Dual behavior of masked o-benzoquinones in intramolecular Diels-Alder reactions. Expedient synthesis of highly functionalized cis-decalins from 2-methoxyphenols

Article abstract of DOI:10.1021/jo0510179

The potential dual behavior as dienes and dienophiles of the diene moieties of masked o-benzoquinones (MOBs) 10a-e-12a-e, generated upon oxidation of 2-methoxyphenols 1-3 with BTIB in the presence of appropriate dienols, in their intramolecular Diels-Alde

Full text of DOI:10.1021/jo0510179

Dual Behavior of Masked o-Benzoquinones in Intramolecular
Diels-Alder Reactions. Expedient Synthesis of Highly
Functionalized cis-Decalins from 2-Methoxyphenols
Po-Yi Hsu, Rama Krishna Peddinti, Santhosh Kumar Chittimalla, and Chun-Chen Liao*
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300
ccliao@mx.nthu.edu.tw
Received May 22, 2005
The potential dual behavior as dienes and dienophiles of the diene moieties of masked o-
benzoquinones (MOBs) 10a-e-12a-e, generated upon oxidation of 2-methoxyphenols 1-3 with
BTIB in the presence of appropriate dienols, in their intramolecular Diels-Alder (IMDA) reactions
has been examined. The IMDA reactions of MOBs 10a-d, 11a,b,d, and 12a,b,d resulted in highly
functionalized oxatricyclic compounds 18a-d, 19a,b,d, and 20a,b,d, respectively, with concomitant
formation of cis-decalin derivatives 21a-d, 22a,b,d, and 23a,b,d in a highly regio- and stereo-
selective manner. However, the MOBs 10e-12e provided exclusively oxatricyclic compounds 18e-
20e. The formation of cis-decalins in these IMDA reactions illustrates the dienophilic character of
MOBs, in addition to their behavior as dienes. The ratio of the two cycloadducts obtained in each
reaction as a result of the dual character of MOBs depends on the nature and/or position of the
substituents on both the cyclohexadienone moiety and the added 2,4-dienol. The majority of the
cycloadducts resulted from the diene property of MOBs in intramolecular Diels-Alder reactions
smoothly underwent Cope rearrangement to furnish cis-decalins as sole products in excellent to
quantitative yields that provides a short and efficient entry to polyfunctionized cis-decalins from
2-methoxyphenols. Furthermore, the variation of dienophilic and diene characters of MOBs in the
IMDA reactions with the electron-donating or electron-withdrawing substituent of both cyclohexa-
dienone moiety and the added conjugated acyclic diene or 2,4-dienol has been studied in detail.
Introduction
intramolecular version, i.e., the intramolecular Diels-
Alder (IMDA) reaction, is a versatile tool for the rapid
construction of polycyclic ring systems with high degree
of structural and stereochemical complexity.3,5 The ad-
vantages of an intramolecular reaction over its inter-
The Diels-Alder reaction has become one of the most
commonly used paradigms in organic chemistry. It has
been enjoying widespread use in organic synthesis owing
to its ability of forming two bonds in a cyclohexenyl
system and simultaneous creation of up to four stereo-
genic centers in a highly stereoselective and predictable
manner.1-3 Furthermore, the Diels-Alder reaction is
considered as one of the most efficient reactions in terms
of atom economy and broad versatility.4 Particularly, the
(2) (a) Fringuelli, F.; Taticchi, A. The Diels-Alder Reaction: Selected
Practical Methods; Wiley: Chichester, 2002. (b) Fa˜llis, A, G,; Lu, Y.-
F. Advances in Cycloadditions; JAI Press, Inc.: Greenwich, CT, 1993;
Vol. 3, Chapter 1, pp 1-66. (c) Oppolzer, W. In Comprehensive Organic
Synthesis; Trost, B. M., Fleming, I. Eds.; Pergamon Press: New York,
1991; Vol. 5, Chapter 4.1, pp 316-399.
(3) (a) Corey, E. J. Angew. Chem., Int. Ed. 2002, 41, 1650. (b)
Nicolaou, K. C.; Snyder, S. A.; Montagnon, T.; Vassilikogiannakis, G.
E. Angew. Chem., Int. Ed. 2002, 41, 1668. (c) Stocking, E. M.; Williams,
R. M. Angew. Chem., Int. Ed. 2003, 42, 3078.
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* To whom correspondence should be addressed. Fax: 886-3-
5728123.
(1) Carruthers, W. Cycloaddition Reactions in Organic Synthesis;
Pergamon: Oxford, 1990.
10.1021/jo0510179 CCC: $30.25 © 2005 American Chemical Society
Published on Web 10/15/2005
9156
J. Org. Chem. 2005, 70, 9156-9167

Dual Behavior of MOBs in IMDA Reactions
SCHEME 1
molecular counterpart are well documented in terms of
milder reaction conditions, superior reactivity due to
favorable entropy considerations, and hightened regio-
selectivities due to constraints posed by the connecting
chain.6 The IMDA reactions are commonly employed in
combination with other reactions in tandem processes.7
The synthesis of triene precursors required for IMDA
reactions is achieved either by (i) in situ tethering of 4π-
and 2π-components via alkylation, acylation, and con-
densation or (ii) in situ generation of either diene or
alkene via oxidation, elimination, and retrogradation.8,9
6,6-Dialkoxycyclohexa-2,4-dienones, named as masked
o-benzoquinones (MOBs)10a,c by us, are very reactive cyclic
conjugated dienones and readily undergo self-dimeriza-
tion via Diels-Alder cycloaddition between a dienic MOB
and a dienophilic MOB.11,12a It was found that oxidation
of simple and readily accessible 2-methoxyphenols in
methanol with diacetoxyiodobenzene (DAIB) or bis-
(trifluoroacetoxy)iodobenzene (BTIB) produce highly re-
active MOBs.10c,13,14 We successfully employed MOBs as
exclusive 4π-partners in intermolecular Diels-Alder
reactions by trapping them with various olefinic dieno-
philes to furnish bicyclo[2.2.2]oct-5-en-2-one derivatives
with complete ortho,anti-selectivity12 (the substituent on
the dienophile is adjacent and anti to the carbonyl
function of the bicyclo[2.2.2]octenone moiety). The IMDA
reaction of MOBs, generated in situ by oxidation of
2-methoxyphenols in the presence of allylic and homo-
allylic alcohols in a tandem oxidative acetalization pro-
cess, provides oxacyclic compounds with complete
meta,syn-selectivity15 (with respect to the carbonyl group
present in the Diels-Alder adduct) (Scheme 1).
SCHEME 2. Dual Behavior of MOBs in IMDA
Reactions
The capacity of the cyclohexa-2,4-dienone unit of MOBs
to react as a dienophile component in both inter-16 and
intramolecular17 Diels-Alder cycloadditions has been
(5) (a) Roush, W. R. In Comprehensive Organic Synthesis; Trost, B.,
Ed.; Oxford: Pergamon Press, 1991; Vol. 5, pp 513-550. (b) Fallis, A.
G. Acc. Chem. Res. 1999, 32, 464. (c) Brocksom, T. J.; Nakamura, J.;
Ferreira, M. L.; Brocksom, U. J. Braz. Chem. Soc. 2001, 12, 597. (d)
Bear, B. R.; Sparks, S. M.; Shea, K. J. Angew. Chem., Int. Ed. 2001,
40, 820. (e) Anderson, J. C.; Blake, A. J.; Graham, J. P.; Wilson, C.
Org. Biomol. Chem. 2003, 16, 2877.
encountered in our laboratories. Simultaneously, dieno-
philic reactivity of MOBs in the IMDA reaction was
reported in the total synthesis of naphthofurans and
phenanthrofurans18a and (()-xestoquinone.18b An o-quinol
acetate was employed as a dienophile in the Diels-Alder
reactions with Brassard’s diene to provide functionally
rich naphthalenes which were key intermediates in the
syntheses of helically chiral molecules.19 Based on this
background, we are interested in employing cyclohexa-
2,4-dienone moiety of MOB as dienophile for the con-
struction of highly functionalized cis-decalins. We now
report herein full details of dual nature of MOBs in their
IMDA reactions, together with the results of our studies
on the variation of the dienic and dienophilic properties
of MOBs with the nature and position of the substituents
on both the cyclohexadienone moiety and the tethered
acyclic 2,4-dienic unit17 (Scheme 2). The cycloadducts
obtained from the dienic MOB and dienophilic tether
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10889.
J. Org. Chem, Vol. 70, No. 23, 2005 9157

Hsu et al.
SCHEME 3
SCHEME 4
is to understand the factors affecting the dual nature of
MOBs with these electronically different tethers in the
IMDA reactions. Thus, sorbyl alcohol (9b), which was
expected to have more dienic character, trans-5-ethoxy-
carbonylpenta-2,4-dienol (9c),20 where the presence of an
ethoxycarbonyl group increases the dienophilic nature of
this tether, were tested along with 9d. Consequently, the
MOBs 10b-d which were generated in situ by the BTIB-
mediated oxidation of 2-methoxyphenol 1 in the presence
of dienols 9b-d, produced a pair of expected products
18b, 21b; 18c, 21c; and 18d, 21d, respectively. The
IMDA reactions of MOBs 10a,c,d produced a 1:1 mixture
of the corresponding oxatricyclic product 18a, 18c, and
18d and cis-decalin 21a, 21c, and 21d, while the MOB
10b derived from sorbyl alcohol and 2-methoxyphenol 1
gave cis-decalin 21b as the major product. The combined
yields of the cycloadducts obtained from the dual reactiv-
ity of MOBs are good. Under similar conditions, the MOB
10e generated from methyl vanillate and cis-penta-2,4-
dienol (9e)20 could provide only the oxatricyclic compound
18e (Scheme 4). In the case of MOB 10e, if the tether
were to act as a diene, then its approach to the dienophilic
part of cyclohexa-2,4-dienone should be an endo-approach
in the transition state which is an unfavorable pathway
due to ring strain. The other possible reaction pathway
should be an exo-approach which is not observed, prob-
ably due to the high energy associated in the transition
state (Scheme 4, simplified transition-state structure D).
Consequently, the only other preference is the formation
of cycloadduct 18e (Scheme 4, simplified transition-state
structure C). For compound 18e, though with a 1,5-diene
unit, the two double bonds (one terminal and the other
being the internal double bond) have a fixed and unfa-
vorable configuration for the Cope rearrangement to
occur.
smoothly underwent the Cope rearrangement to provide
the highly functionalized cis-decalins.
Results and Discussion
(a) Intramolecular Diels-Alder Reactions. The
IMDA reactions of MOBs 10a-e-12a-e generated from
the 2-methoxyphenols 1-3 in the presence of 2,4-dienols
9a-e, respectively, as outlined in Schemes 3 and 4 were
first examined and the results are summarized in Table
1. It may be noted that the 2-methoxyphenols in these
cases are all bearing the substituent (methoxycarbonyl,
methyl and 5,5-dimethyl-1,3-dioxanyl) at the C-4 posi-
tion. The reason for such selection is that the resulting
cis-decalins obtained in the Diels-Alder reactions would
possess substitution at the fused position, as most of the
decalin-containing natural products have angular sub-
stitutions.
Initial investigations were conducted on the MOB 10a
which was generated in situ from methyl vanillate (1) in
the presence of trans-penta-2,4-dienol (9a)20 using BTIB
in THF. At room temperature, the MOB 10a, exhibiting
the dual behavior both as a diene (Scheme 3, simplified
transition-state structure A) and a dienophile (Scheme
3, simplified transition-state structure B), underwent
IMDA reactions to provide the tricyclic compound 18a
and cis-decalin derivative 21a each in 31% isolated yields.
Subsequently, this reaction was extended to various 2,4-
dienols 9b-e. The reason for choosing such 2,4-dienols
For evaluating the effect of electron-donating substitu-
ent on the C4 of cyclohexadienone moiety on these IMDA
reactions, creosol (2) was oxidized in the presence of 2,4-
dienols 9a-e. The increase in the dienic character of
MOBs 11a-e is clear from Table 1; the major product is
oxatricyclic compound formed via path a in the IMDA
reactions of 11a,b,d, whereas 11c, in which dienol tether
(20) Deslongchamps, P.; Berube, G. Can. J. Chem. 1990, 68, 404.
9158 J. Org. Chem., Vol. 70, No. 23, 2005

