Substituted 1-allyl-2-allenylbenzenes via palladium-catalyzed allylallenylation of benzyne derivatives

Article abstract of DOI:10.1055/s-2005-869966

An efficient method for the synthesis of 1-allyl-2-allenyl benzenes via palladium-catalyzed three-component assembly of benzynes, allyl chlorides, and allenylstannanes is described. Substituted benzyne precursors 1a-e undergo three-component assembly with

Full text of DOI:10.1055/s-2005-869966

SPECIAL TOPIC
1693
Substituted 1-Allyl-2-allenylbenzenes via Palladium-Catalyzed
Allylallenylation of Benzyne Derivatives
S
ubstituted 1-Allyl-2-a
a
llenylbenze
s
nes via Pa
i
lladium
l
-Cata
a
lyzed Allyl
m
allenylation of Benz
a
ynes ni Jeganmohan, Chien-Hong Cheng*
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
E-mail: chcheng@mx.nthu.edu.tw
Received 13 March 2005
ethene derivatives consisting of two electron-withdrawing
substituents at the same carbon to afford 1,7-enyne deriv-
atives in good yields. Our continued interest in this type of
reactions prompted us to explore the possibility of using
Abstract: An efficient method for the synthesis of 1-allyl-2-allenyl
benzenes via palladium-catalyzed three-component assembly of
benzynes, allyl chlorides, and allenylstannanes is described. Substi-
tuted benzyne precursors 1a–e undergo three-component assembly
with various allylic chlorides 2a–e and allenylstannanes in the pres- benzynes as the substrates for three-component reactions.
ence of Pd(dba)2/dppe (5 mol%), and cesium fluoride in acetonitrile
at ambient temperature affording 1-allyl-2-allenyl benzenes 4a–k in
good to excellent yields. The possible mechanism for the present
alkynylstannanes in the presence of a palladium catalyst
catalytic reaction is proposed.
Very recently, we have observed that benzynes underwent
a three-component reaction with allylic chlorides and
to afford 1,6-enyne derivatives in good yields.6 In this pa-
per, we wish to report a palladium-catalyzed addition of
allyl chlorides and allenylstannanes to arynes to give var-
Key words: 1,6-enynes, allylalkylation, palladium, benzyne, allyl-
ic chlorides, alkynylstannanes
ious 1-allyl-2-allenylbenzene derivatives in excellent
yields. 1,6-Enallenes are a versatile synthetic intermediate
Recently, the use of benzynes as substrates for metal-cat-
in various reactions, including [2 + 2] cycloaddition reac-
alyzed reactions has drawn substantial attention.1 The ad-
dition of a single-bonded amphiphilic species such as Te–
Te,2a S–S,2b Si–Si,2c Sn–Sn,2d C–Si,2e C–Sn,2f and N–CO2g
to benzynes is described in the literature. A double addi-
tion of two allyl groups to a benzyne moiety using allyl
chloride and allylstannane as the reagents has also been
reported.3 In this bisallylation reaction, the amphiphilic
bis-p-allylpalladium intermediate, generated from allyl
chloride and allylstannane, reacts with benzyne to give the
bis-allylation product. This reaction was limited by low
chemoselectivity when different allyl groups to allyl chlo-
ride and allylstannane were employed, giving a mixture of
cross-over products.
tion,7 ene reaction,7 cycloisomerization reaction,8 and
metal-catalyzed cyclization reaction,9 but they are diffi-
cult to prepare due to complicated procedures, harsh reac-
tion conditions, and poor yields.7–9 The present catalytic
reaction provides a convenient synthetic method for the
synthesis of these compounds in one pot under mild con-
ditions.
The reaction of (1-TfO)(2-TMS)benzene (1a) with allyl
chloride (2a) and tri(n-butyl)allenylstannane (3a) in the
presence of Pd(dba)2/dppe (5 mol%), and CsF in acetoni-
trile at ambient temperature for ten hours afforded the
three-component assembly product 1-allyl-2-allenylben-
zene (4a) in 93% yield (Scheme 1). Product 4a was thor-
oughly characterized by its 1H and 13C NMR spectroscopy
and mass spectroscopy. In the reaction, benzyne was
generated10 in situ from 1a and CsF; control experiments
revealed that in the absence of the palladium catalyst or
CsF 4a was not obtained.
