Ring-closing metathesis of titanium - Carbene complexes prepared from thioacetals having a carbon - Carbon double bond

Article abstract of DOI:10.1016/S0040-4020(00)00201-5

The ring-closing metathesis proceeded to give cycloalkenes in good yields when diphenyl thioacetals having a carbon-carbon double bond were treated with the low-valent titanium species Cp₂Ti[P(OEt)₃]₂ in THF at room temperature and then at reflux. This methodology is successfully applied to the preparation of cyclic ethers and sulfides. (C) 2000 Published by Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00201-5

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 4859±4869
Ring-Closing Metathesis of Titanium±Carbene Complexes
Prepared from Thioacetals Having a Carbon±Carbon
Double Bond
*
Tooru Fujiwara, Yoshiko Kato and Takeshi Takeda
Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
Received 12 November 1999; accepted 2 February 2000
AbstractÐThe ring-closing metathesis proceeded to give cycloalkenes in good yields when diphenyl thioacetals having a carbon±carbon
double bond were treated with the low-valent titanium species Cp2Ti[P(OEt)3]2 in THF at room temperature and then at re¯ux. This
methodology is successfully applied to the preparation of cyclic ethers and sul®des. q 2000 Published by Elsevier Science Ltd.
Introduction
has a great drawback of lacking the general method for
the preparation of alkylidenetitanium species. Therefore
we expected that the desulfurization of thioacetals would
become a practical method for the preparation of such
species. Indeed, the organotitanium species thus formed
showed the reactivity characteristic of titanium±carbenes.
Their reactions with various carbonyl compounds including
carboxylic acid derivatives produced conjugated dienes in
good yields.4a Furthermore, we found that the treatment of
diphenyl thioacetals derived from saturated aldehydes with
4 produced the similar organotitanium species which
reacted with carbonyl compounds4 and alkynes5 to give
the corresponding ole®ns and conjugated dienes, respec-
tively. On the basis of these experimental results, we tenta-
tively propose that the active species formed from saturated
thioacetal is also a titanium±carbene complex 6.
In the course of study on the desulfurizative metallation of
organosulfur compounds,1 we found that vinylcyclo-
propanes 1 were produced by the desulfurization of
b,g-unsaturated thioacetals 2 or 1,3-bis(phenylthio)propene
derivatives 3 with the low-valent titanium species Cp2Ti-
[P(OEt)3]2 4 in the presence of terminal ole®ns. The newly
developed titanium reagent 4 is easily prepared by
the reduction of titanocene dichloride with magnesium in
the presence of triethyl phosphite and molecular sieves 4A
(Scheme 1).2
This ®nding initiated our work with carbene chemistry; the
experimental results described above indicate that vinyl-
carbene complexes 5 would be produced by the reduction
of thioacetals 2 or their congeners 3 with titanocene(II)
species 4. The preparation and reactions of titanium±
carbene complexes have been extensively studied since
the discovery of Tebbe reagent.3 However this chemistry
In contrast to the vinylcarbene complex 5, the reaction of 6
with a simple terminal alkene gave a multi-component
mixture of unsaturated hydrocarbons. It is assumed that
Scheme 1.
Keywords: thioacetal; titanium and compounds; metathesis; cyclization.
* Corresponding author. Tel: 181-42-388-7034; fax: 181-42-388-7034; e-mail: takeda-t@cc.tuat.ac.jp
0040±4020/00/$ - see front matter q 2000 Published by Elsevier Science Ltd.
PII: S0040-4020(00)00201-5

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T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
Scheme 2.
this complexity would arise from lack of regioselectivity in
the formation of titanacyclobutane intermediates 7, which
may decompose to form new carbene complexes and ole®ns
by metathesis-type process (Scheme 2). We then examined
the in¯uence of substituents of ole®n on the geometry of the
intermediate titanacycle 7 and found that g-substituted allyl-
silanes were stereoselectively obtained when allyltrialkyl-
silanes were employed as an ole®n component.6
Results and Discussion
Initially the preparation of cycloalkenes 8 was studied. The
starting thioacetals 9 were prepared from the unsaturated
alcohols 10. After the transformation of 10 to the iodides
11 via the tosylate 12, 11 were treated with bis(phenylthio)-
methyllithium to produce the thioacetals 9 in good overall
yields from 10 (9a; 72%, 9b; 78%, 9c; 68%, 9d; 72%, 9e;
73%, 9f; 76%, 9g; 62%, 9h; 75%, 9i; 78%) (Scheme 4).
When the thioacetal 9a was treated with the low-valent
titanium 4 at room temperature for 17 h, a small amount
of 4-(3-phenylpropyl)cyclopentene 8a, the RCM product,
was obtained along with 1-methyl- and 1-methylene-3-
(3-phenylpropyl)cyclopentanes 13 and 14. The reaction of
9b with 4 at room temperature for 2 h followed by the
treatment with D2O produced 8a and the dideuterio
compound 15 (Scheme 5). The formation of 13 and 15
suggests that the titanacyclobutane 7 was produced as an
intermediate. It is reasonable to assume that 14 was formed
through the b-hydride elimination of 7.
Another approach to regioselective formation of titanacycle
intermediate 7 is to modify the reaction in an intramolecular
fashion. The transition metal catalyzed ring-closing meta-
thesis (RCM) of dienes is a useful method for the prepa-
ration of various cyclic compounds.7 Ruthenium,8
molybdenum,9 tungsten10 and rhenium11 complexes have
been employed as catalysts for such transformations.
Nicolaou et al. reported the preparation of cyclic ethers
from unsaturated esters by RCM using the Tebbe or Petasis
reagent, in which the alkylidenetitanocene was suggested to
serve as an intermediate.12 The formation of metathesis
products by the titanocene(II)-promoted reaction of thio-
acetals with allylsilanes prompted us to explore RCM
using thioacetals that have a carbon±carbon double bond.
This transformation proceeds via the formation of titana-
cyclobutane intermediate 7 by the intramolecular reaction
of titanium±carbene complex with a carbon±carbon double
bond and the subsequent elimination of alkylidenetitano-
cene 6 (Scheme 3).13
In order to accelerate the elimination of alkylidenetitano-
cene 6, the reaction mixture was re¯uxed for 1 h after the
treatment of thioacetal 9a with 4 at room temperature for 2 h
to afford the RCM product 8a in 71% yield. When benzo-
phenone (1.5 equiv.) was added to the reaction mixture prior
to heating, 1,1-diphenylethylene was produced in 10% yield
along with 8a (59%).14 This result supports our assumption
Scheme 3.
Scheme 4.

T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
4861
Scheme 5.
Table 1. Preparation of Cycloalkenes 8
Entry
Thioacetal 9
Titanocene (II) 4
(equiv.)/Concentration
of 9 (M)
Product 8
Yield (%)
1
3/0.03
71
67
2a
3/0.1
8a
8a
b
3a
3/0.1
8
4
3/0.03
4/0.03
3/0.1
87
74
50
5c
6a
7
3/0.03
3/0.03
4/0.015
87
58
8c,d
9
81e
a Carried out at room temperature for 1 h and then at re¯ux for 1 h.
b E:Zˆ82:18.
c Carried out at room temperature for 2 h and then at re¯ux for 3 h.
d 1-Benzyl-4-methylcycloheptane was obtained as a by-product in 9% yield.
e Contaminated with 6-benzyl-2-methyloct-1-ene (3%). The yield was corrected for the contaminant.

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T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
Scheme 6.
