A convenient synthesis of olefins via deacylation reaction

Article abstract of DOI:10.1016/j.tet.2004.01.022

A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room temperature in high yields (70-90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig, Wittig-Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the α-substituents of the 1,3-dicarbonyl compounds.

Full text of DOI:10.1016/j.tet.2004.01.022

Tetrahedron 60 (2004) 2337–2349
A convenient synthesis of olefins via deacylation reaction
Shogo Nakatsu,a Aider T. Gubaidullin,b Vakhid A. Mamedovb and Sadao Tsuboia
,
*
aDepartment of Environmental Chemistry and Materials, Faculty of Environmental Science and Technology, Okayama University,
Tsushima Okayama 700-8530, Japan
bA.E. Arbuzov Institute of Organic and Physical Chemistry, Russian Academy of Science, Arbuzov str. 8, Kazan 420088,
Russian Federation
Received 14 October 2003; accepted 8 January 2004
Abstract—A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives
olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room
temperature in high yields (70–90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig,
Wittig–Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and
X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the a-substituents of the 1,3-dicarbonyl compounds.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
synthesis of other a,b-unsaturated carbonyl compounds,
and some results were communicated in our previous
paper.2 The olefin geometry was tentatively determined, and
4-membered ring transition states of the deacylation
reaction were also postulated.2
Many natural products possess various di- and tri-sub-
stituted alkene components. In the synthesis of these natural
products, a,b-unsaturated esters and ketones are important
building blocks. In the olefin synthesis, highly selective
stereo-control is one of the most important objectives of
organic synthetic chemists.
Recently, the scope and limitations of this method were
finely reinvestigated and the olefin geometry was
absolutely determined by NMR experiments. This
paper provides a full description of our previous
communication (Scheme 1).2
More than 40 different synthetic methods for olefins
synthesis are known.1 The most famous olefin syntheses
are the Wittig reaction1a and the Wittig–Horner reaction.1b
Dehydration olefin synthesis1c is also a representative
method. Other synthetic methods of olefins are Peterson
olefination,1d Johnson methylenation,1e Julia olefination,1f
Knovenagel reaction,1g olefin metathesis,1h Tebbe reac-
tion,1i McMurry reaction1j and Takai olefination reaction,1k
etc. Furthermore, some eliminations1l and addition–
elimination reactions,1m reductions of alkynes,1n catalytic
coupling reactions,1o reactions of alkynes1p with organo-
metallic reagents are well-known methods.
This paper reports a convenient, operationally simple
and environmentally-friendly synthetic method of a,b-
unsaturated ketones, esters, and lactones using deacyla-
tion reaction, and the olefin geometry was determined
with NOE experiments and X-ray analysis of the
olefines obtained. Reactivity and stereoselectivity
among the Wittig, Wittig–Horner and deacylation
reactions were also compared. Furthermore, we exam-
ined the competitive reaction between deacetylation and
debenzoylation reactions.
In 1978, Tsuboi et al. found a new, simple, convenient
method for the synthesis of 5,5,5-trichloro-3-penten-2-one
(1a) by the reaction of chloral with 2,4-pentanedione (A-1)
in the presence of anhydrous potassium carbonate at room
temperature. Furthermore, this method was extended to the
In order to establish the generality of the deacylation
reaction in the presence of potassium carbonate at room
temperature, we investigated reactions of various of
aldehydes with some 1,3-dicarbonyl compounds such as
2,4-pentanedione (A-1), 3-chloro-2,4-pentanedione (A-2),
ethyl 3-oxobutanoate (B-1), ethyl 2-chloro-3-oxobutanoate
(B-2), ethyl 2-methyl-3-oxobutanoate (B-3), ethyl 3-oxo-3-
phenylpropionate (C-1), ethyl 2-chloro-3-oxo-3-phenylpro-
pionate (C-2), and a-acetyl-g-butyrolactones (D).
Keywords: Wittig reaction; Wittig–Horner reactions; Aldehydes;
Unsaturated esters.
*
Corresponding author. Tel./fax: þ81-86-251-8898;
e-mail address: stsuboi6@cc.okayama-u.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.01.022

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S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
Scheme 1.
of 1,3-dicarbonyl compounds (A, B and C) with several
aldehydes.
Table 1 shows a synthesis of a,b-unsaturated methyl
ketones by the reaction of A with aldehydes via deacetyla-
tion reaction. All reactions proceeded in 2 days. In the case
of X¼H, only the E-isomer is produced and in the case of
X¼Cl, only the Z-isomer is produced, respectively.
Reactive aldehydes such as dichloroacetaldehyde
(R¼CHCl2) and chloral (R¼CCl3) gave the desired
products in moderate to good yields. Inactive normal alkyl
A summary of this paper is shown in Scheme 2. In this paper
the reactions of acyl compounds of R0¼Me and Ph in
R0COCHW1W2 are called ‘deacetylation’ and ‘debenzoyla-
tion’, respectively. In Scheme 2, electron-withdrawing
group W1 is acetyl, ester, and chlorine groups, and W2 is
H or Me. As shown in Scheme 2, deacylation reaction
between 1,3-dicarbonyl compounds and aldehydes was
carried out in THF in the presence of potassium carbonate
(1.5 equiv.) at room temperature to give olefins, and the
geometry was absolutely determined by NMR experiments.
Table 1. Synthesis of a,b-unsaturated ketones via deacetylation reaction
Entry
X
R
Yield (%)
E/Z
Compounds No.
1
2
3
4
5
6
H
H
Cl
Cl
Cl
Cl
CCl3–
74
28
56
51
37
49
100:0
100:0
0:100
0:100
0:100
0:100
1a
1b
1d
1e
1f
C2H5–
CHCl2–
CCl3–
C2H5–
n-C6H13
2. Results and discussion
–
1g
Tables 1–3 summarize the results obtained by the reaction
Scheme 2. Deacylation reaction (deacetylation, debenzoylation).

