Annulated butanolides by ring closing metathesis of diallyltetronic acid derivatives

Article abstract of DOI:10.1016/j.tetlet.2005.03.152

3,3-Diallyldihydrofuran-2,4-diones 5 with two identical allyl residues were obtained by Tsuji-Trost-type Pd-catalysed allylation of either 4-O-allyltetronates or 3-allyltetronic acids. Allylation of sodium 3-allyltetronate with a second allyl acetate gave mixed derivatives 5 as did the Claisen rearrangement of 4-O-allyl 3-allyltetronates 6 under microwave conditions. Compounds 5 and 6 were converted to butanolides with 3,3-spirocyclopentenyl or 3,4-cycloalkanyl annulation by ring closing metathesis with Grubbs catalysts.

Full text of DOI:10.1016/j.tetlet.2005.03.152

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 3657–3660
Annulated butanolides by ring closing metathesis
of diallyltetronic acid derivatives
*
Rainer Schobert and Juan Manuel Urbina-Gonzalez
´
Organisch-chemisches Laboratorium der Universita¨t, 95440 Bayreuth, Germany
Received 3 March 2005; revised 21 March 2005; accepted 22 March 2005
Available online 6 April 2005
Abstract—3,3-Diallyldihydrofuran-2,4-diones 5 with two identical allyl residues were obtained by Tsuji–Trost-type Pd-catalysed
allylation of either 4-O-allyltetronates or 3-allyltetronic acids. Allylation of sodium 3-allyltetronate with a second allyl acetate gave
mixed derivatives 5 as did the Claisen rearrangement of 4-O-allyl 3-allyltetronates 6 under microwave conditions. Compounds 5 and
6 were converted to butanolides with 3,3-spirocyclopentenyl or 3,4-cycloalkanyl annulation by ring closing metathesis with Grubbs
catalysts.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Numerous fungal and plant metabolites with spiro-
annulated c-butyrolactone structures have been re-
ported over the last few decades. As part of our ongoing
efforts towards the structural cores of the bakkanes,1 for
example bakkenolide A 1,2 and of compounds like
longianone 23 we explored the feasibility of double
allylation-ring closing metathesis sequences. 3,3-Diallyl-
dihydrofuran-2,4-diones with identical allyl residues
have been obtained by allylation of tetronic acids with
either allyl halides/base followed by thermal Claisen
rearrangement of the intermediate 3,4-diallyl tetro-
nates,4,5 or with allyl acetates under Pd catalysis result-
ing in moderate yields or product mixtures.6 Congeners
with two different allyl residues were not accessible like-
wise. A single ring closing metathesis, namely of sym-
metrical 3,3-diallyldihydrofuran-2,4-dione has been
reported.7 In this paper we investigate the generality of
such and similar approaches to 3-spiro and 4-spiro-
annulated or 3,4-fused butanolides as occurring in
natural products.
The most serious obstacle to using Pd-mediated allyl-
ation protocols8 is the mobility of allyl residues attached
to either the 3- or the 4-position of tetronic acids in the
presence of Pd0, which fact reflects the reversibility of
the C–C bond formation step under the customary con-
ditions. Both 3-allyltetronic acid 39 and 4-O-allyl tetro-
nates 4 when treated with Pd(Ph3P)4 in toluene at ca.
80 ꢁC ÔdisproportionatedÕ to give 30–40% of the corre-
sponding 3,3-diallyldihydrofuran-2,4-diones 5 besides a
similar quantity of easy to separate de-allylated tetronic
acids. The latter can also be converted to 5 by reaction
with an excess of external allyl acetate in the presence
of Pd0 and of a base such as DBU to increase their solu-
bility. As depicted in Scheme 1, symmetrical 3,3-diallyl-
dihydrofuran-2,4-diones 5a–c were obtained in good
yields from 4-O-allyltetronates 4 and allyl acetate.10
3-Allyl-3-cinnamyldihydrofuran-2,4-dione 5d, however,
was formed merely as a mixture with 5a and 3,3-di-
cinnamyldihydrofuran-2,4-dione, when allyltetronate
4a was treated with cinnamyl acetate (Scheme 1).
