Nucleophilic Organic Base DABCO-Mediated Chemospecific Meinwald Rearrangement of Terminal Epoxides into Methyl Ketones

Article abstract of DOI:10.1021/acs.joc.8b03171

Nucleophilic organic base DABCO (1,4-diazabicyclo[2.2.2]octane)-mediated Meinwald rearrangement of various epoxides was investigated. 2-Aryl-, alkenyl-, and alkynylepoxides generate the corresponding methyl ketones chemospecifically in good to excellent yields. The current DABCO-mediated Meinwald rearrangement of epoxides features readily accessible starting materials, a wide substrate scope, a transition-metal- and acid-free environment, and chemospecificity in the isomerization of epoxides.

Full text of DOI:10.1021/acs.joc.8b03171

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Note
Nucleophilic Organic Base DABCO-Mediated Chemospecific
Meinwald Rearrangement of Terminal Epoxides into Methyl Ketones
Siqi Li, Yi Shi, Pingfan Li, and Jiaxi Xu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b03171 • Publication Date (Web): 26 Feb 2019
Downloaded from http://pubs.acs.org on February 27, 2019
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The Journal of Organic Chemistry
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Nucleophilic Organic Base DABCO-Mediated Chemospecific Meinwald
Rearrangement of Terminal Epoxides into Methyl Ketones
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Siqi Li, Yi Shi, Pingfan Li*, Jiaxi Xu*
State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science, Beijing
University of Chemical Technology, Beijing 100029, People’s Republic of China.
Supporting Information
ABSTRACT: Nucleophilic organic base DABCO (1,4-diazabicyclo[2.2.2]octane)-mediated Meinwald rearrangement of various
epoxides was investigated. 2-Aryl, alkenyl, and alkynylepoxides generate the corresponding methyl ketones chemospecifically in
good to excellent yields. The current DABCO-mediated Meinwald rearrangement of epoxides features readily accessible starting
materials, wide substrate scope, transition metal and acid-free environment, and chemospecificity in the isomerization of epoxides.
Epoxides are readily available and important intermediates in
organic synthesis.1 They undergo the nucleophilic ring-opening
reactions to generate 2-hydroxyalkylated derivatives,1,2 the
acid-catalyzed rearrangements to yield carbonyl compounds,1a
and strong base-promoted isomerization to give rise to allylic
alcohols.3 The isomerization of epoxides into carbonyl com-
pounds is well known as the Meinwald rearrangement or Mein-
wald reaction.4 The acid-catalyzed, including various protonic
and Lewis acids, Meinwald rearrangements of epoxides have
been widely investigated,5 in which terminal epoxides generate
the corresponding aldehydes as sole or major products (Scheme
1, a),6 companied with methyl ketones as byproducts in some
cases,6d,6e while internal epoxides generally afford the corre-
sponding ketones with aldehydes as side products in certain re-
actions,7 especially for aryl epoxides.8 Occasionally, aldehydes
are obtained as major products.9 To realize the isomerization of
terminal epoxides into the corresponding methyl ketones (the
inverse selectivity from that in the acid-catalyzed rearrange-
ments), some transition metal catalysts10 and Lewis acid-nucle-
ophilic metal systems with (transition) metal-organic ligand
complexes have been designed and applied in the Meinwald re-
arrangement of terminal epoxides (Scheme 1, b).11 2-Al-
kylepoxides were converted into the desired methyl ketones
chemospecifically in good yields. However, 2-arylepoxides
generated the desired acetophenones with arylethanals as by-
products in most cases. The isomerization is very attractive in
organic synthesis because it could be an alternative to Wacker
oxidation by a two step epoxidation-Meinwald rearrangement
sequence for Lewis acid-sensitive olefins and displace the se-
quence of methyl-Grignard reagent addition-alcohol oxidation
after the combination with the Corey-Chaychovsky epoxidation
for nonoxidation transformation of aldehydes into methyl ke-
tones. After carefully considering and analyzing the mechanism
of the Meinwald rearrangement,1a,5 we designed an organic
base-mediated Meinwald rearrangement. Nucleophilic tertiary
or aromatic organic bases can serve as nucleophiles to open
epoxides at their more electrophilic ring carbon atom (usually
less substituted one)2 to generate zwitterionic intermediates,
which undergo a 1,2-hydride-shift with loss of the organic base
(similar to an intramolecular substitution) to afford the desired
methyl ketones because the organic bases can work as leaving
groups in the zwitterionic intermediates as well (Scheme 1, c).
In continuation of our interest in the synthetic application of
small heterocycles,12 herein, we present our nucleophilic or-
ganic base DABCO-mediated chemospecific Meinwald rear-
rangement of various nonalkyl terminal epoxides into the cor-
responding methyl ketones in good yields. The current strategy
is a mild basic, metal-free, and chemospecific isomerization of
nonalkyl terminal epoxides into methyl ketones. It is a good
complement for the Meinwald rearrangement, especially for
Lewis acid-nucleophilic metal systems. The current method can
be applied in the acid-sensitive epoxides.
Scheme 1. Rearrangement of terminal epoxides to carbonyl
compounds. a) Lewis acid-catalyzed rearrangement; b)
Costes and Kunz’s work; c) This work: Organic base-medi-
ated rearrangement.
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only the reaction with DMAP as a base produced product 2a in
Page 2 of 9
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8% yield (Table 1, entries 9-18). Strong organic nucleophile
PPh3 was test. However, it was inefficient (Table 1, entry 19).
The results indicate that DABCO is an efficient base for the
isomerization due to its strong nucleophilicity. According to the
nucleophilicity scale described by Mayr and coworkers,13
DABCO is a much more potent nucleophile than other organic
amines tested. This could explain its exceptional performance
in this reaction. Solvent evaluation revealed that mesitylene was
the best choice (Table 1, entries 8, 20, and 21). Lengthening the
time to 24 h had a positive influence on the yield, the product
2a was isolated in an excellent yield of 91% (Table 1, entry 22)
(Method A). Decreasing the amount of DABCO to 1.5 to 1.0 to
0.5 equivalents gave lower yields of 79%, 63%, and 47%, re-
spectively (Table 1, entries 23-25). Raising the reaction temper-
ature to 165 C (refluxing conditions) resulted in a slightly de-
creased yield (Table 1, entry 26).
