Room-temperature palladium-catalyzed allyl cross-coupling reaction with boronic acids using phosphine-free hydrazone ligands

Article abstract of DOI:10.1055/s-0028-1083381

Palladium-catalyzed allyl cross-coupling reaction of allylic acetates with a variety of boronic acids at room temperature using a catalytic amount of Pd(OAc)₂ with phosphine-free hydrazone as a ligand gave the allylbenzene derivatives in good yields.

Full text of DOI:10.1055/s-0028-1083381

LETTER
2711
Room-Temperature Palladium-Catalyzed Allyl Cross-Coupling Reaction with
Boronic Acids Using Phosphine-Free Hydrazone Ligands
P
d-Catalyze
d
A
a
llyl Cross-
C
k
oupling Re
a
a
ction shi Mino,* Kenji Kajiwara, Yoshiaki Shirae, Masami Sakamoto, Tsutomu Fujita
Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho,
Inage-ku, Chiba 263-8522, Japan
Fax +81(43)2903401; E-mail: tmino@faculty.chiba-u.jp
Received 3 July 2008
R1
R1
R1
R2
Abstract: Palladium-catalyzed allyl cross-coupling reaction of al-
lylic acetates with a variety of boronic acids at room temperature us-
ing a catalytic amount of Pd(OAc)2 with phosphine-free hydrazone
as a ligand gave the allylbenzene derivatives in good yields.
N
R2
N
N
N
R2
N
N N
2a: R1,R2 = (CH2)6
2b: R1,R2 = (CH2)5
1a: R1 = Ph, R2 = Me
1b: R1,R2 = (CH2)6
1c: R1,R2 = (CH2)5
1d: R1,R2 = (CH2)4
Key words: palladium, catalysis, allyl cross-coupling, boronic
acid, hydrazones
Figure 1 Hydrazone ligands 1 and 2
Palladium-catalyzed C–C bond formation reactions have
been recognized as powerful tools in multiple organic
transformations.1 Palladium-catalyzed cross-coupling of
aryl and vinyl halides with aryl- and vinylboronic acids
(Suzuki–Miyaura coupling)2 has especially gained popu-
larity due to broad functional group tolerance, the avail-
ability of boronic acid substrates, and the lack of toxic by-
products. On the other hand, a 1,3-diarylpropene frame-
work constitutes an important structural assembly in
many molecules of biological importance.3 The palladi-
um-catalyzed allyl cross-coupling reaction of cinnamyl
acetate with arylboronic acids provides a powerful tool for
the synthesis of 1,3-diarylpropenes. Previously allyl
cross-coupling reactions of allylic acetates using
PdCl2(TFP)2 with KF as a fluoride source,4 resin-support-
ed Pd-bis(PPh3) complex5 and Pd2(dba)3·CHCl3–PPh3 un-
der microwave irradiation conditions6 were reported.
However, phosphines in palladium complexes are often
air-sensitive. Although phosphine-free palladium catalyt-
ic systems have also been reported,7 these reactions re-
quire additional tetra-n-butyl ammonium salt as an
activator, heating conditions, or long times to complete
the reaction. We recently demonstrated air-stable phos-
phine-free hydrazone as an effective ligand for palladium-
catalyzed C–C bond formation such as the Suzuki–
Miyaura,8 Mizoroki–Heck,9 Sonogashira, and Hiyama
cross-coupling reactions.10 We now report the use of
phosphine-free hydrazone ligands 1 and 2 (Figure 1) for a
palladium-catalyzed allyl cross-coupling reaction of allyl-
ic acetates with boronic acids at room temperature.
sphere at room temperature to determine the optimum re-
action conditions (Table 1).
The effect of various hydrazone ligands was investigated
using Pd(OAc)2 with K2CO3 as a base (Table 1, entries 1–
5). In the presence of hydrazone 1a, which is the effective
ligand for the Suzuki–Miyaura reaction of aryl halides,
1,3-diphenylpropene (3a) was obtained in moderate yield
(Table 1, entry 1). In this reaction, small amounts of 411
and 512 were also obtained as by-products. The use of hy-
drazone 1c with a 6-membered ring as a ligand led to high
yield (Table 1, entry 3). On the other hand, hydrazone 2a
was not effective for this reaction (Table 1, entry 5). Next,
the effect of various palladium sources was investigated
(Table 1, entries 3 and 6–9). Pd(OAc)2 proved to be the
best palladium source for this reaction. Several bases were
also tested (Table 1, entries 3 and 10–13). Although the
use of fluoride salts such as KF and CsF led to good yields
(Table 1, entries 12 and 13), K2CO3 was found to be the
most effective base in this reaction (entry 3). Finally the
effect of various solvents was investigated (Table 1, en-
tries 3 and 14–20). The DMF–H2O (3:1) mixture was
found to be the solvent of choice. Other solvents proved
less effective in this reaction.
