Palladium-Catalyzed Carbon Dioxide Elimination-Fixation Reaction of 4-Methoxycarbonyloxy-2-buten-1-ols

Article abstract of DOI:10.1021/jo0353280

A new type of palladium-catalyzed CO₂ recycling reaction using allylic carbonates is described. Reaction of trans-4-methoxycarbonyloxy-2-buten-1-ols in the presence of a palladium catalyst produces cyclic carbonates having a vinyl group via a CO₂ elimination-fixation process. A variety of allylic carbonates participate in the reaction giving cyclic carbonates with high efficiencies. Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates. An enantiospecific reaction proceeds to give chiral cyclic carbonate when a chiral methyl-substituted substrate is subjected to the reaction conditions.

Full text of DOI:10.1021/jo0353280

P a lla d iu m -Ca ta lyzed Ca r bon Dioxid e Elim in a tion -F ixa tion
Rea ction of 4-Meth oxyca r bon yloxy-2-bu ten -1-ols
Masahiro Yoshida,* Yusuke Ohsawa, and Masataka Ihara*
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences,
Tohoku University, Aobayama, Sendai 980-8578, J apan
mihara@mail.pharm.tohoku.ac.jp
Received September 9, 2003
A new type of palladium-catalyzed CO2 recycling reaction using allylic carbonates is described.
Reaction of trans-4-methoxycarbonyloxy-2-buten-1-ols in the presence of a palladium catalyst
produces cyclic carbonates having a vinyl group via a CO2 elimination-fixation process. A variety
of allylic carbonates participate in the reaction giving cyclic carbonates with high efficiencies.
Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates.
An enantiospecific reaction proceeds to give chiral cyclic carbonate when a chiral methyl-substituted
substrate is subjected to the reaction conditions.
In tr od u ction
organic compounds.3,4 Recently, we have developed a
novel palladium-catalyzed reaction of propargylic carbon-
ates with phenols, which involves a “recycling of CO2”
process.5 The reaction proceeds via a carbon dioxide
elimination-fixation step and affords phenoxy-substi-
Palladium-catalyzed allylic substitutions of allylic com-
pounds with soft nucleophiles are an extensively studied
research area in organic chemistry, and many examples
and their applications have been developed.1 Among
them, reactions of allylic carbonates are one of the most
common methods in which various kinds of nucleophiles
are substituted at the allylic position via a π-allylpalla-
dium intermediate (eq 1).1e-k The reactions can be
(2) Arakawa, H.; Aresta, M.; Armor, J . N.; Barteau, M. A.; Beckman,
E. J .; Bell, A. T.; Bercaw, J . E.; Creutz, C.; Dinjus, E.; Dixon, D. A.;
Domen, K.; DuBois, D. L.; Eckert, J .; Fujita, E.; Gibson, D. H.; Goddard,
W. A.; Goodman, D. W.; Keller, J .; Kubas, G. J .; Kung, H. H.; Lyons,
J . E.; Manzer, L. E.; Marks, T. J .; Morokuma, K.; Nicholas, K. M.;
Periana, R.; Que, L.; Rostrup-Nielson, J .; Sachtler, W. M. H.; Schmidt,
L. D.; Sen, A.; Somorjai, G. A.; Stair, P. C.; Stults, B. R. Chem. Rev.
2001, 101, 953.
(3) For reviews about CO2 fixation by transition metal complexes:
(a) Vol’pin, M. E.; Kolominkov, I. S. Pure Appl. Chem. 1973, 33, 567.
(b) Eisenberg, R.; Hendriksen, D. E. Adv. Catal. 1979, 28, 79. (c) Ibers,
J . A. Chem. Soc. Rev. 1982, 11, 57. (d) Haruki, E.; Ito, T.; Yamamoto,
A.; Yamazaki, N.; Higashi, F.; Inoue, S. In Organic and Bioorganic
Chemistry of Carbon Dioxide; Inoue, S., Yamazaki, N., Eds.; Kodan-
sha: Tokyo, 1982; p 199. (e) Behr, A. In Catalysis in C1 Chemistry;
Keim, W., Ed.; D. Reidel Publishing Co.: Dordrecht, Holland, 1983; p
169. (f) Walther, D. Coord. Chem. Rev. 1987, 79, 135. (g) Braunstein,
P.; Matt, D.; Nobel, D. Chem. Rev. 1988, 88, 747. (h) Cutler, A. R.;
Hanna, P. K.; Vites, J . C. Chem. Rev. 1988, 88, 1363. (i) Behr, A.
Angew. Chem., Int. Ed. Engl. 1988, 27, 661. (j) Behr, A. Carbon Dioxide
Activation by Metal Complexes; VCH: Weinheim, Germany, 1988; p
91. (k) Miller, J . D. In Reactions of Coordinated Ligands; Braterman,
P. S., Ed.; Plenum Press: New York, 1989; Vol. 2, p 1. (l) Halmann,
M. M. Chemical Fixation of Carbon Dioxide. Methods for Recycling CO2
into Useful Products; CRC Press: Boca Raton, FL, 1993. (m) Creutz,
C. In Electrochemical and Electrocatalytic Reactions of Carbon Dioxide;
Sullivan, B. P., Krist, K., Guard, H. E., Eds.; Elsevier: Amsterdam,
The Netherlands, 1993; Chapter 2. (n) Aresta, M.; Quaranta, E.;
Tommasi, I. New J . Chem. 1994, 18, 133. (o) Leitner, W. Coord. Chem.
Rev. 1996, 153, 127. (p) Gibson, D. H. Chem. Rev. 1996, 96, 2063. (q)
Yin, X.; Moss, J . R. Coord. Chem. Rev. 1999, 181, 27. (r) Walther, D.;
Ruben, M.; Rau, S. Coord. Chem. Rev. 1999, 182, 67.
(4) For examples of palladium-catalyzed CO2 fixation reactions to
give cyclic carbonates: (a) Fujinami, T.; Suzuki, T.; Kamiya, M.;
Fukuzawa, S.; Sakai, S. Chem. Lett. 1985, 199. (b) Trost, B. M.; Angle,
S. R. J . Am. Chem. Soc. 1985, 107, 6123. (c) Trost, B. M.; Lynch, J . K.;
Angle, S. R. Tetrahedron Lett. 1987, 28, 375. (d) Wershofen, S.; Scharf,
H. D. Synthesis 1988, 854. (e) Suzuki, S.; Fujita, Y.; Kobayashi, Y.;
Sato, F. Tetrahedron Lett. 1989, 30, 3487. (f) Uemura, K.; Shiraishi,
D.; Noziri, M.; Inoue, Y. Bull. Chem. Soc. J pn. 1999, 72, 1063.
