A new route to enol ethers

Article abstract of DOI:10.1055/s-2004-822367

Dithioorthoformates having various alkoxy groups were obtained by copper(H) bromide-promoted oxidative coupling of bis(phenylthio)methyltributylstannane with alcohols. The dithioorthoformates thus prepared are useful precursors for alkoxymethylidene compl

Full text of DOI:10.1055/s-2004-822367

PAPER
1457
A New Route to Enol Ethers
A
N
ew Route to
a
E
nol Ethe
k
rs eshi Takeda,* Kensaku Sato, Akira Tsubouchi
Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
Fax +81(42)3887034; E-mail: takeda-t@cc.tuat.ac.jp
Received 9 April 2004
Dedicated to Professor Teruaki Mukaiyama on the occasion of his 77th birthday
In this context, we recently developed an alkoxylmethyl
chloride–titanocene(II) system as an alternative method
for alkoxymethylidenation of carbonyl compounds.4
Although this new method enables us to prepare various
Abstract: Dithioorthoformates having various alkoxy groups were
obtained by copper(II) bromide-promoted oxidative coupling of
bis(phenylthio)methyltributylstannane
with
alcohols.
The
dithioorthoformates thus prepared are useful precursors for
alkoxymethylidene complexes of titanium, which transform carbo- 1-alkoxy-1-alkenes, preparation of starting alkoxymethyl
nyl compounds into a variety of enol ethers. Even the alkoxymeth-
chlorides from acid labile alcohols is difficult and the re-
ylidene complexes having a terminal olefin moiety can be prepared
action requires essentially more than two equivalents of
and employed for carbonyl olefination without formation of ring-
alkoxymethyl chloride.
closing metathesis product.
Then we turned our attention to the preparation of
Key words: carbene complexes, esters, ketones, olefination, titani-
dithioorthoformates 2 from various alcohols under mild
reaction conditions and their application to carbonyl ole-
fination. Preparation of dithioorthoformates is generally
performed by the reaction of alkyl dichloroalkyl ethers5
with alkali metal thiolates. However this procedure cannot
be applied for synthesis of dithioorthoformates bearing an
acid labile alkoxy group. Although several other methods
for the preparation of dithioorthoformates have been de-
veloped, they all need use of a large excess amount of al-
cohol and multi-step procedures, hence they are of limited
synthetic utility.6 Previously we found that the oxidative
coupling of allyl and vinylstannanes with nucleophiles
such as alcohols, acetates, amines, enol silyl ethers, and
allylsilanes proceeded in the presence of copper(II) salts.7
These results prompted us to investigate the copper(II)
salt-promoted oxidative coupling of readily available
bis(phenylthio)methyltributylstannane 7 and alcohols 8
(Scheme 2). Here we describe a versatile method for the
preparation of dithioorthoformates 2 from alcohols and
their application to alkoxymethylidenation of carbonyl
compounds leading to the formation of a variety of enol
ethers.
um
Considerable effort has been made to develop efficient
methods for preparation of enol ethers because of their
usefulness as synthetic intermediates. While carbonyl ole-
finations utilizing a-phosphorous1 and a-silyl2 carbanions
bearing a a-alkoxy group are considered as major ap-
proaches to the enol ethers, these reactions cannot be em-
ployed for the transformation of carboxylic acid
derivatives such as esters and lactones. We have eliminat-
ed this difficulty by means of the alkoxymethylidene com-
plex of titanium 1 generated by the desulfurization of
methoxybis(phenylthio)methane 2 (R1 = Me) with ti-
tanocene(II) reagent Cp2Ti[P(OEt)3]2 3 (Scheme 1).3 This
procedure provides a convenient way for the preparation
of 1,2-diheteroatom-substituted olefins 4 from carboxylic
acid derivatives 5 via the oxatitanacyclobutane intermedi-
ates 6. A serious drawback remained in this procedure; it
is difficult to introduce a variety of alkoxy groups to the
olefinating agents due to lack of easy access to
dithioorthoformates 2.
SPh
SPh
SPh
9 / CuBr2 / LiBr
O
R2
Y
Bu3Sn
SPh
RO
SPh
Cp2Ti[P(OEt)3]2
3
5
2
7
R1O
R1O
SPh
TiCp2
Y = H, R3, OR3, SR3
BuLi
1
2
ROH
ROLi
8
9
R2
Cp2Ti
R1O
O
Scheme 2
R2
R1O
- Cp2Ti=O
Y
Y
6
4
Initially the transformation of benzyl alcohol 8a to the
corresponding dithioorthoformate 2a with bis(phenyl-
thio)methylstannane 7 was investigated under various
conditions. When lithium benzyloxide 9a prepared in situ
from 8a and n-butyllithium was treated with bis(phenyl-
thio)methylstannane 7 at –40 ºC in the presence of CuBr2,
the dithioorthoformate 2a was produced in 30% yield
Scheme 1
SYNTHESIS 2004, No. 9, pp 1457–1465
Advanced online publication: 10.05.2004
DOI: 10.1055/s-2004-822367; Art ID: C01604SS
© Georg Thieme Verlag Stuttgart · New York
x
x
.
x
x
.2
0
0
4

1458
T. Takeda et al.
PAPER
along with a considerable amount of tris(phenyl- formation is applicable to the unsaturated alcohols and
thio)methane. An improved yield (71%) of the product 2a acid labile alcohols such as 2-(trimethylsilyl)ethanol. The
was obtained when LiBr was used as an additive. In this secondary alcohols such as cyclopentanol 8k also reacted
reaction, neither inorganic base such as K2CO3 nor Et3N with 7 to give the corresponding dithioorthoformates 2k
was suitable as a base giving poor yield of 2a. Under op- though the yields were unsatisfactory (entry 11).
timized conditions, the reactions of a variety of alcohols 8
with 7 were preformed and the corresponding dithioortho-
formates 2 were obtained in good yields (Table 1). It is
noteworthy, from a synthetic point of view, that this trans-
via formation of a certain trivalent arylcopper species.8
Barton et al. suggested that copper(II) salt promoted oxi-
dative coupling reactions of triarylbismuths and triaryl-
bismuth diacetates with heteroatom nucleophiles proceed
Table 1 Preparation of Dithioorthoformates 2 from Alcohols 8 by Copper(II) Bromide-Promoted Reaction with Bis(phenylthio)methylstan-
nane 7a
Entry
1
Alcohol 8
Dithioorthoformate 2
Yield (%)
71
PhS
HO
Ph
PhS
O
Ph
8a
8b
2a
PhS
PhS
Ph
2
3
58
65
Ph
Ph
HO
O
2b
PhS
PhS
HO
O
8c
2c
Ph
PhS
PhS
4
5
73
73
HO
O
8d
2d
PhS
HO
Ph
PhS
O
Ph
8e
2e
PhS
HO
PhS
O
6
51
Ph
Ph
8f
2f
PhS
PhS
HO-(CH2)8CH=CH(CH2)7CH3
7
8
9
67
74
78
O(CH2)8CH=CH(CH2)7CH3
8g
2g
PhS
PhS
O
O
HO
O
8h
2h
PhS
PhS
SiMe3
HO
SiMe3
O
8i
2i
2j
PhS
PhS
HO
O
10
11
76
49
O
O
8j
PhS
HO
PhS
O
8k
2k
a All the reactions were performed with a procedure similar to that described in the text.