The effect of leaving groups of cinnamyl esters in this re-
action was investigated (Table 2, entries 1–3). Using cin-
namyl benzoate and pivalate instead of acetate, the yields
were decreased (Table 2, entry 1 vs. entries 2 and 3).
Based on these results, the allyl cross-coupling reaction of
cinnamyl and allyl acetate with various boronic acids was
investigated (Table 2, entries 4–14).13
We examined the allyl cross-coupling reaction of cin-
namyl acetate and phenylboronic acid in the presence of
2 mol% of Pd catalyst for one hour under an argon atmo-
Using p-tolylboronic acid led to good yields of the desired
products (Table 2, entry 4). With 4-methoxyphenylboron-
ic acid (2 equiv), the reaction gave the corresponding
product with moderate yield after one hour (Table 2, entry
5). In the reaction of 4-trifluoromethylphenylboronic acid
longer reaction times, such as 24 h, were necessary
SYNLETT 2008, No. 17, pp 2711–2715
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x
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x
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Advanced online publication: 01.10.2008
DOI: 10.1055/s-0028-1083381; Art ID: U07008ST
© Georg Thieme Verlag Stuttgart · New York

2712
T. Mino et al.
LETTER
Table 1 Optimization of Reaction Conditions for Phenylation of Cinnamyl Acetatea
Pd source, ligand
base, solvent–H2O
Ph
Ph
+
+
+
PhB(OH)2
Ph
OAc
Ph
Ph
Ph
r.t., 1 h, argon
Ph
4
5
3a
Entry
1
Ligand
1a
1b
1c
Pd source
Base
Solvent
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
NMP
MeOH
MeCN
DMSO
DMFd
DMFe
DMFf
3a/4/5b
Yield (%)c
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
PdCl2
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K3PO4
Cs2CO3
CsF
98.0/1.5/0.5
99.0/0.8/0.2
99.0/0.8/0.2
98.8/0.9/0.3
98.5/1.0/0.5
97.8/1.3/0.9
98.9/1.0/0.1
98.8/1.0/0.2
99.0/0.5/0.5
98.1/1.0/0.9
98.6/1.1/0.3
98.8/1.1/0.1
98.8/1.1/0.1
98.9/0.8/0.3
98.4/1.1/0.5
98.8/1.1/0.1
98.2/1.4/0.4
98.8/0.9/0.3
99.0/0.8/0.2
97.9/1.4/0.7
78
92
94
89
69
71
92
88
5
2
3
4
1d
2a
1c
5
6
7
1c
[PdCl(allyl)]2
PdCl2(MeCN)2
Pd(acac)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
8
1c
9
1c
10
11
12
13
14
15
16
17
18
19
20
1c
86
69
89
79
92
72
52
57
64
75
52
1c
1c
1c
KF
1c
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
1c
1c
1c
1c
1c
1c
a Reaction conditions: cinnamyl acetate (0.5 mmol), phenylboronic acid (0.6 mmol), base (1.0 mmol), solvent (1.5 mL), H2O (0.5 mL),
palladium source (0.01 mmol), ligand (0.01 mmol).
b Determined by 1H NMR.
c Isolated yields.
d In this reaction, DMF (2 mL) was added in the absence of H2O.
e In this reaction, a mixture of DMF (1.9 mL) and H2O (0.1 mL) was added.
f In this reaction, a mixture of DMF (1 mL) and H2O (1 mL) was added.