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Table 1. Optimization of base-mediated reaction conditionsa
Solvent
Time
h
Yieldb
%
Base
equiv.
Entry
Base.
1
TEA
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Me3C6H3
Me3C6H3
Me3C6H3
Me3C6H3
Me3C6H3
Me3C6H3
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
NRc
NRc
NRd
58d
NRe
65e
NR
80
2
DABCO
TEA
3
4
DABCO
TEA
5
6
DABCO
TEA
7
8
DABCO
Py
9
NR
NR
NR
NR
8
To avoid the existence of a protonic acid and to extend the
scope of substrates, we directly selected acid-sensitive 2-
styrylepoxide (1a) as a model substrate to react with tertiary or
aromatic organic amine bases under thermal conditions.
Stoichiometric amount of organic amines can rule out the
possible involvement of a trace amount of acid from silica
borate glassware’s residue acidic sites. We started our optimi-
zation with 2-styrylepoxide (1a) and two representative tertiary
organic bases TEA (triethylamine) and DABCO (1,4-diazabi-
cyclo[2.2.2]octane). When 2-styrylepoxide (1a) and 2 equiva-
lents of TEA were stirred in anhydrous toluene at 40 C, 80 C,
and 100 C for 12 hrs, no reaction occurred (Table 1, entries 1,
3 and 5). However, the reaction of 2-styrylepoxide (1a) and 2
equivalents of DABCO produced the desired product 4-phenyl-
but-3-en-2one (2a) in 58% and 65% yields, respectively, at 80
C and 100 C for 12 hrs (Table 1, entries 4 and 6). The yield
was further improved to 80% when 2-styrylepoxide (1a) and
DABCO were stirred in anhydrous mesitylene (Me3C6H3) at
130 C for 12 hrs (Table 1, entry 8). However, triethylamine
was still not efficient at 130 C (Table 1, entry 7). Furthermore,
a number of organic amine bases, including pyridine (Py), 2-
chloropyridine (2-ClPy), 4-methylpyridine (4-MePy), 2,6-di-
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16
2-ClPy
4-MePy
2,6-Me2Py
DMAP
N-MeIm
DIPEA
Me3C6H3
Me3C6H3
Me3C6H3
NR
NR
NR
4-Memor-
pholine
17
18
19
20
21
22
23
24
25
26
Morpholine 2
Me3C6H3
Me3C6H3
Me3C6H3
ClC6H5
12
12
12
12
12
24
24
24
24
24
NR
NR
NR
59
HMTA
2
PPh3
2
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
2
2
DMSO
Mess
91
2
Me3C6H3
Me3C6H3
Me3C6H3
Me3C6H3
Me3C6H3
1.5
1
79
63
0.5
47
86f
2
methylpyridine
(2,6-Me2Py),
4-(dimethylamino)pyridine
a Unless otherwise specified, reactions were performed on a 0.5
mmol scale at 130 C. b Isolated yield. c Reaction was conducted
(DMAP), N-methylimidazole (N-MeIm), N-ethyl-N-iso-
propylpropan-2-amine (DIPEA), 4-methylmorpholine, mor-
pholine, and hexamethylenetetramine (HMTA), was screened,
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at 40 C. d Reaction was conducted at 80 C. e Reaction was
conducted at 100 °C. f Reaction was conducted at 165 C.
yield (Table 1, entry 4), we hope to decrease the reaction tem-
1
2
3
4
5
6
7
8
perature with the assistance of Lewis acids to activate the epox-
ides. We evaluated many weak acidic Lewis acids as catalysts
for the DABCO-mediated reaction at 80 C, including MgSO4,
Mg(ClO4)2, MgI2, LiOAc·2H2O, LiCl, LiBr, SnCl2·2H2O,
Sc(OTf)3, MnSO4·H 2O, AgOAc, AgNO3, FeCl2·7H2O, FeCl3,
Fe(NO3)3·9H2O, CoCl2·2H2O, CeCl3·7H2O, CuSO4·5H2O,
CuBr, Cu(OAc)2, Cu(SO4)2, Cu(OTf)2, CuBr2, and CuCl2·2H2O
(Table 2). After all these attempts, Mg(ClO4)2, MgI2,
SnCl2·2H2O, MnSO4·H 2O, CeCl3·7H2O, Cu(SO4)2, CuBr, and
CuCl22H2O can improve the yield (Table 2, entries 3, 4, 8, 10,
17, 21, 23, and 24). The others decreased the yield possibly due
to strong conjunction between the Lewis acids and base
DABCO. The conjunction not only quenched the Lewis acid,
but also decreased the amount of free DABCO, resulting in the
decrease of the yield. CuCl2·2H2O was chosen as the best cata-
lyst due to its cheaper price. Both increasing and decreasing re-
action temperatures resulted in loss of the yield (Table 2, entries
27 and 28). Adjusting the amount of DABCO to 3 equivalents
and CuCl2·2H2O to 0.2 equivalent gave the best yield of 84%
(Table 2, entry 30) (Method B). The representative Lewis and
protonic acid-catalyzed conditions were evaluated as well.
However, no reaction was observed (Table 2, entries 31 and 32).
Table 2. Optimization of the Lewis acid-catalyzed base-medi-
ated reaction conditionsa
9
Entry
1
Catalyst (equiv.)
-
Yield (%)b
58
T (C)
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
90
70
80
80
80
80
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2
MgSO4 (0.2)
Mg(ClO4)2 (0.2)
MgI2 (0.2)
58
3
67
4
68
5
LiOAc.2H2O (0.2)
52
6
LiCl (0.2)
49
7
LiBr (0.2)
51
.