S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
Table 2. Synthesis of a,b-unsaturated esters via deacetylation reaction
2339
Entry
X
R
Reaction time (day)
Yield (%)
E/Z
Compounds No.
1
2
3
4
5
6
7
8
H
Cl
Cl
Cl
Cl
Cl
CH3
CH3
CCl3–
CHCl2–
CCl3–
C2H5–
(MeO)2CHCH2–
n-C6H13
CHCl2–
CCl3–
2
5
5
6
1
5
1
2
38
67
83
50
20
53
7
100:0
100:0
100:0
86:14
75:25
83:17
92:8
2a
2b
2c
2d
2e
2f
–
2h
2l
90
100:0
aldehydes (R¼Et, n-Hex) gave the product in moderate to
In addition, the deacetylation reaction for cyclic compounds
was investigated and the result is summarized in Scheme 3.
The reaction with a-acetyl-g-butyrolactone D gave a-
alkylidene lactones.
poor yields.
A synthesis of a,b-unsaturated esters by the reaction of
ethyl acetoacetates B with aldehydes via deacetylation
reaction is shown in Table 2. Most of the reactions pro-
ceeded in 2 days. In the case of X¼H, only the E-isomer was
produced as the same as in Table 1. However, in the case of
X¼Me and Cl, the E-isomer was obtained predominantly.
Reactive aldehydes, chloral (R¼CCl3) gave the desired
products in good yields, except entry 1. Electron-donating
aldehyde (R¼p-MeOC6H4) did not give any products. In the
case of X¼Me, reactions with inactive alkyl aldehydes
(R¼C2H5, CH3CHvCH–) and aromatic aldehydes (R¼Ph)
did not give any products. The result of synthesis of a,b-
unsaturated esters by the reaction of benzoylacetate C with
aldehydes via debenzoylation reaction3 is shown in Table 3.
All reactions except entry 5 proceeded in good yields, but
the stereoselectivity decreased somewhat.
Scheme 3. Synthesis of a,-alkylidene lactones via deacetylation reaction.
On the other h0and, the reaction with a-acetylcyclopenta-
none gave 3-(2 -chlorovinyl)-2-hydroxy-2-cyclopentenone,
which is thought to be derived from a-trichloroethylidene-
cyclopentanone, in 32% yield (Scheme 4).4,5
It is worthwhile to point out that in cases of unsymmetrical
1,3-diketones such as E, the less sterically hindered
carboxylate is expelled (Scheme 5). When there is no
significant difference in steric hindrance between the Me
and Ph groups, mixtures of the two possible a,b-unsaturated
ketones were isolated. This phenomenon was observed by
using 1-phenyl-1,3-butandione E where the formation of the
compound with the bigger Ph group was favored [39% 1c
(deacetylation product)]. 18% 1a (debenzoylation product),
respectively]. The small acetyl group was expelled
predominantly. In the competitive reactions of deacetylation
and debenzoylation, the deacetylation reaction proceeded 2
times faster than the debenzoylation reaction.
Generally, reactive aldehydes such as chloral (R¼CCl3) and
dichloroacetaldehyde (R¼CHCl2) gave the desired products
in good yields. Normal alkyl aldehydes (R¼Et, n-Hex) and
aromatic aldehydes (R¼Ph) gave the product in moderate to
poor yields. The deacylation reaction proceeded smoothly
with 100% E-selectivity when the 1,3-diketo compounds
have no substituents at the a-position (X¼H).
Table 3. Synthesis of a,b-unsaturated esters via debenzoylation reaction
We investigated the solvent effect of our deacetylation
reaction and the result is summarized in Table 4. From the
table it is envisioned that aprotic ether type solvents such as
THF, DME (entry 1–3, 7) give the product in good yield.
Entry
X
H
R
Reaction time
(day)
a,b-Unsaturated
esters 2
Acetone was also a good solvent (entry 8) and it is better
than polar aprotic solvent DMF (entry 9). The reaction in
nonpolar solvent, hexane gave the product in low yield. So,
reaction media should be a little polar (entry 1–3, 7–9).
When a carbonate ion is produced, some polar stability is
necessary. Several kinds of THF were used as a solvent
(entry 1–5). Almost the same results were obtained as
shown in intries 1–3. The reaction in wet THF containing
No. Yield
(%)
E/Z
1
2
3
4
5
CCl3–
3
2a
2d
2e
2g
—
82
74
78
72
0
100:0
73:27
75:25
33:67
N.R.
Cl C2H5–
2.5
0.5
4.5
2
Cl (MeO)2CHCH2–
Cl p-NO2C6H4–
Cl p-MeOC6H4–

2340
S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
Scheme 4.
Scheme 5. Competition reaction between deacetylation reaction and debenzoylation reaction.
0.5 equiv. of water to the substrate (entry 4) afforded the
product in a reduced yield (52%). Furthermore, the reaction
in THF/H2O (1:1) (entry 5) did not proceed. Results as
shown in entries 1, 2, and 3 show that the drying method for
THF is not so important.
We examined the olefin synthesis among the Wittig
reaction, the Wittig–Horner reaction, and the present
deacetylation reaction. We tried three reactions to syn-
thesize ethyl 4,4,4-trichloro-2-methyl-2-butenoate.
As shown in Table 6, yield and E-stereoselectivity of the
deacetylation reaction with chloral were better than those of
the Wittig reaction. In the case of dichloroacetaldehyde,
yield of the deacetylation reaction became low, but
E-selectivity was better than that of the Wittig–Horner
reaction. As acidity of the a-proton of dichloroacetaldehyde
is stronger than that of ethyl 2-methylacetoacetate, aldol
reaction of the aldehyde itself may take place.
The base effect of the present reaction was examined for the
reaction of 1,3-dicarbonyl compound B-3 with chloral, and
the result is summarized in Table 5. The reaction using
1.5 equiv. of anhydrous K2CO3 as a base (entry 1) gave the
olefin 2i in the best yield (90%). The use of hydrate K2CO3
(0.5 equiv. H2O, entry 2) gave the olefin in a moderate yield.
However, the use of other alkali metal bases such as
Li2CO3, MgCO3, and KHCO3 did not give significant
results (entry 4–6). In most of the cases we recovered a part
of the starting material. Use of KOAc found to be effective
as shown in entry 7, in which the reaction gave 2i in 80%
yield with the same stereochemistry (E-form) as others.
Our synthetic strategy has been applied to the synthesis of
some natural products. We have utilized this halogen-
substituted a,b-unsaturated olefin moiety towards the
synthesis of a series of halogeno a-amino acids which
possess interesting biological activities.6–8 Electrochemical
reduction of the a,b-unsaturated ketones towards the
synthesis of exo-5-acetyl-endo-6-dichloromethylbicyclo
[2.2.1]hept-2-ene, and exo-5-acetyl-endo-6-chloromethyl-
bicyclo[2.2.1]hept-2-ene9 was also reported. 3-Hexen-2-one
(1b) can be transformed to substituted porphyrin.10 Other
olefinic compounds, for example, (3a), can be used for the
synthesis of compounds possessing antifungal, antitumor,
Table 4. Solvent effect in the synthesis of a,b-unsaturated ester 2i
Table 5. Base effect in the synthesis of a,b-unsaturated ester 2i
Entry
Solvent
Time (day)
Yield (%)
E/Z
1
2
3
4
5
6
7
8
9
10
THFa
2
5.5
5.5
0.5
4
3.5
2
2
90
92
89
52
0
100:0
100:0
100:0
100:0
N.R.
THFb
THFc
THFd
THF/H2O¼1/1
H2O
DME
0
N.R.
Entry
Base
Equiv. to B-3
Yield (%) Recovery (%)
E/Z
95
81
60
39
100:0
100:0
100:0
100:0
Acetone
DMFc
Hexane
1
2
3
4
5
6
7
K2CO3
K2CO3
K2CO3
KHCO3 1.5
Li2CO3 1.5
MgCO3 1.5
1.5
1.5þH2O (0.5)
90
52
37
67
3
0
100:0
100:0
100:0
100:0
100:0
N.R.
2
7
23
63
21
71
78
6
0.5
a
Dried over Na wires and benzophenone.
Commercial one was used without drying.
Dried over CaCl2.
b
c
d
0
80
KOAc
1.5
100:0
H2O (0.5 equiv.) was added.

