Gold-catalyzed hydrative carbocyclization of 1,5- and 1,6-diyn-3-ones via an oxygen transfer process

Article abstract of DOI:10.1021/jo801753g

(Chemical Equation Presented) This study reports new hydrative carbocyclizations of 1,5- and 1,6-diyn-3-ones catalyzed by PPh₃AuOTf, involving a π-alkyne-assisted oxygen transfer in the reaction mechanisms. Treatment of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes with PPh₃AuOTf (5 mol %) in wet 1,4-dioxane (23°C, 10 min) led to hydrative aromatization to give 4-hydroxyl-1-naphthyl ketones efficiently. This approach is also extendible to the hydrative cyclization of acyclic 1,5-diyn-3-ones, which afforded 4-cyclopentenonyl ketones in reasonable yields. On the basis of this oxygen-labeling study, we propose a plausible mechanism involving an alkyne-assisted oxygen transfer to generate key oxonium and gold-enolate intermediates.

Full text of DOI:10.1021/jo801753g

Gold-Catalyzed Hydrative Carbocyclization of 1,5- and
1,6-Diyn-3-ones via an Oxygen Transfer Process
Jhih-Meng Tang, Ting-An Liu, and Rai-Shung Liu*
Department of Chemistry, National Tsing-Hua UniVersity, Hsinchu, Taiwan, Republic of China
rsliu@mx.nthu.edu.tw
ReceiVed August 6, 2008
This study reports new hydrative carbocyclizations of 1,5- and 1,6-diyn-3-ones catalyzed by PPh3AuOTf,
involving a π-alkyne-assisted oxygen transfer in the reaction mechanisms. Treatment of 2-(alk-2-yn-1-
onyl)-1-alkynylbenzenes with PPh3AuOTf (5 mol %) in wet 1,4-dioxane (23 °C, 10 min) led to hydrative
aromatization to give 4-hydroxyl-1-naphthyl ketones efficiently. This approach is also extendible to the
hydrative cyclization of acyclic 1,5-diyn-3-ones, which afforded 4-cyclopentenonyl ketones in reason-
able yields. On the basis of this oxygen-labeling study, we propose a plausible mechanism involving an
alkyne-assisted oxygen transfer to generate key oxonium and gold-enolate intermediates.
SCHEME 1. Alkyne-Assisted Fragment Migration
Introduction
Metal-mediated atom-transfer cyclizations are not only mecha-
nistically interesting, but also synthetically useful to construct
complex molecule frameworks.1,2 One recent impact with gold
and platinum catalysis is the cycloizomerization of oxygen-
containing alkynylbenzenes via formation of intermediate I to
complete a transfer of oxygen atom or alkyl fragment; repre-
(1) Reviews: (a) Matyjaszewski, K.; Miller, P. J.; Fossum, E.; Nakagawa,
Y. Appl. Organomet. Chem. 1998, 12, 667. (b) Delaude, L.; Demonceau, A.;
Noels, A. F. Top. Organomet. Chem. 2004, 11, 155. (c) Clark, A. J. Chem. Soc.
ReV. 2002, 31, 1. (d) Byers, J. In Radicals in Organic Synthesis; Renaud, P.,
Sibi, M. P., Eds.; Wiley-VCH: New York, 2001; Vol. 1, pp 72-89. (e) Yet, L.
Tetrahedron 1999, 55, 9349. (f) Curran, D. P. In ComprehensiVe Organic
Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: New York, 1991; Vol. 4,
pp 779-831.
(2) Selected examples: (a) Cook, G. R.; Hayashi, R. Org. Lett. 2006, 8, 1045.
(b) Yang, D.; Yan, Y.-L.; Zheng, B.-F.; Gao, Q.; Zhu, N.-Y. Org. Lett. 2006, 8,
5757. (c) Yanada, R.; Koh, Y.; Nishimori, N.; Matsumura, A.; Obika, S.; Mitsuya,
H.; Fujii, N.; Takemoto, Y. J. Org. Chem. 2004, 69, 2417. (d) Yang, D.; Gu, S.;
Yan, Y.-L.; Zhu, N.-Y.; Cheung, K.-K. J. Am. Chem. Soc. 2001, 123, 8612.
