Efficient intramolecular Diels-Alder reactions of ester-tethered 1,7,9-decatrienoates catalyzed by bis-aluminated trifluoromethanesulfonamide

Article abstract of DOI:10.1016/j.tet.2004.10.012

Bis-aluminated trifluoromethanesulfonamide generated in situ by mixing TfNH₂ (1 mol) and methylaluminum reagent (2 mol) is an effective catalyst for the IMDA reaction of ester-tethered 1,7,9-decatrienoates. Graphical Abstract

Full text of DOI:10.1016/j.tet.2004.10.012

Tetrahedron 60 (2004) 12239–12247
Efficient intramolecular Diels–Alder reactions of ester-tethered
1,7,9-decatrienoates catalyzed by bis-aluminated
trifluoromethanesulfonamide
*
Akio Saito, Hikaru Yanai and Takeo Taguchi
School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
Received 18 September 2004; revised 5 October 2004; accepted 5 October 2004
Available online 19 October 2004
Abstract—Bis-aluminated trifluoromethanesulfonamide generated in situ by mixing TfNH2 (1 mol) and methylaluminum reagent (2 mol) is
an effective catalyst for the IMDA reaction of ester-tethered 1,7,9-decatrienoates.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
tethered substrates7 or the modification of tether moiety in
the substrates from ester to acetal8 or hydroxamate9 have
been reported, although limitation of substrates is one of the
disadvantages in these reactions. It has been also docu-
mented that Lewis acid mediated reaction, which is often
effective for intermolecular versions, does not always work
well in the IMDA reactions of the ester tethered sub-
strates.5d,10
The Diels–Alder reaction is one of the most powerful means
for the stereocontrolled construction of functionalized
cyclohexene frameworks.1 In particular, the intramolecular
Diels–Alder (IMDA) reaction provides an efficient method
for bicyclic and polycyclic compounds and it has been
applied to the synthesis of a variety of complex molecules
including natural products.2,3 In the IMDA reactions, the
reactivity of the substrate and the stereochemical outcome
of the product are strongly influenced by the nature of the
tether linking diene and dienophile parts. For example,
incorporation of an ester linkage as the tether often has an
adverse effect on the IMDA reaction resulting in requiring
higher reaction temperature and longer reaction time but
low yields of the cyclized products or in some cases even
failure to obtain any cyclized products.2–4 Such a reduced
reactivity of ester tethered substrates, in particular 1,6,8-
nona- and 1,7,9-decatriene systems, is attributed to a
preference for the transoid geometry due primarily to
dipole repulsion between carbonyl-oxygen and ethereal
oxygen and a relatively high rotational barrier to cisoid
form, in which the diene and the dienophile are in close
proximity (Scheme 1).5 Furthermore, poor overlap of the
non-bonding electrons of the ethereal oxygen and carbonyl
group in the transition state is considered to be a major
factor responsible for this low reactivity.4a,6 Towards to
these issues, the use of polar solvent in the case of ester-
Scheme 1.
CF3SO2NH2 C2MeAILn/TfNðAILnÞ2 C2CH4
(1)
Recently we reported that the IMDA reaction of 1,7,9-
decatrienoates can be efficiently promoted by a bidentate
Lewis acid, in particular bis-aluminated trifluoromethane-
sulfonamide generated in situ by mixing TfNH2 (1 mol) and
methylaluminum reagent (2 mol) (Eq. 1).11 We assumed
that coordination of both oxygen atoms of the ester group to
a bidentate Lewis acid (possibly in equilibrium with other
complex forms such as a double coordination form toward
carbonyl oxygen) would control the geometry of ester
moiety to be a cisoid structure and would strongly enhance
the reactivity of the dienophile as compared with the use of a
monodentate Lewis acid (Scheme 1).12 Further study using
a variety type of substrates revealed the efficiency of these
Keywords: Bis-aluminated trifluoromethanesulfonamide; Intramolecular
Diels–Alder reaction; 1,7,9-Decatrienoate; Bidentate Lewis acid.
* Corresponding author. Tel.: C81 426 76 3257; fax: C81 426 76 3257;
e-mail: taguchi@ps.toyaku.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.10.012

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A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
Scheme 2.
bidentate Lewis acids in the IMDA reaction of ester tethered
substrates. In this paper, we report a detail of the IMDA
reactions promoted by bis-aluminated trifluoromethane-
sulfonamide, which is applicable to 1,7,9-decatrienoate
derivatives having various substituent patterns (Scheme 2).
presence of 1.1 equiv of TfN[Al(Me)Cl]2, the reactions of
1a–1d proceeded at 0 8C or room temperature within a short
period (1–8 h) to give the cycloadducts 2a–2d in good
yields (entries 1, 2, 4, 6 and 7). Even on using a catalytic
amount of Lewis acid (0.3 equiv) 2a, 2b and 2d were
obtained in good yields, although higher reaction tempera-
ture and longer reaction time were required (entries 3, 5 and
8). In all cases, each adduct 2a–2d was obtained as a single
cis-fused isomer (endo adduct) with illustrated relative
configuration. In particular, the trans relationship
between the Me group and the hydrogen on the ring-
junction in 2b indicated that the reaction proceeds via
2. Results and discussion
The IMDA reactions of 1,7,9-decatrienoates 1a–1e cata-
lyzed by TfN[Al(Me)Cl]2 are shown in Table 1. In the
Table 1. TfN[Al(Me)Cl]2 catalyzed IMDA reaction of 1,7,9-decatrienoates 1a–1e
Entry
1
Lewis acid
(equiv)
Solvent
Temp. (8C)
Time (h)
2
Yield (%)a
1
2
3
1a
1a
1a
1.1
1.1
0.3
CH2Cl2
Toluene
ClCH2CH2Cl 50
rt
0
1
2
6
2a
2a
2a
88
90
85
4
5
1b
1b
1.1
0.3
CH2Cl2 rt
ClCH2CH2Cl 50
1
7
2b
2b
91
79
6
1c
1.1
CH2Cl2
CH2Cl2
0
8
2c
78
7
8
1d
1d
1.1
0.3
rt
2
24
2d
2d
82
77
ClCH2CH2Cl 80
9
10
1e
1e
1.1
0.3
ClCH2CH2Cl 80
ClCH2CH2Cl 80
5
52
2e
2e
78
71
a Isolated yield.

A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
12241
adducts 2f in 68% yield as an endo/exo mixture in a ratio of
10:1 (Scheme 3).
