Highly efficient synthesis of allenes from trimethylaluminum reagent and propargyl acetates mediated by a palladium catalyst

Article abstract of DOI:10.1002/ejoc.201403008

A series of propargyl acetates were prepared and used as propargyl electrophiles for coupling reactions with trimethylaluminum. The simple catalytic system of palladium(II) acetate (1 mol-%) and tri(o-tolyl)phosphine (2 mol-%) worked efficiently for a wide variety of aromatic and aliphatic propargyl acetates, producing the substituted allenes in good to excellent yields of up to 94% in tetrahydrofuran. The process was simple and easily performed, and it provides an efficient method for the synthesis of substituted allene derivatives. On the basis of the experimental results, a possible catalytic cycle has been proposed.

Full text of DOI:10.1002/ejoc.201403008

FULL PAPER
DOI: 10.1002/ejoc.201403008
Highly Efficient Synthesis of Allenes from Trimethylaluminum Reagent and
Propargyl Acetates Mediated by a Palladium Catalyst
Qing-Han Li,*[a,b] Jung-Yuan Jeng,[b] and Han-Mou Gau*[b]
Keywords: Homogeneous catalysis / C–C coupling / Palladium / Aluminum / Allenes / Alkynes
A series of propargyl acetates were prepared and used as
propargyl electrophiles for coupling reactions with trimeth-
ylaluminum. The simple catalytic system of palladium(II)
acetate (1 mol-%) and tri(o-tolyl)phosphine (2 mol-%)
worked efficiently for a wide variety of aromatic and ali-
phatic propargyl acetates, producing the substituted allenes
in good to excellent yields of up to 94% in tetrahydrofuran.
The process was simple and easily performed, and it provides
an efficient method for the synthesis of substituted allene de-
rivatives. On the basis of the experimental results, a possible
catalytic cycle has been proposed.
Introduction
Allene-containing molecules are very useful building
blocks that have been widely used in organic synthesis.[1,2]
Allene moieties are also found in natural products,[3] phar-
maceuticals,[3] and molecular materials.[4] Thus, it is very
important to develop efficient reactions for the synthesis of
allenes from simple and readily available organic com-
pounds. In recent years, some methods for the synthesis of
allenes have been developed.[5,6] Protocols for the synthesis
of substituted allenes include elimination reactions of allylic
compounds,[7] isomerization of alkynes,[8] reaction of alde-
hydes with terminal alkynes,[9] and metal-catalyzed reac-
tions of propargylic compounds.[6d,10,11] For metal-cata-
lyzed reactions, the substitution reaction of a propargyl de-
rivative with an organometallic nucleophile may take place
either by an SN2Ј process for the formation of an allene 2,
or by an SN2 process to give an alkyne 3 (Scheme 1).[5f]
As there are two competing possible reaction pathways, the
successful application of such a substitution reaction relies
on the choice of catalyst and/or organometallic reagents to
selectively produce either allene product 2 or alkyne prod-
uct 3.
Scheme 1. SN2Ј and SN2 mechanisms in metal-catalyzed coupling
reactions of propargyl derivatives with organometallic nucleophiles.
using reactive organometallic reagents,[12,13,15] in this paper,
we report a palladium(II)-catalyzed substitution reaction of
propargyl acetates with trimethylaluminum at ambient tem-
perature in short reaction times to give allenes in good
yields.
Results and Discussion
To optimize the reaction conditions, the effects on the
cross-coupling reaction of the palladium source, the phos-
phine ligand, the solvent, the reaction time, the amount of
trimethylaluminum, and the molar ratio of metal to ligand
were investigated using propargyl acetate 1a (Table 1). In a
preliminary experiment, treatment of propargyl acetate 1a
with AlMe3 in the presence of Pd(OAc)2 without ligand in
THF at ambient temperature for 3 h gave both SN2Ј and
SN2 products, that is, 1-methyl-1,3-diphenyl-allene (2a) and
1,3-diphenylbutyne (3a), respectively, with only an 8% con-
version (Table 1, entry 1). The product ratio was about
1:Ͼ99 in favor of alkyne 3a. To our surprise, when we used
the catalytic system of Pd(OAc)2 and P(o-tolyl)3, the reac-
tion proceeded smoothly to give products 2a and 3a with
Ͼ99% conversion, and a ratio of Ͼ99:1 in favor of 2a
Our previous studies have shown that organoaluminum
reagents are highly efficient nucleophiles for cross-coupling
reactions with aromatic halides[12] or benzylic halides,[13]
and that palladium is a good catalytic metal.[14] Continuing
our research into the development of coupling reactions
[a] College of Chemistry and Environmental Protection
Engineering, Southwest University for Nationalities,
Chengdu 610041, China
E-mail: lqhchem@163.com
www.swun.edu.cn
[b] Department of Chemistry, National Chung Hsing University,
Taichung 402, Taiwan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201403008.
7916
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 7916–7923

Highly Efficient Synthesis of Allenes
(Table 1, entry 2). Other palladium sources were then tested
To further study the reactivity and selectivity, other
with P(o-tolyl)3. Although PdCl2, PdCl2(nbd) (nbd = 2,5- parameters of the reaction conditions were investigated.
norbornadiene, Pd2(dba)3 (dba = dibenzylideneacetone), Various solvents were screened under the model reaction
and PdCl2(bipy) (bipy = 2,2Ј-bipyridine) gave excellent conditions, and the results are summarized in Table 2 (en-
product selectivities of 2a/3a of Ͼ99:1, the conversions were tries 1–5). Solvents such as diethyl ether, hexane, toluene,
lower (Table 1, entries 3–6). The steric and electronic effects and CH2Cl2 were unsuitable for this reaction since they
of the phosphine ligand were further examined (Table 1, en- gave lower selectivities. In contrast, when THF was used as
tries 7–10). We found that the ortho-methyl group in the solvent at room temperature, a product ratio of Ͼ99:1 and
P(o-tolyl)3 ligand was crucial for the reactivity and selectiv- Ͼ99% conversion were obtained, and 2a was isolated in
ity. Other phosphine ligands did not give satisfactory re- 75% yield (Table 2, entry 5). The effect of the amount of
sults. When the reaction time was decreased from 3 to 2 h, trimethylaluminum was also investigated. When the AlMe3
the conversion decreased from 99 to 69%, while the selectiv- loading was increased from 0.5 to 0.6 mmol, the isolated
ity remained unchanged (Table 1, entry 11). Thus, the yield of 2a decreased from 75 to 58% (Table 2, entries 5 and
Pd(OAc)2 (1 mol-%)/P(o-tolyl)3 (2 mol-%) combination was 6). Gratifyingly, excellent selectivity (2a/3a Ͼ99%) and a
chosen as the catalyst for further research.
high yield of 2a (93%) were obtained when 0.4 mmol tri-
methylaluminum was used (Table 2, entry 7). Lowering the
trimethylaluminum loading further to 0.3 mmol decreased
the yield of 2a to 88% (Table 2, entry 8). When the ratio
of Pd(OAc)2 and P(o-tolyl)3 was altered to 1:1, the yield
decreased to 86% (Table 2, entry 9). Therefore, the optimal
reaction conditions were Pa(OAc)2 (1 mol-%), P(o-tolyl)3
(2 mol-%), trimethylaluminum (0.4 mmol), propargyl acet-
ate (0.5 mmol) in THF (1 mL) at room temperature for 3 h.
