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Synfacts 2009(4): 0425-0425  
DOI: 10.1055/s-0028-1087824
Metal-Mediated Synthesis
© Georg Thieme Verlag Stuttgart ˙ New York

Efficient Cobalt-Catalyzed Coupling of Aryl Grignard Reagents with Alkyl Bromides

Contributor(s):Paul Knochel, Andrei Gavryushin
G. Cahiez*, C. Chaboche, C. Duplais, A. Moyeux
CNRS - Université de Paris 13, Bobigny, France
A New Efficient Catalytic System for the Chemoselective Cobalt-Catalyzed Cross-Coupling of Aryl Grignard Reagents with Primary and Secondary Alkyl Bromides
Org. Lett.  2009,  11:  277-280  
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Publication History

Publication Date:
23 March 2009 (online)

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Key words

alkyl-aryl cross-coupling - cobalt catalysis - Grignard reagents

Significance

An efficient cobalt-catalyzed cross-coupling reaction of aryl Grignard reagents with primary and secondary alkyl bromides is reported. The reaction proceeds rapidly under very mild conditions and tolerates many functional groups. A readily available cobalt catalyst is used in the process, which is in general more efficient and versatile than the similar iron-catalyzed sp²-sp³ cross-coupling reactions.

Comment

Due to the relatively fast reaction (0 ˚C, 40 min) functional groups like ester, amide and ketone are well tolerated. Alkyl iodides give similar yields as bromides, while chlorides and tosylates do not react. Hindered mesitylmagnesium bromide gives low yield of the product. Interestingly, the cobalt source is also important in this reaction, and CoCl2 is less efficient in the presence of TMEDA than Co(acac)3.

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