Highly enantioselective addition of trimethylsilylacetylene to aldehydes catalyzed by a zinc-amino-alcohol complex

Article abstract of DOI:10.1002/chem.201100535

A fine addition! A highly enantioselective and efficient procedure for the amino-alcohol-zinc-catalyzed addition of trimethylsilylacetylene to aromatic, α,β-unsaturated, and aliphatic aldehydes has been developed (see scheme; R=aryl, alkynyl, or alkyl; TMS=trimethylsilyl; TBDMS=tert- butyldimethylsilyl). The present protocol was successfully applied in the concise synthesis of the natural products marine alkynol and falcarindiol. Copyright

Full text of DOI:10.1002/chem.201100535

DOI: 10.1002/chem.201100535
Highly Enantioselective Addition of Trimethylsilylacetylene to Aldehydes
Catalyzed by a Zinc–Amino-Alcohol Complex
Zhi-Yuan Li, Min Wang, Qing-Hua Bian, Bing Zheng, Jian-You Mao, Shuo-Ning Li,
Shang-Zhong Liu, Ming-An Wang, Jiang-Chun Zhong,* and Hong-Chao Guo*[a]
The enantioselective alkynylation of aldehydes is one of
the most useful carbon–carbon bond-forming reactions for
the preparation of chiral propargylic alcohols,[1] which are
versatile building blocks for fine chemicals, pharmaceuticals,
and natural products.[2,3] Accordingly, much progress has
been made in the asymmetric addition of terminal alkynes
to aldehydes, which has been established as a reliable plat-
form for the efficient synthesis of a wide array of chiral
propargylic alcohols.[1,4] Various alkyne derivatives such as
arylacetylene, alkylacetylene, ethynylcyclohexene, acetalace-
tylene, methyl propiolate, 1,3-diyne, and trimethylsilylacety-
lene have been used as the alkyne nucleophiles.[1] Among
these nucleophiles, trimethylsilylacetylene is highly attrac-
tive due to the potential application of the corresponding
trimethylsilyl alkynol product. The product can be easily de-
silylated to give the corresponding terminal alkynol, which
can further be used as the precursor to carry out the alkyla-
tion or the Sonogashira coupling for the synthesis of some
natural products and useful chemicals.[5] A variety of effec-
tive catalytic systems including amino-alcohol–Zn,[6] imino-
alcohol–Zn,[7] hydroxyl-carboxyamide–Zn,[8] proline-derived
dinuclear Zn,[4i] bisoxazolidine–Zn,[4j] 1,1’-bi-2-naphthol
(BINOL)–Ti,[9] bisphosphine–CuI,[10] sulfonamide-alcohol–
Ti,[11] and bis(oxazolinyl)phenyl–Ru[4q] have been developed
for the addition of trimethylsilylacetylene to aldehydes. In
particular, by using catalytic systems such as Trostꢀs proline-
derived dinuclear Zn,[4i] Wolfꢀs bisoxazolidine–Zn,[4j] Puꢀs
BINOL–Ti,[9b] Wangꢀs sulfonamide alcohol–Ti,[11] and Nish-
iyamaꢀs bis(oxazolinyl)-phenyl–Ru,[4q] excellent enantiose-
lectivity (>90% enantiomeric excess (ee)) can be achieved
in the addition of trimethylsilylacetylene to aldehydes.
Among the catalytic systems reported so far for the alkyny-
lation of aldehydes, the amino-alcohol–Zn system is particu-
larly noteworthy in terms of its operational simplicity and
mild reaction conditions. The amino-alcohol–Zn catalytic
system has attracted much attention since the pioneering
contribution from Carreira and co-workers, who demon-
strated that by using a combination of Zn(OTf)2 and N-
AHCTUNGTRENNUNG
methylephedrine, the addition of terminal acetylenes to al-
dehydes afforded the desired products in high yields and
enantioselectivities.[4b,12] However, to the best of our knowl-
edge, no impressive amino-alcohol–Zn system (except for
Trostꢀs dinuclear Zn catalyst) for the alkynylation of alde-
hydes with trimethylsilylacetylene has been reported so far,
therefore
a new, generally applicable procedure using
amino-alcohol–Zn would still be highly desirable.[13] In this
context, we conceived the possibility of introducing a new
type of 1, 4-amino alcohol, based on the chiral cyclopropane
backbone (1–3), which might serve as an excellent chiral
ligand in the alkynylation of aldehydes with trimethylsilyl-
acetylene. Herein, we report the highly enantioselective ad-
dition of trimethylsilylacetylene to a wide range of alde-
hydes catalyzed by the zinc complexes of chiral 1,4-amino
alcohols.