8
SnCl2 2H2O (0.2)
67
9
Sc(OTf)3 (0.2)
MnSO4H2O (0.2)
AgOAc (0.2)
59
With the optimal conditions (Method A) in hand,
substituted 2-styrylepoxides 1b−1e were treated with DABCO
in mesitylene at 130 C, the corresponding methyl ketones
2b−2e were isolated as sole products in good to excellent yields
with chemospecificity (Table 3, entries 2-5, Method A). To
extend the scope of substrates, 2-arylepoxides 1f−1o with both
electron-donating and electron-withdrawing substituents, as
well as 2-heteroarylepoxides 1p and 1q, were subjected to the
rection conditions, affording the desired products in satisfactory
to excellent yields (Table 3, entries 6-17, Method A). The
results indicates that 2-arylepoxides with electron-withdrawing
substituents generally gave the corresponding methyl ketones
in higher yields that those with electron-donating substituents
possibly because the electron-deficient aryls are favorable to
stabilize the generated alkoxide anions in the reactions (Scheme
1, c). The reaction was further extended to 2-alkynylepoxide 1r,
affording the desired methyl alkynyl ketone 2p in 42% yield
(Table 3, entry 18). However, alkyl substituted terminal
epoxides 2-butylepoxide (1s) and 2-dodecylepoxide (1t)
showed no reactivity under the reaction conditions (Table 3,
enmtries 19 and 20).
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31
32
67
33
AgNO3 (0.2)
38
.
FeCl2 7H2O (0.2)
56
FeCl3 (0.2)
Fe(NO3) .9H2O (0.2)
56
0
.
CoCl2 2H2O (0.2)
52
73
CeCl37H2O (0.2)
.
CuSO4 5H2O (0.2)
46
CuBr (0.2)
53
Cu(OAc)2 (0.2)
Cu(SO4)2 ( 0.2)
Cu(OTf)2 (0.2)
55
64
49
CuBr2 (0.2)
79
78
CuCl22H2O (0.2)
CuCl22H2O (0.1)
CuCl22H2O (0.3)
CuCl22H2O (0.2)
CuCl22H2O (0.2)
CuCl22H2O (0.2)
CuCl22H2O (0.2)
CuCl22H2O (0.2)
TsOHH2O (0.2)
71
The Lewis acid-catalyzed conditions were applied in the
isomerization reactions of epoxides 1a-1t at 80 C, the corre-
sponding methyl ketones 2a-2r were obtained in comparable
yields except for 1s and 1t (Table 3, Method B). Even under the
Lewis acid catalysis conditions, they did not work either.
74
58
45
59c
84d
0e,f
messe
Table 3. Scope of epoxides
a
Unless otherwise specified, 2 equiv of DABCO . b Isolated
yields; c 1.5 equiv of DABCO; d 3 equiv of DABCO. e Without
DABCO. f PhCH2CH=CHCHO generated in a trace amount.
Entry
1
Substrate
Product
Yielda in Method
(%)
Ab
Bc
Considering that the reaction temperature of 130 C is
somewhat high for certain thermally unstable epoxides in pos-
sible synthetic applications, and the fact that our DABCO-
mediated rearrangement works at 80 C with a relatively low
91
85
1a
2a
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Page 4 of 9
aYields are isolated yields. bMethod A: 1 (0.5 mmol) and
2
3
69
74
90
1
2
3
4
DABCO (112 mg, 1 mmol) in 2 mL of mesitylene were stirred
c
at 130 C for 24 hrs. Method B: 1 (0.5 mmol), DABCO (112
1b
.
2b
mg, 1 mmol), and CuCl2 2H2O (17 mg, 0.1 mmol) in 2 mL of
75
toluene were stirred at 80 C for 24 hrs.
5
6
7
8
1c
2c
2d
2e
Gram-scale preparations of methyl ketones 2a and 2f were
realized in 82% and 63% isolated yields, respectively (Scheme
2).
4
5
6
7
66
73
70
94
65
39
58
95
1d
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 2. Meinwald Rearrangement of Epoxides into Methyl
Ketones in Gram-Scale Reactions
1e
1f
2f
1g
2g
8
75
95
89
56
56
99
84
13
1h
1i
2h
9
In conclusion, we have realized nucleophilic organic base
DABCO-mediated Meinwald rearrangement of monosubsti-
tuted nonalkylepoxides under thermal conditions, specifically
affording methyl ketone products. Most Lewis acids can cata-
lyze the rearrangement at relatively low temperature, while
CeCl37H2O, CuBr2, and CuCl2·2H2O are efficient ones. Com-
pared with previously reported Meinwald rearrangements,
DABCO-mediated rearrangement can be metal-free, acid-free,
specific, and suitable for monosubstituted nonalkylepoxides.
Our current strategy can be taken as a complementary method
for the acid-catalyzed isomerization of epoxides.
2i
10
11
1j
2j
1k
2k
12
13
41
50
33
48
1l
2l
EXPERIMENTAL SECTION
General Information. Unless otherwise noted, all materials
were purchased from commercial suppliers. Reactions were
conducted in base-washed and flame-dried glassware under ni-
trogen atmosphere. Mesitylene was refluxed with sodium/ben-
zophenone, and freshly distilled prior to use. Flash column
chromatography was performed using silica gel (normal phase,
200300 mesh) from Qingdao Haiyang Chemical. Petroleum
ether used for column chromatography was 6090 C fraction,
and the removal of residue solvent was accomplished under ro-
tovap with repeated azeotrope with chloroform, and then evap-
oration under vacuum (< 1 mmHg pressure). Reactions were
monitored by thin-layer chromatography on silica gel 60-F254
coated 0.2 mm plates from Yantai Chemical Industry Institute.
The plates were visualized under UV light, as well as other TLC
stains (phosphomolybdic acid: 10% in ethanol; potassium per-
manganate: 1% in water; iodine: 10 g iodine absorbed on 30g
silica gel). 1H and 13C NMR spectra were recorded on a Bruker
400 MHz spectrometer, usually in CDCl3 with TMS as an inter-
nal standard, and the chemical shifts (δ) were reported in parts
per million (ppm). IR spectra (KBr pellets, v (cm−1)) were taken
on an FT-IR spectrometer. The high-resolution mass spectra
were obtained under ESI ionization using an LC/MSD TOF
mass spectrometer.
