W(CO)5(L)-catalyzed 6-endo-selective cyclization and formal Cope rearrangement of allenyl silyl enol ethers

Article abstract of DOI:10.1016/j.jorganchem.2006.08.037

On treatment of 5-siloxy-1,2,5-trienes with a catalytic amount of W(CO)₆ under photoirradiation, two types of synthetically useful compounds, that is, 6-endo-cyclized products or formal Cope rearrangement products, are obtained selectively via

Full text of DOI:10.1016/j.jorganchem.2006.08.037

Journal of Organometallic Chemistry 692 (2007) 562–568
www.elsevier.com/locate/jorganchem
W(CO)5(L)-catalyzed 6-endo-selective cyclization and formal
Cope rearrangement of allenyl silyl enol ethers
1
*
Tomoya Miura , Koichi Kiyota, Hiroyuki Kusama, Nobuharu Iwasawa
Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
Received 23 February 2006; received in revised form 11 April 2006; accepted 18 April 2006
Available online 26 August 2006
Abstract
On treatment of 5-siloxy-1,2,5-trienes with a catalytic amount of W(CO)6 under photoirradiation, two types of synthetically useful
compounds, that is, 6-endo-cyclized products or formal Cope rearrangement products, are obtained selectively via the same intermediates
simply by changing reaction conditions. In these reactions, electrophilic activation of the allene moiety is effectively achieved by coor-
dination of W(CO)5, allowing intramolecular attack by neutral carbon nucleophiles in a 6-endo manner.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Cyclization; Cope rearrangement; Allene; Electrophilic activation; Tungsten
1. Introduction
the reaction using a catalytic amount of W(CO)6 under
photoirradiation in the presence of H2O (Eq. (1)) [5f]. We
then decided to examine whether it would be possible to
apply this reaction to 5-siloxy-1,2,5-trienes where the com-
petitive cyclization modes (5-exo versus 6-endo) are possi-
ble (Eq. (2)). In this paper, we would like to describe a
full account of our study on this type of substrate, which
has led to the discovery of two distinctive reaction path-
ways, that is, the 6-endo-selective cyclization and the for-
mal Cope rearrangement [6].
Allenyl compounds play an important role in synthetic
reactions due to their unique structure and high reactivity
[1]. In particular, transition metal-catalyzed cyclization of
allenes bearing a pro-nucleophile such as oxygen and nitro-
gen has attracted much attention as a useful synthetic pro-
tocol for the construction of heterocycles. A variety of
transition-metal catalysts such as mercury(II), palladium(0
or II), silver(I), gold(III), and so on have been employed
for this purpose [1,2] and applied for the synthesis of sev-
eral natural products [3]. On the other hand, transition
metal-catalyzed cyclization of allenes bearing carbon nucle-
ophiles has remained relatively unexplored despite its high
potential as a method for the formation of carbocycles [4].
In the course of our studies on W(CO)5(L)-catalyzed
intramolecular cyclization of silyl enol ethers, we found
that W(CO)5 can effectively activate the allenyl moiety as
well as the alkyne moiety [5]. For example, 5-endo-selective
cyclization of 6-siloxy-1,2,5-trienes was found to proceed
smoothly to give cyclopentene derivatives by carrying out
1
O
R3SiO
2
W(CO)6, H2O
THF
6
4
3
5
R'
R'
ð1Þ
hν,
6-siloxy-1,2,5-triene
5-endo
O
path A
R3SiO
3
5
4
W(CO)5
1
2
5-exo
O
path A
ð2Þ
path B
5-siloxy-1,2,5-triene
path B
*
Corresponding author.
E-mail address: niwasawa@chem.titech.ac.jp (N. Iwasawa).
Present address: Department of Synthetic Chemistry and Biological
1
6-endo
Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan.
