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

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.

alkynes - allylzincation - cobalt

References

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<A NAME="RU07904ST-5">5</A>

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.