1m
2m
14
71
49
1n
1o
2n
2o
15
16
90
96
95
92
1p
1q
2p
2q
17
18
84
42
53
31
1r
1s
2r
2s
19
20
0
0
0
0
2t
1t
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General procedure for the DABCO-mediated Meinwald
137.3, 134.3, 130.6, 128.6, 128.2, 126.7, 52.0, 31.7, 31.7, 27.5,
1
2
3
4
5
6
7
8
rearrangement of epoxides 1. Method A. Epoxide 1 (0.5 mmol)
was dissolved in 2 mL of mesitylene in a 10 mL reaction tube.
DABCO (112 mg, 1.0 mmol) was added at room temperature,
and then the reaction mixture was heated at 130 C for 24 h.
After cooling to room temperature, the reaction mixture was di-
rectly subjected to flash column chromatography with ethyl ac-
etate/petroleum ether (1:50, v/v) to afford product 2.
22.4, 14.0.
1-Phenylethan-1-one (2f).16 Purified by flash column chro-
matography (PE/EA 50:1, v/v) on silica gel to give the desired
product as colorless oil, method A: 70 mg, 70% yield (from 0.83
mmol 1f), method B: 70 mg, 58% yield (from 0.5 mmol 1f). Rf
= 0.27, 5% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 8.02 – 7.92 (m, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.47 (dd,
J = 7.6 7.6, Hz, 2H), 2.61 (s, 3H). 13C{1H} NMR (101 MHz,
CDCl3) δ 198.1, 137.0, 133.0, 128.5, 128.2, 26.5.
1-(4-Chlorophenyl)ethan-1-one (2g).17 Purified by flash col-
umn chromatography (PE/EA 50:1, v/v) on silica gel to give the
desired product as colorless oil, method A: 145 mg, 94% yield
(from 1.0 mmol 1g), method B: 73 mg, 95% yield (from 0.5
Method B. Epoxide 1 (0.5 mmol) was dissolved with 2 mL of
toluene in a 10 mL reaction tube. DABCO (112 mg, 1.5 mmol)
and CuCl22H2O (17 mg, 0.1 mmol) were added at room tem-
perature, and then the reaction mixture was heated at 80 C for
24 h. After cooling to room temperature, the reaction mixture
was directly subjected to flash column chromatography with
ethyl acetate/ petroleum ether (1:50, v/v) to afford product 2.
(E)-4-Phenylbut-3-en-2-one (2a).14 Purified by flash column
chromatography (PE/EA 100:1, v/v) on silica gel to give the de-
sired product as red-brown oil, method A: 133 mg, 91% yield
(from 1.0 mmol 1a), method B: 62 mg, 85% yield (from 0.5
mmol 1a). Rf = 0.30, 5% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.57 – 7.47 (m, 3H), 7.42 – 7.35 (m,
3H), 6.71 (d, J = 16.3 Hz, 1H), 2.37 (s, 3H). 13C{1H} NMR (101
MHz, CDCl3) δ 198.3, 143.4, 134.4, 130.5, 128.9, 128.2, 127.1,
27.5.
(E)-4-(4-Chlorophenyl)but-3-en-2-one (2b).14 Purified by
flash column chromatography (PE/EA 50:1, v/v) on silica gel to
give the desired product as yellow oil, method A: 125 mg, 69%
yield (from 1.0 mmol 1b), method B: 81 mg, 90% yield (from
0.5 mmol 1b). Rf = 0.25, 5% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.50 – 7.43 (m, 3H), 7.40 – 7.35
(m, 2H), 6.69 (d, J = 16.3 Hz, 1H), 2.38 (s, 3H). 13C{1H} NMR
(101 MHz, CDCl3) δ 198.0, 141.8, 136.4, 132.9, 129.3, 129.2,
127.4, 27.6.
(E)-4-(2-Methoxyphenyl)but-3-en-2-one (2c).14 Purified by
flash column chromatography (PE/EA 50:1, v/v) on silica gel to
give the desired product as yellow oil, method A: 104 mg, 74%
yield (from 0.80 mmol 1c), method B: 40 mg, 75% yield (from
0.3 mmol 1c). Rf = 0.20, 5% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.89 (d, J = 16.4 Hz, 1H), 7.54
(dd, J = 7.6, 0.8 Hz, 1H), 7.39 – 7.35 (m, 1H), 6.97 (dd, J = 7.6,
7.6 Hz, 1H), 6.92 (d, J = 8.4 Hz, 1H), 6.75 (d, J = 16.8 Hz, 1H),
3.90 (s, 3H), 2.39 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ
199.1, 158.3, 138.7, 131.8, 128.3, 127.8, 123.4, 120.8, 111.1,
55.5, 27.1.
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1
mmol 1g). Rf = 0.38, 5% ethyl acetate in petroleum ether. H
NMR (400 MHz, CDCl3) δ 7.89 (d, J = 8.8 Hz, 2H), 7.38 (d, J
= 8.4 Hz, 2H), 2.59 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3)
δ 196.8, 139.5, 135.4, 129.7, 128.8, 26.5.
1-(4-Bromophenyl)ethan-1-one (2h).18 Purified by flash col-
umn chromatography (PE/EA 50:1, v/v) on silica gel to give the
desired product as white solid, method A: 75 mg, 75% yield.
(from 0.5 mmol 1h), method B: 56 mg, 56% yield (from 0.5
mmol 1h). M.p. 57–58 C (Lit.19 M.p. 52−53 C). Rf = 0.30,
1
6.67% ethyl acetate in petroleum ether. H NMR (400 MHz,
CDCl3) δ 7.82 (d, J = 8.5 Hz, 2H), 7.61 (d, J = 8.5 Hz, 2H), 2.59
(s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 197.0, 135.8, 131.9,
129.8, 128.3, 26.5.
4-Acetylbenzonitrile (2i).20 Purified by flash column chroma-
tography (PE/EA 50:1, v/v) on silica gel to give the desired
product as white solid, method A: 69 mg, 95% yield (from 0.5
mmol 2i), method B: 45 mg, 99% yield (from 0.3 mmol 1i). M.p.
60–63 C (Lit.21 M.p. 59−60 C). Rf = 0.14, 10% ethyl acetate
in petroleum ether. 1H NMR (400 MHz, CDCl3) δ 8.05 (d, J =
8.4 Hz, 2H), 7.79 (d, J = 8.4 Hz, 2H), 2.66 (s, 3H). 13C{1H}
NMR (101 MHz, CDCl3) δ 196.4, 139.8, 132.4, 128.6, 117.8,
116.3, 26.7.