(Table 2, entry 6). The reactions of other arylboronic ac- bly in many molecules of biological importance14 in addi-
ids led to good yields after one hour (Table 2, entries 7– tion to its applications in organic synthesis.15 Recently,
9). The reactions of cinnamyl acetate derivatives with the reaction of vinyltrifluoroborate with allyl acetate was
phenylboronic acid also led to good yields after one hour reported.16 In this case, 1,4-dienes were obtained using
(Table 2, entries 10–12). Next we investigated the reac- PdCl2(dppf)·CH2Cl2 under microwave irradiation at 80
tion of allyl acetate. Using 1-naphthaleneboronic acid led °C. On the other hand, in our case, the reaction of 2-phe-
to good yield of 1-allylnaphthalene (Table 2, entry 13). nylvinylboronic acid with cinnamyl acetate gave a high
Moreover, we investigated the vinylation of cinnamyl ac- yield of the corresponding 1,4-diene-type product 3l after
etate for the preparation of 1,4-diene. The 1,4-diene one hour at room temperature under phosphine-free con-
framework also constitutes an important structural assem- ditions (Table 2, entry 14).
Synlett 2008, No. 17, 2711–2715 © Thieme Stuttgart · New York

LETTER
Pd-Catalyzed Allyl Cross-Coupling Reaction
2713
Table 2 Allyl Cross-Coupling Reaction of Cinnamyl Esters and
of the Pd(OAc)2/hydrazone 2a system and 2.6 equivalents
of Cs2CO3 as a base in MeCN at room temperature under
an argon atmosphere for 24 hours (Table 3, entry 9).18
Based on these results, the reaction of geranyl acetate,
neryl acetate, and linalyl acetate with 1-naphthalenebo-
ronic acid was investigated (Table 3, entries 11–13). Al-
though these allylic acetates easily gave b-hydride-
eliminated 1,3-diene products via p-allylpalladium inter-
mediate using palladium catalyst such as a catalytic
amount of Pd(PPh3)4,19 an E/Z mixture of product 3n was
obtained with good yields in all cases.
Allyl Acetate with Boronic Acidsa
Pd(OAc)2
ligand 1c
K2CO3
DMF–H2O
+
R'B(OH)2
R
OAc
R
R'
r.t., 1 h, argon
3
Entry
1
R
R¢
Product
Yield (%)b
Ph
Phc
Phd
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
3a
3a
3a
3b
3c
3d
3e
3f
94
83
79
85
64
71
92
92
79
80
77
86
88
96g
2
In conclusion, we found that the palladium-catalyzed allyl
cross-coupling reaction of allylic acetates with boronic
acids at room temperature using a catalytic amount of
Pd(OAc)2 with phosphine-free hydrazone 1c or 2a as a
ligand gave the allylbenzene derivatives in good yields.
3
4
p-MeC6H4
5e
6f
p-MeOC6H4
p-CF3C6H4
3,5-Me2C6H3
o-MeC6H4
1-Naph
Ph
References and Notes
7
(1) For reviews, see the following: (a) Larhed, M.; Hallberg, A.
In Handbook of Organopalladium Chemistry for Organic
Synthesis, Vol. 1; Negishi, E., Ed.; Wiley-Interscience: New
York, 2002, 1133. (b) Whitcombe, N. J.; Hii, K. K.; Gibson,
S. E. Tetrahedron 2001, 57, 7449. (c) Beletskaya, I. P.;
Cheprakov, A. V. Chem. Rev. 2000, 100, 3009.
8
9
3g
3h
3i
10
11
12
13
14
p-MeC6H4
p-MeOC6H4
p-NO2C6H4
H
(d) Hegedus, L. S. Transition Metals in the Synthesis of
Complex Organic Molecules, 2nd ed.; University Science
Books: Sausalito CA, 1999, Chap. 4.6. (e) Bräse, S.; de
Meijere, A. In Metal-Catalyzed Cross-Coupling Reactions;
Diederich, F.; Stang, P. J., Eds.; Wiley-VCH: Weinheim
Germany, 1998, Chap. 3. (f) Link, J. T.; Overman, L. E. In
Metal-Catalyzed Cross-Coupling Reactions; Diederich, F.;
Stang, P. J., Eds.; Wiley-VCH: Weinheim Germany, 1998,
Chap. 6. (g) Beller, M.; Riermeier, T. H.; Stark, G. In
Transition Metals for Organic Synthesis, Vol. 1; Beller, M.;
Bolm, C., Eds.; Wiley-VCH: Weinheim Germany, 1998,
208. (h) Crisp, G. T. Chem. Soc. Rev. 1998, 27, 427.