S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
2341
Table 6. Comparison of olefin synthesis
olefin protons (6.4–7.9 ppm), and allylic protons of the
alkyl side chain (2.3–2.9 ppm). Stereochemistry between
olefin protons and the carbonyl groups was examined by
using allylic alcohols after reduction with DIBAL. In the
case of ester 2f, methylene protons of ethoxy and the olefin
proton showed cross peaks in NOESY. After reduction of
ester 2f to alcohol 20f, methylene protons of alcohol
(4.1 ppm) showed a more clear NOE effect with olefin
protons (5.8 ppm) than with allylic protons of the alkyl side
chain (2.2 ppm). Polychlorinated ester 2b showed cross
peaks between the terminal methyne proton (6.56 ppm)
and methylene protons (4.34 ppm) of the ethoxy group. For
a,b-unsaturated ketone, we examined NOE effect among
methyl protons of the acetyl group (2.4–2.5 ppm), olefin
proton (6.9–7.6 ppm) and allylic protons of the alkyl side
chain (2.4 ppm). Unfortunately, in the case of ketone 1f,
methyl protons of the acetyl group (2.4 ppm) and allylic
Entry
Reaction
Wittig
L
R
Yield
E/Z
1
2
CCl3
CHCl2
73
76
96:4
96:4
Wittig–Horner
Deacetylation
CCl3
CHCl2
38
58
57:43
35:65
3
CCl3
CHCl2
90
7
100:0
92:8
and plant growth inhibitory activities, for example, tulipalin
A which can be further transformed to pentaacetyl tulipo-
side A, 3-methyl-2(3H)-dihydrofuranone.11,12 If (E)-ethyl
4,4,4-trichloro-2-methyl-2-butenoate can be transformed to
(E)-ethyl 2-methyl-2-butenoate, it will be applicable to a
part of an insect pheromone and it can be used for the
synthesis of other compounds.13,14
1
proton of the alkyl side chain (2.4 ppm) overla0pped in H
NMR. After reduction of ketone 1f to alcohol 1 f, methyne
proton of alcohol (4.3 ppm) showed more clear cross peaks
with olefin proton (5.8 ppm) than with allylic protons of the
alkyl side chain (2.2 ppm). Compound 1e showed NOE
effect between olefin proton and methyl protons of the
acetyl group. The geometry of trichloroethylidenedihydro-
furanone 3b was also determined as Z-form by the NOESY
experiment.
Furthermore, the other unsaturated esters and ketones
moiety can be used for different types of reactions, for
example, Diels–Alder reaction,9,15 Favorskii reaction,16,17
and halogen allyl rearrangement18,19 and so on.
Olefin geometries were determined by NMR spectra
assisted by NOESY experiments as depicted in Figure 1.
For a,b-unsaturated ester, we examined NOE effect among
methylene protons of the ethoxy groups (4.2–4.3 ppm),
NOE and HMQC spectra of 2h (E/Z¼2:7), which was
prepared by Wittig–Horner reaction, are shown in Figures 2
and 3, respectively. Upon irradiation of CH3 signal at
1.98 ppm a NOE enhancement of the signals CHCl2
Figure 1. Determination of olefin geometry by NOESY.

2342
S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
Figure 2. NOE of 2h (E/Z¼2:7).
Figure 3. HMQC of 2h (E/Z¼2:7).

S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
Table 7. Olefin geometry and chemical shifts of olefin protons
2343
(1.92%) of (E)-2h and olefin H (6.0%) of (Z)-2h was
detected. As shown in Figure 3, signals of CHCl2
(6.43 ppm: E-form, 7.27 ppm: Z-form) and olefin proton
(6.20 ppm: Z-form, 6.92 ppm: E-form) in 1H NMR
showed cross peaks to those of carbons of CH ¼
(137.18 ppm: E-form, 138.33 ppm: Z-form) and CHCl2
(65.96 ppm: E-form, 66.16 ppm: Z-form) in 13C NMR
clearly, and signals of 1H and 13C NMR spectra of 2h were
assigned as shown in the Section 3, and the E/Z ratio was
determined clearly with the aid of these spectra.
Compounds
R
X
E/Z H (ppm)
J (Hz)
1a
1b
1d
1e
1f
CCl3
H
H
Cl
Cl
Cl
Cl
E
E
Z
Z
Z
Z
7.03
6.86
7.06
7.56
6.93
6.95
d 15.0
C2H5
CHCl2
CCl3
C2H5
n-C6H13
dt 15.8, 6.4
d 9.0
s
t 7.2
t 7.2
1g
Geometry and NMR data of olefins obtained by deacylation
reaction are summarized in Table 7.
In the case of the a-chlorinated ester, an olefin proton of the
(Z)-isomers appears further upfield than that of (E)-isomers.
However, the olefin proton of ester 2g showed the opposite
chemical shift. This may be due to the effect of the electron-
withdrawing nitro group and the benzene ring. The
stereochemistry of (Z)-2g was definitely confirmed by
X-ray analysis of the single crystal. The ORTEP drawing of
(Z)-2g is shown in Figure 4.
1c
CCl3
H
E
7.42
d 14.2
10f
10g
C2H5
n-C6H13
Cl
Cl
Z
Z
5.75
5.77
t 7.0
t 7.0
The present reaction has the following five advantages: (1) it
is highly stereoselective, (2) it proceeds under room
temperature, (3) it uses a weak and cheap base, K2CO3,
(4) it does not produce any phosphorus compounds harmful
to the environment, (5) experimental operation is simple.
This reaction contains a clean and environmentally-friendly
process because points (2)–(4) contribute to a hazard-free
environment.20
2a
2b
2c
2d
CCl3
H
E
E
E
Z
E
Z
E
Z
E
E
Z
Z
E
Z
E
7.22
7.22
7.72
6.43
7.05
6.48
7.07
6.44
7.07
7.26
7.94
6.20
6.91
6.21
7.40
d 15.0
d 9.4
s
t 7.8
t 7.2
t 7.4
t 7.0
t 7.8
t 7.4
s
CHCl2
CCl3
C2H5
Cl
Cl
Cl
2e
2f
CH2CH (OCH3)2 Cl
n-C6H13
p-NO2C6H4
CHCl2
Cl
The present method for the synthesis of a-chloro-a,b-
unsaturated esters and ketones seems to be superior to the
known methods such as the Wittig reaction and the
dehydroxylation reaction using sulfuric acid. Further
exploitation of this strategy towards the syntheses of
nucleoside analog, zidovudine (AZT)21a and insect phero-
mones of pines,21b and study on the mechanistic aspects are
currently under way in our group and the results will be
published elsewhere.
2g
2h
2i
Cl
s
Me
Me
dq 9.5, 1.5
dq 9.8, 1.5
q 1.5
q 1.6
CCl3
20f
3b
n-C6H13
Z
Z
5.79
7.19
t 7.0, 1.0
3. Experimental
CCl3
t 3.1
NMR spectra were recorded on Varian Gemini 200 or
JEOL AL300 instruments and calibrated using residual
undeuterated solvent as an internal reference. All IR
spectra were recorded on a JASCO FT/IR-5000 infrared
spectrophotometer as films. Elemental analyses were
performed on Perkin–Elmer 2400 series II CHNS/O
analyser. For thin layer chromatography aluminum sheets
Merck silica gel coated 60 F254 plates were used and the
plates were visualized with UV light and phosphomolybdic
acid (5% in EtOH). Merck silica gel 60 N (spherical,
neutral) (40–50 mm) was used for the flash chromatog-
raphy. The progress of the reaction was monitored by GC-
MS Shimazu QP 5000 at 70 eV. Some stereoisomers of
synthesized olefin were separated by preparative GC
(Yanagimoto G-2800): column (6/5 mmf£2 m) packed
with 10% liq. phase Apieson Grease L supported on
chromosorb W.
Figure 4. ORTEP drawing of (Z)-2g.