We have been working on metal-catalyzed three-compo-
nent reactions involving allenes4 or activated alkenes5 as
substrates, leading to the formation of two new chemical
bonds in one pot. Thus, allylic chlorides and allenylstan-
nanes in the presence of palladium catalysts react with
R7
R6
R5
R4
R1
R2
OTf
R7
R6
R1
R2
R5
Cl
R4
Pd(dba)2/dppe, CsF
CH3CN, r.t., 10 h
+
+
Bu3Sn
R3
2a–e
SiMe 3
R3
1a–e
3a–c
4a–k
3a: R6 = R7 = H
3b: R6 = H, R7 = D
3c: R6 = Me, R7 = H
1a: R1 = R2 = H
2a: R3 = R4 = R5 = H
1b: R1 = R2 = Me
2b: R3 = R5 = H, R4 = Me
2c: R3 = R5 = Me, R4 = H
2d: R3 = R4 = H, R5 = Ph
2e: 3-chlorocyclohexene
1c: R1 + R2 = (-CH2-)3
1d: R1 + R2 = (-O-CH2-O-)
1e: R1 = R2 = F
Scheme 1
SYNTHESIS 2005, No. 10, pp 1693–1697
x
x.
x
x
.
2
0
0
5
Advanced online publication: 06.06.2005
DOI: 10.1055/s-2005-869966; Art ID: C03005SS
© Georg Thieme Verlag Stuttgart · New York

1694
M. Jeganmohan, C.-H. Cheng
SPECIAL TOPIC
The choice of phosphine ligand and solvent is important Table 1 Palladium-Catalyzed Allylallenylation of Benzynes with
Allylic Chlorides and Allenylstannanesa
to the catalytic reaction of 1a with 2a and 3a. Phosphine-
free palladium complexes Pd(dba)2, Pd(OAc)2, and
Entry
1
1
2
3
Product
Yield (%)b,c
PdCl2(CH3CN)2 in acetonitrile were totally ineffective for
the reaction. Monodentate phosphine palladium complex-
es such as Pd(PPh3)4, PdCl2(PPh3)2, and PdCl2(PCy3)2
were active, but gave 4a in low yields (26%, 20%, and
25%, respectively). It appears that a proper bidentate
phosphine ligand is required for the reaction to proceed in
high yield; therefore Pd(dba)2 with one equivalent of dppe
afforded 4a in 98% yield. The use of other bidentate phos-
phine ligands, dppm, dppp, and dppb gave 4a in 23%,
55%, and 15% yields, respectively. Of the solvents tested,
only acetonitrile is effective; other solvents such as tolu-
ene, THF, DMF, and CH2Cl2 were totally ineffective for
the reaction.
1a
2a
3a
4a
4b
4c
4d
93
(98)
2
3
4
1a
1a
1a
2b
2c
2d
3a
3a
3a
92
81
84
Ph
5
1a
2e
3a
4e
79
Under the optimized reaction conditions, substituted allyl-
ic chlorides also underwent the three-component reaction
with 1a and 3a to afford the corresponding 1-allyl-2-alle-
nylbenzene derivatives in excellent yields (Table 1).
Thus, methallyl chloride (2b) afforded 4b in 92% yield
(Table 1, entry 2), while cinnamyl chloride (2c), 4-chloro-
pent-2-ene (2d) and 3-chlorocyclohexene (2e) gave prod-
ucts 4c–e in 81%, 84%, and 79% yields, respectively
(Table 1, entries 3–5). It is noteworthy that the allylation
by 2c is highly regioselective giving exclusively the cin-
namyl substituted product (Table 1, entry 3).
6
7
1b
1e
2b
2b
3a
3a
4f
88
82
4g
F
F
8
9
1c
1d
1a
2b
2b
2b
3a
3a
3b
4h
4i
87
83
90
O
In addition to 1a, various benzyne precursors 1b–e were
successfully used for the three-component assembly with
2b and 3a. Compound 1b with two methyl groups on the
aromatic ring furnished product 4f in 88% yield, while 1e
with two fluoro-substituents gave 4g in 82% yield. Simi-
larly, the reaction of 2b and 3a with indene derivative 1d
and 1,3-benzodioxal derivative 1e afforded 4h and 4i in
87% and 83% yields, respectively. These results indicate
that the catalytic reaction was not affected by the substit-
uent on the benzyne ring.