(i) Tsuji, J. Palladium Reagents and Catalysts: Innovations
in Organic Synthesis; Wiley: Chichester U.K., 1995.
(2) For reviews, see: (a) Llord-Williams, P.; Giralt, E. Chem.
Soc. Rev. 2001, 30, 145. (b) Suzuki, A. J. Organomet.
Chem. 1999, 576, 147. (c) Suzuki, A. Metal-Catalyzed
Cross-Coupling Reactions; Diederich, F.; Stang, P. J., Eds.;
Wiley-VCH: Weinheim, 1998, 49. (d) Stanforth, S. P.
Tetrahedron 1998, 54, 263. (e) Miyaura, N.; Suzuki, A.
Chem. Rev. 1995, 95, 2457.
(3) (a) Su, C.-R.; Shen, Y.-C.; Kuo, P.-C.; Leu, Y.-L.; Damu,
A. G.; Wang, Y.-H.; Wu, T.-S. Bioorg. Med. Chem. Lett.
2006, 16, 6155. (b) Belley, M.; Chan, C. C.; Gareau, Y.;
Gallant, M.; Juteau, H.; Houde, K.; Lachance, N.; Labelle,
M.; Sawyer, N.; Tremblay, N.; Limontage, S.; Carrière,
M.-C.; Denis, D.; Greig, G. M.; Slipez, D.; Gordon, R.;
Chauret, N.; Lo, C.; Zamboni, R. J.; Metters, K. M. Bioorg.
Med. Chem. Lett. 2006, 16, 5639. (c) Anderson, J. C.;
Headly, C.; Stapleton, P. D.; Taylor, P. W. Tetrahedron
2005, 61, 7703. (d) Kramer, B.; Waldvugel, S. R. Angew.
Chem. Int. Ed. 2004, 43, 2446.
Ph
Ph
3j
1-Naph
3k
Ph
trans-PhCH=CH 3l
a Reaction conditions: acetate (0.5 mmol), boronic acid (0.6 mmol),
K2CO3 (1.0 mmol), DMF (1.5 mL), H2O (0.5 mL), Pd(OAc)2 (2
mol%), ligand 1c (2 mol%), r.t., 1 h, under argon.
b Isolated yields (GC–MS purities of all products were >98%).
c This reaction was carried out using benzoate instead of acetate.
d This reaction was carried out using pivalate instead of acetate.
e This reaction was carried out using 4-methoxyphenylboronic acid
(1.0 mmol).
f This reaction was carried out for 24 h.
g GC–MS purity of 3l was 94.9%.
We also tried the reaction of disubstituted allylic acetates
such as prenyl acetate with 1-naphthaleneboronic acid.
Using similar conditions as the reaction with cinnamyl ac-
etate (Table 3, entry 1), the corresponding product, how-
ever, was not obtained. In this case, naphthalene, which
was the reduced product of 1-naphthaleneboronic acid,
was obtained. Consequently, we attempted to optimize the
coupling conditions of prenyl acetate with 1-naphtha-
leneboronic acid (Table 3). When DMF was used as a sol-
vent in the absence of H2O, a small amount of reaction
product 3m was obtained (Table 3, entry 2). Using 5
mol% of Pd(OAc)2 and ligand 1c for 24 hours increased
the yield of 3m to 15% (Table 3, entry 3). The allyl cross-
coupling conditions were optimized using a variety of
bases (K2CO3, CsF, Cs2CO3), solvents (DMF, MeCN,
MeOH), and ligands (1a, 1c, 2a, 2b17) (Table 3, entries 3–
10). We found the following optimized conditions: 5 mol%
(4) (a) Bouyssi, D.; Gerusz, V.; Balme, G. Eur. J. Org. Chem.
2002, 2445. (b) Ortar, G. Tetrahedron Lett. 2003, 44, 4311.
(5) Uozumi, Y.; Danjo, H.; Hayashi, T. J. Org. Chem. 1999, 64,
3384.
(6) Polackova, V.; Toma, S.; Kappe, C. O. Tetrahedron 2007,
63, 8742.
