Highly efficient epoxidation of electron-deficient olefins with tetrabutylammonium peroxydisulfate

Article abstract of DOI:10.1016/j.tet.2007.03.167

The epoxidation of α,β-unsaturated carbonyl compounds such as enones and enals was efficiently achieved with tetrabutylammonium peroxydisulfate in the presence of equimolar amounts of hydrogen peroxide and NaOH in acetonitrile or methanol at 25 °C in excellent yields. Base-sensitive substrate such as cinnamaldehyde could be successfully epoxidized in short reaction time under mild reaction conditions.

Full text of DOI:10.1016/j.tet.2007.03.167

Tetrahedron 63 (2007) 5184–5188
Highly efficient epoxidation of electron-deficient olefins
with tetrabutylammonium peroxydisulfate
a
Seung Gak Yang, Je Pil Hwang, Min Young Park, Kieseung Lee and Yong Hae Kim
a
a
b
a,*
a
Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
b
Department of Chemistry, Woosuk University, Chonbuk 565-701, Republic of Korea
Received 12 March 2007; revised 28 March 2007; accepted 29 March 2007
Available online 4 April 2007
Abstract—The epoxidation of a,b-unsaturated carbonyl compounds such as enones and enals was efficiently achieved with tetrabutyl-
ꢀ
ammonium peroxydisulfate in the presence of equimolar amounts of hydrogen peroxide and NaOH in acetonitrile or methanol at 25 C in
excellent yields. Base-sensitive substrate such as cinnamaldehyde could be successfully epoxidized in short reaction time under mild reaction
conditions.
Ó 2007 Elsevier Ltd. All rights reserved.
1
. Introduction
work, we have successfully prepared tetrabutylammonium
peroxydisulfate (TBA S O ), which turns out to be a versa-
tile reagent for the useful transformations, e.g., cleavage of
6
2
2 8
Epoxidation of electron-deficient olefins has become one of
the most significant organic reactions in recent years not
only because the resulting epoxy compounds could be
directly used in organic synthesis as essential building
blocks, but also because they could be readily transformed
into various synthetically useful intermediates, e.g., a- and
b-hydroxy carbonyls, a,b-epoxy alcohols, allylic alcohols,
7
a
C]N bond,
ation of alcohols,
ketones.
tetrahydrofuranylation/tetrahydropyranyl-
and a-iodination of functionalized
6
,7b,c
7
d
Recently, we have shown that various a,b-unsaturated
ketones were smoothly epoxidized with TBA S O /H O
2 2
2
2
8
1
8
and 1,3-diols, etc.
under basic conditions in excellent yields. This initial result
prompted us to thoroughly study this reaction using different
solvents/various electron-deficient carbonyl compounds
such as enones and enals. Herein, we wish to disclose the
details of this research and data of the reaction products.
The epoxidation of general and electron-rich olefins is gen-
erally achieved with electrophilic oxidants such as peroxy
acids. By contrast, epoxidation of electron-deficient olefins
2
bearing an electron-withdrawing group at the double bond
generally requires nucleophilic oxidation under basic con-
ditions. Representative examples of such nucleophilic
2. Results and discussion
3
a
1c
oxidants are H O /Bu NF, t-BuOOH/DBU, m-CPBA/
4
2
2
3
b
3c
3d
KOH, NaOCl/cinchona alkaloid, or NaBO /THAHS.
3
Various a,b-unsaturated carbonyl compounds 3 (enones and
enals) have been selected for epoxidation reaction according
to the protocol described in Scheme 1.
Recent reports of epoxidation of electron-deficient olefins
4
a
4b
with iodosyl benzene and dioxirane are noteworthy to
be mentioned since the reactions are carried out under
neutral conditions.
In order to obtain the basic information regarding the opti-
mum reaction conditions, a,b-unsaturated ketone 3a was
attempted first as a model compound under the various re-
action conditions, and the results are summarized in Table 1.