Scheme 7.
that alkylidene-titanocene 6 is formed by the decomposition
of titanacycle intermediate 7. In a similar manner, ®ve, six,
and seven-membered cycloalkenes were obtained in good
yields (Table 1). In the case of the thioacetal having a trisub-
stituted double bond 9c, the major product isolated was a
desulfurized acyclic hydrocarbon, 5-ethyl-2-methyl-8-
phenyloct-2-ene, and the RCM product 8a was obtained in
only 8% yield. The tendency to produce methyl group
substituted ole®ns in better yields than their unsubstituted
congeners was observed in these reactions. The composition
of equilibrium depicted in Scheme 3 is largely dependent on
the number and position of substituents on carbon±carbon
double bond. The equilibrium ratio is also dependent on the
ring size; the formation of 1-benzyl-4-methylcycloheptane
by the reaction of 9h indicates that a considerable amount of
the titanacyclobutane intermediate remained even after the
reaction mixture was re¯uxed for 3 h (Entry 8).
enyl)phenol (23) in 85 and 83% yields, respectively. These
phenols were obtained by the base-catalyzed isomerization
of the corresponding allylphenols.16 The condensation of the
tosylates 12 with 18 or 19 gave 17d±i in good yields (17d;
63%, 17e; 53%, 17f; 69%, 17g; 69%, 17h; 64%, 17i; 81%)
(Scheme 7).
Similarly to the preparation of cycloalkenes, the treatment
of the thioacetals 17 with titanocene(II) species 4 and subse-
quent thermal decomposition of the intermediate afforded
the seven- and eight-membered unsaturated cyclic ethers 16
(Table 2). In some cases, the isomerization of double bond
was observed (entries 3, 4 and 10). As shown in Table 2, this
new cyclization is applicable to not only cyclic ethers fused
with a benzene ring but also monocyclic compounds. The
formation of the latter rings would be a conformationally
less favorable process than the formation of bicyclic
compounds. The cyclic sul®de 24 was also obtained by
the RCM of the sul®de 25. The starting material 25 was
easily prepared in 89% yield by the reaction of tosylate 21
with the thiolate prepared in situ from the corresponding
thiolester 26 (Scheme 8).
Next we examined the application of this methodology to
the construction of cyclic ethers 16. The acyclic unsaturated
ethers 17 were prepared by the Williamson synthesis using
g-hydroxy thioacetals 18a and b or salicylaldehyde di-
phenyl thioacetal (19). The hydroxy thioacetal 18a was
easily prepared by the treatment of commercially available
methyl 3,3-dimethoxypropanoate with thiophenol in the
presence of BF3´OEt2 and the following reduction with
LiAlH4 (Scheme 6).15 The phenyl group substituted alcohol
18b was obtained in 93% yield by the reaction of styrene
oxide with bis(phenylthio)methyllithium. The condensation
of 2-allylphenol (20) with the tosylate 21 prepared from 18a
gave the thioacetal 17c in 83% yield. Similarly the thio-
acetals 17a and b were prepared by the reactions of 21
with 2-(prop-1-enyl)phenol (22) and 2-methoxy-6-(prop-1-
Conclusion
We have established a new cyclization reactions of thio-
acetals that have a carbon±carbon double bond promoted
with the low-valent titanium reagent 4. Because the starting
materials were easily prepared using the organosulfur build-
ing blocks, the present reaction provides a versatile
synthetic tool for the construction of cyclic compounds.
Although we have no direct experimental evidence for the

T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
4863
Table 2. Preparation of unsaturated cyclic ethers 16
Entry
Thioacetal 17
Titanocene (II) 4
(equiv.)/Concentration
of 17 (M)
Product 16
Yield (%)
1a
4/0.03
3/0.03
75
73
b
2a
3c
4
4/0.015
(82:18)
70
61
69
17c
3/0.015
3/0.03
16c
16d (98:2)
5
16a
6
3/0.03
3/0.03
3/0.03
71
69
65
7
8d
16d
9d
3/0.03
3/0.03
3/0.03
56
64e
50
10d
11d
a Carried out at room temperature for 1 h and then at re¯ux for 1 h.
b E:Zˆ96:4.
c Carried out at room temperature for 2 h and then at re¯ux for 3 h.
d The thioacetal was added dropwise over 3 h.
e A mixture of regioisomers (55:45).
intermediary of titanium±carbene complex, the formation
of RCM product indicates that this reaction proceeds
through the initial formation of such species. This active
organotitanium species should be reactive toward a variety
of organic molecules other than those having a carbon±
carbon or carbon±oxygen multiple bond. Indeed we have
already found their reactions with alkanenitriles,17 group 14
metal hydrides,18 and tert-alkyl halides.19 Further study on
the titanocene(II)-promoted reaction of thioacetal is now in
progress.
Experimental
General
Melting points were determined with a Yanaco MP-S3
micromelting point apparatus. 1H (500 MHz) and 13C
Scheme 8.

4864
T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
(125 MHz) NMR spectra were measured in CDCl3 on a Jeol
ALPHA-500 instrument. Chemical shifts are reported (d
scale) from internal tetramethylsilane for 1H and from
CDCl3 for 13C spectroscopies. IR spectra were recorded
on a Jeol Diamond-20 FT-IR spectrometer; absorptions
are reported in cm21. Elemental analyses were performed
on a Perkin Elmer 2400II.
1.48±1.61 (m, 2.54H), 1.58 (dd, 2.46H, Jˆ6.1, 0.9 Hz),
1.66±1.82 (m, 2H), 1.86±2.04 (m, 3H), 2.49±2.59 (m,
2H), 4.41 and 4.40 (2t, 1H, Jˆ7.5 Hz), 5.21 (ddt, 0.82H,
Jˆ15.3, 6.7, 1.5 Hz), 5.31 (dq, 0.82H, Jˆ15.3, 6.1 Hz),
5.18±5.35 (m, 0.18H), 5.45 (dq, 0.18H, Jˆ11.0, 6.7 Hz),
7.11±7.20 (m, 3H), 7.24±7.33 (m, 8H), 7.40±7.47 (m,
4H). 13C NMR 12.92, 17.95, 17.97, 27.98, 28.09, 30.45,
32.63, 32.78, 35.02, 35.35, 35.97, 36.04, 36.15, 40.04,
40.33, 56.65, 125.31, 125.62, 126.93, 127.63, 127.68,
127.97, 128.21, 128.36, 128.47, 128.80, 128.81, 132.75,
132.85, 132.87, 132.99, 134.09, 134.14, 142.47. Anal.
Calcd for C28H32S2: C, 77.73, H, 7.45. Found: C, 77.94,
H, 7.44.
Materials
Wakogel B-5F was used for preparative thin layer chroma-
tography (PTLC) and Merck Si 60 was used for column
chromatography as an adsorbent. THF was distilled from
sodium and benzophenone. Magnesium turnings were
purchased from Nacalai Tesque Inc. (Kyoto, Japan).
5-[2,2-Bis(phenylthio)ethyl]-2-methyl-8-phenyloct-2-ene
(9c). IR (neat) 3059, 3024, 2929, 1603, 1583, 1479, 1439,
1024, 748, 690. 1H NMR 1.20±1.32 (m, 2H), 1.47±1.56 (m,
2H), 1.52 (s, 3H), 1.63 (s, 3H), 1.67±1.81 (m, 2H), 1.86±
2.00 (m, 3H), 2.53 (t, 2H, Jˆ7.5 Hz), 4.41 (t, 1H,
Jˆ7.5 Hz), 4.93±5.01 (m, 1H), 7.10±7.15 (m, 2H), 7.15±
7.20 (m, 1H), 7.22±7.31 (m, 8H), 7.39±7.46 (m, 4H). 13C
NMR 17.84, 25.83, 28.12, 31.67, 32.89, 35.54, 36.03,
40.26, 56.60, 122.06, 125.62, 127.62, 128.21, 128.37,
128.81, 132.74, 132.89, 134.09, 134.14, 142.48. Anal.