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

PAPER
A New Route to Enol Ethers
1459
Recently copper(II) salt-promoted cross-couplings of alkenes in good yields (Table 3). The E-isomers were al-
arylboronic acids9 with heteroatom nucleophiles were in- most always predominant in these reactions. The observed
vestigated, and these reactions are believed to follow a selectivity agrees well with that of the alkoxymethylide-
similar reaction pathway. We also assume that the forma- nation of the carboxylic acid derivatives using organotita-
tion of dithioorthoformates 2 is explained by the reaction nium species generated from alkoxymethyl chlorides and
path involving the formation of organocopper(III) inter- the titanocene(II) reagent4 suggesting that the reaction
mediate depicted in Scheme 3. First the alkoxycopper(II) proceeds via an oxatitanacyclobutane intermediate 6 in
bromide 10 is produced by the reaction of lithium alkox- which dipole-dipole repulsion between an alkoxy substit-
ide 9 with copper(II) bromide. The transmetallation be- uent (R1O) and a polar substituent (Y) is minimized.
tween bis(phenylthio)methyltributylstannane 7 and 10
affords the bis(phenylthio)methylcopper(II) species 11.
The dithioorthoformate 2 is formed by one-electron oxi-
dation of 11 and subsequent reductive elimination of the
What is striking is the fact that no ring-closing metathesis
proceeded when the dithioorthoformates bearing a termi-
nal olefin moiety were employed and the resulting ti-
tanocene alkoxymethylidenes react with carbonyl
trivalent organocopper species 12.
compounds to form enol ethers.16 We found that a variety
Despite the above arguments, however, an alternative of unsaturated carbo and heterocyclic compounds were
pathway for the present reaction, in which a cation radical obtained by the treatment of thioacetals possessing a ter-
intermediate is formed by the oxidation of 7 with cop- minal double bond with the titanocene(II) species.17
per(II) salt should not be excluded. Mizuno et al. de- Therefore the difference of reactivity towards carbon-car-
scribed an oxidative coupling of benzylsatnnanes with bon double bond between alkylidene and alkoxymeth-
alcohols in which a cation radical species is formed by the ylidene complexes is of great interest because this finding
oxidation of benzylstannanes with copper(II) salt under ir- indicates that the reactivity of titanium carbene complexes
radiation.10 Narasaka and his co-workers reported similar is largely affected by the electronic property of a-hetero-
oxidative couplings of 2-tributylstannyl-1,3-dithianes atom substituent.
with olefinic nucleophiles using ammonium hexanitrato-
In conclusion, we have established a versatile method for
cerate(IV) or ferrocenium hexafluorophosphate and they
the preparation of dithioorthoformates from various alco-
suggested that the active intermediate of this reaction is
hols including ones possessing an acid labile group. These
1,3-dithian-2-yl cation.11 The related formation of acetals
dithioorthoformates are useful for the preparation of a va-
by electrochemical oxidation of alkoxymethylstannanes
riety of heteroatom-substituted olefins. Further study on
in the presence of alcohols was also reported.12 As for ac-
the elucidation of reactivity of heteroatom-substituted ti-
celeration of the reaction with lithium bromide, we tenta-
tanium carbene complexes and their application to organ-
tively assume that it is attributable to increase in solubility
ic synthesis is now in progress.
of CuBr2 through the formation of a certain cuprate13 or
generation of a highly coordinated organotin species from
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded
the stannylthioacetal 7 which facilitates its oxidation with
using TMS as internal standard. Chemical shifts (d) are quoted in
CuBr2.14
ppm from TMS for 1H NMR and CDCl3 for 13C NMR spectra. IR
absorptions are reported in cm–1. All reactions were performed un-
der argon atmosphere in dried glassware. THF was distilled from
Na and benzophenone. Preparative thin layer chromatography
(PTLC) was carried out using Wakogel B-5F.
Reaction of Benzyl Alcohol (8a) with Bis(phenylthio)methyl-
tributylstannane (7); General Procedure
Lithium bromide (174 mg, 2.00 mmol) was placed in a flask and
dried by heating with a heat gun under reduced pressure (2-3 mm-
Hg). After cooling, a THF (4 mL) solution of 8a (108 mg, 1.00
mmol) was added under argon. A hexane (1.47 M, 0.68 mL) solu-
tion of n-BuLi (1.0 mmol) was added at 0 °C, and the mixture was
stirred for 15 min. Copper(II) bromide (491 mg, 2.20 mmol) and a
Scheme 3
THF (4 mL) solution of 7 (521 mg, 1.00 mmol) were successively
added with an interval of 15 min to the reaction mixture which was
cooled to –40 °C. After stirring for 2 h at –40 °C, the reaction was
quenched by addition of 3.5% aq NH3 solution. The organic mate-
rials were extracted with Et2O and dried over K2CO3. The solvent
was removed under reduced pressure and the residue was purified
by silica gel PTLC (hexane) to yield benzyloxybis(phenyl-
thio)methane (2a) (241 mg, 71%). In a similar manner, the
Next the carbonyl olefination utilizing these dithioortho-
formates 2 was investigated. The dithioorthoformates 2
were treated with the titanocene(II) reagent 3 (4.5 equiv)
for 10 minutes and then with ketones 5a–d to afford the
corresponding enol ethers in good yields (Table 2). As is
the case with other carbonyl olefination procedures using
the Schrock-type transition metal carbene complexes,15 dithioorthoformates 2b–k were also obtained.
the present alkoxymethylidenation could be applied to
carboxylic acid derivatives such as esters, lactones, thiol-
esters, and amides to afford the diheteroatom-substituted
Benzyloxybis(phenylthio)methane (2a)
IR (neat): 3063, 3030, 2955, 2854, 1594, 1455, 1376, 1079, 1045,
1024, 741, 696, 672 cm–1.
