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Efficient synthesis of conjugated alkynyl cycloalkenones Pd(PPh3)4ЦAgOAc- catalyzed direct coupling of 1-alkynes with 3-oxocycloalkenyl triflates.

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Full Paper
Received: 1 August 2009
Revised: 11 October 2009
Accepted: 26 October 2009
Published online in Wiley Interscience: 17 December 2009
(www.interscience.com) DOI 10.1002/aoc.1592
Efficient synthesis of conjugated alkynyl
cycloalkenones: Pd(PPh3)4 –AgOAccatalyzed direct coupling of 1-alkynes
with 3-oxocycloalkenyl triflates
Chenggang Jiang, Zonglei Zhang, Hangxian Xu, Liang Sun, Lanhai Liu
and Cunde Wang∗
Palladium – silver acetate-catalyzed cross coupling of vinyl triflates and 1-alkynes was investigated. This strategy offered a
very straightforward and efficient method for access to conjugated alkynyl cycloalkenones from the conjugated vinyl triflates
and 1-alkynes. Moreover, the triflates derived from 1,3-cycloalkadione needed no further purification and could be reacted
c 2009
immediately with 1-alkynes to provide the conjugated alkynyl cycloalkenones in excellent overall yields. Copyright John Wiley & Sons, Ltd.
Keywords: conjugated alkynyl
gashira–Linstrumelle reaction
cycloalkenones;
3-oxocycloalkenyl
Introduction
208
Many natural products which contain conjugated eneynes or
enediynes exhibit an exceptional biological profile due to
their unique molecular structure, striking mode of action and
high potency,[1,2] and the play important ecological roles.[3 – 6]
Conjugated enynes are important synthetic intermediates since
conjugated enyne moiety can be readily converted into the
corresponding diene system.[7]
Conjugated eneyne units are also core or versatile building
blocks that can undergo various synthetically useful compounds
with unusual electrical, optical or structural properties, which
are designed for various applications in material science,[8]
and therefore the efficient synthesis of these compounds
has attracted interest from synthetic organic chemists. Many
methods can be used for the synthesis of conjugated enynes.
Conjugated enynes are readily obtained either by addition of
metal acetylides to aldehydes or ketones followed by elimination,
or by coupling alkynes with vinyl halides or triflates, the
so-called Sonogashira–Linstrumelle reaction.[1] Because of its
stereoselectivity, the latter process has gained a wide audience.[9]
Much researches manifesting transition metal-mediated crosscoupling reactions are widely recognized as selective, highyielding methods for the synthesis of complex organic compounds
and have proven to be powerful reactions for mild, highly efficient
carbon–carbon bond formation.[10] Among these reactions,
palladium is recognized as one of the most versatile transition
metal catalysts in synthetic organic chemistry, owing to excellent
levels of selectivity and high functional group compatibility. The
palladium-catalyzed cross-coupling reactions of terminal alkynes
with sp2 halides/triflates, in the presence (Sonogashira–Hagihara
alkynylation)[11] or in the absence (Heck alkynylation)[12] of a
copper co-catalyst, are even more useful synthetically and have
been extensively used in the stereospecific synthesis of conjugated
Appl. Organometal. Chem. 2010, 24, 208–214
triflates;
palladium(0)
catalyst;
silver
acetate;
Sono-
enynes.[13] Conjugated enynes were also formed using a coupling
reaction between alkenylzirconium compounds and alkynyl
halides,[14] or by the palladium-catalyzed hydrostannylation
of alkynyl esters, followed by Stille coupling with alkynyl
halides,[15] or by the palladium-catalyzed coupling reaction of
vinyl tosylate and terminal acetylenes.[16] Moreover, conjugated
enynes can be also conveniently prepared by palladium-catalyzed
cross-coupling reactions of terminal alkynes with β-halo-α,βunsaturated ketones. As in the other palladium-catalyzed cross
coupling reactions, aryl and vinyl triflates are useful alternatives to
halides in the Sonogashira reaction.
Traditionally, silver salts are used as stoichiometeric oxidants for
the oxidation of various organic or inorganic substrates. Recently
some reports have shown that silver salt catalysts or co-catalysts
promote efficient organic reactions.[17] Significant development
of the palladium(0)-silver salt catalyzed cross-coupling reactions
has occurred only in the past decade. In particular palladium
complex and silver iodide are efficient catalysts for the coupling
of sensitive vinyl triflates and 1-alkyne.[17] This result encouraged
us to make a detailed investigation into the combined catalyst of
Pd complex and silver salts. During studies on the preparation of
structurally complex natural molecular, we needed a key unit with
a core building block of 3-alkylethynyl-2-methylcycloalk-2-enone.
Initially the coupling reaction was studied with silver halides
as a co-catalyst. There were some drawbacks, such as the poor
solubility of silver halides in this apolar solvent. Recent studies have
∗
Correspondence to: Cunde Wang, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
E-mail: cundeyz@hotmail.com
SchoolofChemistryandChemicalEngineering,YangzhouUniversity,Yangzhou
225002, People’s Republic of. China
c 2009 John Wiley & Sons, Ltd.