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.037

T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
563
Table 1
2. Results and discussion
6-endo-Selective cyclization of 5-siloxy-1,2,5-triene 1 using a catalytic
amount of W(CO)6 in THF
When 5-triethylsiloxy-1,2,5-triene 1a was treated with
an equimolar amount of W(CO)6 in THF (0.1 M) at
40 °C under photoirradiation in the presence of H2O
(10 equiv), 1a was completely consumed within 1 day to
give the 6-endo-cyclized product, cyclohex-3-en-1-one 2a,
in 74% yield (Scheme 1) [7]. It should be noted here that
the cyclization proceeded with high regio-selectivity, lead-
ing to the exclusive formation of the 6-endo-cyclized prod-
uct. Although the corresponding catalytic reactions under
the same concentration (0.1 M) of the substrate 1a gave
the desired cyclized product 2a in low yield (28% yield)
along with the hydrolyzed ketone as the major product,
this catalytic reaction could be carried out successfully by
carrying out the reaction under high concentration (1 M
for 1a) even with a catalytic amount (as little as
20 mol%) of W(CO)6 in the presence of H2O (3 equiv) to
give 2a in 68% yield. Other metal complexes such as PtCl2
and AgNO3 failed to give better results. The reaction path-
way is assumed to proceed in a similar manner to the
5-endo cyclization of 6-siloxy-1,2,5-trienes [5f]. First, coor-
dination of W(CO)5, generated in situ from W(CO)6 under
photoirradiation, onto the allenyl moiety gives the allene–
W(CO)5 g2-complex A. Then, intramolecular attack of
the silyl enol ether occurs on the distal carbon of the elec-
trophilic allene moiety to give the cyclohexenyl tungsten
species B. Finally, the carbon–tungsten bond is protonated
by H2O to give the 6-endo-cyclized product 2a with regen-
eration of the W(CO)5(thf).
Entry
1
Substrate
Product
Yield/%
77a
TESO
O
Ph
Me
Ph
Ph
Me
Ph
2b
1b
2
71a
TESO
O
2c
1c
3
26b
TESO
O
2d
1d
4
71a
TESO
O
The scope of this reaction was examined employing sev-
eral 5-siloxy-1,2,5-trienes using a catalytic amount of
W(CO)6 (Table 1). The catalytic process worked well with
substrates 1b and 1c containing a tri-substituted silyl enol
ether moiety to give the corresponding products 2b and
2c in good yield (entries 1–2). On the other hand, the reac-
tion of 1d bearing a tri-substituted allene moiety gave the
Ph
Ph
2e
1e
5
84c
TBSO
O
TESO
O
X mol% W(CO)
6
Y equiv H O
2
2f
1f
hν, THF, 40 ˚C
Ph
Ph
74% (X=100, Y=10)
68% (X=20, Y=3)
1a
2a
6
69a
O
TESO
–W(CO) (thf)
5
–TESOH
W(CO) (thf)
5
H O
2
TESO
TESO
2g
1g
Ph
Ph
W(CO)
a
Conditions A: W(CO)6 (20 mol%), H2O (3.0 equiv), THF (1.0 M),
5
40 °C, hm.
W(CO)
2
b
5
Conditions B: W(CO)6 (100 mol%), H2O (1.0 equiv), THF (0.1 M),
40 °C, hm.
B (cyclohexenyl tungsten species)
Scheme 1.
A (
η -complex)
c
Conditions C: W(CO)6 (10 mol%), H2O (3.0 equiv), THF (0.1 M),
40 °C, hm.

564
T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
product 2d in only 26% yield even with a stoichiometric
amount of W(CO)6 due to the facile hydrolysis of the silyl
enol ether moiety during the reaction (entry 3). In the case
of substrate 1e containing both of these tri-substituted silyl
enol ether and allene moieties, the reaction gave the prod-
uct 2e as a single diastereoisomer in 71% yield (entry 4).
The stereochemistry of 2e was assigned as cis on the basis
of a differential NOE study. It is thought that the interme-
diate cis-B may be more favorable than the trans-B due to
the considerable steric repulsion in the trans-B between the
pentacarbonyltungsten moiety and the methyl group on the
C-5 (Fig. 1). Furthermore, this 6-endo cyclization reaction
was also found to proceed smoothly with cyclic substrates
1f and 1g. Compound 2f was obtained in 84% yield even
with 10 mol% amount of W(CO)6, while 2g was produced
by isomerization of the double bond after cyclization
(entries 5 and 6).
During these studies, we found that the reaction of the
same substrate 1a in the absence of H2O under similar con-
ditions proceeded via a different pathway to give a formal
Cope rearrangement product, 2-siloxy-1-en-5-yne 3a, in
good yield (Table 2) [8–10]. Thus, when 5-siloxy-1,2,5-tri-
ene 1a was treated with a catalytic amount of W(CO)6
(20 mol%) in THF at 40 °C under photoirradiation for
1 day, the product 3a was obtained in 81% yield together
with a trace amount of the cyclized product 2a (Table 2,
entry 1). It should be noted that thermal Cope rearrange-
ment of 1,2,5-trienes normally requires high reaction tem-
perature (>250 °C) [8–10]. In fact, when the substrate 1a
was heated at 250 °C for 4 h in the absence of the catalyst,
the Cope rearrangement gradually proceeded to give a 3:1
mixture of 1a and 3a. Furthermore, no reaction occurred
when the substrate 1a was irradiated in the absence of
W(CO)6 (entry 2), and thus, activation of the substrate
O
TESO
diafavor
5
Ph
Ph
trans-B
TESO
W(CO)5
trans-2e
Ph
O
TESO
W(CO)5
A (η2-complex)
favor
5
Ph
Ph
W(CO)5
cis-2e
cis-B
Fig. 1. Stereoselectivity of 6-endo cyclization of the substrate 1e.