O
O
O
O
3
O
4
Yet ÔmixedÕ 3,3-diallyl derivatives were accessible in two
other ways. The first one exploits the fact that the above
mentioned Pd-mediated scrambling of allyl residues
requires elevated temperatures. By deprotonating 3-allyl-
tetronic acids with sodium alkoxides well soluble so-
dium tetronate salts with a more strongly nucleophilic
tetronate anion are obtained.11 These in turn are readily
allylated by a second external allyl acetate at 0 ꢁC
O
Bakkenolide A (1)
Longianone (2)
Keywords: Tetronic acid; Metathesis; Spiro compounds; Microwave.
*
Corresponding author. Tel.: +49 0921 552680; fax: +49 0921
552671; e-mail: rainer.schobert@uni-bayreuth.de
0040-4039/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.03.152

´
R. Schobert, J. M. Urbina-Gonzalez / Tetrahedron Letters 46 (2005) 3657–3660
3658
R4
OAc
Grubbs cat. (1st gen.)
CH2Cl2, 12 h, r.t.
or
R3
O
R3
O
(1-2 equiv)
O
O
Grubbs cat. (2nd gen.)
toluene, refl., 24 h
O
R4
2 mol-% Pd(Ph3P)4
toluene, 85˚C
O
O
O
R5
O
R5
O
R5
O
R5
O
R5 R4 [%]
[%]
90
Et 85
nBu 91
cat.a)
R3 R5
1st gen.
5
7a
7b
4
5 a
H
Et
H
H
H
65
90
82
H
H
H
H
1st gen.
b
c
d
7c 1st gen.
nBu
H
7d 2nd gen.
Ph 27 +othersa)
Me H 96
Scheme 1. 3,3-Diallyldihydrofuran-2,4-diones 5 from 4-O-allyltetro-
nates and allyl acetates under Tsuji conditions; (a) + 5a (26%) + 3,3-
dicinnamyldihydrofuran-2,4-dione (36%).
OSiMe3
OMe
O
O
7a
toluene, sealed tube
180˚C, 3 d
then 0.1 M HCl
O
without scrambling of the allyl residues at a noticeable
degree (Scheme 2, top).12 An alternative high-yielding
route to mixed 3,3-diallyldihydrofuran-2,4-diones 5 con-
sists of the esterification of 3-allyltetronic acids such as 3
with a different allylic alcohol13 followed by a thermal
Claisen rearrangement of the intermediate 4-O-allyl
3-allyltetronate 6 (Scheme 2, bottom).14 When carried
out under microwave irradiation the Claisen step pro-
ceeded quantitatively and without allyl scrambling.
The esterification of 3 with methallylic alcohol to give
6a was only possible under modified Mitsunobu condi-
tions15 while both the Steglich–Hassner as well as our
own isourea16 method failed completely.
O
8 (50%)
a)Grubbs catalysts:
Mes-N
N-Mes
PCy3
Cl
Cl
Ru
Ru
Cl
Cl
Ph
Ph
PCy3
PCy3
1
st gen.
2nd gen.
Scheme 3. 3,3-Spirocyclopentenyldihydrofuran-2,4-diones 7 and 3,4-
dispirobutanolide 8.