Calcd for C29H34S2: C, 77.97; H, 7.67. Found: C, 78.07;
H, 7.66.
Preparation of thioacetals having a carbon±carbon
double bond 9
Preparation of 4-[2,2-bis(phenylthio)ethyl]-7-phenyl-
hept-1-ene (9a). To a pyridine (1.4 ml) solution of
2-(3-phenylpropyl)-4-penten-1-ol (878 mg, 4.3 mmol) was
added p-toluenesulfonyl chloride (902 mg, 4.73 mmol) at
08C, and the reaction mixture was stirred overnight. The
mixture was diluted with water (10 ml) and the organic
materials were extracted with ether (15 ml£2). The extracts
were combined, washed with 1 M HCl (5 ml£3), water, and
brine, and dried (Na2SO4). The crude tosylate was obtained
by removal of the solvent under reduced pressure. The tosyl-
ate and sodium iodide (2.13 g, 14.2 mmol) were dissolved in
acetone (6 ml), and the mixture was re¯ux for 2 h. After
cooling, the reaction mixture was diluted with water
(30 ml) and the organic materials were extracted with
ether (20 ml£2). The combined extracts were washed with
a saturated Na2SO3 solution and brine, dried (Na2SO4), and
condensed under reduced pressure to give the crude iodide.
To a THF solution of bis(phenylthio)methane (999 mg,
4.3 mmol) was added a hexane solution of butyllithium
(2.8 ml, 4.4 mmol) at 08C under argon. After 15 min, the
crude iodide in THF (5 ml) was added and the reaction
mixture was stirred for 2 h. The reaction was quenched by
addition of a saturated NH4Cl solution and the organic
materials were extracted with ether (20 ml£2). The
combined extracts were dried (Na2SO4) and condensed
under reduced pressure. The residue was puri®ed by silica
gel column chromatography to afford 9a (1.30 g, 72%). 9a:
IR (neat) 3074, 3060, 2931, 1637, 1583, 1479, 1439, 1024,
999, 914, 748, 690. 1H NMR 1.20±1.33 (m, 2H), 1.47±1.57
(m, 2H), 1.69±1.83 (m, 2H), 1.91±2.07 (m, 3H), 2.48±2.59
(m, 2H), 4.40 (t, 1H, Jˆ7.5 Hz), 4.88±4.97 (m, 2H), 5.63
(ddt, 1H, Jˆ16.9, 10.2, 6.7 Hz), 7.10±7.21 (m, 3H), 7.22±
7.33 (m, 8H), 7.38±7.47 (m, 4H). 13C NMR 27.92, 32.53,
34.72, 35.96, 37.58, 40.08, 56.63, 116.53, 125.65, 127.70,
128.22, 128.34, 128.82, 132.84, 132.94, 134.05, 136.14,
142.39. Anal. Calcd for C27H30S2: C, 77.46; H, 7.22.
Found: C, 77.72; H, 7.20.
4-[2,2-Bis(phenylthio)ethyl]-2-methyl-7-phenylhept-1-ene
(9d). IR (neat) 3060, 3024, 2933, 1647, 1583, 1479, 1439,
1
1026, 891, 748, 690. H NMR 1.21±1.30 (m, 2H), 1.43±
1.56 (m, 2H), 1.66 (s, 3H), 1.72±1.80 (m, 2H), 1.84±1.90
(m, 1H), 1.92±2.07 (m, 2H), 2.52 (t, 2H, Jˆ7.6 Hz), 4.41 (t,
1H, Jˆ7.5 Hz), 4.61 (s, 1H), 4.71 (s, 1H), 7.09±7.14 (m,
2H), 7.16±7.21 (m, 1H), 7.23±7.32 (m, 8H), 7.39±7.45 (m,
4H). 13C NMR 22.13, 22.15, 27.64, 32.72, 36.03, 40.56,
42.96, 56.67, 112.30, 125.66, 127.60, 127.70, 128.23,
128.36, 128.83, 132.66, 132.89, 134.14, 134.25, 142.42,
143.98. Anal. Calcd for C28H32S2: C, 77.73; H, 7.45.
Found: C, 77.92; H, 7.45.
4-Benzyl-6,6-bis(phenylthio)hex-1-ene (9e). IR (neat)
3074, 3060, 2920, 1639, 1583, 1479, 1439, 1026, 991,
1
914, 744, 702, 692. H NMR 1.74±1.88 (m, 2H), 1.95±
2.08 (m, 2H), 2.26±2.35 (m, 1H), 2.47 (dd, 1H, Jˆ13.4,
7.0 Hz), 2.56 (dd, 1H, Jˆ13.4, 7.0 Hz), 4.38 (t, 1H, Jˆ
7.5 Hz), 4.94±5.01 (m, 2H), 5.68 (ddt, 1H, Jˆ16.9, 10.2,
7.2 Hz), 7.05±7.10 (m, 2H), 7.16±7.20 (m, 1H), 7.21±7.31
(m, 8H), 7.31±7.37 (m, 2H), 7.37±7.42 (m, 2H). 13C NMR
36.95, 37.64, 39.83, 40.23, 56.57, 117.03, 125.93, 127.65,
127.79, 128.30, 128.78, 128.81, 129.19, 132.84, 133.28,
133.47, 133.99, 135.90, 140.30. Anal. Calcd for C25H26S2:
C, 76.88; H, 6.71. Found: C, 76.77; H, 6.65.
5-[2,2-Bis(phenylthio)ethyl]-8-phenyloct-1-ene (9f). IR
(neat) 3060, 3026, 2929, 1639, 1583, 1479, 1439, 1024,
1
999, 910, 748, 690. H NMR 1.21±1.37 (m, 4H), 1.44±
1.58 (m, 2H), 1.76 (t, 2H, Jˆ7.0 Hz), 1.82±1.97 (m, 3H),
2.53 (t, 2H, Jˆ7.5 Hz), 4.35 (t, 1H, Jˆ7.3 Hz), 4.87±5.00
(m, 2H), 5.73 (ddt, 1H, Jˆ16.9, 10.2, 6.7 Hz), 7.09±7.23
(m, 3H), 7.23±7.35 (m, 8H), 7.39±7.48 (m, 4H). 13C NMR
27.63, 30.43, 32.25, 32.41, 34.40, 36.02, 40.28, 56.68,
114.41, 125.65, 127.68, 127.71, 128.23, 128.35, 128.83,
132.63, 132.81, 132.90, 134.10, 134.13, 138.77, 142.39.
In a similar manner, the following thioacetals 9 were
obtained.
5-[2,2-Bis(phenylthio)ethyl]-8-phenyloct-2-ene (9b). (E:Zˆ
82:18) IR (neat) 3060, 3024, 2933, 1602, 1583, 1479, 1439,
1026, 968, 748, 698, 690. H NMR 1.19±1.32 (m, 2H),
1

T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
4865
Anal. Calcd for C28H32S2: C, 77.73; H, 7.45. Found: C,
77.78; H, 7.43.
puri®ed by PTLC (hexane) to yield 1-methyl-4-(3-phenyl-
propyl)cyclopentene (8b) (87 mg, 87%). 8b: IR (neat) 3027,
2925, 2844, 1655, 1604, 1496, 1452, 1014, 789, 748, 698.