Table 2
Reaction of 5-siloxy-1,2,5-triene 1a using a catalytic amount of W(CO)6 in the absence of H2Oa
TESO
OTES
20 mol% W(CO)6
Ph
hν, 40 ˚C
Ph
1a
3a
Entry
Solvent
Additive
Time/h
3a/%b
1
2
3
4
5
6
THF
THF
Toluene
Toluene
Toluene
Toluene
–
–
–
24
24
2
2
2
81
nrc
71
90
72
62
DABCO
n-Bu3N
i-Pr2NEt
2
Abbreviations: nr, no reaction; –, no additive.
a
Unless otherwise noted, the reaction was carried out with 1a (0.2 mmol), additive (0.02 mmol) in solvent (2.0 mL) in the presence of W(CO)6
(0.04 mmol).
b
Isolated yield.
In the absence of W(CO)6.
c

T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
Table 3
565
O
Formal Cope rearrangement of 5-siloxy-1,2,5-triene 1 using a catalytic
amount of W(CO)6 in toluenea
path A
with H2O
Ph
Entry
1
Substrate
Product
Yield/%
68a
TESO
TESO
W(CO)6
2a
TESO
OTES
hν
Ph
W(CO)5
Ph
OTES
path B
Ph
Ph
Me
Ph
1a
B
without
H2O
3b
Ph
1b
3a
Scheme 2.
2
61a
TESO
TESO
OTES
1a by W(CO)5 is essential for this transformation. Use
of toluene as a solvent allowed the reaction time to be
greatly diminished from 1 day to 2 h (entry 3). Further-
more, the addition of an amine (0.1 equiv) suppressed the
formation of minor unidentified products, and in particu-
lar, the use of DABCO as a less sterically demanding amine
gave the product 3a in 90% yield as a sole isolable product
(entry 4).
This novel rearrangement reaction is thought to pro-
ceed as shown in Scheme 2. Treatment of 5-siloxy-1,2,5-tri-
ene 1a with W(CO)6 under photoirradiation would form
the same cyclohexenyl tungsten species B as already
described in the mechanism of the formation of the 6-endo
cyclized product (Scheme 1). In the presence of H2O, the
protonation of the carbon–tungsten bond occurs to give
the 6-endo-cyclized product 2a (path A). On the contrary,
in the absence of H2O, electron-donation from W(CO)5
anion into the silyloxonium moiety induces the carbon–
carbon bond cleavage with the liberation of neutral
W(CO)5 species to give the formal Cope rearrangement
product 3a (path B).
Other examples of the W(CO)5(L)-catalyzed formal
Cope rearrangement of 5-siloxy-1,2,5-trienes under these
optimized conditions are listed in Table 3. The reaction
of 5-siloxy-1,2,5-trienes 1b–d containing either a tri-substi-
tuted silyl enol ether moiety or a trisubstituted allene
moiety afforded the corresponding products 3b–d in good
yield (entries 1–3). In this formal Cope rearrangement, it
is interesting to note that the reaction of 1d, which gave
the cyclized product 2d in low yield due to the hydrolysis
of the silyl enol ether moiety of the starting material, gave
the rearranged product in high yield. In the case of sub-
strate 1e containing both of these tri-substitution moieties,
the reaction gave the product 3e in moderate yield as a 1:1
mixture of syn and anti isomers (entry 4), while the reaction
in the presence of H2O gave the cyclized product 2e in good
yield stereoselectively (Table 1, entry 4). It is likely that the
epimerization occurred at the cyclohexenyl tungsten species
B and/or C by DABCO (Scheme 3). The reaction of TBS
enol ether 1h gave the corresponding product 3h in excel-
lent yield (entry 5).
3c
1c
1d
1e
3
86a
OTES
Ph
Ph
Ph
3d
4
47c,d
TESO
OTES
OTBS
Ph
3e
5
99b
TBSO
Ph
3h
1h
a
Conditions: W(CO)6 (20 mol%), DABCO (0.1 equiv), toluene (0.1 M),
40 °C, hm.
b
c
DABCO (1.1 equiv) was added.
A 1.0 M toluene solution was used.
syn:anti = 1:1.
d
purpose of preparing large-membered cyclic alkynes [11].