1-(4-(Trifluoromethyl)phenyl)ethan-1-one (2j).20 Purified
by flash column chromatography (PE/EA 50:1, v/v) on silica gel
to give the desired product as yellow liquid, method A: 85 mg,
89% yield (from 0.5 mmol 1j), method B: 47 mg, 84% yield
(from 0.3 mmol 1j). Rf = 0.46, 6.67% ethyl acetate in petroleum
ether. 1H NMR (400 MHz, CDCl3) δ 8.05 (d, J = 8.0 Hz, 2H),
7.72 (d, J = 7.9 Hz, 2H), 2.63 (s, 3H). 13C{1H} NMR (101 MHz,
CDCl3) δ 196.9, 139.6, 134.4 (q, JC-F = 32.6 Hz), 128.6, 125.6
(q, JC-F = 3.8 Hz), 123.6 (q, JC-F = 272.8 Hz), 26.7. 19F NMR
(377 MHz, CDCl3) δ -63.14.
1-(4-Methoxyphenyl)ethan-1-one (2k).22 Purified by flash
column chromatography (PE/EA 50:1, v/v) on silica gel to give
the desired product as colorless oil, method A: 84 mg, 56 %
yield (from 1.0 mmol 1k), method B: 10 mg, 13% yield (from
0.5 mmol 1k). Rf = 0.18, 6.67% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.94 (d, J = 8.8 Hz, 2H), 6.93 (d,
J = 8.8 Hz, 2H), 3.87 (s, 3H), 2.56 (s, 3H). 13C{1H} NMR (101
MHz, CDCl3) δ 196.8, 163.5, 130.6, 130.3, 113.7, 55.5, 26.3.
1-(4-Methylphenyl)ethan-1-one (2l).20 Purified by flash col-
umn chromatography (PE/EA 50:1, v/v) on silica gel to give the
desired product as yellow liquid, method A: 41 mg, 41% yield
(from 0.75 mmol 1l), method B: 13 mg, 33% yield (from 0.3
mmol 1l). Rf = 0.37, 6.67% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.86 (d, J = 8.1 Hz, 2H), 7.26 (d, J
(E)-3-Methyl-4-phenylbut-3-en-2-one (2d).15 Purified by
flash column chromatography (PE/EA 50:1, v/v) on silica gel to
give the desired product as colorless oil, method A: 106 mg, 66%
yield (from 1.0 mmol 1d), method B: 31 mg, 65% yield (from
0.3 mmol 1d). Rf = 0.28, 5% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.52 (d, J = 1.2 Hz, 1H), 7.45-
7.40 (m, 4H), 7.36 – 7.32 (m, 1H), 2.47 (s, 3H), 2.06 (d, J = 1.2
Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 200.3, 139.6,
137.8, 135.9, 129.7, 128.5, 128.4, 25.8, 12.9.
(E)-3-Benzylideneoctan-2-one (2e).15 Purified by flash col-
umn chromatography (PE/EA 50:1, v/v) on silica gel to give the
desired product as yellow oil, method A: 129 mg, 73% yield
(from 0.82 mmol 1e), method B: 42 mg, 39% yield (from 0.5
1
mmol 1e). Rf = 0.18, 5% ethyl acetate in petroleum ether. H
NMR (400 MHz, CDCl3) δ 7.50 – 7.29 (m, 6H), 2.52 – 2.45 (m,
2H), 2.44 (s, 3H), 1.50 – 1.40 (m, 2H), 1.40 – 1.10 (m, 4H),
0.92-0.84 (m, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 200.3,
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The Journal of Organic Chemistry
Page 6 of 9
= 7.9 Hz, 2H), 2.58 (s, 3H), 2.41 (s, 3H). 13C{1H} NMR (101 Chaykovsky reaction.27 Sodium hydride (0.9 g, 22.5 mmol, 60%
1
2
3
4
5
6
7
8
MHz, CDCl3) δ 197.8, 143.9, 134.7, 129.2, 128.4, 26.5, 21.6.
mineral oil dispersion) was washed with petroleum ether (3  5
mL). The residual petroleum ether was removed under vacuum.
Under atmosphere of nitrogen, dry THF (15 mL) and dry
DMSO (15 mL) were added and the reaction mixture was
cooled in an ice bath. A solution of trimethylsulfonium iodide
(3.67 g, 18 mmol) in DMSO (4 mL) was added. After addition,
cinnamyl aldehyde (1.98 g, 15 mmol) was added in one portion.
The reaction mixture was stirred at 0 C for 30 min and at room
temperature for an additional 12 h. The reaction mixture was
slowly quenched with a mixture of water and ice (20 mL) and
extracted with methylene chloride (3  10 mL). The combined
organic extracts were washed with brine (2  30 mL), dried over
sodium sulfate, filtered. The reaction mixture was directly sub-
jected to flash column chromatography with ethyl acetate/pe-
troleum ether (1:25, v/v) to give (E)-2-styryloxirane (1a)
1-([1,1'-Biphenyl]-4-yl)ethan-1-one (2m).23 Purified by
flash column chromatography (PE/EA 50:1, v/v) on silica gel to
give the desired product as yellow solid, method A: 50 mg, 50%
yield (from 0.5 mmol 1m), method B: 47 mg, 48% yield (from
0.5 mmol 1m). M.p. 125–128 C (Lit.24 M.p. 123−124 C). Rf
= 0.46, 10% ethyl acetate in petroleum ether. 1H NMR (400
MHz, CDCl3) δ 8.06 – 8.01 (m, 2H), 7.71 – 7.67 (m, 2H), 7.65
– 7.61 (m, 2H), 7.50 – 7.44 (m, 2H), 7.42 –7.39 (m, 1H), 2.64
(s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 197.7, 145.8, 139.9,
135.8, 128.9, 128.9, 128.2, 127.3, 127.2, 26.7.