Copyright Pd(PPh3 )4 –AgOAc-catalyzed synthesis of conjugated alkynylcycloalkenones
Tf2O, pyridine,
CH2Cl2, 24 h,
-78°C to r.t.
O
R
n
92-97%
O
R
O
Pd(PPh3)4, AgOAc,
OTf 1-Alkyne,
DIPEA,
DMF, 50°C, 10 min.
n
86-98%
R′
R
n
2a-d
1a-d
O
R = CH3, H
R′
1-Alkyne:
n = 1, 2
HC C R′
OH
3-18
OH
OH
OCH3
OH
Scheme 1. Synthesis of 3-(alk-1-ynyl) cycloalk-2-enone by Pd–AgOAccatalyzed through 3-trifluoromethanesulfonyloxycycloalk-2-enone from
1,3-cycloalkadione.
shown that silver acetate exhibits interesting catalytic activities
functioning as a transition metal catalyst.[18] However, to the best
of our knowledge, there have been no reports on palladium–silver
acetate-catalyzed Sonogashira–Linstrumelle coupling reaction of
alkynes with vinyl triflates. We intended to make a modification
that silver halides were therefore replaced by silver acetate because
of its better solubility in organic solvents. In the article, we report
a mild coupling reaction catalyzed by a new combination of
catalysts: Pd(PPh3 )4 and AgOAc to prepare 3-alkynylcycloalk-2enones.
Results and Discussion
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
[Pd]
catalyst
PdCl2
Pd(OAc)2
Pd(PPh3 )4
Pd2 (dba)3
PdCl2 (PPh3 )2
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Pd(PPh3 )4
Ag
salt
Base
i Pr NEt
AgI (20 mol%)
2
i Pr NEt
AgI (20 mol%)
2
i Pr NEt
AgI (20 mol%)
2
i Pr NEt
AgI (20 mol%)
2
i
AgI (20 mol%)
Pr2 NEt
i Pr NEt
AgBr (20 mol%)
2
AgOAc (20 mol%) i Pr2 NEt
i Pr NEt
AgBF4 (20 mol%)
2
i Pr NEt
AgOTf (20 mol%)
2
Ag2 CO3 (20 mol%) i Pr2 NEt
AgOAc (20 mol%) i Pr2 NEt
AgOAc (20 mol%) Et3 N
AgOAc (20 mol%) i Pr2 NEt
AgOAc (20 mol%) pyridine
AgOAc (20 mol%) K2 CO3
AgOAc (10 mol%) i Pr2 NEt
a
Isolated
yield
based
trifluoromethanesulfonate.
on
Solvent
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
MeCN
DMF
THF
DMF
DMF
DMF
Yield
(%)a
75
82
84
82
80
83
96
81
95
73
88
90
85
48
53
91
2-methyl-3-oxocyclopent-1-enyl
co-catalyst AgI (20 mol%) and i Pr2 NEt (1.5 equiv.) in DMF at 50 ◦ C
(75% yield, Table 1, entry 1). Similar results were obtained at 82%
(Table 1, entry 2), 84% (Table 1, entry 3), 82% (Table 1, entry 4) and
80% (Table 1, entry 5) yield when Pd(OAc)2 , Pd(PPh3 )4 , Pd2 (dba)3
and PdCl2 (PPh3 )2 were used as replacements, respectively. The
result showed that Pd(PPh3 )4 catalyst gave the best result. Further
screening revealed that silver salts as a co-catalyst affected the
coupling reaction in degree (Table 1, entries 3, 6–10). Indeed,
in the presence of a catalytic amount of Pd(PPh3 )4 and a slight
excess of i Pr2 NEt as base in DMF, silver acetate or triflate led
to the clean formation of compound in high yields (96% yield,
Table 1, entry 7 and 95% yield, Table 1, entry 9 respectively). Other
silver salts such as silver iodide, fluoroborate or carbonate proved
to be efficient in this reaction too, although lower yields were
obtained (Table 1, entries 3, 6, 8 and 10). This result encouraged us
to make a detailed investigation. Therefore, we examined various
bases (i Pr2 NEt, Et3 N, pyridine, and K2 CO3 ) and solvents (DMF,
MeCN and THF) (Table 1, entries 3, 11, 12, 13). Among these tested
conditions, i Pr2 NEt, Et3 N could efficiently promote this reaction
in DMF as solvent in high yield. However, the weak organic
base like pyridine or inorganic base such as potassium carbonate
promoted limitedly this coupling reaction in lower yields (Table 1,
entries 14 and 15). Furthermore, the co-catalyst silver acetate
concentration was reduced to 10 mol% to yield product 3 at 91%.
(Table 1, entry 16) The result showed that yields of product 3
were not obviously different when silver acetate concentration
was reduced from 20 to 10 mol%. Under general and optimized
conditions [triflates, alkynes, Pd(PPh3 )4 , AgOAc and i Pr2 NEt in the
mole ratios of 1 : 1.1 : 0.05 : 0.20 : 1.5 in DMF at 50 ◦ C for 10 min],
a series of triflates and alkynes were tested toward this coupling
reaction. As indicated in Table 2, various triflates and alkynes were
effective for this coupling reaction, and the desired products 3–18
could be obtained in excellent yields (Table 2, entries 1–16).