(3) (a) Fu¨rstner, A.; Davies, P. W. J. Am. Chem. Soc. 2005, 127, 15024. (b)
Fu¨rstner., A.; Stelzer, F.; Szillat, H. J. Am. Chem. Soc. 2001, 123, 11863. (c)
Fu¨rstner, A.; Szillat, H.; Stelzer, F. J. Am. Chem. Soc. 2000, 122, 6785. (d)
Nakamura, I.; Sato, T.; Yamamoto, Y. Angew. Chem., Int. Ed. 2006, 45, 4473.
(e) Shimada, T.; Nakamura, I.; Yamamoto, Y. J. Am. Chem. Soc. 2004, 126,
10546.
sentative examples are provided in Scheme 1.3,4 The uses of
these cyclizations, however, are restricted to the preparation of
functionalized indene and five-membered heterocyclic com-
(4) (a) Dube´, P.; Toste, F. D. J. Am. Chem. Soc. 2006, 128, 12062. (b)
Nakamura, I.; Bajracharya, G. B.; Wu, H.; Oishi, K.; Mizushima, Y.; Gridnev,
I. D.; Yamamoto, Y. J. Am. Chem. Soc. 2004, 126, 15423. (c) Nakamura, I.;
Bajracharya, G. B.; Mizushima, Y.; Yamamoto, Y. Angew. Chem., Int. Ed. 2002,
41, 4328.
10.1021/jo801753g CCC: $40.75
Published on Web 10/04/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 8479–8483 8479

Tang et al.
TABLE 1. Catalytic Cyclization over Various Catalysts
pounds.1-4 We seek to expand new catalytic reactions involving
an oxygen transfer beyond the present scope. Herein we report
new hydrative carbocyclizations5,6 of 2-(alk-2-yn-1-onyl)-1-
alkynylbenzenes and acyclic 1,5-diyn-3-ones catalyzed by gold
species. These mechanistically interesting reaction represent a
transfer of an oxygen atom.
Before this work, Yamamoto reported8 AgSbF6-catalyzed
cyclization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes with al-
cohols in CH2Cl2, giving benzopyranyl allenes involving forma-
tion of silver-benzopyrylium intermediates II (eq 1). Although
Au(I) resembles Ag(I) in electronic property, the use of
PPh3AuOTf leads to a complete change in the cyclization
chemoselectivity of such substrates with water and alcohol, as
depicted in eq 2. Herein, formation of 4-hydroxyl-1-naphthyl
ketones stems from addition of ROH (R ) H, alkyl) at the
oxonim of gold-benzopyrylium intermediates III.
a 5 mol % catalyst, [diynone] ) 0.1 M, H2O (5 equiv) for entries
1-10. b Products are separated from silica column. c No water was
added.
structure of compound 2a relies on an X-ray diffraction study of
its related compound 2g (Table 2, entry 7).10
The preceding catalysis provides a new and facile synthesis
of highly functionalized 1-naphthol from easily prepared 2-(alk-
2-yn-1-onyl)-1- alkynylbenzenes. We prepared various ketones
1a-o with alterations of the R1, R2, R3, and R4 substituents to
demonstrate the generality of this new cyclization. Substrates
1a-c bearing a phenylethynyl group (R1 ) phenyl, entries 1-3)
are much more efficient than their hexynyl analogues 1d-f
(R1 ) n-Bu, entries 4-6) in this hydrative cyclization upon
comparison of their respective product yields and reaction
periods. This cyclization is very suitable for substrates 1g-i
with alterations of their R1 substituent with 3,5-dimethylphenyl,
4-fluorophenyl, 4-and methoxyphenyl (entries 7-9), but it
becomes inefficient with species 1j bearing a 4-trifluorometh-
ylphenyl group (entry 10). Entries 11-15 show the effects of
Results and Discussions
Table 1 shows our efforts to achieve the hydrative carbocy-
clization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes 1a over com-
monly used acid catalysts. PtCl2, PtCl2/CO,9 AuCl, AuCl3, and
ClAuPPh3 (Ph ) phenyl), each at 5 mol % loading, led to unreacted
1a exclusively in wet 1,4-dioxane at 23 °C. Under similar
conditions, the use of AuPPh3SbF6 gave a 69% yield of 4-benzoyl-
3-phenyl-1-naphthol 2a, and the yield was increased to 76% with
PPh3AuCl/AgOTf and a short time reaction (0.8 h). The effect of
counteranions is also pronounced for silver salts; AgSbF6 was
virtually inactive whereas AgOTf gave a 65% yield of 1-naphthol
2a with a long reaction period up to 10 h. This reaction time
indicates that AgOTf residues did not cause catalytic activity of
AuPPh3OTf. In dry 1,4-dioxane, all these acid catalysts including
PPh3AuOTf gave an exclusive recovery of starting diynone 1a
without cycloizomerization. Characterization of the molecular
(10) The X-ray data of compound 2g are provided in the Supporting
Information.