2344
S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
All reactions were carried out in oven-dried, septum-capped
flasks under N2. All liquid reagents were transferred via
oven-dried syringes. Solvents and reagents were dried and
distilled before use. THF was distilled from Na-benzo-
phenone ketyl before use.
J¼7.4 Hz, CH3), 2.41 (s, 3H, OvC–CH3), 2.41 (dq, 2H,
J¼7.4, 7.4 Hz, CH2), 6.93 (t, 1H, J¼7.2 Hz, CH2CHvC);
13C NMR (50 MHz, CDCl3) d 12.11, 23.07, 26.40, 133.26,
143.11, 192.15.
3.1.6. (Z)-3-Chloro-3-decen-2-one (Z)-1g. Yellow oil; Rf
0.45 (hexane/EtOAc, 4:1); IR (neat) n 2960, 2932, 2862,
1692, 1620, 1361, 1228 cm21; 1H NMR (500 MHz, CDCI3)
d 0.89 (t, J¼7.0 Hz, 3H), 1.23–1.40 (m, 6H), 1.50 (tt,
J¼7.5, 7.5 Hz, 2H), 2.39 (dt, J¼7.5, 7.5 Hz, 2H), 2.41 (s,
3H), 6.95 (t, J¼7.5 Hz, 1H); 13C NMR (50 MHz, CDCl3) d
14.03, 22.52, 26.49, 27.70, 29.02, 29.69, 31.51, 133.67,
142.02, 192.19. Anal. calcd for C10H17CIO: C, 63.65; H,
9.08. Found C, 63.76; H, 9.31.
3.1. General procedure for the deacetylation reaction
(typical synthesis of (E)-1a)
In a typical experimental procedure, 1.30 g (9.38 mmol)
of anhydrous potassium carbonate and 0.64 mL
(6.25 mmol) of 2,4-pentanedione in 5 mL of anhydrous
THF were placed in a 10 mL round bottomed flask. To
this mixture, 0.73 mL (7.5 mmol) of chloral was added at
room temperature via syringe under N2 atmosphere. After
2 days, the reaction mixture was diluted with 10–15 mL
of water and extracted with ether (20 mL£3). After
removal of the solvent, the residue was subjected for
column chromatography over silica gel using hexane and
then hexane–ethyl acetate (10–12%) as an eluent to
furnish the title compound as an yellow oil: the ketone 1a
(0.867 g) (74%) (E/Z, 100:0).
3.2. General procedure for the deacetylation reaction:
typical synthesis of 2a. (Procedure for solvent effect and
base effect are also same as this procedure)
In a typical experimental procedure, 1.30 g (9.38 mmol) of
anhydrous potassium carbonate and 0.80 mL (6.25 mmol)
of ethyl acetoacetate in 5 mL of anhydrous THF were placed
in a 10 mL round bottomed flask. To this mixture, 0.73 mL
(7.5 mmol) of chloral was added at room temperature by a
syringe under N2 atmosphere. After being stirring for 2
days, the reaction mixture was diluted with 10–15 mL of
water and the organic layer was extracted with ether
(20 mL£3). After removal of the solvent, the residue was
subjected for column chromatography over silica gel using
hexane and then hexane–ethyl acetate (10–12%) as an
eluent to furnish the title compound as a colorless oil: the
ester (E)-2a (0.517 g) (38%) (E/Z, 100:0).
3.1.1. (E)-5,5,5-Trichloro-3-penten-2-one (E)-1a.18,22,23
Yellow oil; Rf 0.45 (hexane/EtOAc, 4:1); IR (neat) n
3044, 3012, 1709, 1682, 1630, 1427, 1363, 1305, 1267,
1255, 1174, 1096, 1046, 1023, 1002, 965, 911, 853, 768,
729 cm21; 1H NMR (200 MHz, CDCl3) d 2.37 (s, 3H), 6.59
(d, J¼15 Hz, 1H), 7.03 (d, J¼15 Hz, 1H); 13C NMR
(50 MHz, CDCl3) d 28.79, 92.58, 127.96, 144.32, 196.49.
3.1.2. (E)-3-Hexen-2-one (E)-1b.10,24 Pale yellow oil; Rf
0.48 (hexane/EtOAc, 4:1); IR (neat) n 3586, 3536, 3316,
2974, 2940, 2882, 1698, 1680, 1630, 1547, 1512, 1462,
1427, 1363, 1336, 1286, 1257, 1183, 1131, 1093, 1071,
3.2.1. (E)-Ethyl 4,4,4-trichloro-2-butenoate (E)-2a.26
Colorless oil; Rf 0.60 (hexane/EtOAc, 4:1); IR (neat) n
2986 (C–C), 1729 (ester CvO), 1657 (CvC), 1468
(CvC). 1448 (CvC), 1396 (CvC), 1371 (CvC), 1309,
1276, 1183, 1096, 1033, 965, 866, 816, 774 cm21; 1H NMR
(200 MHz, CDCl3) d 1.33 (3H, t, J¼7.0 Hz, OCH2CH3),
4.27 (2H, q, J¼7.0 Hz, OCH2CH3), 6.39 (1H, d, J¼15.0 Hz,
Cl3 CCHvCH). 7.22 (1H, d, J¼15.0 Hz, Cl3CCHvCH);
13C NMR (50 MHz, CDCl3) d 14.13, 61.54, 92.16, 121.70,
146.01, 164.70.
1
1023, 980, 907, 876, 835, 768 cm21; H NMR (200 MHz,
CDCl3) d 1.08 (t, 3H, J¼7.4 Hz, CH3), 2.25 (s, 3H, OvC–
CH3), 2.25 (bdqd, 2H, CH2–CH3), 6.07 (dt, 1H, J¼15.8,
1.6 Hz, CH2CHvCH), 6.86 (dt, 1H, J¼15.8, 6.4 Hz, CH2
CHvCH); 13C NMR (50 MHz, CDCl3) d 12.22, 25.53,
26.82, 130.41, 149.82, 198.86.
3.1.3. (Z)-3,5,5-Trichloro-3-penten-2-one (Z)-1d.18 Pale
orange oil: Rf 0.54 (hexane/EtOAc, 4:1); IR (neat) n 3064,
3020, 2930, 2860, 1709, 1620, 1423, 1363, 1288, 1245,
1209, 1112, 1021, 994, 934, 917, 857, 756, 716, 659,
586 cm21; 1H NMR (200 MHz, CDCl3) d 2.49 (s, 3H), 6.58
(d, J¼9.2 Hz, 1H) 7.06 (d, J¼9.0 Hz, 1H); 13C NMR
(50 MHz, CDCl3), d 26.59, 65.22, 132.09, 135.20, 191.21.
3.2.2. (E)-Ethyl 2,4,4-trichloro-2-butenoate (E)-2b. Col-
orless oil; Rf 0.53 (hexane/EtOAc, 4:1); IR (neat) n 3066,
2988, 2942, 2912, 2876, 1725, 1632, 1526, 1466, 1448,
1394, 1371, 1336, 1270, 1218, 1104, 1042, 1000, 948, 880,
808, 762, 716, 640, 611 cm21; 1H NMR (200 MHz, CDCl3)
d 1.37 (t, J¼7.2 Hz, 3H), 4.34 (q, J¼7.0 Hz, 1H), 6.56
(d, J¼9.4 Hz, 1H), 7.22 (d, J¼9.4 Hz, 1H); 13C NMR
(50 MHz, CDCl3) d 14.06, 63.28, 65.00, 125.53, 136.64,
161.04. Anal. calcd for C6H7Cl3O2: C, 33.14; H, 3.24.
Found C. 33.22; H, 3.01.
3.1.4. (Z)-3,5,5,5-Tetrachloro-3-penten-2-one (Z)-1e.25
Light yellow oil; Rf 0.49 (hexane/EtOAc, 4:1); IR (neat) n
3058, 2980, 2930, 2872, 2348, 1796, 1711, 1605, 1421,
1363, 1303, 1278, 1214, 1094, 1019, 992, 942, 924, 855,
1
791, 731, 669, 615 cm21; H NMR (200 MHz, CDCl3) d
2.52 (s, 3H) 7.56 (s, 1H); 13C NMR (50 MHz, CDCl3) d
26.70, 89.48, 135.43, 139.47, 191.97.
3.2.3. (E)-Ethyl 2,4,4,4-tetrachloro-2-butenoate (E)-2c.27
Colorless oil: Rf 0.63 (hexane/EtOAc, 4:1); IR (neat) n
3066, 2988, 2944, 2912, 1734, 1622, 1466, 1448, 1394,
1371, 1292, 1255, 1174, 1089, 1044, 1004, 862, 828, 797,
3.1.5. (Z)-3-Chloro-3-hexen-2-one (Z)-1f.2,7 Yellow oil; Rf
0.41 (hexane/EtOAc, 4:1); IR (neat) n 3366, 2976, 2942,
2882, 1692, 1620, 1547, 1512, 1462, 1427, 1361, 1330,
1265, 1234, 1133, 1071, 1023, 1002, 975, 944, 899, 859,
1
772, 710, 650, 634, 603, 584 cm21; H NMR (200 MHz,
CDCl3) d 1.37 (t, J¼7.2 Hz, 3H) 4.35 (q, 2H, J¼7.2 Hz)
7.72 (s, 1H); 13C NMR (50 MHz, CDCl3) d 14.01, 63.50,
89.25, 129.79 141.51, 161.12.
795 cm21 1H NMR (200 MHz, CDCl3) d 1.11 (t, 3H,
;