ucts were removed by treatment with 4 mol % of lead
tetraacetate according to Paquette et al.20 We then trea-
ted 7a with ethyl sorbinate in order to complete the bak-
kane framework via a Diels–Alder reaction with the
cyclopentene. No reaction was observed under classical
thermal (PhMe, sealed tube, 180 ꢁC) nor under Lewis
acid catalysed [2 mol % Yb(OTf)3 or EtAlCl2, 180 ꢁC,
PhMe] conditions. However, when compound 7a was
heated with DanishefskyÕs diene in a sealed tube in tol-
uene the corresponding hetero-Diels Alder 3,4-dispiro
adduct 8 was obtained instead in 50% yield after chro-
matography and recrystallisation (Scheme 3, middle).21
Ring closing metathesis reactions were then carried out
with bis-allyl tetronates of types 5 and 6 to build up the
structural target motifs of butanolides with 3,3-spiro-
cyclopentenyl, with 4,4-spiro-oxacycloalkanyl and with
3,4-cycloalkanyl annulation. Metathesis reaction of
various 3,3-diallylfurandiones 5 with Grubbs catalysts
gave 3,3-spirocyclopentenyldihydrofuran-2,4-diones 7
in good to excellent yields (Scheme 3, top). While first
generation catalyst (Pcy3)2Cl2Ru@CHPh was efficacious
in the RCM of derivatives with two C3H5 residues,17
a
second generation catalyst and harsh conditions were
required for the ring closure of 5e, most likely due to
sterical hinderance.18,19 Residual Ru compounds
responsible for a greyish to black hue of the crude prod-
RCM of 4-O-allyl 3-allyltetronates 6 led to the corre-
sponding furo[3,4-b]dihydrooxepines 9. Again, the
allyl-methallyl derivative 6a required a second genera-
tion Grubbs catalyst and forcing conditions causing a
concomitant shift of the double bond into a conjugated
position furnishing 9b (Scheme 4).17,18 Alkene
1) NaOMe, MeOH, 2 h, r.t.
2) PhCH=CHCH2OAc
2 mol-% Pd(Ph3P)4
THF/MeOH, 0˚C, 2 h
O
O
O
O
Ph
O
Grubbs cat. (1st gen.)
CH2Cl2, 12 h, r.t.
OH
O
O
O
3
5 d (80%)a)
R4 = H
O
O
R4
9a (85%)
toluene
190˚C, 20 min
microwave
O
O
O
O
Mitsunobu
(75%)
Grubbs cat. (2nd gen.)
toluene, refl., 24 h
O
O
(100%)
O
6
O
R
4 = Me
O
O
6a
5e
9b (50%)
Scheme 2. Mixed 3,3-diallyldihydrofuran-2,4-diones 5d,e; (a) + 5a
(8%) + 3,3-dicinnamyldihydrofuran-2,4-dione (5%).
Scheme 4. Furo[3,4-b]dihydrooxepines 9.

´
R. Schobert, J. M. Urbina-Gonzalez / Tetrahedron Letters 46 (2005) 3657–3660
3659
5.57 (2H, ddt, 3J 7.3, 9.7, 17.3 Hz); 13C NMR (75.5 MHz,
CDCl3): d 38.9, 53.9, 73.2, 121.2, 129.9, 175.6, 209.9; m/z
(EI) 180 (M+, 2%), 139 (64%), 79 (95%), 41 (100%).
Compound 5b: Rf 0.73 (hexane/Et2O, 3:2), red oil; mmax
(ATR)/cmÀ1 1797, 1751, 1211; 1H NMR (300 MHz,
CDCl3): d 0.98 (3H, t, 3J 7.5 Hz), 1.51–1.69 (1H, m),
1.72–1.89 (1H, m), 2.41 (4H, d, 3J 7.7 Hz), 4.29 (1H, dd, 3J
4.5, 8.6 Hz), 5.01–5.12 (4H, m), 5.46–5.65 (2H, m); 13C
NMR (75.5 MHz, CDCl3): d 9.6, 23.8, 37.9, 40.3, 54.5,
85.7, 120.8, 121.2, 129.9, 130.8, 175.3, 211.7; m/z (EI) 208
(M+, 5%), 166 (33%), 79 (100%), 41 (79%). Compound 5c:
Rf 0.83 (hexane/Et2O, 3:2), yellow oil; mmax (ATR)/cmÀ1
1798, 1755, 1214; 1H NMR (300 MHz, CDCl3): d 0.83
(3H, t, 3J 7.2), 1.10–1.40 (4H, m), 1.40–1.60 (1H, m), 1.65–
1.87 (1H, m), 2.41 (4H, dm, 3J 7.5 Hz), 4.34 (1H, dd,
3J 4.3, 9.1 Hz), 5.05 (2H, m), 5.11 (2H, m), 5.45–5.70
(2H, m); 13C NMR (75.5 MHz, CDCl3): d 13.6, 22.0, 27.3,
30.1, 38.1, 40.3, 54.5, 84.7, 120.8, 121.2, 129.9, 130.8,
175.4, 211.9; m/z (EI) 236 (M+, 5%), 194 (14%), 79
(100%), 41 (29%).
