Novel carbon-carbon bond formation from propargylic alcohols and olefin toward five-membered heterocyclic rings catalyzed by AgSbF6

Article abstract of DOI:10.1021/ol901270b

A mild and direct process for C-C bond formation from propargylic alcohols and olefin has been developed in the presence of a silver catalyst. In this reaction, trace amounts of water were necessary and aliene alcohols 2 and 1,3-dienes 3 were obtained sel

Full text of DOI:10.1021/ol901270b

ORGANIC
LETTERS
2009
Vol. 11, No. 15
3206-3209
Novel Carbon-Carbon Bond Formation
from Propargylic Alcohols and Olefin
toward Five-Membered Heterocyclic
Rings Catalyzed by AgSbF6
Ke-Gong Ji, Xing-Zhong Shu, Shu-Chun Zhao, Hai-Tao Zhu, Yan-Ning Niu,
Xue-Yuan Liu, and Yong-Min Liang*
State Key Laboratory of Applied Organic Chemistry, Lanzhou UniVersity, and State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese,
Academy of Science, Lanzhou 730000, P. R. China
liangym@lzu.edu.cn
Received May 18, 2009
ABSTRACT
A mild and direct process for C-C bond formation from propargylic alcohols and olefin has been developed in the presence of a silver
catalyst. In this reaction, trace amounts of water were necessary and allene alcohols 2 and 1,3-dienes 3 were obtained selectively.
The development of novel methods for the annulation of five-
membered heterocyclic rings is very important in the field of
Scheme 1
synthetic organic chemistry because such heterocyclic com-
pounds are useful synthetic intermediates as well as important
structural units found in natural and artificial products.1 For
example, kainic acid and allokainic acid, isolated from marine
alga, attract the interest of synthetic chemists.2
Recently, transition-metal-catalyzed cyclization reactions
of carbon-hetero formation (via path a) and carbon-carbon
formation (via path b) represent an effective and straight-
as good as other late transition metals. On the other hand,
silver(I) complexes are generally used as stoichiometric
oxidants for the oxidation of various organic or inorganic
substrates. Many reports used silver(I) complexes as catalysts
forward methodology for the synthesis of this heterocyclic
compounds (Scheme 1).3
Silver “catalysts”, as a transition metal catalyst, are
commonly considered to have low efficiency and not to be
(3) For recent reviews, see: (a) Patil, N. T.; Yamamoto, Y. Chem. ReV.
2008, 108, 3395. (b) Nakamura, I.; Yamamoto, Y. Chem. ReV. 2004, 104,
(1) (a) Porter, A. E. A. ComprehensiVe Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vol.
3, pp 157-197. (b) Sainsburg, M. ComprehensiVe Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vol.
3, pp 995-1038. (c) Sharp, J. T. ComprehensiVe Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vol.
7, pp 593-651.
2127. (c) McReynolds, M. D.; Dougherty, J. M.; Hanson, P. R. Chem. ReV.
2004, 104, 2239. (d) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. ReV.
2004, 104, 3079. (e) Deiters, A.; Martin, S. F. Chem. ReV. 2004, 104, 2199.
(f) Zeni, G.; Larock, R. C. Chem. ReV. 2004, 104, 2285. (g) Yet, L. Chem.
ReV. 2000, 100, 2963. (h) Tsuji, J. Transition Metal Reagents and Catalysts;
John Wiley & Sons Ltd.: New York, 2000. (i) Transition Metals for Organic
Synthesis; Beller, M., Bolm, C., Eds.; Wiley-VCH Verlag GmbH: Wein-
heim, 1998. (j) Transition Metal Catalyzed Reactions; Murahashi, S., Davies,
S. G., Eds.; Blackwell Science: Oxford, 1999.
(2) Takano, S.; Sugihara, T.; Satoh, S.; Ogasawara, K. J. Am. Chem.
Soc. 1988, 110, 6467, and references therein.
10.1021/ol901270b CCC: $40.75
Published on Web 07/02/2009
 2009 American Chemical Society

