Acid-catalyzed intramolecular addition of a carboxy group to vinylsilanes

Article abstract of DOI:10.1016/S0022-328X(03)00533-3

In the presence of a catalytic amount of TsOH·H₂O or TiCl₄, 5-silyl-4-pentenoic acids (1), namely vinylsilanes with a carboxy group, were smoothly cyclized to γ-lactones in good to high yields. The difference in the geometry of the carbon-carbon double-bond did not affect the reaction rate. The TiCl₄-catalyzed cyclization of the substrates bearing a phenyl or alkyl group at the homoallylic position showed moderate cis -selectivity, while introduction of a substituent into the allylic position led to high trans-selectivity.

Full text of DOI:10.1016/S0022-328X(03)00533-3

Journal of Organometallic Chemistry 686 (2003) 242Á250
/
www.elsevier.com/locate/jorganchem
Acid-catalyzed intramolecular addition of a carboxy group to
vinylsilanes
Katsukiyo Miura *, Joji Hayashida, Tatsuyuki Takahashi, Hisashi Nishikori,
Akira Hosomi *
Department of Chemistry, 21st Century COE, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
CREST, Science and Technology Corporation (JST), Ibaraki 305-8571, Japan
Received 8 April 2003; received in revised form 28 May 2003; accepted 28 May 2003
Abstract
In the presence of a catalytic amount of TsOH×
/
H2O or TiCl4, 5-silyl-4-pentenoic acids (1), namely vinylsilanes with a carboxy
carbon double-
bond did not affect the reaction rate. The TiCl4-catalyzed cyclization of the substrates bearing a phenyl or alkyl group at the
group, were smoothly cyclized to g-lactones in good to high yields. The difference in the geometry of the carbonÃ
/
homoallylic position showed moderate cis-selectivity, while introduction of a substituent into the allylic position led to high trans-
selectivity.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Acid Catalyst; Cyclization; Vinylsilane; g-lactone
1. Introduction
straightforward route to g- and d-lactones [5,6]. How-
ever, the cyclization of alkenoic acids requires high
concentration of the acid catalyst, which causes the
formation of cyclic a-enones, skeletal rearrangements,
and epimerization of the initially formed stereogenic
center. Thus, this method is not necessarily suitable for
efficient and stereoselective synthesis of lactones. On the
basis of our previous studies, we expected a carboxy
group to be reactive to an internal vinylsilane under
milder conditions, and our efforts were directed toward
the development of a highly efficient route to substituted
lactones using vinylsilanes. We herein report the acid-
catalyzed cyclization of 5-silyl-4-pentenoic acids (1) to g-
lactones and its stereochemical aspects.
The protonation of vinylsilanes is known to take place
at the a-position to form b-silylcarbenium ions hyper-
conjugatively stabilized by the adjacent carbonÃ
bond [1]. The carbenium ions are thermodynamically
stable; however, they are subject to desilylation leading
to alkenes by nucleophilic attack of the counteranion or
a solvent molecule to silicon. Previously, we have
reported that the carbenium ions derived from vinylsi-
lanes can be efficiently trapped with internal oxygen and
/silicon
nitrogen nucleophiles (Scheme 1) [2Á4]. The acid-
/
catalyzed cyclizations of vinylsilanes bearing a hydroxy
or amino group are valuable for stereoselective con-
struction of five- and six-membered cyclic ethers and
amines.
Intramolecular addition of a carboxy group to
alkenes under catalysis by a strong acid provides a
2. Results and discussion
2.1. Cyclization of (Z)- and (E)-5-benzyldimethylsilyl-
4-pentenoic acids (1a)
* Corresponding authors. Present address: Department of
Chemistry, 21st Century COE, Graduate School of Pure and
Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-
In the presence of TsOH×
/
H2O (5 mol%), (Z)-vinylsi-
lane (1a) was slowly cyclized to g-lactone (2a) at room
temperature (entry 1 in Table 1). Increasing both the
amount of the acid catalyst and the reaction tempera-
8571, Japan. Tel.: ꢀ
/
81-295-83-4237; fax: ꢀ81-295-83-6503.
/
E-mail address: hosomi@chem.tsukuba.ac.jp (A. Hosomi).
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00533-3

K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á
/250
243
2.2. Stereochemistry in intramolecular addition of a
carboxy group
Our previous study disclosed that acid-catalyzed
intramolecular addition of a hydroxy group to a
vinylsilane proceeds in a stereospecific syn manner
(3a). To gain stereochemical insight into the present
reaction, a-deuterated (Z)- and (E)-vinylsilanes (1aÁ
were used. In contrast with the previous result, the
TsOH-catalyzed cyclization of 1aÁ1d gave a diastereo-
/
1d)
Scheme 1.
/
meric mixture of 4 and 5 with low or no syn-addition
selectivity.
ture was fairly effective in promoting the cyclization.
Thus, the reaction with 10 mol% of the catalyst at 60 8C
was completed within 12 h to give 2a in 92% yield (entry
3). TiCl4 effectively promoted the cyclization even at
room temperature, although a certain amount of
desilylation product 3 was formed (entry 4). (E)-
Vinylsilane (1a) also was efficiently converted into 2a
under these acidic conditions (entries 5 and 6). Un-
expectedly, the reactivity of (E)-1a was similar to that of
(Z)-1a. This result stands in sharp contrast with our
previous observation that (Z)-vinylsilanes are more
reactive than the corresponding E-isomers in acid-
catalyzed intramolecular addition of a hydroxy group
[2,4].
To make sure of the directing effect of the silyl group,
we attempted the cyclization of (Z)-4-dodecenoic acid
under similar conditions (Eq. (1)). As a result, no
cyclized product was obtained and the substrate was
intact. This result clearly shows that the silyl group of 1a
plays a crucial role in accelerating the acid-catalyzed
cyclization.
ð2Þ
A plausible reaction mechanism for the cyclization of
(Z)-1aÁ1d is as follows (Scheme 2): (1) a proton
/
attaches to the carboxy group; (2) the proton on the
oxygen atom shifts to the a-carbon; (3) the resultant b-
silylcarbenium ion B, which may be a transition state,
turns to its conformer C1 stabilized by sÁp conjugation
/
at the least motion [7]; (4) C1 can be converted into
conformer C2 reversibly; (5) intramolecular attack of
the carboxy oxygen from the side opposite to the silyl
group gives syn-addition product 4 from C1 or anti-
addition product 5 from C2. Since (Z)-1a is similar in
reactivity to (E)-1a, the rate-controlling step would be
the last (cyclization) step rather than the intramolecular
protonation step leading to C1 and C2 through B. On
the other hand, in the case with vinylsilanes bearing a
(1)
Table 1
Optimization of reaction conditions for acid-catalyzed cyclization of vinylsilanes 1a a
Entry
Substrate
Catalyst (mol%)
Temperature (8C)
Time (h)
Yield of 2a (%)
1
2
3
4
5
6
(Z)-1a
(Z)-1a
(Z)-1a
(Z)-1a
(E)-1a
(E)-1a
TsOH×
TsOH×
TsOH×
/
H2O (5)
H2O (5)
H2O (10)
rt
48
36
12
16
12
16
31 b
80
/
60
60
rt
/
92
TiCl4 (5)
TsOH×H2O (10)
TiCl4 (5)
80
92
/
60
rt
77
a
All reactions were carried out with 1a (0.50 mmol) in CHCl3 (2.5 ml).