(5) (a) Yoshida, M.; Ihara, M. Angew. Chem., Int. Ed. 2001, 40, 616.
(b) Yoshida, M.; Fujita, M.; Ishii, T.; Ihara, M. J . Am. Chem. Soc. 2003,
125, 4874.
conveniently carried out in neutral conditions because
the alkoxide ion formed in situ abstracts the active
hydrogen from a protonated nucleophile to generate a
reactive anionic nucleophile. In these reactions, CO2 is
invariably produced as a coproduct.
Fixation of carbon dioxide into organic substances
represents an attractive area of study in both organic and
green chemistry.2 Palladium-catalyzed reactions are one
of the common methods to fix external carbon dioxide into
(1) For reviews about palladium-catalyzed reactions of allylic com-
pounds: (a) Tsuji, J . Acc. Chem. Res. 1969, 2, 144. (b) Tsuji, J . Pure
Appl. Chem. 1982, 54, 197. (c) Trost, B. M.; Verhoeven, T. R. In
Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G.
A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 8, p 799. (d) Heck,
R. F. Palladium Reagents in Organic Synthesis; Academic Press: New
York, 1985. (e) Tsuji, J . J . Organomet. Chem. 1986, 300, 281. (f) Tsuji,
J . Tetrahedron 1986, 42, 4261. (g) Tsuji, J .; Minami, I. Acc. Chem. Res.
1987, 20, 140. (h) Tsuji, J . Organic Synthesis with Palladium Com-
pounds; Springer-Verlag: New York, 1990. (i) Godleski, S. In Com-
prehensive Organic Synthesis; Trost, B. M., Fleming, I., Semmelhack,
M. F., Eds.; Pergamon: Oxford, U.K., 1991; Vol. 4, p 585. (j) Tsuji, J .
Palladium Reagents and Catalysts; J ohn Wiley and Sons: Chichester,
U.K., 1995. (k) Trost, B. M.; Van Vranken, D. L. Chem. Rev. 1996, 96,
395.
10.1021/jo0353280 CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/06/2004
1590
J . Org. Chem. 2004, 69, 1590-1597

Pd-Catalyzed CO2 Elimination-Fixation Reaction
SCHEME 1. Syn th esis of Allylic Ca r bon a tes
TABLE 1. F or m a tion of Cyclic Ca r bon a te 5a by th e
Rea ction of P r op a r gylic Ca r bon a te 3a
tuted cyclic carbonates (eq 2). We sought to determine
entry
catalyst
time (h)
yielda (%)
1
2
3
4
dppe
dppp
dppb
dppf
8
8
8
58
NR
NR
79
whether a “recycling of CO2” process could apply for
allylic carbonates to yield cyclic carbonates (eq 3). Herein,
1
5b
6b
7c
8d
9e
P(o-Tol)3
PPh3
dppf
dppf
dppf
8
2
4
96
96
NR
63
79
57
25 (50)
a
The yield in parentheses is based on recovered starting
b
material. NR stands for no reaction. 40 mol % ligand was used.
we describe the details of this process.
c 2.5 mol % Pd2(dba)3‚CHCl3 and 10 mol % ligand were used.
1
d
mol % Pd2(dba)3‚CHCl3 and 4 mol % ligand were used. e 0.5 mol
% Pd2(dba)3‚CHCl3 and 2 mol % ligand were used.
Resu lts a n d Discu ssion
Allylic carbonates for palladium-catalyzed reactions are
synthesized as follows (Scheme 1). The propargylic diols
having various substituents 1a -1g are selectively re-
duced to trans-allylic diols 2a -2g in 61-89% yields by
reactions with LAH in the presence of sodium methoxide.
Reactions of 2a -2g with methyl chloroformate in the
presence of pyridine afford allylic carbonates 3a -3g in
63-98% yields. Similarly, unsymmetric substrates 3h
and 3i are prepared from the corresponding propargylic
diols 1h and 1i in two steps. A substrate 3j having a
secondary alcohol moiety is also synthesized from the
corresponding allylic diol 2j. To perform mechanistic
studies on the palladium-catalyzed reaction, allylic ben-
zoate 4c is prepared from 2c and benzoyl chloride.
Our initial attempt at palladium-catalyzed reaction of
allylic carbonate begins with 3a (Table 1). When 3a is
subjected to 5 mol % Pd2(dba)3‚CHCl3 and 20 mol % 1,2-
bis(diphenylphosphino)ethane (dppe) in dioxane at 50
°C under an argon atmosphere in a sealed tube, cyclic
carbonate 5a , having a vinyl group, is produced in 58%
yield (entry 1). Although no reaction proceeds in the
presence of 1,3-bis(diphenylphosphino)propane (dppp),
1,4-bis(diphenylphosphino)butane (dppb), and P(o-Tol)3
(entries 2, 3, and 5), the yield is increased to 79% when
1,1′-bis(diphenylphosphino)ferrocene (dppf) is used as a
ligand (entry 4). The reaction in the presence of PPh3 also
gives 5a in 63% yield (entry 6). Although the reason for
the observed specificity depending on the ligand is not
clear, it is proposed that this CO2 elimination-fixation
process is sensitive for the steric and electronic properties
of the phosphine ligand, and dppf is suitable for the
J . Org. Chem, Vol. 69, No. 5, 2004 1591

Yoshida et al.
SCHEME 2. P r op osed Rea ction Mech a n ism
TABLE 2. Rea ction s of Va r iou s Su bstitu ted Allylic
Ca r bon a tes 3b-3ga
initially examined the reactions of allylic benzoate 4c,
having a non-CO2 liberating leaving group, in the pres-
ence of CO2. When 4c is subjected to the palladium
catalyst in the presence of N,O-bis(trimethylsilyl)acet-
amide (BSA)6 under an atmosphere of CO2, the corre-
sponding cyclic carbonate 5c is produced in 74% yield
(eq 4). This result indicates that the product is formed
a
Reactions were carried out in the presence of 5 mol %
Pd2(dba)3‚CHCl3 and 20 mol % dppf in dioxane under an argon
b
atmosphere at 50 °C in a sealed tube for 1-24 h. Dppe was used
as a ligand.
reaction. The reaction exhibits similar reactivity in the
presence of 2.5 mol % palladium catalyst (entry 7), but
the reactivity has been decreased in the presence of 1
mol % and 0.5 mol % palladium catalyst (entries 8 and
9).