O
D
10
4j
11
1a
2b
3c
4k
87
a All reactions were carried out under the following conditions: ben-
zyne precursors (1a–e, 1.00 mmol), allylic chlorides (2a–e, 1.20
mmol), allenylstannanes (3a–c, 1.20 mmol), Pd(dba)2–dppe (0.050
mmol), CsF (3.0 mmol) and CH3CN (3.0 mL).
The present protocol can be further applied to substituted
allenylstannane. The reaction of 1a and 2b with 1-deuter-
ated-1-allenylstannane 3b afforded 1-deuterated allenyl
product 4j, while 3-methyl-1-allenylstannane 3c gave 4k
in excellent yields. The deuterium-labeling study shows
that the addition of allenyltributylstannane takes place at
the a-position of the allenyl group. This is in contrast to
the results observed in the previous addition reaction of
allyl chloride and allenyltributylstannane with activated
olefins in which the allenyl group of 3a was added to ac-
tivated olefins at the g-carbon to give a propargyl prod-
uct.5
b Isolated yields: yields in parentheses were determined by the 1H
NMR integration method using mesitylene as an internal standard.
Subsequent reductive elimination of 8 affords the final
product and regenerates the Pd(0) catalyst.
Strong support for the involvement of benzyne in the re-
actions is the formation of a pair of regioisomers 9 and 10
in a ca. 50:50 ratio from the reaction of unsymmetrical
benzyne precursor 1f, methallyl chloride (2b) with alle-
nylstannane (3a) (Scheme 3). The lack of regioselectivity
is consistent with the insertion of unsymmetrical benzyne
into a palladium-carbon bond. In the literature, the inser-
tion of benzyne into a Pd(II)-allyl intermediate 7 also has
been proposed to explain the reaction of allyl chloride
with benzyne.1b,c
Based on the known palladium-catalyzed three-compo-
nent reactions2–6 a mechanism is proposed to account for
the present allylallenylation reaction (Scheme 2). The
first step involves oxidative addition of allyl chloride to
Pd(0) to give p-allyl palladium complex 5. Benzyne 6
generated from CsF and 1 then inserts into 5 to afford aryl
palladium intermediate 7. Transmetallation of allenyl-
stannanes with 7 gives intermediate 8 and Bu3SnCl.5,11
Another possible mechanism for the present catalytic re-
action involves the oxidative addition of allyl chloride to
Pd(0) to give p-allylpalladium complex 5, followed by
transmetallation of allenylstannane 3 with 5 to give s-al-
Synthesis 2005, No. 10, 1693–1697 © Thieme Stuttgart · New York

SPECIAL TOPIC
Substituted 1-Allyl-2-allenylbenzenes via Palladium-Catalyzed Allylallenylation of Benzynes
1695
Palladium-Catalyzed Three-Component Reactions; General
Procedure
A 25 mL round-bottomed side-arm flask containing Pd(dba)2/dppe
(0.0500 mmol), CsF (3.00 mmol) was evacuated and purged with
nitrogen gas thrice. To the flask were then added benzyne precursor
(1; 1.00 mmol), allyl chloride (2; 1.20 mmol), tri(n-butyl)allenyl-
stannane (3; 1.20 mmol), and CH3CN (3.0 mL) individually via sy-
ringe. The reaction mixture was allowed to stir at r.t. for 10 h. At the
end of the reaction, the reaction mixture was diluted with CH2Cl2,
filtered through celite and silica gel, and the filtrate was concentrat-
ed. The crude residue was purified through a silica gel column (hex-
ane) to give pure 4.
1-Allyl-2-(1,2-propadienyl)benzene (4a)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.47 (d, J = 7.8 Hz, 1 H, H-1),
7.22–7.17 (m, 3 H, H-3), 6.40 (t, J = 6.6 Hz, 1 H, H-1), 6.03–5.96
(m, 1 H, H-1), 5.14 (d, J = 6.6 Hz, 2 H, CH2), 5.12–5.00 (m, 2 H,
CH2), 3.48 (d, J = 6.0 Hz, 2 H, CH2).
Scheme 2
13C NMR (150 MHz, CDCl3): d = 210.3, 136.7, 136.4, 132.0, 129.9,
127.51, 127.0, 126.6, 115.9, 90.8, 78.0, 37.5.
