Gold-catalyzed sequential activation of propargylic carboxylates: A facile route to benzoannulenes

Article abstract of DOI:10.1002/chem.201204091

A cascade reaction of 1-(2-(3-acetoxyprop-1-ynyl)phenyl)prop-2-ynyl acetate and its derivatives is catalyzed by gold to give the corresponding benzo[7]annulenes (see scheme) in excellent yields. A double activation of the gold catalyst toward two different propargylic carboxylates was proposed. Benzoannulenes were hydrolyzed to 8-hydroxybenzo[7]annulene-5-ones. Copyright

Full text of DOI:10.1002/chem.201204091

DOI: 10.1002/chem.201204091
Gold-Catalyzed Sequential Activation of Propargylic Carboxylates: A Facile
Route to Benzoannulenes
Chang Ho Oh,* Ji Hee Kim, Bu Keun Oh, Jong Ryul Park, and Ji Ho Lee[a]
Gold catalysis has emerged as an extraordinary method to
create molecular complexity over the last decade because of
the unique property of gold(I) and goldACTHNUTRGNE(NUG III) complexes to
gration.[11] Two different but mechanistically related inter-
mediates characterize these competitive processes depend-
ing on the type of substrates: 1,2-migration to the gold car-
benes proceeds via the alkenylgold species, whereas 1,3-mi-
gration forms allenoates by gold-assisted [3,3]-sigmatropic
rearrangement (Scheme 1).[12] First, terminal propargyl car-
activate carbon–carbon p-systems.[1] Electrophilic activation
of carbon–carbon multiple bonds toward a variety of nucleo-
philes relies on the interaction between gold catalysts
(sometimes combined with silver salts) and p-bonds of al-
kenes, alkynes, or allenes.[2] In this regard, gold carbenes
and gold-stabilized carbocations have been invoked as likely
reaction intermediates.[3] A broad array of gold-catalyzed
cyclizations and cycloisomerizations have been disclosed
that offer access to a plethora of new complex cyclic motifs
in a highly efficient manner.[4] With significant diversity in
the types of existing gold catalyzed reactions, gold–carbon
s-bond-containing intermediates are captured most fre-
quently by a proton,[5] and much less frequently with alter-
native electrophiles, such as carbocations and sulfonyl, sili-
con, and halogen electrophiles.[6] Recent research has indi-
cated that transmetalation of gold intermediates formed in
situ could extend the scope of gold-catalyzed reactions to,
Scheme 1. Two possible pathways for activation of alkynes with an
AHCTUNGTREGaNNUN cyloxy group by gold.
boxylates would form a five-membered ring intermediate A
by 5-exo-dig, that would form gold–carbene complex B
(path a). Note that gold–carbene species would undergo cy-
clopropanation[13] or cyclopentanation[14] to form a variety of
cyclic compounds. Internal propargylic carboxylates (path
b), however, would undergo oxyaddition to a gold-activated
ꢀ
for example, C C cross-coupling reactions. Recently, Ga-
rayalde and Nevado have disclosed a less explored area in
gold catalysis that would involve the generation of gold-con-
taining 1,n dipoles and their use as reaction partners in cy-
cloaddition and cyclization reactions.[7] Both inter- and intra-
molecular annulation reactions have been recognized as
powerful methods to access cyclic scaffolds in highly regio-
and stereocontrolled fashions.[8] We have long been interest-
ed in developing gold-catalyzed cycloisomerization of di-
triple bond to give C, which further proceeds to give al
oate 2.
Allenoates such as 2 could be isolated and/or utilized in
situ for cycloaddition reactions with the pendant triple bond
ACHTUNGTRENNUNGlen-
AHCTUNGTRENNUNG
A
to give
a
variety of cyclized products of type
3
pounds.[9] This type of structure is found in a variety of natu-
ral products, including barbatusol, pisiferin, faveline, and
(Scheme 2).[15] These cycloadditions would involve a propar-
ACHTUNGTRENNUNGxochitlolone. Application of this strategy to the synthesis of
the ring B and C of a chrysenone derivative in one prepara-
tive step was published by Dyker and co-workers in 2006.[10]
Gold complexes efficiently activate propargylic carboxy-
lates towards 1,2-acyloxy migration and/or 1,3-acyloxy mi-
[a] Prof. C. H. Oh, J. H. Kim, B. K. Oh, J. R. Park, J. H. Lee
Department of Chemistry, Hanyang University
Sungdong-Gu, Seoul 133-791 (Korea)
Fax : (+82)22299-0762
E-mail: changho@hanyang.ac.kr
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201204091.