Synlett 2008, No. 17, 2711–2715 © Thieme Stuttgart · New York

2714
T. Mino et al.
LETTER
Table 3 Allyl Cross-Coupling Reaction of Disubstituted Allylic Acetates with 1-Naphthaleneboronic Acida
Entry
Allylic acetate
prenyl acetate
Ligand
Base
Solvent
Product
Yield (%)b
1c
2c
3
4
5
6
7
8
9
1c
1c
1c
1c
1c
1c
1c
1a
2a
2b
K2CO3
K2CO3
K2CO3
CsF
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
DMF–H2O (3:1)
DMF
DMF
DMF
DMF
MeCN
MeOH
MeCN
MeCN
MeCN
0
3
15
6
22
47
1
37
62
37
3m
10
11
12
13
geranyl acetate
neryl acetate
linalyl acetate
2a
2a
2a
Cs2CO3
Cs2CO3
Cs2CO3
MeCN
MeCN
MeCN
69d
68e
70f
3n
a Reaction conditions: acetate (0.5 mmol), 1-naphthaleneboronic acid (0.6 mmol), base (1.3 mmol), solvent (2 mL), Pd(OAc)2 (5 mol%), ligand
(5 mol%), r.t., 24 h, under argon.
b Isolated yields (GC–MS purities of all products were >98%).
c This reaction was carried out using Pd(OAc)2 (2 mol%) and ligand 1c with K2CO3 (1.0 mmol) for 1 h.
d E/Z mixture = 66:34.
e E/Z mixture = 48:52.
f E/Z mixture = 62:38.
(7) (a) Nájera, C.; Gil-Moltó, J.; Karlström, S. Adv. Synth.
Catal. 2004, 346, 1798. (b) Botella, L.; Nájera, C.
J. Organomet. Chem. 2002, 663, 46.
(8) (a) Mino, T.; Shirae, Y.; Sakamoto, M.; Fujita, T. Synlett
2003, 882. (b) Mino, T.; Shirae, Y.; Sakamoto, M.; Fujita, T.
J. Org. Chem. 2005, 70, 2191.
(14) (a) Durand, S.; Parrain, J.-L.; Santelli, M. J. Chem. Soc.,
Perkin Trans. 1 2000, 253. (b) Andrey, O.; Glanzmann, C.;
Landais, Y.; Parra-Rapado, L. Tetrahedron 1997, 53, 2835.
(c) Nicolaou, K. C.; Ramphal, J. Y.; Petasis, N. A.; Serhan,
C. N. Angew. Chem., Int. Ed. Engl. 1991, 30, 1100.
(15) (a) Basavaiah, D.; Sharada, D. S.; Kumaragurubaran, N.;
Reddy, R. M. J. Org. Chem. 2002, 67, 7135. (b) Tsukada,
N.; Sato, T.; Inoue, Y. Chem. Commun. 2001, 237.
(9) Mino, T.; Shirae, Y.; Sasai, Y.; Sakamoto, M.; Fujita, T.
J. Org. Chem. 2006, 71, 6834.
(10) Mino, T.; Shirae, Y.; Saito, T.; Sakamoto, M.; Fujita, T.
J. Org. Chem. 2006, 71, 9499.
(11) Lawrence, N. J.; Muhammad, F. Tetrahedron 1998, 54,
(c) Klaps, E.; Schmid, W. J. Org. Chem. 1999, 64, 7537.
(d) Hara, R.; Nishihara, Y.; Landre, P. D.; Takahashi, T.
Tetrahedron Lett. 1997, 38, 447. (e) Prasad, A. S. B.;
Knochel, P. Tetrahedron 1997, 53, 16711. (f) Denmark, S.
E.; Guagnano, V.; Dixon, J. A. J. Org. Chem. 1997, 62,
4610. (g) Matsuhashi, H.; Hatanaka, Y.; Kuroboshi, M.;
Hiyama, T. Tetrahedron Lett. 1995, 36, 1539.
(h) Kobayashi, Y.; Ikeda, E. Chem. Commun. 1994, 1789.
(i) Matsushita, H.; Negishi, E. J. Am. Chem. Soc. 1981, 103,
2882.
15345.
(12) (a) Llobet, A.; Masllorens, E.; Rodriguez, M.; Roglans, A.;
Benet-Buchhollz, J. Eur. J. Inorg. Chem. 2004, 8, 1601.
(b) Rodríguez, D.; Sestelo, P. S.; Sarandeses, L. A. J. Org.
Chem. 2003, 68, 2518.