The substrate (Z)-1a was recovered in 64% yield.
b

244
K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á250
/
2.3. Stereoselective synthesis of disubstituted g-lactones
The acid-catalyzed cyclization of 2-substituted 5-silyl-
4-pentenoic acids (1bÁ
lactones (2bÁ2d) in good yields with moderate selectivity
with respect to the formation of the isomer with the side
chains cis to each other (entries 1Á8 in Table 2). The use
of TsOH×H2O at 60 8C led to higher yields of 2, while
/
1d) gave a,g-disubstituted g-
/
/
/
the TiCl4-catalyzed reaction at room temperature
showed higher cis-diastereoselectivity. The presence of
a phenyl substituent in the case of 1d brought about a
rapid cyclization (entry 7). Lowering the reaction
temperature was ineffective in improving the stereose-
lectivity (entry 8). The geometry of the double-bond did
not affect the sense of diastereoselectivity (entries 5 and
6).
Scheme 2.
We next examined the cyclization of 3-substituted
hydroxy group, a marked difference in reactivity be-
tween (Z)- and (E)-isomers suggests that the cyclization
rate should be controlled by the protonation step 3a.
The change of rate-controlling step is attributable to low
nucleophilicity of the carboxy group, which may decele-
rate the last step. The low selectivity toward syn-
addition of the carboxy group supports the relatively
slow cyclization step because the deceleration would
provide enough time for the rotation of C1 to C2.
(Z)-5-silyl-4-pentenoic acids (1e and 1f) (entries 9Á13 in
/
Table 2). The substitution at the allylic position
decreased the cyclization rate; however, high diastereos-
electivity toward the formation of trans-b,g-disubsti-
tuted g-lactones (2e and 2f) was observed in the TiCl4-
catalyzed system. The use of an increased amount of
TiCl4 achieved efficient and highly stereoselective trans-
formation (entries 10 and 12). The cyclization of (E)-1f
proceeded efficiently under the same conditions
Table 2
Stereoselective cyclization of vinylsilanes 1 a
b
Entry
Substrate
Method
Temperature (8C)
Time (h)
Yield (%)
cis:trans
R1
R2
1
Hex
H
H
(Z)-1b
(Z)-1b
(Z)-1c
(Z)-1c
(E)-1c
(E)-1c
(Z)-1d
(Z)-1d
(Z)-1e
(Z)-1e
(Z)-1f
(Z)-1f
(E)-1f
TsOH×
TiCl4 (5)
TsOH×H2O (10)
TiCl4 (5)
TsOH×H2O (10)
TiCl4 (5)
TiCl4 (5)
TiCl4 (5)
/
H2O (10)
60
rt
20
22
12
16
12
12
1
89
74
92
85
95
80
82
81
72
79
63 c
83
88
61:39
78:22
60:40
83:17
77:23
78:22
71:29
69:31
13:87
2
3
i-Pr
/
60
rt
4
5
/
60
rt
6
7
Ph
H
H
rt
8
0
12
21
16
48
16
16
9
Pen
Ph
TsOH×
TiCl4 (10)
TsOH×H2O (10)
/H2O (10)
60
rt
10
11
12
13
B
/
1:99
7:93
1:99
18:82
H
/
60
rt
TiCl4 (10)
B
/
TiCl4 (10)
rt
a
All reactions were carried out with 1a (0.50 mmol) in CHCl3 (2.5 ml).
Determined by 1H-NMR analysis.
The substrate was recovered in 17% yield.
b
c

K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á
/250
245
although the trans-diastereoselectivity was diminished
in some degree (entry 13).
To determine the relative configurations of g-lactones
2b and 2c, they were converted into the corresponding
tetrahydrofurans 6b and 6c as shown in Scheme 3. Eliel
et al. [8] reported that, in 13C-NMR spectra of 2,4-
disubstituted tetrahydrofurans, the signals of C-2, C-3
and C-4 of the cis-isomers appear at lower field than
those of the trans-isomers. On the basis of this criterion,
the major isomers of 6b and 6c were determined to
possess the cis-configuration. The stereochemical as-
signment of 2d was based on NOE experiments of the
major isomer. Irradiation of one b-proton on the ring
showed considerable enhancements (ꢀ10%) of both a-
/
Scheme 4.
and g-protons. This observation agrees with the cis-
configuration of the major isomer. The relative config-
urations of 2e and 2f were deduced from their 1H-NMR
data. In the trans-isomers, b- and g-protons on the ring
the diastereoselectivity, the present situation is in the
middle of these two extremes, i.e., the rotation rates of
E1 and E2 are comparable with their cyclization rates.
The intramolecular protonation of D would proceed
mainly via energetically favorable conformation Dch-eq
to give b-silylcarbenium ion E1 (Scheme 5). A part of E1
is converted into E2 reversibly. The intermediates E1
are shielded by the vicinal CÃ/C bond, and their signals
should be observed at higher field than those of the cis-
isomers [9]. Judging from this consideration, the major
isomers of 2e and 2f have the trans-configuration.
and E2 are cyclized to cis- and trans-2bÁ2d, respec-
/
2.4. Origin of stereoselectivity
tively, probably via chair-like conformations E1ch and
E2ch. Since E2ch is energetically less favored than E1ch
due to the presence of a pseudoaxial substituent, the
cyclization of E1 would be faster than that of E2.
On the basis of Scheme 2, a plausible mechanism for
the cyclization of 1bÁ1d is shown in Scheme 4, in which
/
the b-silylcarbenium ion intermediate corresponding to
B is omitted for simplicity. The b-silylcarbenium ions E1
and E2 are generated by internal protonation from the
top (path a) and bottom (path b) sides, respectively.
When the rotation between E1 and E2 is much slower
than their cyclizations, the diastereoselectivity is deter-
mined in the protonation step. In this situation, the
selectivity would be strongly affected by the geometry of
Accordingly, the cis-selective cyclization of 1bÁ1d is
/
attributable to the diastereoface-selective protonation
and the fast cyclization of E1.