The bidentate Lewis acid also effected the Diels–Alder
reaction of methacrylate derivative 1g having a chiral center
at 5-position to give a mixture of the cycloadducts 2g in
74% yield, which consisted of two endo isomers (trans/
cisZ2.3:1) and one exo isomer in a ratio of endo/exoZ14:1
(Scheme 4). The major isomer 2g-endo-trans has a trans
relationship between the Me group originally attached on
the chiral center and the hydrogen on ring-junction. As in
the case of the acrylates 1a–1e shown in Table 1, this major
isomer 2g-endo-trans would be derived through endo-
boatlike transition state B, in which a-Me substituent has a
psuedo–flagpole interaction with axial hydrogen attached on
the ethereal carbon. Therefore, endo-chairlike transition
state C would be competitively contribute for the formation
of the minor cis-isomer 2g-endo-cis.6b Compared to an
excellent chiral induction in the case of acrylate 1b derived
from the same secondary alcohol (see Table 1, entry 4),
introduction of a-methyl group leading to the methacrylate
Scheme 3.
endo-boatlike transition state A. This conformational
preference is in accord with the previous results in the
thermal IMDA reactions of 1,7,9-decatrien-3-ones2b and
1,7,9-decatrienoates.6,13
In
the
presence
of
TfN[Al(Me)Cl]2, reaction of b-substituted acrylate 1e also
proceeded smoothly at 80 8C to give 2e in good yield with
an excellent endo selectivity (entries 9, 10).
As far as we know, no successful example of the
IMDA reaction of 1,7,9-decatriene systems tethered by an
a-substituted a,b-unsaturated ester moiety such as 1f, 1g has
been reported. Treatment of methacrylate derivative 1f with
1.1 equiv of TfN[Al(Me)Cl]2 at 50 8C gave the cyclo-
structure 1g caused
stereoselectivity.
a
remarkable decrease in
Scheme 4.
Table 2. IMDA reaction of 6-substituted 1,7,9-decatrienoates1h–1j
Entry
1
Lewis acid
Temp. (8C)
Time (h)
2
Yield (%)a
cis/transb
7.3:1
5.2:1
cis only
cis only
1:7.2
1
1h
1h
1i
1i
1j
1j
TfN[Al(Me)Cl]2 rt
—
TfN(AlMe2)2
—
TfN(AlMe2)2
—
7
12
5
12
3
2h
2h
2i
2i
2j
2j
83
49
70
64
74
74
2c
3
140
0
140
0
4c
5
6c
140
12
3.9:1
a Isolated yield.
b Based on isolated yield.
c Solvent: 1,2-dichlorobenzene.

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A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
adduct 2j with cis favorable manner (74% yield, cis/transZ
3.9:1, entry 6), while on using TfN(AlMe2)2 as a catalyst the
reaction proceeded at 0 8C to give the same adduct 2j in
74% yield, but the trans isomer was a major product (cis/
transZ1:7.2, entry 5).
Observed cis/trans selectivity under the thermal or Lewis
acid mediated conditions could be explained by considering
the transition state shown in Scheme 5. In the case of
thermal reaction of 1j, the major isomer 2j-cis would be
derived via endo-boatlike transition state model D, in which
sterically bulky TBSO substituent occupies a psuedo-
equatorial position. Such a preferable conformation was
also proposed in the IMDA reaction of N-sulfinylcarbamate
derivatives having benzyloxy group at the similar position
in the diene parts.14 Likewise, the observed cis-selectivities
of methyl-substituted substrate 1h and silyloxymthyl-
substituted substrate 1i under both thermal and Lewis acid
mediated conditions are also explained by this model D, in
which methyl and siloxymethyl group, instead of TBSO
group, occupy a psuedo-equatorial position. On the other
hand, the Lewis acid mediated reaction of siloxy-substituted
substract 1j would proceed via endo-boatlike transition state
E, in which the bidentate Leiws acid TfN(AlMe2)2
coordinated by oxygens of ester moiety possibly has an
interaction with the oxygen atom of TBSO substituent when
it occupies a psuedo-axial position.15,16
Scheme 5.
Next, we examined the substituent effect on the chiral
induction during the IMDA reaction using the substrates
having a substituent at 6-position. As the substrates, 1,7,9-
decatrienoates having methyl 1h, t-butyldimethylsiloxy-
methyl 1i and t-butyldimethylsiloxy 1j were used and the
reactions were conducted under the thermal conditions or in
the presence of the present bidentate Lewis acid. Results are
shown in Table 2. In the presence of TfN[Al(Me)Cl]2, the
IMDA reaction of Me-substituted substrate 1h proceeded at
room temperature to give the endo adduct 2h in 83% yield
(entry 1). The major isomer of 2h has cis configuration
between the methyl group and the hydrogen on ring-
junction (cis/transZ7.3:1). Under the thermal conditions,
upon heating 140 8C for 12 h, the IMDA reaction of 1h
proceeded in endo selective manner to give the adduct 2h in
49% yield with preferable formation of cis isomer (cis/
transZ5.2:1, entry 2). A complete endo and cis selectivity
was found in the reaction of siloxymethyl-substituted
substrate 1i under the thermal conditions (140 8C, 12 h)
and TfN(AlMe2)2 catalyzed conditions (0 8C, 5 h) giving
rise to the product 2i as a single isomer (entries 3, 4). On the
other hand, in the case of siloxy derivative 1j the
stereochemical outcome (cis/trans selectivity) was found
different depending on the reaction conditions. Thus, the
thermal reaction (140 8C, 12 h) of 1j provided the endo
It is noted that a significant oxophilic nature of the bis-
aluminated triflic amide brought about some limitation of
the substrate structure. For example, the TfN(AlMe2)2
catalyzed reaction of the benzyloxy derivative 1k instead of
siloxy derivative 1j provided the IMDA product 2k in low
yield (17%) due to the facile cleavage of allylic ether moiety
to give benzyl alcohol in 39% yield, even though the starting
material 1k was recovered in 20% yield at the same time
(Scheme 6). Similar problem was also observed in allylic
ester type substrate, 1,6,8-nonatrienoate derivative 3
(Scheme 7). Thus, either TfN[Al(Me)Cl]2 or TfN(AlMe2)2
did not effect the IMDA reaction of 3 due mainly to the
cleavage of ester part. Therefore, it is difficult to prepare
oxabicyclo[4.3.0]nonene derivative 4 from 2,4-alkadienyl
acrylate 3 under the present Lewis acid catalyzed
Scheme 6.
Scheme 7.