1H NMR 1.38±1.47 (m, 2H), 1.57±1.66 (m, 2H), 1.68 (s,
3H), 1.84±1.97 (m, 2H), 2.22±2.38 (m, 2H), 2.38±2.47 (m,
1H), 2.60 (t, 1H, Jˆ7.6 Hz), 5.20±5.24 (m, 1H), 7.13±7.20
(m, 3H), 7.23±7.29 (m, 2H). 13C NMR 16.73, 30.24, 36.14,
36.43, 38.40, 39.18, 43.34, 123.42, 125.55, 128.20, 128.36,
139.51, 142.85. Anal. Calcd for C15H20: C, 89.94; H,10.06.
Found: C, 90.24; H, 10.34.
5-[2,2-Bis(phenylthio)ethyl]-2-methyl-8-phenyloct-1-ene
(9g). IR (neat) 3060, 3024, 2931, 1647, 1583, 1479, 1439,
1
1024, 887, 746, 690. H NMR 1.24±1.31 (m, 2H), 1.31±
1.39 (m, 2H), 1.46±1.56 (m, 2H), 1.66 (s, 3H), 1.76 (t, 2H,
Jˆ7.0 Hz), 1.81±1.89 (m, 3H), 2.54 (t, 2H, Jˆ7.5 Hz), 4.36
(t, 1H, Jˆ7.5 Hz), 4.60 (s, 1H), 4.66 (s, 1H), 7.10±7.21 (m,
3H), 7.23±7.33 (m, 8H), 7.41±7.46 (m, 4H). 13C NMR
22.50, 27.66, 31.07, 32.29, 34.25, 34.56, 36.02, 40.30,
56.73, 109.74, 125.65, 127.68, 127.70, 128.22, 128.35,
128.83, 132.84, 132.87, 134.13, 134.14, 142.39, 145.91.
Anal. Calcd for C29H34S2: C, 77.97; H, 7.67. Found: C,
78.08; H, 7.64.
In a similar manner, the following cycloalkenes 8 were
obtained.
4-(3-Phenylpropyl)cyclopentene (8a). IR (neat) 3062,
3026, 2924, 2844, 1604, 1496, 1452, 748, 698. H NMR
1
6-Benzyl-8,8-bis(phenylthio)oct-1-ene (9h). IR (neat)
3060, 3026, 2929, 1639, 1583, 1479, 1439, 1024, 999,
1.39±1.48 (m, 2H), 1.58±1.69 (m, 2H), 1.90±2.00 (m,
2H), 2.18±2.29 (m, 1H), 2.40±2.51 (m, 2H), 2.60 (t, 2H,
Jˆ7.6 Hz), 5.65 (s, 2H), 7.14±7.19 (m, 3H), 7.23±7.29 (m,
2H). 13C NMR 30.29, 36.14, 36.17, 37.56, 38.91, 125.56,
128.20, 128.35, 129.91, 142.78. Anal. Calcd for C14H18: C,
90.26; H, 9.74. Found: C, 90.65; H, 10.00.
1
912, 741, 700, 690. H NMR 1.18±1.41 (m, 4H), 1.75±
1.84 (m, 2H), 1.92±2.01 (m, 2H), 2.14±2.24 (m, 1H), 2.47
(dd, 1H, Jˆ13.6, 7.0 Hz), 2.56 (dd, 1H, Jˆ13.6, 7.0 Hz),
4.32 (t, 1H, Jˆ7.5 Hz), 4.89±5.01 (m, 2H), 5.73 (ddt, 1H,
Jˆ17.1, 10.1, 6.7 Hz), 7.04±7.08 (m, 2H), 7.16±7.37 (m,
11H), 7.37±7.42 (m, 2H). 13C NMR 25.31, 32.76, 33.83,
37.06, 40.26, 40.45, 56.70, 114.48, 125.84, 127.61,
127.77, 128.25, 128.76, 128.81, 129.16, 132.71, 133.31,
133.60, 134.11, 138.68, 140.51. Anal. Calcd for C27H30S2:
C, 77.46; H, 7.22. Found: C, 77.58; H, 7.18.
4-Benzylcyclopentene (8c). IR (neat) 3064, 3030, 2935,
2850, 1614, 1498, 1454, 744, 700, 671. H NMR 2.02±
1
2.11 (m, 2H), 2.38±2.47 (m, 2H), 2.53±2.63 (m, 1H), 2.68
(d, 2H, Jˆ7.6 Hz), 5.67 (s, 2H), 7.15±7.21 (m, 3H), 7.25±
7.32 (m, 2H). 13C NMR 38.56, 38.87, 42.27, 125.67, 128.18,
128.83, 129.74, 141.81. Anal. Calcd for C12H14: C, 91.08; H,
8.92. Found: C, 91.00; H, 9.02.
6-Benzyl-8,8-bis(phenylthio)-2-methyloct-1-ene (9i). IR
(neat) 3060, 3024, 2931, 1647, 1583, 1479, 1439, 1024,
1
887, 737, 700, 690. H NMR 1.16±1.28 (m, 2H), 1.28±
4-(3-Phenylpropyl)cyclohexene (8d). IR (neat) 3024,
2914, 2854, 1653, 1604, 1496, 1452, 910, 746, 698, 654.
1H NMR 1.15±1.38 (m, 3H), 1.49±1.78 (m, 5H), 1.99±2.04
(m, 3H), 2.60 (t, 2H, Jˆ7.7 Hz), 5.65 (s, 2H), 7.14±7.21 (m,
3H), 7.24±7.31 (m, 2H). 13C NMR 25.26, 28.82, 28.91,
31.87, 33.40, 36.19, 36.34, 125.56, 126.61, 127.01,
128.21, 128.35, 142.81. Anal. Calcd for C15H20: C, 89.94;
H, 10.06. Found: C, 90.25; H, 10.22.
1.44 (m, 2H), 1.66 (s, 3H), 1.77±1.82 (m, 2H), 1.91 (t,
2H, Jˆ7.5 Hz), 2.14±2.24 (m, 1H), 2.47 (dd, 1H, Jˆ13.4,
7.0 Hz), 2.56 (dd, 1H, Jˆ13.4, 6.7 Hz), 4.32 (t, 1H, Jˆ
7.5 Hz), 4.60 (s, 1H), 4.67 (s, 1H), 7.04±7.09 (m, 2H),
7.14±7.20 (m, 1H), 7.20±7.30 (m, 8H), 7.30±7.35 (m,
2H), 7.38±7.42 (m, 2H). 13C NMR 22.35, 24.04, 32.99,
37.10, 37.85, 40.28, 40.50, 56.67, 109.87, 125.84, 127.60,
127.77, 128.25, 128.76, 128.80, 129.15, 132.70, 133.30,
133.58, 134.07, 140.52, 145.72. Anal. Calcd for C28H32S2:
C, 77.73; H, 7.45. Found: C, 77.59; H, 7.58.
1-Methyl-4-(3-phenylpropyl)cyclohexene (8e). IR (neat)
3026, 2912, 1604, 1496, 1452, 800, 746, 698. H NMR
1
1.15±1.36 (m, 3H), 1.42±1.53 (m, 1H), 1.55±1.70 (m,
3H), 1.63 (s, 3H), 1.70±1.77 (m, 1H), 1.85±2.11 (m, 3H),
2.59 (t, 2H, Jˆ7.8 Hz), 5.34 (s, 1H), 7.14±7.19 (m, 3H),
7.23±7.29 (m, 2H). 13C NMR 23.55, 28.98, 29.36, 30.16,
32.06, 33.25, 36.16, 36.23, 120.63, 125.56, 128.21, 128.36,
133.94, 142.86. Anal. Calcd for C16H22: C, 89.66; H, 10.34.