We have been interested in developing efficient epoxidizing
systems/reagents for electron-deficient olefins such as a,b-
unsaturated ketones. In our earlier work, we have failed to
epoxidize a,b-unsaturated ketones with peroxysulfur inter-
mediate generated in situ from superoxide anion and nitro-
When 3a was reacted with equimolar amounts of 1 and
NaOH without H O in acetonitrile at 25 C, very low re-
ꢀ
2
2
5
benzenesulfonyl chloride. In continuation of this kind of
action progress was observed (run 1). On the other hand,
the same reaction conducted using equimolar amounts of
H O and NaOH in the absence of 1 provided the corre-
2
2
Keywords: Epoxidation; Electron-deficient olefins; Tetrabutylammonium
peroxydisulfate; Hydrogen peroxide.
sponding epoxide 4a in ca. 30% yield (run 2). However,
combined use of equimolar amounts of H O , NaOH, and
*
Corresponding author. Tel.: +82 42 869 2818; fax: +82 42 869 2810;
e-mail: kimyh@kaist.ac.kr
2 2
ꢀ
1 in acetonitrile at 25 C resulted in excellent yield of
0
040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.03.167

S. G. Yang et al. / Tetrahedron 63 (2007) 5184–5188
5185
O
S
O
O
S
O
Table 2. Epoxidation of a,b-unsaturated carbonyl compounds (3) in CH CN
3
at 25 C
H2O2, NaOH
CH3CN or MeOH, 25 °C
O
ꢀ
a
Bu4N+-O
O-+NBu4
R1
O
O
b
Yield (%)
1
Run
Substrate
Time (min)
Product
O
S
O
O
R2
1
2
3
4
5
6
3a
3c
3d
3e
3f
30
150
30
30
30
4a
4c
4d
4e
4f
95
88
95
85
95
92
Bu4N+-O
O-
O
2
O
3
R1
R2
2
4
3
a: R1 = Ph, R2 = Me
4a: R1 = Ph, R2 = Me
4b: R1 = Ph, R2 = Ph
3g
120
4g
3
3
3
b: R1 = Ph, R2 = Ph
a
The ratio of 1/3/H
lsolated yield.
2
O
2
/NaOH¼1:1:1:1.
c: R1 = Phenethyl, R2 = Me
d: Cyclohexenone
4c: R1 = Phenethyl, R2 = Me
4d: 2,3-Epoxycyclohexanone
b
solvent under the standard reaction conditions (1 equiv of
each 1, H O , and NaOH, 25 C), and the experimental re-
3
e: Cyclopentenone
4e: 2,3-Epoxycyclopentanone
ꢀ
sults are summarized in Table 2 as reported earlier.
2
2
O
O
8
3f:
4f:
O
The double bonds of acyclic and cyclic a,b-unsaturated ke-
tones were smoothly epoxidized in good to excellent yields.
O
O
O O
3
g:
4g:
O
Methanol was then tested as the reaction solvent to expand
the generality of this new epoxidation protocol, and the
results are summarized in Table 3.
3
h: R1 = Ph, R2 = H
4h: R1 = Ph, R2 = H
CHO
CHO
When methanol instead of acetonitrile was used as the reac-
tion solvent, the reaction time reduced dramatically though
the yields improved slightly in general probably due to the
increased solubility of NaOH in methanol.
3i:
4i:
O
Scheme 1. Epoxidation of a,b-unsaturated carbonyl compounds with
TBA , 1.
2
S
2
O
8
The double bonds of acyclic a,b-unsaturated ketones can be
readily epoxidized (run 1 and 2), while the double bond in
a long chain of acyclic a,b-unsaturated ketone required
longer reaction time (run 3). In the case of cyclic a,b-unsat-
urated ketones (run 4, 5, 6, and 7), the epoxidation generally
proceeded more rapidly than acyclic counterparts with com-
parable yields. The epoxidation of (ꢁ)-carvone 3g is note-
worthy to be mentioned since it clearly demonstrates that
the double bond conjugated with carbonyl group can be
epoxidized regioselectively in the presence of a general dou-
ble bond even though it has an a-substituent (run 7). This
result is quite interesting since b-substituted a,b-unsaturated
ketones such as a-ionone and pulegone were failed to be
epoxidized under the standard reaction conditions probably
epoxide 4a (95%, run 3). In the case of K CO being used as
2
3
a base under the similar reaction conditions as run 3, the
yield of 4a was diminished to 50% (run 4). In the variation
of solvents, several other organic solvents, e.g., benzene,
CH Cl , CHCl , and methanol were also tested as the reac-
2
2
3
tion solvent (run 5, 6, 7, and 8). Among other solvents exam-
ined, methanol demonstrated the best results in terms of
reaction time and yield most probably due to the increased
solubility of base in methanol (run 8). When 3a was reacted
with 0.5 equiv of each 1, H O , and NaOH in methanol,
2
2
ꢀ
epoxide 4a was obtained in 90% yield (25 C, 10 min, run
). Thus, acetonitrile and methanol have been finally chosen
9
9
as the reaction solvent, and reaction conditions (run 3 and 8)
were adopted as the standard protocol for epoxidation reac-
tion. The epoxidation reaction of various electron-deficient
olefins was carried out first using acetonitrile as the reaction
owing to the steric hindrance of b-substituent.
