type of olefins in the Heck reaction. In this regard, very
recently, White and co-workers9a have reported the regiose-
lective Heck-type reaction of alkyl-substituted olefins bearing
auxiliary coordinating groups with aryl boronic acids as
arylating reagents, and Jiao and co-workers9b have described
highly selective Heck coupling reaction of allylic esters with
aryl iodides. Despite these advances in the Heck reaction of
alkyl-substituted olefins, in view of its applications in organic
synthesis, efficient Heck reactions of a wide scope of alkyl-
substituted olefins with various arylating reagents, particu-
larly those that are easily available and inexpensive, remains
highly demanded.
Table 1. Selected Screening Results for the Palladium-Catalyzed
Decarboxylative Heck Coupling of 2,4-Dimethoxybenzoic Acid
with 1-Octenea
isolated
oxidant
entry (equiv)
additive
(eqiuv)
yieldb
(%)
solvent (v:v)
Transition-metal-catalyzed decarboxylative cross-coupling
reactions of arenecarboxylic acids or arenecarboxylates have
emerged over the past few years.10-13 This approach is
particularly attractive due to the high availability and the
low price of arenecarboxylic acids. Myers,11 in his pioneering
work, disclosed an efficient method for palladium-catalyzed
decarboxylative Heck-type reaction of arenecarboxylic acids
with styrene and R,ꢀ-unsaturated carbonyls. This work
represents a milestone in the development of palladium-
catalyzed decarboxylative cross-coupling reactions.14 Nev-
ertheless, significant room remains for improvement in view
of high loadings of silver and palladium that were required
in this process as well as the limiting olefin scope of this
process. Herein, we report an efficient palladium-catalyzed
decarboxylative Heck-type cross-coupling reaction of an
array of arenecarboxylic acids with a broad spectrum of
olefins including unactivated alkyl-substituted terminal ole-
fins, wherein an inexpensive 1,4-benzoquinone (BQ) was
used as an oxidant.
1
2
3
4
BQ (1.2)
DMSO/DMF (1:20) 10
DMSO/DMF (1:20) 26
DMSO/DMF (1:20) 38
DMSO/DMF (1:20) 50
DMSO/DMF (1:20) 70
BQ (1.2) EtCO2H (4)
BQ (1.2) tBuCO2H (4)
BQ (1.2) 1-AdCO2Hc (4)
5d purified 1-AdCO2H (4)
BQ (1.2)
6
purified 1-AdCO2H (4)
BQ (1.2)
DMSO/DMF/
dioxane (1:15:5)
DMF
79
7
purified 1-AdCO2H (4)
BQ (1.2) 3-nitropyridine
(0.2)
purified 1-AdCO2H (4)
BQ (1.2) THTOe (4.4)
BQ (1.2) MeCO2H (4)
41
8
9
DMF
39
DMSO/DMF (1:20) trace
DMSO/DMF (1:20) trace
10 BQ (1.2) CF3CO2H (4)
11 BQ (1.2) p-Me-C6H4SO3H (4) DMSO/DMF (1:20) trace
12f purified 1-AdCO2H (4)
DMSO/DMF (1:20)
0
DDQg
13h O2
31
a Reaction conditions: 1a (0.25 mmol), 1-octene (0.50 mmol),
Pd(O2CCF3)2 (0.025 mmol), 1,4-benzoquinone ) BQ (0.30 mmol), car-
boxylic acid (1.0 mmol), solvent (2.1 mL). b Average of two runs.
c 1-Adamatanecarboxylic acid ) 1-AdCO2H. d BQ was purified by
sublimation. e Tetrahydrothiophene 1-oxide ) THTO. f Rection was run in
the absence of Pd(O2CCF3)2. g 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone
) DDQ. h Reaction was run for 13 h.
The model reaction of 2,4-dimethoxybenzoic acid with 2.0
equiv of 1-octene was examined with a variety of palladium
(8) (a) Bra¨se, S.; Schroen, M. Angew. Chem., Int. Ed. 1999, 38, 1071.