Table 1. Effect of the metal and ligand on the coupling of propargyl
acetates with trimethylaluminum.[a]
Entry
[Pd]
PR3
Conv. [%][b]
2a:3a [%][c]
1
2
3
Pd(OAc)2
Pd(OAc)2
PdCl2
–
8
Ͼ99
51
87
87
4
12
15
9
1: Ͼ99
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
1: Ͼ99
57:43
(o-tolyl)3P
(o-tolyl)3P
(o-tolyl)3P
(o-tolyl)3P
(o-tolyl)3P
dppe[f]
PPh3
PCy3
(p-tolyl)3P
(o-tolyl)3P
Table 3. Pd(OAc)2/P(o-tolyl)3-catalyzed cross-coupling reactions of
propargyl acetates with trimethylaluminum.[a]
4
PdCl2(nbd)
Pd2(dba)3
PdCl2(bipy)
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
5[d]
6
7[e]
8
9
45:55
80:20
Ͼ99:1
10
23
69
Entry
1
2/3
Yield of 2
11[g]
R1
R2
Product [%][b]
[%][c]
[a] 1a/AlMe3/Pd(OAc)2/ligand = 0.5:0.5:0.005:0.01 mmol. [b] Con-
version to 2a + 3a was determined by 1H NMR spectroscopy.
[c] The ratio of 2a/3a was determined by 1H NMR spectroscopy.
[d] Pd2(dba)3 = 0.0025 mmol. [e] Metal/ligand = 0.005:0.005 mmol.
[f] dppe = 1,2-bis(diphenylphosphino)ethane. [g] 2 h.
1
2
3
4
5
6
7
8
9
10
11
12
13
Ph
Ph
Ph
Ph
Ph
1a
1b
1c
1d
1e
1f
1g
1h
1i
2a
2b
2c
2d
2e
2f
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
93
91
87
89
80
90
77
88
89
94
69
88
83
91
90
88
43
58
70
84
87
87
91
91
92
2-MeC6H4
3-MeC6H4
4-MeC6H4
2-MeOC6H4 Ph
2,6-Me2C6H3 Ph
2-ClC6H4
4-ClC6H4
4-CF3C6H4
Ph
Ph
Ph
2g
2h
2i
2j
2k
2l
Table 2. Effect of the solvent and the loading of AlMe3 on the
coupling of propargyl acetates with trimethylaluminum.[a]
4-Me3SiC6H4 Ph
1j
1k
1l
4-vinylC6H4
1-naphthyl
2-naphthyl
benzyl
n-pentyl
cyclohexyl
Ph
Ph
Ph
Ph
Ph
Ph
1m
1n
1o
1p
1q
1r
1s
1t
1u
1v
1w
1x
1y
2m
2n
2o
2p
2q
2r
2s
2t
14[d]
15[d]
16[d]
17[d]
18[d]
19[d,e]
20[d]
21[d]
22[d]
23[d]
24[d]
25[d]
Entry
AlMe3
[mmol]
Solvent
Conv.
[%][b]
2a:3a
Yield of 2a
[%][c]
[%][d]
1
2
3
4
5
6
7
0.5
0.5
0.5
0.5
0.5
0.6
0.4
0.3
0.4
Et2O
86
94:6
–
–
–
phenylethynyl Ph
hexane
toluene
CH2Cl2
THF
THF
THF
Ͼ99
Ͼ99
91
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
23:77
30:70
16:84
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
Ͼ99:1
1-pentenyl
3-pyridine
Ph
Ph
Ph
4-MeC6H4
4-ClC6H4
2-naphthyl
Ph
Ph
–
n-butyl
cyclohexyl
Me3Si
Me3Si
Me3Si
Me3Si
75
58
93
88
86
2u
2v
2w
2x
2y
8
THF
THF
9[e]
[a] 1a/Pd(OAc)2/P(o-tolyl)3 = 0.5:0.005:0.01 mmol. [b] Conversion
[a] 1/AlMe3/Pd(OAc)2/P(o-tolyl)3 = 1.0:0.8:0.01:0.02 mmol. [b] The
1
to 2a + 3a was determined by 1H NMR spectroscopy. [c] The ratio ratio 2a/3a was determined by H NMR spectroscopy. [c] Isolated
2a/3a was determined by 1H NMR spectroscopy. [d] Isolated yield.
[e] Pd(OAc)2/P(o-tolyl)3 = 0.005:0.005 mmol.
yield, two runs average. [d] 60 °C. [e] Pd(OAc)2/P(o-tolyl)3 =
0.02:0.04 mmol.
Eur. J. Org. Chem. 2014, 7916–7923
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Q.-H. Li, J.-Y. Jeng, H.-M. Gau
FULL PAPER
Having established these optimized reaction conditions,
A proposed possible reaction mechanism for the cou-
we set out to test the generality of the reaction. A wide pling reaction, based on known palladium chemistry and
range of propargyl acetates were investigated, and, as the above results on the coupling reaction of propargyl
shown in Table 3, this approach to the cross-coupling reac- acetates with organometallic nucleophiles, is shown in
tions of propargyl acetates with trimethylaluminum was Scheme 2. The first step involves replacement of both of
found to be quite versatile. The corresponding products the acetate ions in Pd(OAc)2 with two methyl groups from
(i.e., 2a–2y) were obtained in moderate to good yields with AlMe3. This is followed by reductive elimination of the two
high selectivities. Aromatic propargyl acetates with either methyl groups and coordination of PR3 to give a Pd0 active
electron-donating or electron-withdrawing groups attached species of Pd(PR3)2 4. Then, the Pd0 is attacked by the tri-
to the benzene rings underwent cross-coupling reactions ple bond of the propargyl acetate to form a π complex 5,
smoothly to give the corresponding products (i.e., 2b–2i) in which is then converted into the corresponding complex 6
good to excellent yields (Table 3, entries 2–9). The coupling or complex 7. Complex 7 could isomerize into complex 6.
reaction of an aromatic propargyl acetate containing a tri- Complex 6 is more stable than complex 7, so complex 6
methylsilyl substituent gave product allene 2j in 94% yield is the major component. Transmetalation of 6 or 7 with
(Table 3, entry 10). Aromatic propargyl acetates containing trimethylaluminum gives methyl(allenyl)palladium(II) inter-
1-naphthyl and 2-naphthyl substituents also produced the mediate 8 or methyl(propargyl)palladium(II) intermediate 9
allene products (i.e., 2l and 2m) with Ͼ99% selectivity in and Me2Al(OAc). Finally complex 8 or 9 undergoes re-
yields of 88 and 83% (Table 3, entries 12 and 13). The cou- ductive elimination to give the desired product of an allene
pling reactions of AlMe3 with aromatic propargyl acetates 2 or an alkyne 3, and regenerates the active Pd0 species for
containing benzyl, n-pentyl, and cyclohexyl groups were the next catalytic cycle.
also explored, and after 3 h at 60 °C, 2n, 2o, and 2p were
formed with Ͼ99% selectivity in yields of 91, 90, and 88%,
respectively (Table 3, entries 14–16). The coupling reactions
Conclusions
of aromatic propargyl acetates containing phenylethynyl
A palladium-catalyzed coupling reaction of propargyl
and 1-pentenyl groups at 60 °C for 3 h gave products 2q and acetates with trimethylaluminum is reported. Coupling re-
2r in moderate 43 and 58% yields (Table 3, entries 17 and actions of aromatic propargyl acetates and aliphatic prop-
18). For an aromatic propargyl acetate containing a pyridyl argyl acetates with trimethylaluminum gave substituted all-
group, the catalytic system was still effective enough to give enes in moderate to good yields with high selectivities. The
2s in 70% yield with Ͼ99% selectivity (Table 3, entry 19).