Epoxidation of aldehydes is of special attention because ear-
lier works on the epoxidation of cinnamaldehyde reported
1
c,3a,d,10
low yields or long reaction time. Following our stan-
dard reaction conditions, however, cinnamaldehyde could be
Table 1. Attempted epoxidation of a,b-unsaturated ketone (3a) under
various reaction conditions
Table 3. Epoxidation of a,b-unsaturated carbonyl compounds (3) in CH
ꢀ
3
OH
1
/ H2O2 / Base
a
3
a
4a
at 25 C
Solvent
b
Yield (%)
Run
Substrate
Time (min)
Product
a
2 2
Run 1/H O (equiv) Base (equiv) Solvent Time (min) Yield (%)
1
2
3
4
5
6
7
8
9
3a
3b
3c
3d
3e
3f
3g
3h
3i
10
20
30
5
10
10
60
20
60
4a
4b
4c
4d
4e
4f
4g
4h
4i
98
91
95
95
92
95
92
90
91
1
2
3
4
5
6
7
8
9
1/0
0/1
1/1
1/1
1/1
1/1
1/1
1/1
NaOH (1)
NaOH (1)
NaOH (1)
CH
CH
CH
CH
3
CN 60
3
CN 60
3
CN 30
3
CN 60
Trace
30
95
K
2
CO
3
(1)
50
10
65
73
98
90
NaOH (1)
NaOH (1)
NaOH (1)
NaOH (1)
Benzene 60
CH
CHCl
MeOH
2
Cl
2
60
60
5
3
0.5/0.5
NaOH (0.5) MeOH 10
a
The ratio of 1/3/H
Isolated yield.
2
O
2
/NaOH¼1:1:1:1.
a
b
Isolated yield.

5186
S. G. Yang et al. / Tetrahedron 63 (2007) 5184–5188
epoxidized in short reaction time in excellent yield (run 8,
0%, 20 min). Presumably, rapid reaction progress and
mild reaction conditions enable the epoxidation reaction
successful by allowing aldehyde moiety being intact during
the short reaction time. The successful epoxidation of 3i (run
movement to afford the epoxides 4 together with tetrabutyl-
ammonium sulfate 5. Peroxysulfate anion intermediate 2
has been neither isolated nor confirmed, but sulfate 5 was
isolated in ca. 80% yield and confirmed.
9
9
), an acyclic b-substituted a,b-unsaturated aldehyde, is also
In conclusion, both acyclic and cyclic a,b-unsaturated ke-
tones (enones) were smoothly oxidized into the correspond-
ing epoxides in excellent yields. a,b-Unsaturated aldehydes
(enals) including base-sensitive cinnamaldehyde could also
be epoxidized efficiently in short reaction time. Considering
several advantages of our approach over the reported meth-
quite contrasted with the aforementioned negative results in
the epoxidation of b-substituted a,b-unsaturated ketones
such as a-ionone and pulegone.
We have also attempted epoxidation of a,b-unsaturated ester
and amide in methanol under the similar reaction conditions,
but epoxidation did not occur at all. In the case of a,b-un-
saturated ester, transesterification took place almost quan-
1
c,3a,d,10,12,13
ods,
agent (TBA S O ), mild reaction conditions and simple
e.g., easy preparation of the requisite re-
2
2 8
reaction procedures, highly improved yields and dramati-
cally reduced reaction time, use of acetonitrile and prefera-
bly MeOH as the reaction solvent, and furthermore inertness
of acetal, ketal, and thioether functionalities toward 1 found
1
1
titatively (Scheme 2).
O
O
O
6
,7b,c
O
1
, H2O2, NaOH
in our earlier works,
our epoxidating approach could be
Ph
OEt
Ph
OMe + Ph
R: -Et or -Me,
not detected)
OR
a method of choice in the epoxidation of a,b-unsaturated
carbonyl compounds having various functional groups
such as acetal, ketal, and thioether moieties without affect-
ing these functional groups.
MeOH
(
(
98%)
Scheme 2. Attempted reaction of a,b-unsaturated ester with 1/H
in CH OH.