Scheme 2. Intramolecular cycloadditions of allenoates formed in situ.
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COMMUNICATION
Table 1. Cyclizations of 5a-b under various catalytic conditions.
gylic carboxylate and a triple bond in the presence of a gold
catalyst to give the corresponding dienoates, which would be
hydrolyzed into corresponding enones upon treatment with
an equivalent of water. Cycloalkene- or benzene-anchored
substrates (1a) provide the products of type 3a. If both a
propargylic carboxylate and a triple bond are located in a
substrate bearing an aliphatic linker such as 1b and 1c, the
corresponding allenoates 2b and 2c would be formed as in-
termediates, and then cyclized with the triple bond in differ-
ent pathways to 3b and 3c, respectively. When a substrate
possess two propargylic carboxylates with one terminal and
one internal triple bond, it was thought to be highly valuable
to examine its chemistry toward alkynophilic metals, such as
in gold, silver, and platinum compounds. Two different prop-
argyl carboxylates might react differently towards such
metal complexes and thus exhibit a domino sequence to
give a very interesting result. To test our hypothesis, we pre-
pared a model substrate 5a in a three-step sequence starting
from 2-bromobenzaldehyde (Scheme 3). Sonogashira cou-
Entry Catalyst [3 mol%] Solvent T [8C] t [h] Yield [%][a]
6a
6aa
1
2
3
4
5
6
7
8
NaAuCl4·H2O
AuCl3
AuCl·H2O
AuCl
EDC[b]
EDC
EDC
EDC
EDC
EDC
EDC
toluene
EDC
EDC
EDC
EDC
EDC
80
80
80
80
100
80
80
110
80
60
60
2
2
2
2
95 (92[c]
67
80
)
–
–
–
–
–
–
–
20
88
75
45
70
–
67
A
N
12 10
2
6
[Au(CO)Cl]
PtCl2
PtCl2
50
20
12 74
9
AgOTf
4
2
2
2
2
–
–
–
10
11
12
13
Cu
Sc(OTf)3
In(OTf)3
NaAuCl4·H2O
A
T
A
60
80
–
88[d]
[a] Determined by 1H NMR spectroscopy of the crude products. [b] 1,2-
dichloroethane. [c] Yield of isolated product. [d] %Yield for 6b.
6-methylene-6H-benzo[7]annulene-5,8-diyl diacetate (6a),
as shown by 1H and 13C NMR, FTIR spectroscopy, and
HRMS. Substrate 5b, a propanoate derivative, was also con-
verted into the 6b in 88% yield when treating 3 mol% of
NaAuCl4·H2O in EDC (entry 13). Further, the products 6a
and 6b were hydrolyzed using aqueous NaOH solution at
room temperature to give the diol, which was tautomer-
ized into 8-hydroxy-6-methyl-5H-benzo[7]annulene-5-one
(7a).[18]
Compound 7a would be a valuable molecular motif that
could be functionalized and transformed into useful mole-
cules. The present novel cascade sequence leading to 7a
from 5a would be explained by the mechanism proposed in
Scheme 4.[19]
Scheme 3. Preparation of substrate 5a.
pling of 4 with propargyl acetate to 4a, its ethynylation to
4aa, and then acetylation provided substrate 5a in a multi-
gram scale.[16]
With substrate 5a in hand, it was screened with alkyno-
philic metal complexes and a few Lewis acids to scrutinize
its chemical behavior (Table 1). Gratifyingly, we could vali-
date our design, which afforded a single interesting product
by analysis of the NMR spectra of the reaction mixture
after drying solvent.
