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Jose Barluenga et al.
FULL PAPERS
ratus at 10ꢀ3 Torr for 1–3 hours to eliminate the protodebori-
nation product.
Experimental Section
Specific experimental details and characterization data for
compounds 4 and 6 are available in the Supporting Informa-
tion.
General Remarks
All reactions were carried out under nitrogen atmosphere in an
RR98030 12 place Carousel Reaction StationTM from Radleys
Discovery Technologies, equipped with gas-tight threaded
caps with a valve, cooling reflux head system, and digital tem-
perature controller. Toluene, dioxane, pentane and hexanes
were continuously refluxed and freshly distilled from sodium/
benzophenone under nitrogen. Pd2(dba)3 was purchased
form Strem Chemical Co. and used without further purifica-
tion. All phosphine ligands used are commercially available
from Strem or Aldrich and were used without further purifica-
tion. K3PO4 and CsF were purchased from Aldrich Chemical
Co., stored in a flask purged with nitrogen and weighed in
the air. The boronic acids employed are commercially availa-
ble from Aldrich or Acros, and were used without further pu-
rification. The boronic acid 3b was prepared according to a lit-
erature procedure.[27] 1,1-Dichloroethylene and 1,2-dichloro-
ethylene are commercially available from Fluka and Acros, re-
spectively, and were used without further purification.
Acknowledgements
´
´
Financial support of this work byFundacion Ramon Areces and
DGI (Grant MCT-04-CTQ2004-08077-C02-01). P. M. wishes to
thank MEC of Spain for a predoctoral fellowship.
References and Notes
[1] For general reviews on Pd-catalyzed cross-coupling reac-
tions, see: a) E. Negishi, (Ed.), Handbook of Organopal-
ladium Chemistry for Organic Synthesis, Wiley-Inter-
science, New York, 2002, Vol. I, Part III, pp 215–1119;
b) A. de Meijere, F. Diederich, (Eds.), Metal-Catalyzed
Cross Coupling Reactions, VCH, Weinheim, 2004.
´
´
[2] a) J. Barluenga, F. Aznar, M. A. Fernandez, C. Valdes,
Chem. Commun. 2002, 2362–2363; b) J. Barluenga,
´
´
M. A. Fernandez, F. Aznar, C. Valdes, Chem. Eur. J.
General Procedure for the Cross-Coupling of Boronic
Acids 3 with 1,1-Dichloroethylene (1) or trans-1,2-
Dichloroethylene (2)
2004, 10, 494–507; c) J. Barluenga, F. Aznar, M. A. Fer-
nandez, C. Valdes, Chem. Commun. 2004, 1400–1401.
[3] J. Barluenga, F. Aznar, P. Moriel, C. Valdes, Adv. Synth.
´
´
´
Catal. 2004, 346, 1697.
[4] For a review on the synthesis and application of hetero-
Method A: A carousel reaction tube under nitrogen atmos-
phere was charged with dicyclohexylphosphino-2’,4’,6’-triiso-
propylbiphenyl (XPhos) (0.02 mmol, 2 mol %), tris(dibenzyli-
deneacetone)dipalladium(0) (0.005 mmol, 1 mol %), potassi-
um phosphate (2 mmol), the boronic acid 3a, b (1 mmol) and
toluene (4 mL). After 1 minute, the dichloroethylene 1 or 2
(4 mmol) was added. The system was heated at 1008C with stir-
ring and reflux until the starting boronic acid had been com-
pletely consumed as judged by TLC analysis. The mixture
was allowed to cool to room temperature, taken up in dry pen-
tane or hexanes (15 mL), and filtered through Celite. The sol-
vents were evaporated under reduced pressure. The residue
was redissolved in dry hexanes (15 mL), filtered again through
Celite, concentrated under reduced pressure and dried under
high vacuum to afford a residue which consisted of the essen-
tially pure chlorodiene 4a, b or 5a, b.
´
substituted dienes, see: J. Barluenga, A. Suarez-Sobrino,
´
L. A. Lopez, Aldrichim. Acta 1999, 32, 4.
[5] a) E. Nagashima, K. Suzuki, M. i. Ishikawa, M. Sekiya,
Heterocycles, 1985, 23, 1873–1879; b) R. Baati, D. K.
Barma, U. M. Krishna, C. Mioskowski, J. R. Falck, Tetra-
hedron Lett. 2002, 43, 959–961; c) B. Crousse, M. Mlade-
nova, P. Ducept, M. Alami, G. Linstrumelle, Tetrahedron
1999, 55, 4353–4368 and references cited therein.
[6] For the synthesis of 2-halo-1,3-butadienes, see: a) J. Por-
´
net, Tetrahedron Lett. 1981, 22, 453; b) A. Horvat, J.-E.
Bäckvall J. Org. Chem. 2001, 66, 8120–8126; c) S. Ma,
G. Wang, Tetrahedron Lett. 2002, 43, 5723.
[7] For some recent reports of the synthesis of b-chlorostyr-
enes through the classical Hunsdiecker reaction, see:
a) D. Naskar, S. Chowdhury, S. Roy, Tetrahedron Lett.
1998, 39, 699; b) S. C. Roy, C. Guin, G. Maiti, Tetrahe-
dron Lett. 2001, 42, 9253; c) C. Kuang, H. Senboku, M.
Tokuda, Synlett 2000, 1439.
[8] For the synthesis of a-chlorostyrenes, see: T. J. Barton,
G. T. Burns, Organometallics 1982, 1, 1455.
[9] A. Minato, K. Suzuki, K. Tamao, J. Am. Chem. Soc. 1987,
109, 1257.
[10] a) C. Xu, E. Negishi, Tetrahedron Lett. 1999, 40, 431–
434; b) X. Zeng, M. Qian, Q. Hu, E. Negishi, Angew.
Chem. Int. Ed. 2004, 43, 2259–2263.
[11] a) W. R. Roush, K. J. Moriarty, B. B. Brown, Tetrahedron
Lett. 1990, 31, 6509–6512; b) L. S. M. Wong, L. A. Sharp,
N. M. C. Xavier, P. Turner, M. S. Sherburn, Org. Lett.
2002, 4, 1995.
Method B: This is the same as that of Method A, using CsF
(2 mmol) instead of K3PO4 as base and dioxane (4 mL) as sol-
vent.
Method C: A carousel reaction tube under nitrogen atmos-
phere was charged with 1,1’-bis(di-tert-butylphosphino)bi-
phenyl (JohnPhos) (0.02 mmol, 2 mol %), tris(dibenzylidene-
acetone)dipalladium(0) (0.005 mmol, 1 mol %), cesium fluo-
ride (2 mmol), the boronic acid 3c–k (1 mmol) and dioxane
(4 mL). After 1 minute, the dichloroethylene 1 or 2 (4 mmol)
was added. The system was heated at 708C with stirring and re-
flux until the starting boronic acid had been completely con-
sumed as judged by TLC analysis. The mixture was allowed
to cool to room temperature, taken up in dry pentane, hexanes
or dichloromethane (15 mL), and filtered through Celite. The
solvents were evaporated under reduced pressure and the res-
idue was purified by flash chromatography. In some cases, the
crude residue was heated neat at 42–658C in a kugelrçhr appa-
352
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Adv. Synth. Catal. 2006, 348, 347 – 353