Found: C, 89.47; H, 10.17.
Cyclization of 9
Cyclization of 9d. Finely powdered molecular sieves 4A
(150 mg), magnesium turnings (40 mg, 1.65 mmol), and
Cp2TiCl2 (374 mg, 1.5 mmol) were placed in a ¯ask and
dried by heating with a heat gun under reduced pressure
(2±3 mmHg). During this procedure, care was taken not
to sublime Cp2TiCl2. After cooling, THF (6.7 ml) and
P(OEt)3 (0.52 ml, 3 mmol) were added successively with
stirring at room temperature under argon. Within 15 min,
the reaction mixture turned dark green and then dark brown
with slight evolution of heat. After 3 h, the unsaturated
thioacetal 9d (216 mg, 0.5 mmol) in THF (10 ml) was
added to the reaction mixture, which was further stirred
for 2 h. Then the reaction mixture was re¯uxed for 1 h.
After cooling, the reaction was quenched with 1 M NaOH
(10 ml) and vigorously stirred for 20 min. The insoluble
materials were ®ltered off through celite and washed with
ether (50 ml). The organic phase was separated and dried
(Na2SO4). After removal of the solvent, the residue was
4-Benzylcycloheptene (8f). IR (neat) 3022, 2914, 2837,
1653, 1604, 1495, 1452, 750, 698. H NMR 1.29±1.43
1
(m, 2H), 1.65±1.81 (m, 2H), 1.85±1.99 (m, 2H), 2.02±
2.20 (m, 3H), 2.53 (d, 2H, Jˆ7.3 Hz), 5.64±5.71 (m, 1H),
5.78±5.85 (m, 1H), 7.10±7.22 (m, 3H), 7.24±7.31 (m, 2H).
13C NMR 25.82, 28.77, 34.09, 38.04, 39.15, 43.54, 125.66,
128.11, 129.18, 130.40, 132.89, 141.42. Anal. Calcd for
C14H18: C, 90.26; H, 9.74. Found: C, 90.63; H, 9.98.
4-Benzyl-1-methylcycloheptene (8g). IR (neat) 3028,
2913, 2848, 1604, 1496, 1454, 847, 748, 698. H NMR
1
1.28±1.39 (m, 2H), 1.62±1.75 (m, 2H), 1.70 (s, 3H),
1.81±1.95 (m, 2H), 1.95±2.08(m, 2H), 2.08±2.18 (m,

4866
T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
1H), 2.45±2.53 (m, 2H), 5.38±5.44 (m, 1H), 7.10±7.19 (m,
3H), 7.22±7.29 (m, 2H). 13C NMR 25.12, 26.08, 33.40,
33.99, 38.32, 39.20, 43.59, 123.72, 125.59, 128.07,
129.17, 141.20, 141.51. Anal. Calcd for C15H20: C, 89.94;
H, 10.06. Found: C, 89.86; H, 10.40.
1244, 1051, 1026, 972, 752, 690. 1H NMR 1.81 (dd, 0.12H,
Jˆ7.0, 1.8 Hz), 1.87 (dd, 2.88H, Jˆ6.7, 1.5 Hz), 2.33 (dt,
2H, Jˆ7.3, 5.8 Hz), 4.23 (t, 2H, Jˆ5.8 Hz), 4.78 (t, 1H,
Jˆ7.0 Hz), 5.79 (dq, 0.04H, Jˆ11.6, 7.0 Hz), 6.19 (dq,
0.96H, Jˆ15.9, 6.7 Hz), 6.47 (dd, 0.04H, Jˆ11.6, 1.8 Hz),
6.65 (dd, 0.96H, Jˆ15.9, 1.5 Hz), 6.78±6.85 (m, 1H), 6.86±
6.95 (m, 1H), 7.10±7.15 (m, 1H), 7.22±7.31 (m, 6H), 7.38
(dd, 1H, Jˆ7.6, 1.5 Hz), 7.43±7.48 (m, 4H). 13C NMR (E
isomer) 18.97, 35.60, 54.71, 64.88, 111.98, 120.89, 125.52,
126.30, 126.35, 127.11, 127.68, 127.73, 128.92, 132.50,
133.90, 155.03. Anal. Calcd for C24H24OS2: C, 73.43; H,
6.16. Found: C, 73.42; H, 6.12.
The dideuterio compound, 1-[1-2H]ethyl-3-(3-phenylpro-
pyl)[5-2H]cyclopentane (15), (47 mg, 43%) was obtained
by the reaction of 9b (216 mg, 0.5 mmol) at room tempera-
ture for 2 h followed by the treatment with D2O (0.5 ml). 15:
IR (neat) 3028, 2933, 2146, 1496, 1454, 1030, 748, 698. 1H
NMR 0.59±0.69 (m, 1H), 0.85 (d, Jˆ7.3 Hz, 3H), 1.09±
1.19 (m, 1H), 1.23±1.38 (m, 3H), 1.56±1.88 (m, 6H),
1.88±1.96 (m, 1H), 2.58 (t, Jˆ7.8 Hz, 2H), 7.13±7.19 (m,
3H), 7.24±7.29 (m, 2H). 13C NMR 12.94, 28.89 (t,
Jˆ19 Hz), 30.64, 30.83 (t, Jˆ20 Hz), 31.50, 36.26, 36.32,
40.06, 40.22, 41.79, 125.52, 128.20, 128.37, 142.96.
In a similar manner, the following thioacetals 17 were
obtained.
(E)-2-[3,3-Bis(phenylthio)propoxy]-1-methoxy-3-(prop-
1-enyl)benzene (17b). IR (neat) 3059, 3035, 2935, 1654,
1576, 1475, 1460, 1439, 1271, 1209, 1090, 1068, 1024, 972,
Preparation of the ethers having a carbon±carbon
double bond and a diphenyl thioacetal moiety 17
1
744, 690. H NMR 1.81 (dd, 1H, Jˆ6.7, 1.5 Hz), 2.28 (dt,
2H, Jˆ7.0, 6.0 Hz), 3.74 (s, 3H), 4.19 (t, 2H, Jˆ6.0 Hz),
4.91 (t, 1H, Jˆ7.0 Hz), 6.21 (dq, 1H, Jˆ15.9, 6.7 Hz), 6.68
(d, 1H, Jˆ15.9, 1.5 Hz), 6.74 (dd, 1H, Jˆ7.9, 1.5 Hz), 6.98
(t, 1H, Jˆ7.9 Hz), 7.04 (dd, 1H, Jˆ7.9, 1.5 Hz), 7.23±7.34
(m, 6H), 7.46±7.54 (m, 4H). 13C NMR 18.83, 36.31, 54.00,
55.62, 69.94, 110.47, 117.85, 123.93, 125.19, 127.21, 127.52,
128.83, 132.18, 132.53, 133.90, 144.75, 152.87. Anal. Calcd
for C25H26O2S2: C, 71.05; H, 6.20. Found: C, 71.09; H, 6.11.
Preparation of 1-phenyl-3,3-bis(phenylthio)propanol
(18b). To a THF (100 ml) solution of bis(phenylthio)-
methane (11.62 g, 50 mmol) was added a hexane solution
of butyllithium (35.6 ml, 55 mmol) at 08C with stirring
under argon. After 30 min, styrene oxide (6.8 ml, 60
mmol) was added and the reaction mixture was stirred for
1.5 h. The reaction was quenched by addition of a saturated
NH4Cl solution (30 ml) and the organic materials were
extracted with ether (50 ml£2). The combined extracts
were dried (Na2SO4) and condensed under reduced pressure.