coupling reaction of an aromatic propargyl acetate contain-
Besides aromatic propargyl acetates, aliphatic propargyl ing a pyridyl group also gave the allene product (i.e., 2s) in
acetates were also found to be suitable substrates for the 70% yield, with a selectivity of up to Ͼ99%. However, the
coupling reaction. When 1-phenyl-hept-2-ynyl acetate (1t) coupling reactions of 1q and 1r, containing an alkynyl or
and 1-phenyl-3-cyclohexylprop-2-ynyl acetate (1u) were an alkenyl substituent, with trimethylaluminum gave the
tested, the desired allene products (i.e., 2t and 2u) were iso- products (i.e., 2q and 2r) in moderate 43 and 58% yields.
lated in good yields (Table 3, entries 20 and 21). Trimethyl- This method represents a useful procedure for the synthesis
silyl-containing aliphatic propargyl acetates were also suc- of allenes. A possible catalytic cycle was proposed to ex-
cessfully used, and the reaction gave the desired allene plain the formation of the allene products. Further studies
products (i.e., 2v–2y) in good to excellent isolated yields into the use of other organoaluminum reagents with this
(Table 3, entries 22–25).
catalyst are currently underway.
Scheme 2. Proposed catalytic cycle for the formation of 2 and 3.
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Eur. J. Org. Chem. 2014, 7916–7923

Highly Efficient Synthesis of Allenes
1-(2-Methoxyphenyl)-3-phenylprop-2-ynyl Acetate (1e): Yellow soild
(3.54g, 84%) H NMR (400 MHz, CDCl3): δ = 7.76 (dd, J = 1.6,
Experimental Section
1
1
General Procedures: H and 13C NMR spectra were obtained with
7.6 Hz, 1 H), 7.50–7.45 (m, 2 H), 7.38–7.33 (m, 1 H), 7.32–7.26 (m,
3 H), 7.04 (s, 1 H), 7.03–7.00 (m, 1 H), 6.90 (dd, J = 1.2, 8.4 Hz,
1 H), 3.85 (s, 3 H), 2.11 (s, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 169.8, 156.7, 131.9, 130.4, 129.0, 128.6, 128.2, 125.2,
122.4, 120.6, 110.8, 86.4, 85.7, 60.9, 55.6, 21.1 ppm. HRMS: calcd.
for C18Hl6O3 280.1099; found 280.1089. C18H16O3 (280.32): calcd.
C 77.12, H 5.75, O 17.12; found C 77.45, H 5.85, O 16.12.
a Varian Mercury 400 spectrometer (1H, 400 MHz; 13C, 100 MHz),
and chemical shifts are reported relative to tetramethylsilane (δ =
0.00 ppm), which was used as an internal reference. Mass spec-
troscopy was carried out with a Finnigan MAT 95 XL Thermo-
Quest Mass Spectrometer. Elemental analysis was carried out with
a Heraeus CHN-O-RAPID instrument. All syntheses and manipu-
lations were carried out under a dry nitrogen atmosphere using
standard Schlenk techniques or in a glovebox. Solvents were dried
by heating at reflux for at least 24 h with P2O5 (dichloromethane)
or sodium/benzophenone (THF, diethyl ether, n-hexane, or tolu-
ene), and were freshly distilled before use. Nickel compounds, phos-
phines, propargyl halides, and trimethylaluminum (2.0 m in tolu-
ene)[26] were obtained commercially, and were used directly for cou-
pling reactions.
1-(2,6-Dimethylphenyl)-3-phenylprop-2-ynyl Acetate (1f): Yellow oil
(3.30g, 79%) 1H NMR (400 MHz, CDCl3): δ = 7.44–7.40 (m, 2 H),
7.32–7.26 (m, 3 H), 7.16–7.11 (m, 1 H), 7.10 (s, 1 H), 7.07–7.03 (m,
2 H), 2.61 (s, 6 H), 2.10 (s, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 169.7, 137.3, 133.6, 131.8, 129.0, 128.6, 128.2, 122.3,
86.2, 85.3, 62.2, 20.9, 20.3 ppm. HRMS: calcd. for C19Hl8O2
278.1307; found 278.1300. C19H18O2 (278.35): calcd. C 81.99, H
6.52, O 11.50; found C 81.69, H 6.28, O 11.72.
General Procedure for the Synthesis of Propargyl Acetates: nBuLi
(1.6 m in n-hexane, 16.5 mmol) was added to a solution of the alk-
yne (16.5 mmol) in anhydrous THF (25 mL) at –78 °C under a
nitrogen atmosphere. The reaction mixture was stirred at that tem-
perature for 20 min, and then at room temperature for 1 h. The
mixture was cooled to –78 °C, then the aldehyde (15.0 mmol) was
added. The reaction mixture was stirred at room temperature for
1 h. Ac2O (30.0 mmol) was added at 0 °C, then the reaction mixture
was warmed to room temperature and stirred for 2 h. The reaction
was quenched with a saturated aqueous NH4Cl solution. The mix-
ture was extracted with diethyl ether (3ϫ 30 mL). The combined
organic layers were washed with brine, dried with magnesium sulf-
ate, filtered, and evaporated to give the crude product. The crude
product was purified by flash column chromatography on silica gel
(hexane or ethyl acetate/hexane) to give the corresponding proparg-
ylic acetate 1.
1-(2-Chlorophenyl)-3-phenylprop-2-ynyl Acetate (1g): Yellow oil
(3.27g, 83%) 1H NMR (400 MHz, CDCl3): δ = 7.87–7.83 (m, 1 H),
7.50–7.46 (m, 2 H), 7.43–7.40 (m, 1 H), 7.37–7.28 (m, 5 H), 6.98
(s, 1 H), 2.14 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ
= 169.5, 134.6, 133.5, 132.0, 130.3, 129.8, 129.5, 128.9, 128.3, 127.2,
122.0, 87.4, 84.6, 63.3, 20.9 ppm. HRMS: calcd. for C17Hl3ClO2
284.0604; found 284.0601. C17H13ClO2 (284.74): calcd. C 71.71, H
4.60, O 11.21; found C 71.25, H 4.51, O 11.08.
1-(4-Chlorophenyl)-3-phenylprop-2-ynyl Acetate (1h): Yellow oil
(3.21g, 81%) 1H NMR (400 MHz, CDCl3): δ = 7.55–7.51 (m, 2 H),
7.49–7.45 (m, 2 H), 7.40–7.36 (m, 2 H), 7.35–7.29 (m, 3 H), 6.66
(s, 1 H), 2.13 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ
= 169.7, 135.7, 134.9, 131.9, 129.2, 128.9, 128.9, 128.3, 121.8, 87.3,
85.0, 65.3, 21.1 ppm. HRMS: calcd. for C17Hl3ClO2 284.0604;
found 284.0607. C17H13ClO2 (284.74): calcd. C 71.71, H 4.60, O
11.21; found C 71.50, H 4.58, O 11.05.
1,3-Diphenylprop-2-ynyl Acetate (1a):[15] Yellow oil (3.18 g, 85 %).
