Generation of Aryl and Heteroaryl Magnesium Reagents in Toluene by Br/Mg or Cl/Mg Exchange

The alkylmagnesium alkoxide sBuMgOR center dot LiOR (R=2-ethylhexyl), which was prepared as a 1.5?m solution in toluene, undergoes very fast Br/Mg exchange with aryl and heteroaryl bromides, producing aryl and heteroaryl magnesium alkoxides (ArMgOR center dot LiOR) in toluene. These Grignard reagents react with a broad range of electrophiles, including aldehydes, ketones, allyl bromides, acyl chlorides, epoxides, and aziridines, in good yields. Remarkably, the related reagent sBu(2)Mg center dot 2 LiOR (R=2-ethylhexyl) undergoes Cl/Mg exchange with various electron-rich aryl chlorides in toluene, producing diorganomagnesium species of type Ar2Mg center dot 2 LiOR, which react well with aldehydes and allyl bromides.