Similarly, the trans-selectivity with 1e and 1f can be
rationalized by selective formation of b-silylcarbenium
ion G1 and its fast cyclization to trans-2e and 2f
(Scheme 6). The high diastereoselectivity would arise
from 1,3-allylic strains by the pseudoaxial substituents
(R2) of Fch-ax and G2ch, which severely destabilize these
conformations [10].
the CÃ
/
C double bond as in the cyclization of vinylsi-
lanes bearing a hydroxy group (3a). When the rotation is
much faster, the diastereoselectivity depends on the
relative cyclization rates of E1 and E2, and the alkene
geometry does not affect the stereochemical outcome.
Judging from the low syn-addition selectivity with (Z)-
1aÁ
/
1d and a slight influence of the alkene geometry on
Scheme 3.
Scheme 5.

246
K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á250
/
dried over Na2SO4 and evaporated. Purification of the
crude product by silica gel column chromatography
gave (Z)-5-benzyldimethylsilyl-4-pentenoic acid (1a,
4.70 g, 18.8 mmol) in 63% yield.
3.1.1. (Z)-5-Benzyldimethylsilyl-4-pentenoic acid ((Z)-
1a)
b.p. 150 8C (bath temp., 0.4 Torr). IR (neat) 2920 (br),
1
1716 cmꢂ1; H-NMR (CDCl3) d 0.12 (s, 6H), 2.17 (s,
2H), 2.34Á
(dm, Jꢃ14.0 Hz, 1H), 7.00Á
2H) ppm; 13C-NMR (CDCl3) d ꢂ
(CH2), 28.45 (CH2), 33.87 (CH2), 124.00 (CH), 128.06
(CHꢁ2), 128.11 (CHꢁ2), 128.89 (CH), 139.73 (C),
146.85 (CH), 179.26 (C) ppm; MS m/z (rel. intensity)
PhCH2, 17], 75 [100]. Anal. Calcd. for
/
2.39 (m, 4H), 5.54 (d, Jꢃ
7.09 (m, 3H), 7.18Á
1.81 (CH3ꢁ2), 26.47
/
14.0 Hz, 1H), 6.29
/
/
/7.27 (m,
/
/
/
/
157 [Mꢀ Ã
/
Scheme 6.
C14H20O2Si: C, 67.69; H, 8.12. Found: C, 67.44; H,
8.28%.
3. Experimental
3.1.2. (E)-5-Benzyldimethylsilyl-4-pentenoic acid ((E)-
1a)
Unless otherwise noted, all reactions and distillations
were carried out under N2. Carboxylic acids 1 were
synthesized from the corresponding alcohols by oxida-
tion with PDC [11]. For the preparation of the starting
alcohols, see the supporting information of Ref [3a]. A
typical procedure for the synthesis of 1 is described
below. Solvents were dried by distillation from sodium
b.p. 160 8C (bath temp., 0.4 Torr). IR (neat) 2950 (br),
1
1710 cmꢂ1; H-NMR (CDCl3) d 0.02 (s, 6H), 2.10 (s,
2H), 2.36Á
(dm, Jꢃ18.6 Hz, 1H), 6.96Á
2H) ppm; 13C-NMR (CDCl3) d ꢂ
(CH2), 31.11 (CH2), 32.98 (CH2), 123.92 (CH), 128.03
(CHꢁ2), 128.19 (CHꢁ2), 129.18 (CH), 139.91 (C),
/
2.47 (m, 4H), 5.66 (d, Jꢃ
7.08 (m, 3H), 7.17Á
3.44 (CH3ꢁ2), 26.04
/
18.6 Hz, 1H), 5.99
/
/
/7.24 (m,
/
/
metal/benzophenone ketyl (THF, Et2O), CaCl2Ã
/
/
/
NaHCO3 (EtOH-free CHCl3) and CaH2 (DMF). TiCl4
was simply distilled and stored as a CH2Cl2 solution (1.0
M). All other commercially obtained reagents were used
as received.
145.25 (CH), 179.65 (C) ppm. Anal. Calcd. for
C14H20O2Si: C, 67.69; H, 8.12. Found: C, 67.59; H,
8.06%.
Infrared spectra were measured on a JASCO FT/IR-
1
3.1.3. (Z)-4-Dodecenoic acid
b.p. 150 8C (bath temp., 0.4 Torr). IR (neat) 2925 (br),
230 spectrophotometer. H-NMR spectra at 270 MHz
and 13C-NMR spectra at 67.7 MHz in CHCl3 were
recorded on a JEOL JNM-EX-270 spectrometer. The
chemical shifts (d) are reported with reference at 0.00
ppm (Me4Si) or 7.26 ppm (CHCl3) for the proton and at
77.00 ppm (centered on the signal of CDCl3) for the
carbon. The proton of the carboxy group of 1 was not
detected due to broadening. Mass spectra were mea-
sured (by EI method) on a Shimadzu GCMS-QP5050
instrument. Elemental analyses were performed by the
Analysis Center of the University of Tsukuba.
1
1712 cmꢂ1; H-NMR (CDCl3) d 0.88 (t, Jꢃ
/
6.7 Hz,
6.6 Hz, 2H), 2.32Á2.44
5.49 (m, 2H) ppm; 13C-NMR (CDCl3) d
3H), 1.27 (br s, 10H), 2.04 (q, Jꢃ
/
/
(m, 4H), 5.31Á
/
14.07 (CH3), 22.49 (CH2), 22.65 (CH2), 27.19 (CH2),
29.19 (CH2), 29.24 (CH2), 29.60 (CH2), 31.84 (CH2),
34.20 (CH2), 126.87 (CH), 131.89 (CH), 179.89 (C) ppm.
Anal. Calcd. for C12H22O2: C, 72.68; H, 11.18. Found:
C, 72.66; H, 11.16%.
3.1.4. (Z)-5-Benzyldimethylsilyl-4-deuterio-4-pentenoic
acid ((Z)-1aÁ
1H-NMR (CDCl3) d 0.12 (s, 6H), 2.17 (s, 2H), 2.34Á
2.39 (m, 4H), 6.28 (br s, 1H), 6.99Á7.09 (m, 3H), 7.17Á
/
1d)
3.1. Typical procedure for synthesis of vinylsilanes 1
/
/
/
A DMF (200 ml) solution of (Z)-5-benzyldimethylsi-
lyl-4-penten-1-ol (7.00 g, 30.0 mmol) was dropwise
added to a DMF (45 ml) solution of pyridinium
dichromate (PDC, 39.0 g, 105 mmol) at room tempera-
ture [11]. After being stirred for 20 h, the resultant
mixture was treated with water (100 ml) and extracted
with t-BuOMe (100 ml). The extract was washed with
7.26 (m, 2H) ppm. Anal. Calcd. for C14H19DO2Si: C,
67.42; H, 7.68; D, 0.81. Found: C, 67.67; H, 7.67; D,
0.80%.