3-Phenyl-1-[4-(trifluoromethyl)phenyl]prop-2-ynyl Acetate (1i): Yel-
1H NMR (400 MHz, CDCl3): δ = 7.62–7.58 (m, 2 H), 7.50–7.46 low oil (4.31g, 90%) H NMR (400 MHz, CDCl3): δ = 7.69 (dd, J
1
(m, 2 H), 7.44–7.37 (m, 3 H), 7.36–7.28 (m, 3 H), 6.70 (s, 1 H), = 8.8, 20.0 Hz, 4 H), 7.50–7.45 (m, 2 H), 7.37–7.29 (m, 3 H), 6.73
2.14 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.7,
137.1, 131.8, 128.9, 128.7, 128.6, 128.2, 127.7, 122.0, 87.0, 85.5,
66.0, 21.0 ppm.
(s, 1 H), 2.15 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ
= 169.6, 141.0, 131.9, 131.0 (q, J = 32.5 Hz), 129.0 128.3, 128.0,
125.7 (q, J = 3.9 Hz), 123.9 (q, J = 271 Hz), 121.7, 87.7, 84.7, 65.3,
20.3 ppm. HRMS: calcd. for C18Hl3F3O2 318.0867; found
318.0862. C180F3Hl3O2 (341.22): calcd. C 67.92, H 4.12, O 10.05;
found C 68.22, H 3.98, O 9.92.
3-Phenyl-1-o-tolylprop-2-ynyl Acetate (1b): Yellow oil (3.50g, 88%)
1H NMR (400 MHz, CDCl3): δ = 7.69–7.66 (m, 1 H), 7.48–7.44
(m, 2 H), 7.33–7.25 (m, 5 H), 7.22–7.19 (m, 1 H), 6.79 (s, 1 H),
2.47 (s, 3 H), 2.14 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3):
δ = 169.8, 136.3, 135.2, 131.9, 130.8, 128.9, 128.7, 128.3, 128.1,
126.3, 122.2, 86.9, 85.4, 64.2, 21.0, 19.1 ppm. HRMS: calcd. for
C18Hl6O2 264.1151; found 264.1154. C18H16O2 (264.32): calcd. C
81.79, H 6.10, O 12.11; found C 81.70, H 6.03, O 12.03.
3-Phenyl-1-[4-(trimethylsilyl)phenyl]prop-2-ynyl Acetate (1j): Yellow
1
oil (1.52g, 59%) H NMR (400 MHz, CDCl3): δ = 7.60–7.54 (m, 4
H), 7.49–7.45 (m, 2 H), 7.34–7.27 (m, 3 H), 6.68 (s, 1 H), 2.12 (s,
3 H), 0.27 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ =
169.8, 141.6, 137.5, 133.7, 131.9, 128.8, 128.2, 127.0, 122.1, 87.0,
85.5, 66.1, 21.1, –1.2 ppm. HRMS: calcd. for C20H22O2Si 322.1389;
found 322.13790. C20H22O2Si (322.48): calcd. C 74.49, H 6.88, O
9.92; found C 74.20, H 7.08, O 10.24.
3-Phenyl-1-m-tolylprop-2-ynyl Acetate (1c): Yellow oil (3.27g, 83%)
1H NMR (400 MHz, CDCl3): δ = 7.50–7.45 (m, 2 H), 7.42–7.38
(m, 2 H), 7.34–7.27 (m, 4 H), 7.18 (d, J = 7.6 Hz, 1 H), 6.66 (s, 1
H), 2.39 (s, 3 H), 2.13 (s, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 169.9, 138.5, 137.1, 131.9, 129.8, 128.8, 128.6, 128.5,
128.3, 124.9, 122.2, 86.9, 85.7, 66.1, 21.4, 21.2 ppm. HRMS: calcd.
for C18Hl6O2 264.1150; found 264.1144. C18H16O2 (264.32): calcd.
C 81.79, H 6.10, O 12.11; found C 81.41, H 6.03, O 11.93.
3-Phenyl-1-(4-vinylphenyl)prop-2-ynyl Acetate (1k): Yellow oil
(3.37g, 81%) 1H NMR (400 MHz, CDCl3): δ = 7.56 (d, J = 8.4 Hz,
2 H), 7.51–7.42 (m, 4 H), 7.33–7.27 (m, 3 H), 6.72 (dd, J = 10.8,
17.2 Hz, 1 H), 6.68 (s, 1 H), 5.78 (d, J = 17.6 Hz, 1 H), 5.28 (d, J
= 11.2 Hz, 1 H), 2.12 (s, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 169.8, 138.3, 136.5, 136.1, 132.0, 131.9, 128.8, 128.2,
128.1, 128.0, 126.4, 122.0, 114.8, 87.0, 85.5, 65.8, 21.1 ppm.
HRMS: calcd. for C19Hl6O2 276.1150; found 276.1142. C19H16O2
(276.33): calcd. C 82.58, H 5.84, O 11.58; found C 81.60, H 5.52,
O 10.33.
3-Phenyl-1-p-tolylprop-2-ynyl Acetate (1d):[16] Yellow oil (2.93 g,
1
74%) H NMR (400 MHz, CDCl3): δ = 7.52–7.44 (m, 4 H), 7.36–
7.28 (m, 3 H), 7.24–7.20 (m, 2 H), 6.66 (s, 1 H), 2.37 (s, 3 H), 2.12
(s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.9, 138.9,
134.2, 131.8, 129.3, 128.7, 128.2, 127.8, 122.1, 86.8, 85.7, 65.9, 21.2,
21.1 ppm.
1-(Naphthalen-1-yl)-3-phenylprop-2-ynyl Acetate (1l): Yellow solid
(3.56g, 79%) 1H NMR (400 MHz, CDCl3): δ = 8.28 (d, J = 8.0 Hz,
Eur. J. Org. Chem. 2014, 7916–7923
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7919

Q.-H. Li, J.-Y. Jeng, H.-M. Gau
FULL PAPER
1 H), 7.92–7.87 (m, 3 H), 7.62–7.44 (m, 5 H), 7.34–7.28 (m, 4 H),
2.15 (s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.9,
134.0, 132.4, 131.9, 130.6, 130.0, 128.9, 128.8, 128.3, 126.69,
126.66, 126.0, 125.2, 123.8, 122.2, 87.6, 85.7, 64.6, 21.1 ppm.
HRMS: calcd. for C21Hl6O2 300.1150; found 300.1142. C21H16O2
(300.36): calcd. C 83.98, H 5.37, O 10.65; found C 84.15, H 5.29,
O 10.29.
251.0942. C16H13NO2 (251.28): calcd. N 5.57, C 76.48, H 5.21, O
12.73; found N 5.64, C 76.33, H 5.57, O 12.35.
1-Phenylhept-2-ynyl Acetate (1t):[19] Colorless oil (2.72g, 79%) 1H
NMR (400 MHz, CDCl3): δ = 7.54–7.50 (m, 2 H), 7.40–7.32 (m, 3
H), 6.46 (t, J = 1.6 Hz, 1 H), 2.27 (dt, J = 2.0, 6.8 Hz, 2 H), 2.09
(s, 3 H), 1.57–1.48 (m, 2 H), 1.45–1.37 (m, 2 H), 0.91 (t, J = 7.2 Hz,
3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.9, 137.6,
128.7, 128.5, 127.7, 88.3, 76.6, 66.0, 30.4, 21.9, 21.2, 18.5,
13.5 ppm.
