionalization: (a) Miao, J. M.; Ge, H. B. Eur. J. Org.
Chem. 2015, 7859. (b) Huang, Z. X.; Lim, H. N.; Mo, F. Y.; Young,
M. C.; Dong, G. B. Chem. Soc. Rev. 2015, 44, 7764. (c) Arockiam, P.
B.; Bruneau, C.; Dixneuf, P. H. Chem. Rev. 2012, 112, 5879.
(7) C–C bond formation through radical coupling and radical addi-
tion reactions: (a) Qian, Q.; Zang, Z. H.; Chen, Y.; Tong, W. Q.;
Gong, H. G. Mini-Rev. Med. Chem. 2013, 13, 802. (b) Ueda, M.
Chem. Pharm. Bull. 2014, 62, 845.
(8) Reactions of cyclic ethers as nucleophilic radical precursors:
(a) Jin, J.; MacMillan, D. W. C. Angew. Chem. Int. Ed. 2015, 54,
1565. (b) Okugawa, N.; Moriyama, K.; Togo, H. Eur. J. Org. Chem.
2015, 4973. (c) Sun, K.; Wang, X.; Li, G.; Zhu, Z. H.; Jiang, Y. Q.;
Xiao, B. B. Chem. Commun. 2014, 50, 12880. (d) Li, X.; Wang, H.-
Y.; Shi, Z.-J. New J. Chem. 2013, 37, 1704. (e) Hasegawa, M.; Ishii,
H.; Cao, Y.; Fuchigami, T. J. Electrochem. Soc. 2006, 153, D162.
(f) Minisci, F. Synthesis 1973, 1.
2-(4-Butylstyryl)-1,3-dioxolane (5d)
Yield: 35.5 mg (51%); pale-yellow oil; mixture of cis/trans isomers,
E/Z = 0.3; Rf = 0.60 (PE/EtOAc, 10:1).
IR (neat): 2957, 2927, 2869, 1727, 1678, 1610, 1565, 1510, 1461,
1379, 1343, 1115, 1044, 946, 846, 813, 621 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 7.26–7.03 (m, 5.2 H), 6.73–6.65 (m,
1.3 H), 6.07–6.01 (m, 0.3 H), 5.62–5.57 (m, 1 H), 5.47 (d, J = 7.6 Hz,
1 H), 5.34 (d, J = 6.0 Hz, 0.3 H), 4.01–3.96 (m, 2.6 H), 3.91–3.83 (m,
2.6 H), 2.59–2.50 (m, 2.6 H), 1.52–1.50 (m, 2.6 H), 1.31–1.26 (m,
2.6 H), 0.88–0.83 (m, 3.9 H).
13C NMR (100 MHz, CDCl3): δ = 135.7, 133.1, 131.6, 129.2, 129.0,
128.6, 128.3, 127.8, 126.8, 126.6, 125.1, 124.0, 104.1, 99.8, 65.3, 65.2,
35.7, 35.4, 33.5, 33.3, 22.4, 22.3, 14.0, 13.9.
HRMS: m/z [M+] calcd for C15H20O2: 232.1463; found: 232.1467.
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Acknowledgment
This work was supported by the National Natural Science Foundation
of China (Nos. 21572203 and J1210042) and Zhejiang Provincial Natu-
ral Science Foundation (LZ16B020001).
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0036-1588909.
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(10) Huang, L.; Cheng, K.; Yao, B.; Zhao, J.; Zhang, Y. Synthesis 2009,
3504.
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2014, 55, 6096.
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