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3. (a) Blaser, H.-U.; Spencer, A. J. Organomet. Chem. 1982,
233, 267–274; (b) Spencer, A. J. Organomet. Chem. 1982,
240, 209–216; (c) Spencer, A. J. Organomet. Chem. 1983, 247,
117–122; (d) Spencer, A. J. Organomet. Chem. 1984, 265,
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4. (a) Miura, M.; Hashimoto, H.; Itoh, K.; Nomura, M.
Tetrahedron Lett. 1989, 30, 975–976; (b) Miura, M.;
Hashimoto, H.; Itoh, K.; Nomura, M. J. Chem. Soc.,
Perkin Trans. 1 1990, 2207–2211.
5. (a) Sugihara, T.; Satoh, T.; Miura, M.; Nomura, M. Angew.
Chem., Int. Ed. 2003, 42, 4672–4674; (b) Sugihara, T.;
Satoh, T.; Miura, M.; Nomura, M. Adv. Synth. Catal. 2004,
346, 1765–1772.
6. The relevant Pd-catalyzed decarbonylative MH reactions
with other arylating reagents under base-free conditions.
With anhydrides: (a) Stephan, M. S.; Teunissen, A. J. J. M.;
Verzijl, G. K. M.; de Vries, J. G. Angew. Chem., Int. Ed.
1998, 37, 662–664; With arylesters: (b) Gooßen, L. J.;
Paetzold, J. Angew. Chem., Int. Ed. 2002, 41, 1237–1241;
With isopropenylesters: (c) Gooßen, L. J.; Paetzodl, J.
Angew. Chem., Int. Ed. 2004, 43, 1095–1098.
The present reaction may proceed by the mechanism sim-
ilar to that proposed previously.3a,5b The first step in-
volves oxidative addition of an aroyl chloride toward
Pd(0) species generated in situ and the subsequent
decarbonylation of the resulting aroylpalladium species
affords an arylpalladium intermediate. Insertion of an al-
kene to the intermediate and b-hydrogen elimination give
the corresponding arylated alkene along with HPdCl.
The refluxing conditions using o-xylene is considered to
make the elimination of HCl from HPdCl to regenerate
Pd(0) facile.7 The major role of the added lipophilic
ammonium chloride in this reaction may be the stabiliza-
tion of the palladium species in the aromatic solvent.9
In summary, we have demonstrated that the MH type
arylation of alkenes such as styrene and acrylate ester
using aroyl chlorides can be effectively performed in
the presence of the palladium catalyst system,
PdCl2(PhCN)2/(PhCH2)Bu3NCl, without adding any
base. The simple conditions make the product isolation
procedure significantly simple. Thus, this protocol
appears to provide a practical, convenient route to
vinyl-substituted aromatic compounds.
7. One of the key catalytic steps, elimination of HCl from
chloro hydrido transition metal complexes [HMCl(ligand)n]
is affected by the identity of metal and ligand as well as
added base. The process without any base has been less
explored. Grushin, V. V. Acc. Chem. Res. 1993, 26, 279–
286.
References and notes
8. Typicalprocedure: A mixture of 1 (1 mmol), 2 (1.2 mmol),
PdCl2(PhCN)2
(0.01 mmol),
and
(PhCH2)Bu3NCl
1. (a) Heck, R. F. Palladium Reagents in Organic Syntheses;
Academic Press: New York, 1985; pp 276–290; (b) Cabri,
W.; Candiani, I. Acc. Chem. Res. 1995, 28, 2–7; (c)
Beletskaya, I. P.; Cheprakov, A. V. Chem. Rev. 2000, 100,
3009–3066; (d) Bra¨se, S.; de Meijere, A. In Metal-Catalyzed
Cross-Coupling Reactions, 2nd ed.; de Meijere, A., Diede-
rich, F., Eds.; Wiley-VCH: Weinheim, 2004; pp 217–315; (e)
Tsuji, J. Palladium Reagents and Catalysts, 2nd ed.; John
Wiley & Sons: Chichester, 2004; pp 105–176.
(0.04 mmol) in refluxing o-xylene (5 mL) was stirred under
N2 (1 atm). After 3 h, the mixture was cooled to room
temperature, Et2O (ca. 30 mL) was added, and a small
amount of insoluble material was removed by filtration
through filter paper. After evaporation of the solvents
under vacuum, a small portion of MeOH was added, and
the resulting mixture was filtered to give the corresponding
crystals of 3. All the products are known and were
compared with those authentic specimens.
2. Blaser, H.-U.; Indolese, A.; Naud, F.; Nettekoven, U.;
Schnyder, A. Adv. Synth. Catal. 2004, 346, 1583–1598.
9. Reetz, M. T.; Westermann, E. Angew. Chem., Int. Ed. 2000,
39, 165–168.