(11) Treatment of acyclic 1,6-diyn-3-ones 4h and 4i with PPh3AuOTf in wet
1,4-dioxane did not give the desired cyclized ketones 5h and 5i, but a messy
mixture of products. Spectral data of ketone substrates 4h and 4i were provided
in the Supporting Information.
(5) For Ru catalysts, see selected examples: (a) Trost, B. M.; Rudd, M. T.
J. Am. Chem. Soc. 2003, 125, 11516. (b) Trost, B. M.; Rudd, M. T. J. Am.
Chem. Soc. 2005, 127, 4763. (c) Odedra, A.; Wu, C.-J.; Pratap, T. B.; Huang,
C.-W.; Ran, Y. F.; Liu, R.-S. J. Am. Chem. Soc. 2005, 127, 3406. (d) Trost,
B. M.; Brown, R. E.; Toste, F. D. J. Am. Chem. Soc. 2000, 122, 5877.
(6) For gold and platinum catalysts, see the following examples: (a) Kennedy-
Smith, J. J.; Staben, S. T.; Toste, F. D. J. Am. Chem. Soc. 2004, 126, 4526. (b)
Yang, C.-Y.; Lin, G.-Y.; Liao, H.-Y.; Datta, S.; Liu, R.-S. J. Org. Chem. 2008,
73, 4907. (c) Chang, H.-K.; Datta, S.; Das, A.; Odedra, A.; Liu, R.-S. Angew.
Chem., Int. Ed. 2007, 46, 4744. (d) Das, A.; Liao, H.-H.; Liu, R.-S. J. Org.
Chem. 2007, 72, 9214. (e) Chang, H.-K.; Liu, R.-S. J. Org. Chem. 2007, 72,
8139. (f) Shapiro, N. D.; Toste, F. D. J. Am. Chem. Soc. 2007, 129, 4160. (g)
Jin, T.; Yamamoto, Y. Org. Lett. 2007, 9, 5259.
(7) For palladium catalyst, see Momiyama, N.; Kanan, M. W.; Liu, D. R.
J. Am. Chem. Soc. 2007, 129, 2230.
(8) Patil, N. T.; Pahadi, N. K.; Yamamoto, Y. J. Org. Chem. 2005, 70, 10096.
(9) For PtCl2/CO catalysts, see the following selected examples: (a) Fu¨rstner,
A.; Davies, P. W.; Gress, T. J. Am. Chem. Soc. 2005, 127, 8244. (b) Zhang, G.;
Catalano, V. J.; Zhang, L. J. Am. Chem. Soc. 2007, 129, 11358. (c) Taduri,
B. P.; Ran, Y.-F.; Huang, C.-W.; Liu, R.-S. Org. Lett. 2006, 8, 883. (d) Lo,
C.-Y.; Lin, C.-C.; Cheng, H.-M.; Liu, R.-S. Org. Lett. 2006, 8, 3153.
(12) The complete mass spectra of 18O-enriched 1a and 2a are provided in
the Supporting Information.