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

1460
T. Takeda et al.
PAPER
Table 2 Titanocene(II)-Promoted Alkoxymethylidenation of Ketones 5 Using Dithioorthoformates 2a
Entry
1
Dithioorthoformate 2
Carbonyl compound 5
Product 4
Yield (%) (E:Z)b
Ph
O
O
Ph
2a
56
55 (74:26)
58
Ph
5a
4a
O
Ph
Ph
O
2
3
2a
2b
Ph
4b
5b
Ph
Ph
5a
O
Ph
Ph
4c
O
Ph
4
5
2b
2d
70
63
O
Ph
Ph
5c
4d
Ph
O
O
5d
5a
4e
CH3(CH2)7CH=CH(CH2)8O
6
7
2g
2f
56
54
Ph
4f
O
Ph
O
5c
Ph
4g
a All the reactions were performed with a procedure similar to that described in the text.
b Determined by NMR analysis.
1H NMR (CDCl3): d = 4.85 (s, 2 H), 6.26 (s, 1 H), 7.08–7.11 (m, 2
H), 7.23–7.33 (m, 9 H), 7.49–7.53 (m, 4 H).
13C NMR (CDCl3): d = 22.5, 37.1, 64.2, 93.4, 111.8, 127.9, 128.9,
132.4, 133.8, 142.2.
13C NMR (CDCl3): d = 67.8, 92.5, 127.9, 128.0, 128.26, 128.34,
129.0, 132.6, 133.4, 136.4.
Anal. Calcd for C18H20OS2: C, 68.31; H, 6.37. Found: C, 68.65; H,
6.41.
Anal. Calcd for C20H18OS2: C, 70.97; H, 5.36. Found: C, 70.80; H,
5.47.
4-Bis(phenylthio)methoxy-2-phenethylbut-1-ene (2d)
IR (neat): 3060, 3025, 2937, 1646, 1582, 1479, 1439, 1156, 1052,
1025, 895, 741 cm–1.
1H NMR (CDCl3): d = 2.25 (t, J = 7.7 Hz, 2 H), 2.28 (t, J = 6.2 Hz,
2 H), 2.68 (dd, J = 7.1, 9.3 Hz, 2 H), 3.91 (t, J = 6.9 Hz, 2 H), 4.74
(s, 1 H), 4.78 (s, 1 H), 6.23 (s, 1 H), 7.12–7.35 (m, 11 H), 7.47–7.52
(m, 4 H).
1-Bis(phenylthio)methoxy-4-phenylbutane (2b)
IR (neat): 3060, 3025, 2938, 2862, 1582, 1479, 1439, 1385, 1065,
1025, 740, 689 cm–1.
1H NMR (CDCl3): d = 1.55–1.58 (m, 4 H), 2.54 (t, J = 7.1 Hz, 2 H),
3.79 (t, J = 5.8 Hz, 2 H), 6.18 (s, 1 H), 7.09–7.14 (m, 2 H), 7.17–
7.32 (m, 9 H), 7.46–7.50 (m, 4 H).
13C NMR (CDCl3): d = 34.1, 35.6, 37.9, 64.3, 93.4, 111.2, 125.8,
127.9, 128.27, 128.29, 128.9, 132.3, 133.8, 141.9, 145.5.
13C NMR (CDCl3): d = 27.8, 28.6, 35.4, 65.9, 93.3, 125.7, 127.9,
128.2, 128.4, 128.9, 132.4, 133.8, 142.2.
Anal. Calcd for C25H26OS2: C, 73.85; H, 6.45. Found: C, 73.66; H,
6.54.
Anal. Calcd for C23H24OS2: C, 72.59; H, 6.36. Found: C, 72.75; H,
6.42.
3-[Bis(phenylthio)methoxy]methyl-6-phenylhex-1-ene (2e)
IR (neat): 3060, 3025, 2932, 2858, 1582, 1496, 1479, 1453, 1382,
1303, 1059, 1025, 916, 741, 690 cm–1.
1H NMR (CDCl3): d = 1.18–1.27 (m, 1 H), 1.34–1.61 (m, 3 H),
2.19–2.27 (m, 1 H), 2.45–2.53 (m, 2 H), 3.70 (d, J = 6.1 Hz, 2 H),
4.958 (d, J = 15.8 Hz, 1 H), 4.964 (d, J = 11.6 Hz, 1 H), 5.44–5.56
(m, 1 H), 6.22 (s, 1 H), 7.10–7.33 (m, 11 H), 7.47–7.53 (m, 4 H).
4-Bis(phenylthio)methoxy-2-methylbut-1-ene (2c)
IR (neat): 3074, 2937, 2879, 1650, 1582, 1478, 1439, 1375, 1303,
1157, 1056, 1024, 891, 615 cm–1.
1H NMR (CDCl3): d = 1.66 (s, 3 H), 2.23 (t, J = 6.8 Hz, 2 H), 3.90
(t, J = 6.8 Hz, 2 H), 4.66 (s, 1 H), 4.73 (s, 1 H), 6.22 (s, 1 H), 7.25–
7.34 (m, 6 H), 7.49–7.52 (m, 4 H).
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

PAPER
A New Route to Enol Ethers
1461
Table 3 Titanocene(II)-Promoted Alkoxymethylidenation of Carboxylic Acid Derivatives 5 Using Dithioorthoformates 2a
Entry
1
Dithioorthoformate 2
Carbonyl compound 5
Product 4
Yield (%) (E:Z)b
OEt
Ph
O
Ph
O
2a
57 (47:53)c
74 (56:44)c
Ph
OEt
5e
5e
4h
Ph
Ph
OEt
Ph
O
2
3
2b
2b
4i
SiPr
O
O
85 (82:18)
51 (61:39)
52 (62:38)d
SiPr
5f
4j
O
OEt
Ph
O
4
5
2c
2c
Ph
OEt
5g
4k
4l
O
O
O
Ph
Ph
O
5h
5g
Ph
OEt
Ph
6
2d
80 (62:38)
O
4m
Me3Si
Me3Si
OEt
O
7
8
2i
2i
5g
62 (58:42)
81 (83:17)
Ph
4n
SEt
Ph
O
O
Ph
Ph
SEt
Ph
5h
4o
O
Me3Si
Ph
Ph
O
9
2i
64e
N
N
Me
Me
4p
5i
a All the reactions were performed with a procedure similar to that described in the text.
b Based on the isolated yields.
c Determined by NMR analysis.
d Ratio of the stereoisomers.
e Obtained as a single stereoisomer. The configuration was not determined.
13C NMR (CDCl3): d = 28.8, 30.8, 35.9, 43.4, 69.0, 93.3, 115.9,
125.6, 127.80, 127.83, 128.2, 128.3, 128.9, 132.3, 132.4, 132.7,
133.71, 133.74, 139.5, 142.5.