The results in Table 2 show that the palladium-catalyzed crosscoupling reaction of vinyl triflates with terminal alkynes in
the presence of a co-catalyst of silver acetate is an effective
c 2009 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
209
Many studies have indicated that the successful implementation
of vinyl and aryl triflates as the electrophilic components in these
reactions has greatly expanded the utility of these transformations,
as the reactive species are readily available from the corresponding
carbonyl compounds or phenols.[19] In particular, conjugated keto
vinyl triflates proved to be good partners.[20]
Considering the synthesis of a complex molecule with 3-alkynyl
conjugated cycloalkenone unit, we needed an active intermediate
for the sp2–sp coupling reaction, so we chose vinyl triflates
as partners of coupling reaction. Although the reaction was
slow (reaction time 4 days), so that triflation of the ketone was
effected by triflic anhydride using pyridine in dichloromethane
at −78 ◦ C,[21] the desired product 2a–d with a conjugated
system was stable when the reaction temperature rose from
−78 ◦ C to ambient temperature. An initial short incubation of the
reaction components at −78 ◦ C followed by warming to higher
temperatures provided the best results. The resulting mixture was
allowed to reach ambient temperature after 30 min, the reaction
was finally speeded up and the reaction was completed in a
short time (1 day). Simple workup followed by silica gel column
purification provided the monotriflated product 2a–d (Scheme 1).
Initially the reaction was studied with 2-methyl-3-oxocyclopent1-enyl triflate 1a and but-3-yn-1-ol 2a, which were selected as
suitable substrates for reaction development (Table 1). At the
outset, various palladium catalysts were screened according to
reported results.[22] We observed that the reactions using various
palladium catalysts worked well when the reaction was carried
out using 2-methyl-3-oxocyclopent-1-enyl triflate 1a and but-3yn-1-ol 2a (1.1 equiv). The desired product 3a was formed when
the reaction was carried out in the presence of PdCl2 (5 mol%),
Appl. Organometal. Chem. 2010, 24, 208–214
Table 1. Pd–Ag salt-catalyzed cross-coupling reaction of trifluoromethanesulfonate 1a with but-3-yn-1-ol 2a
C. Jiang et al.
Table 2. Preparation of conjugated alkynyl cycloalkenones by
Pd(PPh3 )4 –AgOAc-catalyzed coupling reaction
Entry
1
R
n
CH3
1
R
Product
Yield (%)a
3
96
2
CH3
1
4
90
3
CH3
1
5
96
4
CH3
1
6
92
7
89
8
86
9
88
10
92
11
93
12
92
13
90
14
94
15
96
16
98
17
97
18
96
OH
MeO
CH3
1
OH
6
CH3
1
7
CH3
1
8
CH3
2
OH
HO
9
CH3
2
10
CH3
2
OH
OH
11
CH3
2
12
CH3
2
13
H
2
OH
MeO
14
H
2
15
H
2
16
H
1
a
OH
Isolated yields (for reaction conditions see text).
210
methodology for the construction of conjugated enyne systems.
As a classic Sonogashira reaction, the coupling reaction of aryl
and alkenyl halides with terminal alkynes by palladium-catalyzed
in the presence of a co-catalyst of cuprous iodide was carried
out generally. Moreover in the other palladium-catalyzed cross
coupling reactions, vinyl and aryl triflates are useful alternatives to
halides in the Sonogashira reaction using cuprous iodide as a cocatalyst. Under our general and optimized conditions [2-methyl3-oxocyclopent-1-enyl triflate 1a, but-3-yn-1-ol 2a, Pd(PPh3 )4 ,
AgOAc and i Pr2 NEt in the mole ratios of 1 : 1.1 : 0.05 : 0.20 : 1.5
in DMF at 50 ◦ C for 10 min], a 96% yield for product 3 (Table 1,
entry 1) was obtained. Using identical reaction conditions, a
yield of 73% for product 3 was obtained when CuI was used
as a replacement. Then reaction time was extended from 10 to
90 min at 80 ◦ C; a yield in 94% for product 3 was obtained using
CuI as a co-catalyst. The results show that a synthetically useful
www.interscience.wiley.com/journal/aoc
R
n
O
Pd(PPh3)4, AgOAc,
OTf 1-Alkyne,
DIPEA,
DMF, 50°C, 10 min.
n
R′
R
O
n
1a-d
R = CH3, H
HO
5
Tf2O, pyridine,
CH2Cl2, 24 h,
-78°C to r.t.
O
R
O
1-Alkyne:
n = 1, 2
HC C R′
R'
OCH3
Scheme 2. One-pot synthesis of 3-(alk-1-ynyl) cycloalk-2-enone by
Pd–AgOAc-catalyzed directed from 1,3-cycloalkadione.
palladium-catalyzed cross-coupling of vinyl triflates with terminal
alkynes in the presence of a co-catalyst of silver acetate has been
discovered as an efficient method compared with this type of
chemical transformation using CuI as a co-catalyst. The extremely
mild reaction conditions, short reaction time and high isolated
yield also make it a superior method to other existing processes.