Dual Behavior of MOBs in IMDA Reactions
TABLE 1. Intramolecular Diels-Alder Reactions of Masked o-Benzoquinones 10a-e-12a-e
Diels-Alder reactiona
Cope rearrangement of I
adducts/yieldd (%)
yieldd of II (%)
from If total method Cg
addition
after
T
time
(h)
entry phenol dienola MOB timeb/T (°C) additionc (h)
I
II
I:IIe (°C)
1
2
1
2
3
9a
9b
9c
9d
9e
9a
9b
9c
9d
9e
9a
9b
9c
9d
9e
10a
10b
10c
10d
10e
11a
11b
11c
11d
11e
12a
12b
12c
12d
12e
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
18a/31 21a/31
18b/16 21b/42
18c/35 21c/35
18d/25 21d/25
18e/47 21e/0
19a/40 22a/20
19b/46 22b/16
19c/61 22c/0
19d/34 22d/9
19e/52 22e/0
20a/57 23a/19
20b/60 23b/10
20c/42 23c/0
20d/18 23d/2
20e/36 23e/0
1:1
1:3
1:1
1:1
1:0
2:1
3:1
1:0
4:1
1:0
3:1
6:1
1:0
9:1
1:0
200
200
200
220
200
200
200
200
250
200
200
220
200
250
220
8
10
24
10
24
8
92
93
0
92
0
93
95
45
75
0
100
93
41
80
0
60
57
35
48
0
57
60
28
35
0
76
66
17
16
0
50
55
30
48
0
62
72
23
35
0
60
73
0
13
0
3
4
5
6
7
8
8
8
6
9
10
11
12
13
14
15
24
8
8
8
8
24
a Diels-Alder reactions were carried out according to method A using 10 equiv of the appropriate dienol. b Time period during which
BTIB in THF was added to the reaction mixture containing the appropriate 2-methoxyphenol and dienol in THF. c Time period for which
the reaction mixture was allowed to stir at rt after the complete addition of BTIB. d Yields are of isolated products. e Ratio of the products
was determined by the 1H NMR spectrum of the crude reaction mixture and adjusted to the nearest whole number. f Cope rearrangements
of I were carried out according to method B. g In method C, the crude mixture of Diels-Alder adducts I and II was as such subjected to
Cope rearrangements.
TABLE 2. Intramolecular Diels-Alder Reactions of Masked o-Benzoquinones 13a-c-17a-c
Diels-Alder reactiona
Cope rearrangement of IIIf
adducts/yieldd (%)
yieldd of IV(%)
addition
after
Tf
(°C)
time
(h)
entry
phenol
dienola
MOB
timeb/T (°C)
additionc (h)
III
IV
III:IVe
from III
total
1
2
4
9a
9b
9c
9a
9b
9c
9a
9b
9c
9a
9b
9c
9a
9b
9c
13a
13b
13c
14a
14b
14c
15a
15b
15c
16a
16b
16c
17a
17b
17c
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
10 min/rt
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
24a/13
24b/ 31
24c/18
25a/5
25b/31
25c/0
26a/0
26b/12
26c/0
27a/6
27b/6
27c/0
28a/6
28b/28
28c/0
29a/12
29b/31
29c/0
30a/7
30b/11
30c/0
31a/0
31b/0
31c/0
32a/6
32b/6
32c/0
33a/6
33b/19
33c/0
1:1
1:1
1:0
1:1
3:1
200
200
200
200
200
200
200
200
250
200
200
220
200
200
220
8
10
24
8
94
99
0
89
99
25
62
0
3
4g
5h
6
5
6
7
8
12
42
0
8
8
8
7i
0
8j
1:0
24
6
0
0
9
0
10k
11
12
13l
14
15
1:1
1:1
8
96
94
12
12
0
8
8
1:1
2:1
8
85
86
85
11
43
0
8
8
a Diels-Alder reactions were carried out according to method A with 10 equiv of the appropriate dienol. b Time period during which
BTIB in THF was added to the reaction mixture containing the appropriate 2-methoxyphenol and dienol in THF. c Time period for which
the reaction mixture was allowed to stir at rt after the complete addition of BTIB. d Yields are of isolated products. e Ratio of the products
was determined by the 1H NMR spectrum of the crude reaction mixture and adjusted to the nearest whole number. f Cope rearrangements
of III were carried out according to method B. g In IMDA reaction of entry 4, in addition to the products 25a and 30a, oxidation product
34 was also isolated in 30% yield. h In IMDA reaction of entry 5, in addition to the products 25b and 30b, oxidation product 35 was also
isolated in 15% yield. i In IMDA reaction of entry 7, instead of expected products 26a and 31a, oxidation product 36 was also isolated in
20% yield. j In IMDA reaction of entry 8, in addition to 26b, oxidation product 37 was also isolated in 9% yield. k In IMDA reaction of
entry 10, in addition to the products 27a and 32a, oxidation product 38 was also isolated in 20% yield. l In IMDA reaction of entry 13, in
addition to the products 28a and 33a, oxidation product 39 was also isolated in 25% yield.
is electron-poor, brings 19c exclusively with no traces of
22c. A similar trend was observed from the IMDA
reactions of MOBs 12a-e generated from 2-methoxyphe-
nol 3 and dienols 9a-e resulting in the formation of
cycloadducts 20a-e and 23a-e. In these cases, it may
be noted that the product resulted from the diene
character of MOB (path a) is still predominant due to
the steric and electronic effects exerted by the bulky ketal
group present on the C-4 position of cyclohexadienone
moiety. The MOBs 10e-12e where the dienol tether uses
its cis double bond in the IMDA reaction consequently
led to the oxatricycles 18e-20e via path a exclusively
as predicted.
To study the variation of dienophilic and diene char-
acters of the MOBs with the position and the nature of
the substituent on the MOBs as well as 2,4-dienols, the
IMDA reactions of MOBs 13a-c-17a-c were per-
formed. The vehicles chosen for our study are unsubsti-
tuted 2-methoxyphenol (guaiacol, 4), 2-methoxyphenols
with electron-donating and withdrawing substituents at
position 6 (5, 7), and position 5 (6, 8), respectively, and
2,4-dienols 9a-c. Initially, the oxidation of 4 with BTIB
in THF was carried out at room temperature in the
presence of the dienol 9a to generate the MOB 13a. When
the IMDA reaction of MOB 13a reached completion, after
6 h at the room temperature, the usual workup followed
J. Org. Chem, Vol. 70, No. 23, 2005 9159

Hsu et al.
SCHEME 5
a 1:1 mixture of cycloadducts along with oxidation
product 39 in 25% yield. MOB 15b gave exclusively 26b
following path a along with 9% of oxidation product 37,
while 17b provided a 2:1 mixture of cycloadducts. It is
interesting to note that 6 and 8 did not afford 26c, 31c,
and 28c, 33c, respectively. The formation of all the
unexpected products 34-39 can be attributed to the
absence of a substitution on oxidation-prone C-4 of these
2-methoxyphenols (5-8). Similar oxidation at position-4
was observed during our recent study on IMDA reactions
of MOBs derived from 2-methoxyphenols and allyl
alcohols.15a
The formation of cis-decalins in method A needs
further comment as they could in principle have resulted
in two ways: either by (i) direct Diels-Alder reactions,
in which MOB moieties behave as dienophiles, or (ii) a
tandem process involving Diels-Alder reaction in which
MOB moieties serve as dienes and Cope rearrangements.
All of our cases transforming bicyclo[2.2.2]octenones (18-
20 and 24-28) into cis-decalins (21-23 and 29-33) took
place at elevated temperatures as in cases of usual Cope
rearrangements (see the later discussion). To check the
possibility that CF3CO2H formed during the course of
reaction may catalyze the Cope rearrangement although
it seems quite improbable, we treated bicyclo[2.2.2]-
octenones 19b and 24b with CF3CO2H (10 equiv) and
dienol 9b (10 equiv) in dry THF at room temperature for
24 h. No cis-decalins were observed, and the reactants
remained unchanged during the reaction period; thus,
we believe that the present dual Diels-Alder reactions
are kinetically controlled reactions. Consequently, the
second possibility could be ruled out since Cope rear-
rangements require elevated temperatures.
CHART 1
From the foregoing IMDA reactions of all MOBs
conducted in the present study, the following empirical
rules can be proposed regarding the variation of dieno-
philicity and diene character of the MOBs as a function
of their substitution pattern and also of the added 2,4-
dienols.
(1) When the cyclohexadienone moiety of MOB acts as
a diene in the IMDA reaction, oxatricyclic compound will
be formed, whereas if the former acts as a dienophile,
cis-decalin product will be obtained. If R1 is an electron-
withdrawing (methoxycarbonyl) group as in MOBs 10a-
e, the relative diene character of the MOB will be
diminished and the dienophilicity of the double bond to
the ester carbonyl group will be enhanced and as a result,
the yield of the cis-decalin product will be either pre-
dominant or in comparable with the corresponding ox-
atricyclic product (Table 1, entries 2-5). If R1 is a methyl
group, MOB becomes electron-rich and hence exhibits
diene character. Consequently, the major product will be
the oxatricyclic compound (Table 1, entries 6-10), prob-
ably due to the electronic effect. If R1 is a ketal group,
the product resulted from the diene character will be still
predominant (Table 1, entries 11-15) presumably be-
cause of the electronic effect and to some extent steric
effect.
by silica gel column chromatography (method A) provided
1:1 ratio of products 24a and 29a in poor yield (25% total
yield, Table 2 and Scheme 5). Similar results were
obtained in the unimolecular reactions of 14a, 16a, and
17a leading to the oxatricyclic compounds 25a, 27a, and
28a and cis-decalin compounds 30a, 32a, and 33a,
respectively, in a 1:1 ratio. These oxatricyclic compounds
were accompanied by the corresponding p-hydroquinones
34, 38, and 39 in 20-30% yield (entries 4, 10, and 13,
Table 2, Chart 1). The reaction of methyl o-vanillate (6)
with 9a gave the p-hydroquinone 36 instead of the
expected cycloadducts. The electron-releasing methyl
group substituted 2-methoxyphenols 5 and 7 with 9b
gave the products in 3:1 and 1:1 ratios; however, 2-meth-
oxyphenol 5 also furnished oxidation product 35 in 15%
yield. On the other hand, the reactions of dienol 9c with
5 and 7 provided no cycloadducts. When electron-poor
2-methoxyphenols 6 and 8 were subjected to oxidation
in the presence of 2,4-dienols 9a-c followed by the IMDA
reactions, instead of the formation of cycloadducts, 6 with
9a gave oxidation product 36 in 20% yield, while 8 gave
(2) It may be noted that the IMDA reactions of MOBs
10e-12e (Scheme 4) tethered with cis-penta-2,4-dienol,
(Table 1, entries 5, 10, 15) furnished exclusively the
oxatricyclic compounds 18e-20e, respectively. The effect
of ring strain prevents the cis-penta-2,4-dienyl moiety
from behaving as a diene to give the cis-decalin products.
9160 J. Org. Chem., Vol. 70, No. 23, 2005

Dual Behavior of MOBs in IMDA Reactions
CHART 2. NOE Enhancements of the
Cycloadducts 22b and 22d
is clear that Hd with He and bridged methyl group are of
cis-relationship. In the case of 22d, saturation of the
bridged methyl protons gave rise to an increase in signal
intensity of bridged proton Hb (3.3%) while saturation of
Hb brought about significant NOE in the methyl (3.0%)
group present at the fused junction of 6 and five-
membered ring. Similarly when methyl was saturated
gave rise to enhancement in the signal intensity of Hb
(3.5%) thus confirming these groups are of cis-relation-
ship to each other. In the cases of the remaining decalins,
the stereochemical assignments were based on analogy
of the coupling patterns.
(c) Cope Rearrangement of the Cycloadducts. The
majority of the oxatricyclic compounds obtained from
IMDA reactions underwent Cope rearrangement smoothly
when heated to 200-250 °C in mesitylene with the
addition of 1 equiv of molar ratio of HC(OMe)3 to remove
traces of water present if any (method B). For Cope
rearrangement to occur, the basic requirement is proxim-
ity of the two double bonds involved in the reaction. Thus,
IMDA adducts 18e-20e did not undergo Cope re-
arrangement as predicted, in view of their anti-stereo-
chemistry. To make the whole transformation simple, the
crude Diels-Alder reaction mixtures were concentrated
using a Kugelrohr apparatus after the usual workup and
the residues were dissolved in mesitylene and heated to
200-250 °C (method C) to obtain decalins as sole
products in high yields (Table 1). Surprisingly, the
oxatricyclic compound 18c did not undergo Cope re-
arrangement in method B. Unlike anionic oxy-Cope
rearrangement, Cope rearrangement is a reversible reac-
tion. During the course of reaction, the equilibrium shifts
toward the thermodynamically more stable product. The
oxatricyclic compound 18c is presumably more stable
than 21c, and consequently, we could not observe any
21c when subjected to the usual Cope rearrangement
conditions. To check our reasoning and the possible
presence of 21c during the course of above reaction, we
(3) The absence of substitution at an oxidation-prone
site, C-4, of these 2-methoxyphenols furnished lower
yields of the desired products along with the concomitant
production of side products (Table 2, 2-methoxyphenols
4-8). At this point we are unable to explain the reaction
of dienol 9c with 2-methoxyphenols 5-8 which provided
only messy noncharactarizable reaction products.
(4) In a nutshell, from the foregoing discussion, we can
propose that the optimum dienophilicity and high selec-
tivity of MOB can be obtained through constellation of
an electron-withdrawing group at position 4 of the 2,4-
cyclohexadienone unit and an alkyl group at position 5
of the 2,4-dienol (Table 1, entry 2).
(b) Structural Determination of Products. The
structures of all of the new compounds were established
by using spectroscopic methods including IR, 1H and 13
C
NMR, and low and high-resolution mass spectroscopy.
Elemental analyses were conducted only for the solid
compounds 19b and 19d and could obtain satisfactory
results. For most of the adducts in both of their low-
resolution and high-resolution mass spectra recorded in
electron impact mode (70 eV), the peaks corresponding
to the molecular ion could not be seen; instead, the peaks
corresponding to M+ - 28 were observed indicating the
facile extrusion of CO from the molecular ions. The IR
spectra of all the cycloadducts showed strong absorptions
at 1730-1749 cm-1, characteristic of the carbonyl group
adjacent to the R-methoxy and cyclic ether functionality.15
1
checked the H NMR of crude reaction mixture of 18c
when subjected to Cope reaction conditions for 2, 4, and
8 h but failed to observe any 21c, and hence, we propose
compound 18c to be more favorable and thermodynami-
cally more stable compound. To confirm our analysis that
18c is more stable, when cis-decalin 21c was heated at
200 °C for 8 h, oxatricyclic compound 18c could be
isolated in 88% yield suggesting that indeed 18c is more
stable than 21c. A similar fate was observed with
compound 26b, which could not undergo Cope rearrange-
ment to provide compound 31b. In a special case when
compound 19c was heated to 200 °C in mesitylene for 8
h, a mixture of 22c and 19c in a 1:1 ratio was obtained.
To verify the presence of 19c in the reaction is from the
reverse Cope rearrangement, compound 22c was heated
to 200 °C in mesitylene for 8 h again only to observe 1:1
mixture of 22c and 19c confirming the usual trend of
Cope rearrangement.
1
The H NMR (400 MHz) spectra of the crude reaction
mixtures resulted from the IMDA reactions of the MOBs
did not show the peaks corresponding to the other
isomeric cycloadducts indicating that the cycloaddition
took place in a highly regio- and stereoselective manner.
The regio- and stereochemical assignments of the oxatri-
cyclic compounds were made by comparing the coupling
patterns and coupling constants of the various protons
with those of the analogous IMDA adducts, whose regio-
and stereochemistry were earlier determined unambigu-
ously in our laboratories.15 In addition, the stereochem-
istry of the cis-decalins 22b, and 22d were further
confirmed with the help of difference in nuclear Over-
hauser enhancement (NOE) experiments (Chart 2). In
the case of 22b, saturation of bridged methyl protons
gave rise to an increase in the signal intensity of Hb
(0.8%) and He (1.6%) that proves their assigned stereo-
chemistry with respect to the bridged methyl group, while
saturation of Hd brought about significant NOE in the
He (3.5%), similarly saturation of He gave rise to en-
hancement in the signal intensity of Hd (4.2%). Thus it
The strain imparted by the tricyclo[4.3.1.03,7] system
in the adducts 24b, 25b, 27b, and 28b is diminished after
the smooth Cope rearrangement to provide the cis-
decalins 26b, 30b, 32b, and 33b, respectively (Table 2).
It is noteworthy that the thermal transformations of the
J. Org. Chem, Vol. 70, No. 23, 2005 9161