(b) Brunner, H.; de Courey, N. L. C.; Geneˆt, J.-P. Tetrahedron Lett. 1999,
40, 4815. (c) Mabic, S.; Vaysse, L.; Benezra, C.; Lepoittevin, J.-P. Synthesis
1999, 7, 1127. For the Heck reaction of allylic alcohols: (d) Larock, R. C.;
Yum, E. K.; Yang, H. Tetrahedron 1994, 50, 305. (e) Chalk, A. J.;
Magennis, S. A. J. Org. Chem. 1976, 41, 1206. For intramolecular
olefination of C-H bond with alkyl-substituted olefins, see: (f) ref 6e. (g)
Liu, C.; Han, X.; Wang, X.; Widenhoefer, R. A. J. Am. Chem. Soc. 2004,
126, 3700. For the decarboxylative Heck reaction of an aromatic carboxlic
anhydride with an alkyl-substituted olefin, see: (h) Stephan, M. S.;
Teunissen, A. J. J. M.; Verzijl, G. K. M.; de Vires, J. G. Angew. Chem.,
Int. Ed. 1998, 37, 662.
sources, solvents, additives, and oxidants (Table 1). Initially,
using 1.2 equiv of BQ as the oxidant and 10 mol % of
Pd(O2CCF3)2 as the catalyst provided the desired products
in about 10% yield (entry 1). Because the acidic condition
can enhance the ability of BQ to oxidize Pd(0) to Pd(II)15
and prevent the possible catalyst poisoning caused by the
coordinating species,11b the introduction of carboxylic acid
to the reaction system brought about a beneficial effect
(entries 2-4). Screening acids and their loadings established
that 4 equivalents of bulky 1-adamantanecarboxylic acid
maximized the beneficial effect from acids (entry 4).
However, strong acids such as trifluoroacetic acid and
p-toluenesulfonic acid and even acetic acid abolished this
reaction (entries 9-11). The use of BQ purified by sublima-
tion significantly improved the reaction with 70% yield
obtained (entry 5). Further optimization showed that the
reaction in DMSO/DMF/dioxane (1:15:5) furnished the best
yield (entry 6). Interestingly, substituting DMSO for 0.2
equiv of 3-nitropyridine and 0.1 mL of tetrahydrothiophene-
1-oxide provided products in 41% and 39% yields (entries
(9) (a) Delcamp, J. H.; Brucks, A. P.; White, M. C. J. Am. Chem. Soc.
2008, 130, 11270. (b) Pan, D.; Chen, A; Su, Y.; Zhou, W.; Li, S.; Jia, W.;
Xiao, J.; Liu, Q.; Zhang, L.; Jiao, N. Angew. Chem., Int. Ed. 2008, 47,
4729.
(10) (a) Goossen, L. J.; deng, G.; Levy, L. M. Science 2006, 313, 662.
(b) Goossen, L. J.; Rodr´ıguez, N.; Melzer, B.; Linder, C.; Deng, G.; Levy,
L. M. J. Am. Chem. Soc. 2007, 129, 4824. (c) Goossen, L. J.; Melzer, B.
J. Org. Chem. 2007, 72, 7473. (d) Goossen, L. J.; Zimmermann, B.;
Knauber, T. Angew. Chem., Int. Ed. 2008, 47, 7103. (e) Duan, Z.; Ranjit,
S.; Zhang, P.; Liu, X. Chem.sEur. J. 2009, 15, 3666.
(11) (a) Myers, A. G.; Tanaka, D.; Mannion, M. R. J. Am. Chem. Soc.
2002, 124, 11250. (b) Tanaka, D.; Romeril, S. P.; Myers, A. G. J. Am.
Chem. Soc. 2005, 127, 10323. (c) Tanaka, D.; Myers, A. G. Org. Lett. 2004,
6, 433.
(12) (a) Forgione, P.; Brochu, M.-C.; St-Onge, M.; Thesen, K. H.; Bailey,
M. D.; Bilodeau, F. J. Am. Chem. Soc. 2006, 128, 11350. (b) Maehara, A.;
Tsurugi, H.; Satoh, T.; Miura, M. Org. Lett. 2008, 10, 1159. (c) Becht,
J.-M.; Catala, C.; Drian, C. L.; Wagner, A. Org. Lett. 2007, 9, 1781.
(13) For examples of the intramolecular rearrangement reactions via
decarboxylation of esters, see: (a) Waetzig, S. R.; Tunge, J. A. J. Am. Chem.
Soc. 2007, 129, 14860. (b) Rayabarapu, D. K.; Tunge, J. A. J. Am. Chem.
Soc. 2005, 127, 13510. (c) Goossen, L. J.; Paezold, J. Angew. Chem., Int.
Ed. 2004, 43, 1095.
(14) Baudoin, O. Angew. Chem., Int. Ed. 2007, 46, 1373.
(15) Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877.
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Org. Lett., Vol. 11, No. 11, 2009