Gold(I) and goldACHTUNGTRENNUNG(III) complexes catalyzed the conversion
of 5a into 6a as the sole product. Among gold compounds,
NaAuCl4·H2O was the best to give higher than 95% yields
(as shown by NMR spectroscopy; entry 1). AuCl3 itself cata-
lyzed this reaction at room temperature in 67% yield but
led to slow decomposition of the product 6a at more elevat-
ed temperatures (entry 2). Compared to wet AuCl, dry
AuCl gave an inferior result, implying that this reaction
might require a catalytic amount of water (entries 3 and 4).
Other gold(I) compounds possessing a ligand catalyzed this
reaction much less efficiently (entries 5,6). PtCl2, which is
known to have similar relativistic alkynophilicity, catalyzed
this reaction both at 808C in 1,2-dichloroethane (EDC) and
at 1108C in toluene but afforded 6a in 20% and 74%
yields, respectively (entries 7,8). In contrast to gold and
platinum compounds, silver triflate catalyzed the conversion
of 5a into 6aa, a naphthalene derivative (entry 9).[17] Other
Scheme 4. Proposed reaction mechanism for formation of 6a and 7a.
First, a gold cation was supposed to coordinate with two
triple bonds in the substrate 5a to form 5A and then to con-
vert the internal triple bond into the allene 5C via 1,3-car-
boxylate shift (5B). The gold-bound terminal triple bond
would undergo a 1,2-acyloxy shift to 5D, which forms the
Lewis acids, such as CuCAHTUNGTREN(UNNG OTf)2, ScACHTUNRTEGN(NGUN OTf)3, and InACHTNUGRTENN(UGN OTf)3, ex-
hibited similar catalytic activities toward 5a to 6aa (en-
tries 10–12). The structure of the product is a very unusual
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C. H. Oh et al.
seven-membered ring 5F by path a or b. Liberating a gold
cation from 5F leads to 6a. Hydrolysis of the products 6a
with aqueous NaOH in methanol occurred smoothly to give
8-hydroxy-6-methyl-5H-benzo[7]annulene-5-one (7a). With
this encouraging result, we prepared a series of substrates
5c–n and undertook cycloisomerization under the optimized
conditions to determine the scope and limitations of the
present method (Figure 1). Substrates 5c to 5e, which have
pletion, all of the substrates could be successfully converted
into the products 6g–k in excellent yields as a roughly 3:1
mixture of E/Z diastereomers. Note that a remote double
bond in 5h was intact toward our conditions. Each of sub-
strates 5l and 5m has tertiary propargylic acetate. To our
delight, both 5l and 5m also reacted at 808C to give 6l and
6m in 89 and 90% yields, respectively. The fourth type of
substrate was a phenyl-substituted propargyl acetate 5n.
This substrate worked in mod-
erate success to give 6n in 72%
yield as a E/Z mixture. Owing
to elongated conjugation along
benzo[7]annulenes
to
the
phenyl group, the product 6n
seemed to be unstable, and it
overconverted to give oligo-
AHCTUNGTRENNUNG
ynyl)phenyl)prop-2-ynyl acetate
(5a) and its derivatives 5b–5n
under gold catalysis would be
converted into 6-methylene-6H-
benzo[7]annulene-5,8-diyl diac-
etate (6a) and its derivatives
(6b–n) in good to excellent
yields.
To increase the usefulness in
synthetic and physical applica-
tion, we have hydrolyzed the
products 6c–n by using 1.0m
NaOH solution in methanol to
give
8-hydroxy-6-methyl-5H-
benzo[7]annulene-5-one deriva-
tives 7c–n without forming any
side products (Figure 2).
Benzo[7]annulene derivatives
7a–n might play important
roles in synthesis and materials.
Thus, we demonstrated the util-
ity of synthesized benzo[7]an-
nulenes by showing various
transformations of 7a to
a
AHCTUNGTRENNUNG
Figure 1. Cycloisomerization of 5c–n to 6c–n using 3 mol% NaAuCl4·H2O in EDC. Reaction temperature/
time (oC/h): 6c 80/4, 6d 80/8, 6e 80/12, 6 f 100/12, 6g 25/1, 6h 80/2, 6i 80/3, 6j 150/1, 6k 150/1, 6l 80/6, 6m 80/
2, 6n 25/2.