S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
2345
3.2.4. Ethyl 2-chloro-2-pentenoate (2d) (E/Z, 4:1). Color-
less oil; Rf 0.55 (hexane/EtOAc, 4:1); IR (neat) n 2980,
2942, 2882, 1734, 1632, 1543, 1510, 1462, 1396, 1369,
1348, 1272, 1247, 1174, 1135, 1096, 1048, 986, 917, 864,
837, 774, 752 cm21; 1H NMR (200 MHz, CDCl3) d 1.09 (t,
J¼7.6 Hz, 3H), 1.33 (t, J¼7.2 Hz, 3H). 2.37 (dq, J¼7.6,
7.6 Hz, 1.6H), 2.55 (dq, J¼7.6, 7.6 Hz, 0.4H), 4.27 (q,
J¼7.2 Hz, 2H), 6.43 (t, J¼7.8 Hz, 0.2H), 7.05 (t, J¼7.2 Hz,
0.8H); 13C NMR (50 MHz, CDCl3) d 12.03, 14.13, 22.75,
62.07, 124.25, 143.49, 162.54. Anal. calcd for C7H11ClO2:
C, 51.70; H, 6.82. Found C, 51.48; H, 7.05.
1131, 1096, 1031, 977, 899, 760 cm21; 1H NMR (500 MHz,
CDCl3) d 1.33 (t, J¼7.0 Hz, 3H), 1.95 (d, J¼1.5 Hz, 3H),
4.25 (q, J¼7.0 Hz, 2H), 6.43 (dq, J¼9.5 Hz, 1H), 6.92 (dq,
J¼9.5, 1.5 Hz, 1H); 13C NMR (50 MHz, CDCl3) d 12.64,
14.15, 61.50, 65.96, 129.43, 137.18, 166.61. Anal. calcd for
C7H10Cl2O2: C, 42.66; H, 5.11. Found C, 42.71; H, 4.97.
3.2.11. (E)-Ethyl 2-methyl-4,4,4-trichloro-2-butenoate
(E)-2i.30 Pale yellow oil; Rf 0.60 (hexane/EtOAc, 4:1); IR
(neat) n 2986, 2942, 2912, 1775, 1721, 1642, 1460, 1446,
1388, 1371, 1348, 1261, 1129, 1027, 971, 878, 816, 774,
665 cm21; 1H NMR (200 MHz, CDCl3) d 1.34 (t, J¼7.1 Hz,
3H), 2.22 (d, J¼1.4 Hz, 3H), 4.25 (q, J¼7.1 Hz, 2H), 7.40
(q, J¼1.6 Hz, 1H); 13C NMR (50 MHz, CDCl3) d 13.91,
14.11, 61.79, 91.49, 135.42, 142.97, 166.58.
3.2.5. (Z)-Ethyl 2-chloro-2-pentenoate ((Z)-2d). Colorless
oil; Rf 0.55 (hexane/EtOAc, 4:1); 1H NMR (200 MHz,
CDCl3) d 1.07 (t, J¼7.6 Hz, 3H), 1.35 (t, J¼7.2 Hz, 3H),
2.56 (dq, J¼7.6, 7.6 Hz, 2H), 4.28 (q, J¼7.2 Hz, 2H), 6.44
(t, J¼7.8 Hz, 1H).
3.2.12. (Z)-Ethyl 2-methyl-4,4,4-trichloro-2-butenoate
1
((Z)-2i). Pale yellow oil; Rf 0.60 (hexane/EtOAc, 4:1); H
NMR d 1.34 (dt, J¼7.1, 1.5 Hz, 3H), 2.04 (d, J¼1.4 Hz,
3.2.6. (E)-Ethyl 2-chloro-2-pentenoate ((E)-2d). Colorless
oil: Rf 0.55 (hexane/EtOAc, 4:1); IR (neat) n 2980, 2942,
2882, 1734, 1632, 1462, 1369, 1272, 1247, 1133, 1096,
3H), 4.26 (q, J¼7.1, 1.4 Hz, 2H), 6.21 (q, J¼1.5 Hz, 1H).
1048, 986, 919, 864, 752 cm21
;
1H NMR (200 MHz,
3.3. General procedure for the synthesis of
2-chloro-1,3-dicarbonyl compounds. Synthesis of ethyl
a-chloro-benzoylacetate as a typical example
CDCl3) d 1.09 (t, J¼7.6 Hz, 3H), 1.33 (t, J¼7.2 Hz, 3H),
2.36 (dq, J¼7.6, 7.6 Hz, 2H), 4.27 (q, J¼7.0 Hz, 2H), 7.05
(t, J¼7.2 Hz, 1H); 13C NMR (50 MHz, CDCl3) d 12.09,
14.16, 22.80, 62.13, 124.25, 143.59, 162.61.
To ethyl benzoylacetate, thionyl chloride (1.1 equiv.) was
slowly added at 0 8C. The reaction mixture was stirred for
17 h at rt, and then poured into H2O (50 mL). The organic
compound was extracted with EtOAc (3£50 mL) and the
combined organic layer was dried over anhydrous MgSO4.
The solvent was evaporated under reduced pressure, and the
crude residue was distilled to give target molecule.
3.2.7. Ethyl 5,5-dimethoxy-2-chloro-2-pentenoate (2e)
(E/Z, 3:1). Pale yellow oil; Rf 0.45 (hexane/EtOAc, 4:1);
IR (neat) n 3400, 2330, 1638, 1620, 1369, 1176, 994, 735,