1-(Naphthalen-2-yl)-3-phenylprop-2-ynyl Acetate (1m): Yellow soild
1
(3.64g, 81%) H NMR (400 MHz, CDCl3): δ = 8.05 (s, 1 H), 7.90–
7.82 (m, 3 H), 7.70 (dd, J = 1.6, 8.4 Hz, 1 H), 7.53–7.47 (m, 4 H),
7.34–7.28 (m, 3 H), 6.87 (s, 1 H), 2.15 (s, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 169.9, 134.4, 133.4, 133.0, 131.9, 128.8,
128.7, 128.3, 128.2, 127.7, 127.2, 126.6, 126.4, 125.1, 122.0, 87.3,
85.6, 66.3, 21.2 ppm. HRMS: calcd. for C21Hl6O2 300.1151; found
300.1156. C21H16O2 (300.36): calcd. C 83.98, H 5.37, O 10.65;
found C 83.70, H 5.46, O 10.72.
3-Cyclohexyl-1-phenylprop-2-ynyl Acetate (1u):[20] Colorless oil
(3.05g, 82%) 1H NMR (400 MHz, CDCl3): δ = 7.55–7.51 (m, 2 H),
7.40–7.33 (m, 3 H), 6.49 (d, J = 1.6 Hz, 1 H), 2.50–2.42 (m, 1 H),
2.09 (s, 3 H), 1.86–1.77 (m, 2 H), 1.74–1.65 (m, 2 H), 1.56–1.42 (m,
3 H), 1.37–1.24 (m, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3):
δ = 169.9, 137.7, 128.7, 128.5, 127.7, 92.3, 66.0, 32.32, 32.30, 29.0,
25.8, 24.8, 21.2 ppm.
1,4-Diphenylbut-3-yn-2-yl Acetate (1n):[17] Yellow oil (2.07g, 52%)
1H NMR (400 MHz, CDCl3): δ = 7.41–7.36 (m, 2 H), 7.34–7.23
(m, 8 H), 5.78 (t, J = 6.4 Hz, 1 H), 3.16 (d, J = 6.4 Hz, 2 H), 2.07
(s, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.8, 135.9,
131.8, 129.7, 128.6, 128.3, 128.2, 127.0, 122.1, 86.1, 86.0, 65.0, 41.2,
21.0 ppm.
1-Phenyl-3-(trimethylsilyl)prop-2-ynyl Acetate (1v):[21] Colorless oil
(3.05g, 82%) 1H NMR (400 MHz, CDCl3): δ = 7.54–7.50 (m, 2 H),
7.41–7.33 (m, 3 H), 6.49 (s, 1 H), 2.10 (s, 3 H), 0.20 (m, 9 H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ = 169.7, 136.9, 128.9, 128.6,
127.8, 101.2, 92.4, 65.8, 21.1, –0.3 ppm.
1-p-Tolyl-3-(trimethylsilyl)prop-2-ynyl Acetate (1w): Colorless oil
(3.14g, 80%) 1H NMR (400 MHz, CDCl3): δ = 7.42 (d, J = 8.0 Hz,
2 H), 7.19 (d, J = 8.0 Hz, 2 H), 6.45 (s, 1 H), 2.36 (s, 3 H), 2.08 (s,
3 H), 0.19 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ =
169.7, 138.9, 134.0, 129.3, 127.8, 101.4, 92.1, 65.7, 21.21, 21.17,
–0.3 ppm. HRMS: calcd. for C15H20SiO2 260.1233; found
260.1239. C15H20O2Si (260.41): calcd. C 69.19, H 7.74, O 12.29;
found C 69.37, H 8.04, O 12.15.
1-Phenyloct-1-yn-3-yl Acetate (1o): Colorless oil (3.13g, 86%) 1H
NMR (400 MHz, CDCl3): δ = 7.47–7.42 (m, 2 H), 7.34–7.27 (m, 3
H), 5.60 (t, J = 6.8 Hz, 1 H), 2.11 (s, 3 H), 1.88–1.82 (m, 2 H),
1.54–1.46 (m, 2 H), 1.38–1.31 (m, 4 H), 0.94–0.88 (m, 3 H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ = 170.1, 131.9, 128.5, 128.2,
122.3, 86.6, 85.1, 64.6, 34.8, 31.3, 24.7, 22.5, 21.1, 14.0 ppm.
HRMS: calcd. for C15H20O2 244.1469; found 244.1466. C16H20O2
(244.33): calcd. C 78.65, H 8.25, O 13.10; found C 78.69, H 8.23,
O 12.92.
1-(4-Chlorophenyl)-3-(trimethylsilyl)prop-2-ynyl Acetate (1x): Col-
1
orless oil ( 3.03g, 72%) H NMR (400 MHz, CDCl3): δ = 7.46 (d,
1-Cyclohexyl-3-phenylprop-2-ynyl Acetate (1p):[18] Yellow oil (2.32g,
J = 8.0 Hz, 2 H), 7.35 (d, J = 8.4 Hz, 2 H), 6.44 (s, 1 H), 2.10 (s,
3 H), 0.20 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ =
169.6, 135.5, 134.8, 129.2, 128.8, 100.7, 92.8, 65.1, 21.1, –0.3 ppm.
HRMS: calcd. for C14H17SiClO2 280.0686; found 280.0684.
C14H17ClO2Si (280.83): calcd. C 59.88, H 6.10, O 11.39; found C
59.72, H 6.05, O 11.30.
1
60%) H NMR (400 MHz, CDCl3): δ = 7.46–7.42 (m, 2 H), 7.34–
7.27 (m, 3 H), 5.45 (d, J = 6.4 Hz, 1 H), 2.12 (s, 3 H), 1.96–1.65
(m, 6 H), 1.34–1.11 (m, 5 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 170.1, 131.9, 128.5, 128.2, 122.4, 85.8, 85.6, 68.7, 42.0,
28.6, 28.1, 26.2, 25.75, 25.69, 21.0 ppm.
1-(Naphthalen-2-yl)-3-(trimethylsilyl)prop-2-ynyl Acetate (1y):[22]
White soild ( 3.63g, 82%) H NMR (400 MHz, CDCl3): δ = 7.99
(s, 1 H), 7.88–7.80 (m, 3 H), 7.64–7.60 (m, 1 H), 7.52–7.46 (m, 2
H), 6.65 (s, 1 H), 2.11 (s, 3 H), 0.21 (s, 9 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 169.7, 134.2, 133.4, 132.9, 128.5, 128.3,
127.6, 127.3, 126.6, 126.4, 125.1, 101.3, 92.7, 66.0, 21.1, –0.3 ppm.
1,5-Diphenylpenta-1,4-diyn-3-yl Acetate (1q): Yellow oil (1.97g,
48%) H NMR (400 MHz, CDCl3): δ = 7.52–7.48 (m, 4 H), 7.37–
1
1
7.29 (m, 6 H), 6.54 (s, 1 H), 2.18 (s, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 169.2, 132.0, 129.0, 128.3, 121.5, 82.2, 82.7,
54.1, 20.9 ppm. HRMS: calcd. for C19H14O2 274.0994; found
274.0998.
(E)-1-Phenyloct-4-en-1-yn-3-yl Acetate (1r): Yellow oil (3.28g, 90%)
1H NMR (400 MHz, CDCl3): δ = 7.49–7.44 (m, 2 H), 7.36–7.28
(m, 3 H), 6.10–6.08 (m, 1 H), 6.07–6.02 (m, 1 H), 5.63 (ddt, J =
1.6, 6.4, 15.6 Hz, 1 H), 2.12 (s, 3 H), 2.08 (dt, J = 7.6, 7.6 Hz, 2
H), 1.45 (tq, J = 7.6, 7.6 Hz, 2 H), 0.92 (t, J = 7.6 Hz, 3 H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ = 169.8, 136.6, 131.9, 128.6,
128.2, 125.0, 122.1, 86.4, 85.1, 64.8, 34.0, 21.8, 21.2, 13.6 ppm.