A proposed mechanism[23] for the coupling reaction of vinyl
halides or triflates with 1-alkynes by Pd(0)-catalyzed with silver salts
as co-catalyst indicated that the alkynyl silver was produced firstly
from a π -complex between the silver cation and the triple bond of
the alkyne after addition of DIPEA, following the alkynyl silver being
transmetalated to palladium species, then with the alkynyl silver
acting as a nucleophile, alkynylation reactions proceeded. The
results clearly demonstrated that the silver catalysts in coupling
reactions proceeded through such intermediates as alkynyl silver,
which form a key step. Because of its better solubility in organic
solvents, supplying more silver cations, silver acetate becomes a
more effective catalyst than silver halides.
Based on understanding of the mechanism of the Pd–AgOAccatalyzed coupling reactions, we considered that triflate anions are
present during the cross-coupling reaction involving vinyl triflates
and alkynes. Thus, triflate anion from the triflation reaction of 1,3cycloalkdione should not disturb the next cross-coupling reaction.
We aimed to make one-pot synthesis of 3-(alk-1-ynyl)cycloalk2-enone catalyzed by Pd–AgOAc direct from 1,3-cycloalkadione
possible without obtaining intermediate triflates. Vinyl triflates
2a–d contain a conjugated enone structural moiety with a
double bond substituted by a trifluoromethanesulfonyl group.
This substitution enhances the electrophilicity of the double bond
carbon. These unique structural features might be the key elements
that differentiate these vinyl triflates 2a–d from other vinyl triflates
without any conjugated system with respect to their reactivities
in coupling with terminal alkynes. Thus, a modification of the
protocol made it possible to obtain cross-coupling products from
the intermediate vinyl triflates (2a–d) without any workup as crosscoupling components when generated directly from carbonyl
compounds.(Scheme 2, Table 3).
Conclusion
In conclusion, we have studied a synthetically useful palladium–silver acetate-catalyzed cross coupling of the conjugated
vinyl triflates and terminal acetylenes. Some conjugated alkynyl cycloalkenones were efficiently synthesized using palladium–silver
acetate as a combined catalyst in the presence of diisopropylethylamine at 50 ◦ C in not more than 15 min at 86–98% yield. The
extremely mild reaction conditions, simple procedure and high
c 2009 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 208–214
Pd(PPh3 )4 –AgOAc-catalyzed synthesis of conjugated alkynylcycloalkenones
Table 3. One-pot synthesis of conjugated alkynyl cycloalkenones
direct from 1,3-alkadione
R
Product
Yield (%)a
5
90
6
89
1
9
84
CH3
2
14
91
5
H
2
15
90
6
H
2
16
88
7
H
1
18
90
Entry
R
n
1
CH3
1
2
CH3
1
3
CH3
4
MeO
2-Methyl-3-trifluoromethanesulfonylcyclohex-2-enone (2b)
Compound 2b was obtained as a colorless oil, yield 95%; 1 H NMR
(300 MHz, CDCl3 ) 2.79–2.73 (m, 2H), 2.52–2.47 (m, 2H), 2.14–2.04
(m, 2H), 1.86 (t, J = 2.1 Hz, 3H); 13 C NMR (75 MHz, CDCl3 ): 197.53,
162.13, 128.05, 118.38 (q, J = 319 Hz), 36.58, 28.77, 20.66, 9.04; IR
(film): 1693, 1669, 1422, 1243, 1213, 1139; anal. calcd for C8H9 F3 O4 S:
C, 37.21; H, 3.51; found C, 37.21; H, 3.51.
3-Trifluoromethanesulfonylcyclopent-2-enone (2c)
a
MeO
Isolated yields (reaction conditions see text).
3-Trifluoromethanesulfonylcyclohex-2-enone (2d)
isolated yield also make it a superior method over other existing
processes. Moreover, the triflates derived from 1,3-cycloalkadione
without purification were reacted immediately with 1-alkynes to
provide the conjugated alkynyl cycloalkenones in excellent overall
yields (84–91%).
Compound 2d was obtained as a colorless oil, yield 97%; 1 H
NMR (300 MHz, CDCl3 ) δ 5.76 (t, J = 1.5 Hz, 1H), 2.84–2.78 (m,
2H), 2.52–2.49 (m, 2H), 2.14–1.98 (m, 2H); 13 C NMR (75 MHz,
CDCl3 ): 197.68, 164.14, 128.05, 118.20 (q, J = 319 Hz), 36.40, 28.10,
20.80; IR (film): 1690, 1665, 1430, 1238, 1213, 1140; anal. calcd for
C7 H7 F3 O4 S: C, 34.43; H, 2.89; found C, 34.28; H, 2.90.
General Procedure for Coupling Reactions Catalyzed
by Combined Pd–AgOAc catalyst
Experimental
General
All reactions were run under nitrogen. All melting points were
determined on a Yanaco melting point apparatus and are
uncorrected. IR spectra were recorded on a Nicolet FT-IR 5DX
spectrometer as KBr pellets. The 1 H NMR (300 MHz) and 13 C NMR
(75 MHz) spectra were recorded on a Bruker ACF-300 spectrometer
with TMS as internal reference in CDCl3 solutions. The J-values are
given in hertz. The elemental analyses were performed on a PerkinElmer 240C instrument. Flash chromatography was performed on
silica gel (230–400 mesh) eluting with ethyl acetate–hexane
mixture.