HRMS: m/z calcd for C12H12, 156.0939; found, 156.0940.
lenyl p-allyl palladium intermediate 11 (Figure 1). Subse-
quent transfer of the allenyl and allyl groups to the
benzyne moiety affords the final product 4 and regener-
ates the Pd(0) catalyst. This type of mechanism, which has
been proposed for the bisallylation of benzyne catalyzed
by palladium complexes,3 cannot be totally ruled out.
1-(2-Methylallyl)-2-(1,2-propadienyl)benzene (4b)
Colorless oil.
1H NMR (500 MHz, CDCl3): d = 7.42 (d, J = 7.5 Hz, 1 H, H-1),
7.19–7.11 (m, 3 H, H-3), 6.33 (t, J = 6.5 Hz, 1 H, H-1), 5.08 (d, J =
6.5 Hz, 2 H, CH2), 4.81 (s, 1 H, H-1), 4.50 (s, 1 H, H-1), 3.35 (s, 2
H, CH2), 1.73 (s, 3 H, CH3).
13C NMR (125 MHz, CDCl3): d = 210.3, 144.4, 136.2, 132.5, 130.6,
127.4, 126.8, 126.6, 111.9, 90.9, 78.03, 41.5, 22.7.
Pd
L
HRMS: m/z calcd for C13H14, 170.1096; found, 170.1092.
11
1-[(E)-3-Phenyl-2-propenyl]-2-(1,2-propadienyl)benzene (4c)
Figure 1
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.52 (d, J = 7.8 Hz, 1 H, H-1),
7.40–7.24 (m, 8 H, H-8), 6.48 (t, J = 6.6 Hz, 1 H, H-1), 6.42–6.40
(t, J = 5.4 Hz, 2 H, H-2), 5.18 (d, J = 6.6 Hz, 2 H, CH2), 3.67 (t,
J = 2.4 Hz, 2 H, CH2).
13C NMR (150 MHz, CDCl3): d = 210.4, 137.4, 136.6, 132.1, 131.0,
130.0, 128.6, 128.5, 127.6, 127.1, 126.7, 125.7, 90.9, 78.1, 36.6.
It should be noted that the palladium-catalyzed addition of
allenylstannane to a Pd-allyl species to give a 1,5-enyne
product is known in the literature.12 However, under our
standard conditions, no such product was observed. This
result strongly indicates that the present reaction is faster
than the competitive propargylation reaction.
HRMS: m/z calcd for C18H16, 232.1252; found, 232.1248.
In conclusion, we have developed a palladium-catalyzed
three-component reaction of arynes with allylic chlorides
and allenylstannanes. This method results in the construc-
tion of two different C–C bonds in one pot and allows an
efficient synthesis of various 1-allyl-2-allenyl benzene 1), 7.23–7.15 (m, 3 H, H-3), 6.49 (t, J = 7 Hz, 1 H, H-1), 5.66–5.64
derivatives in excellent yields. Further application of the
1-[(E)-1-Methyl-2-butenyl]-2-(1,2-propadienyl)benzene (4d)
Colorless oil.
1H NMR (500 MHz, CDCl3): d = 7.44 (d, J = 7.5 Hz, 2 Hz, 1 H, H-
(dd, J = 5 Hz, 1 Hz, 1 H, H-1), 5.63–5.45 (m, 1 H, H-1) 5.12 (d, J =
7 Hz, 2 H, CH2), 3.77–3.74 (m, 1 H, H-1), 1.69 (d, J = 13 Hz, 3 H,
CH3), 1.34 (d, J = 10 Hz, 3 H, CH3).
methodology in organic synthesis and detailed mechanis-
tic studies of the catalytic reaction are in progress.
OTf
Cl
Pd(dba)2/dppe, CsF
CH3CN, r.t., 10 h
Bu3Sn
SiMe3
3a
2b
1f
9
50:50
88%
10
Scheme 3
Synthesis 2005, No. 10, 1693–1697 © Thieme Stuttgart · New York

1696
M. Jeganmohan, C.-H. Cheng
SPECIAL TOPIC
13C NMR (125 MHz, CDCl3): d = 210.4, 142.8, 135.5, 131.2, 127.7,
127.1, 126.8, 126.1, 124.1, 90.7, 77.8, 37.4, 20.9, 17.9.
13C NMR (100 MHz, CDCl3): d = 210.3, 144.4, 136.2, 132.4, 130.6,
127.4, 126.8, 126.6, 111.9, 90.9, 90.7, 90.5, 78.0, 41.5, 22.7.
