Cobalt-Catalyzed Regio- and Stereoselective Allylzincation of 1-Phenyl-1-alkynes

Toshihiro Nishikawa; Hideki Yorimitsu; Koichiro Oshima

doi:10.1055/s-2004-829086

LETTER

Cobalt-Catalyzed Regio- and Stereoselective Allylzincation of 1-Phenyl-1-alkynes

Toshihiro Nishikawa, Hideki Yorimitsu, Koichiro Oshima*
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
Fax: +81(75)3832437; e-Mail: oshima@orgrxn.mbox.media.kyoto-u.ac.jp;

Abstract

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Abstract

The cobalt-catalyzed allylzincation reaction of 1-phenyl-1-alkynes proceeds with high regio- and stereoselectivity. The resultant alkenylzinc species undergo further functionalization upon treatment with electrophiles.

Key words

alkynes - allylzincation - cobalt

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References

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4 Allylzincation of 1-trimethylsilyl-1-alkyne with 2-(alkoxymethyl)-2-propenylzinc bromide was reported: van der Louw J. van der Baan JL. Bickelhaupt F. Klumpp GW. Tetrahedron Lett. 1987, 28: 2889

5

General Procedure: The allylzincation followed by trapping with allyl bromide is representative. A solution of allylzinc bromide (1.50 mL, 1.34 M THF solution, 2.0 mmol) was added to a THF solution of CoCl₂ (3.2 mg, 0.025 mmol) and 1f (161 mg, 0.500 mmol) at r.t. The mixture was stirred for 48 h at r.t. To the mixture were added sequentially allylbromide (0.22 mL, 2.5 mmol) and CuCN·2LiCl (0.1 mL, 1.0 M THF solution, 0.1 mmol). After stirring for another 3 h, the mixture was poured into 1 M HCl and extracted with Et₂O (3 × 20 mL). The combined organic layer was dried and concentrated. Purification by silica gel column chromatography afforded 7 (142 mg, 0.35 mmol) in 70% yield.