A ruthenium-catalyzed coupling of alkynes with 1,3-diketones

Article abstract of DOI:10.1016/j.jorganchem.2012.05.017

Ruthenium(III) chloride hydrate is a convenient catalyst for the addition of active methylene compounds to aryl alkynes. These reactions are rapid, operationally simple, and high yielding in cases. Most significantly, no precautions are required to exclud

Full text of DOI:10.1016/j.jorganchem.2012.05.017

Journal of Organometallic Chemistry 716 (2012) 6e10
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
A ruthenium-catalyzed coupling of alkynes with 1,3-diketones
*
Megan K. Pennington-Boggio, Brian L. Conley, Travis J. Williams
Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Ruthenium(III) chloride hydrate is a convenient catalyst for the addition of active methylene compounds
to aryl alkynes. These reactions are rapid, operationally simple, and high yielding in cases. Most
significantly, no precautions are required to exclude air or water from the reactions. All reagents are
commercially available at reasonable prices, and the reactions can be conducted in disposable glassware
with minimal solvent.
Received 6 April 2012
Received in revised form
2 May 2012
Accepted 3 May 2012
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Alkynes
Ene reaction
Homogeneous catalysis
Ruthenium
1. Introduction
simultaneously bind and activate both reactive partners. We found,
however, that commercially available ruthenium(III) chloride is
The Conia-Ene reaction (equation 1) is an electrocyclic trans-
formation in which an enolate reacts with a pi system to form a new
CeC bond. Conceptually, a Conia-Ene reaction is similar to alky-
lating a ketone with an alkene or alkyne, with the latter repre-
senting a graceful strategy to “vinylate” adjacent to a carbonyl
group. These reactions occur thermally at high temperature (c.f.
200 ꢀC) [1]. Due to their synthetic utility, several examples of
catalyzed Conia-Ene reactions have been reported.
There are many elegant examples of transition metal catalysts
for the intramolecular Conia-type ene reaction. Some examples
include reactions involving gold [2], palladium/ytterbium [3], and
copper/silver [4] systems. Additionally, some of these methods
have been demonstrated for use in complex [5] and asymmetric
[3,6] applications.
a superior catalyst for this transformation and affords uncharac-
teristically mild intermolecular ene-type coupling reactions for
a variety of terminal alkynes and 1,3-dicarbonyl compounds. Thus
we report here operationally simple, inexpensive, and mild
conditions for the ene-type coupling shown in equation 2.
We report herein the results of our study of commercial
RuCl3$3H2O as a mild and convenient catalyst for coupling of
alkenes with 1,3-diketones. These reactions are high yielding in
cases, and, most notably, are easily executed on the benchtop with
commercially available materials under mild and inexpensive
conditions.
2. Results and discussion
By contrast, there are fewer reports of the analogous intermo-
lecular ene-based coupling reaction (equation 2). Only a few cata-
lytic solutions to this reaction are reported. These are limited
to indium(III) triflate [7], indium(III) trifluoromethylsulfonamide
2.1. Discovery and optimization
Initially we discovered that two ruthenium, boron complexes,
[(py)2BMe2]Ru(cym)Cl and {[(py)2BMe(m
-OH)]Ru(MeCN)3}þ ꢁOTf
[8],
a rhenium-based system [9], and a recently reported
[12] (py ¼ 2-pyridyl, cym ¼ h6-p-cymene), catalyze the ene-type
coupling between phenylacetylene and acetylacetone in modest
yield (Table 1, entries 1, 2). Further experiments revealed that
a variety of ruthenium complexes also affect this transformation
when modified with silver hexafluorophosphate, including [(p-
cymene)RuCl2]2, [(COD)RuCl2]2, [(CO)3RuCl2]2, (Ph3P)3RuCl2, and
[(CO)3RuCl2]2, but notably, RuCl3$3H2O provides the highest yield
(Table 1, entries 3e4 and Table S1). In light of this observation, we
considered that a Ru(acac)3 (acac ¼ acetylacetonate) species,
hydro(trispyrazolyl)borato-ruthenium(II) complex [10].
Whereas the solutions to the intermolecular coupling variant of
this reaction are few, and the existing solutions involve forcing
conditions in cases, we proposed that a dual site ruthenium, boron
catalyst [11] might be a convenient solution because of its ability to
* Corresponding author. Fax: þ1 213 740 6679.