A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
12243
(2.0 mL, 14.3 mmol) in CH2Cl2 (15 mL) was stirred for 2 h
at 0 8C and then for 2 h at room temperature, the reaction
mixture was extracted with ether after addition of H2O. The
organic layer was washed with brine, dried over MgSO4,
and purified by silica gel column chromatography
1
(hexane/Et2OZ50:1) to give 1a (1.35 g, 87% yield). H
NMR spectrum of 1a was identical with that reported in the
literature.4b
By a similar procedure for the preparation of 1a, the
substrates 1f, 1h were prepared from the corresponding
dienyl alcohol and acid chloride.
The physical data of 1b, 1d, 1e, 1g were reported
Scheme 8.
previously.11
4.2.1. (3E)-3,5-Hexadienyl 2-methylacrylate (1f). 76%
yield. Colorless oil. IR (neat) n cmK1; 1720. 1H NMR
(400 MHz, CDCl3) d; 1.93 (3H, s), 2.46 (2H, dt, JZ6.7,
6.7 Hz), 4.19 (2H, t, JZ6.7 Hz), 5.01 (1H, d, JZ10.2 Hz),
5.13 (1H, d, JZ16.8 Hz), 5.54 (1H, bs), 5.68 (1H, dt, JZ
15.1, 6.7 Hz), 6.09 (1H, bs), 6.13 (1H, dd, JZ15.1,
10.2 Hz), 6.31 (1H, ddd, JZ16.8, 10.2, 10.2 Hz). 13C
NMR (100.6 MHz, CDCl3) d; 18.3, 31.9, 63.7, 116.0, 125.4,
129.7, 133.4, 136.4, 136.8, 167.4. EI-MS m/z: 166 (MC).
Anal. Calcd for C10H14O2: C, 72.26; H, 8.49. Found: C,
71.95; H, 8.45.
conditions. Oxabicyclo[4.3.0]nonene derivative 4 could be
prepared through the ring contraction of lactone moiety of
the cycloadduct 2j (Scheme 8).17 As shown in Scheme 8,
desilylation by tetrabutylammonium fluoride (TBAF) led to
the formation of thermodynamically stable 5-membered
lactone 4a from 2i-cis and 4b from 2i-trans, respectively.
3. Conclusion
We have shown that the IMDA reaction of 1,7,9-
decatrienoate derivatives having ester moiety as the tether
are efficiently catalyzed by bis-aluminated trifluoro-
methanesulfonamide, TfN[Al(Me)Cl]2 or TfN(AlMe2)2. In
place of the IMDA reactions of 1,6,8-nonatriene systems,
we have developed two-step procedure, which involves the
IMDA reactions of 1,7,9-decatrienoate having a silyloxy
group at 6 position followed by ring contraction of lactone
function of the cycloadduct. Further studies on the structure
of the complex forms, and application to the synthesis of
natural products are under way.
4.2.2. (2R,3E,5E)-2-Methyl-3,5-heptadienyl acrylate
1
(1h). 79% yield. Colorless oil. IR (neat) n cmK1; 1730. H
NMR (400 MHz, CDCl3) d; 1.06 (3H, d, JZ6.8 Hz), 1.73
(3H, d, JZ7.5 Hz), 2.57 (1H, m), 3.99 (1H, dd, JZ10.7,
6.8 Hz), 4.06 (1H, dd, JZ10.7, 6.7 Hz), 5.41–5.52 (1H, m),
5.58–5.69 (1H, m), 5.81 (1H, dd, JZ10.4, 1.4 Hz), 5.96–
6.10 (1H, m), 6.12 (1H, dd, JZ17.3, 1.4 Hz), 6.39 (1H, dd,
JZ17.3, 1.4 Hz). 13C NMR (100.6 MHz, CDCl3) d; 17.0,
18.1, 36.1, 68.7, 128.4, 128.6, 13.6, 130.8, 131.5, 132.5,
166.5. EI-MS m/z: 180 (MC). Anal. Calcd for C11H16O2: C,
73.30; H, 8.95. Found: C, 73.36; H, 8.73.
4. Experimental
4.1. General
4.2.3. (3E)-5-Phenyl-3,5-hexadienyl acrylate (1c). After a
suspension of methyltriphenylphosphonium bromide
(14.3 g, 40.0 mmol) in ether (80 mL) was treated with
n-BuLi (14.8 mL, 2.44 M in hexane solution) for 3 h at
room temparature, (E)-5-{tert-butyl(dimethyl)silyloxy}-1-
phenyl-2-penten-1-one18 (6.4 g, 22.0 mmol) in ether
(20 mL) was added at 0 8C. The reaction mixture was
stirred for 3 h at room temperture. After usual work-up
(extracetd with AcOEt, dried over MgSO4, and concentrated
under reduced pressure), a solution of the residue in THF
(4.0 mL) was treated with tetrabutylammonium fluoride
(3.0 mL, 1.0 M THF solution) at 0 8C for 8 h. The usual
workup and the subsequent purification by column
chromatography on silica gel (hexane/AcOEtZ9:1) gave
(3E)-5-phenyl-3,5-hexadien-1-ol (316 mg, 91% yield) as
colorless oil. IR (neat) n cmK1; 3335. 1H NMR (400 MHz,
CDCl3) d; 2.40 (2H, dt, JZ7.2, 6.4 Hz), 3.67 (1H, t, JZ
6.4 Hz), 5.11 (1H, bs), 5.23 (1H, bs), 5.63 (1H, dt, JZ15.7,
7.2 Hz), 6.42 (1H, d, JZ15.7 Hz), 7.28–7.37 (5H, m). 13C
NMR (100.6 MHz, CDCl3) d; 36.2, 61.9, 115.7, 127.4,
128.1, 128.2, 129.6, 134.3, 140.3, 147.7. ESI-MS m/z: 175
(MCCH). HRMS calcd for C12H15O: 175.123. Found:
175.1114.
Trifluoromethanesulfonamide, trimethylaluminum (1.0 M
in hexane) and dimethylaluminum chloride (1.0 M in
hexane) are available commercially. All reactions were
conducted under an argon atmosphere. H and 13C NMR
1
spectra were measured at 400 and 100 MHz in CDCl3, and
the chemical shifts are given in ppm using CHCl3
(7.26 ppm) in CDCl3 for 1H NMR and CDCl3
(77.01 ppm) for 13C NMR as internal standard, respectively.
Mass spectra and HRMS were recorded by EI or ESI
methods. Column chromatography was performed on silica
gel (70–230 mesh). Medium-pressure liquid chromato-
graphy (MPLC) was performed on a 30 cm!2.2 cm i.d.
prepacked column (silica gel, 50 mm) with a UV or RI
detector.