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60
1-(4-Methylthiophenyl)ethan-1-one (2n).25 Purified by flash
column chromatography (PE/EA 50:1, v/v) on silica gel to give
the desired product as white solid, method A: 60 mg, 71% yield
(from 0.5 mmol 1n), method B: 41 mg, 49% yield (from 0.5
mmol 1n). M.p. 82–84 C (Lit.25 M.p. 80.6−81.4 C). Rf = 0.44,
2-(Phenylethynyl)oxirane (1r) was prepared from but-3-en-
1-yn-1-ylbenzene using the m-CPBA epoxidation reaction.28 To
a solution of but-3-en-1-yn-1-ylbenzene (640 mg, 5.0 mmol) in
DCM (20 mL) in a 100 mL flask was added m-CPBA (1.5 g,
7.5 mmol, 85%) and Na2HPO4·12H2O (2.15 g, 6 mmol) at 0 C.
The reaction mixture was allowed to stir at room temperature
overnight. The solution was then washed with NaHCO3 aq (20
mL), and dried over Na2SO4. After evaporation of the solvent,
the crude product was purified on silica gel column chromatog-
raphy with a mixture of petroleum ether/EtOAc (20:1, v/v) to
afford the desired epoxide 1r.
1
20% ethyl acetate in petroleum ether. H NMR (400 MHz,
CDCl3) δ 7.86 (d, J = 8.5 Hz, 2H), 7.26 (d, J = 8.4 Hz, 2H), 2.56
(s, 3H), 2.52 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 197.1,
145.8, 133.4, 128.7, 124.9, 26.4, 14.7.
1-(Naphthalen-2-yl)ethan-1-one (2o).20 Purified by flash
column chromatography (PE/EA 50:1, v/v) on silica gel to give
the desired product as yellow oil, method A: 90 mg, 91% yield
(from 0.6 mmol 1o), method B: 81 mg, 95% yield (from 0.5
1
mmol 1o). Rf = 0.29, 5% ethyl acetate in petroleum ether. H
NMR (400 MHz, CDCl3) δ 8.51 – 8.42 (m, 1H), 8.06 – 7.80 (m,
4H), 7.65 – 7.48 (m, 2H). 2.72 (s, 3H).13C{1H} NMR (101 MHz,
CDCl3) δ 198.0, 135.6, 134.5, 132.5, 130.1, 129.5, 128.4, 128.4,
127.7, 126.7, 123.9, 26.6.
All prepared epoxides except 1e are known compounds with
the same analytical data as reported ones. Epoxides 1f, 1s, and
1t are commercially available.
(E)-2-Styryloxirane (1a)29 Yellow liquid, 1.23 g, 56% yield.
Rf = 0.68, 20% ethyl acetate in petroleum ether. 1H NMR (400
MHz, CDCl3) δ 7.44 – 7.40 (m, 2H), 7.36 (t, J = 7.4 Hz, 2H),
7.33 – 7.27 (m, 1H), 6.85 (d, J = 16.0 Hz, 1H), 5.92 (dd, J =
16.0, 8.0 Hz, 1H), 3.64 – 3.45 (m, 1H), 3.09 (dd, J = 5.0, 4.2 Hz,
1H), 2.81 (dd, J = 5.1, 2.6 Hz, 1H). 13C{1H} NMR (101 MHz,
CDCl3) δ 136.1, 134.5, 128.6, 128.0, 126.9, 126.4, 52.5, 49.1.
(E)-2-(4-Chlorostyryl)oxirane (1b).29 Yellow liquid, 0.53 g,
59% yield. Rf = 0.65, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.45 – 7.19 (m, 4H), 6.76 (d, J =
16.0 Hz, 1H), 5.86 (dd, J = 16.0, 7.9 Hz, 1H), 3.63 – 3.38 (m,
1H), 3.06 (dd, J = 4.8, 4.6 Hz, 1H), 2.77 (dd, J = 5.0, 2.4 Hz,
1H). 13C NMR (101 MHz, CDCl3) δ 134.6, 133.7, 133.2, 128.8,
127.7, 127.6, 52.4, 49.2
(E)-2-(2-Methoxystyryl)oxirane (1c)30 Yellow oil, 483 mg,
55% yield. Rf = 0.72, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.31 (d, J = 7.6 Hz, 1H), 7.16 –7.14
(m, 1H), 7.05 (d, J = 16.1 Hz, 1H), 6.86 – 6.75 (m, 2H), 5.80
(dd, J = 16.1, 8.2 Hz, 1H), 3.75 (s, 3H), 3.53 – 3.29 (m, 1H),
2.95 (dd, J= 5.1, 4.6 Hz, 1H), 2.67 (dd, J = 5.1, 2.6 Hz, 1H).
13C{1H} NMR (101 MHz, CDCl3) δ 156.6, 129.6, 129.0, 127.6,
127.0, 125.1, 120.6, 110.8, 55.3, 53.1, 49.1.
1-(Pyridin-4-yl)ethan-1-one (2p).23 Purified by flash column
chromatography (PE/EA 2:1, v/v) on silica gel to give the de-
sired product as colorless liquid, method A: 48 mg, 96% yield
(from 0.4 mmol 1p), method B: 55 mg, 92% yield (from 0.5
1
mmol 1p). Rf = 0.22, 50% ethyl acetate in petroleum eth. H
NMR (400 MHz, CDCl3) δ 8.83 – 8.73 (m, 2H), 8.00 – 7.41 (m,
2H), 2.60 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 197.2,
150.9, 142.7, 121.1, 26.6.
1-(Thiophen-2-yl)ethan-1-one (2q).20 Purified by flash col-
umn chromatography (PE/EA 20:1, v/v) on silica gel to give the
desired product as yellow liquid, method A: 53 mg, 84% yield
(from 0.5 mmol 1q), method B: 33 mg, 53% yield (from 0.5
mmol 1q). Rf = 0.50, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.70 (dd, J = 3.7, 1.2 Hz, 1H), 7.64
(dd, J = 4.9, 1.2 Hz, 1H), 7.13 (dd, J = 5.0, 3.7 Hz, 1H), 2.57 (s,
3H). 13C{1H} NMR (101 MHz, CDCl3) δ 190.7, 144.6, 133.7,
132.4, 128.1, 26.9.