8480 J. Org. Chem. Vol. 73, No. 21, 2008

Carbocyclization of 1,5- and 1,6-Diyn-3-ones
TABLE 2. Gold-Catalyzed Hydrative Cyclization of Aromatic
1,6-Diyne-3-ones
TABLE 3. Gold-Catalyzed Cycliction of Diynone with Alcohol
substratea
R1 ) Ph, R3 ) R4 ) H
time (h)
H2O time
producta
(yieldb)
entry
substrate
R1 ) R2 ) Ph (1a)
R3 (equiv) (h)
1
2
3
R2 ) Ph (1a)
0.8
1.0
1.0
2a (75)
2b (59)
2c (73)
1
2
3
4
5
6
i-Bu
i-Bu
Me
2
2
2
2
2
4
3a (54%), 2a (8%)
3a (34%), 2a (28%)
3b (60%)
3c (59%), 2b (17%)
3d (55%), 2c (10%)
3e (58%), 2f (16%)
R2 ) Me (1b)
1a
1a
5
R2 ) Bu (1c)
n
R1 ) Me, R2 ) Ph (1b) Me
R1 ) Bu, R2 ) Ph (1c) Me
n
R1 ) Bu, R3 ) R4 ) H
R1 ) Ph, R2
)
nBu (1f) Me
n
4
5
6
R2 ) Bu (1d)
R2 ) Me (1e)
R2 ) Ph (1f)
16
24
24
2d (45)
2e (32)
2f (38)
a [Substrate] ) 0.1 M, dioxane, alcohol (5 equiv), 25 °C. b Products
are separated by silica gel column chromatography.
R2 ) Me, R3 ) R4 ) H
TABLE 4. Gold-Catalyzed Hydrative Carbocyclization of Acyclic
1,5-Diyn- 3-ones
7
8
9
10
R1 ) 3,5-Me2C6H3 (1g)
R1 ) 4-FC6H4 (1h)
0.5
1.0
0.5
2g (61)
2h (63)
2i (72)
2j (23)
R1 ) 4-MeOC6H4 (1i)
R1 ) 4-CF3C6H4 (1j)
24
R1 ) Ph, R2 ) Me
11
12
13
14
15
R3 ) H, R4 ) OMe (1k)
R3 ) H, R4 ) F (1l)
1.0
1.0
24
1.0
1.0
2k (82)
2l (93)
2m (11)
2n (93)
2o (75)
R3 ) OMe, R4 ) H (1m)
R3 ) F, R4 ) H (1n)
R3 ) Cl, R4 ) H (1o)
substratea
a [Substrate] ) 0.1 M, H2O (5 equiv), 1 h. b Products are separated by
silica gel column chromatography.
entry
R1
R2
time (h)
productsb (yields)
R3 ) Me
(1)
(2)
(3)
Ph
Ph
Ph
Ph (4a)
Me (4b)
Bu (4c)
2
2
2
5a (45%), 6a (17%)
5b (53%)
5c (48%)
the phenyl R3 and R4 substituents of diynones 1k-o, and their
cyclizations maintain high efficiencies except for compound 1m
bearing a R3 ) OMe group.
R3, R3 ) (CH2)5
This gold catalysis is also compatible with alcohol nucleo-
philes with examples provided in Table 3. Treatment of 1,6-
diyn-3-one 1a with isobutanol (3 equiv) and PPh3AuOTf catalyst
(5 mol %) in dry 1,4-dioxane produced 1-benzoyl-4-isobutoxy-
naphthalene 3a in 54% yield together with a small quantity of
1-naphthol 2a (8%); the yield of undesired species 2a was
further increased to 28% in wet 1,4-dioxane (entry 2). We only
(4)
(5)
(6)
(7)
Ph
Ph
4-FC6H4
4-FC6H4
Ph (4d)
2
5d (38%), 6d (27%)
5e (57%)
5f (55%), 7f (13%)
5g (73%)
Me (4e)
Ph (4f)
Me (4g)
0.5
0.5
0.5
a Conditions: 5 mol % catalyst, 2 equiv of H2O, 0.2 M dry dioxane,
25 °C. b Products are separated by silica gel column chromatography.
obtained cyclized product 3b in 60% yield in dry 1,4-dioxane
when MeOH was used as the nucleophile. This nucleophilic
aromatization was extendible to other 1,6-diyn-3-ones 1b-c and
1f, which gave 4-methoxy-1-naphthyl ketone products 3c,d in
55-59% yields in addition to minor side products 2b, 2c, and
2f. The proposed structure of compound 3b was verified because
it was also produced from the reaction of 1-naphthol 2a with
MeI and NaH in THF.
We also prepared acyclic 1,5-diyn-3-one substrates 4a-g to
expand the scope of this hydrative carbocyclization, as depicted
in Table 4. Treatment of these substrates with PPh3AuCl/AgOTf
(5 mol %) in wet 1,4-dioxane (25 °C) delivered 4-cyclopen-
tenonyl ketone products 5a-g in reasonable yields (38-73%).