The reaction of cyclohexane derivative 1f did not proceed
well under the optimum reaction conditions, and only
deprotonation product 5 was obtained (Eq. (3)). Probably
the ring-expanded product 4 with an enyne moiety in 10-
membered carbocycle would suffer from ring strain, and
only deprotonation occurred by the added base. In con-
trast, when cyclooctane derivative 1g was irradiated in
the presence of W(CO)6 (100 mol %) and DABCO
(0.1 equiv) in toluene, the reaction proceeded as expected
to give the ring-expanded 12-membered cyclic product 6
We next examined a ring-expansion reaction by formal
Cope rearrangement of cyclic 5-siloxy-1,2,5-trienes for the

566
T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
4. Experiment
TESO
Condition A
TESO
or
4.1. General
Condition B
Ph
Ph
All operations were performed under an argon atmo-
1
sphere. H and 13C NMR spectra were recorded on a Bru-
W(CO)
5
A (η2-complex)
ker DRX500, a JEOL AL-400, or a JEOL Lambda-400
spectrometer using CHCl3 (1H, d = 7.24), C6H6 (1H,
d = 7.15) and CDCl3 (13C, d = 77.0) as internal standards.
IR spectra were recorded on a JASCO FT/IR-460 plus
spectrometer. Photochemical reactions were performed
with an USHIO INC. super high-pressure mercury lamp.
Flash column chromatography was conducted on silica
gel (Kanto 60N) and preparative thin-layer chromatogra-
phy (PTLC) was carried out on silica gel (Wakogel B-
5F). Tetrahydrofuran was freshly distilled from sodium
benzophenone ketyl, and all other solvents were distilled
according to the standard procedures and stored over
molecular sieves or KOH. W(CO)6 was purchased from
Soekawa Chemical Co., Ltd. and used without further
purification.
1e
TESO
O
H O
2
H
Ph
W(CO)
Ph
5
2e 71%
B (cyclohexenyl tungsten species)
DABCO
DABCO
TESO
OTES
DABCO
H
Ph
Ph
W(CO)
Experimental procedures for the preparation of 5-siloxy-
1,2,5-trienes were described in the previous communica-
tions [5f,5g].
3e 47%
(syn:anti=1:1)
5
C (cyclohexenyl tungsten species)
Scheme 3.
4.2. General procedure for 6-endo-selective cyclization of
5-siloxy-1,2,5-triene 1
in 53% yield as an 86:14 mixture of E and Z isomers [12]
together with 26% yield of deprotonation product 7 (Eq.
(4)) [13].
To a degassed THF (0.2 mL) solution of 5-siloxy-1,2,5-
triene
1 (0.2 mmol) was added W(CO)6 (14.1 mg,
0.04 mmol) and H2O (10.8 lL, 0.6 mmol) at room temper-
ature. The mixture was irradiated using high-pressure
250 W mercury lamp at ambient temperature (rt ꢀ 40 °C)
until the starting material disappeared, and then the result-
ing mixture was concentrated under reduced pressure. The
residue was purified by preparative thin-layer chromatog-
raphy (hexane:ethyl acetate = 10:1) to give 6-endo-cyclized
product, cyclohex-3-en-1-one 2, as a colorless oil.
TBSO
100 mol% W(CO)6
1.1 equiv DABCO
OTBS
OTBS
ð3Þ
hν, toluene, 40˚C
1f
4
0%
5
63%
OTES
OTES
TESO
100 mol% W(CO)6
0.1 equiv DABCO
hν, toluene, 40˚C
4.2.1. 2,2-Dimethyl-3-phenylcyclohex-3-en-1-one (2a)
Yield 68% (20 mol% WCO6). IR (neat): 3022, 2971,
1g
6 53%
7 26%
1
1713, 1463 cmꢁ1; H NMR (CDCl3) (400 MHz): d = 1.17
(86:14)
(6H, s), 2.48–2.55 (2H, m), 2.62–2.67 (2H, m), 5.64 (1H,
t, J = 4.1 Hz), 7.11–7.16 (2H, m), 7.25–7.31 (3H, m); 13C
NMR (CDCl3) (100 MHz): d = 24.8, 25.3, 35.6, 47.9,
125.1, 126.8, 127.6, 129.2, 140.9, 146.8, 214.6. Anal. Calc.
for C14H16O: C, 83.96; H, 8.05. Found: C, 83.70; H, 8.10%.