The residue was puri®ed by silica gel column chroma-
tography (hexane:AcOEtˆ9:1) to give 18b (16.37 g,
93%). 18b: IR (neat) 3444, 3062, 2918, 1585, 1481, 1441,
1026, 744, 694. 1H NMR 2.10 (ddd, 1H, Jˆ14.7, 8.9,
4.3 Hz), 2.18 (br d, 1H, Jˆ2.2 Hz), 2.34 (ddd, 1H,
Jˆ14.7, 9.2, 5.5 Hz), 4.60 (dd, 1H, Jˆ8.9, 5.5 Hz), 5.13
(dt, 1H, Jˆ8.9, 4.1 Hz), 7.25±7.36 (m, 11H), 7.42±7.47
(m, 4H). 13C NMR 44.58, 54.51, 71.74, 125.77, 127.69,
127.79, 127.83, 128.57, 128.92, 132.51, 132.72, 133.50,
133.76, 143.54. Anal. Calcd for C21H20OS2: C, 71.55; H,
5.72. Found: C, 71.37; H, 5.73.
1-Allyl-2-[3,3-bis(phenylthio)propoxy]benzene (17c). IR
(neat) 3074, 3060, 2927, 1637, 1585, 1495, 1454, 1439,
1
1248, 1025, 914, 754, 692. H NMR 2.32 (dt, 2H, Jˆ7.0,
5.8 Hz), 3.31 (d, 2H, Jˆ6.4 Hz), 4.22 (t, 2H, Jˆ5.8 Hz),
4.77 (t, 1H, Jˆ7.0 Hz), 4.94±5.02 (m, 2H), 5.87±5.97 (m,
1H), 6.83 (d, 1H, Jˆ7.9 Hz), 6.90 (dt, 1H, Jˆ7.3, 0.9 Hz),
7.13 (dd, 1H, Jˆ7.3, 1.8 Hz), 7.17 (dt, 1H, Jˆ7.9, 1.5 Hz),
7.24±7.35 (m, 6H), 7.43±7.52 (m, 4H). 13C NMR 34.38,
35.72, 54.36, 64.39, 111.07, 115.32, 120.64, 127.32,
127.63, 128.35, 128.89, 129.82, 132.38, 133.91, 136.85,
156.11. Anal. Calcd for C24H24OS2: C, 73.43; H, 6.16.
Found: C, 73.32; H, 6.09.
Preparation of 1-(3-methylbut-3-enyloxy)-2-[bis(phenyl-
thio)methyl]benzene (17e). To an acetone (15 ml) solution
of the crude tosylate prepared from 3-methyl-3-buten-1-ol
(947 mg, 11 mmol) and p-toluenesulfonyl chloride (2.31 g,
12.1 mmol) was added K2CO3 (1.52 mg, 11 mmol) and
2-bis(phenylthio)methylphenol (19) (3.25 g, 10 mmol).
After being re¯uxed for 20 h, the reaction mixture was
diluted with water (40 ml) and the organic materials were
extracted with ether (30 ml£2). The combined extracts were
dried (Na2SO4) and condensed under reduced pressure. The
residue was puri®ed by silica gel column chromatography
(hexane:AcOEtˆ98:2) to give 17e (2.09 g, 53%). 17e: IR
(neat) 3064, 2968, 1657, 1572, 1491, 1263, 1221, 1057, 897,
860, 756. 1H NMR 1.75 (s, 3H), 2.45 (t, 2H, Jˆ6.4 Hz), 4.03
(t, 2H Jˆ6.4 Hz), 4.77 (s, 1H), 4.80 (s, 1H), 6.13 (s, 1H),
6.80 (d, 1H, Jˆ8.2 Hz), 6.90 (t, 1H, Jˆ7.5 Hz), 7.15±7.23
(m, 7H), 7.31±7.36 (m, 4H), 7.60 (d, 1H, Jˆ7.9 Hz). 13C
NMR 22.45, 37.31, 52.01, 66.33, 111.27, 112.33, 120.79,
127.16, 128.02, 128.60, 128.90, 128.99, 131.60, 135.27,
141.93, 154.86. Anal. Calcd for C24H24OS2: C, 73.43; H,
6.16. Found: C, 73.47; H, 6.20.
Preparation of 1-[3,3-bis(phenylthio)propoxy]-2-(prop-
1-enyl)benzene (17a). To a pyridine (1.4 ml) solution of
18a (1.11 g, 4 mmol) was added p-toluenesulfonyl chloride
(839 mg, 4.4 mmol) at 08C under argon, and the reaction
mixture was stirred for 12 h. The mixture was diluted with
water (10 ml) and the organic materials were extracted
with ether (15 ml£2). The extracts were combined, washed
with 1 M HCl (5 ml£3), water, and brine, and dried
(Na2SO4). To an acetone (6.7 ml) solution of the crude
tosylate 21 obtained by removal of the solvent under
reduced pressure were added K2CO3 (663 mg, 4.8 mmol)
and 2-(prop-1-enyl)phenol 22 (644 mg, 4.8 mmol), and the
mixture was re¯uxed for 20 h. The reaction mixture was
diluted with water (30 ml) and the organic materials were
extracted with ether (20 ml£2). The combined extracts were
washed with water and brine, dried (Na2SO4), and
condensed under reduced pressure. The residue was puri®ed
by silica gel column chromatography (hexane:
AcOEtˆ95:5) to give 17a (1.34 g, 85%) (E:Zˆ96:4). 17a:
IR (neat) 3059, 3033, 2929, 1597, 1581, 1489, 1452, 1439,

T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
4867
In a similar manner, the following thioacetals 17 were
obtained.
136.73, 140.58. Anal. Calcd for C27H30OS2: C, 74.61; H,
6.96. Found: C, 74.73; H, 6.92.
1-(But-3-enyloxy)-2-[bis(phenylthio)methyl]benzene (17d).
IR (neat) 3076, 2937, 1643, 1583, 1491, 1248, 1026, 989,
In a similar manner, 1-phenyl-3,3-bis(phenylthio)propyl
pent-4-enyl ether (17i) was obtained. 17i: IR (neat) 3059,
1
1
2937, 1639, 1583, 1439, 1342, 1097, 912, 737, 690. H
906, 748, 690. H NMR 2.50 (tq, 2H, Jˆ6.7, 1.2 Hz), 3.98
(t, 2H, Jˆ6.7 Hz), 5.04±5.16 (m, 2H), 5.85 (ddt, 1H,
Jˆ17.1, 10.4, 6.7 Hz), 6.10 (s, 1H), 6.80 (dd, 1H, Jˆ8.2,
0.9 Hz), 6.91 (dt, 1H, Jˆ7.6, 0.9 Hz), 7.16±7.24 (m, 7H),
7.31±7.36 (m, 4H), 7.58 (dd, 1H, Jˆ7.6, 1.8 Hz). 13C NMR
33.74, 52.28, 67.49, 111.46, 117.12, 120.88, 127.23, 128.15,
128.64, 128.97, 129.00, 131.73, 134.51, 135.30, 154.90.
Anal. Calcd for C23H22OS2: C, 72.98; H, 5.86. Found: C,
73.01; H, 5.96.