(Scheme 5). First it was reacted
with trifluoromethanesulfonic
anhydride to afford the triflate
8a. The triflate 8a was coupled
a methoxy or a fluorine substituent on the benzene ring,
were smoothly converted into the corresponding products
6c to 6e under our conditions with longer reaction times. A
naphthalene derivative 5 f required higher temperature
(1008C) to complete the desired transformation.
After the success of the structural variation onto the ben-
zene ring, we next examined substrates 5g–k by replacing
the propargylic hydrogen atoms by alkyl groups. Even with
different reaction temperatures and reaction times to com-
with 1-hexyne to 9a under Sonogashira conditions. Phenyl-
lithium treatment to 9a gave the alcohol 10a, which was de-
hydrated with the aid of BF3·OEt2 to give the hydrocarbon
11a.[20] In contrast to this sequence, we treated 7a with two
equivalents of phenyllithium to give 12a, dehydrated to 13a,
and triflated to 14a, which was converted into the com-
pound 11a by using the Sonogashira reaction.
Finally, we extended this procedure to cycloalkene-an-
AHCTUNGTRENNUNG
chored substrates 15a–c (Scheme 6).[21] 2-Bromo-1-cycloal-
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Chem. Eur. J. 2013, 19, 2592 – 2596

Activation of Propargylic Carboxylates
COMMUNICATION
2-ynyl acetate (1a) and its de-
rivatives (1b–n and 15a–c),
which can provide a highly effi-
cient access to 6-methylene-6H-
benzo[7]annulene-5,8-diyl diac-
etate (6a) and its derivatives
(6b–n and 16a–c) in good to
excellent yields. Two different
roles for the gold catalyst were
proposed. First, the reaction
most
through the formation of al
AHCTUNGTERGoNNUN ate intermediates 5B via 1,3-
probably
proceeds
ACHTUNGTRENNUNG
acyloxy transfer and subsequent
cyclization to 5E with 1,2-acti-
vated alkenylgold species 5C to
give the corresponding seven-
Figure 2. 8-Hydroxy-6-methyl-5H-benzo[7]annulen-5-one derivatives 7c–n. All of the products were isolated in
yields of over 95%.
membered rings 6a–n and 16a–c. The products 6a–n and
their hydrolysis products 7a–n might serve as important
structural motifs for complex multifunctional organic mate-
rials. Further studies to extend the practical application are
in progress.
Experimental Section
Sodium tetrachloroaurate hydrate (2.4 mg, 0.0063 mmol, 3.0 mol%) and
dried 1,2-dichloroethane (1.0 mL) were placed in a new 5 mL test tube
under an argon atmosphere. Substrate 5a (56.8 mg, 0.21 mmol), as a solu-
tion in 1,2-dichloroethane (1.0 mL), was cannulated to this solution over
one minute at 08C. The reaction tube was sealed and the mixture was
stirred at 808C for two hours. After the reaction was complete by TLC
analysis, the reaction mixture was cooled down to room temperature,
quenched with a drop of triethylamine, and concentrated under reduced
pressure. The concentrated residue was then rapidly purified by flash
silica gel chromatography by using a 1:5 mixture of ethyl acetate and
hexane to give the product 6a (52.3 mg, 92%) as a colorless oil. All
other substrates (5b–n and 15a–c) were subjected to similar conditions
with different reaction temperatures and times. Hydrolysis of 6a–n: A
1.0m solution of NaOH (0.40 mL, 0.40 mmol) was slowly added to each
solution of 6a–n (0.16 mmol) in methanol (2.0 mL)at 08C. The reaction
was complete within 30 min at room temperature. Extractive workup and
flash column chromatography gave 7a–n in over 95% yields.
Scheme 5. Transformations of 7a to 11a. Reagents and conditions:
a) Tf2O, pyridine, CH2Cl2, 08C, 1 h, 91%; b) 1-hexyne, CuI, [PdCl2-
A
63%; d) BF3·OEt2, CH2Cl2, 08C, 0.5 h, 86%; e) PhLi, THF, ꢀ788C to RT,
1 h, 83%; f) BF3·OEt2, CH2Cl2, 08C, 0.5 h, 70%; g) Tf2O, pyridine,
CH2Cl2, 08C, 0.5 h, 61%; h) 1-hexyne, CuI, [PdCl
608C, 4 h, 91%.