3.1.5. (E)-5-Benzyldimethylsilyl-4-deuterio-4-pentenoic
acid ((E)-1aÁ
1H-NMR (CDCl3) d 0.02 (s, 6H), 2.10 (s, 2H), 2.36Á
2.47 (m, 4H), 5.95Á6.00 (m, 1H), 6.95Á7.09 (m, 3H),
7.16Á7.23 (m, 2H) ppm. Anal. Calcd. for C14H19DO2Si:
/
1d)
/
water (3ꢁ
/
50 ml). The aqueous layer was extracted with
50 ml). The combined organic layer was
/
/
t-BuOMe (2ꢁ
/
/

K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á
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247
C, 67.42; H, 7.68; D, 0.81. Found: C, 67.53; H, 7.75; D,
0.81%.
(CHꢁ2), 130.10 (CH), 138.17 (C), 140.00 (C), 145.68
(CH), 180.44 (C) ppm. Anal. Calcd. for C20H24O2Si: C,
74.03; H, 7.45. Found: C, 73.63; H, 7.65%.
/
3.1.6. (Z)-5-Benzyldimethylsilyl-2-hexyl-4-pentenoic
acid ((Z)-1b)
3.1.10. (Z)-5-Benzyldimethylsilyl-3-pentyl-4-pentenoic
acid ((Z)-1e)
b.p. 160 8C (bath temp., 0.4 Torr). IR (neat) 2927 (br),
1
1704 cmꢂ1; H-NMR (CDCl3) d 0.10 (s, 6H), 0.88 (t,
b.p. 156 8C (bath temp., 0.4 Torr). IR (neat) 2927 (br),
1
Jꢃ
(s, 2H), 2.16Á
6.27 (ddd, Jꢃ
7.17Á
7.23 (m, 2H) ppm; 13C-NMR (CDCl3) d ꢂ
(CH3ꢁ2), 14.04 (CH3), 22.57 (CH2), 26.58 (CH2), 27.24
(CH2), 29.14 (CH2), 31.62 (CH2), 31.71 (CH2), 35.70
(CH2), 45.63 (CH), 124.01 (CH), 128.10 (CHꢁ2),
128.20 (CHꢁ2), 129.45 (CH), 139.87 (C), 145.86
/
6.7 Hz, 3H), 1.27 (br s, 8H), 1.37Á
2.43 (m, 3H), 5.55 (d, Jꢃ
14.0, 7.4, 6.6 Hz, 1H), 6.99Á
/
1.68 (m, 2H), 2.15
14.0 Hz, 1H),
7.09 (m, 3H),
1.74
1709 cmꢂ1; H-NMR (CDCl3) d 0.11 (s, 6H), 0.87 (t,
/
/
Jꢃ
(dd, Jꢃ
1H), 2.59Á
(dd, Jꢃ14.0, 10.2 Hz, 1H), 6.99Á
7.23 (m, 2H) ppm; 13C-NMR (CDCl3) d ꢂ
/
6.7 Hz, 3H), 1.20Á
14.8, 7.2 Hz, 1H), 2.33 (dd, Jꢃ
2.73 (m, 1H), 5.50 (d, Jꢃ14.0 Hz, 1H), 6.05
7.09 (m, 3H), 7.17Á
1.68 (CH3ꢁ
/
1.45 (m, 8H), 2.15 (s, 2H), 2.21
/
/
/
/14.8, 6.8 Hz,
/
/
/
/
/
/
/
/
/
/
/
2), 14.01 (CH3), 22.51 (CH2), 26.68 (CH2), 26.84 (CH2),
31.90 (CH2), 34.87 (CH2), 39.89 (CH), 40.35 (CH2),
/
(CH), 182.44 (C) ppm. Anal. Calcd. for C20H32O2Si:
C, 72.23; H, 9.70. Found: C, 72.27; H, 9.41%.
123.98 (CH), 128.06 (CHꢁ
/
2), 128.13 (CH), 128.19
(CHꢁ2), 139.90 (C), 151.51 (CH), 179.28 (C) ppm.
/
Anal. Calcd. for C19H30O2Si: C, 71.65; H, 9.49. Found:
C, 71.78; H, 9.42%.
3.1.7. (Z)-5-Benzyldimethylsilyl-2-isopropyl-4-
pentenoic acid ((Z)-1c)
b.p. 162 8C (bath temp., 0.4 Torr). IR (neat) 2962 (br),
3.1.11. (Z)-5-Benzyldimethylsilyl-3-phenyl-4-pentenoic
acid ((Z)-1f)
1
1704 cmꢂ1; H-NMR (CDCl3) d 0.11 (s, 6H), 0.95 (d,
Jꢃ
including 2.15 (s, 2H), 5.53 (d, Jꢃ
(dt, Jꢃ14.2, 7.2 Hz, 1H), 6.99Á7.09 (m, 3H), 7.17Á
(m, 2H) ppm; 13C-NMR (CDCl3) d ꢂ
1.79 (CH3ꢁ
20.01 (CH3), 20.28 (CH3), 26.59 (CH2), 30.22 (CH),
33.06 (CH2), 52.58 (CH), 123.98 (CH), 128.09 (CHꢁ2),
128.20 (CHꢁ2), 129.15 (CH), 139.88 (C), 146.17 (CH),
/
6.8 Hz, 6H), 1.81Á
/
1.95 (m, 1H), 2.11Á
14.2 Hz, 1H), 6.27
7.23
2),
/
2.38 (m, 5H)
b.p. 152 8C (bath temp., 0.4 Torr). IR (neat) 2956 (br),
1
/
1709 cmꢂ1; H-NMR (CDCl3) d 0.15 (s, 3H), 0.16 (s,
/
/
/
3H), 2.17 (s, 2H), 2.58 (dd, Jꢃ
(dd, Jꢃ15.3, 7.6 Hz, 1H), 3.97 (dt, Jꢃ
1H), 5.55 (d, Jꢃ14.0 Hz, 1H), 6.43 (dd, Jꢃ
Hz, 1H), 6.96Á7.08 (m, 3H), 7.16Á7.33 (m, 7H) ppm;
13C-NMR (CDCl3) d ꢂ
1.70 (CH3ꢁ2), 26.51 (CH2),
41.32 (CH2), 44.93 (CH), 124.03 (CH), 126.65 (CH),
126.99 (CHꢁ2), 128.11 (CHꢁ2), 128.19 (CHꢁ2),
128.35 (CH), 128.68 (CHꢁ2), 139.71 (C), 142.41 (C),
/
15.3, 7.4 Hz, 1H), 2.74
10.4, 7.4 Hz,
14.0, 10.4
/
/
/
/
/
/
/
/
/
/
/
/
181.67 (C) ppm; MS m/z (rel. intensity) 199 [Mꢀ Ã
/
PhCH2, 64], 75 [100]. Anal. Calcd. for C17H26O2Si: C,
70.29; H, 9.02. Found: C, 70.09; H, 8.99%.
/
/
/
/
149.59 (CH), 178.08 (C) ppm. Anal. Calcd. for
C20H24O2Si: C, 74.03; H, 7.45. Found: C, 73.88; H,
7.72%.