Hsu et al.
CDCl3) δ 17.8, 41.3, 43.1, 46.0, 51.0, 52.2, 53.0, 73.4, 98.2,
127.3, 130.4, 130.5, 137.7, 164.3, 198.8; MS (70 eV) m/z
(relative intensity) 250 (M+ - CO, 22), 235 (10), 219 (5), 203
(12), 59 (80), 186 (25), 158 (53), 129 (6), 115 (73), 91 (100);
HRMS (EI) calcd for C15H18O5 (M+) 278.1154, found 278.1149.
cycloadducts examined are in conformity with the general
tendency of 1,5-dienes toward Cope rearrangement.22-24
Conclusion
Ethyl
(E)-3-{(1R*,2S*,3S*,6R*,7R*)-6-methoxy-8-
In summary, we have presented herein the dual
behavior of MOBs in the IMDA reactions with a series
of examples. A general and short route (one or two pots)
to highly functionalized cis-decalins with complete ste-
reocontrol up to five stereocenters is developed. Our
methodology demonstrates the utilization of commer-
cially available or easily accessible 2-methoxyphenols in
the synthesis of potentially useful cis-decalins. The
observed experimental results led us to derive some
empirical rules regarding the variation of the diene and
dienophilic characters of MOBs with their substitution
pattern as well as the structure of the added dienol in
the IMDA reactions. The cycloadducts obtained from the
dienic MOB and dienophilic tether smoothly underwent
the Cope rearrangement to provide the highly function-
alized cis-decalins. As exemplified, biologically active
marine metabolites (()-xestoquinone and its 9,10-meth-
oxy derivatives were synthesized by this methodology.13c
Heterocycles related to viridin were also synthesized on
the same lines.18b This methodology brings the structur-
ally complex natural products within relatively simple
reach. Extension of this protocol in the synthesis of
decalin-based natural products is currently in progress
in our laboratories.
(methoxycarbonyl)-10-oxo-5-oxatricyclo[4.3.1.03,7]dec-8-
en-2-yl}-2-propenoate (18c): colorless liquid; IR (film) 2953,
1753, 1714, 1650, 1436, 1258, 1037 cm-1; 1H NMR (400 MHz,
CDCl3) δ 1.27 (t, J ) 6.8 Hz, 3H), 2.44 (apparent dd, J ) 1.6,
4.4 Hz, 1H), 2.96 (apparent dd, J ) 2.4, 8.6 Hz, 1H), 3.42 (dd,
J ) 2.8, 6.8 Hz, 1H), 3.50 (s, 3H), 3.80 (s, 3H), 3.89 (d, J ) 7.6
Hz, 1H), 4.06 (dd, J ) 1.6, 8.4 Hz, 1H), 4.10-4.30 (m, 3H),
5.84 (d, J ) 15.6 Hz, 1H), 6.60 (dd, J ) 8.6, 15.6 Hz, 1H), 7.15
(dd, J ) 2.0, 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.2,
41.6, 42.4, 45.2, 51.2, 51.5, 52.3, 60.7, 73.1, 99.2, 122.9, 133.4,
136.6, 146.4, 164.0, 165.7, 198.3; MS (70 eV) m/z (relative
intensity) 264 (M+ - CO, 100), 250 (10), 234 (41), 218 (7), 189
(59), 177 (11), 159 (64), 145 (64), 130 (42), 124 (20); HRMS
(EI) calcd for C17H20O7 336.1210, found 336.1209.
Methyl (1S*,3R*,6R*,7S*,10S*)-3-methoxy-6-methyl-2-
oxo-10-ethenyl-4-oxatricyclo[4.3.1.03,7]dec-8-ene-8-car-
boxylate (18d): colorless liquid; IR (film) 2950, 1748, 1740,
1620, 1430, 1012 cm-1; H NMR (400 MHz, CDCl3) δ 0.95 (s,
1
3H), 2.83 (dd, J ) 2.6, 9.6 Hz, 1H), 3.32 (dd, J ) 2.6, 6.8 Hz,
1H) 3.48 (s, 3H), 3.70 (d, J ) 1.6 Hz, 1H), 3.78 (s, 3H), 3.80 (d,
J ) 8.0 Hz, 1H), 3.86 (d, J ) 8.0 Hz, 1H), 5.03 (d, J ) 10.0 Hz,
1H), 5.06 (d, J ) 17.4 Hz, 1H), 5.44 (ddd, J ) 9.6, 10.0, 17.4
Hz, 1H), 7.21 (dd, J ) 2.0, 6.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 18.7, 46.4, 48.2, 50.8, 51.0, 52.2, 53.7, 80.6, 99.6,
117.7, 132.7, 135.7, 137.7, 164.4, 199.0; MS (70 eV) m/z
(relative intensity) 250 (M+ - CO, 100), 235 (60), 218 (27),
209 (13), 203 (60), 190 (72), 177 (22), 159 (34), 149 (22), 138
(13), 129 (24); HRMS (EI) calcd for C15H18O5 278.1154, found
278.1133.
Experimental Section
Methyl (1S*,3R*,6R*,7S*,10S*)-3-methoxy-2-oxo-10-
ethenyl-4-oxatricyclo[4.3.1.03,7]dec-8-ene-8-carboxylate
(18e): colorless liquid; IR (film) 2988, 1747, 1716, 1628, 1438,
1263, 1044 cm-1; 1H NMR (400 MHz, CDCl3) δ 2.47 (apparent
dd, J ) 8.2, 9.6 Hz, 1H), 2.56 (ddt, J ) 3.6, 3.8, 9.6 Hz, 1H),
3.24 (dd, J ) 1.6, 7.0 Hz, 1H), 3.50 (s, 3H), 3.79 (s, 3H), 3.97
(dd, J ) 3.6, 8.4 Hz, 1H), 3.99 (dd, 3.6, 8.4 Hz, 1H), 4.05 (dd,
J ) 2.2, 6.2 Hz, 1H), 5.18 (d, J ) 17.0 Hz, 1H), 5.21 (d, J )
10.6 Hz, 1H), 5.72 (ddd, J ) 8.0, 10.6, 17.0 Hz, 1H) 7.29 (dd,
J ) 2.2, 7.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 38.5, 42.0,
42.3, 51.0, 51.3, 52.2, 67.7, 99.8, 118.1, 132.5, 135.1, 139.5,
164.4, 199.4; MS (70 eV) m/z (relative intensity) 236 (M+ - CO,
100), 235 (55), 221 (64), 204 (41), 159 (74), 182 (7), 177 (38),
161 (40), 145 (28), 117 (53); HRMS (EI) calcd for C14H16O5 (M+)
264.0998, found 264.0995.
Methyl (1S*,3R*,6R*,7S*,10R*)-3-methoxy-2-oxo-10-
ethenyl-4-oxatricyclo[4.3.1.03,7]dec-8-en-8-carboxylate
(18a): colorless liquid; IR (film) 2856, 1750, 1715, 1628, 1439,
1
1256, 1020 cm-1; H NMR (400 MHz, CDCl3) δ 2.38 (m, 1H),
2.80 (apparent d, J ) 7.8 Hz, 1H), 3.36 (dd, J ) 3.0, 7.2 Hz,
1H) 3.48 (s, 3H), 3.78 (s, 3H), 3.85 (d, J ) 8.4 Hz, 1H), 4.02
(dd, J ) 2.2, 4.4 Hz, 1H), 4.19 (dd, J ) 3.6, 8.4 Hz, 1H), 5.03
(dd, J ) 1.2, 10.6 Hz, 1H), 5.05 (dd, J ) 1.2, 16.6 Hz, 1H),
5.54 (ddd, J ) 7.8, 10.6, 16.6 Hz, 1H), 7.13 (dd, J ) 2.2, 7.2
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 41.5, 42.4, 46.6, 51.1,
52.2, 52.5, 73.4, 99.2, 116.4, 132.7, 137.4, 137.5, 164.2, 199.4;
MS (70 eV) m/z (relative intensity) 264 (M+, 4), 232 (90), 221
(5), 204 (84), 190 (69), 172 (77), 159 (30), 145 (100), 117 (82),
105 (17); HRMS (EI) calcd for C14H16O5 (M+) 264.0989, found
264.0975.
(1S*,3R*,6R*,7S*,10R*)-3-Methoxy-8-methyl-10-ethenyl-
Methyl (1S*,3R*,6R*,7S*,10S*)-3-methoxy-2-oxo-10-
[(E)-1-propenyl]-4- oxatricyclo[4.3.1.03,7]dec-8-ene-8-car-
boxylate (18b): colorless liquid; IR (film) 2943, 1748, 1716,
4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (19a): colorless liq-
uid; IR (film) 2983, 2908, 1741, 1639, 1443, 1261, 1088 cm-1
;
1H NMR (400 MHz, CDCl3) δ 1.92 (s, 3H), 2.31 (m, 1H), 2.70
(apparent d, J ) 7.8 Hz, 1H), 3.05 (dd, J ) 3.2, 7.0 Hz, 1H),
3.15 (dd, 2.0, 4.4 Hz, 1H), 3.51 (s, 3H), 3.84 (d, 8.2 Hz, 1H),
4.13 (d, J ) 3.6, 8.2 Hz, 1H), 4.98 (d, J ) 10.4 Hz, 1H), 5.02
(d, J ) 16.4 Hz, 1H), 5.61 (ddd, J ) 7.8, 10.4, 16.4 Hz, 1H),
5.77 (d, J ) 7.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 21.2,
42.7, 46.7, 47.7, 51.4, 73.7, 100.3, 115.5, 119.9, 138.7, 139.1,
200.8; MS (70 eV) m/z (relative intensity) 192 (M+ - CO, 47),
177 (5), 151 (5), 133 (36), 125 (64), 117 (58), 105 (62), 91 (100),
77 (42), 65 (31), 194 (9); HRMS (EI) calcd for C13H16O3 (M+)
220.1099, found 220.1103.
1439, 1255, 1110, 1069 cm-1 1H NMR (400 MHz, CDCl3) δ
;
1.64 (dd, J ) 1.4, 6.4 Hz, 1H), 2.34 (ddd, J ) 2.0, 3.6, 4.4 Hz,
1H), 2.78 (apparent d, J ) 8.4 Hz, 1H), 3.33 (dd, J ) 2.4, 5.2
Hz, 1H), 3.58 (s, 3H), 3.72 (s, 3H), 3.87 (d, J ) 8.0 Hz, 1H),
4.03 (dd, J ) 2.2, 4.4 Hz, 1H), 4.20 (dd, J ) 3.6, 8.0 Hz, 1H),
5.17 (ddd, J ) 1.4, 8.4, 13.3 Hz, 1H), 5.53 (dq, J ) 6.4, 13.3
Hz, 1H), 7.19 (dd, J ) 2.2, 6.8 Hz, 1H); 13C NMR (100 MHz,
(21) House, H. U.; Rasmussun, G. H. J. Org. Chem. 1961, 26, 4278.
(22) (a) Kato, N.; Kataoka, H.; Ohbuchi, S.; Tanaka, S.; Takashita,
H. J. Chem. Soc., Chem. Commun. 1988, 354. (b) Shea, K. J.; Philips,
R. B. J. Am. Chem. Soc. 1980, 102, 3156. (c) Shea, K. J.; Bergman, R.
G. J. Am. Chem. Soc. 1977, 99, 1499.
(23) Brown, J. M.; Golding, B. T.; Stofko, J. J., Jr. J. Chem. Soc.,
Chem. Commun. 1973, 319.
(24) (a) Tamaru, Y.; Harada, T.; Yoshida, Z. J. Am. Chem. Soc. 1980,
102, 2392. (b) Zieglar, F. E.; Piwinski, J. J. J. Am. Chem. Soc. 1979,
101, 1611. (c) Conia, J. M.; Sandre-Le, C. A. Tetrahedron Lett. 1962,
505. (d) Cope, A. C.; Hoyle, K. E.; Heyl, D. J. Am. Chem. Soc. 1941,
63, 1843.
(1S*,3R*,6R*,7S*,10R*)-3-Methoxy-8-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (19b): col-
orless solid; mp 70-71 °C (from EtOAc-hexanes); IR (film)
2945, 2883, 1743, 1683, 1440, 1022 cm-1; 1H NMR (400 MHz,
CDCl3) δ 1.57 (dd, J ) 1.8, 6.0 Hz, 3H), 1.86 (d, J ) 1.6 Hz,
3H), 2.17 (apparent ddd, J ) 1.6, 3.2, 4.4 Hz, 1H), 2.58
(apparent ddd, J ) 1.6, 2.8, 8.6 Hz, 1H), 2.94 (dd, J ) 2.8, 6.8
Hz, 1H), 3.05 (dd, J ) 2.8, 4.4 Hz, 1H), 3.45 (s, 3H), 3.76 (d, J
9162 J. Org. Chem., Vol. 70, No. 23, 2005