4.2. General procedure for the preparation of 1,7,9-
decatrienoates 1: (3E)-3,5-hexadienyl acrylate (1a)
After a mixture of 3,5-hexadien-1-ol (1 g, 10.2 mmol),
acryloyl chloride (1.0 mL, 12.4 mmol) and triethylamine

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A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
After a mixture of the above dienyl alcohol (228 mg,
1.0 mmol), acryloyl chloride (0.22 mL, 1.1 mmol) and
triethylamine (0.18 mL, 1.3 mmol) in CH2Cl2 (2.0 mL)
was stirred for 5 h at K78 8C, usual work-up followed by
the purification by silica gel column chromatography
(hexane/Et2OZ50:1) gave 1c (155 mg, 68% yield) as
colorless oil. IR (neat) n cmK1; 1725. 1H NMR
(400 MHz, CDCl3) d; 2.38–2.55 (2H, m), 4.22 (1H, t, JZ
6.8 Hz), 5.12 (1H, bs), 5.22 (1H, bs), 5.54–5.69 (1H, m),
5.79 (1H, d, JZ10.4 Hz), 6.12 (1H, dd, JZ17.4, 10.4 Hz),
6.31–6.45 (2H, m), 7.13–7.47 (5H, m). 13C NMR
(100.6 MHz, CDCl3) d; 32.1, 63.6, 115.6, 127.4, 128.1,
128.2, 128.5, 128.8, 130.6, 134.0, 140.2, 147.7, 166.1. ESI-
MS m/z: 229 (MCCH). HRMS calcd for C15H17O2:
229.1229. Found: 229.1228.
JZ10.1 Hz), 5.14 (1H, bd, JZ16.6 Hz), 5.62 (1H, dd, JZ
15.3, 8.2 Hz), 5.81 (1H, dd, JZ10.4, 1.3 Hz), 6.11 (1H, dd,
JZ17.3, 10.4 Hz), 6.15 (1H, dd, JZ15.3, 10.3 Hz), 6.30
(1H, ddd, JZ16.6, 10.3, 10.1 Hz), 6.38 (1H, dd, JZ17.3,
1.3 Hz). 13C NMR (100.6 MHz, CDCl3) d; K5.5, 18.2,
25.8, 44.2, 63.1, 64.3, 116.4, 128.5, 130.5, 131.6, 133.3,
136.9, 166.1. ESI-MS m/z: 297 (MCCH). HRMS calcd
for C16H29O3Si: 297.1886, Found: 297.1870. Anal.
Calcd for C16H28O3Si: C, 64.82; H, 9.52. Found: C,
64.67; H, 9.48.
4.2.5. (2R*,3E,5E)-2-{[tert-Butyl(dimethyl)silyl]oxy}-3,5-
heptadienyl acrylate (1j). To the Grignard reagent
prepared from Mg (432 mg, 18.0 mmol) and chloromethyl-
isopropyloxydimethylchlorosilane (3.0 mL, 18.0 mmol) in
THF (12.5 mL),20 sorbic aldehyde (1.1 mL, 10.0 mmol) in
THF (10 mL) was added at 0 8C. After being stirred for 2 h
at 0 8C, the reaction mixture was quenched by saturated
NH4Cl and filitered through celite pad. After the filitate was
extracted with ether, the organic layer was washed with
brine, dried over MgSO4, and evapolated. A mixture of the
residue, H2O2 (9.0 mL) and NaHCO3 (840 mg, 10.0 mmol)
in THF–MeOH (1:1, 30 mL) was refluxed overnight, and
then evaporated under reduced pressure. Extractive work-up
followed by evaporation gave the crude mixture of 3,5-
heptadiene-1,2-diol, which was treated with diisopropyl-
ethylamine (2.1 mL, 12.0 mmol) and acrylory chloride
(0.89 mL, 11.0 mmol) in THF (20 mL) for 5 h at K78 8C.
Usual work-up and purification by column chromatography
on silica gel (hexane/AcOEtZ6:1) provided (2R*,3E,5E)-2-
hydroxy-3,5-hexadienyl acrylate (658 mg, 35% yield over 3
4.2.4. (2R*,3E)-2-({[tert-Butyl(dimethyl)silyl]oxy}-
methyl)-3,5-hexadienyl acrylate (1i). To a solution of
LDA (11.0 mL, 1.0 M in THF–hexane solution) and HMPA
(1.8 mL), ethyl sorbate (1.50 mL, 10.0 mmol) in THF
(5.0 mL) was added over 10 min at K78 8C. After being
stirred for 2 h at K78 8C, the reaction mixture was treated
with ethyl chloroformate (4.8 mL, 30.0 mmol) for 12 h at
the same temperature. Usual work-up (Et2O for extraction)
followed by the purification by silica gel column chroma-
tography (hexane/etherZ25:1) gave diethyl 2-[(1E)-1,3-
1
butadienyl]malonate (2.0 g, 93% yield) as colorless oil. H
NMR spectrum of this compound was identifical with that
reported in the literature.19 Diethyl 2-[(1E)-1,3-butadienyl]-
malonate (1.6 g, 7.5 mmol) in ether (5 mL) was added to a
solution of LiAlH4 (0.57 g, 15.0 mmol) in ether (10 mL) at
0 8C. After being stirred for 6 h at 0 8C and then usual work-
up, the residue in THF (5 mL) was added to a suspension of
NaH (0.3 g, 60% activity, 7.5 mmol) in THF (15 mL) at
0 8C. After being stirred for 30 min at room temperature, the
reaction mixture was treated with tert-butyldimethylchloro-
silane (1.13 g, 7.5 mmol) for 2 h at room temperature. The
reaction mixture was quenched by H2O and then extracted
with AcOEt. The organic layer was washed with brine, dried
over MgSO4, and purified by silica gel column chromato-
graphy (hexane/AcOEtZ10:1) to give (2R*,3E)-2-({[tert-
butyl(dimethyl)silyl]oxy}methyl)-3,5-hexadien-1-ol (1.1 g,
1
steps) as colorless oil. IR (neat) n cmK1; 1726, 3446. H
NMR (400 MHz, CDCl3) d; 1.76 (3H, d, JZ6.6 Hz), 4.09
(1H, dd, JZ11.4, 7.6 Hz), 4.25 (1H, dd, JZ11.4, 3.5 Hz),
4.39–4.48 (1H, m), 5.54 (1H, dd, JZ15.3, 6.5 Hz), 5.74
(1H, dq, JZ14.9, 6.6 Hz), 5.86 (1H, dd, JZ10.4, 1.3 Hz),
6.04 (1H, dd, JZ14.9, 10.5 Hz), 6.15 (1H, dd, JZ17.3,
10.4 Hz), 6.30 (1H, dd, JZ15.3, 10.5 Hz), 6.43 (1H, dd, JZ
17.3, 1.3 Hz). 13C NMR (100.6 MHz, CDCl3) d; 18.1, 68.1,
70.6, 127.5, 128.0, 130.5, 131.1, 131.4, 133.0, 166.2. ESI-
MS m/z: 205 (MCCNa). HRMS: Calcd for C10H14O3Na:
205.0841. Found: 205.0837.
1
60% yield) as colorless oil. IR (neat) n cmK1; 3375. H
NMR (400 MHz, CDCl3) d; 0.07 (6H, s), 0.90 (9H, s), 2.50–
2.58 (2H, m), 3.64–3.81 (4H, m), 5.04 (1H, bd, JZ9.9 Hz),
5.35 (1H, bd, JZ16.7 Hz), 5.55 (1H, dd, JZ15.3, 8.2 Hz),
6.16 (1H, dd, JZ15.3, 10.2 Hz), 6.29 (1H, ddd, JZ16.7,
10.2, 9.9 Hz). 13C NMR (100.6 MHz, CDCl3) d; K5.6,
K5.5, 18.2, 25.8, 46.4, 65.7, 66.1, 116.5, 131.4, 133.3,
136.8. ESI-MS m/z: 243 (MCCH). HRMS calcd for
C13H27O2Si: 243.1780, Found: 243.1785. Anal. Calcd
for C13H26O2Si: C, 64.41; H, 10.81. Found: C, 64.42; H,
10.82.
After a mixature of the above alcohol (660 mg, 3.6 mmol),
diisopropylethylamine (0.70 mL, 4.0 mmol) and tert-butyl-
dimethylsilyl triflate (0.92 mL, 4.0 mmol) in Et2O (7.5 mL)
was stirred for 5 h at K78 8C, extractive work-up and
purification by silica gel column chromatography (hexane/
AcOEtZ50:1) gave 1j (593 mg, 56% yield) as colorless oil.
IR (neat) n cmK1; 1730. 1H NMR (400 MHz, CDCl3) d; 0.04
(3H, s), 0.06 (3H, s), 0.90 (9H, s), 1.75 (3H, d, JZ6.7 Hz),
4.03 (1H, dd, JZ11.0, 7.5 Hz), 4.09 (1H, dd, JZ11.0,
4.4 Hz), 4.36–4.44 (1H, m), 5.49 (1H, dd, JZ15.2, 6.2 Hz),
5.65–5.75 (1H, m), 5.82 (1H, dd, JZ17.3, 10.5 Hz), 5.99–
6.08 (1H, m), 6.14 (1H, dd, JZ17.3, 10.5 Hz), 6.22 (1H, dd,
JZ15.2, 10.5 Hz), 6.41 (1H, dd, JZ17.3, 1.4 Hz). 13C
NMR (100.6 MHz, CDCl3) d; K4.9, K4.6, 18.0, 18.2, 25.7,
68.3, 71.1, 128.4, 129.2, 130.1, 130.7, 130.7, 131.8, 165.9.
ESI-MS m/z: 319 (MCCNa). HRMS: Calcd for C16H29O3-
SiNa: 319.1705, Found: 319.1704. Anal. Calcd for
C16H28O3Si: C, 64.82; H, 9.52. Found: C, 64.68; H, 9.52.
In a similar manner for the preparation of 1a, reaction of the
above dienyl alcohol (486 mg, 2.0 mmol) with acryloyl
chloride (0.18 mL, 2.2 mmol) and triethylamine (0.33 mL,
2.4 mmol), and the subsequent purification by silica gel
column chromatography (hexane/Et2OZ25:1) gave 1i
(498 mg, 84% yield) as colorless oil. IR (neat) n cmK1
;
1730. 1H NMR (400 MHz, CDCl3) d; 0.03 (6H, s), 0.88 (9H,
s), 2.58–2.68 (1H, m), 3.62 (1H, dd, JZ9.9, 6.5 Hz), 3.67
(1H, dd, JZ9.9, 5.2 Hz), 4.18–4.29 (1H, m), 5.03 (1H, bd,

A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
12245
4.3. General procedure of Lewis acid mediated IMDA
reactions of 1,7,9-decatrienoate derivatives: (4aS*,
8aR*)-6-phenyl-3,4,4a,7,8,8a-hexahydro-1H-isochromen-
1-one (2c)
NMR (400 MHz, CDCl3) d; 1.00 (6H, d, JZ6.6 Hz), 1.31–
1.46 (1H, m), 1.68–1.78 (1H, m), 1.84–1.98 (1H, m), 2.09–
2.16 (2H, m), 2.23–2.36 (1H, m), 2.80 (1H, ddd, JZ9.8, 6.1,
3.4 Hz), 3.87 (1H, dd, JZ11.2, 11.2 Hz), 4.24 (1H, dd, JZ
11.2, 4.5 Hz), 5.66–5.68 (2H, bs). 13C NMR (100.6 MHz,
CDCl3) d; 13.4, 21.1, 30.9, 31.8, 33.0, 38.6, 39.9, 125.1,
135.4, 174.5. EI-MS m/z: 180 (MC). HRMS calcd for
C11H17O2: 181.1229, Found: 181.1128. 2h-trans: IR (neat)
n cmK1; 1728. 1H NMR (400 MHz, CDCl3) d; 1.02 (3H, d,
JZ7.2 Hz), 1.03 (3H, d, JZ7.1 Hz), 1.77 (1H, ddd, JZ
14.1, 8.1, 6.3 Hz), 2.07–2.21 (2H, m), 2.23–2.33 (1H, m),
2.58–2.65 (1H, m), 2.79 (1H, ddd, JZ7.9, 7.9, 4.9 Hz), 4.15
(1H, dd, JZ10.9, 3.7 Hz), 4.24 (1H, ddd, JZ10.2, 2.5,
2.5 Hz), 5.53 (1H, ddd, JZ10.2, 2.7, 2.7 Hz). 13C NMR
(100.6 MHz, CDCl3) d; 13.0, 21.4, 29.2, 31.6, 32.4, 36.0,
38.6, 72.6, 123.8, 137.0, 174.0. EI-MS m/z: 180 (MC)
HRMS calcd for C11H17O2: 181.1229, Found: 181.1131.