3.1.8. (E)-5-Benzyldimethylsilyl-2-isopropyl-4-pentenoic
acid ((E)-1c)
IR (neat) 2960 (br), 1707 cmꢂ1; 1H-NMR (CDCl3) d
0.01 (s, 6H), 0.967 (d, Jꢃ
Hz, 3H), 1.84Á1.97 (m, 1H), 2.09 (s, 2H), 2.22Á
3H), 5.68 (dt, Jꢃ18.6, 1.3 Hz, 1H), 5.95 (dt, Jꢃ
6.3 Hz, 1H), 6.96Á7.08 (m, 3H), 7.16Á7.22 (m, 2H) ppm;
13C-NMR (CDCl3) d ꢂ
3.43 (CH3), ꢂ3.39 (CH3),
20.07 (CH3), 20.14 (CH3), 26.04 (CH2), 29.97 (CH),
36.33 (CH2), 51.81 (CH), 123.89 (CH), 128.05 (CHꢁ2),
128.21 (CHꢁ2), 130.50 (CH), 139.98 (C), 144.76 (CH),
181.39 (C) ppm.
/
6.8 Hz, 3H), 0.973 (d, Jꢃ
2.42 (m,
18.6,
/
6.9
3.1.12. (E)-5-Benzyldimethylsilyl-3-phenyl-4-pentenoic
acid ((E)-1f)
/
/
/
/
IR (KBr) 2954 (br), 1701 cmꢂ1; 1H-NMR (CDCl3) d
/
/
0.02 (s, 6H), 2.09 (s, 2H), 2.71 (dd, Jꢃ
2.77 (dd, Jꢃ15.6, 7.7 Hz, 1H), 3.85 (td, Jꢃ
1H), 5.65 (dd, Jꢃ18.6, 1.5 Hz, 1H), 6.08 (dd, Jꢃ
6.3 Hz, 1H), 6.96Á
7.33 (m, 10H) ppm; 13C-NMR
(CDCl3) d 3.46 (CH3ꢁ2), 26.01 (CH2), 39.69
(CH2), 47.33 (CH), 123.93 (CH), 126.72 (CH), 127.63
(CHꢁ2), 128.03 (CHꢁ3), 128.19 (CHꢁ2), 128.57
(CHꢁ2), 139.78 (C), 141.92 (C), 148.36 (CH), 178.39
/
15.6, 7.6 Hz, 1H),
7.7, 6.2 Hz,
18.6,
/
/
/
/
/
/
/
/
/
ꢂ
/
/
/
/
/
3.1.9. (Z)-5-Benzyldimethylsilyl-2-phenyl-4-pentenoic
acid ((Z)-1d)
/
(C) ppm.
b.p. 190 8C (bath temp., 0.4 Torr). IR (neat) 2954 (br),
1
1707 cmꢂ1; H-NMR (C6D6) d 0.05 (s, 3H), 0.06 (s,
3.2. Typical procedure for cyclization of vinylsilanes 1
3H), 2.02 (s, 2H), 2.43Á
3.50 (t, Jꢃ7.6 Hz, 1H), 5.50 (d, Jꢃ
(dt, Jꢃ14.2, 7.2 Hz, 1H), 6.91Á
7.21 (m, 10H) ppm; 13C-
NMR (C6D6) d ꢂ1.69 (CH3ꢁ2), 26.66 (CH2), 37.21
(CH2), 52.05 (CH), 124.48 (CH), 127.76 (CH), 128.35
(CHꢁ2), 128.48 (CHꢁ2), 128.54 (CHꢁ2), 128.97
/
2.54 (m, 1H), 2.80Á
/
2.91 (m, 1H),
/
/14.2 Hz, 1H), 6.20
To a CHCl3 (2.5 ml) solution of (Z)-1a (124 mg, 0.500
mmol) was added TiCl4 (1 M in CH2Cl2, 25 ml, 25 mmol)
at room temperature. The mixture was stirred for 16 h.
The resultant mixture was treated with saturated aqu-
eous NaHCO3 (20 ml) and extracted with t-BuOMe
/
/
/
/
/
/
/

248
K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á250
/
(3ꢁ
/
10 ml). The extract was dried over Na2SO4 and
PhCH2, 91], 75 [100]. Anal. Calcd. for C20H32O2Si: C,
72.22; H, 9.70. Found: C, 72.33; H, 9.48%.
evaporated. Purification of the crude product by silica
gel column chromatography gave 5-benzyldimethylsilyl-
4-pentanolide (2a, 99.2 mg, 0.400 mmol) in 80% yield.
3.2.4. 5-Benzyldimethylsilyl-2-isopropyl-4-pentanolide
When TsOH×
/
H2O was used as the catalyst, it was
(2c, cis:transꢃ83:17)
/
quickly added to a solution of (Z)-1a under the atmo-
sphere and N2 was passed through the flask to displace
the air.
b.p. 140 8C (bath temp., 0.4 Torr). IR (neat) 1766,
1
1171 cmꢂ1; H-NMR (CDCl3) d 0.07 (s, 3H), 0.09 (s,
3H), 0.88Á
and 1.01 (d, Jꢃ
0.17H), 1.22 (dd, Jꢃ
12.5, 10.2 Hz, 0.83H), 1.80 (ddd, Jꢃ
0.17H), 2.09Á2.23 (m, 4H) including 2.15 (s), 2.49Á
(m, 1H), 4.40 (dddd, Jꢃ10.4, 7.6, 6.9, 5.4 Hz, 0.83H),
4.55 (qd, Jꢃ7.6, 5.6 Hz, 0.17H), 6.98Á7.11 (m, 3H),
7.19Á
7.25 (m, 2H) ppm; 13C-NMR (CDCl3) for the
major isomer d ꢂ2.84 (CH3), ꢂ2.81 (CH3), 18.16
/
1.03 (m, 7H) including 0.89 (d, Jꢃ
6.8 Hz), 1.16 (dd, Jꢃ14.5, 7.6 Hz,
14.5, 3.3 Hz, 0.83H), 1.52 (td, Jꢃ
13.0, 9.7, 5.6 Hz,
2.59
/
6.8 Hz)
/
/
/
/
3.2.1. 5-Benzyldimethylsilyl-4-pentanolide (2a)
b.p. 142 8C (bath temp., 0.4 Torr). IR (neat) 1768,
/
1
1171 cmꢂ1; H-NMR (CDCl3) d 0.07 (s, 3H), 0.09 (s,
/
/
/
3H), 0.96 (dd, Jꢃ
7.2 Hz, 1H), 1.69Á
(m, 1H), 2.46Á2.59 (m, 2H), 4.53Á
7.11 (m, 3H), 7.19Á
7.25 (m, 2H) ppm; 13C-NMR
(CDCl3) d 2.98 (CH3ꢁ2), 22.68 (CH2), 25.69
(CH2), 29.28 (CH2), 31.20 (CH2), 79.70 (CH), 124.11
(CH), 127.95 (CHꢁ2), 128.15 (CHꢁ2), 139.22 (C),
/
14.5, 7.6 Hz, 1H), 1.22 (dd, Jꢃ
1.84 (m, 1H), 2.16 (s, 2H), 2.23Á
4.64 (m, 1H), 6.98Á
/
14.5,
/
/
/
/2.36
/
/
/
/
/
/
/
(CH3), 20.65 (CH3), 22.66 (CH2), 25.85 (CH2), 27.25
(CH), 33.59 (CH2), 47.66 (CH), 77.08 (CH), 124.19
ꢂ
/
/
(CH), 128.06 (CHꢁ
/
2), 128.23 (CHꢁ
/
2), 139.34 (C),
/
/
176.93 (C) ppm; MS m/z (rel. intensity) 157 [Mꢀ Ã
PhCH2, 57], 75 [100]. Anal. Calcd. for C14H20O2Si: C,
67.69; H, 8.12. Found: C, 67.69; H, 7.96%.