Dual Behavior of MOBs in IMDA Reactions
) 8.0 Hz, 1H), 4.05 (dd, J ) 3.2, 8.0 Hz, 1H), 5.19 (ddq, J )
1.8, 8.6, 14.8 Hz, 1H), 5.41 (dq, J ) 6.0, 14.8 Hz, 1H), 5.74
(ddq, J ) 1.6, 2.8, 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
17.8, 21.2, 43.3, 45.9, 47.6, 51.3, 51.9, 73.7, 100.2, 120.0, 126.1,
131.4, 138.8, 201.1; MS (70 eV) m/z (relative intensity) 206
(M+ - CO, 100), 159 (4), 147 (39), 125 (50), 119 (44), 105 (43),
91 (37), 77 (16), 59 (9), 39 (12); HRMS (EI) calcd for C13H18O2
(M+ - CO) 206.1307, found 206.1308. Anal. Calcd for C14H18O3:
C, 71.77, H, 7.74. Found: C, 71.68, H, 7.80.
(1S*,3R*,6R*,7S*,10R*)-8-(5,5-Dimethyl-1,3-dioxan-2-
yl)-3-methoxy-10-[(E)-1-propenyl]-4-oxatricyclo[4.3.1.03,7]-
dec-8-en-2-one (20b): colorless liquid; IR (film) 2920, 1746,
1464, 1391, 1187, 1103, 1024 cm-1;1H NMR (300 MHz, CDCl3)
δ 0.77 (s, 3H), 1.21 (s, 3H), 1.63 (dd, J ) 1.5, 6.7 Hz, 3H), 2.20-
2.40 (m, 1H), 2.68 (apparent d, J ) 8.6 Hz, 1H), 3.20 (dd, J )
3.0, 6.8 Hz, 1H), 3.40-3.60 (m, 2H), 3.52 (s, 3H), 3.66 (s, 3H),
3.84 (d, J ) 8.1 Hz, 1H), 4.16 (dd, J ) 3.3, 8.1 Hz, 1H), 4.96
(s, 1H), 5.24 (ddq, J ) 1.5, 8.6, 14.8 Hz, 1H), 5.50 (dq, J ) 6.7,
14.8 Hz, 1H), 6.19 (dd, J ) 1.8, 8.6 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 17.9, 21.8, 23.0, 30.1, 41.2, 43.6, 46.1, 50.4,
51.8, 73.5, 77.4 (CH2 × 2), 100.0, 109.3, 124.2, 126.5, 131.0,
139.5, 200.7; MS (70 eV) m/z (relative intensity) 333 (M+ - 1,
8), 305 (50), 275 (8), 249 (10), 206 (8), 146 (6), 126 (7), 114
(100); HRMS (EI) calcd for C19H26O5 (M+) 334.1782, found
334.1779.
Ethyl (E)-3-{(1R*,2S*,3S*,6R*,7R*)-8-(5,5-dimethyl-1,3-
dioxan-2-yl)-6-methoxy-10-oxo-5-oxatricyclo[4.3.1.03,7]dec-
8-en-2-yl}-2-propenoate (20c): colorless liquid; IR (film)
2959, 1748, 1715, 1650, 1464, 1029 cm-1; 1H NMR (400 MHz,
CDCl3) δ 0.68 (s, 3H), 1.14 (s, 3H), 1.22 (t, J ) 6.8 Hz, 3H),
2.30-2.40 (m, 1H), 2.83 (apparent d, J ) 8.6 Hz, 1H), 3.15
(dd, J ) 3.2, 6.8 Hz, 1H), 3.40-3.46 (m, 2H), 3.45 (s, 3H), 3.50-
3.70 (m, 2H), 3.63 (dd, J ) 1.8, 6.4 Hz, 1H), 3.77 (d, J ) 8.4
Hz, 1H), 4.00-4.20 (m, 3H), 4.89 (s, 1H), 5.73 (d, J ) 15.6 Hz,
1H), 6.13 (dd, J ) 1.8, 6.8 Hz, 1H), 6.65 (dd, J ) 8.6, 15.6 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 14.1, 21.7, 22.9, 30.1, 41.2,
42.7, 45.3, 50.1, 50.3, 52.3, 60.4, 73.1, 76.9, 77.1, 99.9, 122.4,
123.4, 140.3, 147.3, 166.0, 199.1; MS (70 eV) m/z (relative
intensity) 264 (M+ - CO, 100), 250 (10), 234 (41), 218 (7), 189
(59), 177 (11), 159 (64), 145 (64), 130 (42), 124 (20); HRMS
(EI) calcd for C21H28O7 (M+) 392.1836, found 392.1835.
Ethyl (E)-3-{(1R*,2S*,3S*,6R*,7R*)-6-methoxy-8-meth-
yl-10-oxo-5-oxatricyclo[4.3.1.03,7]dec-8-en-2-yl}-2-pro-
penoate (19c): colorless liquid; IR (film) 2951, 1744, 1716,
1648, 1451, 1286, 1032 cm-1 1H NMR (400 MHz, CDCl3) δ
;
1.91 (s, 3H), 1.25 (t, J ) 7.2 Hz, 3H), 2.83 (apparent d, J ) 8.8
Hz, 1H), 3.07 (dd, J ) 3.0, 6.2 Hz, 1H), 3.15 (apparent dd, J )
1.6, 3.6 Hz, 1H), 3.49 (s, 3H), 4.11 (dd, J ) 3.2, 8.6 Hz, 1H),
3.81 (d, J ) 8.6 Hz, 1H), 4.11 (dd, J ) 3.2, 8.6 Hz, 1H), 4.15
(q, J ) 7.2 Hz, 2H), 5.80 (d, J ) 6.2 Hz, 1H), 5.81 (d, J ) 6.2
Hz, 1H), 6.68 (dd, J ) 8.8, 15.2 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 14.2, 21.3, 42.5, 45.3, 47.8, 50.4, 51.5, 73.4, 100.0,
120.0, 122.1, 139.8, 149.7, 166.06, 166.08, 199.7; MS (70 eV)
m/z (relative intensity) 264 (M+-- CO, 100), 250 (10), 234 (41),
218 (7), 189 (59), 177 (11), 159 (64), 145 (64), 130 (42), 124
(20); HRMS (EI) calcd for C16H20O5 (M+) 292.1300, found
292.1301.
(1S*,3R*,6R*,7R*,10S*)-3-Methoxy-6,8-dimethyl-10-eth-
enyl-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (19d): colorless
solid; mp 122-123 °C (from EtOAc-hexanes); IR (film) 2955,
2876, 1732, 1630, 1436, 1042 cm-1; 1H NMR (400 MHz, CDCl3)
δ 0.94 (s, 3H), 1.90 (t, J ) 1.6 Hz, 3H), 2.71 (dd, J ) 2.6, 8.2
Hz, 1H), 2.80 (d, J ) 2.2 Hz, 1H), 3.00 (dd, J ) 2.6, 6.8 Hz,
1H), 3.50 (s, 3H), 3.76 (s, 2H), 5.00 (dd, J ) 2.6, 8.2 Hz, 1H),
5.07 (dd, J ) 1.6, 17.4 Hz, 1H), 5.55 (dd, J ) 8.2, 8.2, 17.4 Hz,
1H), 5.87 (ddd, J ) 1.6, 2.2, 6.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 18.7, 22.2, 46.5, 50.8, 51.3, 52.5, 54.8, 80.9, 100.7,
116.9, 120.0, 136.7, 139.1, 200.5; MS (70 eV) m/z (relative
intensity) 206 (M+ - CO, 50), 165 (21), 159 (9), 147 (100), 131
(62), 124 (38), 120 (10), 119 (48), 105 (25); HRMS (EI) calcd
for C14H18O3 234.1254, found 234.1257. Anal. Calcd for
C14H18O3: C, 71.77; H, 7.74. Found: C, 71.67; H, 7.81.
(1S*,3R*,6R*,7S*,10S*)-8-(5,5-Dimethyl-1,3-dioxan-2-
yl)-3-methoxy-6-methyl-10-ethenyl-4-oxatricyclo[4.3.1.03,7]-
dec-8-en-2-one (20d): colorless liquid; IR (film) 2948, 2882,
1732, 1674, 1460, 1014 cm-1 1H NMR (400 MHz, CDCl3) δ
;
0.72 (s, 3H), 0.95 (s, 3H), 1.19 (s, 3H), 2.75 (apparent d, J )
10.0 Hz, 1H), 3.12 (dd, J ) 2.4, 6.7 Hz, 1H), 3.32 (d, J ) 1.9
Hz, 1H), 3.46 (d, J ) 9.0 Hz, 2H), 3.49 (s, 3H), 3.63 (d, J ) 9.6
Hz, 2H), 3.80 (s, 2H), 4.91 (s, 1H), 4.99 (dd, J ) 1.2, 10.0 Hz,
2H) 5.04 (dd, J ) 1.2, 16.7 Hz, 1H), 5.52 (ddd, J ) 10.0, 10.0,
16.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 18.9, 21.8, 22.9,
30.1, 46.3, 48.2, 50.4, 51.2, 52.5, 77.3, 81.0, 99.72, 99.74, 100.6,
116.9, 124.3, 136.6, 140.1, 200.0; MS (70 eV) m/z (relative
intensity) 307 (66), 306 (100), 291 (14), 274 (17), 248 (14), 220
(62), 205 (7), 193 (32), 175 (12), 133 (18); HRMS (EI) calcd for
C19H26O5 (M+) 334.1780, found 334.1795.
(1S*,3R*,6R*,7S*,10S*)-3-Methoxy-8-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (19e): col-
orless liquid; IR (film) 2940, 1742, 1638, 1441, 1325, 1169, 1084
1
cm-1; H NMR (400 MHz, CDCl3) δ 1.89 (d, J ) 1.8 Hz, 3H),
2.42 (apparent dd, J ) 8.4, 10.0 Hz, 1H), 2.51 (ddd, J ) 3.2,
3.6, 10.0 Hz, 1H), 2.91 (dd, J ) 1.6, 6.8 Hz, 1H), 3.12 (dd, J )
2.0, 4.0 Hz, 1H), 3.51 (s, 3H), 3.86 (dd, J ) 3.2, 8.4 Hz, 1H),
3.89 (d, J ) 8.4 Hz, 1H), 5.14 (dd, J ) 0.4, 9.4 Hz, 1H), 5.13
(dd, J ) 0.4, 18.0 Hz, 1H), 5.73 (ddd, J ) 8.0, 9.4, 18.0 Hz,
1H), 5.96 (ddd, J ) 1.8, 2.0, 6.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 21.3, 38.8, 43.5, 48.3, 50.3, 51.4, 68.0, 100.9, 117.1,
123.2, 136.4, 138.9, 200.8; MS (70 eV) m/z (relative intensity)
220 (M+, 2), 192 (100), 177 (14), 164 (33), 159 (8), 145 (5), 133
(60), 124 (18), 117 (25), 105 (12); HRMS (EI) calcd for C13H16O3
(M+) 220.1099, found 220.1104.
(1S*,3R*,6R*,7S*,10S*)-8-(5,5-Dimethyl-1,3-dioxan-2-
yl)-3-methoxy-10-ethenyl-4-oxatricyclo[4.3.1.03,7]dec-8-
en-2-one (20e): colorless liquid; IR (film) 2928, 1745, 1640,
1
1487, 1100, 1012 cm-1; H NMR (400 MHz, CDCl3) δ 0.74 (s,
3H), 1.21 (s, 3H), 2.45 (apparent dd, J ) 8.0, 10.0 Hz, 1H)
2.52 (1H, ddd, J ) 3.2, 3.2, 10.0 Hz, 1H), 3.07 (dd, J ) 1.6, 6.8
Hz, 1H), 3.50 (s, 3H), 3.40-3.70 (m, 5H), 3.94 (d, J ) 3.2 Hz,
2H), 4.92 (s, 1H), 5.13 (d, J ) 16.8 Hz, 1H), 5.15 (d, J ) 10.2
Hz, 1H), 5.72 (ddd, J ) 8.0, 10.2, 16.8 Hz, 1H), 6.17 (dd, J )
1.6, 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 21.8, 23.0, 30.2,
39.1, 41.9, 43.1, 50.0, 50.4, 67.7, 77.1, 77.2, 100.2, 100.5, 117.1,
127.1, 136.0, 139.3, 200.2; MS (70 eV) m/z (relative intensity)
292 (M+, 100), 258 (8), 266 (8), 211 (10), 194 (9), 145(11), 133-
(2); HRMS (EI) calcd for C18H24O3 (M+) 292.1714, found
292.1658.
(1S*,3R*,6R*,7S*,10S*)-8-(5,5-Dimethyl-1,3-dioxan-2-
yl)-3-methoxy-10-ethenyl-4-oxatricyclo[4.3.1.03,7]dec-8-
en-2-one (20a): colorless liquid; IR (film) 2925, 1747, 1638,
1
1467, 1392, 1016 cm-1; H NMR (400 MHz, CDCl3) δ 0.76 (s,
3H), 1.24 (s, 3H), 2.38 (apparent d, J ) 2.8 Hz, 1H), 2.75
(apparent d, J ) 8.2 Hz, 1H), 3.19 (dd, J ) 3.2, 6.8 Hz, 1H),
3.53 (m, 5H), 3.60-3.70 (m, 3H), 3.86 (d, J ) 8.2 Hz, 1H), 4.18
(dd, J ) 3.6, 8.2 Hz, 1H), 4.96 (s, 1H), 5.03 (dd, J ) 1.6, 10.0
Hz, 1H), 5.06 (dd, J ) 1.6, 17.0 Hz, 1H), 5.64 (ddd, J ) 8.4,
10.0, 17.0 Hz, 1H), 6.19 (dd, J ) 1.6, 6.8 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 21.8, 23.0, 30.1, 41.2, 43.0, 46.8, 50.4, 51.2,
73.4, 77.1 (CH2 × 2), 100.0, 100.2, 115.8, 124.0, 138.2, 139.7,
200.3; MS (70 eV) m/z (relative intensity) 320 (M+, 4), 292 (5),
261 (8), 234 (3), 208 (10), 174 (8), 161 (4), 145 (9), 131 (3), 110
(100); HRMS (EI) calcd for C18H24O5 (M+) 320.1624, found
320.1614.
Methyl (2aR*,5aS*,8aR*,8bR*)-8a-methoxy-2a,5,5a,8,
8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-5a-car-
boxylate (21a): colorless liquid; IR (film) 2967, 1734, 1694,
1442, 1283, 1214, 1099, 1041 cm-1; 1H NMR (400 MHz, CDCl3)
δ 1.96 (ddd, J ) 1.6, 3.6, 16.8 Hz, 1H), 2.61 (ddd, J ) 6.0, 16.8
Hz, 1H), 3.15-3.20 (m, 1H), 3.27 (s, 3H), 3.41 (dd, J ) 1.6, 9.2
Hz, 1H), 3.72 (s, 3H), 3.80 (dd, J ) 2.8, 8.4 Hz, 1H), 4.13 (dd,
J ) 7.2, 8.4 Hz, 1H), 5.72 (dddd, J ) 1.2, 3.4, 5.8, 10.0 Hz,
1H), 5.81 (ddd, J ) 2.0, 4.0, 10.0 Hz, 1H), 6.09 (d, J ) 10.2
Hz, 1H), 6.96 (d, J ) 10.2 Hz, 1H); 13C NMR (100 MHz, CDCl3)
J. Org. Chem, Vol. 70, No. 23, 2005 9163