NMR 1.57±1.65 (m, 2H), 1.89 (dddd, 1H, Jˆ14.7, 9.5,
4.3, 1.5 Hz), 2.01±2.11 (m, 2H), 2.36 (dddd, 1H, Jˆ14.7,
9.5, 5.0, 1.7 Hz), 3.20 (dt, 1H, Jˆ9.2, 6.4 Hz), 3.31 (dt, 1H,
Jˆ9.2, 6.4 Hz), 4.62±4.68 (m, 2H), 4.89±4.99 (m, 2H), 5.76
(ddt, 1H, Jˆ17.1, 10.4, 6.7 Hz), 7.21±7.35 (m, 11H), 7.41±
7.46 (m, 4H). 13C NMR 29.10, 30.39, 44.59, 54.10, 68.23,
78.97, 114.63, 126.54, 127.40, 127.59, 127.69, 128.44,
128.85, 132.11, 132.48, 133.96, 134.21, 138.29, 141.79.
Anal. Calcd for C26H28OS2: C, 74.24; H, 6.71. Found: C,
74.05; H, 6.78.
1-(3-Ethylbut-3-enyloxy)-2-[bis(phenylthio)methyl]ben-
zene (17f). IR (neat) 3078, 2970, 1647, 1585, 1489, 1248,
1
1026, 741. H NMR 1.03 (t, 3H, Jˆ7.3 Hz), 2.06 (q, 2H,
Preparation of 2-benzylpent-4-enyl 3,3-bis(phenylthio)-
propyl sul®de (25). To an ethanol (2 ml) solution of KOH
(85%, 0.28 g, 6 mmol) was added an ethanol (4 ml) solution
of S-2-benzylpent-4-enyl thioacetate (26) (703 mg, 3 mmol)
under argon, and the reaction mixture was stirred for 2.5 h at
room temperature. After cooling to 08C, the crude tosylate
21, prepared from 18a (912 mg, 3.3 mmol) and p-toluene-
sulfonyl chloride (692 mg, 3.6 mmol), in ethanol (1 ml) was
added and the reaction mixture was gradually warmed up to
room temperature. After being stirred overnight, the reac-
tion mixture was diluted with water (10 ml) and the organic
materials were extracted with ether (10 ml£3). The
combined extracts were dried (Na2SO4) and condensed
under reduced pressure. The residue was puri®ed by silica
gel column chromatography (hexane:AcOEtˆ10:1) to give
25 (1.21 g, 89%). 25: IR (neat) 3060, 2916, 1639, 1583,
Jˆ7.3 Hz), 2.47 (t, 2H, Jˆ6.7 Hz), 4.03 (t, 2H, Jˆ6.7 Hz),
4.79 (s, 1H), 4.81 (s, 1H), 6.12 (s, 1H), 6.80 (d, 1H,
Jˆ8.2 Hz), 6.90 (t, 1H, Jˆ7.6 Hz), 7.15±7.24 (m, 7H),
7.30±7.36 (m, 4H), 7.58 (d, 1H, Jˆ7.6 Hz). 13C NMR
12.27, 28.91, 35.82, 52.03, 66.73, 109.98, 111.29, 120.77,
127.17, 128.61, 128.92, 128.99, 131.63, 135.28, 147.47,
154.90. Anal. Calcd for C25H26OS2: C, 73.85; H, 6.45.
Found: C, 74.07; H, 6.48.
1-(Pent-4-enyloxy)-2-[bis(phenylthio)methyl]benzene (17g).
IR (neat) 3060, 2941, 1641, 1583, 1481, 1248, 1099, 1001,
1
914, 748, 690. H NMR 1.81±1.89 (m, 2H), 2.19 (dt, 2H,
Jˆ7.6, 6.7 Hz), 3.94 (t, 2H, Jˆ6.4 Hz), 4.95±5.04 (m, 2H),
5.81 (ddt, 1H, Jˆ17.1, 10.1, 6.7 Hz), 6.08 (s, 1H), 6.79 (d,
1H, Jˆ8.2 Hz), 6.88 (t, 1H, Jˆ7.6 Hz), 7.06±7.22 (m, 7H),
7.30±7.36 (m, 4H), 7.57 (d, 1H, Jˆ7.6 Hz). 13C NMR
28.45, 30.16, 52.64, 67.44, 111.37, 115.23, 120.66,
127.23, 127.93, 128.66, 128.90, 129.00, 131.67, 135.34,
137.68, 155.05. Anal. Calcd for C24H24OS2: C, 73.43; H,
6.16. Found: C, 73.81; H, 6.21.
1
1481, 1439, 914, 744, 690. H NMR 1.86±1.93 (m, 1H),
2.02 (q, 2H, Jˆ7.0 Hz), 2.11 (t, 2H, Jˆ7.0 Hz), 2.34 (dd,
1H, Jˆ12.7, 6.3 Hz), 2.37 (dd, 1H, Jˆ12.7, 6.3 Hz), 2.59
(dd, 1H, Jˆ13.7, 7.0 Hz), 2.66 (dd, 1H, Jˆ13.7, 7.0 Hz),
2.72 (t, 2H, Jˆ7.0 Hz), 4.60 (t, 1H, Jˆ6.9 Hz), 5.00±5.07
(m, 2H), 5.67±5.77 (m, 1H), 7.12±7.21 (m, 3H), 7.23±7.33
(m, 8H), 7.43±7.49 (m, 4H). 13C NMR 29.97, 35.26,
35.71, 36.95, 39.09, 39.98, 56.66, 117.04, 125.97,
127.80, 128.28, 128.92, 129.21, 132.80, 133.82, 136.11,
140.24. Anal. Calcd for C27H30S3: C, 71.95; H, 6.71.
Found: C, 71.95; H, 6.61.
Preparation of 2-benzylpent-4-enyl 3,3-bis(phenylthio)-
propyl ether (17h). To a ¯ask charged with NaH (55%
dispersion in mineral oil, 52 mg, 1.2 mmol) was added a
DMF (0.5 ml) solution of 18a (276 mg, 1 mmol) dropwise
at room temperature under argon. After the evolution of
hydrogen was terminated, the tosylate prepared from
2-benzylpent-4-en-1-ol (212 mg, 1.2 mmol) and p-toluene-
sulfonyl chloride (252 mg, 1.32 mmol) in DMF (0.4 ml)
was added at 08C and the reaction mixture was warmed
up to room temperature. After being stirred for 19 h, the
reaction was quenched by addition of water (5 ml) and
the organic materials were extracted with ether (10 ml£3).
The combined extracts were dried (Na2SO4) and condensed
under reduced pressure. The residue was puri®ed by PTLC
(hexane:AcOEtˆ98:2) to give 17h (278 mg, 64%). 17h: IR
(neat) 3062, 2920, 1639, 1583, 1481, 1438, 1117, 1026, 995,
741, 692. 1H NMR 1.87±1.98 (m, 1H), 2.02±2.14 (m, 4H),
2.63 (dd, 1H, Jˆ13.6, 7.5 Hz), 2.57 (dd, 1H, Jˆ13.6,
6.9 Hz), 3.22 (dd, 2H, Jˆ5.5, 1.5 Hz), 3.60 (dt, 2H,
Jˆ6.8, 1.2 Hz), 4.69 (dt, 1H, Jˆ7.0, 2.1 Hz), 4.97±5.04
(m, 2H), 5.72±5.82 (m, 1H), 7.11±7.20 (m, 3H), 7.22±
7.32 (m, 8H), 7.44±7.49 (m, 4H). 13C NMR 35.46, 36.20,
37.25, 40.33, 54.30, 67.44, 72.15, 116.37, 125.79, 127.46,
127.48, 128.17, 128.85, 129.22, 132.21, 132.27, 134.28,
Cyclization of 17 and 25
The reactions of 17 and 25 were performed with a similar
procedure described above, and the following cyclic ethers
and sul®de were obtained.