Recently we reported a series of chiral amino alcohols
based on the cyclopropane backbone, which exhibited an
advantageous combination of structural rigidity, low molecu-
lar weight on a well-defined and highly variable platform,
and unusual bond angles. By using these amino alcohols in
combination with dialkylzinc, the addition of dialkylzinc or
some alkyne derivatives to aldehydes could be carried out
with high enantioselectivity.[4o,13] As a continuing effort to
develop highly enantioselective alkynylation catalysts, we
speculated that modification of the ligand structure, by in-
troducing another chiral center on the side chain of the
chiral cyclopropane backbone, might provide extra steric
discriminations that may enhance the enantioselectivity.
With this in mind, new chiral ligands 1, 2, and 3 were de-
signed and synthesized by introduction of the (R)- and (S)-
prolinols into the side chain of a chiral cyclopropane back-
bone by using a four-step reaction (Scheme 1). To increase
the steric effect, the hydroxyl group in prolinol was protect-
ed with tert-butyldimethylsilyl (TBDMS) or tert-butyldiphe-
nylsilyl (TBDPS).
[a] Z.-Y. Li, Dr. M. Wang, Dr. Q.-H. Bian, B. Zheng, J.-Y. Mao, S.-N. Li,
Dr. S.-Z. Liu, Dr. M.-A. Wang, Dr. J.-C. Zhong, Dr. H.-C. Guo
Department of Applied Chemistry, China Agricultural University
2 Yuanmingyuan West Road, Beijing 100193 (P.R. China)
Fax : (+86)10-62820325
With the amino alcohols 1, 2, and 3 in hand, our initial at-
tempts at amino-alcohol–Zn-catalyzed asymmetric addition
of trimethylsilylacetylene to aldehydes commenced with the
reactions of benzaldehyde and trimethylsilylacetylene.
Table 1 presents the results of the model reaction between
benzaldehyde and trimethylsilylacetylene, in which we es-
tablished appropriate reaction conditions by screening
E-mail: dr_zhongjiangchun@yahoo.com.cn
hchguo@gmail.com
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201100535.
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Chem. Eur. J. 2011, 17, 5782 – 5786

COMMUNICATION
tained in slightly improved yield, albeit with a slightly lower
ee value (Table 1, entry 1 vs. entry 6).
By using 1 (10 mol%) as the ligand, a range of aromatic
aldehydes were examined in toluene at 308C (Table 2). A
variety of aromatic aldehydes underwent the addition reac-
Table 2. Enantioselective addition of trimethylsilylacetylene to aromatic
aldehydes.[a]
Entry
R
Yield
[%][b]
ee
Scheme 1. Synthesis of amino alcohol ligands. TBS=tert-butylsilyl. Reac-
tion conditions: a) TsOH (0.2 equiv), CH3OH, reflux, 5 h, CH3CO2Na
(0.4 equiv), and (COOH)2 (0.5% aq.). b) NaBH3CN(0.5 equiv), Prolinol
(2 equiv), H2SO4 (0.5 equiv), and CH3OH. c) PhMgCl (4 equiv), and
THF at room temperature, 24 h. d) tert-butyldimethylsilyl (TBDMS) or
tert-butyldiphenylsilyl (TBDPS) (2 equiv), imidazole (3 equiv), and
CH2Cl2.