/
177.81 (C) ppm, for the minor isomer d ꢂ
/
2.90 (CH3),
18.67 (CH3), 20.48 (CH3), 23.27 (CH2), 28.54 (CH),
32.62 (CH2), 45.70 (CH), 77.41 (CH), 178.34 (C) ppm;
MS m/z (rel. intensity) 275 [Mꢀ Ã
PhCH2, 66], 75 [100]. Anal. Calcd. for C17H26O2Si: C,
/
CH3, 1.4], 199 [Mꢀ Ã
/
3.2.2. 5-Benzyldimethylsilyl-5-deuterio-4-pentanolide (4
for the (4R*, 5S*)-isomer and 5 for the (4R*, 5R*)-
70.31; H, 9.02. Found: C, 70.18; H, 8.94%.
isomer, 4:5ꢃ
1H-NMR (CDCl3) d 0.07 (s, 3H), 0.09 (s, 3H), 0.94
(dt, Jꢃ7.6, 2.0 Hz, 0.6H), 1.20 (br d, Jꢃ7.1 Hz, 0.4H),
1.69Á1.84 (m, 1H), 2.15 (s, 2H), 2.23Á2.36 (m, 1H),
2.45Á2.59 (m, 2H), 4.54Á4.62 (m, 1H), 6.98Á7.11 (m,
3H), 7.19Á7.25 (m, 2H) ppm. Anal. Calcd. for
/
3:2)
3.2.5. 5-Benzyldimethylsilyl-2-phenyl-4-pentanolide (2d,
cis:transꢃ71:29)
/
/
/
b.p. 180 8C (bath temp., 0.4 Torr). IR (neat) 1768,
1161 cmꢂ1; 1H-NMR (CDCl3) d 0.09 (s, 2.1H), 0.10 (s,
/
/
/
/
/
0.9H), 0.11 (s, 3H), 1.00 (dd, Jꢃ
1.05 (dd, Jꢃ14.3, 7.7 Hz, 0.71H), 1.27 (dd, Jꢃ
Hz, 0.71H), 1.32 (dd, Jꢃ14.3, 6.9 Hz, 0.29H), 1.96 (td,
Jꢃ
13.0, 9.2, 6.1 Hz, 0.29H), 2.48 (dt, Jꢃ
0.29H), 2.71 (ddd, Jꢃ
(dd, Jꢃ12.7, 8.4 Hz, 0.71H), 3.89 (dd, Jꢃ
0.29H), 4.57 (dddd, Jꢃ10.4, 7.6, 6.9, 5.1 Hz, 0.71H),
4.73 (quint, Jꢃ6.7 Hz, 0.29H), 6.99Á7.40 (m, 10H)
ppm; 13C-NMR (CDCl3) for the major isomer d ꢂ
2.75
(CH3ꢁ2), 22.63 (CH2), 25.89 (CH2), 41.46 (CH2), 47.98
(CH), 77.47 (CH), 124.31 (CH), 127.54 (CH), 128.10
(CHꢁ4), 128.34 (CHꢁ2), 128.81 (CHꢁ2), 136.53 (C),
139.29 (C), 176.61 (C) ppm, for the minor isomer d ꢂ
/14.3, 7.4 Hz, 0.29H),
/
/
/14.3, 7.1
C14H19DO2Si: C, 67.42; H, 7.68; D, 0.81. Found: C,
67.55; H, 7.69, D, 0.80%. The relative configurations of
4 and 5 were determined by stereo-defined desilylation
/
/
12.7, 10.4 Hz, 0.71H), 2.18 (s, 2H), 2.26 (ddd, Jꢃ
/
/13.0, 6.6 Hz,
1
OEt2 [12] followed by H-NMR analysis of
with BF3×
/
/12.7, 8.4, 5.1 Hz, 0.71H), 3.84
the resultant deuterated alkene 3.
/
/
9.2, 6.4 Hz,
/
3.2.3. 5-Benzyldimethylsilyl-2-hexyl-4-pentanolide (2b,
/
/
cis:transꢃ/78:22)
/
b.p. 150 8C (bath temp., 0.09 Torr). IR (neat) 1768,
/
1
1165 cmꢂ1; H-NMR (CDCl3) d 0.07 (s, 3H), 0.08 (s,
3H), 0.86Á
(m, 1.22H), 2.15 (s, 2H), 2.38 (ddd, Jꢃ
0.78H), 2.48Á2.63 (m, 1H), 4.42 (dddd, Jꢃ
6.9, 5.3 Hz, 0.78H), 4.59 (qd, Jꢃ7.1, 5.8 Hz, 0.22H),
6.98Á7.11 (m, 3H), 7.18Á
7.25 (m, 2H) ppm; 13C-NMR
(CDCl3) for the major isomer d ꢂ2.86 (CH3ꢁ2), 13.96
/
0.99 (m, 4H), 1.12Á
/
1.47 (m, 11H), 1.74Á
12.2, 8.4, 5.1 Hz,
10.2, 7.7,
/
2.07
/
/
/
/
/
/
/
2.81 (CH3), 22.75 (CH2), 39.43 (CH2), 45.97 (CH), 77.68
/
(CH), 137.04 (C), 139.31 (C), 176.92 (C) ppm; MS m/z
(rel. intensity) 233 [Mꢀ Ã
/
/
/
PhCH2, 31], 73 [100]. Anal.
/
/
Calcd. for C20H24O2Si: C, 74.03; H, 7.45. Found: C,
74.16; H, 7.51%.