HRMS: calcd. for C16H18O2 242.1307; found 242.1304. C16H18O2
(242.32): calcd. C 79.31, H 7.49, O 13.21; found C 79.21, H 7.43,
O 13.07.
General Procedure for the Coupling Reaction of Propargyl Acetates
with Trimethylaluminum: Pd(OAc)2 (2.6 mg, 0.010 mmol) and tri-
(o-tolyl)phosphine (11.2 mg, 0.0200 mmol) were mixed in a reac-
tion vessel under a dry nitrogen atmosphere. A solution of trimeth-
ylaluminum (0.4 mL, 0.8 mmol) in THF (2 mL) was slowly added
by syringe, followed by the addition of propargyl acetate
(1.00 mmol). The resulting solution was stirred at room tempera-
ture or 60 °C for 3 h. After the reaction was complete, the mixture
was diluted with saturated ammonium chloride solution (5 mL),
and extracted with ethyl acetate (3ϫ 15 mL). The combined or-
ganic layers were dried with anhydrous Na2SO4, filtered, and evap-
orated in vacuo. The residue was subjected to flash column
chromatography on silica gel (hexane or ethyl acetate/hexane) to
give allene products 2.
3-Phenyl-1-(pyridin-3-yl)prop-2-ynyl Acetate (1s): Yellow oil (2.31g,
1
61%) H NMR (400 MHz, CDCl3): δ = 8.84 (d, J = 2.4 Hz, 1 H),
8.64–8.62 (dd, J = 1.6, 4.8 Hz, 1 H), 7.93 (dt, J = 1.6, 8.0 Hz, 1
H), 7.51–7.46 (m, 2 H), 7.38–7.30 (m, 4 H), 6.72 (s, 1 H), 2.15 (s,
3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 169.6, 150.1, 1,3-Diphenylbuta-1,2-diene (2a):[23] Yellow oil (0.190 g, 93%). 1H
149.2, 135.4, 133.0, 131.9, 129.1, 128.3, 123.5, 121.6, 87.8, 84.4,
64.0, 21.0 ppm. HRMS: calcd. for C16H13NO2 251.0946; found
NMR (400 MHz, CDCl3): δ = 7.48–7.44 (m, 2 H), 7.36–7.28 (m, 6
H), 7.25–7.20 (m, 2 H), 6.48 (q, J = 2.8 Hz, 1 H), 2.23 (d, J =
7920
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Eur. J. Org. Chem. 2014, 7916–7923

Highly Efficient Synthesis of Allenes
2.8 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 206.8, 1-(4-Trimethylsilylphenyl)-3-phenylbuta-1,2-diene (2j): Yellow oil
1
136.3, 134.5, 128.7, 128.5, 127.03, 127.02, 126.9, 125.8, 104.5, 96.6,
16.8 ppm.
(0.262 g, 94%). H NMR (400 MHz, CDCl3): δ = 7.49–7.43 (m, 4
H), 7.35–7.30 (m, 4 H), 7.22 (t, J = 7.2 Hz, 1 H), 6.47 (q, J =
2.8 Hz, 1 H), 2.22 (d, J = 2.8 Hz, 3 H), 0.25 (s, 9 H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ = 207.1, 139.2, 136.2, 135.0, 133.7,
128.4, 127.0, 126.2, 125.8, 104.5, 96.6, 16.1, –1.1 ppm.
1-(2-Methylphenyl)-3-pethylbuta-1,2-diene (2b):[24] Yellow oil
(0.199 g, 91%). 1H NMR (400 MHz, CDCl3): δ = 7.46 (d, J =
7.6 Hz, 2 H), 7.38–7.30 (m, 3 H), 7.24–7.20 (m, 1 H), 7.18–7.10 (m,
3 H), 6.66 (q, J = 3.2 Hz, 1 H), 2.41 (s, 3 H), 2.22 (d, J = 3.2 Hz,
3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 207.5, 136.6,
135.3, 132.7, 130.7, 128.4, 127.5, 126.95, 126.90, 126.2, 125.8,
103.5, 94.1, 20.0, 16.9 ppm.
1-(4-Vinylphenyl)-3-phenylbuta-1,2-diene (2k): Yellow oil (0.160 g,
69%). H NMR (400 MHz, CDCl3): δ = 7.47–7.43 (m, 2 H), 7.37–
1
7.27 (m, 6 H), 7.25–7.20 (m, 1 H), 6.69 (dd, J = 11.2, 17.6 Hz, 1
H), 6.47 (q, J = 2.8 Hz, 1 H), 5.72 (dd, J = 0.8, 17.6 Hz, 1 H), 5.21
(dd, J = 0.8, 10.8 Hz, 1 H), 2.23 (d, J = 3.2 Hz, 3 H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ = 207.1, 136.5, 136.4, 136.3, 134.0,
128.4, 127.04, 127.00, 126.6, 125.8, 113.5, 104.6, 96.4, 16.7 ppm.
HRMS: calcd. for C18H16 232.1252; found 232.1255.
1-(3-Methylphenyl)-3-phenylbuta-1,2-diene (2c): Yellow oil (0.190 g,
1
87%). H NMR (400 MHz, CDCl3): δ = 7.46 (d, J = 8.0 Hz, 2 H),
7.33 (t, J = 7.2 Hz, 2 H), 7.21 (dd, J = 8.4, 16.4 Hz, 2 H), 7.15–
7.05 (m, 2 H), 7.03 (d, J = 7.2 Hz, 1 H), 6.45 (q, J = 2.8 Hz, 1 H),
2.32 (s, 3 H), 2.22 (d, J = 2.8 Hz, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 206.8, 138.3, 136.4, 134.4, 128.6, 128.4,
127.9, 127.5, 127.0, 125.8, 124.1, 104.3, 96.6, 21.4, 16.8 ppm.
HRMS: calcd. for C17H16 220.1252; found 220.1258.
1-(Naphthylen-1-yl)-3-phenylbuta-1,2-diene (2l):[25] Yellow solid
(0.224 g, 88%). 1H NMR (400 MHz, CDCl3): δ = 8.30 (d, J =
7.6 Hz, 1 H), 7.89–7.85 (m, 1 H), 7.75 (d, J = 8.4 Hz, 1 H), 7.58
(d, J = 6.8 Hz, 1 H), 7.55–7.47 (m, 4 H), 7.43 (t, J = 7.6 Hz, 1 H),
7.35 (t, J = 7.6 Hz, 2 H), 7.24 (t, J = 7.6 Hz, 1 H), 7.18 (q, J =
3.2 Hz, 1 H), 2.30 (d, J = 2.8 Hz, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 208.2, 136.4, 134.0, 130.9, 130.6, 128.7,
128.5, 127.6, 127.0, 126.2, 125.9, 125.73, 125.68, 125.6, 122.7,
103.4, 93.4, 16.9 ppm.