J = 9.2, 18.3 Hz, 1 H), 4.58 (s, 1 H), 4.65 (s, 1 H), 6.17 (s, 1 H),
6.99–7.01 (m, 2 H), 7.15–7.33 (m, 9 H), 7.46–7.51 (m, 4 H).
13C NMR (CDCl3): d = 22.3, 28.6, 34.9, 37.7, 39.6, 67.9, 93.6,
110.0, 125.8, 127.8, 127.9, 128.1, 128.3, 128.91, 128.93, 129.2,
132.4, 132.6, 133.7, 135.3, 140.5, 145.6.
Anal. Calcd for C26H28OS2: C, 74.24; H, 6.71. Found: C, 74.21; H,
6.57.
Anal. Calcd for C27H30OS2: C, 74.61; H, 6.96. Found: C, 74.38; H,
7.00.
5-Benzyl-6-bis(phenylthio)methoxy-2-methylhex-1-ene (2f)
IR (neat): 3060, 3025, 2930, 1648, 1582, 1495, 1479, 1452, 1439,
1374, 1056, 1025, 887, 739 cm–1.
1H NMR (CDCl3): d = 1.33–1.44 (m, 2 H), 1.59 (s, 3 H), 1.74–1.80
(m, 1 H), 1.92–1.98 (m, 2 H), 2.48 (dd, J = 6.3, 13.2 Hz, 1 H), 2.55
(dd, J = 7.2, 13.2 Hz, 1 H), 3.63 (dd, J = 9.4, 18.2 Hz, 1 H), 3.65 (dd,
1-[Bis(phenylthio)methoxy]octadec-9-ene (2g)
IR (neat): 3060, 3004, 2925, 2853, 1583, 1479, 1466, 1439, 1378,
1303, 1156, 1065, 1025, 967, 737, 689 cm–1.
1H NMR (CDCl3): d = 0.88 (t, J = 6.5 Hz, 3 H), 1.17–1.40 (m, 22
H), 1.45–1.58 (m, 2 H), 1.90–2.00 (m, 4 H), 3.76 (t, J = 6.4 Hz, 2
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

1462
T. Takeda et al.
PAPER
H), 5.30–5.41 (m, 2 H), 6.18 (s, 1 H), 7.26–7.33 (m, 4 H), 7.49–7.52
(m, 6 H).
13C NMR (CDCl3): d = 14.1, 22.7, 26.1, 27.2, 29.1, 29.2, 29.27,
29.31, 29.4, 29.5, 29.8, 31.9, 66.2, 93.3, 127.8, 128.9, 129.8, 123.0,
132.4, 133.9.
and the reaction mixture was stirred for 3 h. A THF (1 mL) solution
of 2a (152 mg, 0.45 mmol) was added to the mixture and stirring
was continued for 10 min at the same temperature. A THF (1 mL)
solution of 5a (52 mg, 0.30 mmol) was added dropwise over 10 min
and the reaction mixture was refluxed for 3 h. After cooling to r.t.,
the reaction was quenched by addition of 1 M NaOH. Insoluble ma-
terials were filtered off through Celite and washed with Et2O. The
layers were separated, and the aqueous layer was extracted with
Et2O. The combined organic extracts were dried over K2CO3 and
the solvent was removed under reduced pressure. The residue was
purified by PTLC (hexane–EtOAc, 95:5) to afford 1-benzyloxyme-
thylidene-4-phenylcyclohexane (4a) (47 mg, 56%). In a similar
manner, the enol ethers 4b–p were also obtained.
Anal. Calcd for C31H46OS2: C, 74.64; H, 9.29. Found: C, 74.45; H,
9.08.
2-[Bis(phenylthio)methoxy]methyloxolane (2h)
IR (neat): 3058, 2946, 1582, 1479, 1439, 1304, 1057, 1025, 1000,
919, 740, 710, 690 cm–1.
1H NMR (CDCl3): d = 1.47–1.57 (m, 1 H), 1.76–1.92 (m, 3 H),
3.67–3.85 (m, 4 H), 3.98 (tt, J = 6.0, 6.0 Hz, 1 H), 6.29 (s, 1 H),
7.25–7.34 (m, 6 H), 7.50–7.55 (m, 4 H).
1-Benzyloxymethylidene-4-phenylcyclohexane (4a)
IR (neat): 3083, 3028, 2923, 2854, 1686, 1602, 1494, 1453, 1444,
13C NMR (CDCl3): d = 25.5, 28.1, 67.7, 68.2, 77.0, 93.3, 127.8,
127.9, 128.9, 132.2, 132.5, 133.7.
1360, 1205, 1181, 1133, 1077, 1064, 1027, 752, 698 cm–1.
1H NMR (CDCl3): d = 1.28–1.50 (m, 2 H), 1.75–2.18 (m, 5 H), 2.62
(tt, J = 3.3, 12.2 Hz, 1 H), 3.00 (d, J = 13.6 Hz, 1 H), 4.76 (s, 2 H),
5.95 (t, J = 1.7 Hz, 1 H), 7.17–7.39 (m, 10 H).
Anal. Calcd for C18H20OS2: C, 65.02; H, 6.06. Found: C, 64.92; H,
5.94.
13C NMR (CDCl3): d = 25.5, 30.4, 34.3, 35.6, 44.7, 73.5, 118.2,
1-Bis(phenylthio)methoxy-2-(trimethylsilyl)ethane (2i)
IR (neat): 3060, 2952, 2896, 1582, 1479, 1439, 1376, 1249, 1177,
1059, 1087, 1025, 938, 836, 739, 690 cm–1.
1H NMR (CDCl3): d = 0.00 (s, 9 H), 0.83–0.89 (m, 2 H), 3.84–3.90
(m, 2 H), 6.18 (s, 1 H), 7.27–7.36 (m, 6 H), 7.51–7.54 (m, 4 H).
125.9, 126.8, 127.4, 127.7, 128.3, 128.4, 137.5, 137.9, 147.2.
Anal. Calcd for C20H22O: C, 86.29; H, 7.96. Found: C, 86.40; H,
8.04.
Benzyl 2-Phenylprop-1-enyl Ether (4b)
IR (neat): 3056, 3031, 2928, 2865, 1651, 1599, 1496, 1454, 1444,
1374, 1282, 1264, 1206, 1161, 1072, 1028, 909, 845, 758, 736, 696
cm–1.
1H NMR (CDCl3): d = 1.90–1.91 (m, 0.78 H), 2.04–2.05 (m, 2.22
H), 4.89 (s, 0.52 H), 4.92 (s, 1.48 H), 6.25 (br q, J = 1.3 Hz, 0.26 H),
6.56 (br q, J = 1.3 Hz, 0.74 H,), 7.14–7.68 (m, 10 H).