(CH3), 22.47 (CH2), 22.68 (CH2), 25.81 (CH2), 27.23
(CH2), 28.93 (CH2), 30.11 (CH2), 31.51 (CH2), 38.39
(CH2), 41.58 (CH), 77.45 (CH), 124.16 (CH), 128.01
3.2.6. trans-5-Benzyldimethylsilyl-3-pentyl-4-pentanolide
(2e)
(CHꢁ
/
2), 128.20 (CHꢁ/2), 139.29 (C), 178.73 (C) ppm,
for the minor isomer d ꢂ
/
2.94 (CH3ꢁ2), 22.80 (CH2),
/
b.p. 150 8C (bath temp., 0.09 Torr). IR (neat) 1776,
1
25.78 (CH2), 28.90 (CH2), 30.56 (CH2), 36.52 (CH2),
39.57 (CH), 77.28 (CH), 139.32 (C), 179.14 (C) ppm; MS
m/z (rel. intensity) 317 [Mꢀ Ã
1205 cmꢂ1; H-NMR (CDCl3) d 0.07 (s, 3H), 0.09 (s,
3H), 0.87Á
/
0.96 (m, 4H), 1.00 (dd, Jꢃ/14.8, 4.8 Hz, 1H),
/
CH3, 1.3], 241 [Mꢀ Ã
/
1.27 (br s, 8H), 1.94Á
/
2.10 (m, 1H), 2.16 (dd, Jꢃ
/17.1,

K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á
/250
249
9.2 Hz, 1H), 2.17 (s, 2H), 2.65 (dd, Jꢃ
4.16 (ddd, Jꢃ9.7, 6.9, 4.8 Hz, 1H), 6.99Á
7.19Á
7.24 (m, 2H) ppm; 13C-NMR (CDCl3) d ꢂ
(CH3), ꢂ2.73 (CH3), 13.94 (CH3), 21.24 (CH2), 22.41
(CH2), 25.86 (CH2), 27.26 (CH2), 31.68 (CH2), 32.42
(CH2), 35.17 (CH2), 45.08 (CH), 84.45 (CH), 124.10
/
17.1, 8.1 Hz, 1H),
7.10 (m, 3H),
2.97
3.3. Typical procedure for synthesis of tetrahydrofurans 6
To a solution of lactone 2b (cis:transꢃ76:24, 250 mg,
0.75 mmol) in Et2O (2.5 ml) was added DIBALH (0.95
M in hexane, 2.0 ml, 1.9 mmol) at 0 8C. The mixture was
warmed to room temperature over 3 h. The resultant
mixture was cooled to 0 8C and aqueous potassium
sodium tartrate (20%, 10 ml) was added slowly. The
resultant precipitate was dissolved with a small amount
of 2 M aqueous NaOH. The mixture was extracted with
/
/
/
/
/
/
(CH), 128.10 (CHꢁ
/
2), 128.20 (CHꢁ2), 139.61 (C),
/
176.44 (C) ppm; MS m/z (rel. intensity) 227 [Mꢀ Ã
PhCH2, 38], 73 [100]. Anal. Calcd. for C19H30O2Si: C,
71.65; H, 9.49. Found: C, 71.66; H, 9.38%.
/
AcOEt (3ꢁ10 ml). The extract was washed with
/
saturated aqueous NH4Cl, dried over Na2SO4 and
evaporated. The crude product was directly used for
further transformation. To a solution of the crude
product in THF (1.5 ml) was added BuLi (1.73 M in
3.2.7. 5-Benzyldimethylsilyl-3-pentyl-4-pentanolide (2e,
trans:cisꢃ
1H-NMR (CDCl3) d 0.07 (s, 3H), 0.09 (s, 3H), 0.73
(dd, Jꢃ14.4, 4.2 Hz, 0.13H), 0.87Á0.96 (m, 4H), 1.00
(dd, Jꢃ14.8, 4.8 Hz, 0.87H), 1.27 (br s, 8H), 1.94Á2.10
(m, 0.87H), 2.16 (dd, Jꢃ17.1, 9.2 Hz, 0.87H), 2.17 (s,
2H), 2.25 (dd, Jꢃ16.1, 7.1 Hz, 0.13H), 2.32Á2.46 (m,
0.13H), 2.53 (dd, Jꢃ16.1, 7.4 Hz, 0.13H), 2.65 (dd, Jꢃ
17.1, 8.1 Hz, 0.87H), 4.16 (ddd, Jꢃ9.7, 6.9, 4.8 Hz,
0.87H), 4.66 (ddd, Jꢃ11.4, 6.1, 4.3 Hz, 0.13H), 6.99Á
7.10 (m, 3H), 7.19Á
7.24 (m, 2H) ppm; 13C-NMR
(CDCl3) for the minor isomer (see above for the signals
of the major isomer) d ꢂ3.07 (CH3), ꢂ2.82 (CH3),
/87:13)
/
/
hexane, 0.48 ml, 0.83 mmol) at ꢂ78 8C. After 30 min, a
/
/
/
THF (2.5 ml) solution of TsCl (160 mg, 0.84 mmol) was
added. The mixture was warmed to room temperature
/
/
/
over 3 h, and then cooled to ꢂ78 8C again. BuLi (1.73
/
/
/
M in hexane, 0.48 ml, 0.83 mmol) was added to the
cooled mixture. The mixture was warmed to room
temperature over 2 h, poured into saturated aqueous
/
/
/
/
NH4Cl and extracted with t-BuOMe (3ꢁ10 ml). The
/
extract was dried over Na2SO4 and evaporated. Pur-
ification by silica gel column chromatography gave
/
/
15.56 (CH2), 25.80 (CH2), 27.13 (CH2), 28.43 (CH2),
31.76 (CH2), 34.00 (CH2), 39.98 (CH), 81.84 (CH),
176.60 (C) ppm.
tetrahydrofuran 6b (cis:transꢃ
/
73:27, 204 mg, 0.64
mmol) in 85% yield.
3.3.1. 2-Benzyldimethylsilylmethyl-4-
hexyltetrahydrofuran (6b, cis:transꢃ
1H-NMR (CDCl3) d 0.00 (s, 3H), 0.01 (s, 2.2H), 0.02
(s, 0.8H), 0.76Á1.15 (m, 6H), 1.27 (br s, 10H), 1.53Á1.66
(m, 0.54H), 2.05Á2.26 (m, 3.46H) including 2.11 (s), 3.23
(dd, Jꢃ8.4, 7.6 Hz, 0.27H), 3.42 (dd, Jꢃ8.1, 7.4 Hz,
0.73H), 3.82 (t, Jꢃ7.9 Hz, 0.73H), 3.87Á4.02 (m,
1.27H), 6.98Á7.09 (m, 3H), 7.17Á7.24 (m, 2H) ppm;
13C-NMR (CDCl3) for the major isomer d ꢂ
2.95
(CH3), ꢂ2.82 (CH3), 14.03 (CH3), 22.58 (CH2), 22.74
3.2.8. trans-5-Benzyldimethylsilyl-3-phenyl-4-
pentanolide (2f)
/
73:27)
m.p. 86Á
1H-NMR (CDCl3) d 0.03 (s, 3H), 0.04 (s, 3H), 1.01 (d,
Jꢃ7.1 Hz, 2H), 2.12 (s, 2H), 2.73 (dd, Jꢃ17.5, 10.7 Hz,
1H), 2.93 (dd, Jꢃ17.5, 8.4 Hz, 1H), 3.21 (dt, Jꢃ10.6,
8.3 Hz, 1H), 4.53 (dt, Jꢃ7.9, 7.1 Hz, 1H), 6.87Á7.41 (m,
10H) ppm; 13C-NMR (CDCl3) d ꢂ
2.97 (CH3), ꢂ2.86
(CH3), 20.74 (CH2), 25.75 (CH2), 37.40 (CH2), 51.56
(CH), 85.54 (CH), 124.12 (CH), 127.26 (CHꢁ2), 127.78
(CH), 128.11 (CHꢁ2), 128.24 (CHꢁ2), 129.12 (CHꢁ
2), 138.56 (C), 139.51 (C), 175.47 (C) ppm; MS m/z (rel.