2ACHTUNGTRNE(UNNG PPh3)2], Et3N, DMF,
1
6a: IR(NaCl, cmꢀ1) 1761, 1596, 1199; H NMR (400 MHz, CDCl3) d 8.22
(m, 1H), 7.80 (m, 1H), 7.58 (s, 1H), 7.51–7.48 (m, 2H), 7.37 (d, J=
1.6 Hz, 1H), 5.38 (s, 1H), 5.27 (s, 1H), 2.34 (s, 3H), 2.12 ppm (s, 3H);
13C NMR (100 MHz, CDCl3) d; 169.53, 169.00, 152.22, 147.44, 135.33,
134.19, 129.07, 128.30, 126.77, 126.41, 125.54, 122.40, 120.03, 107.74, 21.31,
21.13 ppm; HRMS m/z calcd for C16H1O4 [M] 270.0892, found 270.0893.
Scheme 6. Cycloisomerization of aliphatic substrates 15a–c to 16a–c.
EDC=1,2-dichloroethane.
7a: IR(NaCl, cmꢀ1) 3164, 1655, 1602, 1597; 1H NMR (400 MHz, CDCl3)
d 8.57 (d, J=8.4 Hz, 1H), 7.69 (d, J=7.6 Hz, 1H), 7.55 (d, J=2.4 Hz,
1H), 7.49–7.42 (m, 2H), 7.31 (d, J=2.4 Hz, 1H), 5.50 (bs, 1H), 2.73 ppm
(s, 3H); 13C NMR (100 MHz, CDCl3) d 201.89, 151.86, 137.39, 135.35,
127.06, 126.87, 125.83, 125.70, 125.61, 120.28, 114.37, 30.07 ppm; HRMS
calculated for C12H11O2 (M+H), 187.0759; found, 187.0770.
ACHTUNGTRENNUNGkenACHTUNGTRENNUNGals were transformed to substrates 15a–c in four steps by
the known procedure. When substrates 15a–c were treated
with 3 mol% of NaAuCl4·H2O in EDC, the desired reaction
occurred smoothly to afford the corresponding benzo[7]an-
nulene-5,8-diyl diacetylates 16a–c in 45%, 68%, and 72%
yields, respectively. This implies that the present gold-cata-
lyzed procedure could provide a wide scope of benzo[7]an-
nulene-5,8-diyl diacetylates (such as 6a–n and 16a–c) start-
ing from not only aromatic substrates like 5a–n but also ali-
phatic substrates such as 15a–c.
Acknowledgements
Financial support was provided by a grant from the National Research
Foundation of Korea (NRF 3j201200000000953).
In summary, we have developed a novel gold-catalyzed
cascade reaction of 1-(2-(3-acetoxyprop-1-ynyl)phenyl)prop-
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C. H. Oh et al.
[9] a) N. Kim, Y. Kim, W. Park, D. Sung, A. K. Gupta, C. H. Oh, Org.
Lett. 2005, 7, 5289; For our Pt-catalyzed work, see: b) C. H. Oh,
J. H. Ryu, H. I. Lee, Synlett 2007, 15, 2337; c) C. H. Oh, J. H. Lee,
S. J. Lee, J. I. Kim, C. S. Hong, Angew. Chem. 2008, 120, 7615;
Angew. Chem. Int. Ed. 2008, 47, 7505; d) C. H. Oh, J. H. Lee, S. M.
Lee, H. J. Yi, C. H. Hong, Chem. Eur. J. 2009, 15, 71; e) C. H. Oh,
J. H. Yi, J. H. Lee, D. H. Lim, Chem. Commun. 2010, 46, 3007;
f) C. H. Oh, S. M. Lee, C. S. Hong, Org. Lett. 2010, 12, 1308;
g) C. H. Oh, S. Y. Tak, J. H. Lee, L. H. Piao, Bull. Korean Chem.