To attain a smooth cyclization, the alkynyl R1 substituents
of these substrates are strictly limited to phenyl groups whereas
their R2 groups tolerate either alkyl or phenyl groups; such a
structure-activity pattern parallels that of aromatic diynones
1a-f (entries 1-6, Table 2). In such reactions, we also obtained
side products 6a, 6d, and 7f in minor proportions (13-27%),
produced from gold-catalyzed alkyne hydration. Subsequent
treatment of 6a and 7f with the same gold catalyst in wet 1,4-
(13) Reviews for benzopyrilium see: (a) Asao, N. Synlett 2006, 11, 1645.
(b) Kuznetsov, E. V.; Shcherbakova, I. V.; Balaban, A. T. AdV. Heterocycl. Chem.
1990, 50, 157.
(14) For metal catalysis involving benzopyrylium as reaction intermediates,
see: (a) Beeler, A. B.; Su, S.; Singleton, C. A.; Porco, J. A., Jr. J. Am. Chem.
Soc. 2007, 129, 1413. (b) Asao, N.; Takahashi, K.; Lee, S.; Kasahara, T.;
Yamamoto, Y. J. Am. Chem. Soc. 2002, 124, 12650. (c) Asao, N.; Aikawa,
H.; Yamamoto, Y. J. Am. Chem. Soc. 2004, 126, 7458. (d) Nakamura, I.;
Mizushima, Y.; Gridnev, I. D.; Yamamoto, Y. J. Am. Chem. Soc. 2005, 127,
9844. (e) Iwasawa, N.; Shido, M.; Kusama, H. J. Am. Chem. Soc. 2001, 123,
5814.
(15) Spectral data of compounds 8 and 9 are provided in the Supporting
Information. Structural assignment of compound 9 was determined by 1H
NOE-effect with the map shown below. The hydroxyl proton has a proton
signal at δ 11.7, which disappeared upon treatment with CD3OD in hot CDCl3
(60 °C, 2 h).
J. Org. Chem. Vol. 73, No. 21, 2008 8481

Tang et al.
in a Michael-type reaction will give cyclohexenone E, which
ultimately forms observed product 2a. This proposed mechanism
also rationalizes the formation mechanism of 4-cyclopentenonyl
ketone 5a from acyclic 1,5-diyn-3-one 4a, which includes similar
gold enolate F and gold cyclopentenonyl intermediate G. As
depicted in eq 4, gold-free ketone species 8 (Ar ) 4-MeO-C6H4)
is unlikely to be an intermediate for 2-naphthol product because it
led to different aromatization compound 9 catalyzed by PPh3AuCl/
AgOTf under reaction conditions according to our control experi-
ment.15 This information supports the proposed conversion of gold-
enolate F to gold-cyclohexenonyl species G.
FIGURE 1
dioxane (25 °C) failed to give major cyclized products 5a and
5f; these minor products were not intermediates for desired
cyclopentenonyl ketones. We were unsuccessful in obtaining
4-cyclohexenonyl ketone products through hydrative cyclization
of acyclic 1,6-diyn-3-ones under similar conditions.11
We performed a 17O-labeling experiment to elucidate the
mechanism of the hydrative cyclization. Treatment of aromatic
1,6-diyn-3-one 1a with H217O and PPh3AuOTf (5 mol %) in
1,4-dioxane provided 17O-2a, which showed a broad peak (δ
75 ppm) assignable to the phenoxy oxygen. We did not observe
any Cd17O signal of species 17O-2a in the in situ NMR study,
or from the purified 17O-2a sample by flash chromatography.
This isotopic labeling experiment provides results compatible
with our observation for the alcohol-based aromatization (see
Table 3). In a separate experiment, we also prepared 18O-1a
bearing a ca. 45% 18O enrichment at the carbonyl oxygen, and
its PPh3AuOTf-catalyzed cyclization with natural H2O (5.0
equiv) afforded the cyclized product 18O-2a, which retained a
16
This proposed mechanism also provides rationales for the high
efficiencies for diynones 1a-c bearing an arylethynyl group
(R1 ) aryl), which are more efficient than their hexynyl
analogues 1d-f (R1 ) n-Bu), as depicted in Table 2 (entries
1-6). We envisage that the aryl group of π-alkyne species A
stabilizes the vinyl cationic resonance (Scheme 3) to facilitate
the formation of benzopyrylium B. The oxygen labeling
experiments also exclude the possibility that hydrated ketone
species I is responsible for formation of cyclic ketal intermediate
C, which is expected to give cyclized product with the 17O-
labeling at both the ketone and phenol groups.