13C NMR (CDCl3): d = 12.8, 18.4, 74.0, 74.3, 111.3, 115.2, 125.0,
125.9, 126.0, 127.2, 127.3, 127.5, 127.84, 127.88, 127.91, 128.3,
128.50, 128.52, 137.5, 137.6, 140.6, 142.9, 143.5.
13C NMR (CDCl3): d = –1.5, 17.6, 64.0, 93.1, 127.8, 128.9, 132.4,
133.9.
Anal. Calcd for C18H24OSiS2: C, 62.02; H, 6.94. Found: C, 62.23;
H, 6.80.
1-[3-[Bis(phenylthio)methoxy]propyl]-2-(2-methylprop-2-enyl-
oxy)benzene (2j)
IR (neat): 3074, 3060, 2938, 2870, 1657, 1600, 1584, 1492, 1479,
1451, 1438, 1376, 1301, 1239, 1192, 1120, 1054, 1024, 903, 751
cm–1.
1H NMR (CDCl3): d = 1.81 (s, 3 H), 1.81–1.90 (m, 2 H), 2.61 (t,
J = 7.7 Hz, 2 H), 3.80 (t, J = 6.4 Hz, 2 H), 4.40 (s, 2 H), 4.95 (s, 1
H), 5.08 (s, 1 H), 6.17 (s, 1 H), 6.78–6.85 (m, 2 H), 6.97 (dd, J = 1.7,
7.3 Hz, 1 H), 7.13 (dt, J = 1.8, 7.8 Hz, 1 H), 7.24–7.34 (m, 6 H),
7.47–7.54 (m, 4 H).
13C NMR (CDCl3): d = 19.5, 27.2, 29.1, 66.1, 71.4, 93.4, 111.3,
112.1, 120.4, 127.0, 127.9, 128.9, 130.0, 130.2, 132.5, 133.8, 141.0,
156.5.
Anal. Calcd for C16H16O: C, 85.68; H, 7.19. Found: C, 85.72; H,
7.16.
4-Phenyl-1-[(4-phenylbutoxy)methylidene]cyclohexane (4c)
IR (neat): 3026, 2923, 2858, 1686, 1603, 1494, 1452, 1443, 1204,
1188, 1142, 1082, 1064, 840, 749, 699 cm–1.
1H NMR (CDCl3): d = 1.37–1.51 (m, 2 H), 1.63–1.83 (m, 5 H),
1.91–2.18 (m, 4 H), 2.55–2.67 (m, 3 H), 2.93 (d, J = 11.9 Hz, 1 H),
3.69 (t, J = 7.0 Hz, 2 H), 5.83 (s, 1 H), 7.14–7.20 (m, 6 H), 7.25–
7.30 (m, 4 H).
Anal. Calcd for C26H28O2S2: C, 71.52; H, 6.46. Found: C, 71.40; H,
6.56.
13C NMR (CDCl3): d = 25.4, 27.7, 29.3, 30.5, 34.4, 35.6, 35.7, 44.8,
71.6, 117.1, 125.7, 125.9, 126.8, 128.3, 128.4, 137.9, 142.3, 147.2.
[Bis(phenylthio)methoxy]cyclopentane (2k)
IR (neat): 3059, 2960, 2745, 1582, 1477, 1439, 1362, 1319, 1302,
Anal. Calcd for C23H28O: C, 86.20; H, 8.81. Found: C, 85.85; H,
9.07.
1172, 1051, 1025, 968, 743, 710, 690 cm–1.
1H NMR (CDCl3): d = 1.37–1.65 (m, 8 H), 4.41–4.45 (m, 1 H), 5.91
(d, J = 1.3 Hz, 1 H), 7.21–7.33 (m, 6 H), 7.47–7.56 (m, 4 H).
13C NMR (CDCl3): d = 23.3, 32.2, 79.9, 92.2, 128.0, 128.7, 133.3.
2-Phenethyl-4-phenylbut-1-enyl 4-Phenylbutyl Ether (4d)
IR (neat): 3084, 3062, 3026, 2935, 2858, 1674, 1602, 1496, 1453,
1179, 1133, 1076, 1030, 843, 746, 698 cm–1.
Anal. Calcd for C18H20OS2: C, 68.31; H, 6.37. Found: C, 68.72; H,
6.63.
1H NMR (CDCl3): d = 1.52–1.73 (m, 4 H), 2.17 (t, J = 7.8 Hz, 2 H),
2.42 (t, J = 8.1 Hz, 2 H), 2.60–2.74 (m, 6 H), 3.60 (t, J = 6.1 Hz, 2
H), 5.78(s, 1 H), 7.13–7.29 (m, 15 H).
13C NMR (CDCl3): d = 27.7, 29.2, 29.3, 33.9, 34.2, 35.1, 35.6, 71.6,
116.9, 125.6, 125.69, 125.72, 128.15, 128.22, 128.3, 128.37,
128.40, 141.8, 142.27, 142.31, 142.7.
Olefination of 4-Phenylcyclohexanone (5a) with 2a; General
Procedure
Finely powdered molecular sieves 4A (135 mg), magnesium turn-
ings (39 mg, 1.6 mmol) and Cp2TiCl2 (336 mg, 1.35 mmol) were
placed in a flask and dried by heating with a heat gun under reduced
pressure. After cooling, THF (3 mL) and P(OEt)3 (0.46 mL, 2.7
mmol) were added successively with stirring at 25 °C under argon,
Anal. Calcd for C28H32O: C, 87.45; H, 8.39. Found: C, 87.50; H,
8.26.
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

PAPER
A New Route to Enol Ethers
1463
2-Ethylbut-1-enyl 3-Phenethylbut-3-enyl Ether (4e)
IR (neat): 3064, 3027, 2963, 1677, 1644, 1496, 1455, 1372, 1269,
1160, 1079, 893, 839, 745, 698 cm–1.
1H NMR (CDCl3): d = 0.95 (t, J = 7.1 Hz, 3 H), 0.97 (t, J = 6.5 Hz,
3 H), 1.92 (dq, J = 7.5, 1.2 Hz, 2 H), 2.08 (q, J = 7.6 Hz, 2 H), 2.33–
2.39 (m, 4 H), 2.76 (dd, J = 7.0, 9.4 Hz, 2 H), 3.77 (t, J = 7.1 Hz, 2
H), 4.81 (s, 1 H), 4.84 (s, 1 H), 5.77 (s, 1 H), 7.15–7.20 (m, 3 H),
7.24–7.30 (m, 2 H).