Soc. 2011, 32, 2978.
[10] D. Hildebrandt, G. Dyker, J. Org. Chem. 2006, 71, 6728.
[11] a) A. S. K. Hashmi, W. Yang, Y. Yu, M. M. Hansmann, M. Rudolph,
F. Rominger, Angew. Chem. Int. Ed. 2012, DOI: 10.1002/
anie.201207287. b) N. D. Shapiro, F. D. Toste, J. Am. Chem. Soc.
2008, 130, 9244; c) S. Wang, G. Zhang, L. Zhang, Synlett 2010, 5,
692.
[12] a) B. Alcaide, P. Almendros, J. M. Alonso, Molecules 2011, 16, 7815;
b) Huang, T. De Haro, C. Nevado, Chem. Eur. J. 2009, 15, 5904;
c) A. S. K. Hashmi, Angew. Chem. 2008, 120, 6856; Angew. Chem.
Int. Ed. 2008, 47, 6754; d) N. Marion, S. P. Nolan, Angew. Chem.
2007, 119, 2806; Angew. Chem. Int. Ed. 2007, 46, 2750; e) C. Fehr, J.
Galindo, Angew. Chem. 2006, 118, 2967; Angew. Chem. Int. Ed.
2006, 45, 2901; f) A. Fꢃrstner, P. Hannen, Chem. Eur. J. 2006, 12,
3006; g) A. Correa, N. Marion, L. Fensterbank, M. Malacria, S. P.
Nolan, L. Cavallo, Angew. Chem. 2008, 120, 730; Angew. Chem. Int.
Ed. 2008, 47, 718. For the Pt-versions, see: h) E. Mainetti, V. Mo-
uries, L. Fensterbank, M. Malacria, J. Marco-Contelles, Angew.
Chem. 2002, 114, 2236; Angew. Chem. Int. Ed. 2002, 41, 2132; i) W.
Rao, M. J. Koh, P. Kothandaraman, P. W. H. Chan, J. Am. Chem.
Soc. 2012, 134, 10811.
Keywords: benzo[7]annulenes · cyclization · gold catalysis ·
propargyl carboxylates · sequential activation
[1] a) M. Rudolph, A. S. K. Hashmi, Chem. Soc. Rev. 2012, 41, 2448;
b) A. Leyva-Pꢁrez, A. Corma, Angew. Chem. 2012, 124, 658; Angew.
Chem. Int. Ed. 2012, 51, 614; c) D. J. Gorin, F. D. Toste, Nature 2007,
446, 395; d) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. 2006,
118, 8064; Angew. Chem. Int. Ed. 2006, 45, 7896.
[2] a) D. Wang, R. Cai, S. Sharma, J. Jirak, S. K. Thummanapelli, N. G.
Akhmedov, H. Zhang, X. Liu, J. L. Petersen, X. Shi, J. Am. Chem.
Soc. 2012, 134, 9012; b) M. P. MuÇoz, Org. Biomol. Chem. 2012, 10,
3584; c) B. Chen, W. Fan, G. Chai, S. Ma, Org. Lett. 2012, 14, 3616.
[3] a) L. Ye, Y. Wang, D. H. Aue, L. Zhang, J. Am. Chem. Soc. 2012,
134, 31; b) A. S. K. Hashmi, I. Braun, P. Nçsel, J. Schꢂdlich, M. Wie-
teck, M. Rudolph, F. Rominger, Angew. Chem. 2012, 124, 4532;
Angew. Chem. Int. Ed. 2012, 51, 4456; c) A. S. K. Hashmi, M. Wie-
teck, I. Braun, P. Nçsel, L. Jongbloed, M. Rudolph, F. Rominger,
Adv. Synth. Catal. 2012, 354, 555; d) A. S. K. Hashmi, I. Braun, M.
Rudolph, F. Rominger, Organometallics 2012, 31, 644; e) S. Gaillard,
C. S. J. Cazin, S. P. Nolan, Acc. Chem. Res. 2012, 45, 778; f) N.
Krause, C. Winter, Chem. Rev. 2011, 111, 1994; g) A. Fꢃrstner, P. W.