isomerisation as a side or a follow-up reaction to
metathesis processes initiated with Grubbs catalysts
has been frequently reported, especially for allylic alco-
hols and allyl ethers.22
In conclusion two efficient syntheses of 3,3-diallyl-
dihydrofurandiones-2,4 5 with different allyl residues
were developed, one by Pd-catalysed Tsuji allylation of
the sodium salts of 3-allyltetronic acids, the other by
Claisen rearrangement of 4-O-allyl 3-allyltetronates.
Ring-closing metathesis of 5 with Grubbs catalysts
furnished 3-spirocyclopentenyldihydrofurandiones-2,4
7 while RCM of the 4-O-allyl 3-allyltetronate precursors
gave furo[3,4-b]dihydrooxepinones 9. In line with the
known literature on RCM, the proper choice of the cat-
alyst very much depends on the degree of substitution of
the olefins.
11. Sodeoka, M.; Sampe, R.; Kojima, S.; Baba, Y.; Morisaki,
N.; Hashimoto, Y. Chem. Pharm. Bull. 2001, 49(2), 206–
212.
Acknowledgements
12. Compound 5d from 3: 3 (200 mg, 1.43 mmol), NaOMe
(79.5 mg, 1.43 mmol) and dry MeOH (10 mL) were stirred
at rt for 2 h. The solvent was removed to give a
hygroscopic sodium salt, which was re-dissolved in
THF/MeOH and stirred with Pd(Ph3P)4 (32 mg,
2 mol %) and cinnamyl acetate (276 mg, 1.57 mmol) at
0 ꢁC in the dark for 2 h. Filtration over Celiteꢂ, concen-
tration and CC (silica gel 60; hexane/Et2O, 2:3, v/v; Rf
0.72) left a colourless oil (292 mg, 80%); mmax (ATR)/cmÀ1
1801, 1753, 1218; 1H NMR (300 MHz, CDCl3): d 2.48
Financial support from the Deutsche Forschungsgeme-
inschaft (Grant Scho 402/7-1) is gratefully acknowl-
edged.
References and notes
1. (a) Fischer, N. H.; Oliver, E. J.; Fischer, H. D. In Progress
in the Chemistry of Organic Natural Products; Herz, W.,
Grisebach, H., Kirby, G. W., Eds.; Springer: New York,
1979; Vol. 38, Chapter 2; (b) Silva, L. F. Synthesis 2001,
671–689.
2. (a) Abe, N.; Onoda, R.; Shirahata, K.; Kato, T.; Woods,
M. C.; Kitahara, Y. Tetrahedron Lett. 1968, 9(3), 369–373;
(b) Brocksom, T. J.; Coelho, F.; Depres, J.; Greene, A. E.;
Freire de Lima, M. E.; Hamelin, O.; Hartmann, B.;
Kanazawa, A.; Wang, Y. J. Am. Chem. Soc. 2002, 124,
15313–15325.
3. Edwards, R. L.; Maitland, D. J.; Oliver, C. L.; Pacey, M.
S.; Shields, L.; Whalley, A. J. S. J. Chem. Soc., Perkin
Trans. 1 1999, 715–719.