ð4Þ
3. Conclusion
We have developed a novel 6-endo-selective cyclization
of allenyl silyl enol ethers using a catalytic amount of
W(CO)6. Two types of synthetically useful compounds,
that is, 6-endo-cyclized products or the formal Cope
rearrangement products, are prepared selectively from the
same starting materials via the same intermediates simply
by changing the reaction conditions. It is also noted that
electrophilic activation of the allene moiety is effectively
achieved by coordination of W(CO)5, allowing intramolec-
ular attack by neutral carbon nucleophiles efficiently.
4.2.2. 2,2,6-Trimethyl-3-phenylcyclohex-3-en-1-one (2b)
Yield 77% (20 mol% W(CO)6). IR (neat): 3021, 2971,
2929, 1712, 1462 cmꢁ1 1H NMR (CDCl3) (400 MHz):
;
d = 1.07 (3H, s), 1.13 (3H, d, J = 6.3 Hz), 1.25 (3H, s),
2.14 (1H, ddd, J = 17.0, 11.9, 2.0 Hz), 2.59 (1H, dt,
J = 17.0, 6.0 Hz), 2.93–3.05 (1H, m), 5.59 (1H, dd,
J = 6.0, 2.0 Hz), 7.10–7.17 (2H, m), 7.22–7.35 (3H, m);
13C NMR (CDCl3) (100 MHz): d = 14.4, 22.7, 27.7, 34.2,
38.8, 48.3, 124.3, 126.7, 127.5, 129.3, 140.8, 146.8, 215.7.

T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
567
Anal. Calc. for C15H18O: C, 84.07; H, 8.47. Found: C,
84.04; H, 8.68%.
4.3.1. 1-Phenyl-6-methyl-5-triethylsiloxyhept-5-en-1-yne
(3a)
Yield 90% (20 mol% W(CO)6). IR (neat): 2955, 2914,
1680, 1258, 1198 cmꢁ1 1H NMR (CDCl3) (400 MHz):
d = 0.67 (6H, q, J = 8.0 Hz), 0.98 (9H, t, J = 8.0 Hz),
1.62 (3H, s), 1.65 (3H, s), 2.41–2.44 (2H, m), 2.52–2.56
(2H, m), 7.23–7.28 (3H, m), 7.35–7.39 (2H, m); 13C
NMR (CDCl3) (100 MHz): d = 5.6, 6.9, 17.9, 18.0, 18.9,
32.1, 80.6, 90.0, 110.8, 124.0, 127.4, 128.1, 131.4, 142.7.
Anal. Calc. for C20H30OSi: C, 76.37; H, 9.61. Found: C,
76.17, H, 9.87%.
4.2.3. 2,2,3,6-Tetramethylcyclohex-3-en-1-one (2c)
Yield 71% (20 mol% WCO6). IR (neat): 2971, 2931,
;
1
1712, 1450 cmꢁ1; H NMR (CDCl3) (400 MHz): d = 1.02
(3H, d, J = 6.0 Hz), 1.12 (3H, s), 1.18 (3H, s), 1.68–1.69
(3H, m), 1.90–1.99 (1H, m), 2.35–2.43 (1H, m), 2.74–2.83
(1H, m), 5.45 (1H, d, J = 6.0 Hz); 13C NMR (CDCl3)
(100 MHz): d = 14.3, 18.3, 21.9, 26.7, 33.8, 38.8, 48.0,
120.4, 140.6, 216.4; HRMS (EI+) Calcd for C10H16O, M
152.1201. Found for m/z 152.1209.
4.3.2. 4,6-Dimethyl-1-phenyl-5-triethylsiloxy-hept-5-en-1-
yne (3b)
4.2.4. 3-Phenyl-2,2,5,6-tetramethylcyclohex-3-en-1-one (2e)
The stereochemistry was assigned to be cis on the basis
of the measurement of differential NOE spectra. Yield 71%
(20 mol% W(CO)6). IR (neat): 2970, 2931, 1713,
Yield 68% (20 mol% W(CO)6). IR (neat): 2957, 1672,
1
1262, 1189 cmꢁ1; H NMR (CDCl3) (400 MHz): d = 0.72
(6H, q, J = 8.0 Hz), 0.99 (9H, t, J = 8.0 Hz), 1.12 (3H, d,
J = 6.8 Hz), 1.60 (3H, s), 1.66 (3H, s), 2.36 (1H, dd,
J = 8.0, 16.8 Hz), 2.46 (1H, dd, J = 6.8, 16.8 Hz), 2.98
(1H, sext, J = 6.8 Hz), 7.22–7.27 (3H, m), 7.35–7.37 (2H,
m); 13C NMR (CDCl3) (100 MHz): d = 6.1, 7.1, 17.8,
18.9, 19.0, 24.8, 35.0, 81.2, 89.7, 108.4, 124.1, 127.3,
128.1, 131.4, 146.6. Anal. Calc. for C21H32OSi: C, 76.77;
H, 9.82. Found: C, 76.57; H, 10.09%.