[%][c]
1
Ph
oFC6H4
mFC6H4
pFC6H4
78
62
61
66
62
77
78
76
70
72
84
84
73
60
94
94
93
96
96
95
94
95
94
96
97
95
94
90
2[d]
3[d]
4
5
pClC6H4
6[d]
7[d]
8
oCH3C6H4
mCH3C6H4
pCH3C6H4
oCH3OC6H4
mCH3OC6H4
pCH3OC6H4
1-naphthyl
2-naphthyl
1-furaldehyde
9
Table 1. Enantioselective addition of trimethylsilylacetylene to benzalde-
hyde catalyzed by ligands 1–3.[a]
10
11
12
13
14
[a] Three equivalents of trimethylsilylacetylene were used. [b] Yield of
isolated product. [c] Determined by HPLC. [d] Absolute configuration
has not been assigned.
Entry
Ligand
T [oC]
t [h]
Yield [%][b]
ee [%][c]
1
2
3
4
1
2
3
1
1
1
30
30
30
24
24
24
48
48
24
78
58
80
48
trace
83
94
36
92
94
n.d.
93
0
tion, providing the anticipated chiral alkynol products in
good yields and with consistently excellent ee values
5
À20
6[d]
30
A
[a] Three equivalents of trimethylsilylacetylene were used. [b] Yield of
isolated product. [c] Determined by HPLC. [d] 20 mol% of ligand was
used.
groups, with electron-donating or withdrawing substituents
on the benzene ring, could be tolerated in the process; in
particular, when 4-methoxybenzaldehyde was used as sub-
strate, the best ee value of 97% was obtained (Table 2,
entry 11). In addition, aromatic aldehydes with 1-naphthyl
(Table 2, entry 12), 2-naphthyl (entry 13), or heteroaryl
groups such as 1-furyl (entry 14) also smoothly underwent
the addition reaction, to readily afford the corresponding al-
kynol products with excellent enantioselectivities (90–
95% ee) and in good yields (Table 2, entries 12–14). All
these results demonstrate the high efficiency of the new
amino alcohol ligand 1.
After successfully evaluating the alkynylation of aromatic
aldehydes with trimethylsilylacetylene, we were delighted to
find out that even a,b-unsaturated and aliphatic aldehydes
could also undergo the alkynylation reaction in the presence
of amino alcohol 1, albeit with a slightly lower ee value
amino alcohols under different conditions. Initially, benzal-
dehyde was treated with trimethylsilylacetylene in toluene
at 308C in the presence of 1 (10 mol%), and the reaction
proceeded smoothly to give the corresponding propargylic
alcohols in 78% yield and with an excellent 94% ee
(Table 1, entry 1). In sharp contrast, whereas ligand 2 was
employed under otherwise identical conditions, the alkyny-
lation reaction only afforded the product in 58% yield and
with a poor 36% ee (Table 1, entry 2). On the contrary,
ligand 3, with the same configuration as ligand 1, could de-
liver the product in 80% yield, albeit with a slightly lower
92% ee (Table 1, entry 3). This shows that the chiral center
in pyrrolidine plays the decisive role, which explains the dra-
matic differences in the catalytic results. In the presence of
1 (10 mol%), lowering the reaction temperature to 08C re-
sulted in a dramatic decrease in reactivity (Table 1, entry 1
vs. entry 4). When the reaction temperature continued to be
lowered to À208C, the catalyst was nearly inert (Table 1,
entry 1 vs. entry 5). When the amount of ligand 1 was in-
creased from 10 to 20 mol%, the alkynol product was ob-
(Table 3, entries 1–13). Initially, by using
10 mol% of 1, the alkynylation reaction proceeded to afford
the product with 63% ee and a poor yield of 40% (Table 3,
entry 1). After the catalyst loading was increased to
20 mol%, the product was obtained with an improved
83% ee and in 68% yield (Table 3, entry 2). Therefore, the
reaction of a range of distinctly substituted a,b-unsaturated
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J.-C. Zhong, H.-C. Guo et al.