The results of the reactions of allylic carbonates
3b-3g, which contain various substituents, are sum-
marized in Table 2. The corresponding cyclic carbonate
5b is formed in 76% yield when dipropyl-substituted
substrate 3b is used (entry 1). Substrates 3c and 3d ,
having dipentyl and di-â-cyclohexylethyl groups, are
transformed to 5c and 5d in 79% and 68% yield,
respectively (entries 2 and 3). Reactions of substrates 3e,
3f, and 3g with cycloalkanol moieties of various ring sizes
also afford the corresponding products 5e, 5f, and 5g in
moderate yields (entries 4, 5, and 6).
by a route in which CO2 is incorporated from an external
source.
A crossover experiment with allylic carbonate 3f and
allylic benzoate 4c is next performed (eq 5). Reaction of
Mech a n istic Stu d ies. A proposed mechanism for the
formation of cyclic carbonates by the palladium-catalyzed
reaction of the allylic carbonates is shown in Scheme 2.
A palladium catalyst initially promotes decarboxylation
of allylic carbonate to generate a π-allylpalladium com-
plex 6, MeOH, and CO2. Fixation of CO2 by the resulting
hydroxyl anion leads to an intermediate 7, and subse-
quent cyclization gives a cyclic carbonate 5. However, as
another mechanism, an intramolecular CO2 transfer
pathway via 8, which involves a chelation of carbonate
to palladium without decarboxylation, is also expected.
To examine whether CO2 dissociates from the substrate
in the reaction, several experiments were attempted. We
an equimolar mixture of 3f and 4c under palladium
catalysis results in production of cyclic carbonate 5c in
22% yield, which is derived from 4c, along with the
formation of 3f-derived cyclic carbonate 5f and 4c-derived
epoxide 9c in 20% and 19% yield, respectively. It is clear
(6) For a review on BSA: El Gihani, M. T.; Heaney, H. Synthesis
1998, 357.
1592 J . Org. Chem., Vol. 69, No. 5, 2004

Pd-Catalyzed CO2 Elimination-Fixation Reaction
SCHEME 3. Dia ster eoselective Con str u ction of
Cyclic Ca r bon a tes
F IGURE 1. NOESY correlations of trans- and cis-5h and 5i.
SCHEME 4. Syn th esis of Ch ir a l Allylic Ca r bon a te
(S)-14
that 5c arises by reaction of in situ generated CO2 formed
by decarboxylation of 3f.
We also conducted the reactions in both the presence
and the absence of a CO2 source (eq 6). While the reaction
of allylic carbonate 3c with Pd2(dba)3‚CHCl3 and dppf
under an argon atmosphere yields cyclic carbonate 5c
in 79% yield (entry 4 in Table 1), the process carried
out under 1 atm of CO2 leads to an 86% yield of 5c.
stereochemical outcome of the process is based on a
consideration of the transition state for cyclization of the
interconverting, isomeric π-allylpalladium intermediates
A and B (eq 7). Equilibration between A and B occurs
Furthermore, when the reaction is carried out under
bubbling argon to remove the resulting CO2, 5c is formed
in only 17% yield together with epoxide 9c in 20% yield.
It is expected that 9c would be obtained by direct
cyclization from intermediate 6 without fixation of CO2,
and these results support the hypothesis that the process
proceeds through a pathway involving decarboxylation-
fixation of liberated CO2.
Ster eoselective Con str u ction of Cyclic Ca r bon -
a te. We also studied the reaction using unsymmetric
allylic carbonates (Scheme 3). Substrate 3h , derived from
acetophenone, reacts with the palladium catalyst to
afford a mixture of products trans- and cis-5h with trans-
selectivity (50% yield of trans-5h , 19% yield of cis-5h ).
Furthermore, trans-cyclic carbonate 5i is produced as a
sole product in 72% yield when substrate 3i, having a
2-phenylcyclohexyl group, is subjected to the reaction. On
the other hand, a reaction of allylic carbonates 3j with
a secondary alcohol moiety gives a complex mixture,
which reveals that a tertiary alcohol moiety in the sub-
strate is necessary for the reaction.7 The stereochemis-
tries of the obtained products were all determined by
NOESY spectra (Figure 1). A proposed rationale for the
by π-σ-π isomerization. It is expected that the transition
state for cyclization B, forming the trans-product, would
be of lower energy because of the absence of the steric
repulsion that is present in the transition state derived
from A.
En a n tiosp ecific Con str u ction of Cyclic Ca r bon -
a te. It is known that enantiospecific chirality transfer
is observed in the palladium-catalyzed reaction of chiral
allylic compounds.8 We sought to apply this property of
π-allylpalladium species to our CO2 recycling process by
introducing an asymmetric center at an allylic position.9
Scheme 4 shows the synthesis of chiral methyl-substi-
tuted substrate (S)-14. Chiral propargylic alcohol (S)-10,
with 95% ee, is protected with the TBDPS group and then
treated with BuLi followed by dipentyl ketone to give
propargylic alcohol (S)-11 in 95% yield. After the depro-
tection of the silyl group that leads to diol (S)-12,
(8) For reviews on stereochemical studies of palladium-catalyzed
reactions of allylic compounds: (a) Tsuji, J . Tetrahedron 1986, 42, 4361.
(b) Consiglio, G.; Waymouth, R. M. Chem. Rev. 1989, 89, 257. (c) Trost,
B. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1173. (d) Heumann, A.;
Re´glier, M. Tetrahedron 1995, 51, 975. (e) Trost, B. M.; Vranken, D.
L. V. Chem. Rev. 1996, 96, 395.
(7) Previously, we obtained
catalyzed reaction of propargylic carbonate containing a primary
alcohol; see ref 5b.
a
similar result in the palladium-
(9) Recently, we discovered the reaction of substituted chiral pro-
pargylic carbonates with phenols proceeds with transferring chiral-
ity: Yoshida, M.; Fujita, M.; Ihara, M. Org. Lett. 2003, 5, 3325.
J . Org. Chem, Vol. 69, No. 5, 2004 1593

Yoshida et al.