significant amount of 18O-content at the ketone group (υCO
)
Conclusion
1655 cm-1; υCO ) 1620 cm-1) upon comparison of their
respective mass parent peaks (Figure 1).12 The small peak at
327 of compound 18O-2a is assignable to the M + 1 peak of
18O-embedded 2a, and we did not obtain a clear peak at 328
assignable to a incorporation of two 18O-atoms.
18
In this investigation, we report the use of PPh3AuOTf to
implement hydrative carbocyclization of 2-(alk-2-yn-1-onyl)-
1-alkynylbenzenes and acyclic 1,5-diyn-3-ones under ambient
conditions, providing 4-ketonyl-1-naphthols and cyclopentenyl
ketones, respectively. The mechanisms of these reactions have
been studied by oxygen-labeling and suitable control experi-
ments; we propose that such hydrative carbocyclizations proceed
through an alkyne-assisted oxo transfer to generate gold-
containing oxonium and enolate intermediates to complete the
cyclization.16
(16) (a) Treatment of 1,5-diyn-3-one 4a with MeOH (2 equiv) and PPh3AuCl/
AgOTf (5 mol %) in dry dioxane (25 °C, 4h) gave 4-cyclopentenonyl ketone 5a
and 6a in 46% and 28% yields, respectively. Formation of ketone 5a is probably
due to easy hydration of ketal speices J.
On the basis of oxygen labeling experiments, we propose a
plausible mechanism in Scheme 2, which involves benzopyrylium
B as the reaction intermediate.13,14 We believe that the cyclization
efficiency of this catalysis depends on the state of the equilibrium
of A and A′. This hypothesis also rationalizes the observation that
a 4-methoxyphenyl group greatly decreases the cyclization ef-
ficiency (Table 2, entry 13) because it increases the ketone basicity
to favor σ-bonded ketone A′. Once the benzopyrylium B is formed,
its oxonium group is subject to the attack of water to form cyclic
ketal species C. A subsequent proton-catalyzed opening of this
ketal species generates gold enol form D, which subsequently
produces ketone form D′. We believe that the Bronsted acid
catalyzes the ketone-enol equilibrium, and a subsequent attack
of the enol group of species D on the proton-coordinated alkynone
(17) Barbot, F.; Miginiac, Ph. J. Organomet. Chem. 1992, 440, 249.
8482 J. Org. Chem. Vol. 73, No. 21, 2008

Carbocyclization of 1,5- and 1,6-Diyn-3-ones
SCHEME 2. A Plausible Mechanism for the Hydrative Carbocyclization Reaction
SCHEME 3. A Proposed Mechanism to Rationalize
18O-Labeling Results
125.2, 123.4, 122.0, 110.1; HRMS calcd for C23H16O2 324.1150,
found:324.1152.
Experimental Procedure for Cyclization of 4,4-Dimethyl-1,6-
diphenylhexa-1,5-diyn-3-one (4a) to 4-Benzoyl-5,5-dimethyl-3-
phenylcyclopent-2-enone (5a) and 3,3-Dimethyl-1,6-diphenylhex-
5-yne-1,4-dione (6a). A flask containing AuClPPh3 (9.0 mg, 0.018
mmol) and AgOTf (4.7 mg, 0.018 mmol) was charged with dioxane
(0.26 mL) and the mixture was stirred for 2 min. To this solution
was added diynone 4a (100 mg, 0.367 mmol) and H2O (13.2 mg,
0.73 mmol) in dioxane (0.73 mL). After consumption of starting
diynone 4a, the solution was evaporated to dryness, and the residues
were purified by column chromatography (hexane/ethyl acetate: 5/1)
to yield cyclopentenone 5a (47.8 mg, 0.165 mmol, 45%) and
diketone 6a (18.1 mg, 0.062 mmol, 17%).
