Microwave-enhanced palladium-catalyzed cross-coupling reactions of potassium vinyltrifluoroborates and allyl acetates: A new route to 1,4-pentadienes

Article abstract of DOI:10.1021/ol051955v

(Chemical Equation Presented) A novel and straightforward microwave synthesis of 1,4-pentadienes has been developed involving the cross-coupling of potassium vinyltrifluoroborates and allyl acetates in the presence of a palladium catalyst.

Full text of DOI:10.1021/ol051955v

ORGANIC
LETTERS
2006
Vol. 8, No. 1
11-13
Microwave-Enhanced
Palladium-Catalyzed Cross-Coupling
Reactions of Potassium
Vinyltrifluoroborates and Allyl Acetates:
A New Route to 1,4-Pentadienes
George W. Kabalka*,† and Mohammad Al-Masum‡
Departments of Chemistry and Radiology, The UniVersity of Tennessee,
KnoxVille, Tennessee 37996-1600, and Department of Chemistry, Tennessee State
UniVersity, NashVille, Tennessee 37209
kabalka@utk.edu
Received August 12, 2005
ABSTRACT
A novel and straightforward microwave synthesis of 1,4-pentadienes has been developed involving the cross-coupling of potassium
vinyltrifluoroborates and allyl acetates in the presence of a palladium catalyst.
Reactions involving the coupling of potassium organotri-
fluoroborates with organic electrophiles have received a good
deal of attention in organic chemistry as a result of their
efficiency in creating carbon-carbon bonds.1 Trifluoro-
borates are readily prepared and remarkably stable, yet they
are quite reactive. To our knowledge, of the reported
couplings involving potassium vinyltrifluoroborate and elec-
trophiles, none include straightforward allylation reactions.2
Although examples describing the palladium-catalyzed
coupling of arylboronic acids with allyl halides3 and allyl
acetates4 have been reported, reactions producing 1,4-dienes
have not been explored.5 The 1,4-diene framework constitutes
(2) (a) Kabalka, G. W.; Dong, G.; Venkataiah, B. Org. Lett. 2003, 5,
3803. (b) Molander, G. A.; Bernardi, C. R. J. Org. Chem. 2002, 67, 8424.
(c) Darses, S.; Michaud, G.; Genet, J.-P. Eur. J. Org. Chem. 1999, 1875.
(3) (a) Singh, R.; Viciu, M. S.; Kramareva, N.; Navarro, O.; Nolan, S.
P. Org. Lett. 2005, 7, 1829. (b) Alonso, D. A.; Najera, C.; Pacheco, M. C.
J. Org. Chem. 2002, 67, 5588. (c) Varma, R. S.; Naicker, K. P. Green
Chem. 1999, 2, 247. (d) Moreno-Manas, M.; Pajuelo, F.; Pleixats, R. J.
Org. Chem. 1995, 60, 2396. (e) Miyaura, N.; Suginome, H.; Suzuki, A.
Tetrahedron Lett. 1984, 25, 761.
(4) (a) Ortar, G. Tetrahedron Lett. 2003, 44, 4311. (b) Bouyssi, D.;
Gerusz, V.; Balme, G. Eur. J. Org. Chem. 2002, 2445. (c) Legros, J.-Y.;
Fiaud, J.-C. Tetrahedron Lett. 1990, 31, 7453. (d) Miyaura, N.; Yamada,
K.; Suginome, H.; Suzuki, A. J. Am. Chem. Soc. 1985, 107, 972. (e)
Miyaura, N.; Tanabe, Y.; Suginome, H.; Suzuki, A. J. Organomet. Chem.
1982, 233, C13,
* To whom all corresspondence should be addressed. Ph: (865)974-
3260. Fax: (865)974-2997.
† The University of Tennessee.
‡ Tennessee State University.
(1) (a) Molander, G. A.; Felix, L. A. J. Org. Chem. 2005, 70, 3950. (b)
De, S.; Welker, M. E. Org. Lett. 2005, 7, 2481. (c) Duursma, A.; Boiteau,
J.-G.; Lefort, L.; Boogers, J. A. F.; DeVries, A. H. M.; DeVries, J. G.;
Minnaard, A. J.; Feringa, B. L. J. Org. Chem. 2004, 69, 8045. (d) Fang,
G.-H.; Yan, Z.-J.; Deng, M.-Z. Org. Lett. 2004, 6, 357. (e) Pucheault, M.;
Darses, S.; Genet, J.-P. J. Am. Chem. Soc. 2004, 126, 15356. (f) Pucheault,
M.; Darses, S.; Genet, J.-P. Tetrahedron Lett. 2002, 43, 6155.
(5) In one case, a reaction between 1-hexenyl-1,3,2-benzodioxaborole
and cinnamyl acetate was carried out in benzene at refluxing temperatures
for 4 h using 5 mol % Pd(PPh3)4 and a 10% excess of 1-hexenyl-1,3,2-
benzodioxaborole. A 12% yield of the corresponding 1-phenyl-1,4-nonadiene
was reported: Miyaura, N.; Yamada, K.; Suginome, H.; Suzuki, A. J. Am.
Chem. Soc. 1985, 107, 972. An additional example was recently reported:
Kayaki, Y.; Koda, T.; Ikariya, T. Eur. J. Org. Chem. 2004, 4989.
10.1021/ol051955v CCC: $33.50
© 2006 American Chemical Society
Published on Web 12/03/2005