3
2 2
O /NaOH
Concerning the reaction mechanism, there seems to be
two competitive epoxidating routes plausible: one is direct
epoxidation by HOO , and the other is epoxidation by per-
3. Experimental
3.1. General
ꢁ
oxysulfate anion intermediate 2 (Fig. 1).
All reactions were carried out in oven-dried glassware under
dry N or argon atmosphere. Melting points were taken on an
Electro-thermal melting point apparatus and are uncor-
The latter, however, appears to be the main route from the
following experimental results (Table 1): (i) use of equi-
valent amount of each peroxydisulfate 1 and NaOH without
H O gave trace amount of epoxide 4a (run 1); (ii) use of
2
1
13
rected. H NMR (200, 300 or 400 MHz) and C NMR (75
or 100 MHz) spectra were obtained on Bruker FT spectro-
meters in CDCl , and chemical shifts (d) were reported in
2
2
equivalent amount of each H O and NaOH in the absence
2
2
3
of 1 resulted in 30% yield of epoxide 4a (run 2); (iii) use
of equivalent amount of each 1, H O , and NaOH afforded
parts per million downfield from tetramethylsilane as an
internal standard. GC spectra were recorded from GC fitted
with OV-17 packed column. High-resolution mass spectra
(HRMS) were measured with VG Autospec Ultima instru-
ment in EI (70 eV) mode at KAIST. Flash column chroma-
tography was performed on silica gel (Merck, 230–400
mesh) using organic solvents as eluents. Starting a,b-unsat-
urated carbonyl compounds were purchased from commer-
cial sources or prepared according to the known method.
Methanol, acetonitrile, methylene chloride, and diethyl ether
were purified by the usual methods.
2
2
9
each 1, H O , and NaOH provided 90% of epoxide 4a (run
5% yield of epoxide 4a (run 3); (iv) use of 0.5 equiv of
2
2
9
anism since it strongly indicates that 0.5 equiv of each 1 and
). Result (iv) is highly informative about the reaction mech-
ꢁ
HOO may form stoichiometric amount of peroxysulfate
anion intermediate 2 as a reactive intermediate. The stronger
ꢁ
ꢁ
nucleophile (HOO ) rather than OH may be attributed to
form peroxysulfate anion intermediate 2 more easily, which
also shows a strong nucleophilic oxidizing ability toward
substrates 3. Therefore, epoxidation may be initiated by per-
oxysulfate anion intermediate 2 via 1,4-addition of 2 onto
a,b-unsaturated carbonyls 3, and then following electronic
3.1.1. Tetrabutylammonium peroxydisulfate (1). Tetra-
butylammonium hydrogensulfate (21.2 g, 64.0 mmol) and
potassium persulfate (8.70 g, 32.0 mmol) were dissolved
in 140 mL of distilled water and the solution was stirred
for 30 min at room temperature. The solution was extracted
H2O2,OH-
O
S
O
S
HOO-
O
S
Bu4N+ -O
O-+NBu4
2 Bu N+ -O
4
O-
with CH Cl (30 mLꢂ3), and the combined organic layers
O
O
O
2
2
were washed with distilled water (30 mLꢂ3), dried over an-
O
O
O
1
2
hydrous MgSO , and filtered. Evaporation of the solvent in
4
O
vacuo and subsequent drying under high vacuum gave 1 as
a white solid in 95% yield. Mp 118–120 C (dec); H
R1
R2
O
O
S
O
ꢀ
NMR (300 MHz) d 3.2 (t, 8H), 1.6 (m, 8H), 1.2 (m, 8H),
1
O
3
Bu4N+ -
O-
R1
O
O
R2
0
.8 (t, 12H); IR (NaCl) 2951, 2874, 1476, 1382, 1063,
O
S
O
ꢁ
1041, 676 cm . Anal. Calcd for C H N O S : C, 56.7;
32 72 2 8 2
1
Bu4N+-O
O
O
O
S
O
O-
Bu N+ -O
O-
H, 10.7; N, 4.14. Found: C, 56.9; H, 10.8; N, 4.15. The per-
oxydisulfate 1 turns out to be stable for a couple of months
at room temperature, and can be stored in refrigerator
permanently.
+
4
R1
R2
O
R1
R2
4
5
Figure 1. Plausible reaction mechanism for epoxidation.

S. G. Yang et al. / Tetrahedron 63 (2007) 5184–5188
5187
3
.2. General procedure for the epoxidation in CH CN
3
3.3.6. 2,3-Epoxy-2,3-dihydro-1,4-naphthoquinone (4f).
