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9375
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6. Wada, M.; Ohki, H.; Akiba, K. Y. Bull. Chem. Soc.
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7. Zhou, J. Y.; Jia, Y.; Sun, G. F.; Wu, S. H. Synth.
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8. Li, C. J.; Meng, Y.; Yi, X. H.; Ma, J. H.; Chan, T. H.
J. Org. Chem. 1998, 63, 7498.
9. Zhang, W. C.; Li, C. J. J. Org. Chem. 1999, 64, 3230.
10. (a) Marton, D.; Stivanello, D.; Tagliavini, G. J. Org.
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Scheme 3.
11. (a) Mukaiyama, T.; Harada, T. Chem. Lett. 1981, 1527;
(b) Wu, S. H.; Huang, B. Z.; Gao, X. Synth. Commun.
1990, 20, 1279; (c) Wu, S. H.; Huang, B. Z.; Zhu, T.
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1999, 64, 4452; (e) Zhou, C.-L.; Zha, Z.-G.; Wang,
Z.-Y.; Wu, J.-H.; Zhang, J.-H. Chin. J. Chem. 2002, 20,
718.
positively charged copper cluster forms a cation-p com-
plex with allyl halide on the surface of copper metal
activating the allyl halide. Third, the activated allyl
halide reacts with SnCl2, producing an organotin com-
plex. Finally, the organotin complex allylates the car-
bonyl compound giving homoallylic alcohol.
12. The earlier allylation of carbonyl compounds in
aqueous media with SnCl2 employed allylic alcohols as
substrates. A palladium catalyst is necessary to activate
the reaction, see: (a) Masuyama, Y.; Takahara, T. P.;
Kurusu, Y. Tetrahedron Lett. 1989, 30, 3437; (b) Sati,
M.; Sinou, D. Tetrahedron Lett. 1991, 32, 2025.
13. Kundu, A.; Prabhakar, S.; Vairamani, M.; Roy, S.
Organometallics 1997, 16, 4796.
14. It should be mentioned that Cu(I) was also found to be
able to catalyze Barbier reaction in anhydrous organic
solvent, see: (a) Imai, T.; Niashida, S. J. Chem. Soc.,
Chem. Commun. 1994, 277; (b) Nishida, M.; Tozawa,
T.; Yamada, K.; Mukaiyama, T. Chem. Lett. 1996,
1125.
15. Roy et al. found that Cu(II)/Sn(II) can also mediate
allylation of disulfides and diselenides and carbonyl
propargylation presumably using the same mechanism
shown in Scheme 1, see: (a) Kundu, A.; Prabhakar, S.;
Vairamani, M.; Roy, S. Organometallics 1999, 18, 2782;
(b) Kundu, A.; Roy, S. Organometallics 2000, 19, 105;
(c) Sinha, P.; Kundu, A.; Roy, S.; Prabhakar, S.;
Vairamani, M.; Sankar, A. R.; Kunwar, A. C.
Organometallics 2001, 20, 157; (d) Sinha, P.; Roy, S.
Chem. Commun. 2001, 1798.
The key of the above mechanism is that the reaction
should occur on the surface of copper metal. Therefore,
enlarging the effective surface area should increase the
reaction efficiency. To test if this is true, we are now
trying to make nanometer copper materials20 and then
use them to catalyze allylation.
In conclusion, this study demonstrated a novel car-
bonyl allylation reaction mediated by SnCl2/Cu in
aqueous media. The reaction is very efficient and appli-
cable to various aliphatic and aromatic aldehydes and
ketones. Since copper metal is cheap, easy to handle
and fully recoverable after the reaction, we think that
this reaction could be valuable for laboratory and
industrial synthesis.
Acknowledgements
This work was supported by the MOST, CAS and
NSFC.
16. Copper metal was also found to be able to catalyze the
carbonyl allylation mediated by Zn and Mn metals, see:
(a) Delair, P.; Luche, J. L. J. Chem. Soc., Chem. Com-
mun. 1989, 398; (b) Li, C.-J.; Meng, Y.; Yi, X.-H.; Ma,
J.; Chan, T.-H. J. Org. Chem. 1997, 62, 8632. However,
the mechanism of copper catalysis in these reactions
remains unclear.
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1
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