Table 3. Enantioselective addition of trimethylsilylacetylene to a,b-unsa-
aldehydes with a substituent at the a-carbon provided the
alkynol products with comparable ee values to a,b-unsatu-
rated aldehydes (Table 3, entries 12 and 13), however the
straight chain of the aliphatic aldehyde only afforded the
product with 76% ee (Table 3, entry 11). These results rep-
resent major progress in the amino-alcohol–Zn catalyzed ad-
dition reactions of trimethylsilylacetylene to aliphatic and
a,b-unsaturated aldehydes. The new addition reactions
would provide a generally applicable procedure for the syn-
thesis of the alkyl substituted 3-silylpropargylic alcohols for
further desilylated derivatives, which are the key units or
building blocks in natural product synthesis.
Chiral alkynols are valuable synthetic building blocks. For
example, the alkynol product 5 (prepared from the addition
reaction of trimethylsilylacetylene to (E)-octadec-2-enal
(4)), was easily desilylated to furnish a type of marine alky-
nol 6, which has been separated from the sponge Cribrocha-
lina vasculum and shows in vitro immunosuppressive and
antitumor activities (Scheme 2).[14] The ee value of 6 could
turated and aliphatic aldehydes.[a]
Entry
Aldehyde
Yield
[%][b]
ee
[%][c]
1[d]
2
40
68
63
83
3
82
71
70
92
94
94
4[e]
5[e]
6
7
88
82
94
85
8
80
85
9
62
74
83
84
10[e]
11
12
62
78
76
82
13
80
87
Scheme 2. Synthesis of marine alkynol product 6.
[a] Three equivalents of trimethylsilylacetylene were used. [b] Yield of
isolated product. [c] Determined by HPLC. [d] 10 mol% of ligand was
used. [e] Absolute configuration has not been assigned.
be increased to 97% by simple recrystallization. Compared
with the reported multistep synthetic strategy,[15] the synthe-
sis of 6 with alkynylation as a key step is quite brief. The
synthetic utility of our reaction was further exemplified by
the concise synthesis of falcarindiol,[16] which is a representa-
tive alkynol natural product and exhibited antimicrobial, an-
tibacterial, antifungal, and antiproliferative activities.[3b,17]
Previously, cumbersome procedures were required to obtain
(3S, 8S)-falcarindiol, with asymmetric ynone reduction as
the key step.[18] With our current approach, (3S,8S)-falcarin-
diol can be easily accessed in very short route (Scheme 3).
In conclusion, we have developed an amino-alcohol–Zn
catalyzed highly enantioselective addition of trimethylsilyl-
and aliphatic aldehydes with trimethylsilylacetylene was in-
vestigated in the presence of 20 mol% of amino alcohol 1
(Table 3). The substituent at the a-carbon of the a,b-unsatu-
rated aldehyde appeared to have a great influence on the
enantioselectivity of the reaction. a-Alkyl substituted a,b-
unsaturated aldehydes underwent the addition reaction in
92–94% ee with good yields (Table 3, entries 3–6). In con-
trast, the reactions with acrylaldehyde (Table 3, entry 2), b-
alkyl (entries 7–9), and b,b’-dialkyl (entry 10) substituted al-
dehydes were somewhat sluggish to react, leading to the cor-
responding products with 80–
85% ee. The nature and
number of the substituent at
the b-carbon of the a,b-unsatu-
rated aldehyde does not have
an impact on the reaction
course (Table 3, entries 7–10).
In addition, the E and Z struc-
ture of the alkenes has no
effect on enantioselectivity
(Table 3, entries 7 and 8). The
addition reactions of aliphatic Scheme 3. Synthesis of (3S,8S)-falcarindiol. NBS=N-bromosuccinimide.
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Enantioselective Addition of Trimethylsilylacetylene to Aldehydes
COMMUNICATION
6131–6141; k) H. Sugiyama, F. Yokokawa, T. Shioiri, Org. Lett.
2000, 2, 2149–2152; l) P. A. Roethle, D. Trauner, Org. Lett. 2006, 8,
345–347.
acetylene to aromatic, a,b-unsaturated and aliphatic alde-
hydes. The alkynylation is broad in scope with respect to al-
dehyde substrates. Notably, the catalytic procedure elimi-
nates the need for commonly used additives, such as small
amounts of amine. The synthetic utility of this method was
demonstrated in the concise syntheses of two biologically
active alkynol natural products. The salient features of this
protocol, such as its operational simplicity, mild reaction
conditions, and the cheap and easy preparation of amino al-
cohol ligands, suggest that it has good potential for extensive
application of these reactions in the synthesis of chiral alky-
nols.