E-mail address: travisw@usc.edu (T.J. Williams).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.05.017

M.K. Pennington-Boggio et al. / Journal of Organometallic Chemistry 716 (2012) 6e10
7
Table 1
Condition Optimization.
R1 OR2
O
O
R1
OR2
O
O
O
OH
5 mol% [Ru]
O
O
5-15 mol% [Ag]
+
Equation 1. A Conia-Ene reaction.
150 µL solvent
0.5-1.0 mmol H2O
75 oC
3 eq.
generated in situ, might be responsible for the reactivity, but we
observe no coupling when Ru(acac)3 is used as the catalyst precursor
(entry 5). This reaction results in the formation of 10% product with
the addition of AgOCOCF3 (entry 6). No reaction was observed in the
absence of ruthenium (entry 7), and the incorporation of a silver salt
seems essential (entry 8). The addition of AgOCOCF3 instead of AgPF6
produces similar results (entries 4 and 9).
The reaction proceeds in a variety of solvents, or with no solvent
at all (Table 1, entries 4, 10e12). We find that the shortest reaction
times and highest yields are obtained using a minimal volume of
diethyl ether. Further, a small amount of water significantly accel-
erates the reaction rate; two equivalents relative to diketone seems
optimal (entries 4, 13e14).
Finally, we observe that although three equivalents of alkyne
relative to the diketone is optimal for reaction time; the reaction
proceeds to completion with only 1.5 equivalents (Table 1, entry
15). The need for excess alkyne arises from a side reaction in which
some alkyne is hydrolyzed to the corresponding methyl ketone, as
is evident from the formation of acetophenone from phenyl-
acetylene as determined by GC/MS and NMR [13]. Electron-rich
alkynes are more susceptible to this side reaction as evident from
NMR quantification, and it appears to be faster in the presence of
AgPF6 as opposed to AgOCOCF3.
It is important to note that while the solvents used in this study
were rigorously anhydrous to allow for the quantification of added
water, we observe that these reactions can be run with benchtop
grade solvent without the need for additional water. For example,
repeating the reaction in Table 1, entry 4 in this way gives an 87%
isolated yield.
Entry [Ru]
[Ag]
H2O Solvent Time Yield
(eq.)
(h) (%)a
1
[(py)2BMe2]Ru(cym)Cl
AgPF6
2
2
2
2
2
2
2
2
2
2
2
2
0
1
2
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
CH2Cl2
None
C6H6
Et2O
Et2O
Et2O
2
2
2
2
2
2
2
2
2
2
2
2
2
2
52
10
82
90
0
10
0
9
92
53
69
45
6
2
{[(py)2BMe(
m
-OH)]Ru(MeCN)3}þ ꢁOTf None
3
4
5
[(CO)3RuCl2]2
RuCl3$3H2O
Ru(acac)3
AgPF6
AgPF6
None
AgOCOCF3
AgPF6
None
AgOCOCF3
AgPF6
AgPF6
AgPF6
AgPF6
AgPF6
AgPF6
6
Ru(acac)3
7
None
8
9
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2O
RuCl3$3H2Ob
10
11
12
13
14
15
84
5.5 92
a
Yield determined by NMR using nitromethane as internal standard.
1.5 eq. Phenylacetylene.
b
2.3. Diketone scope
A number of 1,3-diketone compounds participate efficiently
in coupling reactions under our reaction conditions (Table 3);
b
-ketoesters participate less efficiently (37% yield by NMR, see
Supporting information). The products of reactions with
-ketoesters and 3-substituted 1,3-diketones (entries 2 and 3)
are susceptible to retro-Claisen type decomposition to give
deacylated products with internal alkenes (Scheme 1). This
decomposition is promoted by water, and the use of only 1 equiv-
alent of water relative to diketone is beneficial. These reaction
b
2.2. Alkyne scope
conditions are not useful for the functionalization of
phosphonates, -cyanoketones, -nitroketones, or
rated- -aminoketones.