J = 6.2 Hz, 0.88 H), 3.55–3.64 (m, 2 H), 3.98 (q, J = 7.0 Hz, 1.12
H), 5.34 (s, 0.44 H), 5.69 (s, 0.56 H), 7.15–7.29 (m, 10 H).
13C NMR (CDCl3): d = 14.9, 15.7, 27.6, 27.8, 29.1, 29.2, 29.8, 32.8,
33.3, 34.0, 35.5, 35.6, 63.2, 65.6, 72.3, 72.5, 125.60, 125.69,
125.72, 126.3, 128.1, 128.2, 128.3, 128.37, 128.44, 128.5, 129.3,
137.7, 141.9, 142.1, 142.26, 142.32, 146.5.
Anal. Calcd for C22H28O2: C, 81.44; H, 8.70. Found: C, 81.28; H,
8.60.
13C NMR (CDCl3): d = 12.6, 13.2, 20.1, 24.3, 34.3, 36.3, 38.2, 70.5,
111.1, 122.3, 125.8, 128.29, 128.32, 139.3, 142.0, 145.8.
(E)-2-(Isopropylthio)hex-1-enyl 4-Phenylbutyl Ether (E-4j)
IR (neat): 3027, 2955, 2861, 1631, 1496, 1454, 1379, 1363, 1238,
1134, 1048, 862, 747, 699 cm–1.
1H NMR (CDCl3): d = 0.90 (t, J = 7.2 Hz, 3 H), 1.18 (d, J = 6.6 Hz,
6 H), 1.23–1.36 (m, 2 H), 1.42–1.52 (m, 2 H), 1.60–1.76 (m, 4 H),
2.22 (t, J = 7.5 Hz, 2 H), 2.64 (t, J = 7.2 Hz, 2 H), 2.92 (sep, J = 6.7
Hz, 1 H), 3.79 (t, J = 6.1 Hz, 2 H), 6.38 (s, 1 H), 7.16–7.20 (m, 3 H),
7.25–7.30 (m, 2 H).
Anal. Calcd for C18H26O: C, 83.67; H, 10.14. Found: C, 83.50; H,
10.33.
1-[Octadec-9-enyloxymethylidene]-4-phenylcyclohexane (4f)
IR (neat): 3026, 3003, 2924, 2853, 1687, 1639, 1602, 1493, 1456,
1369, 1204, 1186, 1142, 839, 754 cm–1.
1H NMR (CDCl3): d = 0.88 (t, J = 6.8 Hz, 3 H), 1.25–2.20 (m, 35
H), 2.62 (tt, J = 12.2, 3.2 Hz, 1 H), 2.93 (d, J = 13.8 Hz, 1 H), 3.68
(t, J = 6.7 Hz, 2 H), 5.35 (t, J = 4.7 Hz, 2 H), 5.85 (s, 1 H), 7.15–
7.33 (m, 5 H).
13C NMR (CDCl3): d = 14.1, 22.7, 25.4, 25.9, 27.2, 29.2, 29.3, 29.4,
29.47, 29.52, 29.71, 29.74, 29.8, 30.5, 31.9, 34.4, 35.5, 35.7, 44.8,
71.9, 116.9, 125.9, 126.80, 126.85, 128.3, 129.8, 129.9, 131.1,
138.0, 147.3.
13C NMR (CDCl3): d = 14.0, 22.3, 22.8, 27.6, 29.2, 29.3, 30.0, 35.3,
35.5, 72.3, 111.5, 125.8, 128.3, 128.4, 142.1, 150.7.
Anal. Calcd for C19H30OS: C, 74.45; H, 9.87. Found: C, 74.74; H,
10.00.
(Z)-2-(Isopropylthio)hex-1-enyl 4-Phenylbutyl Ether (Z-4j)
IR (neat): 3026, 2956, 2927, 2861, 1639, 1496, 1453, 1380, 1363,
1154, 1051, 746, 698 cm–1.
1H NMR (CDCl3): d = 0.90 (t, J = 7.2 Hz, 3 H), 1.19–1.34 (m, 2 H),
1.22 (d, J = 6.6 Hz, 6 H), 1.41–1.50 (m, 2 H), 1.63–1.74 (m, 4 H),
2.03 (t, J = 7.3 Hz, 2 H), 2.64 (t, J = 7.1 Hz, 2 H), 3.32 (sep, J = 6.6
Hz, 1 H), 3.81 (t, J = 6.1 Hz, 2 H), 6.27 (s, 1 H), 7.20–7.16 (m, 3 H),
7.25–7.30 (m, 2 H).
Anal. Calcd for C31H50O: C, 84.87; H, 11.49. Found: C, 84.69; H,
11.21.
2-[(2-Phenethy-4-phenylbut-1-enyl)oxymethyl]oxolane (4g)
IR (neat): 3025, 2925, 2859, 1674, 1603, 1496, 1454, 1277, 1175,
1156, 1127, 1076, 1030, 746, 699 cm–1.
1H NMR (CDCl3): d = 1.63–1.73 (m, 1 H), 1.82–1.96 (m, 3 H), 2.18
(t, J = 8.0 Hz, 2 H), 2.40–2.51 (m, 2 H), 2.60–2.81 (m, 4 H), 3.56–
3.66 (m, 2 H), 3.72–3.88 (m, 2 H), 3.97–4.05 (m, 1 H), 5.86 (s, 1 H),
7.14–7.30 (m, 10 H).
13C NMR (CDCl3): d = 26.1, 28.2, 29.5, 34.1, 34.4, 35.3, 68.7, 74.3,
77.8, 117.3, 125.9, 126.0, 128.4, 128.5, 128.66, 128.72, 142.4,
142.6, 142.9.
13C NMR (CDCl3): d = 13.9, 22.1, 23.1, 27.5, 29.3, 30.8, 33.6, 34.6,
35.5, 72.4, 109.6, 125.7, 128.3, 128.4, 142.1, 146.7.
(E)-2-Ethoxy-3-phenylprop-1-enyl 3-Methylbut-3-enyl Ether
(E-4k)
IR (neat): 3063, 3029, 2978, 2903, 1650, 1603, 1495, 1454, 1392,
1245, 1139, 1056, 891, 778, 733, 699 cm–1.
1H NMR (CDCl3): d = 1.20 (t, J = 7.0 Hz, 3 H), 1.76 (s, 3 H), 2.34
(t, J = 6.9 Hz, 2 H), 3.53 (s, 2 H), 3.59 (q, J = 6.9 Hz, 2 H), 3.73 (t,
J = 6.9 Hz, 2 H), 4.75 (br s, 1 H), 4.80 (br s, 1 H), 5.84 (s, 1 H), 7.15–
7.30 (m, 5 H).