After a solution of triflic amide (82 mg, 0.55 mmol) in
CH2Cl2 (4.5 mL) was treated with dimethylaluminum
chloride (1.0 M in hexane, 1.1 mL, 1.1 mmol) for 30 min
at room temperature, 1c (114 mg, 0.50 mmol) in CH2Cl2
(2.5 mL) was added at 0 8C. After being stirred for 1 h at
room temperature, the reaction mixture was quenched by
1 M HCl and extracted with ether. The organic layer was
washed with brine and dried over MgSO4. Purification by
column chromatography on silica gel (hexane/AcOEtZ5:1)
gave the product 2c (89.0 mg, 78% yield) as white solid. Mp
1
82–83 8C. IR (neat) n cmK1; 1720. H NMR (400 MHz,
CDCl3) d; 1.79–1.97 (2H, m), 2.11–2.21 (1H, m), 2.35–2.47
(2H, m), 2.52–2.63 (1H, m), 2.88 (1H, ddd, 6.2, 6.2, 3.9H),
2.91–2.98 (1H, m), 4.29–4.36 (2H, m), 5.95 (1H, bs), 7.23–
7.29 (2H, m), 7.30–7.40 (3H, m). 13C NMR (100.6 MHz,
CDCl3) d; 24.1, 24.8, 28.5, 32.5, 40.0, 67.3, 124.8, 125.1,
127.4, 128.4, 139.5, 141.2, 173.4. ESI-MS m/z: 229 (MCC
H). HRMS calcd for C15H17O2: 229.1229, Found: 229.1248.
Anal. Calcd for C15H16O2: C, 78.92; H, 7.06. Found C,
78.88; H, 6.98.
4.3.3. (4R*,4aR*,8aR*)-4-({[tert-Butyl(dimethyl)silyl]-
oxy}methyl)-3,4,4a,7,8,8a-hexahydro-1H-isochromen-1-
one (2i). The reaction of 1i (148 mg, 0.50 mmol) with
TfN(AlMe2)2 (0.55 mmol) and the subsequent purification
by column chromatography on silica gel (hexane/AcOEtZ
5:1) gave the product 2i (103.8 mg, 70% yield). IR (neat) n
1
cmK1; 1732. H NMR (400 MHz, CDCl3) d; 0.06 (6H, s),
0.90 (9H, s), 1.69–1.79 (1H, m), 1.85–1.92 (1H, m), 1.98–
2.07 (2H, m), 2.15–2.31 (1H, m), 2.62–2.70 (1H, m), 2.76–
2.85 (1H, m), 3.66–3.78 (2H, m), 4.18 (1H, dd, JZ11.2,
8.7 Hz), 4.22 (1H, dd, JZ11.2, 4.4 Hz), 5.54 (1H, bd, JZ
10.1 Hz), 5.79–5.85 (1H, m). 13C NMR (100.6 MHz,
CDCl3) d; K5.5, 18.2, 22.0, 22.8, 25.8, 32.9, 36.8, 42.5,
61.8, 68.8, 127.6, 174.2. ESI-MS m/z: 297 (MCCH).
HRMS: Calcd for C16H29O3Si: 297.1886, Found: 297.1884.
Anal. Calcd for C16H28O3Si: C, 64.82; H, 9.52. Found: C,
64.96; H, 9.44.
The cycloadducts 2a, 2b, 2d, 2e, 2g were reported
previously.11
4.3.1. (4aS*,8aR*)- and (4aS*,8aS*)-8a-Methyl-3,4,4a,
7,8,8a-hexahydro-1H-isochromen-1-one (2f-endo and 2f-
exo). The reaction of 1f (83 mg, 0.50 mmol) with
TfN[Al(Me)Cl]2 (0.55 mmol) and the subsequent purifi-
cation by column chromatography on silica gel (hexane/
AcOEtZ10:1) gave the product 2f as endo/exo mixture
(56.2 mg, 78% yield, endo/exoZ9.5:1). 2g-endo: IR (neat) n
1
cmK1; 1722. H NMR (400 MHz, CDCl3) d; 1.33 (3H, s),
4.3.4. (4R*,4aS*,7S*,8aR*)- and (4R*,4aR*,7R*,8aS*)-4-
{[tert-Butyl(dimethyl)silyl]-oxy}-7-methyl-3,4,4a,7,8,8a-
hexahydo-1H-isochromen-1-one (2j-trans and 2j-cis). A
cis/trans mixture of 2j obtained from the reaction of 1j
(148 mg, 0.50 mmol) with TfN(AlMe2)2 (0.55 mmol) was
separated by MPLC (hexane/AcOEtZ10:1, flow rate
7.0 mL/min) to give 2j-cis (13.0 mg, 9% yield) and 2j-
trans (96.5 mg, 65% yield) in the order of elution. 2j-trans:
mp 78.0–79.5 8C. IR (KBr) n cmK1; 1736. 1H NMR
(400 MHz, CDCl3) d; 0.05 (3H, s), 0.07 (3H, s), 0.87 (9H,
s), 1.00 (3H, d, JZ7.1 Hz), 1.78 (1H, ddd, JZ12.2, 12.0,
10.0 Hz), 2.17 (1H, ddd, JZ12.2, 4.7, 4.2 Hz), 2.19–2.28
(1H, m), 2.55–2.60 (1H, m), 2.78 (1H, ddd, JZ12.0, 7.8,
4.2 Hz), 4.02 (1H, dd, JZ4.5, 2.3 Hz), 4.30 (2H, d, JZ
2.3 Hz), 5.50 (1H, ddd, JZ10.0, 3.1, 3.1 Hz), 5.78 (1H, bd,
JZ10.0 Hz). 13C NMR (100.6 MHz, CDCl3) d; K4.9,
K4.6, 18.0, 21.0, 25.7, 30.0, 33.5, 37.6, 38.1, 66.7, 73.6,
124.6, 136.8, 173.5. ESI-MS m/z: 297 (MCCH). HRMS:
Calcd for C16H29O3Si: 297.1886, Found: 297.1884. 2j-cis:
mp 84.5–85.5 8C. IR (KBr) n cmK1; 1736. 1H NMR
(400 MHz, CDCl3) d; 0.08 (3H, s), 0.09 (3H, s), 0.89 (9H,
s), 1.02 (3H, d, JZ7.2 Hz), 1.60 (1H, ddd, JZ13.2, 10.5,
8.1 Hz), 2.09 (1H, ddd, JZ13.2, 4.9, 4.8 Hz), 2.25–2.27