b
-keto-
b
b
a,b-unsatu-
A number of aryl alkynes afford good yield of ene-type coupling
products under our optimized conditions (Table 2). Our parent case,
entry 1, affords coupling product in 88% isolated yield. Electron-rich
and electron-poor alkynes both participate successfully. However,
the electron-rich alkynes are more reactive towards the alkyne
hydrolysis side reaction. Entries 2 and 3 show that although these
reactions are somewhat slower than the parent, they proceed in
desirable yields. For example, a reaction of 4-ethynyltoluene (3)
proceeds to completion to give 4 in 2 h, and the analogous
1-ethynyl-4-methoxybenzene (5) requires 6 h to convert to 6. In all
cases, reactions of electron-rich alkynes do not reach completion
with only 3 equivalents of alkyne when AgPF6 is utilized. Even with
the use of AgOCOCF3, the corresponding aryl ketones are produced
in quantities detectable by GC/MS. Our conditions are compatible
with ethyne-pendant heterocycles and anilines: entries 6 and 7
show the results of these experiments. These conditions are not
compatible with internal alkynes such as 1-phenylpropyne.
b
In cases where R2 ¼ Ph (entries 4, 5), coupling is high-yielding
and involves a subsequent isomerization of the initially formed
diene to an internal alkene, either stepwise or through a [1,5]
hydride shift (Scheme 2). Entry 4 shows all of the possibilities
available along these lines: 21 is converted to 22 under our
conditions, then 22 converts to isomers 23E and 23Z. By contrast,
when R1 ¼ R2 ¼ Ph (24), a single, isomerized product is collected in
90% yield (entry 5).
2.4. Scalability
We have observed that our reaction conditions can be scaled up
to 1 g with no appreciable loss of yield (Scheme 3). This is indicative
of homogeneous catalysis, and is an essential part of the practicality
of these conditions.
3. Conclusion
O
O
In conclusion, we have developed new catalytic conditions for
the ene-type coupling reaction of alkynes with 1,3-diketones.
These reactions proceed at mild temperature under air and in the
presence of water with relatively low catalyst loading and
minimal solvent waste. While there are other known catalysts for
O
O
R1
R2
R3
+
R1
R2
R3
Equation 2. An intermolecular carbonyl ene reaction.

8
M.K. Pennington-Boggio et al. / Journal of Organometallic Chemistry 716 (2012) 6e10
Table 2
Table 3
Alkyne scope.a
Diketone scope.a
O
OH
5 mol% RuCl3 3H2O
15 mol% AgOCOCF3
O
OH
R2
5 mol% RuCl3 3H2O
15 mol% AgOCOCF3
R1
O
O
O
O
+
+
R1
R2
Et2O, 2 eq. H2O
75 oC
Et2O, 2 eq. H2O
R
75 oC
R
3 eq.
3 eq.
Entry
Substrate
Product
Time (h)
Yield (%)b
78 (83)
Entry
Substrate
Product
Time (h)
Yield (%)b
88 (92)
O
O
OH
O
OH
O
O
1
2
1
2
3
2
3
6
15
1
16
2
O
O
OH
O
O
2c
15
44 (50)
77 (95)
17
19
3
5
7
18
4
O
O
OH
O
O
O
3c
15
50 (54)
82 (96)
MeO
MeO
6
20
O
OH
O
OH
Ph
4
4
92
Ph
Ph
O
O
8
22 +
O
4
4
90 (95)
O
Ph
O
OH
21
Ph
5
2
68 (83)
F3C
F3C
23ZE
9 22:13 23Z: 4 23E
9
10
O
OH
O
O
S
O
O
Ph
Ph
Ph
Ph
6
8
36 (45)
S
5
4
90 (98)
11
24
12
25
O
OH
a
Conditions: 0.5 mmol diketone, 1.5 mmol phenylacetylene, 150 mL diethyl ether,
1.0 mmol H2O.
b
c
Isolated yield. NMR Yield in parentheses.
1 eq. (0.5 mmol) H2O.
7
24
41 (50)
Me2N
Me2N
13
14
a
Conditions: 0.5 mmol acetylacetone, 1.5 mmol alkyne, 150
mL diethyl ether,
O
O
1.0 mmol H2O.
b
Isolated yield. NMR Yield in parentheses.
Nu-
Ph
O
O
R1
+
this reaction, our conditions have advantages over each. The
rhenium catalyst involves significantly greater cost, and though
the cost of both the indium and hydro(trispyrazolyl)borato-
ruthenium(II) catalysts are similar all three must be prepared
Nu
R1
Scheme 1. Retro-Claisen decomposition of 3-substitued 1,3-diketones.