(13) General Procedure for Allyl Cross-Coupling Reaction of
Cinnamyl and Allyl Acetate with Boronic Acids (Table
2): To a mixture of acetate (0.5 mmol), K2CO3 (138.2 mg,
1.0 mmol), Pd(OAc)2 (2.24 mg, 0.01 mmol), and ligand 1c
(2.22 mg, 0.01 mmol) in DMF (1.5 mL) and H2O (0.5 mL)
was added boronic acid (0.6 mmol) at r.t. under an
atmosphere of argon. After 1 h, the mixture was diluted with
EtOAc and H2O. The organic layer was washed with brine,
dried over MgSO4, and concentrated under reduced pressure.
The residue was purified by silica gel chromatography. All
prepared compounds 3 (except for 3e) were known and
identified by 1H NMR, 13C NMR, and MS. Analytical Data
of 3e (Table 2, entry 7): colorless oil. IR (neat): 1604 cm–1.
1H NMR (CDCl3): d = 2.29 (s, 6 H), 3.47 (d, J = 6.5 Hz, 2
H), 6.33 (dt, J = 15.7, 6.6 Hz, 1 H), 6.45 (d, J = 15.9 Hz, 1
H), 6.86 (s, 3 H), 7.16–7.37 (m, 5 H). 13C NMR (CDCl3):
d = 21.1, 39.2, 126.1, 126.4, 127.0, 127.8, 128.5, 129.4,
130.8, 137.5, 138.0, 140.0. MS (EI, relative intensity): m/z =
222 (86) [M+]. HRMS (FAB–MS): m/z calcd for C17H18:
222.1409; found: 222.1408. GC–MS purity: 98.5%.
(16) Kabalka, G. W.; Al-Masum, M. Org. Lett. 2006, 8, 11.
(17) Preparation of Hydrazone 2b: To a solution of
N-aminopiperidine (0.060 g, 0.60 mmol) in MeOH (2.0 mL)
was added 2-pyridinecarboxaldehyde (0.054 g, 0.51 mmol)
and the mixture was stirred for 24 h at r.t. The mixture was
directly concentrated under reduced pressure. The residue
was purified by silica gel chromatography (hexane–EtOAc,
4:1). Yield: 0.092 g, 0.49 mmol, 96%; colorless oil. IR
(neat): 1572 cm–1. 1H NMR (CDCl3): d = 1.51–1.59 (m, 2 H),
1.66–1.79 (m, 4 H), 3.24 (t, J = 5.6 Hz, 4 H), 7.08–7.12 (m,
1 H), 7.59–7.64 (m, 2 H), 7.83 (dd, J = 8.1, 0.8 Hz, 1 H), 8.50
(dd, J = 4.8, 0.8 Hz, 1 H). 13C NMR (CDCl3): d = 24.4, 25.4,
52.0, 119.4, 122.3, 134.3, 136.5, 149.4, 156.3. MS (EI,
relative intensity): m/z = 189 (11) [M+]. HRMS (FAB–MS):
m/z calcd for C11H15N3: 189.1266; found: 189.1280.
(18) General Procedure for Allyl Cross-Coupling Reaction of
Disubstituted Allylic Acetates with 1-Naphthalene-
boronic Acid (Table 3): To a mixture of acetate (0.5 mmol),
Cs2CO3 (423.6 mg, 1.3 mmol), Pd(OAc)2 (5.61 mg, 0.025
Synlett 2008, No. 17, 2711–2715 © Thieme Stuttgart · New York

LETTER
mmol), and ligand 2a (5.08 mg, 0.025 mmol) in MeCN (2
Pd-Catalyzed Allyl Cross-Coupling Reaction
2715
under reduced pressure. The residue was purified by silica
gel chromatography. Compounds 3m and 3n were known
and identified by 1H NMR, 13C NMR, and MS.
(19) Keinan, E.; Kumar, S.; Dangur, V.; Vaya, J. J. Am. Chem.
Soc. 1994, 116, 11151.
mL) was added 1-naphthaleneboronic acid (103.2 mg, 0.6
mmol) at r.t. under an atmosphere of argon. After 24 h, the
mixture was diluted with EtOAc and H2O. The organic layer
was washed with brine, dried over MgSO4, and concentrated
Synlett 2008, No. 17, 2711–2715 © Thieme Stuttgart · New York

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