Hsu et al.
δ 35.3, 37.7, 47.6, 49.1, 50.3, 52.9, 73.2, 102.5, 124.5, 128.4,
130.1, 151.0, 173.7, 190.3; MS (70 eV) m/z (relative intensity)
264 (M+, 5), 249 (12), 232 (97), 221 (6), 204 (84), 190 (73), 172
(82), 159 (30), 145 (100), 117 (91); HRMS (EI) calcd for
C14H16O3 (M+) 264.0989, found 264.0988.
(ddd, J ) 3.0, 6.4, 9.6 Hz, 1H), 5.67 (ddd, J ) 2.0, 4.4, 9.6 Hz,
1H), 6.07 (d, J ) 10.4 Hz, 1H), 6.63 (d, J ) 10.4 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ 15.6, 28.8, 37.7, 39.0, 39.5, 51.1,
54.3, 71.5, 102.8, 127.9, 129.1, 133.9, 154.8, 192.2; MS (70 eV)
m/z (relative intensity) 234 (M+, 10), 206 (40), 191 (5), 175 (11),
161 (29), 131 (42), 115 (47), 91 (95), 79 (72), 39 (100); HRMS
(EI) calcd for C14H18O3, (M+) 234.1256, found 234.1255.
Ethyl (2aR*,5S*,5aR*,8aR*,8bR*)-8a-methoxy-5a-meth-
yl-8-oxo-2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isoben-
zofuran-5-carboxylate (22c): colorless liquid; IR (film) 2939,
1773, 1688, 1455, 1174, 1030 cm-1; 1H NMR (400 MHz, CDCl3)
δ 1.26 (t, J ) 7.2 Hz, 3H), 1.40 (s, 3H), 2.73 (dd, J ) 0.9, 10.5
Hz, 1H), 2.92 (dd, J ) 2.5, 5.2 Hz, 1H), 2.98 (apparent ddd, J
) 2.4, 3.0, 5.2 Hz, 1H), 3.41 (s, 3H), 3.58 (dd, J ) 6.0, 9.0 Hz,
1H), 4.20-4.40 (m, 3H), 5.76 (ddd, J ) 2.4, 5.2, 9.3 Hz, 1H),
5.88 (d, J ) 10.5 Hz, 1H), 6.00 (d, J ) 10.5 Hz, 1H), 6.86 (dd,
J ) 0.9, 10.5 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.2, 28.5,
38.5, 39.6, 51.5, 51.8, 54.0, 60.1, 70.6, 102.5, 127.5, 128.0, 131.3,
153.5, 172.3, 192.5; MS (70 eV) m/z (relative intensity) 292
(M+, 30), 264 (100), 234 (17), 219 (30), 210 (8), 204 (24), 186
(39), 176 (11), 158 (64), 145 (37); HRMS (EI) calcd for C16H20O5
(M+) 292.1311, found 292.1308.
(2aR*,5aR*,8aR*,8bS*)-8a-Methoxy-2a,5a-dimethyl-
2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (22d): colorless liquid; IR (film) 2926, 1738, 1690, 1455,
1042 cm-1; 1H NMR (400 MHz, CDCl3) δ 1.19 (s, 3H), 1.26 (s,
3H), 1.78 (apparent ddd, J ) 2.4, 2.8, 16.4 Hz, 1H), 1.99 (dd,
J ) 5.8, 16.4 Hz, 1H), 2.25 (d, J ) 1.6 Hz, 1H), 3.24 (s, 3H),
3.70 (d, J ) 8.4 Hz, 1H), 3.75 (d, J ) 8.4 Hz, 1H), 5.60 (dd, J
) 2.4, 10.0 Hz, 1H), 5.66 (ddd, J ) 2.8, 5.8, 10.0 Hz, 1H), 6.00
(d, J ) 10.0 Hz, 1H), 6.76 (d, J ) 10.0 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 26.3, 27.5, 35.2, 37.3, 42.7, 50.0, 60.5, 79.4,
103.9, 123.3, 127.1, 134.5, 160.0, 190.7; MS (70 eV) m/z
(relative intensity) 234 (M+, 15), 219 (29), 206 (37), 187 (34),
176 (48), 174 (62), 161 (100), 147 (43), 133 (45), 131 (40); HRMS
(EI) calcd for C14H18O3 (M+) 234.1256, found 234.1263.
Methyl (2aR*,5S*,5aR*,8aR*,8bR*)-8a-methoxy-5-meth-
yl-8-oxo-2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isoben-
zofuran-5a-carboxylate (21b): colorless liquid; IR (film)
2938, 1731, 1693, 1446, 1383, 1235, 1046 cm-1; 1H NMR (400
MHz, CDCl3) δ 1.11 (d, J ) 7.2 Hz, 3H), 2.71 (ddd, J ) 2.8,
4.6, 7.2 Hz, 1H), 3.00-3.12 (m, 1H), 3.31 (s, 3H), 3.43 (d, J )
10.0 Hz, 1H), 3.76 (dd, J ) 4.0, 8.8 Hz, 1H), 3.83 (s, 3H), 4.24
(dd, J ) 7.2, 8.8 Hz, 1H), 5.59 (ddd, J ) 2.8, 7.2, 9.0 Hz, 1H),
5.77 (ddd, J ) 2.4, 4.6, 9.0 Hz, 1H), 6.20 (d, J ) 10.4 Hz, 1H),
6.88 (d, J ) 10.4 HZ, 1H); 13C NMR (100 MHz, CDCl3) δ 15.9,
29.6, 37.8, 38.2, 51.0, 51.3, 51.4, 52.9, 71.0, 101.7, 129.4, 130.8,
132.6, 141.0, 174.5, 191.3; MS (70 eV) m/z (relative intensity)
278 (M+, 4), 263 (12), 247 (18), 219 (9), 159 (16), 131 (26), 99
(100), 91 (18), 81 (16), 59 (9); HRMS (EI) calcd for C15H18O5
(M+) 278.1154, found 278.1141.
5-Ethyl-5a-methyl (2aR*,5S*,5aS*,8aR*,8bR*)-8a-meth-
oxy-8-oxo-2a,5,5a,8a,8b-hexahydro-2H-benzo[cd]isoben-
zofuran-5,5a-dicarboxylate (21c): colorless liquid; IR (film)
2953, 1732, 1711, 1646, 1437, 1093 cm-1; 1H NMR (400 MHz,
CDCl3) δ 1.27 (t, J ) 6.8 Hz, 3H), 2.95-3.05 (m, 1H), 3.28 (dd,
J ) 0.8, 9.6 Hz, 1H), 3.32 (s, 3H), 3.65 (dd, J ) 2.8, 6.4 Hz,
1H), 3.72 (dd, J ) 4.8, 9.0 Hz, 1H), 3.80 (s, 3H), 4.20 (q, J )
6.8 Hz, 2H), 4.23 (dd, J ) 6.4, 9.0 Hz, 1H), 5.83 (ddd, J ) 2.8,
5.2, 9.4 Hz, 1H), 6.04 (ddd, J ) 3.2, 6.4, 9.4 Hz, 1H), 6.15 (d,
J ) 10.4 Hz, 1H), 6.69 (dd, J ) 0.8, 10.4 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 14.1, 38.9, 48.9, 49.5, 51.9, 52.0, 52.3, 61.6,
73.1, 101.7, 126.3, 130.3, 132.1, 145.6, 170.5, 173.8, 191.4; MS
(70 eV) m/z (relative intensity) 264 (M+ - CO, 100), 250 (10),
234 (41), 218 (7), 189 (59), 177 (11), 159 (64), 145 (64), 130
(42), 124 (20); HRMS (EI) calcd for C17H20O7 (M+) 336.1209,
found 336.1209.
Methyl (2aR*,5aS*,8aR*,8bR*)-8a-methoxy-2a-methyl-
8-oxo-2a,5,5a,8,8a, 8b-hexahydro-2H-benzo[cd]isobenzo-
furan-5a-carboxylate (21d): colorless liquid; IR (film) 2955,
(2aR*,5aS*,8aR*,8bR*)-5a-(5,5-Dimethyl-1,3-dioxan-2-
yl)-2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (23a): colorless liquid; IR (film) 2926, 1692, 1467, 1391,
1
1732, 1688, 1436, 1042 cm-1
;
1H NMR (400 MHz, CDCl3) δ
1210, 1034 cm-1; H NMR (400 MHz, CDCl3) δ 0.61 (s, 3H),
1.32 (s, 3H), 1.87 (ddd, J ) 2.2, 2.4, 16.4 Hz, 1H), 2.69 (ddd, J
) 2.6, 6.3, 16.4 Hz, 1H), 3.15 (d, J ) 2.4 Hz, 1H), 3.27 (s, 3H),
3.72 (s, 3H), 3.76 (d, J ) 8.8 Hz, 1H), 3.84 (d, J ) 8.8 Hz, 1H),
5.63 (dd, J ) 2.2, 9.6 Hz, 1H), 5.69 (ddd, J ) 2.6, 6.3, 9.6 Hz,
1H), 6.10 (d, J ) 10.4 Hz, 1H), 6.97 (d, J ) 10.4 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ 26.0, 34.5, 43.2, 47.8, 50.0, 52.8,
56.0, 80.5, 103.4, 123.0, 128.2, 136.4, 151.6, 173.7, 189.8; MS
(70 eV) m/z (relative intensity) 278 (M+, 13), 246 (93), 232 (8),
218 (34), 205 (40), 197 (24), 186 (100), 176 (39), 158 (72), 145
(70); HRMS (EI) calcd for C15H18O5 (M+) 278.1154, found
278.1144.
1.07 (s, 3H), 1.75 (dd, J ) 2.6, 15.2 Hz, 1H), 2.34 (dd, J ) 3.6,
15.2 Hz, 1H), 2.87 (apparent dd, J ) 2.8, 6.8 Hz, 1H), 2.98 (d,
J ) 8.0 Hz, 1H), 3.18 (s, 3H), 3.30 (d, J ) 10.0 Hz, 2H), 3.40-
3.60 (m, 2H), 3.71 (dd, J ) 2.8, 8.8 Hz, 1H), 4.02 (dd, J ) 6.8,
8.8 Hz, 1H), 4.26 (s, 1H), 5.63-5.66 (m, 2H), 6.00 (d, J ) 10.0
Hz, 1H), 6.94 (d, J ) 10.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 30.2, 30.7, 37.6, 43.5, 47.5, 50.5, 72.8, 77.3 (CH2 × 2), 102.7,
103.1, 125.7, 127.8, 130.0, 153.8, 191.3; MS (70 eV) m/z
(relative intensity) 320 (M+, 26), 319 (26), 292 (30), 277 (3),
261 (24), 208 (32), 193 (9), 175 (32), 144 (25), 115 (100); HRMS
(EI) calcd for C18H24O5 (M+) 320.1624, found 320.1626.
(2aR*,5aR*,8aR*,8bR*)-8a-Methoxy-5a-methyl-2a,5,
5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (22a): colorless liquid; IR (film) 2923, 1732, 1669, 1445,
(2aR*,5S*,5aR*,8aR*,8bR*)-5a-(5,5-Dimethyl-1,3-dioxan-
2-yl)-8a-methoxy-5-methyl-2a,5,5a,8,8a,8b-hexahydro-2H-
benzo[cd]isobenzofuran-8-one (23b): colorless liquid; IR
1
1
1262, 1065 cm-1; H NMR (400 MHz, CDCl3) δ 1.13 (s, 3H),
(film) 1692 cm-1; H NMR (300 MHz, CDCl3) δ 0.66 (s, 3Η),
1.74 (d, J ) 15.8 Hz, 1H), 1.90 (dd, J ) 3.2, 15.8 Hz, 1H), 2.49
(d, J ) 9.6 Hz, 1H), 2.94 (apparent dd, J ) 7.6, 9.6 Hz, 1H),
3.21 (s, 3H), 3.66 (dd, J ) 3.6, 8.8 Hz, 1H), 4.03 (dd, J ) 7.6,
8.8 Hz, 1H), 5.60-5.70 (m, 2H), 5.92 (d, J ) 10.0 Hz, 1H), 6.61
(d, J ) 10.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 28.3, 35.3,
37.3, 37.7, 50.5, 53.4, 72.7, 102.9, 125.7, 127.0, 129.4, 159.1,
191.4; MS (70 eV) m/z (relative intensity) 220 (M+, 11), 205
(90), 188 (36), 173 (10), 160 (58), 151 (26), 147 (100), 137 (5),
117 (57), 105 (48); HRMS (EI) calcd for C13H17O3 (M+)
220.1099, found 220.1095.
0.90 (d, J ) 7.2 Hz, 3H), 1.13 (s, 3H), 2.54 (apparent ddd, J )
2.0, 7.2, 9.2, 1H), 2.80-3.00 (m, 1H), 3.13 (d, J ) 9.2 Hz, 1H),
3.24 (s, 3H), 3.35 (dd, J ) 3.6, 11.0 Hz, 2H), 3.61 (dd, J ) 3.6,
11.0 Hz, 2H), 3.78 (dd, J ) 2.0, 8.4 Hz, 1H), 4.05 (dd, J ) 7.2,
8.4 Hz, 1H), 4.38 (s, 1H), 5.61 (m, 2H), 6.16 (d, J ) 9.6 Hz,
1H), 6.82 (d, J ) 9.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
17.7, 21.6, 23.1, 30.2, 32.2, 37.5, 47.3, 47.7, 50.6, 72.5, 77.6
(CH2 × 2), 103.1, 103.4, 128.9, 129.3, 133.2, 150.4, 191.2; MS
(70 eV) m/z (relative intensity) 334 (M+, 2), 305 (50), 272 (4),
251 (6), 205 (6), 172 (4), 158 (4), 144, (3), 114 (100); HRMS
(EI) calcd for C19H26O5 (M+) 334.1782, found 334.1783.
(2aR*,5S*,5aS*,8aR*,8bR*)-8a-Methoxy-5,5a-dimethyl-
2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (22b): colorless liquid; IR (film) 2961, 2874, 1736, 1614,
Ethyl (2aR*,5S*,5aS*,8aR*,8bR*)-5a-(5,5-dimethyl-1,3-
dioxanyl-2-yl)-8a-methoxy-2a-methyl-8-oxo-2a,5,5a,8,
8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-5-carboxy-
late (23c): colorless liquid; IR (film) 2931, 1719, 1469, 1032
1439, 1282, 1209, 1026 cm-1 1H NMR (400 MHz, CDCl3) δ
;
1.07 (d, J ) 7.2 Hz, 3H), 1.32 (s, 3H), 2.00-2.20 (m, 1H), 2.66
(d, J ) 10.0 Hz, 1H), 2.85-3.05 (m, 1H), 3.37 (s, 3H), 3.67
(dd, J ) 4.4, 8.8 Hz, 1H), 4.17 (dd, J ) 8.0, 8.8 Hz, 1H), 5.61
1
cm-1; H NMR (400 MHz, CDCl3) δ 0.69 (s, 3H), 1.18 (s, 3H),
1.25 (t, J ) 7.2 Hz, 3H), 2.80-2.90 (m, 1H), 3.23 (d, J ) 1.2
9164 J. Org. Chem., Vol. 70, No. 23, 2005