1
1460 cmꢁ1; H NMR (CDCl3) (400 MHz): d = 0.86 (3H,
d, J = 7.2 Hz), 1.08 (3H, d, J = 6.8 Hz), 1.08 (3H, s), 1.20
(3H, s), 2.63 (1H, sext, J = 6.8 Hz), 3.20 (1H, quint,
J = 6.8 Hz), 5.70 (1H, d, J = 6.0 Hz), 7.13–7.15 (2H, m),
7.26–7.31 (3H, m); 13C NMR (CDCl3) (100 MHz):
d = 11.6, 15.8, 23.0, 27.2, 37.2, 43.3, 48.4, 126.7, 127.5,
129.4, 131.8, 140.7, 145.3, 215.8; HRMS (EI+) Calcd for
C16H20O, M 228.1514. Found for m/z 228.1493.
4.3.3. 2,4-Dimethyl-3-triethylsiloxyoct-2-en-6-yne (3c)
Yield 61% (20 mol% W(CO)6). IR (neat): 2957, 2917,
4.2.5. Bicyclo[4.4.0]dec-1-en-5-one (2f)
Since 2f has already been prepared [14], NMR spectra
are only presented. Yield 84% (10 mol% W(CO)6). 1H
NMR (CDCl3) (400 MHz): d = 1.10–1.42 (3H, m), 1.45–
1.54 (1H, m), 1.70–2.21 (4H, m), 2.22–2.50 (4H, m),
2.57–2.67 (1H, m), 5.50 (1H, br s); 13C NMR (CDCl3)
(100 MHz): d = 25.3, 25.9, 27.4, 30.1, 34.6, 37.8, 50.2,
118.1, 139.8, 212.9.
2877, 1671, 1261, 1190 cmꢁ1
;
1H NMR (CDCl3)
(400 MHz): d = 0.68 (6H, q, J = 8.0 Hz), 0.96 (9H, t,
J = 8.0 Hz), 1.04 (3H, d, J = 6.8 Hz), 1.56 (3H, s), 1.60
(3H, s), 1.75–1.77 (3H, m), 2.02–2.11 (1H, m), 2.14–2.20
(1H, m), 2.80 (1H, sext, J = 6.8 Hz); 13C NMR (CDCl3)
(100 MHz): d = 3.6, 6.0, 7.1, 17.6, 18.87, 18.89, 24.1,
35.1, 76.1, 78.6, 108.0, 147.0. Anal. Calc. for C16H30OSi:
C, 72.11; H, 11.35. Found: C, 71.84; H, 11.13%.
4.2.6. Bicyclo[6.4.0]dodec-1(8)-en-9-one (2g)
Since 2g has already been prepared [15], NMR spectra
are only presented. Yield 69% (20 mol% W(CO)6). 1H
NMR (CDCl3) (400 MHz): d = 1.35–1.54 (6H, s), 1.61–
1.70 (2H, m), 1.92 (2H, quint, J = 6.4 Hz), 2.33–2.38 (6H,
m), 2.43 (2H, t, J = 6.4 Hz); 13C NMR (CDCl3)
(100 MHz): d = 22.7, 23.2, 26.5, 26.7, 28.7, 29.7, 31.1,
33.9, 37.9, 135.4, 159.7, 198.4.
4.3.4. 3,6-Dimethyl-1-phenyl-5-triethylsiloxyhept-5-en-1-yne
(3d)
Yield 86% (20 mol% W(CO)6). IR (neat): 2958, 1680,
1
1250, 1174 cmꢁ1; H NMR (CDCl3) (400 MHz): d = 0.67
(6H, q, J = 7.6 Hz), 0.98 (9H, t, J = 7.6 Hz), 1.22 (3H, d,
J = 7.2 Hz), 1.64 (3H, s), 1.66 (3H, s), 2.26 (1H, dd,
J = 8.0, 14.0 Hz), 2.47 (1H, dd, J = 6.4, 14.0 Hz), 2.92
(1H, sext, J = 7.2 Hz), 7.21–7.28 (3H, m), 7.33–7.37 (2H,
m); 13C NMR (CDCl3) (100 MHz): d = 5.6, 6.9, 18.0,
19.3, 20.4, 25.0, 39.7, 80.4, 94.7, 111.7, 124.1, 127.3,
128.0, 131.5, 141.9. Anal. Calc. for C21H32OSi: C, 76.77;
H, 9.82. Found: C, 76.50; H, 9.59%.