Trifluoromethanesulfonylation of 1,3-Cycloalkdione
Triflic anhydride (0.96 ml, 5.82 mmol) was added by a syringe to
a solution of 1,3-cycloalkdione (5.30 mmol) and pyridine (460 mg,
5.82 mmol) in dry dichloromethane (50 ml) at −78 ◦ C under
nitrogen. The resultant mixture was allowed to reach ambient
temperature and stirred at the same temperature for 24 h. The
solvent was evaporated and the crude product was purified by
flash chromatography eluting with hexanes–EtOAc 3 : 1 to give
the desired products 2a–d.
2-Methyl-3-trifluoromethanesulfonyloxycyclopent-2-enone (2a)
The mixture of 3-oxocycloalk-1-enyl trifluoromethanesulfonate
2a–d (1.0 mmol), terminal alkynes (1.1 mmol), AgOAc (34 mg,
0.2 mmol), Pd[(C6 H5 )3 P]4 (58 mg, 0.05 mmol) and diisopropylethylamine (195 mg, 1.5 mmol) in dry N,N-dimethylacetamide (10 ml)
was stirred at 50 ◦ C for 10 min. TLC showed that the starting material disappeared. The mixture was diluted with dichloromethane
(15 ml) and the solid was removed by filter; the filter was then
concentrated in vacuo and purified by flash chromatography (silica
gel, EtOAc–hexanes, 1 : 10 to 1 : 4) providing a desired products
3–18 (Scheme 1, Table 2).
One-pot synthesis of 3-(alk-1-ynyl)cycloalk-2-enone
by Pd–AgOAc-catalyzed directed from 1,3-cycloalkadione
Triflic anhydride (0.20 ml, 1.20 mmol) was added by a syringe
to a solution of 1,3-cycloalkdione (1.00 mmol) and pyridine
(119 mg, 1.5 mmol) or diisopropylethylamine (195 mg, 1.5 mmol)
in dry dichloromethane (10 ml) at −78 ◦ C under nitrogen. The
resultant mixture was allowed to reach ambient temperature
and stirred at the same temperature for 24 h. The solvent was
evaporated and followed by solvent replacement with dry N,Ndimethylacetamide to a volume of about 12 ml. Then terminal
alkynes (1.1 mmol), AgOAc (34 mg, 0.2 mmol), Pd[(C6 H5 )3 P]4
(58 mg, 0.05 mmol) and diisopropylethylamine (195 mg, 1.5 mmol)
were added respectively, and the resulting mixture was stirred
at 50 ◦ C for 10 min. Following the completion of the reaction
that was monitored by TLC, the mixture was diluted with
dichloromethane (20 ml) and the solid was removed by filter,
the filter was washed with water and brine, dried over anhydride
sodium sulfate, then concentrated under reduced pressure and
purified by flash chromatography (silica gel, EtOAc–hexanes, 1 : 10
to 1 : 4) providing a desired product (Scheme 2, Table 3).
c 2009 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
211
Compound 2a was obtained as a colorless oil, yield 92%; 1 H NMR
(300 MHz, CDCl3 ) 2.93 (m, 2H), 2.67 (m, 2H), 1.78 (t, J = 2.1 Hz
3H); 13 C NMR (75 MHz, CDCl3 ): 203.00, 172.14, 129.84, 118.43 (q,
J = 319 Hz), 34.78, 26.91, 6.48; anal. calcd for C7 H7 F3 O4 S: C, 34.43;
H, 2.89; found C, 34.56; H, 2.66.
Appl. Organometal. Chem. 2010, 24, 208–214
Compound 2c was obtained as a colorless oil, yield 96%; 1 H NMR
(300 MHz, CDCl3 ) δ 5.96 (t, J = 1.5 Hz, 1H), 2.99 (m, 2H), 2.60 (m,
2H); 13 C NMR (75 MHz, CDCl3 ) δ 203.80, 172.90, 128.40, 118.43 (q,
J = 319 Hz), 35.60, 28.63; anal. calcd for C6 H5 F3 O4 S: C, 31.31; H,
2.19; found C, 31.09; H, 2.02.
C. Jiang et al.
3-(3-Hydroxybut-1-ynyl)-2-methylcyclopent-2-enone (3, Table 2, entry 1)
Compound 3 was obtained as a colorless oil, 96% yield; 1 H NMR
(300 MHz, CDCl3 ): 4.82 (m, 1H), 3.23 (s, 1H), 2.64–2.61 (m, 2H),
2.45–2.42 (m, 2H), 1.83 (t, J = 1.8 Hz, 3H), 1.56 (d, J = 6.6 Hz, 3H);
13 C NMR (75 MHz, CDCl ): 209.53, 150.06, 144.88, 108.03, 79.54,
3
58.82, 34.03, 30.22, 24.27, 9.67; IR (film): 3401, 2211, 1697, 1613,
1443, 1339, 1105; anal. calcd for C10 H12 O2 : C, 73.15; H, 7.37; found
C, 73.02; H, 7.18.