HRMS: m/z calcd for C14H16, 184.1252; found, 184.1249.
HRMS: m/z calcd for C13H13D, 171.1157; found, 171.1152.
1-(2-Cyclohexenyl)-2-(1,2-propadienyl)benzene (4e)
Colorless oil.
1-(1,2-Butadienyl)-2-(2-methylallyl)benzene (4k)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.42–7.14 (m, 5 H, H-5), 6.46 (t,
J = 6.6 Hz, 1 H, H-1), 5.93–5.91 (m, 1 H, H-1), 5.69–5.67 (m, 1 H,
H-1), 5.10–5.08 (dd, J = 6.6 Hz, 3.6 Hz, 2 H, CH2), 3.72–3.70 (m,
1 H, H-1), 2.10–1.60 (m, 6 H, CH2).
1H NMR (600 MHz, CDCl3): d = 7.42 (d, J = 7.2 Hz, 1 H, H-1),
7.20–7.13 (m, 3 H, H-3), 6.30–6.27 (m, 1 H, H-1), 5.51–5.47 (m, 1
H, H-1), 4.84 (s, 1 H, H-1), 4.54 (s, 1 H, H-1), 3.40 (s, 2 H, CH2),
1.79–1.76 (m, 6 H, CH3).
13C NMR (150 MHz, CDCl3): d = 210.5, 142.8, 131.2, 130.1, 128.7,
128.2, 127.8, 126.9, 126.2, 90.7, 77.8, 37.8, 31.2, 25.0, 21.0.
13C NMR (150 MHz, CDCl3): d = 206.6, 144.5, 136.2, 133.6, 130.6,
127.5, 126.6, 126.5, 111.9, 91.1, 88.7, 41.5, 22.7, 14.1.
HRMS: m/z calcd for C15H16, 196.1252; found, 196.1251.
HRMS: m/z calcd for C14H16, 184.1252; found, 184.1255.
1,2-Dimethyl-4-(2-methylallyl)-5-(1,2-propadienyl)benzene (4f)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.21 (s, 1 H, H-1), 6.91 (s, 1 H, H-
1), 6.31 (t, J = 6.6 Hz, 1 H, H-1), 5.10 (d, J = 6.6 Hz, 2 H, CH2),
4.82 (s, 1 H, H-1), 4.55 (s, 1 H, H-1), 3.32 (s, 2 H, CH2), 2.25 (s, 3
H, CH3), 2.24 (s, 3 H, CH3), 1.75 (s, 3 H, CH3).
4-Methyl-2-(2-methylallyl)-1-(1,2-propadienyl)benzene (9) and
4-Methyl-1-(2-methylallyl)-2-(1,2-propadienyl)benzene (10)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.32–7.01 (m, 2 H, H-2), 6.94–
6.31 (m, 4 H, H-4), 4.85 (s, 1 H, H-1), 6.32 (t, J = 6.6 Hz, 1 H, H-
1), 6.31 (t, J = 6.6 Hz, 1 H, H-1), 5.10 (d, J = 6.6 Hz, 2 H, CH2),
5.08 (d, J = 6.6 Hz, 2 H, CH2), 4.82 (s, 2 H, CH2), 4.52 (s, 2 H, CH2),
3.33 (s, 4 H, CH2), 2.31 (s, 3 H, CH3), 2.30 (s, 3 H, CH3), 1.74 (s, 3
H, CH3),1.73 (s, 3 H, CH3).
13C NMR (150 MHz, CDCl3): d = 210.2, 210.1, 144.7, 144.5, 136.5,
136.1, 133.0, 132.1, 131.3, 130.6, 129.4, 127.9, 127.8, 127.5, 111.9,
111.8, 90.9, 90.8, 90.9, 90.8, 77.9, 77.9, 41.5, 41.2, 22.7, 22.7, 21.1,
20.9.
13C NMR (150 MHz, CDCl3): d = 210.0, 144.8, 135.3, 134.8, 133.6,
131.9, 129.6, 128.5, 111.7, 90.7, 77.7, 41.7, 22.7, 19.7, 19.7.
HRMS: m/z calcd for C15H18, 198.1409; found, 198.1412.