in oxidation or group-transfer reactions,4 although recent
studies have shown that silver species exhibited interesting
catalytic activities functioning for carbon-hetero formation.5,6
However, examples of the carbocyclization catalyzed by
silver are limited.7 In the context of our ongoing efforts to
develop tandem reactions, we anticipated that a new domino
process initiated by silver induced C-C bond formation
followed by subsequent trace amounts of water attack
(Scheme 2) might be achieved. Herein, we reported a novel
Table 2. AgSbF6-Catalyzed Synthesis of Allene Alcohols 2
from Propargylic Alcohols 1a
Scheme 2
carbon-carbon bond formation from propargylic alcohols
and olefin toward five-membered heterocyclic rings in the
presence of AgSbF6. In this reaction, trace amounts of water
were necessary and olefin as the intramolecular nucleophilic
with propargylic alcohols were selectively transformed into
allene alcohols and 1,3-dienes.
Initially, we started by using 0.3 mmol of N-(4-hydroxy-
4-phenylbut-2-ynyl)-N-(3-methylbut-2-enyl)-toluenesulfona-
Table 1. Transition-Metal Catalysts for the Transformation of
1a to 2a
a Conditions: 0.3 mmol of 1 with 10 mol % of catalyst in CH2Cl2 (2.0
mL) at 15 °C. b Isolated yield.
temp time yield
(%)a
mide 1a and 5 mol % of AgSbF6 in wet CH2Cl2 at room
temperature; to our delight, the desired product 2-(4-(2-
phenylvinylidene)-1-tosylpyrrolidin-3-yl)propan-2-ol 2a was
formed in 80% yield after 20 h. On increasing the amount
of catalyst to 10 mol %, a 88% yield of 2a was obtained
after 15 h, when the silver salt was added to 15 mol %, but
no higher yield was obtained (Table 1, entries 1-3). Then
we decrease temperature to 15 °C, an excellent yield of 2a
was obtained with 10 mol % AgSbF6 (up to 92%) (Table 1,
entry 4). The reaction was also tested in dry CH2Cl2 at 15
°C; only trace amounts of 2a was observed (Table 1, entry
6). Other silver catalysts, such as AgOTf, AgBF4, AgNTf2,
AgOOCCF3 gave no better results (Table 1, entries 7-10).
AlCl3 and FeCl3, including protic acids such as TsOH, TFA
and TfOH have also been applied to the reaction, no superior
results were obtained (Table 1, entries 11-15). Other
solvents were also tested in the reaction, only DCE gave
good yield. Thus, the use of AgSbF6 (10 mol %) in wet
CH2Cl2 at 15 °C was found to be the most efficient and used
as the standard conditions.
entry catalyst (mol %)
solvent
CH2Cl2
(°C)
(h)
1
2
3
4
5
6
7
8
AgSbF6 (5)
AgSbF6 (10)
AgSbF6 (15)
AgSbF6 (10)
AgSbF6 (10)
AgSbF6 (10)
AgOTf (10)
AgBF4(10)
rt
rt
rt
15
0
20
15
12
20
24
24
24
24
24
24
24
24
24
24
24
18
24
24
24
24
80
88
87
92
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
dry CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
80
c
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
0
0
73
0
9
AgNTf2 (10)
10b
11
12
13
14
15b
16
17
18
19
20
AgOOCCF3 (10) CH2Cl2
AlCl3 (10)
FeCl3 (10)
TsOH (10)
F3CCOOH (10)
TfOH(10)
AgSbF6 (10)
AgSbF6 (10)
AgSbF6 (10)
AgSbF6 (10)
AgSbF6 (10)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
ClCH2CH2Cl
THF
CH3OH
toluene
CH3NO2
0
c
13
c
d
91
0
0
0
0
a Isolated yield. b Decomposed. c Trace. d For details, see Supporting
With the optimized conditions in hand, various representa-
tive propargylic alcohols 1a-l were then submitted to the
Information.
Org. Lett., Vol. 11, No. 15, 2009
3207