3-(4-Hydroxybut-1-ynyl)-2-methylcyclopent-2-enone (4, Table 2, entry 2)
Compound 4 was obtained as a colorless oil, 90% yield; 1 H NMR
(300 MHz, CDCl3 ): 3.84 (q, J = 6.0 Hz, 2H), 2.78 (t, J = 6.3 Hz,
2H), 2.64–2.60 (m, 2H), 2.43–2.39 (m, 2H), 2.30 (t, J = 6.0 Hz,
1H), 1.83 (t, J = 2.1 Hz, 3H); 1 H NMR (300 MHz, CDCl3 + D2 O):
3.84 (q, J = 6.0 Hz, 2H), 2.78 (t, J = 6.3 Hz, 2H), 2.64–2.60 (m,
2H), 2.43–2.39 (m, 2H), 1.83 (t, J = 2.1 Hz, 3H); 13 C NMR (75 MHz,
CDCl3 ): 209.51, 150.89, 144.41, 104.72, 78.41, 60.99, 34.06, 30.51,
24.48, 9.67; IR (film): 3401, 2216, 1684, 1613, 1442, 1344, 1055; anal.
calcd for C10 H12 O2 : C, 73.15; H, 7.37; found C, 73.18; H, 7.08.
2-Methyl-3-phenylethynylcyclopent-2-enone (5, Table 2, entry 3)
Compound 5 was obtained as a white solid, m.p. 85–87 ◦ C
(hexanes–EtOAc), 96% yield; 1 H NMR (300 MHz, CDCl3 ): 7.66 (d,
J = 7.8 Hz, 2H), 7.59 (t, J = 7.8 Hz, 1H), 7.37 (t, J = 7.8 Hz, 2H),
2.73–2.70 (m, 2H), 2.46–2.44 (m, 2H), 1.90 (s, 3H); 13C NMR (75 MHz,
CDCl3 ): 207.8, 160.8, 152.0, 146.7, 132.7(2C), 128.8, 128.4(2C), 104.2,
85.4, 34.2, 29.5, 9.6; IR (film): 2196, 1685, 1611, 1596, 1518, 1438,
1278, 1024, 786; anal. calcd for C14 H12 O: C, 85.68; H, 6.16; found C,
85.56; H, 6.12.
3-[(4-Methoxyphenyl)ethynyl]-2-methylcyclopent-2-enone (6, Table 2, entry 4)
Compound 6 was obtained as a white solid, m.p. 85–87 ◦ C
(hexanes–EtOAc), 92% yield; 1 H NMR (300 MHz, CDCl3 ): 7.47 (d,
J = 9.0 Hz, 2H), 6.90 (d, J = 9.0 Hz, 2H), 3.84 (s, 3H), 2.72–2.70
(m, 2H), 2.47–2.44 (m, 2H), 1.91 (s, 3H); 13 C NMR (75 MHz, CDCl3 ):
208.95, 160.84, 150.50, 143.87, 133.71(2C), 114.40(3C), 106.18,
84.41, 55.49, 34.12, 30.25, 9.81; IR (KBr): 2192, 1683, 1615, 1598,
1510, 1440, 1292, 1251, 1174, 1022, 836; anal. calcd for C15 H14 O2 :
C, 79.62; H, 6.24; found C, 79.56; H, 6.10.
3-(3-Hydroxy-3-methylbut-1-ynyl)-2-methylcyclopent-2-enone
Table 2, entry 5)
(7,
Compound 7 was obtained as a colorless oil, 89% yield; 1 H NMR
(300 MHz, CDCl3 ): 2.85 (s, 1H), 2.63–2.60 (m, 2H), 2.44–2.41 (m,
2H), 1.83 (t, J = 2.1 Hz, 3H), 1.62 (s, 6H); 1 H NMR (300 MHz, CDCl3 +
D2 O): 2.63–2.60 (m, 2H), 2.44–2.41 (m, 2H), 1.83 (t, J = 2.1 Hz,
3H), 1.62 (s, 6H); 13 C NMR (75 MHz, CDCl3 ): 209.31, 150.03, 144.85,
110.70, 77.91, 65.80, 34.03, 31.42(2C), 30.22, 9.68; IR (film): 3402,
2213, 1687, 1615, 1443, 1383, 1338, 1170, 961; anal. calcd for
C11 H14 O2 : C, 74.13; H, 7.92; found C, 74.00; H, 7.78.
3-[(1-Hydroxycyclohexyl)ethynyl]-2-methylcyclopent-2-enone (8, Table 2, entry 6)
212
Compound 8 was obtained as a colorless oil, 86% yield; 1 H NMR
(300 MHz, CDCl3 ): 3.45 (s, 1H), 2.65–2.61 (m, 2H), 2.45–2.42 (m,
www.interscience.wiley.com/journal/aoc
2H), 2.05–1.98 (m, 2H), 1.83 (m, 3H), 1.78–1.53 (m, 7H), 1.31–1.26
(m, 1H); 1 H NMR (300 MHz, CDCl3 + D2 O): 2.65–2.61 (m, 2H),
2.45–2.42 (m, 2H), 2.05–1.98 (m, 2H), 1.83 (m, 3H), 1.78–1.53
(m, 7H), 1.31–1.26 (m, 1H); 13 C NMR (75 MHz, CDCl3 ): 209.26,
150.35, 144.49, 110.26, 79.87, 69.11, 39.74(2C), 33.93, 30.18, 25.11,
23.30(2C), 9.62; IR (film): 3401, 2206, 1686, 1617, 1444, 1383, 1339,
1151, 967; anal. calcd for C14H18 O2 : C, 77.03; H, 8.31; found C, 77.22;
H, 8.55.