4-Phenylbut-3-yn-2-one (2r).26 Purified by flash column
chromatography (PE/EA 50:1, v/v) on silica gel to give the de-
sired product as colorless oil, method A: 30 mg, 42% yield
(from 0.5 mmol 1r), method B: 28 mg, 31% % (from 0.5 mmol
1
1r). Rf = 0.60, 20% ethyl acetate in petroleum ether. H NMR
(E)-2-(1-Phenylprop-1-en-2-yl)oxirane (1d)29 Colorless oil,
1.552 g, 97% yield. Rf = 0.5, 10% ethyl acetate in petroleum
ether. 1H NMR (400 MHz, CDCl3) δ 7.37 – 7.27 (m, 4H), 7.26
– 7.20 (m, 1H), 6.67 (s, 1H), 3.52 – 3.47 (m, 1H), 2.94 (dd, J =
5.0, 4.6 Hz, 1H), 2.81 (dd, J = 5.0, 2.6 Hz, 1H), 1.74 (s, 1H).
13C{1H} NMR (101 MHz, CDCl3) δ 137.1, 134.0, 128.9, 128.8,
128.2, 126.7, 56.1, 46.8, 11.8.
(400 MHz, CDCl3) δ 7.58 (d, J = 7.1 Hz, 2H), 7.46 (dd, J = 7.4,
7.1 Hz, 1H), 7.39 (dd, J = 7.4, 7.1 Hz, 2H), 2.46 (s, 3H). 13C{1H}
NMR (101 MHz, CDCl3) δ 184.6, 133.0, 130.7, 128.6, 119.9,
90.3, 88.3, 32.7.
General procedure for the synthesis of epoxides 1.
Styrylepoxides 1a-1e and arylepoxides 1g-1q were prepared
from trimethylsulfonium iodide with the corresponding cin-
namaldehydes and aromatic aldehydes using Johnson-Corey-
(E)-2-(1-Phenylhept-1-en-2-yl)oxirane (1e) Colorless oil,
2.086 g, 97% yield. Rf = 0.58, 10% ethyl acetate in petroleum
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The Journal of Organic Chemistry
ether. 1H NMR (400 MHz, CDCl3) δ 7.36 – 7.30 (m, 2H), 7.28
2-(Naphthalen-2-yl)oxirane (1o)34: White solid, 300 mg, 17%
yield. M.p. 57−58 C (Lit.36 M.p. 57−58 C). Rf = 0.70, 20%
ethyl acetate in petroleum ether. 1H NMR (400 MHz, CDCl3) δ
7.92 – 7.76 (m, 3H), 7.55 – 7.46 (m, 3H), 7.36 (dd, J = 8.5, 1.8
Hz, 1H), 4.06 (dd, J = 4.1, 2.6 Hz, 1H), 3.26 (dd, J = 5.4, 4.1
Hz, 1H), 2.94 (dd, J = 5.5, 2.6 Hz, 1H). 13C{1H} NMR (101
MHz, CDCl3) δ 135.0, 133.2, 133.1, 128.3, 127.7, 126.3, 126.0,
125.1, 122.6, 58.1, 52.6, 51.2.
4-(Oxiran-2-yl)pyridine (1p)37 Brown liquid, 60 mg, 10%
yield. Rf = 0.22, 50% ethyl acetate in petroleum ether. 1H NMR
(400 MHz, CDCl3) δ 8.58 (d, J = 6.0 Hz, 2H), 7.21 (d, J = 6.0
Hz, 2H), 3.84 (dd, J = 4.1, 2.5 Hz, 1H), 3.19 (dd, J = 5.5, 4.2
Hz, 1H), 2.76 (dd, J = 5.6, 2.5 Hz, 1H). 13C{1H} NMR (101
MHz, CDCl3) δ 149.9, 146.8, 120.3, 51.2, 50.9.
2-(Thiophen-2-yl)oxirane (1q)38 Colorless liquid, 248 mg,
98% yield. Rf = 0.35, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.25 (dd, J = 4.9, 1.4 Hz, 1H), 7.13
(dd, J = 3.5, 1.2 Hz, 1H), 6.98 (dd, J = 5.0, 3.5 Hz, 1H), 4.10
(dd, J = 4.0, 2.6 Hz, 1H), 3.19 (dd, J = 5.2, 4.0 Hz, 1H), 3.00
(dd, J = 5.1, 2.6 Hz, 1H). 13C{1H} NMR (101 MHz, CDCl3) δ
141.3, 127.0, 126.3, 125.1, 51.5, 49.3.
2-(Phenylethynyl)oxirane (1r)39 Yellow oil, 317 mg, 44%
yield. Rf = 0.81, 20% ethyl acetate in petroleum ether. 1H NMR
(400 MHz, CDCl3) δ 7.45 (dd, J = 7.6, 1.8 Hz, 2H), 7.36 – 7.29
(m, 3H), 3.59 (t, J = 3.3 Hz, 1H), 3.01 (d, J = 3.2 Hz, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 131.9, 128.8, 128.3, 121.9,
85.7, 83.4, 49.1, 40.2.
1
2
3
4
5
6
7
8
– 7.18 (m, 3H), 6.56 (s, 1H), 3.58 – 3.30 (m, 1H), 2.96 (dd, J =
5.6, 4.1 Hz, 1H), 2.69 (dd, J = 5.6, 2.7 Hz, 1H), 2.26 (ddd, J =
13.6, 10.8, 5.6 Hz, 1H), 2.14 (ddd, J = 13.6, 10.7, 5.4 Hz,
1H).1.60 – 1.52 (m, 1H), 1.51 – 1.41 (m, 1H), 1.32 – 1.27 (m,
4H), 0.89 – 0.86 m, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ
138.8, 137.1, 128.6, 128.2, 126.6, 126.3, 54.7, 48.8, 32.0, 28.8,
27.8, 22.4, 14.0. HRMS (ESI-TOF) m/z: [M+H]+ calcd for
C15H21O+ 217.1587, found 217.1584.