Davies, Angew. Chem. 2007, 119, 3478; Angew. Chem. Int. Ed. 2007,
46, 3410.
[4] a) E. Jimꢁnez-NfflÇez, A. M. Echavarren, Chem. Rev. 2008, 108,
3326; b) V. Michelet, P. Y. Toullec, J. P. Genet, Angew. Chem. 2008,
120, 4338; Angew. Chem. Int. Ed. 2008, 47, 4268; c) P. García-
García, A. Martínez, A. M. Sanjuµn, M. A. Fernµndez-Rodríguez,
R. Sanz, Org. Lett. 2012, 14, 4970; d) S. Naoe, Y. Suzuki, K. Hirano,
Y. Inaba, S. Oishi, N. Fujii, H. Ohno, J. Org. Chem. 2012, 77, 4907.
[5] For recent reviews on gold-catalyzed reactions, see: a) A. S. K.
Hashmi, Chem. Rev. 2007, 107, 3180; b) D. J. Gorin, B. D. Sherry,
F. D. Toste, Chem. Rev. 2008, 108, 3351; c) J. Muzart, Tetrahedron
2008, 64, 5815; d) A. Corma, A. Leyva-Perez, M. J. Sabater, Chem.
Rev. 2011, 111, 1657.
[6] a) A. S. K. Hashmi, T. Hꢂffner, W. Yang, S. Pankajakshan, S. Schꢂ-
fer, L. Schultes, F. Rominger, W. Frey, Chem. Eur. J. 2012, 18,
10480; b) L. Wang, G. Li, Y. Liu, Org. Lett. 2011, 13, 3786; c) I. Na-
kamura, T. Sato, Y. Yamamoto, Angew. Chem. 2006, 118, 4585;
Angew. Chem. Int. Ed. 2006, 45, 4473; d) L. Zhang, J. Am. Chem.
Soc. 2005, 127, 16804; e) I. Nakamura, U. Yamagishi, D. Song, S.
Konta, Y. Yamamoto, Angew. Chem. 2007, 119, 2334; Angew. Chem.
Int. Ed. 2007, 46, 2284; f) I. Nakamura, T. Sato, M. Terada, Y. Yama-
moto, Org. Lett. 2007, 9, 4081; g) A. Buzas, F. Gagosz, Org. Lett.
2006, 8, 515; h) S. F. Kirsch, J. T. Binder, B. Crone, A. Duschek, T. T.
Haug, C. Liebert, H. Menz, Angew. Chem. 2007, 119, 2360; Angew.
Chem. Int. Ed. 2007, 46, 2310; i) M. Yu, G. Zhang, L. Zhang, Org.
Lett. 2007, 9, 2147; j) A. S. K. Hashmi, T. D. Ramamurthi, F. Ro-
minger, J. Organomet. Chem. 2009, 694, 592; k) A. S. K. Hashmi,
T. D. Ramanurthi, M. H. Todd, A. S. K. Tsang, Graf, Aust. J. Chem.
2010, 63, 1619; l) R. Kazem Shiroodi, A. S. Dudnik, V. Gevorgyan, J.
Am. Chem. Soc. 2012, 134, 6928.
[7] a) D. Garayalde, C. Nevado, ACS Catal. 2012, 2, 1462; b) A. S. K.
Hashmi, C. Lothschꢃtz, R. Dçpp, M. Ackermann, J. D. B. Becker,
M. Rudolph, C. Scholz, F. Rominger, Adv. Synth. Catal. 2012, 354,
133; c) A. S. K. Hashmi, L. Molinari, Organometallics 2011, 30,
3457; d) A. S. K. Hashmi, R. Dçpp, C. Lothschꢃtz, M. Rudolph, D.
Riedel, F. Rominger, Adv. Synth. Catal. 2010, 352, 1307; e) Y. Shi,
S. D. Ramgren, S. A. Blum, Organometallics 2009, 28, 1275;
f) A. S. K. Hashmi, C. Lothschꢃtz, R. Dçpp, M. Rudolph, T. D.
Ramamurthi, F. Rominger, Angew. Chem. 2009, 121, 8392; Angew.