709 cm21; 1H NMR (200 MHz, CDCl3) d 1.33 (t, J¼7.2 Hz.
2.25H), 1.34 (t, J¼7.2 Hz, 0.75H), 2.69 (dd, J¼7.0, 5.6 Hz,
1.5H), 2.90 (dd, J¼7.4, 5.6 Hz, 0.5H), 3.35 (s, 4.5H), 3.36
(s, 1.5H), 4.28 (q, J¼7.2 Hz, 2H), 4.45 (t, J¼5.6 Hz, 0.25H),
4.53 (t, J¼5.6 Hz, 0.75H), 6.48 (t, J¼7.4 Hz, 0.25H), 7.07
(t, J¼7.0 Hz, 0.75H). Anal. calcd for C9H15ClO4: C, 48.55;
H, 6.79. Found C, 48.46; H, 6.65.
3.4. General procedure for the debenzoylation reaction
(E)-2a
In a typical experimental procedure, 1.30 g (9.38 mmol)
of anhydrous potassium carbonate and 1.08 mL
(6.25 mmol) of ethyl benzoylacetate in 5 mL of
anhydrous THF were placed in a 10 mL round bottomed
flask. To this mixture, 0.73 mL (7.5 mmol) of chloral
was added at room temperature by a syringe under N2
atmosphere. After being stirred for 3 days, the reaction
mixture was diluted with 10–15 mL of water and
extracted with ether (20 mL£3). After removal of the
solvent, the residue was subjected to column chromato-
graphy over silica gel using hexane and then hexane–
ethyl acetate (10–12%) as an eluent to furnish the title
3.2.8. Ethyl 2-chloro-2-nonenoate (2f) (E/Z, 82:18).28
Colorless oil; Rf 0.61 (hexane/EtOAc, 4:1); IR (neat) n
2938, 2836, 1721, 1638, 1450, 1371, 1338, 1270, 1125,
1
1052, 967, 866, 750 cm21; H NMR (200 MHz, CDCl3) d
0.88 (bs, 3H), 1.16–1.54 (m, 8H), 2.34 (dt, J¼7.2, 7.2 Hz,
1.64H), 2.53 (dt, J¼7.4, 7.4 Hz, 0.36H), 4.27 (q, J¼7.2 Hz,
2H), 6.44 (t, J¼7.8 Hz, 0.18H), 7.06 (t, J¼7.4 Hz, 0.82 Hz);
13C NMR (50 MHz, CDCl3)29 d 14.01, (14.51), 22.51,
(22.63), 27.64, (28.87), 28.96, 29.39, 29.93, 31.52, (61.82)
62.10, (122.45), 124.63, 142.47, (145.08), 162.60.
compound as
(5.13 mmol) (82%) (E/Z, 100:0).
a colorless oil: ester 2a 1.115 g
3.2.9. (Z)-Ethyl 2-methyl-4,4-dichloro-2-butenoate ((Z)-
2h). Pale yellow oil; Rf 0.61 (hexane/EtOAc, 4:1); IR (neat)
n 2986, 2934, 1717, 1651, 1452, 1373, 1350, 1286, 1261,
3.4.1. Ethyl 2-chloro-3-(4-nitrophenyl)-2-propenoate
(2g) (E/Z, 33:67).30–32 Green crystal; mp 88–92 8C (from
hexane); Rf 0.35 (hexane/EtOAc, 4:1); IR (KBr) n 3100,
2992, 2902, 2850, 1717, 1618, 1597, 1520, 1475, 1462,
1446, 1412, 1348, 1323, 1292, 1267, 1203, 1112, 1073,
1035, 996, 926, 890, 855, 814, 760, 745, 692, 685 cm21; 1H
NMR (200 MHz, CDCl3) d 1.20 (t, J¼7.2 Hz, 0.99H), 1.40
(t, J¼7.2 Hz, 2.01H), 4.22 (q, J¼7.2 Hz, 0.68H), 4.38
(q, J¼7.2 Hz, 1.32H), 7.26 (s, 0.33H), 7.46 (d, J¼8.4 Hz,
0.35H), 7.94 (s, 0.67H), 7.96 (d, J¼9.2 Hz, 0.65H), 8.21
(d, J¼8.8 Hz, 0.35H), 8.28 (d, J¼8.8 Hz, 0.65H); 13C NMR
(50 MHz, CDCl3)29 d (13.72), 14.15, (62.64), 63.06,
1
1222, 1143, 1098, 1023, 1006, 884, 748, 702 cm21; H
NMR (500 MHz, CDCl3) d 1.33 (t, J¼7.0 Hz, 3H), 1.98 (d,
J¼1.5 Hz, 3H), 4.25 (q, J¼7.0 Hz, 2H), 6.20 (dq, J¼10.0,
1.5 Hz, 1H), 7.27 (d, J¼9.5 Hz, 1H); 13C NMR (50 MHz,
CDCl3) d 14.07, 19.86, 61.34, 66.16, 128.46, 138.33,
165.87. Anal. calcd for C7H10Cl2O2: C, 42.66; H, 5.11.
Found C, 42.71; H, 4.97.
3.2.10. (E)-Ethyl 2-methyl-4,4-dichloro-2-butenoate
((E)-2h). Pale yellow oil; Rf 0.61 (hexane/EtOAc, 4:1); IR
(neat) n 2986, 1721, 1651, 1462, 1446, 1371, 1280, 1228,