1-(4-Methylphenyl)-3-phenylbuta-1,2-diene (2d):[6n] Yellow oil
1
(0.196 g, 89%). H NMR (400 MHz, CDCl3): δ = 7.47–7.43 (m, 2
H), 7.34–7.29 (m, 2 H), 7.25–7.20 (m, 3 H), 7.12 (d, J = 8.0 Hz, 2
H), 6.45 (q, J = 2.8 Hz, 1 H), 2.33 (s, 3 H), 2.22 (d, J = 2.8 Hz, 3
H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 206.5, 136.8,
136.5, 131.5, 129.4, 128.4, 126.9, 126.8, 125.8, 104.4, 96.4, 21.2,
16.8 ppm.
1-(Naphthylen-2-yl)-3-phenylbuta-1,2-diene (2m):[6n] Yellow solid
1
(0.213 g, 83%). H NMR (400 MHz, CDCl3): δ = 7.80–7.71 (m, 4
H), 7.52–7.48 (m, 3 H), 7.48–7.39 (m, 2 H), 7.37–7.31 (m, 2 H),
7.26–7.23 (m, 1 H), 6.65 (q, J = 2.8 Hz, 1 H), 2.28 (d, J = 2.8 Hz)
ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 207.4, 136.3, 133.7,
132.7, 132.0, 128.5, 128.3, 127.69, 127.68, 127.1, 126.2, 125.9,
125.63, 125.62, 124.8, 104.7, 96.9, 16.8 ppm.
1-(2-Methoxyphenyl)-3-phenylbuta-1,2-diene (2g): Yellow oil
(0.190 g, 80%). H NMR (400 MHz, CDCl3): δ = 7.48–7.35 (m, 2
1
H), 7.38–7.29 (m, 3 H), 7.23–7.16 (m, 2 H), 6.91–6.85 (m, 3 H),
3.87 (s, 3 H), 2.21 (d, J = 3.2 Hz, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 207.2, 156.1, 136.6, 128.4, 128.1, 127.8,
126.8, 125.7, 122.8, 120.7, 111.0, 103.7, 90.5, 55.6, 16.8 ppm.
HRMS: calcd. for C17H16O 236.1201; found 236.1202.
1,4-Diphenylpenta-2,3-diene (2n): Yellow oil (0.201 g, 91%). 1H
NMR (400 MHz, CDCl3): δ = 7.42–7.38 (m, 2 H), 7.36–7.27 (m, 6
H), 7.24–7.17 (m, 2 H), 5.63–5.56 (m, 1 H), 3.45 (d, J = 7.2 Hz, 2
H), 2.10 (d, J = 2.8 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 204.7, 140.4, 137.3, 128.5, 128.4, 128.2, 126.5, 126.2,
125.7, 100.8, 92.4, 35.8, 17.1 ppm. HRMS: calcd. for C17Hl6
220.1252; found 220.1247.
1-(1,3-Dimethylphenyl)-3-phenylbuta-1,2-diene (2f): Yellow oil
(0.212 g, 90%). 1H NMR (400 MHz, CDCl3): δ = 7.45 (d, J =
8.0 Hz, 2 H), 7.33 (t, J = 7.2 Hz, 2 H), 7.20 (t, J = 7.6 Hz, 1 H),
7.04 (s, 3 H), 6.66 (q, J = 2.4 Hz, 1 H), 2.39 (s, 6 H), 2.20 (d, J =
2.4 Hz) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 207.4, 137.0,
136.5, 131.7, 128.33, 128.31, 126.62, 126.56, 125.9, 100.8, 92.0,
21.4, 17.2 ppm. HRMS: calcd. for C18H18 234.1409; found
234.1414.
2-Phenyl-nona-2,3-diene (2o): Colorless oil (0.180 g, 90%). 1H
NMR (400 MHz, CDCl3): δ = 7.43–7.38 (m, 2 H), 7.34–7.28 (m, 2
H), 7.20–7.16 (m, 1 H), 5.47–5.40 (m, 1 H), 2.13–2.07 (m, 2 H),
2.09 (d, J = 2.8 Hz, 3 H), 1.51–1.43 (m, 2 H), 1.38–1.26 (m, 4 H),
0.88 (t, J = 7.2 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3):
δ = 204.1, 137.8, 128.2, 126.2, 125.6, 100.2, 93.1, 31.4, 28.93, 28.88,
22.5, 17.2, 14.1 ppm. HRMS: calcd. for C15H20 200.1565; found
200.1564.
1-(2-Chlorophneyl)-3-phenylbuta-1,2-diene (2g): Yellow oil (0.186 g,
1
77%). H NMR (400 MHz, CDCl3): δ = 7.48–7.42 (m, 3 H), 7.38–
7.31 (m, 3 H), 7.27–7.22 (m, 1 H), 7.19–7.10 (m, 2 H), 6.92 (q, J
= 2.4 Hz, 1 H), 2.24 (d, J = 2.8 Hz, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 207.8, 135.9, 132.2, 129.8, 128.5, 128.4,
128.0, 127.2, 126.8, 125.8, 104.8, 93.0, 16.6 ppm. HRMS: calcd. for
C16H13Cl 240.0706; found 240.0698.
1-Cyclohexyl-3-phenylbuta-2,3-diene (2p): Colorless oil (0.186 g,
1
88%). H NMR (400 MHz, CDCl3): δ = 7.44–7.40 (m, 2 H), 7.34–
1-(4-Chlorophneyl)-3-phenylbuta-1,2-diene (2h):[6n] Yellow oil
7.28 (m, 2 H), 7.20–7.16 (m, 1 H), 5.46–5.41 (m, 1 H), 2.15–2.06
(m, 1 H), 2.09 (d, J = 2.8 Hz, 3 H), 1.86–1.79 (m, 2 H), 1.76–1.68
(m, 2 H), 1.67–1.60 (m, 1 H), 1.35–1.11 (m, 5 H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ = 203.0, 137.7, 128.2, 126.2, 125.4,
101.0, 99.1, 37.9, 33.23, 33.18, 26.14, 26.05, 17.3 ppm. HRMS:
calcd. for C16H20 212.1565; found 212.1568.
1
(0.211 g, 88%). H NMR (400 MHz, CDCl3): δ = 7.46–7.43 (m, 2
H), 7.36–7.31 (m, 2 H), 7.29–7.21 (m, 5 H), 6.43 (q, J = 2.8 Hz, 1
H), 2.23 (d, J = 2.8 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 206.9, 136.0, 133.1, 132.6, 128.8, 128.5, 128.0, 127.2,
125.8, 105.0, 95.7, 16.7 ppm.
1-(4-Trifluoromethylphenyl)-3-phenylbuta-1,2-diene (2i):[6n] Yellow 1,5-Dipheneylhexa-3,4-dien-1-yne (2q): Yellow oil (0.098 g, 43%).
oil (0.244 g, 89%). 1H NMR (400 MHz, CDCl3): δ = 7.57–7.53 (m, 1H NMR (400 MHz, CDCl3): δ = 7.46–7.41 (m, 4 H), 7.38–7.33
2 H), 7.46–7.40 (m, 4 H), 7.37–7.32 (m, 2 H), 7.27–7.22 (m, 1 H),
6.50 (q, J = 3.2 Hz, 1 H), 2.25 (d, J = 3.2 Hz, 3 H) ppm. 13C{1H}
NMR (100 MHz, CDCl3): δ = 207.8, 138.5, 135.7, 128.9 (q, J =
32.5 Hz), 128.6, 127.4, 127.0, 125.9, 125.6 (q, J = 3.9 Hz), 124.2 (q,
J = 270 Hz), 105.3, 95.8, 16.6 ppm.
