Recent Advance in Heterocyclic Organozinc and

Organomanganese Compounds; Direct Synthetic Routes and

Application in Organic Synthesis

Seung-Hoi Kim

1 and Reuben D. Rieke 2,*

The above review appeared in Molecule (8 November 2010), which you should be able to access via the Directory of Open Access Journals (if not, I can send you a PDF copy). The reaction scheme and table on the fifth page should help resolve your difficultty. 3- haloaromatic heterocycles are not the most co-operative for Grignard formation, but the are alternative ways of substituting the bromine atiom on your thiophene ring with the group you do want. Best of luck.

Paul

Riecke magnesium does the trick, although in modest yield:

http://pubs.acs.org/doi/abs/10.1021/jo970778b

Grignard chemistry doesn't work with 3-bromothiophene. Use lithiation instead.

Possible but not recommended.

Grignard reaction might not work, best would be Lithium halogen exchange reaction.

Try n-BuLi and make sure you have anhydrous solvent like ether.

Good luck

Moshfiqur

Paul,

Thanks for the Molecules review. BTW, the thiophene halides featured there serve as electrophiles, and not precursors to a nucleophile.

Kumar,

Try Ultrasonic activation for the preparation of your reagent ! It may work well and let us know.  Of course, as mentioned organo-lithium is a good idea.

Good luck 

You may use Mg in the presence of LiCl.

http://dx.doi.org/10.1080/00397911.2011.606391