TABLE 3. F or m a tion of Cyclic Ca r bon a te 16 by th e
Rea ction of P r op a r gylic Ca r bon a te 14
yielda,b (%)
entry
ligand
atmosphere
time (h)
16
17
1
2
3
4
dppf
dppf
dppe
dppp
dppb
PPh3
argon
CO2
argon
argon
argon
argon
24
48
12
6
4
4
13 (15)
19 (66)
85
15
64
45 (53)
4 (12)
7
64
6
F IGURE 2. Determination of the absolute configuration of
16.
the product is determined by Kusumi’s method10 after
conversion to the MTPA esters. Product (S)-16 is sub-
jected to hydrolysis in the presence of 1 N NaOH to give
diol 18, and then the product is transformed to (S)- and
(R)-MTPA ester (S)- and (R)-19 by reaction with (R)- and
(S)-MTPA chloride (eq 9). On the basis of the ∆δ values
5
6c
32
67
a
b
Isolated yields. The yields in parentheses are based on
recovered starting material. c 40 mol % ligand was used.
reduction of the alkyne followed by methyl carbonation
of the secondary alcohol affords chiral allylic carbonate
(S)-14. By following the same procedure, racemic allylic
carbonate 14 is also synthesized from racemic 10. The
enantiomeric excess of (S)-14 is determined as 95% ee
by conversion of diol (S)-13 with 2-methoxy-2-trifluoro-
methyl-2-phenylacetyl chloride (MTPACl) to MTPA ester
(S,S)-15.
We initially attempted the reaction using racemic
allylic carbonate 14 (Table 3). Reaction of the sub-
strate in the presence of 5 mol % Pd2(dba)3‚CHCl3 and
20 mol % dppe in dioxane at 50 °C under an argon
atmosphere for 24 h produces racemic cyclic carbonate
16, which has E geometry, in 13% yield together with
diene 17 in 45% yield and a small amount of recovered
starting material. It is presumed that byproduct 17 would
be yielded by â-elimination with the terminal methyl
hydrogen from the π-allylpalladium intermediate. The
production of 17 is suppressed by employing the reac-
tion under a CO2 atmosphere, but a fair amount of
starting material remains (entry 2). Gratifyingly, the
desired cyclic carbonate 16 is selectively obtained in
85% yield when the reaction is carried out in the pres-
ence of dppe (entry 3). Similar reactivity is observed by
the use of dppb (64% yield), while diene 17 is predomi-
nantly formed when dppp and PPh3 are used (entries 4
and 6).
(∆δ ) δ(S)-ester - δ(R)-ester) (Figure 2), the absolute config-
uration of 16 is determined as S. Furthermore, it is
noteworthy that the enantiomeric excess of (S)-16 is
1
determined as 93% by H NMR integration of (S)- and
(R)-19. The result clearly shows that the CO2 recycling
reaction of allylic carbonate occurs with a transfer of
chirality. The observed high enantiospecificity is ex-
plained as follows (eq 10). The initial attack of the
The reaction using enantiomerically enriched chiral
allylic carbonate (S)-14 was next examined (eq 8). When
(S)-14 is subjected to the reaction in the presence of
palladium catalyst and dppe, chiral cyclic carbonate 16
is produced in 85% yield. The absolute configuration of
palladium complex to (S)-14 would proceed with conver-
sion of the stereochemistry to give π-allylpalladium
intermediate C and isomer D. It is expected that there
is equilibrium between C and D, and the nucleophilic
cyclization process would proceed via the more stable
intermediate D from the back side against the π-allylpal-
ladium species to afford (S)-16 without loss of chirality.
(10) (a) Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J . Am.
Chem. Soc. 1991, 113, 4092. For reviews about the determination of
absolute configuration by the use of MTPA esters, see: (b) Seco, J .
M.; Quin˜oa´, E.; Riguera, R. Tetrahedron: Asymmetry 2001, 12, 2915.
(c) Kusumi, T. J . Synth. Org. Chem., J pn. 1993, 51, 462.
1594 J . Org. Chem., Vol. 69, No. 5, 2004

Pd-Catalyzed CO2 Elimination-Fixation Reaction
(c) Syn th esis of Allylic Ben zoa te 4c. To a stirred solution
of diol 2c (151 mg, 0.66 mmol) and Et3N (0.18 mL, 1.32 mmol)
and a catalytic amount of DMAP in CH2Cl2 (10 mL) was added
dropwise benzoyl chloride (84 µL, 0.73 mmol) at 0 °C, and
stirring was continued for 1 h at the same temperature. The
reaction mixture was diluted with water and extracted with
AcOEt. The combined extracts were washed with aqueous
NH4Cl and saturated NaCl. The residue upon workup was
chromatographed on silica gel with hexane-AcOEt (80:20 v/v)
as eluent to give allylic benzoate 4c (219 mg, quantitative
Con clu sion
In conclusion, we have developed a novel type of CO2
recycling process involving a palladium-catalyzed reac-
tion of 4-methoxycarbonyloxy-2-buten-1-ols. This reaction
can create a variety of cyclic carbonates via a CO2
elimination-fixation process. trans-Cyclic carbonates are
generated with a high degree of stereochemical control
in the reactions of unsymmetric substrates. By the use
of chiral methyl-substituted allylic carbonates, an enan-
tiospecific reaction occurs to produce a chiral product with
high specificity. The CO2 fixation processes in the reac-
tions generally proceed with high efficiency. The reaction
should not only provide a new possibility of a CO2
recycling reaction but also gain the attention of scientists
searching for new eco-friendly chemical reactions.
1
yield) as a colorless oil: IR (neat) 2860, 1697, 1452 cm-1; H
NMR (400 MHz, CDCl3) δ 0.87 (6H, t, J ) 6.6 Hz), 1.21-1.31
(12H, m), 1.39 (1H, s), 1.46-1.56 (4H, m), 4.84 (2H, d, J ) 4.9
Hz), 5.80-5.91 (2H, m), 7.43 (2H, dd, J ) 7.8 and 7.8 Hz),
7.55 (1H, dd, J ) 7.8 and 7.8 Hz), 8.04 (2H, d, J ) 7.8 Hz); 13
C
NMR (75 MHz, CDCl3) δ 13.8, 22.4, 22.9, 32.1, 40.7, 65.0, 74.9,
122.1, 128.3, 129.6, 130.3, 132.9, 144.1, 166.4; MS m/z 314 [M+
- 18 (H2O)]. Anal. Calcd for C21H32O2: C, 75.86; H, 9.70.