M.K. Pennington-Boggio et al. / Journal of Organometallic Chemistry 716 (2012) 6e10
9
O
Ph
O
Ph
was isolated as a yellow oil in 88% yield. Data are consistent with
a known compound [7a].
R1
O
H
R1
O
4.2.2. 4-Hydroxy-3-(1-(p-tolyl)vinyl)pent-3-en-2-one (4)
Adduct 4 was prepared according to the standard procedure
Scheme 2. Isomerization in cases where R2 ¼ Ph.
using acetylacetone (50.0 mg, 51.1
mL, 0.50 mmol) and p-tolylace-
tylene (3, 174.2 mg, 190.2 L, 1.50 mmol), and stirring for 3 h. 4 was
m
isolated as a yellow oil in 77% yield. Data are consistent with
a known compound [10].
OH
O
5 mol% RuCl3 3H2O
15 mol% AgOCOCF3
O
O
4.2.3. 4-Hydroxy-3-(1-(4-methoxyphenyl)vinyl)pent-3-en-2-one (6)
Adduct 6 was prepared according to the standard procedure
+
Et2O, 2 eq. H2O
using acetylacetone (50.0 mg, 51.1
mL, 0.50 mmol) and 1-ethynyl-4-
75 oC
3 eq.
methoxybenzene (5, 198.2 mg, 194.5
m
L,1.50 mmol), and stirring for
88 %
880 mg
6 h. 6 was isolated as a pale yellow solid in 82% yield. Data are
consistent with a known compound [10].
Scheme 3. Parent reaction on 1 g scale.
4.2.4. 3-(1-([1,10-Biphenyl]-4-yl)vinyl)-4-hydroxypent-3-en-2-one
(8)
Adduct 8 was prepared according to the standard procedure
and conducted under inert atmosphere with rigorously dried
materials. Our system is not limited by this need and is therefore
more practically applicable. Additionally, all catalytic materials are
commercially available and the conditions are applicable to
a diverse variety alkynes and diketones. Thus, these conditions
present a very convenient approach to the “vinylation” of diketone
systems.
using acetylacetone (50.0 mg, 51.1 mL, 0.50 mmol) and 4-ethynyl-
1,10-biphenyl (7, 267.3 mg, 1.50 mmol), and stirring for 4 h. 8 was
isolated as a yellow solid in 92% yield.
M.P. ¼ 75e78 ꢀC; 1H NMR (CDCl3, 400 MHz)
d: 2.024 (s, 6H),
5.264 (s, 1H), 5.966 (s, 1H), 7.362 (tt, J ¼ 1.2 Hz, 7.4 Hz, 1H),
7.429e7.468 (m, 2H), 7.498e7.524 (m, 2H), 7.577e7.615 (m, 4H),
16.659 (s, 1H); 13C NMR (CDCl3, 100 MHz)
d
: 23.8, 118.5, 126.498,
127.1, 127.6, 127.7, 129.0, 138.7, 140.5, 143.2, 191.5; FT-IR (KBr/cmꢁ1
)
4. Materials and methods
v ¼ 3032, 1598, 1487, 1246, 909, 774, 743, 729; HR-MS (þESI):
m/z ¼ 279.1380 g/mol, calc’d. for C19H19O2þ [MH]þ: 279.1380 g/mol.
4.1. Materials and instrumentation
4.2.5. 4-Hydroxy-3-(1-(4-(trifluoromethyl)phenyl)vinyl)pent-3-en-
2-one (10)
Deuterated NMR solvents were purchased from Cambridge
Isotopes Laboratories and were used as received. Reagents were
purchased from SigmaeAldrich Co., Alfa-Aesar, Strem Chemicals,
Inc., Combi-Blocks, Inc., or and TCI America and used as received. 1H,
19F and 13C NMR spectra were obtained on a Varian 400-MR spec-
trometer (400 MHz in 1H, 100 MHz in 13C) or a Varian 500 spec-
trometer (500 MHz in 1H, 125 MHz in 13C). All 1H and 13C chemical
shifts are referenced tothe residual 1H or 13C solvent (relative toTMS)
and reported in units of ppm. Infrared spectra were acquired on
a Bruker OPUS FT-IR spectrometer. Benzene and diethyl ether were
driedby refluxingoversodium andbenzophenone, dichloromethane
was distilled from calcium hydride. Column chromatography was
done in automation using the Teledyne CombiFlash Rf 200 system
using hexane and ethyl acetate. High-resolution ESI mass spectra
were recorded at the University of California, Riverside.