Mp 135–136 C (lit. 134–136 C); H NMR (300 MHz)
13b
ꢀ ꢀ
1
(
procedure A)
1
3
d 7.98–7.95 (m, 2H), 7.76–7.73 (m, 2H), 4.00 (s, 2H);
C
To a stirred solution of a,b-unsaturated ketone (1.0 mmol)
in anhydrous acetonitrile (1 mL) were added a mixture of
NMR (75 MHz) d 190.5, 134.5, 131.6, 127.0, 55.1; HRMS
(EI) m/z calcd for C H O 174.0317, found 174.0317.
1
0 6 3
1
(667 mg, 1.0 mmol) and sodium hydroxide (40 mg,
.0 mmol) in anhydrous acetonitrile (4 mL), and then hydro-
1
gen peroxide (100 mL, 30%, 1.0 mmol) slowly at 25 C.
3.3.7. 2,3-Epoxy-5-isopropenyl-2-methylcyclohexanone
(4g). H NMR (300 MHz) d 4.63–4.57 (d, 2H), 3.31 (t, 1H),
ꢀ
1
ꢀ
with monitoring on TLC, and extracted with CH Cl
The reaction mixture was stirred for 30–150 min at 25 C
2.55–2.52 (m, 1H), 2.45–2.37 (m, 1H), 2.25–2.16 (m, 1H),
1.92–1.83 (dd, 1H), 1.81–1.72 (m, 1H), 1.57 (s, 3H), 1.24
(s, 3H); C NMR (75 MHz) d 204.8, 146.0, 110.1, 60.9,
2
2
1
3
(
with water, dried over anhydrous MgSO , and concentrated
30 mLꢂ3). The combined organic layers were washed
ꢁ
1
58.3, 41.4, 34.7, 28.3, 20.2, 14.9; IR (NaCl) 1705 cm ;
HRMS (E1) m/z calcd for C H O 166.0994, found
166.0986.
4
in vacuo. The crude product was purified by flash column
chromatography on SiO to afford a pure product.
1
0 14 2
2
1
3
(
.3. General procedure for the epoxidation in MeOH
procedure B)
3.3.8. 2,3-Epoxy-3-phenylpropanal (4h).
(300 MHz) d 9.16 (d, J¼6.0 Hz, 1H), 7.36–7.24 (m, 5H),
.14 (d, J¼1.8 Hz, 1H), 3.43 (dd, J ¼6.0 Hz, J ¼1.8 Hz,
H
NMR
4
1
2
1
3
To a stirred solution of a,b-unsaturated carbonyl compound
0.50 mmol) in 2 mL of methanol were added 1 (334 mg,
.50 mmol), H O (50 mL, 0.50 mmol, 30% in H O), and
1H); C NMR (75 MHz) d 196.7, 134.0, 129.0, 128.6,
125.5, 62.7, 56.4; IR (NaCl) 1730 cm ; HRMS (EI) m/z
calcd for C H O 148.0524, found 148.0522.
ꢁ
1
(
0
2
2
2
9 8 2
NaOH (20.0 mg, 0.5 mmol) successively at room tempera-
ture. After stirring for 5–60 min at 25 C, the reaction mix-
ꢀ
ture was poured into saturated aq NH Cl solution (30 mL),
1
3.3.9. 2,3-Epoxy-3,7-dimethyl-6-octenal (4i). H NMR
(300 MHz, mixture of cis and trans) d 9.38–9.32 (m, 1H),
4.98–4.95 (m, 1H), 3.10–3.05 (m, 1H), 2.05–1.98 (m, 2H),
4
and extracted with diethyl ether (30 mLꢂ3). The combined
1
3
ethereal layers were washed with brine, dried over anhy-
drous MgSO , and concentrated under reduced pressure to
1.76–1.33 (m, 11H); C NMR (75 MHz, mixture of cis
and trans) d 199.3, 198.6, 133.0, 132.5, 122.4, 122.2, 64.4,
64.3, 63.9, 63.3, 38.1, 33.2, 25.47, 25.42, 24.0, 23.2, 21.9,
17.47, 17.41, 17.0; HRMS (E1) m/z calcd for C H O
10 16 2
4
provide a crude product, which was purified by flash column
chromatography on SiO to provide a pure product.
2
1
68.1150, found 168.1157.