1-2-Difluoro-4-(2-methyallyl)-5-(1,2-propadienyl)benzene (4g)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 7.22–7.19 (dd, J = 12 Hz, 8.2 Hz,
1 H, H-1), 6.93–6.90 (dd, J = 12 Hz, 8.2 Hz, 1 H, H-1), 6.21 (t,
J = 6.6 Hz, 1 H, H-1), 5.13 (d, J = 6.6 Hz, 2 H CH2), 4.84 (s, 1 H,
H-1), 4.52 (s, 1 H, H-1), 3.29 (s, 2 H, CH2), 1.72 (s, 3 H, CH3).
HRMS: m/z calcd for C14H16, 184.1252; found, 184.1249.
Acknowledgment
13C NMR (150 MHz, CDCl3): d = 210.1, 149.6, 148.8, 143.5, 136.0,
133.3, 118.9, 115.7, 112.6, 89.8, 78.9, 40.7, 22.5.
We thank the National Science Council of the Republic of China
(NSC-92-2113-M-007-044) for support of this research.
HRMS: m/z calcd for C13H12F2, 206.0907; found, 206.0912.
5-(2-Methylallyl)-6-(1,2-propadienyl)indane (4h)
Colorless oil.
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1H NMR (600 MHz, CDCl3): d = 7.32 (s, 1 H, H-1), 7.06 (s, 1 H, H-
1), 6.35 (t, J = 6.6 Hz, 1 H, H-1), 5.09 (d, J = 6.6 Hz, 2 H, CH2),
4.83 (s, 1 H, H-1), 4.56 (s, 1 H, H-1), 3.35 (s, 2 H, CH2), 2.89–2.86
(m, 4 H, CH2), 2.08–2.03 (m, 2 H, CH2), 1.71 (s, 3 H, CH3).
13C NMR (150 MHz, CDCl3): d = 210.1, 144.8, 143.3, 142.7, 134.1,
130.0, 126.4, 123.0, 111.7, 91.2, 77.8, 41.6, 32.6, 32.5, 25.5, 22.7.
HRMS: m/z calcd for C16H18, 210.1409; found, 210.1405.
5-(2-Methylallyl)-6-(1,2-propadienyl)-1,3-benzodioxole (4i)
Colorless oil.
1H NMR (600 MHz, CDCl3): d = 6.91 (s, 1 H, H-1), 6.60 (s, 1 H, H-
1), 6.26 (t, J = 6.6 Hz, 1 H, H-1), 5.90 (s, 2 H, CH2), 5.08 (d, J = 6.6
Hz, 2 H, CH2), 4.80 (s, 1 H, H-1), 4.54 (s, 1 H, H-1), 3.25 (s, 2 H,
CH2), 1.75 (s, 3 H, CH3).
13C NMR (150 MHz, CDCl3): d = 209.8, 146.6, 146.5, 144.4, 129.9,
125.6, 111.9, 110.3, 106.8, 100.9, 90.9, 78.5, 41.3, 22.5.
HRMS: m/z calcd for C14H14O2, 214.0994; found, 214.0995.
1-(1-Deuterio-1,2-propadienyl)-2-(2-methylallyl)benzene (4j)
Colorless oil.
1H NMR (400 MHz, CDCl3): d = 7.42 (d, J = 7.6 Hz, 1 H, H-1),
7.26–7.16 (m, 3 H, H-3), 5.15 (s, 2 H, CH2), 4.88 (s, 1 H, H-1), 4.57
(s, 1 H, H-1), 3.42 (s, 2 H, CH2), 1.80 (s, 3 H, CH3).
(c) Jeganmohan, M.; Shanmugasundaram, M.; Chang, K.-J.;
Cheng, C.-H. Chem. Commun. 2002, 2552.
(d) Jeganmohan, M.; Shanmugasundaram, M.; Cheng, C.-H.
Chem. Commun. 2003, 1736. (e) Yang, F.-Y.;
Shanmugasundaram, M.; Chuang, S.-Y.; Ku, P.-J.; Wu, M.-
Y.; Cheng, C.-H. J. Am. Chem. Soc. 2003, 125, 12576.
Synthesis 2005, No. 10, 1693–1697 © Thieme Stuttgart · New York

SPECIAL TOPIC
Substituted 1-Allyl-2-allenylbenzenes via Palladium-Catalyzed Allylallenylation of Benzynes
1697
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Synthesis 2005, No. 10, 1693–1697 © Thieme Stuttgart · New York