Found: C, 75.70; H, 9.41.
Exp er im en ta l Section
Gen er a l P r oced u r e for th e P a lla d iu m -Ca ta lyzed Re-
action of tr a n s-4-Meth oxycar bon yloxy-2-bu ten -1-ols. Syn -
th esis of Cyclic Ca r bon a te 5a (En tr y 4 in Ta ble 1). To a
stirred solution of allylic carbonate 3a (56.0 mg, 0.28 mmol)
in dioxane (2.8 mL) were added Pd2(dba)3‚CHCl3 (14.5 mg, 14.0
µmol) and dppf (31.0 mg, 56.0 µmol) in a sealed tube at rt.
After stirring was continued for 1 h at 50 °C, the reaction
mixture was concentrated and the residue was chromato-
graphed on silica gel with hexane-AcOEt (80:20 v/v) as eluent
to give cyclic carbonate 5a (37.6 mg, 79%) as a colorless oil:
Gen er a l. Substrates 1a -1i and 2j were prepared by
following the literature.5b,11,12 Propargylic alcohol (S)-10 was
purchased from a commercial supplier. All nonaqueous reac-
tions were carried out under a positive atmosphere of argon
or nitrogen in dried glassware unless otherwise indicated.
Materials were obtained from commercial suppliers and used
without further purification except when otherwise noted.
Solvents were dried and distilled according to standard
protocols. The phrase “residue upon workup” refers to the
residue obtained when the organic layer was separated and
dried over anhydrous MgSO4 and the solvent was evaporated
under reduced pressure.
Gen er a l E xp er im en t a l P r oced u r e for Sch em e 1. (a )
Syn th esis of tr a n s-Allylic Alcoh ol 2a . To a stirred suspen-
sion of LAH (1.07 g, 28.2 mmol) and NaOMe (3.05 g, 56.4
mmol) in THF (120 mL) was added dropwise the solution of
propargylic diol 1a (2.00 g, 14.1 mmol) in THF (30 mL) at 0
°C. After refluxing for 3 h, the reaction mixture was treated
with the minimum amount of cold water at rt and extracted
with AcOEt. The combined extracts were washed with aqueous
NaHCO3 and saturated NaCl. The residue upon workup was
chromatographed on silica gel with hexane-AcOEt (60:40 v/v)
as eluent to give diol 2a (1.33 g, 66%) as colorless needles:
mp 57-58 °C; IR (KBr) 3344, 2967, 2936 cm-1; 1H NMR (400
MHz, CDCl3) δ 0.86 (6H, t, J ) 7.2 Hz), 1.50-1.59 (4H, m),
1.99 (1H, s), 2.69 (1H, s), 4.16 (2H, d, J ) 5.6 Hz), 5.66 (1H, d,
J ) 15.6 Hz), 5.81 (1H, dt, J ) 5.6 and 15.6 Hz); 13C NMR
(100 MHz, CDCl3) δ 7.8, 63.0, 75.1, 127.6, 136.7; MS m/z 115
[M+ - 29 (C2H5)]. Anal. Calcd for C8H16O2: C, 66.63; H, 11.18.
Found: C, 66.51; H, 10.91.
IR (neat) 3645, 2885, 1790, 1028 cm-1 1H NMR (300 MHz,
;
CDCl3) δ 0.97 (3H, t, J ) 7.8 Hz), 0.99 (3H, t, J ) 7.8 Hz),
1.56-1.88 (4H, m), 4.82 (1H, dt, J ) 6.9 and 1.2 Hz), 5.45 (1H,
dt, J ) 10.5 and 1.2 Hz), 5.51 (1H, dt, J ) 18.3 and 1.2 Hz),
5.88 (1H, ddd, J ) 18.3, 10.5, and 6.9 Hz); 13C NMR (75 MHz,
CDCl3) δ 6.8, 7.0, 25.5, 28.3, 84.0, 88.3, 121.0, 130.0, 154.0;
MS m/z 170 (M+). Anal. Calcd for C9H14O3: C, 63.51; H, 8.29.
Found: C, 63.69; H, 8.18.
P r oced u r e for th e P a lla d iu m -Ca ta lyzed Rea ction of
Allylic Ben zoa te u n d er CO2 Atm osp h er e (Eq 4). To a
stirred solution of allylic benzoate 4c (46.5 mg, 0.14 mmol) in
dioxane (1.4 mL) were added Pd2(dba)3‚CHCl3 (7.2 mg, 7.0
µmol), dppf (15.2 mg, 28.0 µmol), and BSA (50 µL, 0.21 mmol)
in a sealed tube at rt. After stirring was continued under CO2
atmosphere for 12 h at 50 °C, the reaction mixture was
concentrated and the residue was chromatographed on silica
gel with hexane-AcOEt (90:10 v/v) as eluent to give cyclic
carbonate 5c (26.3 mg, 74%) as a colorless oil.
Cr ossover Exp er im en t Usin g Allylic Ca r bon a te 3f a n d
Allylic Ben zoa te 4c (Eq 5). To a stirred solution of equimolar
amounts of allylic carbonate 3f (57.1 mg, 0.27 mmol) and allylic
benzoate 4a (89.7 mg, 0.27 mmol) in dioxane (2.7 mL) were
added Pd2(dba)3‚CHCl3 (27.9 mg, 27.0 µmol), dppe (43.0 mg,
0.11 mmol), and BSA (0.10 mL, 0.41 mmol) in a sealed tube
at rt. After stirring was continued for 12 h at 50 °C, the
reaction mixture was concentrated and the residue was
chromatographed on silica gel with hexane-AcOEt (90:10 v/v)
as eluent to give a 1:1.1 mixture of cyclic carbonates 5f and
5c (52.9 mg, 20% 5f and 22% 5c) and epoxide 9c (21.2 mg,
19%) as a colorless oil.