2-Methyl-3-(4-methylpent-1-ynyl)cyclopent-2-enone (9, Table 2, entry 7)
Compound 9 was obtained as a colorless oil, 88% yield; 1 H NMR
(300 MHz, CDCl3 ): 2.63–2.60 (m, 2H), 2.41–2.39 (m, 4H), 1.93
(m, 1H), 1.83 (t, J = 2.1 Hz, 3H), 1.04 (d, J = 6.9 Hz, 6H); 13 C NMR
(75 MHz, CDCl3 ): 209.01, 151.26, 143.53, 107.03, 76.78, 33.88, 30.37,
29.11, 27.96, 21.90(2C), 9.43; IR (film): 2215, 1704, 1616, 1465, 1445,
1384, 1323, 1092, 1052; anal. calcd for C12 H16 O: C, 81.77; H, 9.15;
found C, 81.61; H, 9.34.
3-(3-Hydroxybut-1-ynyl)-2-methylcyclohex-2-enone (10, Table 2, entry 8)
Compound 10 was obtained as a colorless oil, 92% yield; 1 H NMR
(300 MHz, CDCl3 ): 4.78 (m, 1H), 3.42 (s, 1H), 2.49–2.42 (m, 4H),
2.00–1.96 (m, 2H), 1.94 (t, J = 1.5 Hz, 3H), 1.53 (d, J = 6.6 Hz, 3H);
13
C NMR (75 MHz, CDCl3 ): 198.88, 139.10, 137.49, 105.55, 82.53,
58.68, 37.84, 31.06, 24.26, 22.60, 13.87; IR (film): 3410, 2209, 1667,
1651, 1596, 1355, 1112, 866; anal. calcd for C11 H14 O2 : C, 74.13; H,
7.92; found C, 74.00; H, 7.64.
3-(4-Hydroxybut-1-ynyl)-2-methylcyclohex-2-enone (11, Table 2, entry 9)
Compound 11 a colorless oil, 93% yield; 1 H NMR (300 MHz, CDCl3 ):
3.81 (d, J = 6.6 Hz, 2H), 3.23 (s, 1H), 2.73 (d, J = 6.6 Hz, 2H),
2.49–2.41 (m, 4H), 1.99–1.95 (m, 2H), 1.93 (t, J = 1.8 Hz, 3H); 13 C
NMR (75 MHz, CDCl3 ): 199.00, 139.20, 138.52, 101.97, 81.27, 60.85,
37.81, 31.36, 24.21, 22.59, 13.78; IR (film): 3400, 2213, 1661, 1651,
1594, 1355, 1307, 1103, 1047; anal. calcd for C11 H14 O2 : C, 74.13; H,
7.92; found C, 74.01; H, 7.70.
3-(3-Hydroxy-3-methylbut-1-ynyl)-2-methylcyclohex-2-enone
Table 2, entry 10)
(12,
Compound 12 was obtained as a colorless oil, 92% yield; 1 H NMR
(300 MHz, CDCl3 ): 2.94 (s, 1H), 2.48–2.42 (m, 4H), 1.99–1.95 (m,
2H), 1.93 (t, J = 1.8 Hz, 3H), 1.60 (s, 6H); 13 C NMR (75 MHz, CDCl3 ):
198.72, 139.14, 137.44, 108.20, 80.99, 65.72, 37.92, 31.41(2C), 31.12,
22.68, 13.90; IR (film): 3412, 2210, 1654, 1594, 1356, 1306, 1165,
962; anal. calcd for C12 H16 O2 : C, 74.97; H, 8.39; found C, 74.73; H,
8.22.
3-[(1-Hydroxycyclohexyl)ethynyl]-2-methylcyclohex-2-enone (13, Table 2, entry 11)
Compound 13 was obtained as a colorless oil, 90% yield; 1 H NMR
(300 MHz, CDCl3 ): 2.69 (s, 1H), 2.50–2.42 (m, 4H), 2.02–1.98 (m,
3H), 1.95 (t, J = 1.8 Hz, 3H), 1.77–1.49 (m, 8H), 1.29–1.25 (m, 1H);
13 C NMR (75 MHz, CDCl ): 198.65, 139.07, 137.51, 107.41, 83.30,
3
69.40, 39.97(2C), 37.96, 31.30, 25.24, 23.47(2C), 22.72, 14.07; IR
(film): 3401, 2202, 1665, 1654, 1595, 1354, 1305, 1073, 966; anal.
calcd for C15 H20 O2 : C, 77.55; H, 8.68; found C, 77.34; H, 8.54.
