Highly Regioselective Preparation of Heteroaryl-Magnesium Reagents by Using a Br/Mg Exchange

Disubstituted thienyl-, furyl- and pyridylmagnesium derivatives are regioselectively prepared from a Br/Mg exchange of the corresponding dibromo compounds by using either iPrMgCl center dot LiCl or hindered arylmagnesium reagents, such as isitylmagnesium bromide center dot lithium chloride (isityl=2,4,6-triisopropyl-phenyl) complexed with a diamine ligand, in difficult cases. The selective functionalisations of these heterocyclic scaffolds by using Negishi cross-coupling reactions, acylations or addition to aldehydes were readily achieved.