13C NMR (CDCl3): d = 14.9, 22.7, 34.4, 37.7, 63.6, 71.2, 111.8,
125.8, 126.8, 128.1, 128.6, 139.5, 142.4, 146.0.
Anal. Calcd for C23H28O2: C, 82.39; H, 8.39. Found: C, 81.98; H,
8.66.
Benzyl 2-Ethoxy-4-phenylbut-1-enyl Ether (4h)
IR (neat): 3028, 2977, 2927, 2866, 1686, 1604, 1496, 1454, 1382,
1170, 1131, 1077, 1056, 746, 698 cm–1.
1H NMR (CDCl3): d = 1.26 (t, J = 7.0 Hz, 1.59 H), 1.27 (t, J = 7.0
Hz, 1.41 H), 2.18 (t, J = 7.7 Hz, 1.06 H), 2.54 (t, J = 7.8 Hz, 0.94
H), 2.71–2.76 (m, 2 H), 3.57 (q, J = 7.4 Hz, 0.94 H), 4.00 (q, J = 7.0
Hz, 1.06 H), 4.44 (s, 0.94 H), 4.68 (s, 1.06 H), 5.44 (s, 0.53 H), 5.77
(s, 0.47 H), 7.14–7.36 (m, 10 H).
13C NMR (CDCl3): d = 14.9, 15.7, 29.9, 32.7, 33.2, 33.9, 63.1, 65.7,
74.0, 74.6, 125.6, 125.71, 125.74, 127.4, 127.71, 127.74, 128.1,
128.2, 128.33, 128.37, 128.44, 128.56, 128.63, 137.6, 137.7, 138.4,
141.8, 142.2, 147.2.
(Z)-2-Ethoxy-3-phenylprop-1-enyl 3-Methylbut-3-enyl Ether
(Z-4k)
IR (neat): 3063, 3028, 2975, 2928, 1687, 1650, 1603, 1495, 1454,
1369, 1343, 1199, 1137, 1052, 891, 701 cm–1.
1H NMR (CDCl3): d = 1.12 (t, J = 7.1 Hz, 3 H), 1.75 (s, 3 H), 2.35
(t, J = 6.9 Hz, 2 H), 3.23 (s, 2 H), 3.78 (t, J = 7.1 Hz, 2 H), 3.87 (q,
J = 7.0 Hz, 2 H), 4.73 (br s, 1 H), 4.78 (br s, 1 H), 5.47 (s, 1 H), 7.17–
7.31 (m, 5 H).
13C NMR (CDCl3): d = 15.5, 22.7, 37.2, 37.7, 65.9, 71.1, 111.9,
126.2, 128.2, 128.7, 130.0, 138.1, 139.0, 142.2.
Anal. Calcd for C19H22O2: C, 80.82; H, 7.85. Found: C, 80.66; H,
8.14.
Anal. Calcd for C16H22O2: C, 78.01; H, 9.00. Found: C, 77.74; H,
9.33.
2-Ethoxy-4-phenylbut-1-enyl 4-Phenylbutyl Ether (4i)
IR (neat): 3061, 3026, 2975, 2935, 2862, 1687, 1604, 1496, 1454,
1232, 1175, 1136, 1077, 1056, 747, 699 cm–1.
1H NMR (CDCl3): d = 1.265, 1.273 (t, J = 7.1, 6.9 Hz, 3 H), 1.52–
1.71 (m, 4 H), 2.19 (dd, J = 7.5, 8.2 Hz, 0.88 H), 2.52 (dd, J = 6.7,
9.1 Hz, 1.12 H), 2.59–2.65 (m, 2 H), 2.72–2.80 (m, 2 H), 3.42 (t,
2-[(3-Methylbut-3-enyl)oxymethylidene]-5-phenyloxolane (4l,
Major Isomer)
IR (neat): 3068, 3031, 2938, 1650, 1496, 1453, 1375, 1200, 1136,
1028, 890, 756, 700 cm–1.
Synthesis 2004, No. 9, 1457–1465 © Thieme Stuttgart · New York

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T. Takeda et al.
PAPER
1H NMR (CDCl3): d = 1.77 (s, 3 H), 1.86–1.99 (m, 1 H), 2.33–2.43
(m, 1 H), 2.35 (t, J = 7.0 Hz, 2 H), 2.62–2.79 (m, 2 H), 3.74 (t, J =
6.9 Hz, 2 H), 4.75 (br s, 1 H), 4.80 (br s, 1 H), 5.15 (dd, J = 6.4, 7.9
Hz, 1 H), 6.17 (t, J = 2.1 Hz, 1 H), 7.27–7.37(m, 5 H).
13C NMR (CDCl3): d = 22.7, 25.4, 33.1, 37.6, 71.1, 82.6, 111.7,
123.4, 125.6, 127.7, 128.4, 142.5.
1H NMR (CDCl3): d = 0.00 (s, 9 H), 0.97–1.03 (m, 2 H), 1.10 (t,
J = 7.0 Hz, 3 H), 3.21 (s, 2 H), 3.70–3.75 (m, 2 H), 3.85 (q, J = 7.0
Hz, 2 H), 5.44 (s, 1 H), 7.15–7.28 (m, 5 H).
13C NMR (CDCl3): d = –1.2, 15.7, 18.7, 37.3, 66.0, 70.3, 126.4,
128.5, 129.0, 130.3, 137.9, 139.3.
(E)-2-Ethylthio-3-phenylprop-1-enyl 2-(Trimethylsilyl)ethyl
Ether (E-4o)
Anal. Calcd for C16H20O2: C, 78.65; H, 8.25. Found: C, 78.33; H,
8.30.
IR (neat): 3085, 3028, 2954, 1631, 1495, 1453, 1420, 1383, 1305,
1250, 1226, 1148, 1082, 1030, 838, 764, 719, 698, 627 cm–1.
2-[(3-Methylbut-3-enyl)oxymethylidene]-5-phenyloxolane (4l,
Minor Isomer)
1H NMR (CDCl3): d = 0.00 (s, 9 H), 0.97–1.03 (m, 2 H), 1.05 (t,
J = 7.3 Hz, 3 H), 2.30 (q, J = 7.3 Hz, 2 H), 3.54 (s, 2 H), 3.88–3.93
(m, 2 H), 6.49 (s, 1 H), 7.09–7.24 (m, 5 H).
IR (neat): 3070, 3030, 2937, 1650, 1452, 1342, 1181, 1136, 1078,
1027, 943, 890, 754, 700 cm–1.