2-(4-Chlorophenyl)oxirane (1g)12h Colorless oil, 262 mg, 32%
yield. Rf = 0.5, 20% ethyl acetate in petroleum ether. 1H NMR
(400 MHz, CDCl3) δ 7.30 (d, J = 8.2 Hz, 2H), 7.20 (d, J = 8.2
Hz, 2H), 3.85–3.79 (m, 1H), 3.13 (t, J = 4.7 Hz, 1H), 2.74 (dd,
J = 5.0, 2.1 Hz, 1H). 13C{1H} NMR (101 MHz, CDCl3) δ 136.1,
133.9, 128.7, 126.8, 51.7, 51.2.
2-(4-Bromophenyl)oxirane(1h)12h Colorless oil, 600 mg, 60%
yield. Rf = 0.43, 20% ethyl acetate in petroleum ether. 1H NMR
(400 MHz, CDCl3) δ 7.47 (d, J = 8.5 Hz, 2H), 7.15 (d, J = 8.4
Hz, 2H), 3.82 (dd, J = 3.9, 2.6 Hz, 1H), 3.14 (dd, J = 5.4, 4.1
Hz, 1H), 2.75 (dd, J = 5.5, 2.5 Hz, 1H). 13C{1H} NMR (101
MHz, CDCl3) δ 136.7, 131.6, 127.1, 122.0, 51.8, 51.2.
4-(Oxiran-2-yl)benzonitrile(1i)32 Colorless liquid, 320 mg,
44% yield. Rf = 0.28, 10% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.64 (d, J = 8.3 Hz, 2H), 7.39 (d, J
= 8.3 Hz, 2H), 3.91 (dd, J = 4.1, 2.5 Hz, 1H), 3.21 (dd, J = 5.5,
4.1 Hz, 1H), 2.76 (dd, J = 5.5, 2.5 Hz, 1H). 13C{1H} NMR (101
MHz, CDCl3) δ 143.2, 132.3, 126.1, 118.6, 111.9, 51.6, 51.5.
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60
2-(4-(Trifluoromethyl)phenyl)oxirane(1j)11c: Colorless liq-
uid, 0.456 g, 48% yield. Rf = 0.56, 10% ethyl acetate in petro-
leum ether.1H NMR (400 MHz, CDCl3) δ 7.60 (d, J = 8.4 Hz,
2H), 7.39 (d, J = 8.0 Hz, 2H), 3.91 (dd, J = 4.1, 2.5 Hz, 1H),
3.18 (dd, J = 5.5, 4.1 Hz, 1H), 2.77 (dd, J = 5.5, 2.5 Hz, 1H).
ASSOCIATED CONTENT
Supporting Information
13C{1H} NMR (101 MHz, CDCl3) δ 141.8, 130.34 (q, JC-F
=
The Supporting Information is available free of charge on the ACS
Publications website at DOI:
32.5 Hz), 125.7, 125.4 (q, JC-F = 4.0 Hz), 124.0 (q, JC-F = 266.6
Copies of 1H NMR, 13C NMR, and 19F NMR spectra for all iso-
lated products 1 and 2 (PDF)
Hz), 51.7, 51.4. 19F NMR (377 MHz, CDCl3) δ -62.60.
2-(4-Methoxyphenyl)oxirane (1k)33 Colorless liquid, 1.04 g,
77% yield. Rf = 0.83, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.20 (d, J = 8.6 Hz, 2H), 6.88 (d, J
= 8.6 Hz, 2H), 3.89 – 3.76 (m, 4H), 3.15 – 3.10 (m, 1H), 2.81
(dd, J = 5.2, 2.5 Hz, 1H). 13C{1H} NMR (101 MHz, CDCl3) δ
159.7, 129.4, 126.8, 114.0, 55.3, 52.2, 51.0.
2-(4-Methylphenyl)oxirane (1l)34 Colorless liquid, 665 mg,
98% yield. Rf = 0.80, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.18 – 7.13 (m,4H), 3.83 (dd, J =
4.1, 2.6 Hz, 1H), 3.12 (dd, J = 5.5, 4.1 Hz, 1H), 2.79 (dd, J =
5.5, 2.6 Hz, 1H), 2.34 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3)
δ 138.0, 134.5, 129.2, 125.4, 52.3, 51.1, 21.2.
AUTHOR INFORMATION
Corresponding Author
* E-mail: jxxu@mail.buct.edu.cn (J. Xu); lipf@mail.buct.edu.cn
(P. Li).
ORCID
Jiaxi Xu: 0000-0002-9039-4933;
Siqi Li: 0000-0002-6474-950X
Notes
The authors declare no competing financial interest.
2-([1,1'-Biphenyl]-4-yl)oxirane (1m)34: Yellow solid, 292
ACKNOWLEDGMENT
This work was supported by the National Natural Science Foun-
dation of China (Nos. 21572017 and 21372025), and the Funda-
mental Research Funds for the Central Universities (XK1802-6).
mg, 30% yield. M.p. 103–105℃. Rf = 0.57, 10% ethyl acetate
1
in petroleum ether. H NMR (400 MHz, CDCl3) δ 7.60 – 7.57
(m, 4H), 7.48 – 7.41 (m, 2H), 7.38 – 7.31 (m, 3H), 3.91 (dd, J
= 4.1, 2.6 Hz, 1H), 3.18 (dd, J = 5.5, 4.1 Hz, 1H), 2.85 (dd, J =
5.5, 2.6 Hz, 1H). 13C{1H} NMR (101 MHz, CDCl3) δ 141.2,
140.6, 136.6, 128.8, 127.4, 127.2, 127.0, 125.9, 52.2, 51.2.
2-(4-Methylthiophenyl)oxirane (1n)35 Colorless oil, 967 mg,
58% yield. Rf = 0.63, 20% ethyl acetate in petroleum ether. 1H
NMR (400 MHz, CDCl3) δ 7.22 (d, J = 8.5 Hz, 2H), 7.18 (d, J
= 8.4 Hz, 2H), 3.80 (dd, J = 4.0, 2.7 Hz, 1H), 3.11 (dd, J = 5.4,
4.1 Hz, 1H), 2.77 (dd, J = 5.4, 2.6 Hz, 1H), 2.46 (s, 3H). 13C{1H}
NMR (101 MHz, CDCl3) δ 138.4, 134.3, 126.5, 125.9, 52.0,
51.0, 15.7.
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