Gen er a l P r oced u r e for th e Dia ster eoselective Syn -
th esis of Cyclic Ca r bon a tes (Sch em e 3). Syn th esis of
tr a n s- a n d cis-5h . To a stirred solution of allylic carbonate
3h (50.0 mg, 0.21 mmol) in dioxane (2 mL) were added Pd2-
(dba)3‚CHCl3 (10.9 mg, 10.5 µmol) and dppf (22.9 mg, 42.0
mmol) in a sealed tube at rt. After stirring was continued for
4 h at 50 °C, the reaction mixture was concentrated and the
residue was chromatographed on silica gel with hexane-
AcOEt (95:5 v/v) as eluent to give cyclic carbonate trans-5h
(21.1 mg, 50%) as yellow needles and cis-5h (8.4 mg, 19%) as
a colorless oil.
(b) Syn th esis of Allylic Ca r bon a te 3a . To a stirred
solution of diol 2a (463 mg, 3.2 mol) and pyridine (0.78 mL,
9.6 mmol) in CH2Cl2 (35 mL) was added dropwise methyl
chloroformate (0.27 mL, 3.52 mmol) at 0 °C, and stirring was
continued for 1 h at the same temperature. The reaction
mixture was diluted with water and extracted with AcOEt.
The combined extracts were washed with aqueous NH4Cl and
saturated NaCl. The residue upon workup was chromato-
graphed on silica gel with hexane-AcOEt (85:15 v/v) as eluent
to give allylic carbonate 3a (595 mg, 92%) as a colorless oil:
IR (neat) 3345, 2967, 1732 cm-1; H NMR (300 MHz, CDCl3)
1
δ 0.85 (6Η, t, J ) 7.8 Hz), 1.54 (4H, dq, J ) 2.1 and 7.8 Hz),
2.01 (1H, s), 3.78 (3H, s), 4.65 (2H, dd, J ) 1.2 and 3.6 Hz),
5.77-5.80 (2H, m); 13C NMR (75 MHz, CDCl3) δ 7.3, 32.4, 54.3,
67.8, 74.8, 121.8, 140.7, 155.5; MS m/z 173 [M+ - 29 (C2H5)].
Anal. Calcd for C10H18O4: C, 59.39; H, 8.97. Found: C, 59.44;
H, 8.75.
(11) Shigemasa, Y.; Oikawa, H.; Ohrai, S.; Sashiya, H.; Saimoto,
H. Bull. Chem. Soc. J pn. 1992, 65, 2594.
(12) Bates, R. W.; D´ıez-Mart´ın, D.; Kerr, W. J .; Knight, J . G.; Ley,
S. V.; Sakellaridis, A. Tetrahedron 1990, 46, 4063.
Exp er im en ta l P r oced u r e for Sch em e 4. (a ) (S)-(ter t-
Bu tyld ip h en ylsiloxy)-1,1-d ip en tyl-2-p en tyn -1-ol [(S)-11].
J . Org. Chem, Vol. 69, No. 5, 2004 1595

Yoshida et al.
To a stirred solution of (S)-3-butyn-2-ol (S)-10 (696 mg, 9.93
mmol, 95% ee) and imidazole (1.35 g, 19.9 mmol) in DMF (14
mL) was added TBDPSCl (5.17 mL, 19.9 mmol) at rt, and
stirring was continued for 1 h at 50 °C. The reaction mixture
was diluted with water and extracted with AcOEt. The
combined extracts were washed with aqueous NH4Cl and
saturated aqueous NaCl. The residue upon workup was
chromatographed on silica gel with hexane-AcOEt (95:5 v/v)
as eluent to give TBDPS ether (3.06 g, quantitative yield) as
a colorless oil. To a stirred solution of the product (2.31 g, 7.7
mmol) and TMEDA (1 mL, 7.5 mmol) in THF (80 mL) was
added dropwise 1.60 M BuLi in THF (4.7 mL, 7.5 mmol) at
-78 °C. After stirring was continued for 2 h at -78 °C, a
solution of 6-undecanone (1.02 mL, 5.0 mmol) in THF (20 mL)
was added dropwise to this solution, and stirring was contin-
ued for 4 h at the same temperature. The reaction mixture
was diluted with water and extracted with AcOEt. The
combined extracts were washed with aqueous NH4Cl and
saturated NaCl. The residue upon workup was chromato-
graphed on silica gel with hexane-AcOEt (90:10 v/v) as eluent
to give propargylic alcohol (S)-11 (2.27 g, 95%) as a colorless
oil: [R] 2D5 ) -5.99 (c 10.2 in CDCl3); IR (neat) 3543, 3071,
with aqueous NH4Cl and saturated NaCl. The residue upon
workup was chromatographed on silica gel with hexane-
AcOEt (60:40 v/v) as eluent to give allylic carbonate (S)-14 (140
mg, 98%) as a colorless oil: [R] 2D9 ) -42.97 (c 10.0 in CDCl3);
IR (neat) 3499, 2930, 2860, 1732 cm-1 1H NMR (400 MHz,
;
CDCl3) δ 0.87 (6H, t, J ) 7.2 Hz), 1.28-1.34 (12H, m), 1.38
(4H, d, J ) 7.2 Hz), 1.45-1.52 (3H, m), 1.56 (1H, s), 3.76 (3H,
s), 5.19-5.25 (1H, m), 5.66 (1H, dd, J ) 16.0 and 5.6 Hz), 5.72
(1H, d, J ) 16.0 Hz); 13C NMR (75 MHz, CDCl3) δ 13.9, 20.5,
22.4, 22.9, 32.1, 40.8, 74.8, 74.9, 127.5, 139.0, 155.2; MS m/z
197 [M+ - 103 (CHCH3OCO2CH3)]; HRMS m/z calcd for
C
13H25O 197.1906 (M+ - 103), found 197.1893.
P r oced u r e for th e Syn th esis of MTP A Ester (S,S)-15.