4.3. General procedure for the formal Cope rearrangement of
5-siloxy-1,2,5-triene (1)
To a degassed toluene (2.0 mL) solution of 5-siloxy-
1,2,5-triene 1 (0.2 mmol) was added W(CO)6 (14.1 mg,
0.04 mmol) and DABCO (2.2 mg, 0.02 mmol) at room tem-
perature. The mixture was irradiated using high-pressure
250 W mercury lamp at ambient temperature (rt ꢀ 40 °C)
until the starting material disappeared, and then the result-
ing mixture was concentrated under reduced pressure. The
residue was purified by preparative thin-layer chromatog-
raphy (hexane) to give the formal Cope rearrangement
product, 2-siloxy-1-en-5-yne 3, as a colorless oil.
4.3.5. 1-Phenyl-5-triethylsiloxy-3,4,6-trimethylhept-5-en-1-
yne (3e)
This compound was obtained as a 1:1 mixture of syn
and anti isomers. 47% yield (20 mol% W(CO)6). IR (neat):
2957, 1672, 1261, 1197 cmꢁ1
;
1H NMR (CDCl3)
(400 MHz): (syn, anti mixture) d = 0.61–0.70 (6.0H, m),
0.90–0.95 (9.0H, m), 0.97 (1.5H, d, J = 6.8 Hz), 1.10
(1.5H, d, J = 6.0 Hz), 1.15 (1.5H, d, J = 6.4 Hz), 1.19

568
T. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 562–568
(c) J.D. Winkler, K.J. Quinn, C.H. MacKinnon, S.D. Hiscock, E.C.
McLaughlin, Org. Lett. 5 (2003) 1805.
(1.5H, d, J = 6.8 Hz), 1.53 (1.5H, s), 1.55 (1.5H, s), 1.56
(1.5H, s), 1.62 (1.5 H, s), 2.52–2.61 (1.5H, m), 2.66–2.73
(0.5H, m), 7.16–7.26 (4H, m), 7.33–7.35 (1H, m); 13C
NMR (CDCl3) (100 MHz): (syn, anti mixture) d = 6.1,
6.2, 7.1, 7.2, 15.4, 17.7, 18.7, 18.8, 19.0, 19.1, 19.4, 19.5,
30.2, 30.3, 40.4, 40.9, 80.8, 81.3, 94.7, 94.8, 108.4, 109.0,
124.1, 124.4, 127.1, 127.3, 128.0, 128.1, 131.3, 131.4,
145.6, 147.0. Anal. Calc. for C22H34OSi: C, 77.13; H,
10.00. Found: C, 77.22; H, 9.82%.
[4] For selected examples of the palladium-catalyzed cyclization of
allenes bearing carbon nucleophiles via p-allyl complexes, see: (a) M.
Ahmar, B. Cazes, J. Gore, Tetrahedron Lett. 26 (1985) 3795;
(b) Y. Yamamoto, M. Al-Masum, N. Asao, J. Am. Chem. Soc. 116
(1994) 6019;
(c) B.M. Trost, V.J. Gerusz, J. Am. Chem. Soc. 117 (1995) 5156;
(d) M. Meguro, S. Kamijo, Y. Yamamoto, Tetrahedron Lett. 37
(1996) 7453;
(e) B.M. Trost, P.-Y. Michellys, V.J. Gerusz, Angew. Chem., Int. Ed.
Engl. 36 (1997) 1750;
(f) B.M. Trost, C. Ja¨kel, B. Plietker, J. Am. Chem. Soc. 125 (2003)
4438;
(g) S. Ma, N. Jiao, Q. Yang, Z. Zheng, J. Org. Chem. 69 (2004) 6463;
(h) B.M. Trost, A.B.C. Simas, B. Plietker, C. Ja¨kel, J. Xie, Chem.
Eur. J. 11 (2005) 7075;
4.3.6. 1-Phenyl-6-methyl-5-(t-butyldimethylsiloxy)hept-5-
en-1-yne (3h)
Yield 99% (20 mol% W(CO)6). IR (neat) 2928, 1680,
1
1257, 1163 cmꢁ1; H NMR (CDCl3) (500 MHz): d = 0.12
(6H, s), 0.95 (9H, s), 1.61 (3H, s), 1.66 (3H, s), 2.40–2.48
(2H, m), 2.50–2.58 (2H, m), 7.21–7.27 (3H, m), 7.35–7.40
(2H, m); 13C NMR (CDCl3) (125 MHz): d = ꢁ3.8, 18.2,
18.5, 18.7, 19.4, 26.3, 32.2, 81.0, 90.4, 111.4, 124.5, 127.9,
128.6, 131.9, 143.1. Anal. Calc. for C20H30OSi: C, 76.37;
H, 9.61. Found: C, 76.08; H, 9.71%.