PhCH2, 12], 73 [100]. Anal. Calcd.
/
88 8C (Et2O). IR (KBr) 1774, 1223 cmꢂ1
;
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
(CH2), 26.10 (CH2), 28.48 (CH2), 29.38 (CH2), 31.75
(CH2), 34.09 (CH2), 40.45 (CH), 41.89 (CH2),
/
/
/
72.49 (CH2), 77.59 (CH), 123.88 (CH), 128.09 (CHꢁ
/
intensity) 233 [Mꢀ Ã
/
4), 140.00 (C) ppm, for the minor isomer d ꢂ2.91
/
for C20H24O2Si: C, 74.03; H, 7.45. Found: C, 74.08; H,
7.47%.
(CH3), 22.96 (CH2), 28.37 (CH2), 33.74 (CH2), 39.14
(CH), 40.65 (CH2), 73.01 (CH2), 76.39 (CH), 140.06 (C)
ppm.
3.2.9. 5-Benzyldimethylsilyl-3-phenyl-4-pentanolide (2f,
trans:cisꢃ
1H-NMR (CDCl3) d
2.46H), 0.04 (s, 2.46H), 0.15 (s, 0.54H), 0.40 (dd, Jꢃ
14.8, 3.6 Hz, 0.18H), 0.60 (dd, Jꢃ14.8, 11.5 Hz, 0.18H),
1.01 (d, Jꢃ7.1 Hz, 1.64H), 2.09 (s, 0.36), 2.12 (s,
1.64H), 2.73 (dd, Jꢃ17.5, 10.7 Hz, 0.82H), 2.77 (dd,
Jꢃ17.5, 6.0 Hz, 0.18H), 2.93 (dd, Jꢃ17.5, 8.4 Hz, 1H),
3.21 (dt, Jꢃ10.6, 8.3 Hz, 0.82H), 3.68 (dt, Jꢃ8.1, 6.1
Hz, 0.18H), 4.53 (dt, Jꢃ7.9, 7.1 Hz, 0.82H), 4.87 (ddd,
Jꢃ11.5, 6.3, 3.6 Hz, 0.18H), 6.87Á7.41 (m, 10H) ppm.
/
82:18)
3.3.2. 2-Benzyldimethylsilylmethyl-4-
ꢂ
/
0.01 (s, 0.54H), 0.03 (s,
isopropyltetrahydrofuran (6c, cis:transꢃ
1H-NMR (CDCl3) d 0.01 (s, 3H), 0.02 (s, 3H), 0.76Á
0.92 (m, 7.19H), 0.99Á1.14 (m, 1.81H), 1.39Á1.72 (m,
1H), 1.86Á2.13 (m, 4H) including 2.11 (s), 3.27 (t, Jꢃ
8.7 Hz, 0.19H), 3.50 (t, Jꢃ8.1 Hz, 0.81H), 3.83 (t, Jꢃ
8.1 Hz, 0.81H), 3.89Á4.01 (m, 1.19H), 6.98Á7.09 (m,
3H), 7.17Á
7.23 (m, 2H) ppm; 13C-NMR (CDCl3) for the
major isomer d ꢂ2.94 (CH3), ꢂ2.83 (CH3), 21.35
(CH3), 21.45 (CH3), 22.55 (CH2), 26.09 (CH2), 32.25
/
81:19)
/
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250
K. Miura et al. / Journal of Organometallic Chemistry 686 (2003) 242Á250
/
(b) K. Miura, T. Takahashi, H. Nishikori, A. Hosomi, Chem.
Lett. (2001) 958.;
(CH), 40.24 (CH2), 48.06 (CH), 71.15 (CH2), 77.83
(CH), 123.88 (CH), 128.06 (CHꢁ4), 139.97 (C) ppm,
/
(c) K. Miura, T. Hondo, T. Nakagawa, T. Takahashi, A. Hosomi,
Org. Lett. 2 (2000) 385;
for the minor isomer d 21.21 (CH3), 21.54 (CH3), 23.11
(CH2), 31.70 (CH), 38.75 (CH2), 46.58 (CH), 71.71
(CH2), 76.90 (CH) ppm.
(d) K. Miura, T. Hondo, T. Takahashi, A. Hosomi, Tetrahedron
Lett. 41 (2000) 2129.
[4] (a) K. Miura, T. Hondo, S. Okajima, T. Nakagawa, T.
Takahashi, A. Hosomi, J. Org. Chem. 67 (2002) 6082;
(b) K. Miura, T. Takahashi, T. Hondo, A. Hosomi, Chirality 15
(2003) 41.
Acknowledgements
[5] M.F. Ansell, M.H. Palmer, Quart. Rev. 18 (1964) 211.
[6] (a) T. Fujita, S. Watanabe, K. Suga, T. Miura, K. Sugahara, H.
Kikuchi, J. Chem. Tech. Biotechnol. 32 (1982) 476;
(b) L. Jalander, M. Broms, Acta Chem. Scand. B 36 (1982) 371;
(c) M.D. Bachi, J.W. Epstein, Y.H.- Minzly, H.J.E. Loewenthal, J
Org Chem. 34 (1969) 126.
This work was partly supported by Grants-in-Aid for
Scientific Research from the Ministry of Education,
Culture, Sports, Science, and Technology, Government
of Japan. We thank Dow Corning Toray Silicone Co.
Ltd. and Shin-Etsu Chemical Co. Ltd. for a gift of
organosilicon compounds.
[7] K.E. Koenig, W.P. Weber, J. Am. Chem. Soc. 95 (1973) 3416
As mentioned by Koenig and Weber, simultaneously with
protonation to the double bond, rotation would occur about
the developing carbonÃ
permit the silyl group to continuously stabilize the incipient b-
silylcarbenium ion B by hyperconjugation of the SiÃC bond.
/
carbon single bond in the direction to
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