1H NMR (CDCl3): d = 1.77 (s, 3 H), 1.91–2.00 (m, 1 H), 2.33–2.44
(m, 1 H), 2.41 (t, J = 7.3 Hz, 2 H), 2.54–2.60 (m, 2 H), 3.84 (t, J =
7.3 Hz, 2 H), 4.75 (s, 1 H), 4.79 (s, 1 H), 5.29 (t, J = 6.7 Hz, 1 H),
5.42 (t, J = 1.6 Hz, 1 H), 7.24–7.34 (m, 5 H).
13C NMR (CDCl3): d = 22.9, 25.9, 33.7, 37.7, 71.2, 83.2, 111.7,
119.9, 125.6, 127.5, 128.3, 140.8.
13C NMR (CDCl3): d = –1.4, 14.4, 18.6, 27.0, 35.4, 70.4, 109.4,
125.9, 128.1, 128.8, 140.2, 150.5.
Anal. Calcd for C16H26OSSi: C, 65.25; H, 8.90. Found: C, 65.48; H,
8.94.
(Z)-2-Ethylthio-3-phenylprop-1-enyl 2-(Trimethylsilyl)ethyl
Ether (Z-4o)
(E)-2-Ethoxy-3-phenylprop-1-enyl 3-Phenethylbut-3-enyl
Ether (E-4m)
IR (neat): 3027, 2954, 2925, 1638, 1495, 1453, 1382, 1250, 1147,
1031, 970, 938, 838, 757, 698 cm–1.
IR (neat): 3083, 3062, 3026, 2978, 2928, 1645, 1602, 1496, 1454,
1H NMR (CDCl3): d = 0.04 (s, 9 H), 1.04–1.10 (m, 2 H), 1.13 (t,
J = 7.3 Hz, 3 H), 2.60 (q, J = 7.4 Hz, 2 H), 3.41 (s, 2 H), 3.89–3.95
(m, 2 H), 6.34 (s, 1 H), 7.18–7.32 (m, 5 H).
13C NMR (CDCl3): d = –1.5, 14.7, 18.6, 25.7, 39.6, 70.4, 126.2,
128.2, 128.7, 147.1.
1246, 1139, 1055, 894, 744, 698 cm–1.
1H NMR (CDCl3): d = 1.20 (t, J = 7.0 Hz, 3 H), 2.34 (t, J = 8.2 Hz,
2 H), 2.38 (t, J = 7.0 Hz, 2 H), 2.75 (t, J = 8.1 Hz, 2 H), 3.53 (s, 2
H), 3.59 (q, J = 7.0 Hz, 2 H), 3.74 (t, J = 6.9 Hz, 2 H), 4.83 (br s, 1
H), 4.85 (br s, 1 H), 5.83 (s, 1 H), 7.15–7.30 (m, 10 H).
13C NMR (CDCl3): d = 14.8, 34.3, 34.4, 36.2, 38.1, 63.5, 71.4,
111.2, 125.81, 125.82, 126.8, 128.1, 128.3, 128.6, 139.5, 142.0,
145.7, 146.0.
2-(N-Methyl-N-phenylamino)-2-phenylethenyl 2-(Trimethylsi-
lyl)ethyl Ether (4p)
IR (neat): 3059, 3026, 2952, 2894, 2816, 1645, 1599, 1501, 1445,
1363, 1322, 1250, 1227, 1147, 1051, 1031, 955, 859, 837, 764, 748,
692 cm–1.
1H NMR (CDCl3): d = 0.00 (s, 9 H), 0.98–1.04 (m, 2 H), 3.17 (s, 3
H), 3.94–4.00 (m, 2 H), 6.58 (s, 1 H), 6.64–6.74 (m, 3 H), 7.13–7.31
(m, 7 H).
Anal. Calcd for C23H28O2: C, 82.10; H, 8.39. Found: C, 82.44; H,
8.51.
(Z)-2-Ethoxy-3-phenylprop-1-enyl 3-Phenethylbut-3-enyl
Ether (Z-4m)
IR (neat): 3062, 3027, 2977, 2927, 1687, 1645, 1603, 1496, 1454,
13C NMR (CDCl3): d = –1.5, 18.7, 38.0, 70.8, 112.7, 116.3, 124.7,
1368, 1343, 1198, 1138, 1052, 894, 747, 700 cm–1.
125.4, 126.4, 128.5, 128.7, 137.1, 142.3, 148.0.
1H NMR (CDCl3): d = 1.11 (t, J = 7.1 Hz, 3 H), 2.34 (t, J = 8.5 Hz,
2 H), 2.40 (t, J = 7.3 Hz, 2 H), 2.75 (t, J = 8.1 Hz, 2 H), 3.23 (s, 2
H), 3.79 (t, J = 7.1 Hz, 2 H), 3.86 (q, J = 7.0 Hz, 2 H), 4.81 (br s, 1
H), 4.84 (br s, 1 H), 5.46 (t, J = 0.83 Hz, 1 H), 7.15–7.31 (m, 10 H).
Anal. Calcd for C20H27ONSi: C, 73.79; H, 8.36, N, 4.30. Found: C,
73.87; H, 8.32, N, 4.03.
13C NMR (CDCl3): d = 15.5, 34.3, 36.2, 37.1, 38.1, 65.8, 71.2,
111.3, 125.8, 126.2, 128.2, 128.3, 128.7, 130.0, 138.1, 138.9, 141.9,
145.5.
Acknowledgment
This research was supported by a Grant-in-Aid for Scientific Re-
search (No. 14340228) and Grant-in-Aid for Scientific Research on
Priority Areas (A) ‘Exploitation of Multi-Element Cyclic Molecu-
les’ (No. 14044022) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan. This work was carried out
under the 21st Century COE program of ‘Future Nano-materials’ in
Tokyo University of Agriculture & Technology.
(E)-2-Ethoxy-3-phenylprop-1-enyl 2-(Trimethylsilyl)ethyl
Ether (E-4n)
IR (neat): 3029, 2978, 2953, 2896, 1603, 1495, 1454, 1250, 1136,
1113, 1056, 860, 837, 698 cm–1.
1H NMR (CDCl3): d = 0.00 (s, 9 H), 0.95–1.01 (m, 2 H), 1.18 (t,
J = 7.0 Hz, 3 H), 3.53 (s, 2 H), 3.57 (q, J = 7.0 Hz, 2 H), 3.68–3.71
(m, 2 H), 5.81 (s, 1 H), 7.11–7.29 (m, 5 H).
References
13C NMR (CDCl3): d = –1.1, 15.2, 18.6, 34.6, 63.8, 70.5, 126.1,
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(Z)-2-Ethoxy-3-phenylprop-1-enyl 2-(Trimethylsilyl)ethyl
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IR (neat): 3029, 2953, 2926, 2898, 1687, 1495, 1454, 1381, 1342,
1250, 1198, 1133, 1051, 860, 838, 701 cm–1.
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