(m, 2 H), 7.32–7.23 (m, 4 H), 5.93 (q, J = 2.8 Hz, 1 H), 2.19 (d, J
= 2.8 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 213.9,
135.4, 131.5, 128.5, 128.2, 128.1, 127.4, 126.2, 123.4, 103.1, 89.9,
82.2, 77.9, 16.7 ppm. HRMS: calcd. for C18H14 230.1095; found
230.1089.
Eur. J. Org. Chem. 2014, 7916–7923
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7921

Q.-H. Li, J.-Y. Jeng, H.-M. Gau
FULL PAPER
(E)-2-Phenyl-nona-2,3,5-triene (2r): Colorless oil (0.115 g, 58%). 1H
NMR (400 MHz, CDCl3): δ = 7.40 (d, J = 7.6 Hz, 2 H), 7.31 (t, J
= 7.6 Hz, 2 H), 7.20 (t, J = 7.2 Hz, 1 H), 6.14–6.09 (m, 1 H), 5.95–
5.88 (m, 1 H), 5.76–5.64 (m, 1 H), 2.12 (d, J = 2.8 Hz, 3 H), 2.11–
2.05 (m, 2 H), 1.48–1.39 (m, 2 H), 0.92 (t, J = 7.6 Hz, 3 H) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ = 207.3, 137.0, 133.5, 128.3,
128.2, 126.6, 125.8, 125.2, 101.6, 96.0, 34.8, 22.5, 17.1, 13.8 ppm.
HRMS: calcd. for C15Hl8 198.1408; found 198.1402.
Acknowledgments
Financial support from the National Science Council of Taiwan
under grant number NSC 99-2113-M-005-005-MY3 is appreciated.
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Three-Component Cyclization of Functionalized Allenes” in
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2005, pp. 183–210.
1-(3-Pyridyl)-3-phenylbuta-1,2-diene (2s): Yellow oil (0.145 g, 70%).
1H NMR (400 MHz, CDCl3): δ = 8.56 (d, J = 1.6 Hz, 1 H), 8.44
(dd, J = 1.6, 4.8 Hz, 1 H), 7.61 (dt, J = 2.0, 8.0 Hz, 1 H), 7.46–
7.42 (m, 2 H), 7.37–7.31 (m, 2 H), 7.27–7.19 (m, 2 H), 6.46 (q, J
= 3.2 Hz, 1 H), 2.24 (d, J = 3.2 Hz, 3 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 207.2, 148.3, 148.1, 135.7, 133.6, 130.5,
128.5, 127.3, 125.8, 123.5, 105.3, 93.3, 16.7 ppm. HRMS: calcd. for
C13Hl3N 207.1048; found 207.1041.
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1-Phenyl-3-methylhepta-1,2-diene (2t): Colorless oil (0.156 g, 84%).
1H NMR (400 MHz, CDCl3): δ = 7.32–7.24 (m, 4 H), 7.18–7.13
(m, 1 H), 6.06–6.02 (m, 1 H), 7.26–7.21 (m, 2 H), 2.10–2.05 (m, 2
H), 1.80 (d, J = 2.8 Hz, 2 H), 1.52–1.42 (m, 2 H), 1.41–1.31 (m, 2
H), 0.89 (t, J = 7.2 Hz, 3 H) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 202.6, 136.1, 128.5, 126.5, 126.3, 103.7, 93.7, 33.8,
29.7, 22.4, 18.8, 13.9 ppm. HRMS: calcd. for C14Hl8 186.1409;
found 186.1404.
1-Phneyl-3-cyclohexylbuta-1,2-diene (2u): Colorless oil (0.186 g,
1
87%). H NMR (400 MHz, CDCl3): δ = 7.31–7.25 (m, 4 H), 7.18–
7.13 (m, 1 H), 6.07 (dq, J = 2.4, 2.4 Hz, 1 H), 1.94–1.84 (m, 3 H),
1.81 (d, J = 2.8 Hz, 3 H), 1.78–1.71 (m, 2 H), 1.68–1.61 (m, 1 H),
1.34–1.10 (m, 5 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ =
202.2, 136.2, 128.5, 126.31, 126.27, 108.9, 94.4, 42.1, 32.1, 32.0,
26.4, 26.3, 17.2 ppm. HRMS: calcd. for C16H20 212.1565; found
212.1569.
1-Phenyl-3-trimethylsilylbuta-1,2-diene (2v): Colorless oil (0.177 g,
1
87%). H NMR (400 MHz, CDCl3): δ = 7.29–7.19 (m, 4 H), 7.15–
7.10 (m, 1 H), 5.81 (q, J = 2.8 Hz, 1 H), 1.81 (d, J = 2.8 Hz, 3 H),
0.15 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 205.6,
136.1, 128.5, 125.9, 125.7, 95.5, 88.3, 15.1, –1.7 ppm. HRMS:
calcd. for C13Hl8Si 202.1178; found 202.1174.
1-(4-Methylphneyl)-3-trimethylsilylbuta-1,2-diene (2w): Colorless oil
1
(0.196 g, 91%). H NMR (400 MHz, CDCl3): δ = 7.13–7.06 (m, 4
H), 5.79 (q, J = 2.8 Hz, 1 H), 2.31 (s, 3 H), 1.80 (d, J = 3.2 Hz, 3
H), 0.13 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ =
205.6, 135.4, 133.0, 129.2, 125.8, 95.4, 88.1, 21.1, 15.2, –1.7 ppm.
HRMS: calcd. for C13Hl8Si 202.1178; found 202.1174.
1-(4-Chlorophenyl)-3-trimethylsilylbuta-1,2-diene (2x): Colorless oil
1
(0.215 g, 91%). H NMR (400 MHz, CDCl3): δ = 7.24–7.20 (m, 2
H), 7.15–7.10 (m, 2 H), 5.76 (q, J = 3.2 Hz, 1 H), 1.81 (d, J =
2.8 Hz, 3 H), 0.14 (s, 9 H) ppm. 13C{1H} NMR (100 MHz, CDCl3):
δ = 205.4, 134.7, 131.1, 128.6, 127.0, 96.0, 87.5, 15.0, –1.8 ppm.
HRMS: calcd. for C13Hl7Si 236.0788; found 236.0782.
[6] For selected recent reports on the synthesis of allenes, see: a)
M. Ahmed, T. Arnauld, A. G. M. Barrett, D. C. Braddock, K.
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B. H. Lipshutz, N. Krause, Angew. Chem. Int. Ed. 2007, 46,
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3-(Naphthalen-2-yl)-3-trimethylsilylbuta-1,2-diene (2y): White solid
(0.231 g, 92%). H NMR (400 MHz, CDCl3): δ = 7.78–7.71 (m, 3
1
H), 7.56 (s, 1 H), 7.45–7.35 (m, 3 H), 5.99 (q, J = 2.8 Hz, 1 H),
1.86 (d, J = 2.8 Hz, 3 H), 0.17 (s, 9 H) ppm. 13C{1H} NMR
(100 MHz, CDCl3): δ = 206.1, 133.8, 133.7, 132.1, 128.0, 127.6,
127.4, 126.0, 125.0, 124.4, 124.0, 95.7, 88.8, 15.2, –1.7 ppm.
HRMS: calcd. for C17H20Si 252.1334; found 252.1327.
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of the H and 13C NMR spectra.
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Received: July 30, 2014
Published Online: October 28, 2014
Eur. J. Org. Chem. 2014, 7916–7923
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7923