Dual Behavior of MOBs in IMDA Reactions
Hz, 1H), 3.34 (s, 3H), 3.39 (d, J ) 11.6 Hz, 3H), 3.62 (dd, J )
2.4, 8.4 Hz, 1H), 3.64 (dd, J ) 2.8, 6.4 Hz, 1H), 3.84 (dd, J )
3.2, 8.8 Hz, 1H), 4.00-4.20 (m, 3H), 4.53 (s, 1H), 5.70-5.90
(m, 2H), 6.12 (d, J ) 10.4 Hz, 1H), 6.93 (d, J ) 10.4 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ 14.1, 21.7, 23.2, 30.2, 39.4, 45.2,
47.8, 48.3, 51.2, 60.9, 71.5, 77.4, 77.5, 102.7, 103.8, 127.3, 129.6,
132.3, 147.9, 172.5, 192.3; MS (70 eV) m/z (relative intensity)
392 (M+, 6), 364 (20), 319 (12), 277 (7), 233 (8), 210 (11), 173
(16), 145 (15), 115 (100), 69 (35); HRMS (EI) calcd for C21H28O7
(M+) 392.1835, found 392.1831.
(2aR*,5aS*,8aR*,8bR*)-5a-(5,5-Dimethyl-1,3-dioxan-2-
yl)-8a-methoxy-2a-methyl-2a,5,5a,8,8a,8b-hexahydro-2H-
benzo[cd]isobenzofuran-8-one (23d): colorless liquid; IR
(film) 3026, 2955, 1688, 1606, 1436, 1042 cm-1; 1H NMR (400
MHz, CDCl3) δ 0.70 (s, 3H), 1.16 (s, 3H), 1.22 (s, 3H), 1.69 (d,
J ) 15.8 Hz, 1H), 2.45 (dd, J ) 4.4, 15.8 Hz, 1H), 2.81 (s, 1H),
3.23 (s, 3H), 3.36 (d, J ) 11.6 Hz, 2H), 3.64 (d, J ) 11.6 Hz,
1H), 3.73 (d, J ) 8.4 Hz, 2H), 3.80 (d, J ) 8.4 Hz, 2H), 4.37 (s,
1H), 5.62 (s, 1H), 6.08 (d, J ) 10.4 Hz, 1H), 7.24 (d, J ) 10.4
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 21.2, 21.6, 23.1, 25.7,
30.2, 31.0, 42.8, 43.5, 50.0, 54.0, 77.4, 79.4, 101.6, 104.2, 123.5,
127.5, 135.1, 154.5, 190.9; MS (70 eV) m/z (relative intensity)
333 (M+, 24), 319 (12), 303 (24), 289 (4), 275 (15), 217 (12),
208 (25), 189 (24), 175 (18), 115 (100); HRMS (EI) calcd for
C19H26O5 (M+) 334.1780, found 334.1776.
(1R*,3R*,6S*,7S*,10S*)-3-Methoxy-10-vinyl-4-oxatri-
cyclo[4.3.1.03,7]dec-8-en-2-one (24a): colorless liquid; IR
(film) 2949, 1745, 1460, 1023 cm-1; 1H NMR (400 MHz, CDCl3)
δ 2.29 (ddd, J ) 1.6, 3.6, 4.4 Hz, 1H), 2.72 (apparent d, J )
8.0 Hz, 1H), 3.17 (ddd, J ) 1.6, 2.8, 6.4 Hz, 1H), 3.32 (ddd, J
) 1.6, 4.4, 6.4 Hz, 1H), 3.50 (s, 3H), 3.83 (d, J ) 8.0 Hz, 1H),
4.13 (dd, J ) 3.6, 8.0 Hz, 1H), 5.01 (d, J ) 9.8 Hz, 1H), 5.05
(d, J ) 17.0 Hz, 1H), 5.63 (ddd, J ) 8.0, 9.8, 17.0 Hz, 1H),
6.18 (ddd, J ) 1.6, 6.4, 8.0 Hz, 1H), 6.25 (ddd, J ) 1.6, 6.4, 8.0
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 43.06, 43.09, 46.4, 51.4,
51.9, 73.6, 99.9, 115.7, 128.3, 129.5, 138.4, 200.7; MS (70 eV)
m/z (relative intensity) 178 (M+ - CO, 76), 159 (12), 145 (9),
124 (18), 119 (88), 105 (31), 93 (12), 91 (100), 77 (47), 41 (44);
HRMS (EI) calcd for C11H14O2 (M+ - CO) 178.0994, found
178.0987.
(1R*,3R*,6S*,7S*,10S*)-3-Methoxy-1-methyl-10-vinyl-4-
oxatricyclo[4.3.1.03,7]dec-8-en-2-one (25a): colorless liquid;
IR (film) 2971, 1741, 1638, 1453, 1054 cm-1 1H NMR (400
;
MHz, CDCl3) δ 1.22 (s, 3H), 2.26 (apparent d, J ) 8.8 Hz, 1H),
2.31 (ddd, J ) 1.6, 3.6, 4.6 Hz, 1H), 3.29 (ddd, J ) 1.4, 4.6, 6.4
Hz, 1H), 3.49 (s, 3H), 3.82 (d, J ) 8.0 Hz, 1H), 4.12 (dd, J )
3.6, 8.0 Hz, 1H), 5.04 (d, J ) 16.0 Hz, 1H), 5.05 (d, J ) 10.8
Hz, 1H), 5.62-5.64 (m, 1H), 5.77 (dd, J ) 1.4, 8.0 Hz, 1H),
6.23 (dd, J ) 6.4, 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
15.3, 42.3, 45.2, 50.8, 51.3, 53.2, 73.6, 100.2, 116.8, 129.0, 136.6,
137.6, 202.2; MS (70 eV) m/z (relative intensity) 220 (M+, 8),
192 (28), 189 (25), 162 (84), 147 (62), 131 (38), 117 (44), 91
(100), 77 (56), 65 (35); HRMS (EI) calcd for C13H16O3 (M+)
220.1100, found 220.1102.
(1R*,3R*,6S*,7S*10S*)-3-Methoxy-1-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (25b): col-
1
orless liquid; IR (film) 2969, 1741, 1450, 1039 cm-1; H NMR
(400 MHz, CDCl3) δ 1.17 (s, 3H), 1.63 (dd, J ) 1.6, 6.4 Hz,
3H), 2.19 (apparent d, J ) 9.6 Hz, 1H), 2.26 (ddd, J ) 1.6, 3.0,
4.4 Hz, 1H), 3.26 (ddd, J ) 1.6, 4.4, 6.0 Hz, 1H), 3.47 (s, 3H),
3.80 (d, J ) 8.0 Hz, 1H), 4.09 (dd, J ) 3.6, 8.0 Hz, 1H), 5.14
(ddq, J ) 1.6, 9.6, 15.0 Hz, 1H), 5.44 (dq, J ) 6.4, 15.0 Hz,
1H), 5.76 (d, J ) 8.0 Hz, 1H), 6.20 (dd, J ) 6.8, 8.0 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ 15.4, 17.8, 42.1, 45.5, 51.0, 51.2,
52.1, 73.6, 100.2, 127.5, 128.7, 130.2, 133.7, 202.5; MS (70 eV)
m/z (relative intensity) 206 (M+ - CO, 100), 175 (6), 147 (41),
131 (37), 119 (57), 105 (63), 91 (70), 77 (29), 59 (19), 39 (28);
HRMS (EI) calcd for C14H18O3 (M+) 234.1256, found 234.1241.
Methyl (1S*,3R*,6R*,7S*,10S*)-3-methoxy-2-oxo-10-
[(E)-1-propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-ene-1-car-
boxylate (26b): colorless liquid; IR (film) 2953, 1754, 1733,
1675, 1438, 1016 cm-1; 1H NMR (400 MHz, CDCl3) δ 1.57 (dd,
J ) 1.6, 6.8 Hz, 3H), 2.20-2.40 (m, 1H), 3.09 (apparent d, J )
9.0 Hz, 1H), 3.27 (ddd, J ) 1.6, 4.4, 6.4 Hz, 1H), 3.50 (s, 3H),
3.78 (s, 3H), 3.90 (dd, J ) 8.0, 8.2 Hz, 1H), 4.13 (dd, J ) 3.2,
8.2 Hz, 1H), 5.10 (ddq, J ) 1.6, 9.0, 15.2 Hz, 1H), 5.51 (dd,
6.8, 15.2 Hz, 1H), 6.26 (dd, J ) 6.4, 8.4 Hz, 1H), 6.55 (dd, J )
1.6, 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 17.9, 43.5, 44.5,
48.8, 51.9, 52.4, 64.3, 73.5, 99.9, 128.0, 128.5, 128.7, 128.8,
168.7, 196.1; MS (70 eV) m/z (relative intensity) 278 (M+, 10),
250 (100), 247 (22), 215 (54), 191 (33), 159 (49), 131 (59), 115
(22), 91 (24), 59 (9); HRMS (EI) calcd for C15H18O5 (M+)
278.1155, found 278.1160.
(1R*,3R*,6S*,7S*,10S*)-3-Methoxy-6-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (24b): col-
orless liquid; IR (film) 3063, 2950, 1744, 1686, 1461, 1094 cm-1
;
1H NMR (400 MHz, CDCl3) δ 1.62 (dd, J ) 1.6, 6.8 Hz, 3H),
2.30-2.45 (m, 1H), 2.66 (apparent d, J ) 8.2 Hz, 1H), 3.11
(ddd, J ) 1.6, 3.2, 6.4 Hz, 1H), 3.30 (ddd, J ) 2.2, 4.4, 6.4 Hz,
1H), 3.49 (s, 3H), 3.81 (d, J ) 8.0 Hz, 1H), 4.11 (dd, J ) 4.0,
8.0 Hz, 1H), 5.23 (ddd, J ) 1.6, 8.2, 15.8 Hz, 1H), 5.49 (dq, J
) 6.8, 15.8 Hz, 1H), 6.18 (ddd, J ) 2.2, 6.4, 8.4 Hz, 1H), 6.23
(ddd, J ) 1.6, 6.4, 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
17.8, 43.0, 43.7, 45.7, 51.3, 52.4, 73.7, 100.0, 126.4, 128.4, 129.3,
131.2, 201.1; MS (70 eV) m/z (relative intensity) 192 (M+ - CO,
68), 174 (4), 163 (4), 145 (4), 117 (50), 105 (89), 91 (100), 77
(36), 65 (22); HRMS (EI) calcd for C12H16O2 (M+ - CO)
192.1150, found 192.1130.
(1S*,3R*,6S*,7S*,10S*)-3-Methoxy-9-methyl-10-vinyl-4-
oxatricyclo[4.3.1.03,7]dec-8-en-2-one (27a): colorless liquid;
1
IR (film) 2957, 1742, 1672, 1654, 1442, 1026 cm-1; H NMR
(400 MHz, CDCl3) δ 1.81 (d, J ) 1.6 Hz, 3H), 2.28 (apparent
dd, J ) 2.6, 4.4 Hz, 1H), 2.72 (apparent dd, J ) 2.6, 8.0 Hz,
1H), 2.94 (dd, J ) 2.0, 2.6 Hz, 1H), 3.23 (dd, J ) 4.4, 6.4 Hz,
1H), 3.49 (s, 3H), 3.82 (d, J ) 8.0 Hz, 1H), 4.11 (dd, J ) 2.6,
8.0 Hz, 1H), 5.02 (d, J ) 10.2 Hz, 1H), 5.07 (d, J ) 17.0 Hz,
1H), 5.60 (ddd, J ) 8.0, 10.2, 17.0 Hz, 1H), 5.84 (ddq, J ) 1.6,
2.0, 6.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 21.4, 41.9, 42.8,
46.1, 50.9, 57.2, 73.5, 100.1, 115.6, 121.2, 137.2, 137.9, 200.3;
MS (70 eV) m/z (relative intensity) 192 (M+ - CO, 78), 187
(7), 153 (10), 138 (14), 134 (100), 131 (23), 125 (40), 105 (62),
91 (69), 77 (42); HRMS (EI) calcd for C12H16O2 (M+ - CO)
192.1150, found 192.1148.
Ethyl (E)-3-[(1R*,2S*,3S*,6R*,7S*)-6-methoxy-10-oxo-
5-oxatricyclo[4.3.1.03,7]dec-8-en-2-yl]-2-propenate (24c):
colorless liquid; IR (film) 2953, 1741, 1719, 1648, 1023 cm-1
;
1H NMR (400 MHz, CDCl3) δ 1.27 (t, J ) 7.2 Hz, 3H), 2.36
(apparent d, J ) 4.4 Hz, 1H), 2.88 (apparent d, J ) 8.4 Hz,
1H), 3.21 (ddd, J ) 1.6, 2.8, 6.6 Hz, 1H), 3.37 (ddd, J ) 1.4,
4.4, 6.8 Hz, 1H), 3.51 (s, 3H), 3.83 (d, J ) 8.2 Hz, 1H), 4.17 (q,
J ) 7.2 Hz, 2H), 5.80-5.85 (m, 2H), 6.21 (ddd, J ) 1.6, 6.8,
8.0 Hz, 1H), 6.31 (ddd, J ) 1.4, 6.6, 8.0 Hz, 1H), 5.76 (dd, J )
8.4, 15.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.2, 42.9,
43.1, 45.0, 50.9, 51.5, 60.6, 73.3, 99.8, 122.4, 128.0, 130.2, 147.5,
166.0, 199.6; MS (70 eV) m/z (relative intensity) 278 (M+, 1),
250 (21), 236 (12), 163 (27), 145 (39), 117 (59), 91 (82), 77 (37),
43 (48), 18 (100); HRMS (EI) calcd for C15H18O5 (M+) 278.1146,
found 278.1154.
(1S*,3R*,6S*,7S*,10S*)-3-Methoxy-9-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-en-2-one (27b): col-
1
orless liquid; IR (film) 2953, 1741, 1440, 1022 cm-1; H NMR
(400 MHz, CDCl3) δ 1.61 (dd, J ) 1.2, 6.4 Hz, 3H), 1.80 (d, J
) 1.6 Hz, 3H), 2.19 (dd, J ) 3.6, 4.4 Hz, 1H), 2.65 (apparent
d, J ) 8.4 Hz, 1H), 2.87 (dd, J ) 1.6, 2.8 Hz, 1H), 3.19 (dd, J
) 4.4, 6.4 Hz, 1H), 3.46 (s, 3H), 3.78 (d, J ) 8.0 Hz, 1H), 4.07
(dd, J ) 3.6, 8.0 Hz, 1H), 5.18 (ddq, J ) 1.2, 8.4, 15.0 Hz, 1H),
5.49 (dq, J ) 6.4, 15.0 Hz, 1H), 5.80 (ddq, J ) 1.6, 1.6, 6.4 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 17.9, 21.6, 42.0, 43.6, 45.4,
51.1, 57.7, 73.7, 100.2, 121.2, 126.5, 130.8, 137.5, 200.8; MS
(70 eV) m/z (relative intensity) 206 (M+ - CO, 100), 191 (4),
J. Org. Chem, Vol. 70, No. 23, 2005 9165