Table 3. AgSbF6-Catalyzed Synthesis of 1,3-dienes 3 from Propargylic Alcohols 1a
a Conditions: 0.3 mmol of 1 with 10 mol % of catalyst in CH2Cl2 (2.0 mL) at 15 °C. b Isolated yield. c The reaction was carried out at 40 °C.
above conditions, as depicted in Table 2. Thus, a tandem
carbon-carbon and carbon-oxygen bond formation of
propargylic alcohols 1a-f and 1h-k proceeded smoothly to
provide corresponding products 2a-f and 2h-k in moderate
to excellent yields. The reaction works well with aromatic
R1 groups. Electron-withdrawing aryl groups showed better
results than those with an electron-rich group in this tandem
reaction (1b vs 1c). Substrate 1d with a heteroaromatic R1
group can also afford the desired product 2d in 73% yield,
while a substrate like 1g with an aliphatic R1 group gave no
reaction. Other substrates like 1h-k can also afford corre-
sponding furan derivatives 2h-k in moderate yield. Interest-
ingly, substrate like 1l with steric effects gave no reaction.
Furthermore, to expand the scope of this reaction, we
also investigated a range of propargylic alcohols; it was
found that under the silver catalyst some substrates 1
transferred into 1,3-dienes 3 directly, without giving the
products 2 as depicted in Table 3. Various representative
propargylic alcohols 1m-u transferred into corresponding
products 3m-u in moderate to excellent yields (up to
97%) (Figure 1).
(4) For selected papers, see: (a) Li, Z.; Capretto, D. A.; Rahaman, R.;
He, C. Angew. Chem., Int. Ed. 2007, 46, 5184. (b) Cui, Y.; He, C. Angew.
Chem., Int. Ed. 2004, 43, 4210. (c) Clark, T. B.; Woerpel, K. A. J. Am.
Chem. Soc. 2004, 126, 9522. (d) Cui, Y.; He, C. J. Am. Chem. Soc. 2003,
125, 16202. (e) Josephsohn, N. S.; Snapper, M. L.; Hoveyda, A. H. J. Am.
Chem. Soc. 2003, 125, 4018. (f) Momiyama, N.; Yamamoto, H. J. Am.
Chem. Soc. 2003, 125, 6038. (g) Dias, H. V. R.; Browning, R. G.; Polach,
S. A.; Diyabalanage, H. V. K.; Lovely, C. J. J. Am. Chem. Soc. 2003, 125,
9270.
(5) For selected recent examples of Ag-catalyzed reviews, see: (a)
Yamamoto, Y. Chem. ReV. 2008, 108, 3199. (b) Weibel, J.-M.; Blanc, A.;
´
Pale, P. Chem. ReV. 2008, 108, 3149. (c) Alvarez-Corral, M.; Mun˜oz-
Dorado, M.; Rodr´ıguez-Garc´ıa, I. Chem. ReV. 2008, 108, 3174. (d) Li, Z.;
He, C. Eur. J. Org. Chem. 2006, 4313.
(6) For selected examples of Ag-catalyzed reactions, see: (a) Umeda,
R.; Studer, A. Org. Lett. 2008, 10, 993. (b) Mandai, H.; Mandai, K.; Snapper,
M. L.; Hoveyda, A. H. J. Am. Chem. Soc. 2008, 130, 17961. (c) Yong,
S. W.; Eom, J. I. J. Org. Chem. 2006, 71, 6705. (d) Yang, C.-G.; Reich,
N. W.; Shi, Z.; He, C. Org. Lett. 2005, 7, 4553. (e) Yao, X.; Li, C.-J. Org.
Lett. 2005, 7, 4395. (f) Patil, N. T.; Pahadi, N. K.; Yamamoto, Y. J. Org.
Chem. 2005, 70, 10096. (g) Wei, C.; Li, Z.; Li, C.-J. Org. Lett. 2003, 5,
4473.
Figure 1.
X-ray structure of 3q.8
To uncover the mechanism for the reaction, we started
out by using propargylic alcohol 1m under the standard
conditions, and the desired product 2m was isolated in 30%
(7) (a) Yao, X.; Li, C.-J. J. Org. Chem. 2005, 70, 5752. (b) Harrison,
T. J.; Dake, G. R. Org. Lett. 2004, 6, 5023. (c) Sweis, R. F.; Schramm,
M. P.; Kozmin, S. A. J. Am. Chem. Soc. 2004, 126, 7442.
3208
Org. Lett., Vol. 11, No. 15, 2009

yield after 2 h,9 and only a trace amount of 3m was observed.
When the reaction was carried out for 10 h under the above
conditions, and only a trace amount of 2m was observed;
also, a 50% yield of 3m was isolated (Scheme 3).
Scheme 4. Proposed Mechanism
Scheme 3
On the basis of the above observations, we propose the
following plausible mechanisms for this cascade transforma-
tion (Scheme 4). (i) Coordination of the alkynyl moiety and
hydroxy of A to AgSbF6 gives the complex B. (ii) The
subsequent domino trace amounts of water as the nucleo-
philic attack the olefin and occurs carbocyclization affords
intermediate allene alcohol cation C. (iii) Intermediate C
releases the hydrogen cation to afford the allene alcohol D
and regenerates the catalyst AgSbF6. (iv) Coordination of
the allene moiety of D to Ag catalyst gives the complex E.
(v) Some of allene alcohols occur domino carbon-carbon
bond cleavage and afford the intermediate F. (IV) Protonation
of F yields 1,3-dienes G and regenerates the catalyst Ag. In
this reaction, trace amounts of water played an important
role.
member heterocyclic compounds allene alcohols 2 and 1,3-
dienes 3 containing various functionalities. A more detailed
investigation on the mechanism, as well as the scope of this
cascade, is ongoing in our laboratory.
Acknowledgment. We thank the NSF (NSF-20621091,
NSF-20732002) for financial support.
Supporting Information Available: Experimental pro-
cedures and full spectroscopic data for all new compounds.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OL901270B
In summary, a mild and direct process for C-C bond
formation from propargylic alcohols and olefin has been
developed in the presence of a silver catalyst. In this reaction,
trace amounts of water were necessary and propargylic
alcohols with olefin were selectively transformed into five-
(8) The molecular structure of the corresponding product 1q was
determined by means of X-ray crystallographic studies; for details, see the
Supporting Information.
(9) The product 2m may be not stable, and only 30% yield was isolated
by flash column chromatography.
Org. Lett., Vol. 11, No. 15, 2009
3209