5a: colorless oil; IR (nujol, cm-1) ν 1670 (s), 1607 (s), 1701 (s),
1603 (s); 1H NMR (400 MHz, CDCl3) δ 8.04 (dd, J ) 6.8, 1.6 Hz, 2
H), 7.65 (tt, J ) 7.4, 1.2 Hz, 1 H), 7.55 (dd, J ) 7.9, 0.6 Hz, 2 H),
7.47-7.44 (m, 2 H), 7.36-7.29 (m, 3 H), 6.72 (s, 1 H), 5.12 (s, 1 H),
1.42 (s, 3 H), 0.94 (s, 3 H); 13C NMR (100 MHz, CDCl3) δ 211.1,
197.9, 170.0, 137.4, 133.8, 133.2, 131.0, 129.1 (2 × CH), 128.9 (2 ×
CH), 128.4 (2 × CH), 127.2, 127.0 (2 × CH), 59.7, 48.1, 27.3, 20.6.
HRMS calcd for C20H18O2 290.1307, found 290.1304.
6a: pale yellow oil;. IR (nujol, cm-1) ν 2157 (w), 1692 (s), 1672
(s), 1605 (s); 1H NMR (400 MHz, CDCl3) δ 7.94 (dd, J ) 8.0, 1.2
Hz, 2 H), 7.53 (d, J ) 7.5 Hz, 1 H), 7.50-7.48 (m, 2 H), 7.43-7.37
(m, 3 H), 7.32 (td, J ) 7.2, 1.4 Hz, 2 H), 3.44 (s, 2 H), 1.40 (s, 6
H); 13C NMR (100 MHz, CDCl3) δ 197.3, 192.5, 136.9, 133.1,
132.9 (2 × CH), 130.4, 128.5 (2 × CH), 128.5 (2 × CH), 128.0
(2 × CH), 120.3, 92.2, 85.8, 48.1, 46.2, 24.9 (2 × CH3). HRMS
calcd for C20H18O2 290.1307, found 290.1309.
Experimental Sections
General Sections. Synthesis of aromatic 1,6-diyne-3-ones has
been previously reported in the literature.8 2,2-Dimethylbut-3-yn-
1-ol was prepared according to literature procedure.17 1H NMR
spectra were run at 600 and 400 MHz and 13C NMR experiments
were operated at 125 and 100 MHz in CDCl3 or CD2Cl2 solution.
Experimental Procedure for Cyclization of 1,6-Diyne-3-one
(1a) to 2-Naphthol Derivative (2a). A flask containing AuClPPh3
(8.0 mg, 0.016 mmol) and AgOTf (4.2 mg, 0.016 mmol) was
charged with dioxane (0.26 mL) and the mixture was stirred for 2
min. To this mixture was added diynone 1a8 (100 mg, 0.326 mmol)
and H2O (29.3 mg, 1.63 mmol) in dioxane (3 mL). After complete
consumption of starting diynone 1a, the solution was evaporated
to dryness, and the residues were eluted through a short silica
column (hexane/ethyl acetate: 5/1) to afford 1-naphthyl ketone 2a
(79.7 mg, 0.244 mmol, 75%) as a yellow oil. IR (nujol, cm-1):
3310 (br s), 3012 (s), 1652 (m), 1643 (m), 1251 (s); 1H NMR (400
MHz, CDCl3) δ 8.25 (dd, J ) 7.5, 1.4 Hz, 1H), 7.69 (dd, J ) 7.4,
0.9 Hz, 1 H), 7.58 (dd, J ) 8.1, 1.0 Hz, 2 H), 7.48-7.40 (m, 2 H),
7.34 (tt, J ) 7.4, 1.5 Hz, 1 H), 7.25-7.16 (m, 5 H), 7.13-7.09 (m,
2 H), 6.83 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 200.1, 152.0,
140.1, 138.6, 138.4, 133.0, 132.2, 129.6 (2 × CH), 129.2 (2 ×
CH), 128.3, 128.1 (2 × CH), 128.0 (2 × CH), 127.7, 127.3, 125.4,
Acknowledgment. The authors wish to thank the National
Science Council, Taiwan for supporting this work.
Supporting Information Available: Experimental proce-
dures for the synthesis of reaction substrates and catalytic
operations, NMR spectra, spectral data of compounds 1a-7f,
8, and 9, and X-ray structural data of compound 2g. This
material is available free of charge via the Internet at
http://pubs.acs.org.
JO801753G
J. Org. Chem. Vol. 73, No. 21, 2008 8483