Hsu et al.
147 (52), 131 (36), 119 (66), 105 (64), 91 (70), 77 (31), 59 (27),
39 (34); HRMS (EI) calcd for C13H18O2 (M+ - CO) 206.1298,
found 206.1310.
(2aR*,5S*,5aR*,8aR*,8bS*)-8a-Methoxy-5,7-dimethyl-
2a,5,5a,8,8a,8b-hexa-hydro-2H-benzo[cd]isobenzofuran-
8-one (30b): colorless liquid; IR (film) 2959, 1677, 1460, 1058
1
cm-1; H NMR (400 MHz, CDCl3) δ 1.04 (d, J ) 7.6 Hz, 3H),
Methyl (1S*,3R*,6S*,7S*,10S*)-3-methoxy-2-oxo-10-vinyl-
4-oxatricyclo[4.3.1.03,7]dec-8-ene-9-carboxylate (28a): col-
orless liquid; IR (film) 3078, 2920, 1746, 1716, 1683, 1436, 1018
cm-1; 1H NMR (400 MHz, CDCl3) δ 2.35-2.45 (m, 1H), 2.80-
2.90 (m, 1H), 3.49 (dd, J ) 4.4, 6.8 Hz, 1H) 3.51 (s, 3H), 3.75
(s, 3H), 3.78 (dd, J ) 1.9, 2.4 Hz, 1H), 3.88 (d, J ) 8.4 Hz,
1H), 4.19 (dd, J ) 3.6, 8.4 Hz, 1H), 5.03 (d, J ) 10.4 Hz, 1H),
5.05 (d, J ) 17.2 Hz, 1H), 5.52 (ddd, J ) 7.2, 10.4, 17.2 Hz,
1H), 7.22 (dd, J ) 1.9, 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 43.6, 43.8, 50.7, 51.4, 52.1, 73.6, 99.4, 115.8, 131.9, 138.2,
138.4, 163.4, 199.5; MS (70 eV) m/z (relative intensity) 236
(M+ - CO, 30), 221 (2), 177 (22), 169 (24), 145 (59), 117 (100),
91 (63), 77 (34), 59 (50), 41 (66); HRMS (EI) calcd for C13H16O4
(M+ - CO) 236.1049, found 236.1033.
1.83 (d, J ) 2.0 Hz, 3H), 2.20-2.40 (m, 1H), 2.80-2.84 (m,
1H), 2.90-3.00 (m, 2H), 3.32 (s, 3H), 3.62 (dd, J ) 4.4, 8.8 Hz,
1H), 4.16 (dd, J ) 7.2, 8.8 Hz, 1H), 5.64 (m, 2H), 6.47 (dd, J )
2.0, 4.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 16.0, 17.5, 32.7,
35.8, 37.3, 46.9, 51.2, 72.5, 103.6, 128.9, 133.6, 136.6, 144.1,
192.7; MS (70 eV) m/z (relative intensity) 234 (M+, 23), 203
(21), 189 (9), 176 (74), 129 (36), 101 (100), 99 (43), 91 (62), 81
(37), 77 (33); HRMS (EI) calcd for C14H18O3 (M+) 234.1256,
found 234.1260.
(2a*R,5aS*,8aR*,8bS*)-8a-Methoxy-6-methyl-2a,5,5a,
8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-8-one
(32a): colorless liquid; IR (film) 3039, 2942, 1681, 1634, 1437,
1
1026 cm-1; H NMR (400 MHz, CDCl3) δ 1.55-1.70 (m, 1H),
Methyl (1S*,3R*,6S*,7S*,10S*)-3-methoxy-2-oxo-10-[(E)-
1-propenyl]-4-oxatricyclo[4.3.1.03,7]dec-8-ene-9-carboxy-
late (28b): colorless liquid; IR (film) 2952, 1746, 1719, 1665,
2.00 (d, J ) 1.2 Hz, 3H), 2.20-2.40 (m, 2H), 2.82 (ddd, J )
2.0, 7.2, 8.8 Hz, 1H), 3.05-3.15 (m, 1H), 3.26 (s, 3H), 3.77 (dd,
J ) 2.4, 8.2 Hz, 1H), 4.09 (dd, J ) 7.6, 8.2 Hz, 1H), 5.79 (ddd,
J ) 2.8, 5.2, 10.4 Hz, 1H), 5.86 (ddd, J ) 2.8, 5.2, 10.4 Hz,
1H), 5.89 (dq, J ) 1.2, 2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 23.3, 29.9, 36.9, 38.2, 46.7, 50.0, 74.6, 102.9, 124.8, 126.8,
129.6, 165.4, 190.3; MS (70 eV) m/z (relative intensity) 220
(M+, 14), 204 (6), 189 (55), 161 (47), 147 (60), 131 (52), 117
(51), 105 (43), 91 (100), 77 (53); HRMS (EI) calcd for C13H16O3
(M+) 220.1099, found 220.1093.
1
1628, 1438, 1022 cm-1; H NMR (400 MHz, CDCl3) δ 1.57 (d,
J ) 6.0 Hz, 3H), 2.20-2.40 (m, 1H), 2.74 (apparent d, J ) 8.0
Hz, 1H), 3.46 (s, 3H), 3.72 (s, 3H), 3.83 (d, J ) 8.0 Hz, 3H),
4.14 (dd, J ) 3.6, 8.0 Hz, 1H), 5.08 (ddd, J ) 1.6, 8.0, 15.4 Hz,
1H), 5.47 (dq, J ) 6.0, 15.4 Hz, 1H), 7.20 (dd, J ) 2.2, 6.8 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 17.8, 43.6, 43.7, 45.0, 51.1,
52.1, 73.6, 99.4, 127.4, 129.7, 131.7, 138.6, 163.6, 200.1; MS
(70 eV) m/z (relative intensity) 250 (M+ - CO, 97), 247 (44),
198 (22), 191 (22), 159 (48), 131 (73), 115 (30), 91 (46), 59 (30),
43 (100); HRMS (EI) calcd for C15H18O5 (M+) 278.1154, found
278.1173.
(2aR*,5S*,5aS*,8aR*,8bS*)-8a-Methoxy-5,6-dimethyl-
2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (32b): IR (film) 3021, 2967, 1678, 1630, 1435, 1026 cm-1
;
1H NMR (400 MHz, CDCl3) δ 0.71 (s, 3H), 1.96 (s, 3H), 2.30-
2.41 (m, 1H), 2.62 (dd, J ) 6.0, 8.0 Hz, 1H), 2.82 (dd, J ) 8.0,
10.0 Hz, 1H), 3.10-3.16 (m, 1H), 3.29 (s, 3H), 3.74 (dd, J )
2.8, 8.0 Hz, 1H), 4.08 (dd, J ) 8.0, 8.8 Hz, 1H), 5.73 (dd, J )
6.0, 10.0 Hz, 1H), 5.97 (dd, J ) 6.0, 10.0 Hz. 1H), 6.06 (s, 1H);
13C NMR (100 MHz, CDCl3) δ 17.4, 23.2, 30.2, 35.7, 41.1, 46.2,
50.2, 74.3, 103.0, 127.1, 127.3, 132.5, 162.4, 189.9; MS (70 eV)
m/z (relative intensity) 234 (M+, 8), 206 (19), 203 (87), 175 (29),
161 (38), 143 (54), 133 (39), 105 (55), 91 (100), 77 (54); HRMS
(EI) calcd for C14H18O3 (M+) 234.1256, found 234.1256.
(2aR*,5aR*,8aR*,8bS*)-8a-Methoxy-2a,5,5a,8,8a,8b-
hexahydro-2H-benzo[cd]isobenzofuran-8-one (29a): color-
less liquid; IR (film) 2963, 1686, 1605, 1455, 1019 cm-1 1H
;
NMR (400 MHz, CDCl3) δ 1.70-1.80 (m, 1H), 2.23 (ddd, J )
5.2, 5.2, 16.4 Hz, 1H), 2.61-2.69 (m, 1H), 2.87 (dd, J ) 8.0,
8.8 Hz, 1H), 3.10-3.14 (m, 1H), 3.34 (s, 3H), 3.73 (dd, J ) 3.6,
8.4 Hz, 1H), 4.14 (dd, J ) 8.0, 8.4 Hz, 1H), 5.83 (ddd, J ) 1.8,
5.2, 10.0 Hz, 1H), 5.89 (ddd, J ) 3.2, 5.6, 10.0 Hz, 1H), 6.08
(dd, J ) 1.6, 10.0 Hz, 1H), 6.93 (dd, J ) 5.2, 10.0 Hz, 1H); 13
C
NMR (100 MHz, CDCl3) δ 30.0, 32.8, 37.2, 46.7, 50.6, 74.4,
103.3, 127.3, 128.2, 129.9, 152.9, 191.5; MS (70 eV) m/z
(relative intensity) 206 (M+, 37), 178 (8), 175 (8), 148 (53), 117
(67), 105 (54), 91 (100), 77 (68), 51 (38); HRMS (EI) calcd for
C12H14O3 (M+) 206.0943, found 206.0940.
Methyl (2aR*,5aS*,8aR*,8bR*)-8a-methoxy-8-oxo-2a,
5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-6-car-
boxylate (33a): colorless liquid; IR (film) 2949, 1724, 1696,
1
1434, 1249, 1038 cm-1; H NMR (400 MHz, CDCl3) δ 1.52-
1.58 (m, 1H), 2.31 (ddd, J ) 5.2, 6.4, 16.0 Hz, 1H), 2.87 (dd, J
) 7.0, 8.8 Hz, 1H), 3.03 (ddd, J ) 5.2, 7.0, 11.6 Hz, 1H), 3.10-
3.20 (m, 1H), 3.22 (s, 3H), 3.83 (s, 3H), 3.86 (dd, J ) 1.6, 8.0
Hz, 1H), 4.12 (dd, J ) 7.2, 8.0 Hz, 1H), 5.80 (ddd, J ) 2.4, 4.4,
9.8 Hz, 1H), 5.86 (ddd, J ) 2.4, 6.4, 9.8 Hz, 1H), 6.85 (s, 1H);
13C NMR (100 MHz, CDCl3) δ 31.0, 31.8, 37.0, 47.0, 49.8, 52.8,
74.7, 103.6, 126.9, 129.0, 132.5, 151.6, 165.9, 191.2; MS (70
eV) m/z (relative intensity) 264 (M+ , 23), 249 (60), 233 (34),
205 (34), 176 (22), 145 (48), 117 (100), 115 (21), 99 (67), 91
(61); HRMS (EI) calcd for C13H16O4 (M+) 264.0094, found
264.0997.
(2aR*,5S*,5aS*,8aR*,8bS*)-8a-Methoxy-5-methyl-
2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-
8-one (29b): colorless liquid; IR (film) 3021, 2969, 1685, 1458,
1
1035 cm-1; H NMR (400 MHz, CDCl3) δ 1.15 (d, J ) 7.2 Hz,
3H), 2.35-2.42 (m, 1H), 2.80-3.10 (m, 3H), 3.35 (s, 3H), 3.67
(dd, J ) 4.8, 8.6 Hz, 1H), 4.18 (dd, J ) 8.0, 8.6 Hz, 1H), 5.67
(s, 2H), 6.15 (dd, J ) 1.6, 10.2 Hz, 1H), 6.76 (dd, J ) 6.6, 10.2
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 17.4, 32.7, 37.2, 37.3,
51.4, 72.2, 103.1, 129.4, 129.7, 133.7, 149.7, 192.1; MS (70 eV)
m/z 220 (M+, 100), 196 (33), 192 (49), 177 (7), 162 (22), 147
(21), 133 (8), 117 (5), 91 (7), 77 (6); HRMS (EI) calcd for
C13H16O3 (M+) 220.1100, found 220.1095.
Methyl (2aR*,5S*,5aS*,8aR*,8bS*)-8a-methoxy-5-meth-
yl-8-oxo-2a,5,5a,8,8a,8b-hexahydro-2H-benzo[cd]isoben-
zofuran-6-carboxylate (33b): colorless liquid; IR (film) 3021,
2953, 1721, 1695, 1621, 1436, 1019 cm-1; 1H NMR (400 MHz,
CDCl3) δ 0.68 (d, J ) 6.8 Hz, 1H), 2.41 (ddd, J ) 6.4, 6.8, 11.8
Hz, 1H), 2.84 (dd, J ) 8.0, 11.8 Hz, 1H), 3.10-3.20 (m, 1H),
3.23 (s, 3H), 3.29 (dd, J ) 4.8, 8.0 Hz, 1H), 3.80 (dd, J ) 3.6,
8.8 Hz, 1H), 3.84 (s, 3H), 4.10 (dd, J ) 8.0, 8.8 Hz, 1H), 5.70
(dd, J ) 5.2, 10.0 Hz, 1H), 5.95 (dd, J ) 6.4, 10.0 Hz, 1H),
6.98 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 17.7, 30.7, 35.0,
35.8, 46.3, 50.0, 52.8, 74.2, 103.6, 126.7, 132.7, 134.1, 148.9,
166.0, 190.9; MS (70 eV) m/z (relative intensity) 278 (M+, 8),
263 (21), 250 (19), 247 (86), 219 (18), 187 (13), 159 (31), 131
(2aR*,5aR*,8aR*,8bS*)-8a-Methoxy-7-methyl-2a,5,5a,
8,8a,8b-hexahydro-2H-benzo[cd]isobenzofuran-8-one
(30a): colorless liquid; IR (film) 2942, 1682, 1450, 1029 cm-1
;
1H NMR (400 MHz, CDCl3) δ 1.60-1.80 (m, 1H), 1.71 (s, 3H),
2.18 (ddd, J ) 1.2, 5.6, 16.0 Hz, 1H), 2.50-2.54 (m, 1H), 2.84
(dd, J ) 8.4, 8.8 Hz, 1H), 3.05-3.10 (m, 1H), 3.31 (s, 3H), 3.73
(dd, J ) 3.6, 8.2 Hz, 1H), 4.13 (dd, J ) 8.0, 8.2 Hz, 1H), 5.80
(ddd, J ) 2.0, 6.4, 9.4 Hz, 1H), 5.87 (ddd, J ) 2.8, 5.6, 9.4 Hz,
1H), 6.66 (dd, J ) 1.6, 6.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 15.7, 30.4, 31.9, 37.3, 46.5, 50.4, 74.6, 103.6, 127.4, 129.6,
135.2, 147.3, 192.1; MS (70 eV) m/z (relative intensity) 220
(M+, 6), 192 (75), 189 (27), 162 (49), 147 (36), 125 (62), 117
(54), 105 (59), 91 (100), 77 (46); HRMS (EI) calcd for C13H16O3
(M+) 220.1100, found 220.1105.
(59), 115 (51), 99 (100); HRMS (EI) calcd for C15H18O5 (M+
278.1154, found 278.1157.
)
9166 J. Org. Chem., Vol. 70, No. 23, 2005