(E,S)-1,1-Dip en tyl-4-[(S)-2-m eth oxy-2-tr iflu or om eth yl-2-
p h en yla cetyl]oxy-2-p en ten -1-ol [(S,S)-15]. To a stirred
solution of allylic diol (S)-13 (19.9 mg, 82 µmol) and NEt3 (57.0
µL, 0.41 mmol) and a catalytic amount of DMAP in CH2Cl2
(5.0 mL) was added dropwise (R)-MTPA chloride (17.0 µL, 90.0
µmol) at 0 °C, and stirring was continued for 2 h at the same
temperature. The reaction mixture was diluted with water and
extracted with Et2O. The combined extracts were washed with
1 N HCl, aqueous NaHCO3, and saturated NaCl. The residue
upon workup was chromatographed on silica gel with hexane-
AcOEt (80:20 v/v) as eluent to give MTPA ester (S,S)-15 (36.3
1
2932, 2859 cm-1; H NMR (300 MHz, CDCl3) δ 0.88 (6H, t, J
) 6.3 Hz), 1.06 (9H, s), 1.23-1.37 (12H, m), 1.41 (3H, d, J )
6.6 Hz), 1.45-1.57 (6H, m), 7.34-7.43 (6H, m), 7.68-7.77 (4H,
m); 13C NMR (100 MHz, CDCl3) δ 14.1, 19.2, 22.7, 23.8, 23.9,
25.4, 26.9, 32.0, 41.8, 59.9, 70.9, 86.4, 127.3, 127.5, 129.5, 129.6,
133.7, 133.9, 135.7, 135.9; MS m/z 421 [M+ - 57 (C4H9)];
HRMS m/z calcd for C27H37O2Si 421.2562 (M+ - 57), found
421.2549.
mg, quantitative yield, 95% ee) as a colorless oil: [R] D25
-42.51 (c 5.1 in CDCl3); IR (neat) 3439, 2936, 2862, 1751 cm-1
)
;
1H NMR (600 MHz, CDCl3) δ 0.840.88 (6H, m), 1.23-1.31
(12H, m), 1.36 (3H, d, J ) 6.2 Hz), 1.43-1.53 (4H, m), 3.54
(3H, s), 5.60-5.64 (1H, m), 5.68-5.72 (1H, m), 5.78 (1H, d, J
) 15.5 Hz), 7.37-7.42 (3H, m), 7.52 (2H, d, J ) 7.2 Hz); 13C
NMR (100 MHz, CDCl3) δ 14.0, 14.1, 20.4, 22.6, 22.6, 23.1,
32.2, 41.0, 41.1, 55.3, 73.7, 74.8, 126.2, 127.2, 127.3, 128.2,
129.4, 132.3, 140.2, 165.5; MS m/z 189 (M+ - 269); HRMS m/z
calcd for C9H8F3O 189.0527 (M+ - 269), found 189.0497.
P r oced u r e for th e En a n tiosp ecific Rea ction of (S)-14
(Eq 8). To a stirred solution of allylic carbonate (S)-14 (28.2
mg, 94.0 µmol) in dioxane (2 mL) were added Pd2(dba)3‚CHCl3
(4.9 mg, 4.7 µmol) and dppe (7.5 mg, 18.8 µmol) in a sealed
tube at rt. After stirring was continued for 7 h at 50 °C, the
reaction mixture was concentrated and the residue was
chromatographed on silica gel with hexane-AcOEt (90:10 v/v)
as eluent to give cyclic carbonate (S)-16 (21.8 mg, 85%) and
diene 17 (1.5 mg, 7%) as colorless oils.
(b) (S)-4-Hyd r oxy-1,1-d ip en t yl-2-p en t yn -1-ol [(S)-12].
To a stirred solution of propargylic alcohol (S)-11 (1.48 g, 3.1
mmol) in THF (30 mL) was added dropwise a 1.0 M solution
of TBAF in THF (6.2 mL, 6.20 mmol) at rt. After stirring was
continued for 1 h at the same temperature, the reaction
mixture was diluted with water and extracted with AcOEt.
The combined extracts were washed with saturated NaCl. The
residue upon workup was chromatographed on silica gel with
hexane-AcOEt (60:40 v/v) as eluent to give diol (S)-12 (745
mg, quantitative yield) as colorless needles: mp 35-38 °C;
[R] 2D9 ) -14.97 (c 10.5 in CDCl3); IR (neat) 3335, 2934, 2862
1
cm-1; H NMR (400 MHz, CDCl3) δ 0.90 (6H, t, J ) 6.8 Hz),
1.26-1.38 (8H, m), 1.42-1.51 (8H, m), 1.56-1.65 (3H, m), 1.98
(2H, s), 4.56 (1H, d, J ) 3.6 Hz); 13C NMR (100 MHz, CDCl3)
δ 14.0, 22.6, 23.9, 24.5, 31.9, 41.8, 58.3, 71.1, 86.0, 87.0; MS
m/z 387 [M+ - 71 (C5H11)]; HRMS m/z calcd for C20H26O4F3
387.1783 (M+ - 71), found 387.1776.
(a ) (E,S)-1,2-Dih yd r oxy-1,1-d ip en tyl-3-p en ten e [(S)-18].
To a stirred solution of cyclic carbonate (S)-16 (18.0 mg, 67.0
µmol) in dioxane (2.0 mL) was added 1 N NaOH (2.0 mL) at
rt. After stirring had been continued for 1 h at the same
temperature, the reaction mixture was diluted with water and
extracted with AcOEt. The combined extracts were washed
with aqueous NH4Cl and saturated NaCl. The residue upon
workup was chromatographed on silica gel with hexane-
AcOEt (90:10 v/v) as eluent to give chiral diol 18 (16.2 mg,
quantitative yield) as a colorless oil: [R] 2D6 ) -3.44 (c 1.6 in
(c) (E,S)-4-Hyd r oxy-1,1-d ip en tyl-2-p en ten -1-ol [(S)-13].
To a stirred suspension of LAH (190 mg, 5.0 mmol) and
NaOMe (546 mg, 10.0 mmol) in THF (40.0 mL) was added
dropwise the solution of propargylic diol (S)-12 (600 mg, 2.50
mmol) in THF (10.0 mL) at 0 °C. After the reaction mixture
was refluxed for 3 h, it was treated with the minimum amount
of cold water and extracted with AcOEt. The combined extracts
were washed with aqueous NaHCO3 and saturated NaCl. The
residue upon workup was chromatographed on silica gel with
hexane-AcOEt (60:40 v/v) as eluent to give diol (S)-13 (339
mg, 56%) as a colorless oil: [R] 2D9 ) +0.20 (c 10.0 in CDCl3);
1
CDCl3); IR (neat) 3418, 2932, 2955, 2680 cm-1; H NMR (300
MHz, CDCl3) δ 0.89 (6H, dt, J ) 1.5 and 7.2 Hz), 1.26-1.58
(16H, m), 1.74 (3H, dd, J ) 6.4 and 1.5 Hz), 1.83 (2H, brs),
3.94 (1H, d, J ) 7.5 Hz), 5.59 (1H, ddq, J ) 15.3, 7.5, and 1.5
Hz), 5.74 (1H, dd, J ) 15.3 and 6.4 Hz); 13C NMR (100 MHz,
CDCl3) δ 14.0, 22.5, 23.8, 24.4, 31.9, 41.8, 58.2, 71.1, 86.0, 86.9;
MS m/z 171 [M+ - 71 (C5H11)]; HRMS m/z calcd for C10H17O2
171.1749 (M+ - 71), found 171.1724.