4. Momose, T.; Toyooka, N.; Nishio, M.; Shinoda, H.; Fujii,
H.; Yanagino, H. Heterocycles 1999, 51(6), 1321–1343.
5. Kotha, S.; Mandal, K.; Deb, A. C.; Banerjee, S. Tetra-
hedron Lett. 2004, 45, 9603–9605.
3
3
(2H, d, J 7.3 Hz), 2.59 (2H, d, J 7.4 Hz), 4.30 (2H, s),
3
2
3
2
5.10 (1H, dd, J 10.2, J 1.5 Hz), 5.10 (1H, dd, J 17.0, J
1.5 Hz), 5.56 (1H, ddt, 3J 17.0, 10.2, 7.3 Hz), 5.93 (1H, dt,
3J 15.8, 7.4 Hz), 6.40 (1H, d, J 15.8 Hz), 7.12–7.24 (5H,
3
m); 13C NMR (75.5 MHz, CDCl3): d 38.3, 39.1, 54.3, 73.3,
120.8, 121.3, 126.4, 127.9, 128.3, 129.9, 136.0, 136.1,
175.8, 210.1; m/z (EI) 256 (M+, 4%), 215 (6%), 117 (100%),
104 (35%).
13. Compound 6a from 3: DIAD (940 mg, 4.65 mmol) was
added dropwise to Ph3P (1.22 g, 4.65 mmol) in THF
(10 mL) at À78 ꢁC whereupon a white solid formed. 3
(500 mg, 3.57 mmol) in THF (5 mL) was slowly added at
À78 ꢁC. After addition of methallylic alcohol (390 mg,
5.41 mmol) to the clear solution it was warmed to rt while
stirring and treated with aqueous NaHCO3 solution
(pH 10) and Et2O (3 · 10 mL). Drying and concentrating
of the organic layers and CC (silica gel 60; hexane/Et2O,
2:3, v/v; Rf 0.57) of the residue afforded a colourless oil
(519 mg, 75%); mmax (ATR)/cmÀ1 1746, 1667, 1045; 1H
6. (a) Prat, M.; Moreno-Man˜as, M.; Ribas, J. Tetrahedron
1988, 44(23), 7205–7212; (b) Moreno-Man˜as, M.; Prat,
M.; Ribas, J.; Virgili, A. Tetrahedron Lett. 1988, 29(5),
581–584.
3
NMR (300 MHz, CDCl3): d 1.72 (3H, s), 2.94 (2H, d, J
7. Kotha, S.; Deb, A. C.; Kumar, R. V. Bioorg. Med. Chem.
Lett. 2005, 15(4), 1039–1043.
8. Tsuji, J. In Handbook of Organopalladium Chemistry for
Organic Synthesis; Negishi, E., Ed.; John Wiley & Sons,
2002, p 1669.
6.2 Hz), 4.49 (2H, s), 4.64 (2H, s), 4.95 (2H, m), 4.96 (2H,
mc), 5.81 (1H, ddt, 3J 6.2, 10.0, 17.0 Hz); 13C NMR
(75.5 MHz, CDCl3): d 18.7, 26.2, 65.5, 73.6, 101.2, 113.8,
115.5, 134.2, 139.2, 172.4, 174.3; m/z (EI) 194 (M+, 10%),
161 (27%), 139 (60%), 55 (100%).
9. Schobert, R.; Gordon, G. J.; Mullen, G.; Stehle, R.
Tetrahedron Lett. 2004, 45(6), 1121–1124.