2346
S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
(123.49), 123.65, 126.07, (129.25), 131.07, 134.22,
(134.86), 139.07, 147.95, 162.54.
4:1); IR (neat) n 3058, 2990, 2928, 1773, 1671, 1562, 1522,
1481, 1460, 1423, 1386, 1342, 1278, 1207, 1120, 1042, 969,
1
926, 886, 837, 760, 623, 588, 551, 443 cm21; H NMR
3.5. X-ray structure determination of (Z)-2g
(200 MHz, CDCl3) d 3.35 (dt, 2H, J¼7.2, 3.2 Hz, –CH2–).
4.48 (t, 2H, J¼7.2 Hz, –CH2–O–), 7.26 (t, 1H, J¼3.2 Hz,
CvCH); 13C NMR (50 MHz, CDCl3) d 26.01, 66.02, 91.40,
129.07, 139.78, 170.19. Anal. calcd for C6H5Cl3O2: C,
33.45; H, 2.34. Found C, 33.25; H, 2.44.
Crystallographic data for (Z)-2g. C11H10O4N1Cl1, colorless
crystal of dimension 0.1£0.2£0.3 mm3, mol.weight 255.66,
˚
monoclinic, P21/n, a¼15.347(3), b¼4.011(4), c¼19.21(2) A,
3
b¼105.64(6)8, V¼1139(1) A , Z¼4, r¼1.49 g cm23. The
˚
X-rays diffraction data were collected on a CAD4 Enraf-
Nonius automatic four-circle diffractometer (graphite
monochromator, Cu Ka radiation (1.54184<), v–2u scan
method, u#57.38).
3.7. Competition reaction
Anhydrous potassium carbonate (1.34 g, 9.68 mmol) and
1.08 g (6.67 mmol) of 1-phenyl-1,3-butanedione in 5 mL of
anhydrous THF was placed in a 10 mL round bottomed
flask. To this mixture, 0.75 mL (7.74 mmol) of chloral was
added at room temperature via syringe under N2 atmo-
sphere. After being stirred for 16 h, the reaction mixture was
diluted with 10–15 mL of water and the organic layer was
extracted with ether (20 mL£3). After removal of the
solvent, the residue was subjected for column chromato-
graphy over silica gel using hexane and then hexane–ethyl
acetate (10–12%) as an eluent to furnish the title compound
as an yellow oil: the ketone 1a (0.219 g, 18%) (E/Z, 100:0),
and the ketone 1c (0.646 g, 39% (E/Z, 100:0) as a pale
yellow crystal.
A total of 2477 reflections were measured, of which 1975
were unique with I.3s. The stability of crystals and of
experimental conditions was checked every 2 h using three
control reflections, while the orientation was monitored
every 200 reflections by centering two standards. Correc-
tions for Lorentz and polarization effects and absorption
correction were applied (m¼30.56 cm21). The structure was
solved by direct methods and difference Fourier syntheses
using SIR program33 and MolEN package.34 All non-
hydrogen atoms were refined anisotropically, H-atoms were
located in DF maps and were refined isotropically. The final
R values were R¼0.051, Rw¼0.064 for 1857 unique
reflections with F 2$3s. All calculations were carried out
on a DEC Alpha Station 200 computer, all figures were
made using the program PLATON.35
3.7.1. (E)-1-Phenyl-4,4,4-trichloro-2-penten-1-one (E)-
1c.15,19 Pale yellow crystal; mp 95–97 8C (from hexane);Rf
0.50 (hexane/EtOAc,4:1); IR (KBr) n 3050, 2366, 2330,
1995, 1972, 1903, 1818, 1773, 1678, 1626, 1597, 1578,
1495, 1452, 1398, 1346, 1334, 1311, 1296, 1278, 1214,
1187, 1164, 1100, 1033, 1013, 955, 870, 793, 768, 733, 714,
Crystallographic data for the structure 1 will be deposited
with the Cambridge Crystallographic Data Centre.
1
685, 675, 615, 565, 524, 497 cm21; H NMR (200 MHz,
3.6. General procedure for the deacetylation reaction
(typical synthesis of (Z)-3b)
CDCl3), d 7.27 (d, 1H, J¼14.2 Hz, CHvCHCCl3, 7.42 (d,
1H, J¼14.2 Hz, CHvCHCCl3), 7.47–7.70 (m, 3H, Ph),
7.99 (d, 2H, Ph); 13C NMR (50 MHz, CDCl3) d 92.91,
124.03, 128.71, 128.88, 133.86, 136.72, 145.40, 188.77.
In a typical experimental procedure, 1.30 g (9.38 mmol)
of anhydrous potassium carbonate, 0.67 mL (6.25 mmol) of
2-acetylbutyrolactone in 5 mL of anhydrous THF was
placed in a 10 mL round bottomed flask. To this mixture,
0.73 mL (7.5 mmol) of chloral was added at room
temperature via syringe under N2 atmosphere. After being
stirring for 17 h, the reaction mixture was diluted with 10–
15 mL of water and extracted with ether (20 mL£3). After
removal of the solvent, the residue was subjected for column
chromatography over silica gel using hexane and then
hexane–ethyl acetate (10–12%) as an eluent to furnish the
title compound as a yellow oil. It was gave the lactone 3b
0.739 g (3.43 mmol) (55%) (E/Z, 0:100).
3.8. General procedure for the Wittig reaction (typical
synthesis of 2i)
To a suspension of (carbethoxyethylidene) triphenyl
phosphorane (0.391 g, 1.08 mmol) in 5 mL of THF was
added dropwise the chloral (0.1 mL, 1.04 mmol). The
reaction mixture was stirred at room temperature for 16 h.
The reaction mixture was poured into ice cold brine (20 mL)
and extracted by diethyl ether (20 mL£3). The combined
organic layer was dried over anhydrous MgSO4, filtered,
and the solvent removed under reduced pressure. The crude
material was subjected for column chromatography over
silica gel using hexane and then hexane–ethyl acetate (10–
12%) as an eluent to furnish the title compound as a pale
yellow oil: the ester 2i (73%) (E/Z-96.4).
3.6.1. 3-Methylene-2(3H)-dihydrofuranone (3a).11,12
Colorless oil; Rf 0.13 (hexane/EtOAc, 4:1); IR (neat) n
3586, 3514, 3104, 2994, 2924, 2730, 2526, 2382, 2232,
2032, 1883, 1760, 1667, 1638, 1528, 1489, 1439, 1402,
1373, 1267, 1118, 1027, 965, 948, 812, 766, 696, 617 cm21
;
3.9. General procedure for the Wittig–Horner reaction
(typical synthesis of 2i)
1H NMR (200 MHz, CDCl3) d 2.96 (tdd, 2H, J¼7.4, 2.8,
2.8 Hz, –CH2–), 4.35 (t, 2H, J¼7.4 Hz, –CH2–O–), 5.65
(t, 1H, J¼2.6 Hz, CvCH), 6.21 (t, 1H, J¼2.8 Hz, CvCH);
13 C NMR (50 MHz, CDCl3) d 27.20, 65.18, 122.09, 133.46,
170.63.
To a suspension of sodium hydride (60% in oil, 0.087 g,
2.18 mmol) in 5 mL of THF was added dropwise triethyl
2-phosphonopropionate (0.223 mL, 1.04 mmol). After the
evolution of hydrogen ceased, chloral (0.1 mL, 0.153 g,
1.04 mmol) was added. The reaction mixture was stirred
at room temperature for 16 h. Then reaction mixture was
3.6.2. (Z)-3-(2,2,2-Trichloroethylidene)-2(3H)-dihydro-
furanone (Z)-3b.36 Yellow oil; Rf 0.35 (hexane/EtOAc,