ꢀ
lit. 52–54 C); H NMR (300 MHz) d 7.35–7.24 (m, 5H),
3
(
.3.1. 3,4-Epoxy-4-phenyl-2-butanone (4a). Mp 53–55 C
ꢀ
1
3a
1
3.3.10. Isolation of tetrabutylammonium hydrogensul-
fate (5). In the above experiment (procedure A), the aqueous
solution was saturated with sodium chloride and extracted
with methylene chloride (30 mLꢂ4). The CH Cl layer
3
.98 (d, J¼1.8 Hz, 1H), 3.47 (d, J¼1.8 Hz, 1H), 2.16 (s, H);
1
3
C NMR (75 MHz) d 204.0, 134.9, 128.9, 128.6, 125.6,
3.4, 57.6, 24.7; IR (NaCl) 1712 cm ; HRMS (EI) m/z
ꢁ
1
6
calcd for C H O 162.0681, found 162.0682.
2
2
was washed with aq HCl (30 mL, 1 N), then with distilled
water and filtered. The organic layer was dried over an-
hydrous MgSO , filtered, and concentrated in vacuo. Further
1
0 10 2
3
.3.2. 2,3-Epoxy-1,3-diphenylpropanone (4b). Mp 90–
4
ꢀ
m, 2H), 7.60–7.58 (m, 1H), 7.49–7.44 (m, 2H), 7.39–7.35
13b
ꢀ
1
9
1 C (lit. 89–90 C); H NMR (300 MHz) d 8.00–7.98
drying under high vacuum gave pure tetrabutylammonium
hydrogensulfate as a white solid in 80% yield, mp 170–
171 C (lit. 169–171 C).
(
(
14
ꢀ ꢀ
m, 5H), 4.28 (d, J¼1.9 Hz, 1H), 4.06 (d, J¼1.9 Hz, 1H);
1
3
C NMR (75 MHz) d 193.0, 135.4, 128.8, 128.7, 128.3,
25.7, 61.0, 59.3; IR (NaCl) 1689 cm ; HRMS (EI) m/z
ꢁ
1
1
calcd for C H O 224.0837, found 224.0838.
1
5 12 2
Acknowledgements
1
3
.3.3. 3,4-Epoxy-6-phenyl-2-hexanone (4c). H NMR
This work was supported by Center for Molecular Design
and Synthesis of Korea Science and Engineering foundation.
(
400 MHz) d 7.30–7.16 (m, 5H), 3.15 (d, J¼2.0 Hz, 1H),
3
1
1
.09–3.05 (dt, 1H), 2.81–2.74 (m, 1H), 1.99 (s, 3H), 1.96–
.90 (m, 2H); C NMR (100 MHz) d 205.4, 140.3, 128.5,
28.4, 128.3, 128.2, 126.3, 59.8, 57.4, 33.3, 31.9, 24.7; IR
1
3
ꢁ
1
(
NaCl) 1711 cm ; HRMS (EI) m/z calcd for C H O
2 14 2
References and notes
1
1
90.0994, found 190.0998.
1
. (a) Jacobsen, E. N. Acc. Chem. Res. 2000, 33, 421–431; (b)
Porter, M. J.; Skidmore, J. Chem. Commun. 2000, 1215–
1225; (c) Yadav, V. K.; Kapoor, K. K. Tetrahedron 1995, 51,
8573–8584.
1
3
.3.4. 2,3-Epoxycyclohexanone (4d). H NMR (300 MHz)
d 3.56–3.54 (m, 1H), 3.19 (d, J¼3.9 Hz, 1H), 2.55–2.46 (dt,
1
1
H), 2.26–2.04 (m, 1H), 1.95–1.66 (m, 2H), 1.67–1.61 (m,
H); C NMR (75 MHz) d 205.6, 55.6, 36.3, 22.8, 16.9;
1
3
2. Smith, M. B.; March, J. March’s Advanced Organic Chemistry,
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ꢁ
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IR (NaCl) 1711 cm ; HRMS (EI) m/z calcd for C H O
8 2
6
1
12.0524, found 112.0526.
2
85–288; (b) Garcia, R. J. L.; Fajardo, C.; Fraile, A.; Martin,
1
3.3.5. 2,3-Epoxycyclopentanone (4e). H NMR (300 MHz)
d 3.73–3.72 (m, 2H), 3.10–3.08 (m, 1H), 2.18–2.02 (m, 2H), 1.96–
1
M. R. J. Org. Chem. 2005, 70, 4300–4306; (c) Lygo, B.;
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13
.82 (m, 2H); C NMR (75 MHz) d 209.3, 57.2, 54.0, 29.7, 22.4.

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(
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