Table 1. Pd-Catalyzed Allylation of Potassium Vinyltrifluoroborates with Allyl Acetatesa
a Reaction conditions: 1 (0.5 mmol), allylating agent 2 (0.5 mmol), i-Pr2NEt (1.5 mmol), PdCl2(dppf)-CH2Cl2 (0.001 mmol), 2-propanol/water (2:1), 80
°C, MW, 10 min. b Isolated yields.
an important structural assembly in many molecules of
biological importance6 in addition to its application in organic
synthesis.7 Homoconjugated dienes can also be transformed
into conjugated 1,3-dienes in the presence of sulfur dioxide
via an ene reaction.8 We wish to report a rapid palladium-
catalyzed cross-coupling of allyl acetates with a variety of
potassium vinyltrifluoroborates that furnishes 1,4-pentadienes
under microwave irradiation (Scheme 1).
(6) (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.
(7) (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. (c) Klaps, E.; Schmid, W. J. Org. Chem. 1999,
64, 4, 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.
Scheme 1. Synthesis of 1,4-Dienes
12
Org. Lett., Vol. 8, No. 1, 2006

Microwave activation has been utilized with some notable
success in a variety of Suzuki-Miyaura coupling reactions.9
This study was initiated by allowing potassium trans-2-[4-
(trifluoromethyl)phenyl]vinyltrifluoroborate to react with
allyl acetate in the presence or absence of a palladium
catalyst. No carbon-carbon bond formation occurred in the
absence of palladium. PdCl2(dppf)‚CH2Cl2, Pd2dba3‚CHCl3/
dppf, Pd2dba3/(o-tolyl)3, Pd(OAc)2/dppf, and Pd(OAc)2 were
evaluated as potential catalysts. Diisopropylethylamine,
cesium carbonate, potassium carbonate, and triethylamine
were examined as bases. Of the conditions studied, the best
results were obtained using 2 mol % of PdCl2(dppf)‚CH2-
Cl2 in the presence of 3.0 equiv of diisopropylethylamine
(Hu¨nig’s base) in 2-propanol/water (2:1) at 80 °C under
microwave irradiation. The required organotrifluoroborates
were readily accessible from the corresponding organobo-
ronic acids by addition of potassium hydrogen fluoride.10
Table 1 contains the results of this initial study. Allyl acetate
and cinnamyl acetate were allowed to react with various
substituted potassium arylvinyltrifluoroborates to produce a
variety of 1,4-dienes in good to excellent yields. Geranyl
acetate also reacted as an allylating agent.
Aliphatic potassium vinyltrifluoroborates such as potas-
sium trans-1-nonenyltrifluoroborate can also be utilized. The
coupling reactions are stereoselective in that the E isomers
are the only observed products and also regioselective,
although traces of the isomeric products are observed in the
products derived from cinnamyl acetate (presumably gener-