14. Compound 5e from 6a: 6a (500 mg, 2.57 mmol) in toluene
(8 mL) was irradiated in a microwave oven (CEM
Discoveryꢂ) at 190 ꢁC for 20 min. Removal of the solvent
and CC (silica gel 60; hexane/Et2O, 2:3, v/v; Rf 0.76) left a
colourless oil (500 mg, 100%); mmax (ATR)/cmÀ1 1804,
1754, 1044; 1H NMR (300 MHz, CDCl3): d 1.65 (3 H, dd,
10. Compound 5a7 from 4a—typical procedure: 4a12 (500 mg,
3.6 mmol), Pd(Ph3P)4 (80 mg, 2 mol %), allyl acetate
(390 mg, 3.9 mmol) and toluene (10 mL) were stirred in
the dark at 85 ꢁC for 2 h. Filtration over Celiteꢂ, removal
of the solvent and column chromatography (CC) (silica gel
60; hexane/Et2O, 2:3, v/v; Rf 0.78) left a colourless liquid
(418 mg, 65%); mmax (ATR)/cmÀ1 1802, 1752, 1214; 1H
3
4
4J 0.9, 1.4 Hz), 2.47 (2H, ddd, J 7.3, J 1.4, 1.2 Hz), 2.50
(2H, s), 4.38 (2H, s), 4.68 (1H, m), 4.83 (1H, m), 5.12 (1H,
3
m), 5.13 (1H, m), 5.60 (1H, ddt, J 17.3, 9.7, 7.3 Hz); 13C
3
NMR (300 MHz, CDCl3): d 2.44 (4H, d, J 7.3 Hz), 4.35
(2H, s), 5.08 (2H, d, J 9.7 Hz), 5.09 (2H, d, J 17.3 Hz),
NMR (75.5 MHz, CDCl3): d 23.8, 40.3, 42.6, 54.2, 73.6,
3
3
116.1, 121.4, 129.8, 139.4, 176.2, 210.2; m/z (EI) 194 (M+,

´
R. Schobert, J. M. Urbina-Gonzalez / Tetrahedron Letters 46 (2005) 3657–3660
3660
2
2
2%), 176 (50%), 139 (88%), 55 (100%). Satisfactory
microanalyses (C, 0.2; H, 0.1) were obtained for 5a–e.
2J 15.3 Hz), 2.73 (1H, dm, J 15.3 Hz), 2.69 (1H, dm, J
17 Hz), 2.81 (1H, d, 2J 17 Hz), 4.63 (2H, d, 5J 1.7 Hz), 5.22
(1H, m); 13C NMR (75.5 MHz, CDCl3): d 15.6, 42.6, 45.4,
51.5, 72.1, 120.7, 137.4, 177.7, 209.2; m/z (EI) 166 (M+,
64%), 124 (41%), 93 (36%), 79 (100%). Compound 9b: Rf
0.77 (Et2O), colourless oil; mmax (ATR)/cmÀ1 1747, 1647,
1009; 1H NMR (300 MHz, CDCl3): d 1.10 (3H, d, 3J
15. Tahir, H.; Hindsgaul, O. J. Org. Chem. 2000, 65, 911–913.
16. Schobert, R.; Siegfried, S. Synlett 2000, 686–687.
17. Compound 7a from 5a—typical procedure: 5a (330 mg,
1.8 mmol) dissolved in dry CH2Cl2 (15 mL) was treated
with (Pcy3)2Cl2RuCHPh (30 mg, 2 mol %) and the mix-
ture was stirred for 24 h at rt. Pb(OAc)4 (32 mg, 4 mol %)
was added and stirring was continued for a further 20 h.
Filtration over a Celiteꢂ plug (3 cm), concentration of the
filtrates and CC (silica gel 60; Et2O; Rf 0.64) left a white
powder (250 mg, 90%), mp 72 ꢁC; mmax (ATR)/cmÀ1 1781,
1745, 1246, 1047; 1H NMR (300 MHz, CDCl3): d 2.70–
2.92 (4H, m), 4.65 (2H, s), 5.65 (2H, s); 13C NMR
(75.5 MHz, CDCl3): d 42.4, 50.8, 72.1, 127.4, 177.6, 209.3;
m/z (EI) 152 (M+, 80%), 110 (41%), 94 (33%), 66 (100%).