c 2009 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 208–214
Pd(PPh3 )4 –AgOAc-catalyzed synthesis of conjugated alkynylcycloalkenones
2-Methyl-3-(4-methylpent-1-ynyl)cyclohex-2-enone (14, Table 2, entry 12)
Compound 14 was obtained as a colorless oil, 94% yield; 1 H NMR
(300 MHz, CDCl3 ): 2.46–2.34 (m, 6H), 1.99–1.85 (m, 6H), 1.02 (d,
J = 6.6 Hz, 6H); 13 C NMR (75 MHz, CDCl3 ): 198.55, 138.61, 138.20,
104.57, 81.19, 37.96, 31.62, 29.19, 28.14, 22.75, 22.04(2C), 13.83;
IR (film): 2212, 1667, 1598, 1353, 1305, 1101, 1038; anal. calcd for
C13 H18 O: C, 82.06; H, 9.53; found C, 82.00; H, 9.34.
3-(4-Methoxyphenylethynyl)-2-cyclohexen-1-one (15, Table 2, entry
13)24
Compound 15 was obtained as a white solid, m.p. 95–96 ◦ C
(hexanes–EtOAc), 96% yield; 1 H NMR (300 MHz, CDCl3 ) δ 7.43 (d,
J = 9.0 Hz, 2H), 6.90 (d, J = 9.0 Hz, 2H), 6.28 (t, J = 1.8 Hz, 1H),
3.85 (s, 3H), 2.55 (td, J = 6.9, 1.8 Hz, 2H), 2.46 (t, J = 6.9 Hz, 2H),
2.07 (q, J = 6.9 Hz, 2H); 13 C NMR (75 MHz, CDCl3 ) δ198.90, 160.63,
143.80, 133.66, 131.69(2C), 114.10, 114.24(2C), 100.35, 87.67, 55.34,
37.32, 30.60, 22.64; IR (KBr): 2194, 1692, 1615, 1590, 1540, 1435,
1260, 1231, 902; anal. calcd for C15 H14 O2 : C, 79.62; H, 6.24; found
C, 79.50; H, 6.07.
3-(Phenylethynyl)cyclohex-2-enone (16, Table 2, entry 14)[24]
Compound 16 was obtained as a white solid, m.p. 90–92 ◦ C
(hexanes–EtOAc), 98% yield; 1 H NMR (300 MHz, CDCl3 ) δ7.53 (m,
J = 8.7 Hz, 2H), 7.40 (m, 3H), 6.34 (t, J = 1.8 Hz, 1H), 2.60 (m, 2H),
2.52 (t, J = 6.3 Hz, 2H), 2.10 (m, 2H); 13 C NMR (75 MHz, CDCl3 )
δ199.02, 143.48, 133.02, 132.22, 131.00(2C), 129.10(2C), 122.42,
100.22, 88.64, 38.02, 31.04, 23.20; IR (KBr): 2200, 1689, 1612, 1592,
1550, 1420, 1270, 1236, 889; anal. calcd for C14 H12 O: C, 85.68; H,
6.16; found C, 85.52; H, 6.02.
3-[(1-Hydroxycyclohexyl)ethynyl]cyclohex-2-enone(17,Table 2,entry
15)[25]
Compound 17 was obtained as an oil, 97% yield; 1 H NMR (300 MHz,
CDCl3 ) δ 6.15 (t, J = 1.5 Hz, 1H), 3.18 (s, 1H), 2.43 (m, 4H), 2.01–1.90
(m, 4H), 1.70–1.48 (m, 7H), 1.26 (m, 1H); 13 C NMR (75 MHz, CDCl3 ):
199.58, 144.20, 132.78, 104.68, 83.88, 69.32, 40.04(2C), 37.54, 31.22,
25.52, 23.62(2C), 23.00; IR (film): 3396, 2200, 1663, 1650, 1600, 1350,
1298, 1068, 950; anal. calcd for C14 H18 O2 : C, 77.03; H, 8.31; found
C, 76.92; H, 8.58.
3-(1-Hexynyl)-2-cyclopenten-1-one (18, Table 2, entry 16)[24]
Compound 18 was obtained as a colorless oil, 96% yield; 1 H NMR
(300 MHz, CDCl3 ): δ 6.19 (t, J = 1.8 Hz, 1H), 2.70 (m, 2H), 2.46 (t,
J = 7.2 Hz, 2H), 2.40 (m, 2H), 1.54–1.62 (m, 2H), 1.40–1.47 (m, 2H),
0.94 (t, J = 7.5 Hz, 3H); 13 C NMR (75 MHz, CDCl3 ) δ 208.88, 158.34,
135.20, 107.60, 76.84, 34.55, 32.78, 30.16, 21.90, 19.58, 13.40; IR
(film): 2210, 1696, 1600, 1348, 1360, 1201, 1032; anal. calcd for
C11 H14 O: C, 81.44; H, 8.70; found C, 81.19; H, 8.58.
Acknowledgments
Appl. Organometal. Chem. 2010, 24, 208–214
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This work was supported by the Jiangsu Province Natural Science
Foundation of China (BK2008216).
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