1
IR (neat) 3366, 3225, 2858 cm-1; H NMR (400 MHz, CDCl3)
δ 0.88 (6H, t, J ) 6.4 Hz), 1.27-1.33 (16H, m), 1.40 (1H, s),
1.47-1.52 (3H, m), 1.66 (1H, s), 4.35 (1H, m), 5.63 (1H, d, J )
15.6 Hz), 5.71 (1H, dd, J ) 6.0 and 15.6 Hz); 13C NMR (100
MHz, CDCl3) δ 14.4, 22.7, 23.2, 23.8, 32.3, 40.9, 41.0, 68.5,
74.7, 132.0, 135.8; MS m/z 171 [M+ - 71 (C5H11)]; HRMS m/z
calcd for C10H19O2 171.1385 (M+ - 71), found 171.1385.
(d) (E,S)-1,1-Dipen tyl-4-m eth oxycar bon yloxy-2-pen ten -
1-ol [(S)-14]. To a stirred solution of diol (S)-13 (115 mg, 0.47
mmol) and pyridine (0.11 mL, 1.41 mmol) in CH2Cl2 (10 mL)
was added dropwise methyl chloroformate (40.0 µL, 0.52 mmol)
at 0 °C, and stirring was continued for 1 h at the same
temperature. The reaction mixture was diluted with water and
extracted with AcOEt. The combined extracts were washed
(b )
(E,S)-1,1-Dip en t yl-2-[(R)-2-m et h oxy-2-t r iflu or o-
m eth yl-2-p h en yla cetyl]oxy-3-p en ten -1-ol [(S,R)-19]. To a
stirred solution of chiral diol (S)-18 (4.0 mg, 16.5 µmol) and
NEt3 (11 µL, 82.3 µmol) and a catalytic amount of DMAP in
CH2Cl2 (2 mL) was added dropwise (S)-MTPA chloride (3.5 µL,
18.2 µmol) at 0 °C, and stirring was continued for 2 h at the
same temperature. The reaction mixture was diluted with
water and extracted with Et2O. The combined extracts were
washed with 1 N HCl, aqueous NaHCO3, and saturated NaCl.
The residue upon workup was chromatographed on silica gel
with hexane-AcOEt (85:15 v/v) as eluent to give MTPA ester
1596 J . Org. Chem., Vol. 69, No. 5, 2004

Pd-Catalyzed CO2 Elimination-Fixation Reaction
(S,R)-19 (5.1 mg, 70%) as a colorless oil: [R] 2D6 ) +12.53 (c
1.5 in CDCl3); IR (neat) 3537, 2928, 2856, 1732 cm-1; 1H NMR
(600 MHz, CDCl3) δ 0.87 (6H, t, J ) 7.2 Hz), 1.14-1.45 (16H,
m), 1.76 (3H, d, J ) 6.5 Hz), 3.55 (3H, s), 5.33 (1H, d, J ) 9.0
Hz), 5.60 (1H, qt, J ) 1.7, 9.0, and 15.5 Hz), 5.93-5.99 (1H,
m), 7.36-7.41 (3H, m), 7.51-7.54 (2H, m); 13C NMR (100 MHz,
CDCl3) δ 13.7, 14.0, 18.1, 19.2, 22.3, 22.5, 22.8, 30.5, 31.9, 32.2,
32.3, 34.2, 35.6, 55.5, 65.5, 75.3, 81.8, 124.2, 127.0, 128.2, 128.7,
129.4, 130.7, 132.1, 134.5, 165.4; MS m/z 458 (M+); HRMS m/z
calcd for C25H37O4F3 458.2644 (M+), found 458.2648.
CDCl3) δ 13.7, 14.0, 18.0, 19.2, 22.4, 22.5, 22.8, 30.6, 32.4, 34.5,
36.1, 55.4, 65.6, 82.1, 124.2, 127.7, 128.4, 128.9, 129.6, 131.0,
132.1, 133.9, 165.7; MS m/z 458 (M+); HRMS m/z calcd for
C
25H37O4F3 458.2644 (M+), found 458.2617.
Ack n ow led gm en t. This study was supported in
part by a Grant-in-Aid for Encouragements for Young
Scientists (B) from the J apan Society for the Promotion
of Science (J SPS) (for M.Y.) and Scientific Research on
Priority Areas (A) from the Ministry of Education,
Culture, Sports, Science and Technology, J apan.
(c)
(E,S)-1,1-Dip en t yl-2-[(S)-2-m et h oxy-2-t r iflu or o-
m eth yl-2-p h en yla cetyl]oxy-3-p en ten -1-ol [(S,S)-19]. By
following the same procedure described for (S,R)-19, MTPA
ester (S,S)-19 was prepared from allylic diol 18 and (R)-MTPA
chloride in 72% yield as a colorless oil: [R] 2D5 ) -17.40 (c 1.0
Su p p or t in g In for m a t ion Ava ila b le: Spectral data of
2b-2i, 3b-3j, 5b-5i, 9c, (S)-16, and 17, 1H NMR and 13C
NMR spectra for 2d , 2f-2i, 3c, 3d , 3f, 3g, 5b, 5d -5g, 9c, cis-
5h , and 11-19, and NOESY spectra for trans- and cis-5h and
5i. This material is available free of charge via the Internet
at http://pubs.acs.org.
in CDCl3); IR (neat) 3351, 2932, 2850, 1746 cm-1 1H NMR
;
(600 MHz, CDCl3) δ 0.88 (6H, t, J ) 7.2 Hz), 1.23-1.49 (16H,
m), 1.73 (3H, d, J ) 6.4 Hz), 3.51 (3H, s), 5.33 (1H, d, J ) 5.7
Hz), 5.46 (1H, qd, J ) 10.3, 5.7, and 2.7 Hz), 5.85-5.91 (1H,
m), 7.38-7.41 (3H, m), 7.49-7.54 (2H, m); 13C NMR (100 MHz,
J O0353280
J . Org. Chem, Vol. 69, No. 5, 2004 1597