Chem. Int. Ed. 2009, 48, 8243; g) Y. Shi, K. E. Roth, S. D. Ramgren,
S. A. Blum, J. Am. Chem. Soc. 2009, 131, 1802.
[13] a) M. J. Johansson, D. J. Gorin, S. T. Staben, F. D. Toste, J. Am.
Chem. Soc. 2005, 127, 18002; b) X. Moreau, J. Goddard, M. Ber-
nard, G. Lemi›re, J. M. López-Romero, E. Mainetti, N. Marion, V.
Mouri›s, S. Thorimbert, L. Fensterbank, M. Malacria, Adv. Synth.
Catal. 2008, 350, 43.
[14] a) S. Karmaka, A. Kim, C. H. Oh, Synthesis 2009, 194; b) P. Mau-
león, J. L. Krinsky, F. D. Toste, J. Am. Chem. Soc. 2009, 131, 4513.
[15] a) C. H. Oh, A. Kim, W. Park, D. I. Park, N. Kim, Synlett 2006, 2781;
b) C. H. Oh, A. Kim, New J. Chem. 2007, 31, 1719; c) C. H. Oh, A.
Kim, Synlett 2008, 777.
[16] X.-Z. Shu, S.-C. Zhao, K.-G. Ji, Z.-J. Zheng, X.-Y. Liu, Y.-M. Liang,
Eur. J. Org. Chem. 2008, 1418.
[17] J. Zhao, C. O. Hughes, F. D. Toste, J. Am. Chem. Soc. 2006, 128, 436.
[18] a) H. Suga, S. Higuchi, M. Ohtsuka, D. Ishimoto, T. Arikawa, Y. Ha-
shimoto, S. Misawa, T. Tsuchida, A. Kakehi, T. Baba, Tetrahedron
2010, 66, 3070; b) H. Suga, D. Ishimoto, S. Higuchi, M. Ohtsuka, T.
Arikawa, T. Tsuchida, A. Kekehi, T. Baba, Org. Lett. 2007, 9, 4359;
c) D. M. Hodgson, D. Angrish, Adv. Synth. Catal. 2006, 348, 2509;
d) A. Padwa, L. Precedo, M. A. Semones, J. Org. Chem. 1999, 64,
4079; e) C. Plꢃg, W. Friedrichsen, Tetrahedron Lett. 1992, 33, 7509;
f) C. M. M. Daconceicao, J. A. Mcritchie, D. Middlemiss, G. R. Proc-
tor, J. Chem. Res., Synop. 1995, 9, 347; g) J. W. Lown, K. Matsunoto,
Can. J. Chem. 1971, 49, 3443.
[19] A. S. K. Hashmi, Angew. Chem. 2010, 122, 5360; Angew. Chem. Int.
Ed. 2010, 49, 5232.
[20] a) N. A. Lengkeek, P. F. Greenwood, B. Nguyen, G. A. Koutsantonis,
M. J. Piggott, J. Comb. Chem. 2010, 12, 141; b) G. H. Posner, E. M.
Shulman-Roskes, C. H. Oh, J. Carry, J. V. Green, A. B. Clark, H.
Dai, T. E. Anjeh, Tetrahedron Lett. 1991, 32, 6489.
[21] a) J. Tang, S. Bhunia, S. Md, A. Sohel, M. Lin, H. Liao, S. Datta, A.
Das, R. Liu, J. Am. Chem. Soc. 2007, 129, 15677; b) B. Lu, C. Li, L.
Zhang, J. Am. Chem. Soc. 2010, 132, 14070; c) B. G. Pujanauski,
B. A. B. Prasad, R. Sarpong, J. Am. Chem. Soc. 2006, 128, 6786.
[8] a) S. Kobayashi, K. A. Jorgensen in Cycloaddition Reactions in Or-
ganic Synthesis Wiley-VCH, Weinheim, Germany, 2002; b) For cy-
cloaddition to seven-membered rings, see: H. Butenschçn, Angew.
Chem. 2008, 120, 5367; Angew. Chem. Int. Ed. 2008, 47, 5287.
Received: November 15, 2012
Published online: January 7, 2013
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