(1H, m), 2.50–2.51 (1H, m), 2.93 (1H, ddd, JZ10.5, 6.8,
4.8 Hz), 3.83 (1H, ddd, JZ7.8, 7.5, 3.7 Hz), 4.00 (1H, dd,
JZ11.0, 3.7 Hz), 4.26 (1H, dd, JZ11.0, 3.7 Hz), 5.64 (1H,
ddd, JZ10.1, 3.5, 2.5 Hz), 5.76 (1H, ddd, JZ10.1, 2.1,
1.45 (1H, ddd, JZ13.2, 7.3, 5.7 Hz), 1.63 (1H, dddd,
JZ8.1, 8.1, 5.7, 4.0 Hz), 2.00–2.07 (1H, m), 2.16 (1H,
ddd, JZ13.2, 4.8, 4.8 Hz), 2.13–2.27 (1H, m), 2.35 (1H,
ddd, JZ11.4, 5.7, 2.6 Hz), 4.23–4.28 (1H, m), 5.48 (1H,
ddd, JZ9.9, 4.7, 2.6 Hz), 5.58 (1H, ddd, JZ9.9, 6.0,
3.7 Hz). 13C NMR (100.6 MHz, CDCl3) d; 22.4, 26.0,
26.3, 32.1, 38.8, 41.7, 67.4, 127.7, 129.8, 176.5. EI-MS
m/z: 166 (MC). HRMS calcd for C10H14O2: 166.0994
(MC), Found: 166.0981. 2g-exo: IR (neat) n cmK1
;
1722. 1H NMR (400 MHz, CDCl3) d; 1.16 (3H, s),
1.73–1.81 (1H, m), 1.86–1.99 (2H, m), 2.08–2.28 (3H,
m), 2.47–2.52 (1H, m), 4.36 (1H, ddd, JZ11.6, 11.6,
6.5 Hz), 4.49 (1H, ddd, JZ11.6, 7.5, 1.9 Hz), 5.34–5.40
(1H, m), 5.64–5.71 (1H, m). 13C NMR (100.6 MHz,
CDCl3) d; 16.1, 22.6, 24.2, 29.8, 37.0, 39.8, 68.6, 126.5,
127.4, 176.6. EI-MS m/z: 166 (MC). HRMS calcd for
C10H14O2: 166.0994 (MC), Found: 166.0990.
4.3.2. (4R,4aR,7S,8aR)- and (4R,4aS,7R,8aS)-4,7-
Dimethyl-3,4,4a,7,8,8a-hexahydro-1H-isochromen-1-
one (2h-cis and 2h-trans). A cis/trans mixture of 2h
obtained from the reaction of 1h (90.5 mg, 0.50 mmol) with
TfN[Al(Me)Cl]2 (0.55 mmol) was separated by MPLC
(hexane/AcOEtZ10:1, flow rate 7.0 mL/min) to give 2h-
cis (69.4 mg, 71% yield) and 2h-trans (9.5 mg, 10% yield)
1
in the order of elution. 2h-cis: IR (neat) n cmK1; 1732. H

12246
A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
2.1 Hz). 13C NMR (100.6 MHz, CDCl3) d; K4.8, K4.6,
18.0, 21.3, 25.7, 30.0, 32.5, 37.7, 39.5, 68.0, 71.6, 124.6,
135.8, 173.5. ESI-MS m/z: 297 (MCCH). HRMS: Calcd for
C16H29O3Si: 297.1886, Found: 297.1903. Anal. Calcd for
C16H28O3Si: C, 64.82; H, 9.52. Found: C, 64.56; H, 9.22.
2. For reviews on IMDA reaction, see: (a) Roush, W. R. In
Curran, D. P., Ed.; Advances in Cycloaddition; JAI:
Greenwich, CT, 1990; Vol. 2, pp 91–146. (b) Roush, W. R.
In Trost, B. M., Fleming, I., Eds.; Comprehensive Organic
Synthesis; Pergamon: Oxford, 1991; Vol. 2, pp 513–550.
(c) Ciganek, E. In Dauben, W. G., Ed.; Organic Reactions;
Wiley: New York, 1984; Vol. 2, pp 1–374. (d) Weinreb, S. W.
Acc. Chem. Res. 1985, 18, 16.
4.4. Procedure for thermal IMDA reaction of 1,7,9-
decatrienoates 1j
3. For references of natural product syntheses, see: (a) Fallis,
A. G. Acc. Chem. Rev. 1999, 32, 464–474. (b) Suzuki, Y.;
Murata, T.; Takao, K.; Tadano, K. J. Synth. Org. Chem. 2002,
60, 679–689.
After a solution of 1j (148 mg, 0.50 mmol) in 1,2-
dichlorobenzene (9 mL) was stirred for 12 h at 140 8C,
reaction mixture was concentrated under reduced pressure.
The residue was chromatographed on silica gel (hexane/
AcOEtZ10:1) to give 2j as a cis/trans mixture, which was
separated by MPLC (hexane/AcOEtZ10:1, flow rate
7.0 mL/min) to give 2j-cis (87.4 mg, 59% yield) and 2j-
trans (22.4 mg, 15% yield) in the order of elution.
4. (a) Boeckman, R. K. Jr.; Demko, D. M. J. Org. Chem. 1982,
47, 1789–1792. (b) Martin, S. F.; Williamson, S. A.; Gist,
R. P.; Smith, K. M. J. Org. Chem. 1983, 48, 5170–5180.
5. (a) Nakanishi, H.; Fujita, H.; Yamamoto, O. Bull. Chem. Soc.
Jpn. 1978, 51, 214. (b) Parker, K. A.; Adamchuk, M. R.
Tetrahedron Lett. 1978, 1689–1692. (c) Perrin, C. L.; Young,
D. B. Tetrahedron Lett. 1995, 36, 7185–7188. (d) Toyota, M.;
Wada, Y.; Fukumoto, K. Heterocycles 1993, 35, 111–114.
6. (a) Jung, M. E.; Huang, A.; Johnson, T. W. Org. Lett. 2000, 2,
1835–1837. For theoretical discussions of the transition states
in the IMDA reaction of 1,7,9-decatrienoates, see: (b) Tantillo,
D. J.; Houk, K. N.; Jung, M. E. J. Org. Chem. 2001, 66,
1938–1940.