(i) For Au(I)-catalyzed cyclization reactions of allenylic ester inter-
mediates generated by [3,3]-rearrangement of propargylic esters, see:
L. Zhang, J. Am. Chem. Soc. 127 (2005) 16804;
(j) L. Zhang, S. Wang, J. Am. Chem. Soc. 128 (2006) 1442.
[5] (a) K. Maeyama, N. Iwasawa, J. Am. Chem. Soc. 120 (1998) 1928;
(b) N. Iwasawa, K. Maeyama, H. Kusama, Org. Lett. 3 (2001) 3871;
(c) T. Miura, N. Iwasawa, J. Am. Chem. Soc. 124 (2002) 518;
(d) H. Kusama, H. Yamabe, N. Iwasawa, Org. Lett. 4 (2002) 2569;
(e) N. Iwasawa, T. Miura, K. Kiyota, H. Kusama, K. Lee, P.H. Lee,
Org. Lett. 4 (2002) 4463;
4.3.7. 2-Triethylsiloxycyclododec-1-en-5-yne (6)
This compound was obtained as a 86:14 mixture of geo-
metrical isomers. The geometry was not determined. NMR
data were described for the major product. Yield 53%
(100 mol% W(CO)6). IR (neat): 2917, 1672, 1148, 1005,
(f) T. Miura, K. Kiyota, H. Kusama, K. Lee, H. Kim, S. Kim, P.H.
Lee, N. Iwasawa, Org. Lett. 5 (2003) 1725;
(g) T. Miura, K. Kiyota, H. Kusama, N. Iwasawa, Org. Lett. 7
(2005) 1445.
1
729 cmꢁ1; H NMR (C6D6) (400 MHz): d = 0.60 (6H, q,
[6] A part of this work appeared as preliminary communications, see Ref.
[5f,5g].
J = 8.0 Hz), 0.98 (9H, t, J = 8.0 Hz), 1.37 (2H, quint,
J = 6.4 Hz), 1.44–1.63 (6H, m), 2.03 (2H, t, J = 6.0 Hz),
2.11–2.14 (2H, m), 2.25 (2H, q, J = 6.8 Hz), 2.32–2.36
(2H, m), 4.51 (1H, t, J = 6.8 Hz); 13C NMR (CDCl3)
(100 MHz): d = 5.5, 6.9, 16.8, 17.4, 23.5, 24.5, 25.2, 26.1,
26.3, 36.3, 80.1, 81.8, 110.9, 148.0. Anal. Calc. for
C18H32OSi: C, 73.90; H, 11.03. Found: C, 73.80; H, 10.77%.
[7] When the corresponding TBS enol ether was employed, the reaction
gave the corresponding formal Cope rearrangement product (see the
later part of this paper) as the major product even in the presence of
H2O. This is probably due to the slower rate of hydrolysis of the
silyloxonium intermediate (see Scheme 1, B).
[8] For reviews dealing with of acetylenic or allenic Cope rearrangement,
see: (a) W.D. Huntsman, in: S. Patai (Ed.), The Chemistry of
Ketenes, Allenes and Related Compounds, J. Wiley and Sons, 1980,
pp. 582–643, Part 2;
(b) A. Viola, J.J. Collins, N. Filipp, Tetrahedron 37 (1981) 3765.
[9] For the first example, see: D.K. Black, S.R. Landor, J. Chem. Soc.
(1965) 6784.
[10] (a) For recent examples, see: K.A. Owens, J.A. Berson, J. Am. Chem.
Soc. 112 (1990) 5973;
(b) K.A. Black, S. Wilsey, K.N. Houk, J. Am. Chem. Soc. 120 (1998)
5622;
(c) H. Hopf, J. Wolff, Eur. J. Org. Chem. (2001) 4009.
[11] For example of ring-expansion reaction of thermal allenyl Cope
rearrangement, see: E. Vedejs, A. Cammers-Goodwin, J. Org. Chem.
59 (1994) 7541.
Acknowledgements
This work was supported by Grant-in-Aid for Scientific
Research on Priority Area ‘‘Reaction Control of Dynamic
Complexes’’ from Ministry of Education, Culture, Sports,
Science, and Technology, Japan. T.M. was granted a Re-
search Fellowship of the Japan Society for the Promotion
of Science for Young Scientists.
References
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