Adduct 10 was prepared according to the standard procedure
using acetylacetone (50.0 mg, 51.1
(trifluoromethyl)benzene (9, 255.2 mg, 244.7
stirring for 2 h. 10 was isolated as a yellow semi-solid in 68% yield.
1H NMR (CDCl3, 500 MHz)
: 1.979 (s, 1H), 5.373 (s, 1H), 6.004 (s,
1H), 7.543 (d, J ¼ 8.2 Hz, 2H), 7.613 (d, J ¼ 8.2 Hz, 2H), 16.668 (s, 1H);
13C NMR (CDCl3, 125 MHz)
23.8, 113.4, 120.8, 124.2 (q,
JCF ¼ 272 Hz),125.9 (q, JCF ¼ 4 Hz),126.3,130.3 (q, JCF ¼ 32 Hz),142.7,
mL, 0.50 mmol) and 1-ethynyl-4-
mL, 1.50 mmol), and
d
d
:
143.3, 191.5; 19F NMR: (CDCl3, 500 MHz, ref. CFCl3)
d
ꢁ63.12; FT-IR
(KBr/cmꢁ1) v ¼ 3094, 2928, 1617, 1326, 1122, 1068, 1015, 853; HR-
þ
MS (þESI): m/z ¼ 271.0946 g/mol, calc’d. for C14H14F3O2 [MH]þ:
271.0940 g/mol.
4-Ethynyl-1,10-biphenyl was synthesized according to literature
procedures [14].
4.2.6. 4-Hydroxy-3-(1-(thiophen-2-yl)vinyl)pent-3-en-2-one (12)
Adduct 12 was prepared according to the standard procedure
using acetylacetone (50.0 mg, 51.1
mL, 0.50 mmol) and 2-
ethynylthiophene (11, 162.2 mg, 146.2
mL, 1.50 mmol), and stirring
4.2. Standard procedure
for 8 h. 12 was isolated as an orange-brown oil 36% yield.
1H NMR (CDCl3, 500 MHz)
: 2.051 (s, 6H), 5.086 (s, 1H), 5.820 (s,
1H), 6.944 (d, J ¼ 3.4 Hz, 1H), 6.976 (m, 1H), 7.227 (d, J ¼ 4.9 Hz, 1H),
d
To a vial containing a magnetic stir bar, ruthenium(III) chloride
hydrate (6.5 mg, 25
(16.6 mg, 75 mol, 15 mol%) is added diethyl ether (150
water (18 L, 1.0 mmol). Diketone (0.50 mmol) and alkyne
mmol, 5 mol%) and silver(I) trifluoroacetate
16.604 (s, 1H); 13C NMR (CDCl3, 125 MHz)
d: 23.5, 113.9, 116.8, 125.3,
m
mL) and
125.9, 128.0, 137.8, 145.5, 191.5; FT-IR (Neat/cmꢁ1) v ¼ 3105, 2925,
1609, 1395, 1247, 993, 915, 702; HR-MS (þESI): m/z ¼ 209.0637 g/
mol, calc’d. for C11H13O2Sþ [MH]þ: 209.0631 g/mol.
m
(1.50 mmol) are added to the vial. The reaction is then stirred at
75 ꢀC for the specified time. Products were isolated by column
chromatography using a hexane/ethyl acetate gradient.
Only 1 eq. of H2O was used for compounds 18 and 20.
4.2.7. 3-(1-(4-(Dimethylamino)phenyl)vinyl)-4-hydroxypent-3-en-
2-one (14)
Adduct 14 was prepared according to the standard procedure
using acetylacetone (50.0 mg, 51.1 mL, 0.50 mmol) and 4-ethynyl-
N,N-dimethylaniline (13, 213.3 mg, 1.50 mmol), and stirring for
24 h. 14 was isolated as a yellow solid in 41% yield.