[3] a) M. Stavri, K. T. Mathew, T. Gibson, R. T. Williamson, S. Gibbons,
J. Nat. Prod. 2004, 67, 892–894; b) M. Kobaisy, Z. Abramowski, L.
Lermer, G. Saxena, R. E. W. Hancock, G. H. N. Towers, D. Doxsee,
R. W. Stokes, J. Nat. Prod. 1997, 60, 1210–1213.
[4] For some representative examples, see: a) E. J. Corey, K. A. Cim-
prich, J. Am. Chem. Soc. 1994, 116, 3151–3152; b) D. E. Frantz, R.
Faessler, E. M. Carreira, J. Am. Chem. Soc. 2000, 122, 1806–1807;
c) D. Moore, L. Pu, Org. Lett. 2002, 4, 1855–1857; d) X. Li, G. Lu,
W. H. Kwok, A. S. C. Chan, J. Am. Chem. Soc. 2002, 124, 12636–
12637; e) Z. Xu, C. Chen, J. Xu, M. Miao, W. Yan, R. Wang, Org.
Lett. 2004, 6, 1193–1195; f) G. Gao, R.-G. Xie, L. Pu, Proc. Natl.
Acad. Sci. USA 2004, 101, 5417–5420; g) R. Takita, K. Yakura, T.
Ohshima, M. Shibasaki, J. Am. Chem. Soc. 2005, 127, 13760–13761;
h) M. Ni, R. Wang, Z.-j. Han, B. Mao, C.-S. Da, L. Liu, C. Chen,
Adv. Synth. Catal. 2005, 347, 1659–1665; i) B. M. Trost, A. H. Weiss,
A. Jacobi von Wangelin, J. Am. Chem. Soc. 2006, 128, 8–9; j) C.
Wolf, S. Liu, J. Am. Chem. Soc. 2006, 128, 10996–10997; k) B. M.
Trost, A. H. Weiss, Org. Lett. 2006, 8, 4461–4464; l) G. Gao, Q.
Wang, X.-Q. Yu, R.-G. Xie, L. Pu, Angew. Chem. 2006, 118, 128–
131; Angew. Chem. Int. Ed. 2006, 45, 122–125; m) L. Lin, X. Jiang,
W. Liu, L. Qiu, Z. Xu, J. Xu, A. S. C. Chan, R. Wang, Org. Lett.
2007, 9, 2329–2332; n) M. Turlington, A. M. DeBerardinis, L. Pu,
Org. Lett. 2009, 11, 2441–2444; o) J.-C. Zhong, S.-C. Hou, Q.-H.
Bian, M.-M. Yin, R.-S. Na, B. Zheng, Z.-Y. Li, S.-Z. Liu, M. Wang,
Chem. Eur. J. 2009, 15, 3069–3071; p) B. M. Trost, V. S. Chan, D. Ya-
mamoto, J. Am. Chem. Soc. 2010, 132, 5186–5192; q) J.-i. Ito, R.
Asai, H. Nishiyama, Org. Lett. 2010, 12, 3860–3862.
Experimental Section
In a flame-dried Schlenk tube under nitrogen atmosphere, trimethylsilyl-
acetylene (0.42 mL, 3.0 mmol, 3 equiv) and Me2Zn solution (2.5 mL, 1.2m
in toluene, 3 mmol, 3 equiv) were dissolved in dry toluene (3.5 mL), and
the solution was stirred for 90 min at 308C, then transferred by the sy-
ringe to another flame-dried Schlenk tube containing the amino alcohol
ligand (0.1 mmol, 0.1 equiv, or 0.2 mmol, 0.2 equiv). After the resulting
solution was stirred for 30 min at 308C, the aldehyde (1 mmol) was
added and the reaction mixture was stirred at the same temperature for
24 h. The reaction was quenched with saturated NH4Cl aqueous solution
(5 mL) at 08C and extracted with diethyl ether (3ꢂ10 mL). The organic
layer was dried over Na2SO4, filtered, and concentrated under vacuum.