4.5. General procedure for conversion to oxa-
bicyclo[4.3.0]nonene derivatives: (3R*,3aS*, 6S*,7aR*)-
3-(hydroxymethyl)-6-methyl-3a,6,7,7a-tetrahydro-1-
benzofuran-1(3H)-one (4a)
A mixture of 2j-cis (104 mg, 0.25 mmol) and tetrabuthyl-
ammonium fluoride (0.75 mL, 1.0 M solution in THF) in
THF (1 mL) was stirred for 3 h at room temperature, and
then usual work-up followed by the purification by column
chromatography on silica gel (hexane/AcOEtZ1:1) gave 4a
(32.8 mg, 72% yield) as white solid. Mp 44–46 8C. IR (neat)
7. (a) Jung, M. E.; Gervay, J. J. Am. Chem. Soc. 1989, 111,
5469–5470. (b) Jung, M. E. Synlett 1990, 4, 186–190. (c) Jung,
M. E. Synlett 1999, 843–846.
8. (a) Taillefumier, C.; Chapleur, Y.; Bayeul, D.; Aubry, A.
J. Chem. Soc., Chem. Commun. 1995, 937–938. (b)
Taillefumier, C.; Chapleur, Y. Can. J. Chem. 2000, 78,
708–722.
1
n cmK1; 1771, 3447. H NMR (400 MHz, CDCl3) d; 1.03
(3H, d, JZ7.2 Hz), 1.42 (1H, ddd, JZ13.3, 10.3, 8.3 Hz),
2.05 (1H, ddd, JZ13.3, 5.7, 5.7 Hz), 2.15–2.24 (1H, m),
2.79 (1H, ddd, JZ10.3, 9.9, 5.7 Hz), 3.16–3.25 (1H, m),
3.51 (2H, d, JZ5.8 Hz), 4.68 (1H, dt, JZ8.7, 5.8 Hz), 5.54
(1H, ddd, JZ10.1, 2.9, 2.8 Hz), 5.81 (1H, ddd, JZ10.1, 2.3,
2.3 Hz). 13C NMR (100.6 MHz, CDCl3) d; 21.2, 28.3, 29.5,
35.3, 37.9, 63.5, 81.7, 119.9, 137.0, 179.0. ESI-MS m/z: 183
(MCCH). HRMS: Calcd for C10H15O3: 183.1021. Found:
183.1012.
9. (a) Ichikawa, T.; Senzaki, M.; Kadoya, R.; Morimoto, T.;
Miyake, N.; Izawa, M.; Saito, S.; Kobayashi, H. J. Am. Chem.
Soc. 2001, 123, 4607–4608. (b) Ishikawa, T.; Kudoh, T.; Saito,
S. J. Synth. Org. Chem. 2003, 61, 1186–1194.
10. (a) Boeckman, R. K. Jr.; Flam, C. J. Tetrahedron Lett. 1983,
24, 5035–5038. (b) Alexakis, A.; Jachiet, D.; Toupet, L.
Tetrahedron 1989, 45, 6203–6210.
11. Saito, A.; Ito, H.; Taguchi, T. Org. Lett. 2002, 4, 4619–4621.
12. For examples of significant activation of carbonyl group by a
bidentate Lewis acid, see: (a) Hanawa, H.; Maruoka, K.
Tetrahedron Lett. 1999, 40, 5365–5368. (b) Hanawa, H.;
Maekawa, N.; Maruoka, K. Tetrahedron Lett. 1999, 40,
8379–8382.
4.5.1.
(3R*,3aR*,6R*,7aS*)-3-(Hydroxymethyl)-6-
methyl-3a,6,7,7a-tetrahydro-1-benzo-furan-1(3H)-one
(4b). 91% yield. White solid. Mp 57–58 8C. IR (neat) n
1
cmK1; 1772, 3287. H NMR (400 MHz, CDCl3) d; 1.07
(3H, d, JZ7.1 Hz), 1.24–1.37 (1H, m), 2.09 (1H, ddd, JZ
12.9, 4.8, 4.7 Hz), 2.20–2.31 (1H, m), 2.80 (1H, dd, JZ
12.6, 4.4 Hz), 2.89–2.97 (1H, m), 3.74 (1H, dd, JZ12.6,
4.4 Hz), 3.99 (1H, dd, JZ12.6, 2.4 Hz), 4.25 (1H, ddd, JZ
9.3, 4.4, 2.4 Hz), 5.58 (1H, ddd, JZ10.0, 3.9, 2.6 Hz), 5.77
(1H, bd, JZ10.0 Hz). 13C NMR (100.6 MHz, CDCl3) d;
21.6, 29.2, 29.7, 35.7, 39.7, 62.5, 84.5, 121.9, 136.6, 187.5.
ESI-MS m/z: 183 (MCCH). HRMS: Calcd for C10H15O3:
183.1021. Found: 183.1015.
13. Kim, P.; Hantz, M. H.; Kurth, M. J.; Olmstead, M. M. Org.
Lett. 2000, 2, 1831–1834.
14. Remiszewski, S. W.; Stouch, T. R.; Weinreb, S. W.
Tetrahedron Lett. 1985, 41, 1173–1178.
15. Recently NMR studies of b-TBSO substituted ketones with
Me2AlCl implied the chelation of TBSO group to aluminum
metal, see: Evans, D. A.; Allison, B. D.; Yang, M. G.; Masse,
C. E. J. Am. Chem. Soc. 2001, 123, 10840–10852.
16. Elucidation of mechanistic detail, for example, based on the
structure of the substrate–Lewis acid complex form and based
on the stereochemical outcome in the IMDA reaction of
alkoxy-instead of silyloxy-substituted substrate is the future
subject. Concerning the substituent effect of silyloxy group on
the transition state of the IMDA reaction, it was reported that
silyloxy group at C7 position in the 2,8,10-undecatrienal
derivatives preferentially occupies pseudo-axial position. See:
Marshall, J. A.; Shearer, B. G.; Crooks, S. L. J. Org. Chem.
1987, 52, 1236–1245.
References and notes
1. Oppolzer, W. In Trost, B. M., Fleming, I., Eds.; Comprehen-
sive Organic Synthesis; Pergamon: Oxford, 1991; Vol. 5,
Chapter 4.1, p 315.

A. Saito et al. / Tetrahedron 60 (2004) 12239–12247
12247
17. It was reported that the stereoselectivity of the IMDA reaction
of 1,6,8-nonatrienoate 5 under the thermal conditions is low to
give a mixture of oxabicyclo[4.3.0]nonene derivatives 6, see:
see: White, J.D., Nolen, E.G., Jr., Miller, C.H., J. Org. Chem.
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