Compound 7b: Rf 0.63 (hexane/Et2O, 2:3), yellow oil; mmax
(ATR)/cmÀ1 1796, 1747, 1242, 1046; 1H NMR (300 MHz,
CDCl3): d 0.99 (3H, t, 3J 7.4 Hz), 1.70–1.88 (1H, m), 1.88–
2.05 (1H, m), 2.68 (1H, d, 2J 16.5 Hz), 2.74 (1H, d, 2J
16.2 Hz), 2.86 (1H, d, 2J 16.5 Hz), 2.86 (1H, d, 2J 16.2 Hz),
4.70 (1H, dd, 3J 4.8, 7.0 Hz), 5.63 (2H, s); 13C NMR
(75.5 MHz, CDCl3): d 8.8, 24.7, 42.1, 43.2, 50.9, 84.7,
126.9, 127.6, 177.4, 211.7; m/z (EI) 180 (M+, 73%), 110
(13%), 94 (95%), 66 (100%). Compound 7c: Rf 0.59
(hexane/Et2O, 2:3), yellow oil; mmax (ATR)/cmÀ1 1798,
1749, 1250, 1052; 1H NMR (300 MHz, CDCl3): d 0.84
3
7.4 Hz), 2.77 (1H, m), 4.14 (1H, dd, J 5.9, 10.9 Hz), 4.26
(1H, dd, 3J 1.1, 10.9 Hz), 4.58 (2H, s), 5.85 (1H, dd, 3J 5.1,
10.6 Hz), 6.05 (1H, d, J 10.6 Hz); 13C NMR (75.5 MHz,
3
CDCl3): d 16.6, 37.8, 66.4, 76.8, 102.3, 117.6, 137.0, 173.0,
173.4; m/z (EI) 166 (M+, 100%), 151 (59%), 124 (42%), 79
(74%). Satisfactory microanalyses (C, 0.2; H, 0.2) were
obtained for 7a–c and 9a,b.
19. A similar observation has been reported recently for the
RCM of 2,3-bisalkenylcyclopentanones to give [5.7]bicy-
cles: Michalak, K.; Michalak, M.; Wicha, J. Tetrahedron
Lett. 2005, 46(7), 1149–1153.
20. Paquette, L. A.; Schloss, J. D.; Efremov, I.; Fabris, F.;
´
Gallou, F.; Mendez-Andino, J.; Yang, J. Org. Lett. 2000,
2(9), 1259–1261.
21. Compound 8: 1-Methoxy-3-trimethylsiloxy-1,3-butadiene
(490 mg, 2.84 mmol) in toluene (10 mL) was treated with
7a (220 mg, 1.45 mmol) at 0 ꢁC and the resulting mixture
was heated in a sealed tube for 3 days at 180 ꢁC. 15 mL of
a mixture of THF (35 mL) and 0.1 N aqueous HCl
(15 mL) were added at rt and stirring continued for 1 min.
The residual acid solution (35 mL) was added and the
resulting solution poured into AcOEt (50 mL) and treated
with H2O (25 mL). The organic layer was separated and
the aqueous one was extracted with AcOEt (4 · 20 mL).