2,3-Dihydro-1-benzoxepin (16a). IR (neat) 3024, 2960,
2929, 1488, 1452, 1444, 1248, 1215, 1111, 997, 773, 756,
741. 1H NMR 2.67 (ddt, 2H, Jˆ4.9, 4.6, 1.8 Hz), 4.24 (t, 2H,
Jˆ4.9 Hz), 5.97 (dt, 1H, Jˆ11.6, 4.6 Hz), 6.33 (dt, 1H,
Jˆ11.6, 1.8 Hz), 6.98±7.00 (m, 2H), 7.12 (dt, 1H, Jˆ7.6,
1.5 Hz), 7.17 (dd, 1H, Jˆ7.6, 1.5 Hz). 13C NMR 34.23,
69.47, 119.86, 122.32, 126.79, 127.87, 128.69, 130.21,
132.67, 158.87. Anal. Calcd for C10H10O: C, 82.16; H,
6.90. Found: C, 82.56; H, 7.10.
2,3-Dihydro-9-methoxy-1-benzoxepin (16b). Mp: 69±
69.58C. IR (KBr) 3024, 3014, 2925, 1576, 1487, 1460,

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T. Fujiwara et al. / Tetrahedron 56 (2000) 4859±4869
1
1442, 1263, 1207, 987, 796, 739. H NMR 2.68 (ddt, 2H,
Jˆ4.9, 4.6, 1.8 Hz), 3.86 (s, 3H), 4.31 (t, 2H, Jˆ4.9 Hz),
5.98 (dt, 1H, Jˆ11.6, 4.6 Hz), 6.30 (dt, 1H, Jˆ11.6, 1.8 Hz),
6.74±6.80 (m, 2H), 6.91 (t, 1H, Jˆ7.9 Hz). 13C NMR 34.18,
56.03, 70.17, 110.36, 121.83, 124.52, 127.41, 128.51,
130.65, 148.33, 150.32. Anal. Calcd for C11H12O2: C,
74.98; H, 6.86. Found: C, 74.80; H, 6.87.
A mixture of 8-phenyl-3,4,7,8-tetrahydro-2H-oxocin
(16h) and 2-phenyl-3,4,7,8-tetrahydro-2H-oxocin (16i)
(55: 45). IR (neat) 3020, 2933, 1645, 1454, 1273, 1097,
1028, 754, 721, 698. 1H NMR 1.45±1.55 (m, 0.55H),
1.73±1.90 (m, 0.90H), 1.94±2.03 (m, 0.55H), 2.08±2.22
(m, 1.45H), 2.38±2.45 (m, 0.55H), 2.48±2.68 (m, 2H),
3.46 (ddd, 0.55H, Jˆ12.2, 9.8, 2.4 Hz), 3.58 (dt, 0.45H,
Jˆ11.8, 3.4 Hz), 3.97±4.06 (m, 1H), 4.38±4.46 (m, 1H),
5.76±5.94 (m, 2H), 7.12±7.38 (m, 5H). 13C NMR 23.62,
24.05, 29.43, 30.60, 35.48, 37.92, 68.73, 70.82, 81.31,
82.73, 125.44, 125.91, 126.78, 127.05, 127.53 128.16,
128.18, 128.87, 131.31, 131.63, 143.53, 144.52. Anal.
Calcd for C13H16O: C, 82.93; H, 8.57. Found: C, 82.82; H,
8.75.
A mixture of 3,6-dihydro-2H-1-benzoxocin (16c) and
3,4-dihydro-2H-1-benzoxocin (16d) (82: 18). IR (neat)
3018, 2927, 2871, 1491, 1441, 1286, 1252, 1223, 1103,
1005, 775, 733, 704. 1H NMR 1.69±1.76 (m, 0.36H),
2.30±2.42 (m, 2H), 3.41 (d, 1.64H, Jˆ6.7 Hz), 4.05 (t,
1.64H, Jˆ5.2 Hz), 4.27 (dt, 0.36H, Jˆ5.5, 2.1 Hz), 5.62
(dt, 0.82H, Jˆ11.0, 7.6 Hz), 5.76 (ddt, 0.18H, Jˆ11.9,
7.0, 1.8 Hz), 5.91 (ddt, 0.82H, Jˆ11.0, 6.7, 0.9 Hz), 6.33
(d, 0.18H, Jˆ11.9 Hz), 6.95±7.05 (m, 2H), 7.06±7.11 (m,
0.36H), 7.11±7.22 (m, 1.64H). 13C NMR (16c): 27.86,
32.34, 73.59, 122.63, 124.17, 126.44, 127.91, 129.39,
133.10, 136.85, 157.42. Anal. Calcd for C11H12O: C,
82.46; H, 7.55. Found: C, 82.62; H, 7.53.
3-Benzyl-3,4,7,8-tetrahydro-2H-thiacin (24). IR (neat)
3026, 2925, 1653, 1497, 1456, 1415, 1342, 1273, 1030,
1
748, 725, 698. H NMR 2.06±2.15 (m, 1H), 2.15±2.26
(m, 1H), 2.34±2.44 (m, 1H), 2.44±2.72 (m, 8H), 5.60 (dt,
1H, Jˆ10.4, 7.6 Hz), 5.74 (dt, 1H, Jˆ10.4, 7.6 Hz), 7.12±
7.22 (m, 3H), 7.25±7.31 (m, 2H). 13C NMR 29.59, 30.39,
33.98, 35.18, 40.18, 43.33, 125.90, 128.31, 129.10, 130.03,
130.16, 140.75. Anal. Calcd for C14H18S: C, 77.01; H, 8.31.
Found: C, 76.87; H, 8.25.
3,4-Dihydro-2H-1-benzoxocin (16d). IR (neat) 3022,
2945, 1641, 1495, 1257, 1211, 1065, 752. H NMR 1.68±
1
1.76 (m, 2H), 2.34±2.42 (m, 2H), 4.27 (t, 2H, Jˆ5.7 Hz),
5.75 (dt, 1H, Jˆ11.6, 7.0 Hz), 6.35 (d, 1H, Jˆ11.6 Hz),
6.96±7.01 (m, 2H), 7.06±7.11 (m, 1H), 7.15±7.21 (m,
1H). 13C NMR 23.79, 26.54, 71.11, 121.89, 122.57,
127.36, 128.35, 128.69, 130.08, 131.27, 156.11. Anal.
Calcd for C11H12O: C, 82.46; H, 7.55. Found: C, 82.38; H,
7.75.
Acknowledgements
This work was supported by a Grant-in-Aid for Scienti®c
Research from the Ministry of Education, Science, Sports,
and Culture, Japan (no. 11119214 and 11440213).
4-Methyl-2,3-dihydro-1-benzoxepin (16e). IR (neat)
3064, 2968, 1657, 1491, 1263, 1221, 1057, 756. H NMR
1
1.95 (s, 3H), 2.59 (t, 2H, Jˆ4.9 Hz), 4.21 (t, 2H, Jˆ4.9 Hz),
6.14 (s, 1H), 6.91 (d, 1H, Jˆ7.6 Hz), 6.94 (dt, 1H, Jˆ7.3,
1.2 Hz), 7.05 (dt, 1H, Jˆ7.6, 1.8 Hz), 7.10 (dd, 1H, Jˆ7.6,
1.5 Hz). 13C NMR 26.42, 38.63, 68.84, 119.65, 122.30,
124.90, 126.64, 126.93, 132.24, 139.00, 158.68. Anal.
Calcd for C11H12O: C, 82.46; H, 7.55. Found: C, 82.44; H,
7.52.
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1
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