4.2.1. 4-Hydroxy-3-(1-phenylvinyl)pent-3-en-2-one (2)
Adduct 2 was prepared according to the standard procedure
using acetylacetone (50.0 mg, 51.1
mL, 0.50 mmol) and phenyl-
acetylene (1, 153.2 mg, 164.7 L, 1.50 mmol), and stirring for 2 h. 2
m

10
M.K. Pennington-Boggio et al. / Journal of Organometallic Chemistry 716 (2012) 6e10
M.P. ¼ 38e41 ꢀC; 1H NMR (CDCl3, 500 MHz)
d
: 1.995 (s, 6H),
v ¼ 3058, 1654, 1595, 1449, 1315, 1211, 865, 704; HR-MS (þESI): m/
þ
2.976 (s, 6H), 5.009 (s, 1H), 5.729 (s, 1H), 6.680 (d, J ¼ 9.1 Hz, 2H),
z ¼ 265.1227 g/mol, calc’d. for C18H17O2 [MH]þ: 265.1223 g/mol.
7.319 (d, J ¼ 9.1 Hz, 2H), 16.596 (s, 1H); 13C NMR (CDCl3, 125 MHz)
d:
23.6, 40.51, 112.3, 114.2, 114.4, 127.0, 127.7, 143.1, 150.5, 191.5; FT-IR
4.2.14. (E)-1-Phenyl-2-(1-phenylethylidene)butane-1,3-dione (23E)
(Isolated as a mixture with Z isomer): 1H NMR (CDCl3, 400 MHz)
d: 1.868 (s, 3H), 2.049 (s, 3H), 7.331e7.353 (m, 2 H), 7.409e7.434 (m,
(KBr/cmꢁ1) v ¼ 2919, 2808, 1757, 1606, 1552, 1364, 1171, 897, 820;
þ
HR-MS (þESI): m/z ¼ 246.1492 g/mol, calc’d. for C15H20NO2
[MH]þ: 246.1489 g/mol.
3H), 7.507 (t, J ¼ 8 Hz, 2 H), 7.610 (apparent t, J ¼ 8 Hz,1 H), 8.009 (d,
J ¼ 6.8 Hz, 2H); 13C NMR (CDCl3, 100 MHz)
d: 23.486, 31.005,
127.605, 128.991, 129.061, 129.162, 129.611, 133.955, 136.960,
4.2.8. 5-Hydroxy-4-(1-phenylvinyl)hept-4-en-3-one (16)
140.987, 141.274, 148.266, 196.396, 200.624; FT-IR (Neat/cmꢁ1
)
Adduct 16 was prepared according to the standard procedure
v ¼ 2923, 1656, 1491, 1449, 1355, 1257, 1026, 700; GC/MS: calc’d.:
using heptane-3,5-dione (15, 64.1 mg, 67.8
phenylacetylene (1, 153.2 mg, 164.7 L, 1.50 mmol), and stirring for
2 h. 16 was isolated as a yellow oil in 78% yield.
1H NMR (CDCl3, 400 MHz)
: 1.036 (t, J ¼ 7.29 Hz, 6 H), 2.196 (b,
2H), 2.379 (b, 2H), 5.235 (s, 1H), 5.913 (s, 1H), 7.270e7.460 (m, 5H),
mL, 0.50 mmol) and
264.12 g/mol, found: 264.14 g/mol.
m
4.2.15. 1,3-diphenyl-2-(1-phenylethylidene)propane-1,3-dione (25)
Adduct 25 was prepared according to the standard procedure
using dibenzoylmethane (24, 112.1 mg, 0.50 mmol) and phenyl-
acetylene (1, 153.2 mg, 164.7 mL, 1.50 mmol), and stirring for 4 h. 25
was isolated as a yellow solid in 90% yield. Data are consistent with
a known compound [9].
d
16.710 (s, 1H); 13C NMR (CDCl3, 100 MHz)
d: 9.9, 29.5, 118.4, 126.1,
128.3, 128.8, 140.0, 143.1, 194.6; FT-IR (Neat/cmꢁ1) v ¼ 3084, 2978,
1598, 1492, 1199, 1065, 912, 781; HR-MS (þESI): m/z ¼ 231.1384 g/
þ
mol, calc’d. for C15H19O2 [MH]þ: 231.1380 g/mol.