The combined extracts were dried and concentrated and
the residue was purified by CC (silica gel 60; Et2O; Rf
0.53); white powder, mp 113 ꢁC; mmax (ATR)/cmÀ1 1767,
1675, 1039, 1005; 1H NMR (300 MHz, CDCl3): d 2.46
3
(3H, t, J 6.9 Hz), 1.22–1.45 (4H, m), 1.60–1.76 (1H, m),
1.77–1.95 (1H, m), 2.65 (1H, d, 2J 15.7 Hz), 2.70 (1H, d, 2J
15.5 Hz), 2.82 (1H, d, 2J 15.7 Hz), 2.83 (1H, d, 2J 15.5 Hz),
4.71 (1H, dd, 3J 4.5, 7.9 Hz), 5.60 (2H, s); 13C NMR
(75.5 MHz, CDCl3): d 13.5, 21.9, 26.6, 30.9, 42.2, 43.1,
50.8, 83.7, 126.9, 127.5, 177.3, 211.7; m/z (EI) 208 (M+,
21%), 110 (5%), 94 (100%), 66 (84%). Compound 9a: Rf
0.32 (hexane/Et2O, 2:3), white powder, mp 86 ꢁC; mmax
1
2
4
2
(ATR)/cmÀ1 1734, 1662, 1019, 921; H NMR (300 MHz,
(1H, dd, J 17.2, J 1.1 Hz), 2.53 (2H, m), 2.81 (1H, d, J
17.2 Hz), 2.71–2.82 (1H, m), 2.84–2.95 (1H, m), 4.00 (1H,
CDCl3): d 3.08 (2H, ddd, 3J 5.6, 4J1.5, 5J 1.6 Hz), 4.46
(2H, t, 5J 1.6 Hz), 4.73 (2H, dd, 3J 7.0, 4J 0.4 Hz), 5.96
(1H, dtt, 3J 7.0, 10.4, 4J 1.5 Hz), 6.25 (1H, ddt, 3J 5.6, 10.4,
4J 0.4 Hz); 13C NMR (75.5 MHz, CDCl3): d 22.1, 66.7,
67.6, 99.6, 125.4, 137.2, 174.1, 174.2; m/z (EI) 152 (M+,
70%), 66 (100%), 54 (49%), 39 (59%).
2
2
3
d, J 10.6 Hz), 4.51 (1H, d, J 10.6 Hz), 5.46 (1H, dd, J
6.2, 4J 1.1 Hz), 5.50–5.57 (1H, m), 5.70–5.77 (1H, m), 7.23
(1H, d, J 6.2 Hz); 13C NMR (75.5 MHz, CDCl3): d 35.3,
3
37.4, 38.6, 54.9, 71.5, 88.9, 107.2, 125.9, 130.1, 160.9,
178.8, 188.5; m/z (EI) 220 (M+, 46%), 110 (97%), 91
(100%), 71 (91%). Found: C, 65.3; H, 5.6. C12H12O4
requires C, 65.5; H, 5.5.
18. Compound 7d from 5e—typical procedure: 5e (250 mg,
1.8 mmol) dissolved in dry toluene (15 mL) was treated
with
benzylidene-[1,3-bis-(2,4,6-trimethylphenyl)-2-imi-
22. (a) Sutton, A. E.; Seigal, B. A.; Finnegan, D. F.; Snapper,
M. L. J. Am. Chem. Soc. 2002, 124, 13390–13391; (b)
Bourgeois, D.; Pancrazi, A.; Nolan, S. P.; Prunet, J.
J. Organomet. Chem. 2002, 643/644, 247–252; (c) Sworen,
J. C.; Pawlowa, J. H.; Case, W.; Lever, J.; Wagener, K. B.
J. Mol. Cat. A: Chem. 2003, 194, 69–78; (d) Lehman, S. E.;
Schwendeman, J. E.; OÕDonnell, P. M.; Wagener, K. B.
Inorg. Chim. Acta 2003, 345, 190–198.
dazolidinylidene]-dichloro(tricyclohexylphosphane)ruthe-
nium C46H65Cl2N2PRu (44 mg, 4 mol %) and the mixture
was stirred at 110 ꢁC for 24 h. Pb(OAc)4 (23 mg, 4 mol %)
was added at rt and stirring was continued for a further
20 h. Workup as for 7a gave a colourless oil of Rf 0.46
(Et2O); mmax (ATR)/cmÀ1 1807, 1791, 1750, 1042; 1H
NMR (300 MHz, CDCl3): d 1.72 (3H, m), 2.60 (1H, dm,