Dual Behavior of MOBs in IMDA Reactions
(1R*,3R*,6R*,7R*,10R*)-3-Methoxy-1-methyl-10-[(E)-1-
propenyl]-4-oxatricyclo[4.3.1.03,7]decane-2,8-dione (35):
colorless liquid; IR (film) 2970, 1740, 1450, 1023 cm-1; 1H NMR
(400 MHz, CDCl3) δ 1.07 (s, 3H), 1.71 (dd, J ) 1.6, 6.4 Hz,
3H), 2.14 (dd, 1.6, 19.6 Hz, 1H), 2.30 (apparent d, J ) 8.8 Hz,
1H), 2.52 (d, J ) 19.6 Hz, 1H), 2.67 (dd, J ) 3.6, 4.4 Hz, 1H),
3.27 (apparent d, J ) 4.4 Hz, 1H), 3.48 (s, 3H), 3.83 (d, J )
8.0 Hz, 1H), 4.16 (dd, J ) 3.6, 8.0 Hz, 1H), 5.34 (ddq, J ) 1.6,
8.8, 15.2 Hz, 1H), 5.56 (dq, J ) 6.4, 15.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 16.6, 18.1, 43.1, 44.8, 46.3, 47.5, 51.5, 55.6,
74.5, 104.1, 126.9, 130.6, 205.4, 206.5; MS (70 eV) m/z (relative
intensity) 222 (M+ - CO, 69), 194 (18), 167 (24), 153 (14), 147
(9), 121 (14), 99 (100), 79 (72), 71 (68), 41 (75) HRMS (EI) calcd
for C13H18O3 222.1256, found 222.1253.
Hz, 1H), 4.21 (dd, J ) 3.2, 8.4 Hz, 1H), 5.37 (ddd, J ) 1.6, 8.0,
15.2 Hz, 1H), 5.51 (dd, J ) 6.8, 14.8 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 18.1, 39.1, 43.6, 44.0, 52.1, 52.7, 56.9, 59.2,
74.4, 104.0, 126.0, 131.1, 168.4, 199.2, 201.4; MS (70 eV) m/z
(relative intensity) 292 (M+, 6), 248 (34), 233 (22), 215 (100),
201 (52), 187 (64), 173 (33), 157 (78), 129 (10), 115 (67); HRMS
(EI) calcd for C15H18O5 (M+) 292.0946, found 292.0951.
Acknowledgment. We gratefully acknowledge the
financial support from the National Science Council
(NSC) of the Republic of China. R.K.P. thanks the NSC
for a postdoctoral fellowship. We thank Dr. N. S. K. Rao
for helpful discussions.
Methyl (1S*,3R*,6R*,7S*,10R*)-3-methoxy-2,8-dioxo-10-
[(E)-1-propenyl]-4-oxatricyclo[4.3.1.03,7]decane-1-carbox-
ylate (37): colorless liquid; IR (film) 2954, 1757, 1731, 1438,
Supporting Information Available: General remarks,
1
general experimental procedures, and H NMR spectra of all
1
1044 cm-1; H NMR (400 MHz, CDCl3) δ 1.67 (d, J ) 5.6 Hz,
the new compounds. This material is available free of charge
via the Internet at http://pubs.acs.org.
3H), 2.65-2.75 (m, 1H), 2.71 (dd, J ) 1.6, 20.4 Hz, 1H), 2.91
(d, J ) 20.4 Hz, 1H), 3.23 (apparent d, J ) 8.0 Hz, 1H), 3.27
(d, J ) 4.4 Hz, 1H), 3.52 (s, 3H), 3.79 (s, 3H), 3.94 (d, J ) 8.0
JO0510179
J. Org. Chem, Vol. 70, No. 23, 2005 9167