The residue was purified by flash chromatography on silica gel (SiO2, par-
ticle size 32–63 mm; eluent: hexane/ether (9:1)) to afford the correspond-
ing pure propargylic alcohols. The enantiomeric excess was determined
by HPLC (Chiralcel OD or AD, 10% of iPrOH in hexane if not stated
otherwise). For additional details, see the Supporting Information.
[5] a) K. Sonogashira in Comprehensive Organic Synthesis, Vol. 3 (Eds.:
B. M. Trost, I. Fleming), Pergamon, New York, 1991, pp. 521–549;
b) J. A. Marshall, G. M. Schaaf, J. Org. Chem. 2001, 66, 7825–7831;
c) S. A. Burova, F. E. McDonald, J. Am. Chem. Soc. 2002, 124,
8188–8189; d) S. A. Burova, F. E. McDonald, J. Am. Chem. Soc.
2004, 126, 2495–2500; e) Y. D. Zhang, Y. F. Tang, T. P. Luo, J. Shen,
J. H. Chen, Z. Yang, Org. Lett. 2006, 8, 107–110.
[6] a) Z. Xu, N. Wu, Z. Ding, T. Wang, J. Mao, Y. Zhang, Tetrahedron
Lett. 2009, 50, 926–929; b) S. Subirats, C. Jimeno, M. A. Pericas, Tet-
rahedron: Asymmetry 2009, 20, 1413–1418.
Acknowledgements
[7] S. Dahmen, Org. Lett. 2004, 6, 2113–2116.
Support of this study was from China NSFC, the startup research funding
from China Agricultural University, National 12th Five-Year Plan Scien-
tific and Technological Issues and Nutriechem Company is gratefully ac-
knowledged.
[8] G. Blay, L. Cardona, I. Fernandez, A. Marco-Aleixandre, M. C.
Munoz, J. R. Pedro, Org. Biomol. Chem. 2009, 7, 4301–4308.
[9] a) F. Yang, P. Xi, L. Yang, J. Lan, R. Xie, J. You, J. Org. Chem. 2007,
72, 5457–5460; b) Y. Yue, M. Turlington, X.-Q. Yu, L. Pu, J. Org.
Chem. 2009, 74, 8681–8689.
[10] Y. Asano, K. Hara, H. Ito, M. Sawamura, Org.Lett. 2007, 9, 3901–
3904.
[11] L. Qiu, Q. Wang, L. Lin, X. Liu, X. Jiang, Q. Zhao, G. Hu, R.
Wang, Chirality 2009, 21, 316–323.
Keywords: addition reaction
alcohols · asymmetric catalysis · zinc
·
alkynylation
·
amino
[12] a) N. K. Anand, E. M. Carreira, J. Am. Chem. Soc. 2001, 123, 9687–
9688; b) D. Boyall, D. E. Frantz, E. M. Carreira, Org. Lett. 2002, 4,
2605–2606; c) D. Boyall, F. Lopez, H. Sasaki, D. E. Frantz, E. M.
Carreira, Org. Lett. 2000, 2, 4233–4236; d) E. El-Sayed, N. K.
Anand, E. M. Carreira, Org. Lett. 2001, 3, 3017–3020.
[1] a) B. M. Trost, A. H. Weiss, Adv. Synth. Catal. 2009, 351, 963–983;
b) O. Riant, J. Hannedouche, Org. Biomol. Chem. 2007, 5, 873–888;
c) P. G. Cozzi, R. Hilgraf, N. Zimmermann, Eur. J. Org. Chem. 2004,
4095–4105.
[13] a) B. Zheng, S. Hou, Z. Li, H. Guo, J. Zhong, M. Wang, Tetrahe-
dron: Asymmetry 2009, 20, 2125–2129; b) J. Zhong, H. Guo, M.
Wang, M. Yin, M. Wang, Tetrahedron: Asymmetry 2007, 18, 734–
741; c) J. Zhong, M. Wang, H. Guo, M. Yin, Q. Bian, M. Wang, Syn-
lett 2006, 1667–1670. For the reports from other research groups,
see: d) P. Aviron-Violet, Y. Colleuille, J. Varagnat, J. Mol. Catal.