S. Nakatsu et al. / Tetrahedron 60 (2004) 2337–2349
2347
poured into ice-cold water (20 mL) and the organic
compound was extracted by ether. After drying over
organic layer by MgSO4, the solvent was evaporated.
Silica gel column chromatography afforded the ester 2i
(31%) (E/Z, 57:43).
J¼8.0 Hz, 0.004H) 5.87 (tt, J¼7.0, 1.0 Hz, 0.996H)
(500 MHz, CDCl3) d 0.88 (t, J¼7.0 Hz, 3H), 1.20–1.44
(m, 8H), 1.94 (bs, 1H), 2.20 (q, J¼7.5 Hz, 2H), 4.18 (s, 2H),
5.79 (td, J¼7.0, 1.0 Hz, 1H); 13C NMR (50 MHz, CDCl3) d
14.05, 22.57, 28.13, 28.35, 28.88, 31.61, 66.94, 127.63,
132.95. Anal. calcd for C9H17ClO: C, 61.18; H, 9.70.
Found: C, 60.98; H, 9.79.
3.10. Reduction of a,b-unsaturated carbonyl compounds
3.10.1. (Z)-3-Chloro-3-hexen-2-ol (Z)-10f. A solution of
compound 1f (0.138 g, 1.04 mmol) in dry THF (5 mL) was
purged with N2 and cooled to 278 8C, and then a 0.9 M
solution of diisobutylaluminum hydride (DIBAL) (1.12 mL,
1.01 mmol) in hexane was slowly added. The mixture was
stirred at 260 8C for 2 h. The reaction mixture was
quenched with 10% aq. HCl. and the organic compounds
were extracted with ether (20 mL£3). The combined
organic phase was dried over (MgSO4) and the solvent
was removed under reduced pressure. The residue was
purified by column chromatography using hexane/EtOAc,
(10:1); as an eluent to yield 76 mg (54%) of a 10f as (Z)
colorless oil Rf 0.24 (hexane/EtOAc, 4:1); IR (neat) n 3330,
2974, 2938, 2880, 1659, 1462, 1412, 1373, 1323, 1288,
Acknowledgements
We thank Dr. Dipak Kalita for advising and helping to write
this paper and SC-NMR Laboratory of Okayama University
for the measurement of NMR spectra. We also thank Mr.
Hiroyasu Ono and Miss Mayumi Tsuji for the preliminary
experiments.
References and notes
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1.36 (dd, J¼6.5, 2.0 Hz, 3H), 2.10 (bs, 1H), 2.19 (dq, J¼7.5,
7.5 Hz, 2H), 4.34 (q, J¼6.5 Hz, 1H), 5.75 (t, J¼7.0 Hz, 1H)
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127.27, 136.92. Anal. calcd for C6H11ClO: C, 53.54; H,
8.24. Found C, 53.41; H. 8.21.
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ether. The combined organic phases was dried over
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graphy over silica gel using hexane/EtOAc (10:1) as an
eluent to yield (Z)-20f (71 mg, 85%) as a colorless oil: Rf
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2862, 1659, 1640, 1462, 1454, 1412, 1379, 1098,
1
1015 cm21; H NMR (500 MHz, (CD3)2C¼O) d 0.87 (t,
J¼7.0 Hz, 3H), 1.22–1.44 (m, 8H), 2.18 (q, J¼7.5 Hz, 2H),
4.09 (dd, J¼6.0, 1.5 Hz, 2H) 4.38 (t, J¼6.5 Hz, 1H), 5.70 (t,

2348
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