4.2.9. 3-methyl-3-(1-phenylvinyl)pentane-2,4-dione (18)
Acknowledgements
Adduct 18 was prepared according a modification of the stan-
dard procedure requiring only 1 eq. (9
methylpentane-2,4-dione (17, 57.0 mg, 58.1
phenylacetylene (1, 153.2 mg, 164.7 L, 1.50 mmol), and stirring for
15 h. 18 was isolated as an orange-brown solid in 44% yield. Data are
consistent with a known compound [7a].
m
L) of H2O and using 3-
This work is supported by the University of Southern California,
the Hydrocarbon Research Foundation, and the National Science
Foundation (CHE-1054910). M. K. P.-B. is thankful for the USC
Provost Fellowship and the USC College Doctoral Fellowship. We
thank the NSF (DBI-0821671, CHE-0840366) and NIH (S10-
RR25432) for NMR spectrometers.
mL, 0.50 mmol) and
m
4.2.10. 2-acetyl-2-(1-phenylvinyl)cyclohexanone (20)
Adduct 20 was prepared according to a modification of the
standard procedure requiring only 1 eq. (9
acetylcyclohexanone (19, 70.1 mg, 65.0 L, 0.50 mmol) and phe-
nylacetylene (1,153.2 mg,164.7 L,1.50 mmol), and stirring for 15 h.
m
L) of H2O and using 2-
Appendix A. Supplementary data
m
m
Supplementary data related to this article can be found online at
doi:10.1016/j.jorganchem.2012.05.017.
20 was isolated as a yellow oil in 50% yield. Data are consistent with
a known compound [10].
References
4.2.11. Reaction of 1 and 21 to form adducts 22, 23E, and 23Z
Adducts 22 and 23EZ were prepared according to the standard
procedure using benzoylacetone (21, 81.1 mg, 0.50 mmol) and
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phenylacetylene (1, 153.2 mg, 164.7 mL, 1.50 mmol), and stirring for
4 h. The products were isolated as a yellow oil (22, 23E) or a yellow
solid (23Z). Products were collected in a combined yield of 124 mg
(90%) with the ratio 22:23Z:23E ¼ 9:13:4. Each compound is
separately characterized below. Olefin geometry assignments for
23E and Z were made on the basis on 1D-NOE NMR experiments,
see Supporting information.
(b) W. Li, W. Liu, X. Zhou, C.-H. Lee, Org. Lett. 12 (2010) 548e551;
(c) H.K. Grover, T.P. Lebold, M.A. Kerr, Org. Lett. 13 (2011) 220e223;
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(2011) 5398e5401.
4.2.12. 3-Hydroxy-1-phenyl-2-(1-phenylvinyl)but-2-en-1-one (22)
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50 (2011) 7616e7619.
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13002e13003;
1H NMR (CDCl3, 400 MHz)
d: 2.046 (s, 3H), 5.130 (s, 1H), 5.786 (s,
1H), 7.221 (t, J ¼ 8 Hz, 2 H), 7.279e7.350 (m, 4 H), 7.480 (d, J ¼ 8 Hz,
2 H), 7.579 (d, J ¼ 8 Hz, 2 H),17.351 (s,1H); 13C NMR (CDCl3,100 MHz)
d
: 25.553, 113.333, 119.613, 126.351, 127.884, 128.194, 128.395,
128.891, 130.649, 140.422, 143.705, 183.487; FT-IR (Neat/cmꢁ1
)
(b) M. Nakamura, K. Endo, E. Nakamura, Org. Lett. 7 (2005) 3279e3281;
(c) K. Endo, T. Hatakeyama, M. Nakamura, E. Nakamura, J. Am. Chem. Soc. 129
(2007) 5264e5271.
v ¼ 3027, 1658, 1492, 1355, 1212, 1027, 913, 697; HR-MS (þESI): m/
þ
z ¼ 265.1227 g/mol, calc’d. for C18H17O2 [MH]þ: 265.1223 g/mol.
[8] H. Tsuji, T. Fujimoto, K. Endo, M. Nakamura, E. Nakamura, Org. Lett. 10 (2008)
1219e1221.
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411e425.
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4.2.13. (Z)-1-Phenyl-2-(1-phenylethylidene)butane-1,3-dione (23Z)
M.P. ¼ 44e47 ꢀC; 1H NMR (CDCl3, 400 MHz)
d: 2.274 (s, 3H),
2.476 (s, 3H), 7.089 (s, 5H), 7.242e7.279 (m, 2H), 7.389 (t, J ¼ 6.8 Hz,
1H), 7.704 (d, J ¼ 8.4 Hz, 2 H); 13C NMR (CDCl3, 100 MHz)
d: 22.727,
31.059,127.822,128.310,128.488,128.550,129.363,133.313,137.355,
139.841, 141.366, 151.449, 197.496, 198.781; FT-IR (KBr/cmꢁ1
)