1979, 5, 41–50; e) Y. Okada, T. Minami, T. Yamamoto, J. Ichikawa,
Chem. Lett. 1992, 547–550; f) G. A. Molander, J. P. Burke, P. J. Car-
roll, J. Org. Chem. 2004, 69, 8062–8069.
[14] S. P. Gunasekera, G. T. Faircloth, J. Org. Chem. 1990, 55, 6223–6225.
[15] a) J. Garcia, M. Lopez, J. Romeu, Tetrahedron: Asymmetry 1999, 10,
2617–2626; b) W. Lu, G. Zheng, J. Cai, Tetrahedron 1999, 55, 4649–
4654; c) J. Chun, H.-S. Byun, R. Bittman, Tetrahedron Lett. 2002, 43,
[2] For some reviews, see: a) Modern Acetylene Chemistry (Eds.: P. J.
Stang, F. Diederich), Wiley-VCH, Weinheim, 1995; b) K. K. Chau-
han, C. G. Frost, J. Chem. Soc. Perkin Trans. 1 2000, 3015–3019. For
selected examples, see: c) A. M. Caporusso, L. Lardicci, J. Chem.
Soc. Perkin Trans. 1 1983, 949–953; d) J. A. Marshall, X. J. Wang, J.
Org. Chem. 1992, 57, 1242–1252; e) G. Zhu, X. Lu, J. Org. Chem.
1995, 60, 1087–1089; f) B. M. Trost, T. J. J. Mueller, J. Martinez, J.
Am. Chem. Soc. 1995, 117, 1888–1899; g) A. G. Myers, B. Zheng, J.
Am. Chem. Soc. 1996, 118, 4492–4493; h) M. E. Fox, C. Li, J. P. Mar-
ino, Jr., L. E. Overman, J. Am. Chem. Soc. 1999, 121, 5467–5480;
i) L. Tan, C.-Y. Chen, R. D. Tillyer, E. J. J. Grabowski, P. J. Reider,
Angew. Chem. 1999, 111, 724–727; Angew. Chem. Int. Ed. 1999, 38,
711–713; j) B. M. Trost, M. J. Krische, J. Am. Chem. Soc. 1999, 121,
Chem. Eur. J. 2011, 17, 5782 – 5786
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J.-C. Zhong, H.-C. Guo et al.
8043–8045; d) B. W. Gung, H. D. Dickson, S. Seggerson, K. Bluhm,
Synth. Commun. 2002, 32, 2733–2740.
mund, J. Mader, R. Greil, E. P. Ellmerer, H. Stuppner, J. Agric.
Food Chem. 2005, 53, 2518–2523.
[18] a) G. Zheng, W. Lu, J. Cai, J. Nat. Prod. 1999, 62, 626–628; b) G. Sa-
bitha, V. Bhaskar, C. S. Reddy, J. S. Yadav, Synthesis 2008, 115–121;
c) L. Schmiech, C. Alayrac, B. Witulski, T. Hofmann, J. Agric. Food
Chem. 2009, 57, 11030–11040; d) S. Tamura, T. Ohno, Y. Hattori, N.
Murakami, Tetrahedron Lett. 2010, 51, 1523–1525.
[16] a) F. Bohlmann, U. Niedballa, K. M. Rode, Chem. Ber. 1966, 99,
3552–3558; b) S. Ratnayake Anokha, T. Hemscheidt, Org. Lett.
2002, 4, 4667–4669.
[17] a) M. S. Kemp, Phytochemistry 1978, 17, 1002–1002; b) K. Furumi,
T. Fujioka, H. Fujii, H. Okabe, Y. Nakano, H. Matsunaga, M.
Katano, M. Mori, K. Mihashi, Bioorg. Med. Chem. Lett. 1998, 8, 93–
96; c) C. Zidorn, K. Joehrer, M. Ganzera, B. Schubert, E. M. Sig-
Received: February 17, 2011
Published online: April 8, 2011
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