ated via an n3-allylpalladium intermediate). The regioisomer
is more prevalent in the products generated from geranyl
acetate. The presence of the isomer is revealed by resonances
near 112 ppm in the carbon-13 spectra due to the terminal
methylene carbon. In conclusion, the new method provides
a general and efficient synthetic method for preparing 1,4-
pentadienes.11
Acknowledgment. We wish to thank the Department of
Energy and the Robert H. Cole Foundation for support of
this research. We also thank Mr. Eric Dadush and Dr. Arjun
Mereddy for technical assistance.
Supporting Information Available: Experimental pro-
cedure for the syntheses; copies of the 13C NMR, 1H NMR,
and 19F NMR spectra; and combustion analyses for all new
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
(8) (a) Roulet, J.-M.; Deguin, B.; Vogel, P. J. Am. Chem. Soc. 1994,
116, 3639. (b) Rogic, M.; Masilamani, D. J. Am. Chem. Soc. 1977, 99,
5219.
OL051955V
(9) (a) Arvela, R. K.; Leadbeater, N. E.; Collins, M. J., Jr. Tetrahedron
2005, 61, 9349. (b) Kabalka, G. W.; Al-Masum, M. Tetrahedron Lett. 2005,
46, 6329. (c) Arvela, R. K.; Leadbeater, N. E. Org. Lett. 2005, 7, 2101. (d)
Miao, G.; Ye, P.; Yu, L.; Baldino, C. M. J. Org. Chem. 2005, 70, 2332. (e)
Bedford, R. B.; Butts, C. P.; Hurst, T. E.; Lidstroem, P. AdV. Synth. Catal.
2004, 346, 1627. (f) Melucci, M.; Barbarella, G.; Zambianchi, M.; Di Pietro,
P.; Bongini, A. J. Org. Chem. 2004, 69, 4821. (g) Zhang, W.; Chen, C.
H-T.; Lu, Y.; Nagashima, T. Org. Lett. 2004, 6, 1473. (h) Bai, L.; Wang,
J.-X.; Zhang, Y. Green Chem. 2003, 5, 615. (i) Larhed, M.; Lindeberg, G.;
Hallberg, A. Tetrahedron Lett. 1996, 37, 8219.
(11) General Procedure for the Synthesis of 1,4-Pentadienes. A dry
Pyrex tube fitted with an airtight rubber cap was charged with potassium
vinyltrifluoroborate (0.50 mmol) and PdCl2(dppf)‚CH2Cl2 (0.01 mmol, 9.0
mg) and was flushed with argon. The allylating agent (0.50 mmol) and
Hu¨nig’s base (1.5 mmol, 265 µL) were then added, followed by argon-
purged 2-propanol/water (2:1, 5.0 mL). The resulting mixture was placed
in a CEM microwave unit and allowed to react at 80 °C for 10 min. The
reaction mixture was then transferred to a separatory funnel and diluted
with ethyl ether (2 × 15 mL) and water (15 mL). After extraction, the
organic phase was separated and dried over anhydrous sodium sulfate. The
ether solution was filtered and concentrated, and the product was subjected
to silica gel chromatography using hexane/ethyl acetate (100/1) as eluent.
(10) Vedejs, E.; Chapman, R. W.; Fields, S. C.; Lin, S.; Schrimpf, M.
R. J. Org. Chem. 1995, 60, 3020.
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